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Deforesting the Riverscape: The Effects of Wood on Fish Diversity in a Venezuelan Piedmont Stream
Abstract
While deforestation of tropical ecosystems has been shown to have significant impacts on terrestrial habitats, its effects on aquatic habitats are poorly studied. Deforestation dramatically reduces the input of woody debris to streams, and given the importance of large woody debris to fish communities in temperate streams, this might be one mechanism by which logging could affect aquatic ecosystems in the tropics. To examine the effects of large woody debris on the diverse fish assemblage of a tropical stream, we surveyed pools with and without wood at Rio Las Marias, Venezuela. Pools containing wood contained greater numbers of individuals and more species of fish than pools without wood, and the two types of pools differed in their composition. To test whether these results were due to the presence of woody debris, we conducted an experimental wood addition. Pools to which wood was added showed marked increases in both fish abundance and species richness relative to wood-free pools, and the composition of the fish assemblage in experimental pools approached that of pools with naturally occurring woody debris. These results demonstrate that large woody debris plays a major role in structuring fish communities in tropical streams. As a consequence, logging practices that reduce the input of woody debris to tropical streams or directly remove wood from streams could have serious impacts on aquatic habitats, affecting both the diverse fish communities and local economies dependent on stream fisheries.
... En Venezuela son pocos los trabajos desarrollados, destacando los de Flecker (1992), Cressa y Barrios (2002), Maldonado et al. (2002), Capelo et al. (2004), Wright y Flecker (2004), Pereira et al. (2006), Rincón (2006), Guerrero (2007) y Alarcón (2008), entre otros. Solo algunos de estos han evaluado la comunidad de macroinvertebrados a nivel de la cordillera andina o zonas con características similares, por lo que resulta necesario desarrollar un mayor número de investigaciones con la finalidad de completar la información existente. ...
... Al comparar las siete localidades evaluadas en el Área Focal 1, la quebrada La Bellaca presentó la mayor riqueza de grupos (39), seguida de la quebrada La Laja (29) (Tabla 3.1), lo cual podría ser atribuido a la mayor heterogeneidad y complejidad de hábitats presentes en estas localidades. Numerosos autores (Dahl y Greenberg 1998, Vinson y Hawkins 1998, Baptista et al. 2001a, 2001bBueno et al. 2003, Wright y Flecker 2004, han evidenciado esta relación y mencionan que en este tipo de ambientes una mayor entrada de material alóctono (hojas, ramas, troncos) y productividad del perifiton y una elevada velocidad de corriente, genera una mayor disposición de sustrato que puede ser colonizado por la fauna bentónica, proporcionando una mayor disponibilidad de alimento y refugio para estos organismos. Entre los hábitats mencionados, las zonas de acumulación de hojarasca han sido reportadas como sitios de alta riqueza de insectos ya que durante la estación seca son menos afectadas por el flujo hidráulico, permitiendo un mayor período de colonización y procesamiento de la materia orgánica por los macroinvertebrados (Baptista et al. 2001a). ...
... Probablemente la menor riqueza observada se deba a que esta zona presenta un mayor grado de intervención (deforestación y actividad agrícola). Wright y Flecker (2004) indican que la deforestación es una actividad común en ríos de piedemonte andino y puede traer como consecuencia una disminución en la diversidad de los ecosistemas acuáticos, atribuido principalmente a una reducción en la entrada de material alóctono al cuerpo de agua. Adicionalmente, Sponseller et al. (2001) señalan que este tipo de actividades están correlacionadas negativamente con la heterogeneidad del sustrato debido a un incremento en la entrada de sedimento fino al cuerpo de agua, extendiéndose este efecto aguas abajo del área perturbada. ...
... Riparian clearing/canopy opening can cause decreases in mid-channel shade (Leal et al., 2016), higher periphyton biomass (Bojsen & Jacobsen, 2003;Lobón-cerviá, Mazzoni, & Rezende, 2016;Feijó-Lima et al., 2018), higher water temperature (Benstead et al., 2003;Fugère, Kasangaki, & Chapman, 2016;Leal et al., 2016), lower levels of benthic organic matter or leaf litter (Bojsen & Barriga, 2002;Bojsen & Jacobsen, 2003;Benstead et al., 2003;Brejão et al., 2018;Montag et al., 2019), increased aquatic vegetation , and declines in terrestrial insect inputs (Chan, Zhang, & Dudgeon, 2008;da Silva Gonçalves, de Souza Braga, & Casatti, 2018; as found in Nakano, Miyasaka, & Kuhara, 1999). Loss of instream large woody debris results from deforestation (Heartsill-Scalley & Aide, 2003;De Paula, Gerhard, Wenger, Ferreira, Vettorazzi, Ferraz, 2011;Leal et al., 2016), and has been related to shifts in the biotic community (Wright & Flecker, 2004;Valente-Neto, Koroiva, Fonseca-Gessner, & de Oliveira Roque, 2015;Leitão et al., 2017;Brejão et al., 2018;Montag et al., 2019). ...
... Studies have shown community changes are related to shifts in instream habitat. Wright and Flecker (2004) found higher abundance of most species, and especially rare species, in streams where woody debris was not removed (loss of woody debris is coincident with deforestation). Bojsen and Barriga (2002) correlated shifts in the fish community to increased sunlight and lower instream leaf abundance from loss of canopy cover. ...
... Both autochthonous and allochthonous sources of plant material were lowest in longer deforested streams (Table 1) and were significantly explained by the deforestation history index (Table 2). Lower amounts of large wood and small woody and leafy debris in streams is a common impact of deforestation in a catchment (Bojsen & Barriga, 2002;Benstead et al., 2003;Bojsen & Jacobsen, 2003;Wright & Flecker, 2004;De Paula et al., 2011;Leal et al., 2016;Leitão et al., 2017;Brejão et al., 2018;Montag et al., 2019), and is related to reduced riparian vegetation. It could also be related to decreased flow consistency, as deforestation could be resulting in increasingly flashy streams (Chaves et al., 2008;Recha et al., 2012;Peña-Arancibia, Bruijnzeel, Mulligan, & van Dijk, 2019) with less stabilizing large wood structure which tends to flush out leaf litter and smaller debris (Bilby & Likens, 1980). ...
In southeast Nicaragua, recent waves of illegal deforestation for cattle pasture are
damaging the Indio-Maíz Biological Reserve (IMBR) and Rama-Kriol territory (RKT), with
negative consequences to aquatic ecosystems and the people who rely on services they provide.
Deforestation and subsequent land use are causing shifts in stream community structure that are
mediated by changes in stream habitat. This study integrated temporally explicit land use
information with stream habitat, macroinvertebrate, freshwater shrimp, and fish community data
to assess impacts of deforestation on 15 headwater streams in southeast Nicaragua’s poorly
studied protected rainforests. The new calculation, deforestation history index (DFI), a product
of deforestation amount and time since deforestation for the catchment draining to each stream
reach, was the best linear predictor of most taxa responses—better than other habitat metrics and
raw forest cover at multiple scales. Stream reaches that were deforested for a longer time and to a
larger extent—thus having higher values for the DFI—had less large wood, organic debris,
macroalgae, and macrophytes; more stream bank erosion and sedimentation; degraded riparia;
lower diversity and abundance of macroinvertebrates, shrimp, and fish; higher invertebrate
evenness; and distinct changes in invertebrate community composition. All deforested reaches
also had smaller sized game fish. New registers of fish species and insect genera were recorded
for Nicaragua. As this is the first aquatic study in these watersheds of the IMBR and RKT, this
region should be a high priority for further research and conservation investment before it is lost.
... The moderate levels of explanation may be due to the dynamic nature of small streams in the Amazon, which are prone to effects of other variables not measured in our study associated with disturbance regimes, reproduction/recruitment, dispersal, metacommunity dynamics, and others. The positive association of medium to very large LWD inside the channel with aquatic species richness and composition reflects the dependence of aquatic species on submerged structures to provide cover from predators, nesting sites, and food resources (Wright & Flecker, 2004;Valente-Neto et al., 2015;Pilotto et al., 2016). LWD contributes not only to the quantity but also the quality of microhabitats available in streams (Braccia & Batzer, 2001), providing structural complexity that influences the spatial distribution of several taxa (Smith et al., 1993). ...
... LWD contributes not only to the quantity but also the quality of microhabitats available in streams (Braccia & Batzer, 2001), providing structural complexity that influences the spatial distribution of several taxa (Smith et al., 1993). Habitat structural complexity facilitates coexistence of species with different ecological requirements (Barreto, 1999), and has been shown to be positively associated with aquatic species richness in streams and rivers (Wright & Flecker, 2004;Willis et al., 2005). ...
... The positive relationship between LWD and richness of aquatic insect taxa and fish species in the study area is consistent with findings from other studies (e.g. Watson & Hilman, 1997;Wright & Flecker, 2004;Schneider & Winemiller, 2008). This relationship involving fishes has been inferred to be due to the high abundance and diversity of aquatic insects that colonize woody debris and provide food for fishes, as well as the structural complexity of woody debris that provides shelter from predators (Wright & Flecker, 2004;Schneider & Winemiller, 2008). ...
Streams of protected areas should be subjected to less environmental degradation than surrounding areas and consequently support greater aquatic biodiversity. To test this, 186 environmental and landscape variables were measured in 34 streams within the Caxiuanã National Forest (CNF) and its surrounding zone in the eastern Amazon. We expected that streams inside the CNF protected area would have more riparian forest cover and large woody debris (LWD) that increase instream habitat complexity and aquatic biodiversity. Several environmental variables differed between streams in the CNF and surrounding zone; however, the major difference was greater LWD, leaf litter, and channel depth in CNF streams. Richness of fish, Chironomidae, EPT (Ephemeroptera + Plecoptera + Trichoptera), and all-groups combined were positively associated with LWD. Assemblage taxonomic composition was correlated with several variables, but most groups revealed no clear differentiation between the two areas. This lack of differentiation may be explained by relatively minor environmental impacts in areas surrounding the CNF given the region’s small human population. The most notable impact to streams outside of the CNF was removal of LWD to facilitate boat passage. To conserve aquatic biodiversity, we recommend expansion of protected areas and adoption of policies governing land use in surrounding zones.
... Instream wood also contributes to bank stabilization and the formation of islands and mid-channel bars [17,18]. Instream wood also enhances nutrient cycling and carbon storage [19][20][21], benefits the aquatic biota by structuring the habitat [22][23][24], providing spawning areas for fish [16,25,26], increasing shelter, cover and refuge [11,[27][28][29], and increasing the supply of food, organic matter and nutrients [11,30]. Through these many pathways, instream wood generally increases the ecological integrity of flowing waters, as reflected in its positive association with indicators of biotic population and assemblage integrity [31][32][33][34][35]. ...
... Further, high peak discharge per unit drainage area in the tropics, should result in higher wood transport rates [54] leading to even more decay through higher abrasion and breakage rates [55]. Nevertheless, wood in tropical streams still performs important physical and ecological functions [13,23,25,29,33,34]. ...
Instream wood plays important chemical, physical and ecological functions in aquatic systems, benefiting biota directly and indirectly. However, human activities along river corridors have disrupted wood recruitment and retention, usually leading to reductions in the amount of instream
wood. In the tropics, where wood is believed to be more transient, the expansion of agriculture and infrastructure might be reducing instream wood stock even more than in the better studied temperate streams. However, research is needed to augment the small amount of information about wood in different biomes and ecosystems of neotropical streams. Here we present the
first extensive assessment of instream wood loads and size distributions in streams of the wet tropical Amazon and semi-humid-tropical Cerrado (the Brazilian savanna). We also compare neotropical wood stocks with those in temperate streams, first comparing against data from the literature, and then from a comparable dataset from temperate biomes in the USA. Contrary to our expectations, Amazon and Cerrado streams carried similar wood loads, which were lower than the world literature average, but similar to those found in comparable temperate forest and savanna streams in the USA. Our results indicate that the field survey methods and the wood metric adopted are highly important when comparing different datasets. But when properly compared, we found that most of the wood in temperate streams is made-up of a small number of large pieces, whereas wood in neotropical streams is made up of a larger number of small pieces that produce similar total volumes. The character of wood volumes among biomes is linked more to the delivery, transport and decomposition mechanisms than to the total number of pieces. Future studies should further investigate the potential instream wood drivers in neotropical catchments in order to better understand the differences and similarities here detected between biomes and climatic regions.
... The aforementioned characteristics entail an intimate connection with the surrounding terrestrial environment, and freshwater ecosystems tend to accumulate and concentrate impacts related to landscape modification or land use activities in the surrounding watershed (Hynes, 1975;Wear et al., 1998;Townsend et al., 2003). For example, high rates of deforestation in rainforests, either in the past or the present, affect many of the ecological processes occurring in the associated streams (Wright, Flecker, 2004;Paula et al., 2011;Brejão et al., 2018). Intact riparian zones or buffers may perform critical ecological functions in mitigating to some degree the impacts to freshwater systems caused by land cover change (Dwire, Lowrance, 2006). ...
... Although environment-turnover relationships were mostly weak, it is interesting that turnover metrics are mainly related to instream habitat complexity indicators (i.e., litter packs, fine roots, and trees in the stream margin) and forest quality at the watershed and riparian buffer scales. Landscape modifications are known to influence the physical and chemical characteristics of streams (Gorman, Karr, 1978;Cruz et al., 2013;Siqueira et al., 2015;Leal et al., 2016), thereby indirectly affecting many of the ecological processes occurring in streams (Wright, Flecker, 2004;Paula et al., 2011). Maintaining pristine forest remnants associated with landscape complexity and connectivity may extend the prevalence of sensitive species with unique functional traits across the landscape, contributing to the taxonomic and functional integrity of these stream communities. ...
High rates of deforestation, either in the past or the present, affect many of the ecological processes in streams. Integrating deforestation history and the current landscape structure enhances the evaluation of ecological effects of land-use change. This is especially true when contemporary landscape conditions are similar but the temporal path to those conditions differs. One approach that has shown promise for evaluating biodiversity responses over time and space is the β-diversity partitioning, which combines taxonomic and functional trait-based approaches. We tested hypotheses related to stream fish assemblages’ turnover in watersheds with different environmental conditions and deforestation histories. We sampled fish from 75 watersheds in the Machado River basin, Brazil, and environmental factors were quantified at multiple scales. Taxonomic turnover was higher than expected by chance, whereas functional turnover was lower than expected by the observed taxonomic turnover, indicating that deterministic processes are structuring these assemblages. The turnover, and the environmental factors differed among watersheds with different deforestation histories. Besides being scale-dependent, turnover patterns are also likely dependent on land use dynamics and involve time-lags.
... In Amazonia, canopy removal increased light input and water temperature which in turn increased aquatic vegetation cover (Leal et al., 2016;Leitão et al., 2018) and reduced the growth rates of stream fishes (Ilha et al., 2018), respectively. The input of LW is drastically reduced, reducing habitat complexity and tropical fish assemblage diversity (Wright & Flecker, 2004;Paula et al., 2011;Leal et al., 2016;Leitão et al., 2018;Brejão et al., 2018). Local deforestation and grass establishment in the banks create narrower, deeper, and warmer channels (Davies-Coley, 1997;Allmendinger et al., 2005;McBride et al., 2010;Paula et al., 2018). ...
... In the beginning of forest succession, secondary forests have a lower and more open canopy that allows more light to reach the channel (Warren et al., 2016;Bechtold et al., 2017;Yeung et al., 2017;Paula, 2018), keeping the high light incidence, water temperature, and reduced fish growth rates observed in deforested streams (Leal et al., 2016;Ilha et al., 2018;Leitão et al., 2018). By having a low basal area, the small trees delivered to streams are less effective in creating large pools in the channel, reducing channel complexity and fish assemblage diversity (Wright & Flecker, 2004;Paula et al., 2011). Also, these secondary tree species are mostly soft wood, which decompose fast (Cadol & Wohl, 2010) and may not provide long-term food resources and cover to specific fish groups that rely on wood (Power, 2003;Lujan et al., 2011). ...
Riparian deforestation degrades stream habitats, altering fish assemblages’ structure, and composition. In contrast, secondary riparian forests can recover stream habitats and fish assemblages as they recover structural attributes and ecological processes. We evaluated whether the amount and condition of secondary riparian forests were important to conserve fish assemblages in 49 streams sites in eastern Amazonia. We related fish assemblage taxonomic and functional measures to riparian forest amount plus different habitat metrics using regression analysis. We compared assemblage measures among reference forests, abandoned pastures (open canopy), and secondary forests (closed canopy) using ANOVA tests. The amount of secondary forests had little influence on fish assemblages. Species richness, diversity, and functional richness were higher in pasture than in reference sites but returned to pre-disturbance conditions in secondary sites. However, functional evenness was lower in pasture streams and did not recover after secondary forest regrowth. Our results show that secondary riparian forest condition is important to recover some aspects of fish assemblages. However, streams bordered by these forests may have impoverished fish assemblages because some lost sensitive species may take longer to return. Avoiding riparian deforestation is the best strategy to reduce losses in aquatic biodiversity and ecosystem functions in tropical agricultural landscapes.
... Native forest plays a vital role in physical channel heterogeneity by supplying large wood, branches, litter and roots to aquatic systems (Allan, 2004;Jackson et al., 2015). These structures are responsible for creating mesohabitats and microhabitats along stream channels, and for increasing marginal and instream habitat complexity (Harvey, Henshaw, Parker, & Sayer, 2018), which can provide habitat for the establishment of additional and different fish species (Angermeier & Karr, 1984;Pettit et al., 2013;Wright & Flecker, 2004). For instance, a coarse root inside of a channel can create backwater microhabitats, favouring the deposition of drifted material such as leaves, seeds and aquatic or terrestrial insects. ...
... For instance, while streams in the Machado River basin have been experiencing environmental filters associated with deforestation for~40 years (Alves et al., 1998), in the Alto Paraná, native forest removal took place more than 150 years ago (Victor et al., 2005). Indeed, in the Machado basin, wood structures used by several fish species (Pettit et al., 2013;Wright & Flecker, 2004) were still common even in highly deforested catchments. In the Alto Paraná streams, on the other hand, it is likely that functionally distinct fauna had already been lost following the loss of most of the allochthonous structures. ...
• Deforestation can modify stream habitat and the functional structure of fish assemblages. The aims of this study were (a) to identify whether deforestation has a similar effect on local habitats from two biogeographically distinct river basins in a tropical region; (b) to identify how fish trait–habitat relationships were influenced by deforestation; and (c) to compare functional redundancy patterns in these basins.
• Environmental and biological variables were obtained for 160 stream reaches, 85 located in the Alto Paraná River basin and 75 in the Machado River basin. Traits were associated with body size, habitat preference, food items and foraging period. Linear models were constructed to verify the environmental convergence of habitats across streams from the Alto Paraná and the Machado basins. An RLQ and a fourth‐corner analysis were conducted to investigate how deforestation affected habitat variables and trait–habitat relationships. The nearest relative index (NRI) was used as a functional redundancy measure.
• Deforestation led to a similar habitat gradient from streams with a higher proportion of coarse roots in more forested catchments to streams with streamside grasses, bare soil and unconsolidated substrate in more deforested catchments; however, a general pattern of fish trait–habitat relationships was not identified across basins. Functional redundancy was associated with a long history of habitat loss in the Alto Paraná streams, whereas functional complementarity was related to more recent and less intense habitat loss in Machado streams.
• We believe that differences in regional species pools and historical processes between the basins influenced the fish functional responses to deforestation. Nevertheless, the results highlighted the importance of stream habitat heterogeneity and the presence of preserved forest fragments in a region to prevent the loss of unique traits. Decision‐makers should therefore maintain large forest fragments and restore riparian forests to preserve stream habitat and the functional structure of fish assemblages.
... Anthropogenic effects such as habitat alteration, deforestation, pollution and exotic fish introductions, are also factors that threaten autochthonous fish diversity (Bussing, 1998;Beard, 1989;Wolter & Arlinghaus, 2003;Wright & Flecker, 2004). The last is apparently not the case of the Río Pacuare, which is considered one of the few watersheds in Costa Rica that is well-preserved, especially in the middle and upper reaches (Anderson, Freeman & Pringle, 2006a;Anderson, Pringle & Rojas, 2006b;Instituto Costarricense de Electricidad (ICE), 2006). ...
... In the case of the members of the Cichlidae, they were found for the most part in sites of the lower reaches, below 100 m.a.s.l., particularly in sites with low water velocity, with abundant vegetation and logs lying on the river bottom. This pattern reflects that the majority of Cichlidae species that we caught are not well-adapted to withstand fast flowing waters (Winemiller, Kelso-Winemiller, & Brenkert, 1995;Bussing, 1998;Wright & Flecker, 2004;Anderson et al., 2006a). Babler & Babler (1980), Nordlie (1981), and Strydom (2002), describe a higher species richness at the river mouth and lower reaches of tropical rivers based on the use of these areas as centers of reproduction and hatcheries for both, marine and freshwater species, resulting in a high density of juvenile life stages. ...
Fish assemblages and their ecological traits along an elevational gradient in the Río Pacuare, Costa Rica. Between May 2004 and May 2005, we sampled fish in 19 sites, grouped in four elevations, ranging from the river mouth to 650 m.a.s.l. in the Río Pacuare, Caribbean versant of Costa Rica. Changes in the distribution and composition of the fish fauna, as well as patterns of alpha and beta diversity along an elevational gradient were assessed. Additional analyses of habitat preferences, trophic guilds, functional groups and general ecology for the most abundant species are included. All fish captured were classified into 22 families, 43 genera and 53 species. The most abundant family was Characidae, followed by Gobiidae, Mugilidae, Poeciliidae and Heptateridae, which together comprise 87.9 % of all sampled individuals. Elevation shows an inverse effect on species diversity, we observed a monotonic decrease in species richness with increasing elevation (p < 0.05), as reported in other tropical rivers. According to our results, in the Río Pacuare the total fish fauna diversity is found within the first 500 m.a.s.l. Species turnover increases with elevation, while nestedness decreases. Turnover was dominated by the loss of species rather than gain; the higher species loss was registered between the river mouth and the lower river reach (< 100 m.a.s.l.). Seven species can be classified as typical or core species (Astyanax aeneus, Sicydium altum, Agonostomus monticola, Poecilia gillii, Brycon costaricensis, Rhamdia laticauda and Joturus pichardi) along the elevation gradient. The habitat availability and the integration of eco-morphological, feeding and reproductive traits help to explain better the elevation distribution of the complete set of species observed. Although it is possible to identify groups of species characteristic of each reach of river, this does not mean that they are isolated from each other. Natural drift and movement along the river of some species during their life cycle, especially S. altum, A. monticola and J. pichardi, are key processes linking the whole watershed. The present study constitutes a first step in documenting and understanding the distribution and composition of fish assemblages in a watershed that is relatively intact and well-conserved in the Caribbean versant of Costa Rica. Rev. Biol. Trop. 66(Suppl. 1): S132-S152. Epub 2018 April 01.
... As in temperate systems, wood is heterogeneously distributed in tropical rivers and lakes, and woodpiles can be areas of high primary and secondary aquatic productivity (Pyron et al. 1999, Cadol andWohl 2010). Fish respond directly to the distribution and abundance of LWD (Bojsen and Barriga 2002, Wright and Flecker 2004, Willis et al. 2005; however, the mechanisms underlying the responses may differ among ecosystems. Neotropical fishes, for example, are functionally diverse, and grazers-benthic feeders that consume algae and detritus-are especially important in structuring communities and influencing ecosystem function (Wootton and Oemke 1992). ...
... The positive impact of this energy pulse is well documented for invertebrates Wallace 2007, Wallace et al. 2015), algae, and heterotrophic microbes (Benke et al. 1984, Hoellein et al. 2010. Multiple authors have suggested that these energetic effects could percolate up the food web, ultimately providing an additional attractant to grazing, insectivorous, and omnivorous fish (Schindler et al. 2000, Wright andFlecker 2004), although experimental evidence is rare. ...
Understanding the role of interactions in influencing community structure and ecosystem function is a goal in ecology, and identifying biotic entities that are strong interactors is imperative for setting targeted conservation strategies. Several different mechanisms have been linked with strongly interacting species (e.g., predation, competition, abiotic habitat modification), but the most important organisms often influence ecosystems in multiple ways. We propose that these strong interactors share a broad common feature: They catalyze ecosystem processes, such as rates of primary productivity, species interactions, and/or physical disturbances. We provide a case study of Spanish cedar (Cedrela odorata), focusing on its influence as a provider of large woody debris (LWD) on food web dynamics in tropical floodplain rivers and associated oxbow lakes. Large woody debris has been subject to considerable attention because of its perceived importance in creating geomorphologically favorable conditions for target commercial species (e.g., distribution of pools and riffle for salmonids). However, in this study we suggest that LWD catalyzes a suite of ecological processes in addition to geomorphology that determines its important role within aquatic communities. Through a factorial experiment manipulating large and small fish access to treatments with and without LWD piles, we tested the role of Spanish cedar in modifying interactions between different-sized fishes, invertebrates, and primary producers in a tropical floodplain river and associated oxbow lake. Path analysis revealed that fishes influence particulate matter accumulation and invertebrate abundances more so in wood piles than outside of wood piles in both river and lake ecosystem contexts. In addition to providing the first experimental test of factors controlling trophic dynamics in an Amazonian river, we suggest that understanding the role of organisms through the ecological processes they catalyze provides an overarching conceptual framework to link single species and ecosystem-based management strategies.
... The significant relationship between species richness and littoral leaf litter cover reflects the effects of altering or removing riparian vegetation as a result of land-use changes. Although fish communities have been found to be strongly associated with woody material (Wright & Flecker, 2004;Chua et al., 2020), this relationship is not significant for Macrobrachium species. This suggests a greater reliance of Macrobrachium on leaf litter microhabitats for foraging and refuge which is typically associated with lowland peat swamp habitats (Ng & Lim, 1992;Wowor & Ng, 2010), is mostly found in oil palm plantation streams, possibly as a result of the extensive conversion of peatlands to plantation land use in Peninsular Malaysia (Koh et al., 2011). ...
Commodity‐driven forest conversion represents one of the most severe threats to freshwater biodiversity in Southeast Asia, notably causing population declines and the extinction of freshwater fish species. Although a variety of freshwater taxa are likely to be adversely affected by forest conversion, little is known about the impact on ecologically and economically important invertebrates such as decapod crustaceans. This study evaluated the impact of forest conversion and land‐use change on freshwater Macrobrachium shrimp species, using species richness, abundance, and environmental data collected from 20 streams across southern Peninsular Malaysia. Streams were located in three types of landscape: forest; oil palm plantation; and mixed land use, comprising young secondary forest, small‐scale plantations, patches of open and sparsely vegetated areas, and agricultural fields and clearings. Generalized linear models showed that even incomplete change from forest habitats to mixed land use and oil palm plantation resulted in significantly lower Macrobrachium native species richness and higher non‐native species abundance. Native species richness was positively correlated with canopy cover, leaf litter, substrate size, and dissolved oxygen, and was negatively correlated with water temperature and conductivity. Native species richness was also negatively correlated with non‐native species abundance, with non‐native species abundance increasing along the human disturbance gradient. These results highlight the need for riparian habitat protection to conserve native Macrobrachium and limit the spread of non‐native species. A management priority should be to maintain or restore optimum instream habitat conditions for shrimps, which would also benefit fish and other benthic macroinvertebrates. Suitable riparian management requires substantial support and funding from multiple stakeholders, but it can be aligned with other catchment‐based strategies to optimize the use of limited resources available for freshwater biodiversity conservation.
... In small streams, deforestation reduces the availability of large instream wood, which plays critical roles in the structure, diversity, and abundance of fish communities, thus impacting fisheries and ecosystem functions (Wright and Flecker 2004). Loss of smaller debris could impact the benthic insects and macroinvertebrates that fish eat. ...
This Report provides a comprehensive, objective, open, transparent, systematic, and rigorous scientific assessment of the state of the Amazon’s ecosystems, current trends, and their implications for the long-term well-being of the region, as well as opportunities and policy relevant options for conservation and sustainable development.
... This measure was based on Kaufmann & Faustini (2012) and Laub et al. (2012), in order to estimate the EH in freshwater ecosystems, since high CV values indicate stretches with a greater variety of riffles, runs, and pools. The number of microhabitats was estimated by the proportion of flooded vegetation in the stretches, because it is known that such structures (submerged branches, trunks, and roots) create shelters and provide substrate for foraging, reproduction, and spawning for fish, which increase their diversity (Wright & Flecker, 2004). Thus, using an ordering analysis, we can determine which streams have a combination of large amounts of micro-and mesohabitats, that is, streams with high EH. ...
Human activities change the environmental conditions of streams and alter their assemblages. However, the environmental factors associated with the change in the ecomorphological similarity of the fish assemblage have not been investigated enough. In this context, we sampled data from three urban and six rural streams in the Pirapó River Basin to assess which environmental factors influence the taxonomic and ecomorphological structures of the fish assemblage. We hypothesized that (1) streams with greater environmental heterogeneity have higher species diversity; (2) the greater species diversity is associated with a greater diversity of body shapes and coexistence of more ecomorphologically distinct species. Twenty-two ecomorphological indices related to the food acquisition, locomotion, and habitat use of species were used to calculate interspecific ecomorphological distances that were analyzed using principal component analysis and multiple linear regression. The results show that the rural streams showed less degraded environmental conditions and greater environmental heterogeneity than the urban ones, which was related to the increase in species diversity and ecomorphological similarity of the assemblage. We can conclude that streams containing greater environmental heterogeneity can support more diverse fish assemblages. Furthermore, environmental degradation results in the loss of ecomorphologically similar species, in which only those with distinct ecological requirements remain in the degraded streams. Therefore, conservation efforts that aim at sustaining environmental heterogeneity and mitigating urban land use do not only maintain the species’ diversity, but also the coexistence of ecomorphological similar fishes.
... We agree that LW may not be acting solely on the channel recovery observed here and we are also not encouraging restoration practitioners to randomly throw wood into tropical streams. Our aim is to emphasize the opportunity to seize this in-stream residual structure due to its structural role in the ecosystem and as a fish biodiversity stronghold (Wright and Flecker, 2004;Lujan et al., 2011), which is important to reduce habitat degradation and biodiversity loss during passive stream recovery (especially because active wood addition to the channels is complex, expensive, and many times, ineffective (Palmer et al., 2014)). Resilience loss is also exacerbated by land-use history and the landscape context of the recovering sites. ...
Forest regeneration has increased in many tropical abandoned lands and current restoration commitments in this region aim to restore over 1,400,000 km² of degraded land by 2030. Although regenerating forests recover biomass, biodiversity, and processes with time, the recovery trajectories may be uncertain due to past disturbances. Currently, there is a lack of knowledge to sustain the effectiveness of passive regeneration for the recovery of riparian forests and the adjacent waterbodies in the tropics, which may compromise the outcomes of ongoing and future tropical riparian restoration programs. We evaluated the drivers of riparian forest structural recovery and how this relates to stream conditions in 12 abandoned pasturelands in eastern Brazilian Amazonia. These pasturelands range across regeneration age (pasture (PA) — 0 to 4 years; young regeneration (YR) — 8 to 12 years; old regeneration (OR) — 18 to 22 years) and years of past land-use (PA — 23.25 average years of past land-use, YR — 18.25, OR — 7). We compared the conditions of these sites to 4 reference sites with conserved forests (REF, >100 years), where there was no recorded pasture use in the past. Short-term responses of forests and streams to passive regeneration indicated high ecosystem resilience after low to intermediate past land-use intensity, reflected in the improvement of stream ecosystems. Such high resilience is possibly attributable to low- to intermediate-intensity pasture-related disturbances, remaining forest matrix, and residual structures (e.g. roots, sprouts, and in-stream wood) observed in the area. Our results suggest a recovery by 12 to 20 years for riparian forests of this region. However, areas degraded by intensive land-use apparently showed delayed recovery. We conclude that seizing resilience windows (defined here as the period when ecosystems retain high potential resilience) is essential to foster passive recovery of riparian forests and streams more cost-effectively in the tropics.
... As anthropogenic influences increase in magnitude over time, stream conditions move beyond thresholds of tolerance and most organisms adapted to natural conditions ultimately decrease in abundance or even become locally extirpated (Allan, 2004;Dala-Corte et al., 2020), and richness declines (Wright & Flecker, 2004;Iñiguez-Armijos et al., 2014;Fugère et al., 2016). Ultimately driving these patterns are individual responses of taxa to the specific changes and stressors described above, and subsequent trophic cascades. ...
Recent waves of illegal deforestation for cattle pasture are damaging the Indio Maíz Biological Reserve and Rama-Kriol Territory of Nicaragua, with negative consequences to aquatic ecosystems and the people they support. This study creates a framework for how deforestation from cattle ranching causes shifts in stream community structure, mediated by changes in stream habitat over time. It integrates temporally explicit land use information with stream habitat, macroinvertebrate, freshwater shrimp, and fish community data to assess impacts of cattle ranching on 15 headwater streams. The deforestation history measure (DHM), a product of deforestation amount and time since deforestation for each catchment, strongly predicted stream habitat and biotic responses. Delayed effects of land-use change such as decreased allochthonous inputs (large wood, debris) and increased bank destabilization, sedimentation, flashiness, and the scouring effect were apparent in longer deforested catchments, causing lower richness and density and higher evenness of macroinvertebrates; lower shrimp abundance; and distinct changes in fish and invertebrate community composition. Both recently and longer deforested catchments had degraded riparia and smaller sized game fish. Otherwise, recently deforested catchments were more similar to forested catchments. Nicaragua’s understudied primary rainforest ecosystems should be high priority for research and conservation before they are lost.
... Curimbatá, Prochilodus lineatus, is another indigenous species in Brazil also known as curimba or curimatã. This species is exploited by fisheries and aquaculture in different regions of South America [12,[23][24][25][26][27]. This is an iliophagus fish that feeds predominantly on fine-particle organic matter and periphyton over the bottom of rivers and lakes [28,29]. ...
A single farmed fish species assimilates about 20% of the nutrients in the supplied diet. This study evaluated if the culture of complementary ecological-function species can recover nutrients dispersed into water and transform them into high-valued biomass. A completely randomized experiment was designed with three treatments and four replications of each production system: monoculture of lambari (Astyanax lacustris); integrated aquaculture of lambari and Amazon river prawn (Macrobrachium amazonicum); and integrated aquaculture of lambari, Amazon river prawn, and curimbatá (Prochilodus lineatus). Fingerlings of lambari (0.8 ± 0.8 g) were stocked in twelve earthen-ponds (0.015 ha) at the density of 50 fish m−2. Eight ponds were stocked with juveniles of Amazon river prawn (1.1 ± 0.2 g) at the density of 25 prawn m−2. Four of these eight ponds were stocked with curimbatá fingerlings (0.2 ± 0.1 g) at a density of 13 fish m−2. Only lambari was fed twice a day with an extruded commercial diet. The experiment lasted 60 days when lambari attained commercial size. The inclusion of prawn increased the total species yield from 1.8 to 2.4 t ha−1 cycle−1 and reduced the feed conversion ratio (FCR) from 2.5 to 1.8. The inclusion of prawn and curimbatá increased the total yield to 3.2 t ha−1 cycle−1 and reduced the FCR to 1.4. Therefore, the integrated culture of lambari, prawn, and curimbatá improves the use of space, water, feed, and benthic species to recover the large quantity of nutrients accumulated in the bottom of lambari pond production, converting them into high-nutritional and monetary-valued biomass.
... Curimbatá, Prochilodus lineatus, is another indigenous species in Brazil also known as curimba or curimatã. This species is exploited by fisheries and aquaculture in different regions of South America [12,[23][24][25][26][27]. This is an iliophagus fish that feeds predominantly on fine-particle organic matter and periphyton over the bottom of rivers and lakes [28,29]. ...
A single farmed fish species assimilates about 20% of the nutrients in the supplied diet. This study evaluated if the culture of complementary ecological-function species can recover nutrients dispersed into the water and transform them into high-valued biomass. A completely randomized experiment was designed with three treatments and four replications of each production system: monoculture of lambari (Astyanax lacustris); integrated aquaculture of lambari and Amazon river prawn (Macrobrachium amazonicum); and integrated aquaculture of lambari, Amazon river prawn, and curimbatá (Prochilodus lineatus). Fingerlings of lambari (0.8 ± 0.8 g) were stocked in twelve earthen-ponds (0.015 ha) at the density of 50 fish m-2. Eight ponds, were stocked with juveniles of Amazon river prawn (1.1 ± 0.2 g) at the density of 25 prawn m−2. Four of these eight ponds were stocked with curimbatá fingerlings (0.2 ± 0.1 g) at a density of 13 fish m-². Only lambari was fed twice a day with an extruded commercial diet. The experiment lasted 60 days when lambari attained commercial size. The inclusion of prawn increased the total species yield from 1.8 to 2.4 t ha-1 cycle-1 and reduced the feed conversion ratio (FCR) from 2.5 to 1.8. The inclusion of prawn and curimbatá increased the total yield to 3.2 t ha-1 cycle-1 and reduced the FCR to 1.4. Therefore, the integrated culture of lambari, prawn, and curimbatá improves the use of space, water, feed, and benthic species can recover the large quantity of nutrients accumulated in the bottom of lambari pond production, converting them into high-nutritional and monetary-valued biomass.
... Curimbatá, Prochilodus lineatus, is another indigenous species in Brazil also known as curimba or curimatã. This species is exploited by fisheries and aquaculture in different regions of South America [12,[23][24][25][26][27]. This is an iliophagus fish that feeds predominantly on fine-particle organic matter and periphyton over the bottom of rivers and lakes [28,29]. ...
A single farmed fish species assimilate about 20% of the nutrients in the supplied diet. This study evaluated if the culture of complementary ecological-function species can recover nutrients dispersed into the water and transform them into high-valued biomass. A completely randomized experiment was designed with three treatments and four replications of each production system: monoculture of lambari (Astyanax lacustris); integrated aquaculture of lambari and Amazon river prawn (Macrobrachium amazonicum); and integrated aquaculture of lambari, Amazon river prawn, and curimbatá (Prochilodus lineatus). Fingerlings of lambari (0.8 ± 0.8 g) were stocked in twelve earthen-ponds (0.015 ha) at the density of 50 fish m-2. Eight ponds, were stocked with juveniles of Amazon river prawn (1.1 ± 0.2 g) at the density of 25 prawn m−2. Four of these eight ponds were stocked with curimbatá fingerlings (0.2 ± 0.1 g) at a density of 13 fish m-². Only lambari was fed twice a day with an extruded commercial diet. The experiment lasted 60 days when lambari attained commercial size. The inclusion of prawn increased the total species yield from 1.8 to 2.4 t ha-1cycle-1 and reduced the FCR from 2.5 to 1.8, whereas The inclusion of prawn and curimbatá increased the total yield to 3.2 t ha-1cycle-1 and reduced the FCR to 1.4. Therefore, the integrated culture of lambari, prawn, and curimbatá improves the use of space, water, feed, and benthic species can recover the large quantity of nutrients accumulated in the bottom of lambari pond production, converting them into high-nutritional and monetary-valued biomass.
... Freshwater fishes have evolved over geological time scales to inhabit portions of rivers with certain sets of environmental and physical characteristics. Logs, woody debris, rocks, fallen leaves, macrophytes, natural caves, etc., are often required for routine activities such as procuring food and for reproduction (Angermeier & Karr, 1984;Grenouillet et al., 2002;Lo et al., 2020;Wright & Flecker, 2004;Zeni & Casatti, 2014). When the physical substrate of the river is altered, the affected portion of T A B L E 2 Critically endangered (CR), endangered (EN), near threatened (NT) and vulnerable (VU) freshwater fishes of Ecuador identified by the national endangered freshwater fishes working group (Aguirre et al., 2019b) the river often becomes a very poor or unusable habitat for native species. ...
Freshwater fish communities in Ecuador exhibit some of the highest levels of diversity and endemism in the Neotropics. Unfortunately, aquatic ecosystems in the country are under serious threat and conditions are deteriorating. In 2018-19, the government of Ecuador sponsored a series of workshops to examine the conservation status of Ecuador's freshwater fishes. Concerns were identified for 35 species, most of which are native to the Amazon region, and overfishing of Amazonian pimelodid catfishes emerged as a major issue. However, much of the information needed to make decisions across fish groups and regions was not available, hindering the process and highlighting the need for a review of the conservation threats to Ecuador's freshwater fishes. Here, we review how the physical alteration of rivers, deforestation, wetland and floodplain degradation, agricultural and urban water pollution, mining, oil extraction, dams, overfishing, introduced species, and climate change, are affecting freshwater fishes in Ecuador. Although many of these factors affect fishes throughout the Neotropics, the lack of data on Ecuadorian fish communities is staggering and highlights the urgent need for more research. We also make recommendations including the need for proper enforcement of existing environmental laws, restoration of degraded aquatic ecosystems, establishment of a national monitoring system for freshwater ecosystems, investment in research to fill gaps in knowledge, and encouragement of public engagement in citizen science and conservation efforts. Freshwater fishes are an important component of the cultural and biological legacy of the Ecuadorian people. Conserving them for future generations is critical.
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... In the Venezuelan Andean piedmont, where deforestation was particularly acute and diminished connectivity with downstream floodplains, the abundance of migratory fishes, including Prochilodus spp., was severely reduced (Winemiller et al., 1996). Deforestation usually also reduces the input of large wood in local streams, depleting fish species richness and abundance, including many migratory species, with potential consequences for fisheries and ecosystem functioning (Wright & Flecker, 2004). Recent analyses of stable isotopes demonstrated that terrestrial plant material and arthropods were the most important items contributing to migratory fish biomass in the oligotrophic Apaporis River floodplains in Colombia, emphasizing the importance of seasonally flooded forests for sustaining fisheries in the Amazon basin (Correa & Winemiller, 2018). ...
• The Amazon basin hosts the Earth's highest diversity of freshwater fish. Fish species have adapted to the basin's size and seasonal dynamics by displaying a broad range of migratory behaviour, but they are under increasing threats; however, no study to date has assessed threats and conservation of Amazonian migratory fishes.
• Here, the available knowledge on the diversity of migratory behaviour in Amazonian fishes is synthesized, including the geographical scales at which they occur, their drivers and timing, and life stage at which they are performed.
• Migratory fishes are integral components of Amazonian society. They contribute about 93% (range 77–99%) of the fisheries landings in the basin, amounting to ~US$436 million annually.
• These valuable fish populations are mainly threatened by growing trends of overexploitation, deforestation, climate change, and hydroelectric dam development. Most Amazonian migratory fish have key ecological roles as apex predators, ecological engineers, or seed‐dispersal species. Reducing their population sizes could induce cascading effects with implications for ecosystem stability and associated services.
• Conserving Amazonian migratory fishes requires a broad portfolio of research, management, and conservation actions, within an ecosystem‐based management framework at the basin scale. This would require trans‐frontier coordination and recognition of the crucial importance of freshwater ecosystems and their connectivity.
• Existing areas where fishing is allowed could be coupled with a chain of freshwater protected areas. Management of commercial and subsistence species also needs fisheries activities to be monitored in the Amazonian cities and in the floodplain communities to allow assessments of the status of target species, and the identification of management units or stocks. Ensuring that existing and future fisheries management rules are effective implies the voluntary participation of fishers, which can be achieved by increasing the effectiveness and coverage of adaptive community‐based management schemes.
... Pristine stream communities depend on allochthonous introductions of leaf litter and invertebrates (Pusey and Arthington 2003), which influence food web and community structure (Knight and Bottoroff 1984;Silva et al. 2014;Lorion and Kennedy 2009). Additionally, large woody debris is more common in forested reaches and provides habitat structuring, slows stream flow, and provides substrate for periphyton growth (Wang et al. 2003;Wright and Flecker 2004;Mellina and Hinch 2009). The removal of riparian vegetation opens the canopy, increasing temperature (Johnson and Jones 2000;Cole and Newton 2013) and inputs of photosynthetically active radiation (Rutherford et al. 1999), ultraviolet radiation (Kelly et al. 2003), and nutrients (Bennet et al. 2001;Naiman et al. 2005). ...
Environmental conditions influence ecological processes that shape stream community diversity and abundance. Deforestation has the potential to limit available particulate organic matter and raise stream temperatures. The degree to which tropical stream communities are impacted by these changes is likely to differ between systems, but empirical data from tropical regions are lacking. This lack of baseline data hinders conservation policy as well as efforts to better understand biogeographic and anthropogenic impacts on species’ distributions. To fill this knowledge gap, we surveyed 27 sites in six previously unstudied streams across a gradient of deforestation in northwest Ecuador and assessed the degree to which localized deforestation predicted patterns of community composition of fishes. Using general linear mixed models and AICC we found that neither forest fragmentation nor canopy closure was a significant predictor of species richness and found no difference between the species richness of fragmented and continuous sites. However, forest fragmentation was a strong predictor of abundance, occurring in 31 of 31 general linear mixed models, with higher abundance in fragmented forest than in continuous forest. Of 16 species found, eight occurred at five or more sites and one (Pseudochalceus boehlkei), numbered 200 out of 627 individuals. NMDS and SIMPER analysis suggested that community composition differed between fragmented and continuous sites. P. boehlkei, Pseudopoecilia fria, and Astroblepus cf. fissidens species presented in higher abundances in deforested sites, possibly suggesting a less functionally diverse community. This pattern is consistent with neotropical streams that have experienced partial deforestation but not total degradation of habitat.
... The spatial scale of fish responses is a particularly important consideration for IWH restoration. The relationship between fish and IWH at small spatial scales is well demonstrated (Lehtinen, Mundahl, & Madejczyk, 1997;Roni & Quinn, 2001;Wright & Flecker, 2004). For example, fish diversity, distribution and abundance (especially of salmonids in the northern hemisphere) has been positively associated with IWH through the provision of critical mesohabitats such as increasing pool area and diversity of hydrodynamic conditions (Bisson, Sullivan, & Nielsen, 1988;Cederholm et al., 1997;House & Boehne, 1986;Roni et al., 2015;Rosenfeld, Porter, & Parkinson, 2000). ...
• Removal of instream woody habitat (IWH) is one factor attributed to declines in fish populations worldwide. Restoration of IWH to help fish populations recover is now common; however, quantitative predictions about the outcomes of these interventions is rare. As such, quantitative links between IWH and fish abundance is of interest to managers to inform conservation and restoration activities.
• Links between instream habitat attributes, especially IWH, and selected fish species of recreational, cultural, and ecological significance were explored at 335 sites spanning eight streams across south‐eastern Australia. Data were collected on fish abundance and length, IWH density and a range of other habitat attributes at a scale that incorporated at least one of each of the major mesohabitat types (functional river elements). The data were analysed using Bayesian hierarchical generalized linear mixed models to examine fish habitat associations and used to make quantitative predictions of responses to future restoration.
• Strong positive relationships were found between fish abundance and IWH density and the strength of this relationship varied between species and waterways. Murray cod (Maccullochella peelii ), a species commonly targeted by IWH interventions, displayed the strongest association with IWH density. River blackfish (Gadopsis marmoratus ) also showed a significant relationship with IWH, but this effect was waterway specific. Fish length was only related to IWH for river blackfish. These results may reflect differences in the life histories of these two species. We suggest that differences in habitat association through ontogeny may be more relevant at smaller spatial scales.
• The results generated in this study can be used to guide waterway restoration and develop quantitative predictions about how fish might respond to IWH interventions across south‐eastern Australia. This approach provides a powerful quantitative framework within which to explore management options and objectives, and to test our predicted responses to habitat restoration.
... Curimbata (Prochilodus spp) is a group of iliophagus South-American native species exploited by fisheries and aquaculture in different regions (Wright and Flecker, 2004;Taylor et al., 2006;Sampaio et al., 2010;Freire et al., 2012;Saint-Paul, 2017). In the past decades, Prochilodus lineatus was introduced in the aquaculture of China and Vietnam and has been used in integrated culture (Kalous et al., 2012). ...
In the integrated culture of pelagic fishes and benthic prawns, a large quantity of nutrients and energy remain in the pond bottom after harvest. This study assessed whether the inclusion of an iliophagus species, such as curimbata (Prochilodus lineatus), can take advantage of those resources and improves yield and diet use efficiency in tambaqui (Colossoma macropomum) and Amazon river prawn (Macrobrachium amazonicum) integrated aquaculture. A completely randomized experiment was designed with two treatments, and five replicates each of integrated systems: tambaqui and Amazon river prawn (TP) and tambaqui, Amazon river prawn, and curimbata (TPC). Ten 0.01-ha earthen ponds were used as experimental unities. Juveniles of tambaqui (3.93 ± 1.63 g) and Amazon river prawn (0.02 ± 0.02 g) were stocked in all ponds at a density of 3 and 11 individuals per m⁻², respectively. Five ponds, selected at random, were also stocked with curimbata (3.11 ± 2.61 g) at a density of 5 individuals per m⁻². Tambaqui was fed twice a day with an extruded commercial diet (32% crude protein) to apparent satiation. The prawn and curimbata were not fed. The experiment lasted 53 days. The presence of curimbata did not affect tambaqui performance, whereas reduced the production of prawn in ~25%. The inclusion of curimbata increased total species yield by ~35% (from 734 to 991 kg.ha⁻¹) and decreased FCR by ~31% (from 0.61 to 0.42). These results indicate that a mud-feeder like curimbata can take advantage of the large quantity of nutrients and energy deposited in the bottom of freshwater pond aquaculture.
... For instance, riparian vegetation provides food, such as fruits and terrestrial insects, that is important to both specialized and generalist fish species that feed on allochthonous items (Allan et al. 2003;Dala-Corte et al. 2017). Submerged tree roots on the stream banks and wood debris provide refuge for several specialized fish species, in addition to creating heterogeneous hydraulic microhabitats (Wright and Flecker 2004). Riparian shading reduces water temperature and also serves as a refuge for other fish species (Macedo et al. 2013). ...
Despite the importance of assessing beta diversity to understand the effects of human modifications on biological communities, there are almost no studies that properly addressed how beta diversity varies along anthropogenic gradients. We developed an algorithm to calculate beta diversity among a set of sites included in a moving window along any given environmental gradient. This allowed us to assess beta diversity among sites with similar conditions in terms of human modifications (e.g., land use or instream degradation). We investigated beta diversity using stream fish community data and indicators of human modification quantified at four spatial scales (whole catchment, riparian, local, and instream). Variation in beta diversity was dependent on the scale of human modifications (catchment, riparian, local, instream, and all four scales combined) and on the type of diversity considered (taxonomic or functional). We also found evidence for non-linear responses of both taxonomic and functional beta diversity to human-induced environmental alterations. Therefore, the response of beta diversity was more complex than expected, as it depended on the scale used to quantify human impact and exhibited opposite responses depending on the location along the environmental impact gradient and on whether the response was taxonomic or functional diversity. Anthropogenic modifications can introduce unexpected variability among stream communities, which means that low beta diversity may not necessarily indicate a degraded environmental condition and high beta diversity may not always indicate a reference environmental condition. This has implications for how we should consider beta diversity in environmental assessments.
... Beberapa penelitian sebelumnya telah menunjukkan adanya pengaruh meningkatnya masukkan partikel tersuspensi dan kekeruhan terhadap komunitas ikan dan makroavertebrata, termasuk insekta air, sebagai komponen dalam jejaring makanan di sungai. Beberapa jenis ikan cenderung menghindari perairan yang keruh karena akan mengurangi kemampuan mencari makan secara efektif (Berg & Northcote 1985, Bruton 1985, Vogel & Beauchamp 1999, Sweka & Hartman 2003, Sutherland & Meyer 2007, Zamor & Grossman 2007 berkaitan dengan menurunnya jarak reaktif ikan secara visual ketika mencari makan (Barrett et al. 1992, Shoup & Wahl 2009, Carter et al. 2010) dan/atau kecepatan ikan dalam mencari makan (Rowe & Dean 1998). Kondisi ini akan berakibat pada penurunan laju pertumbuhan ikan (Sigler et al. 1984, Northcote 1995, kelimpahan dan penyebarannya (Berkman & Rabeni 1987, Rowe et al. 2000, Mol & Ouboter 2004. ...
The research on feeding effectivity of arfak rainbowfish conducted at Fisheries Laboratory, Faculty of Fishes and Marine Scince, University of Papua in July to December 2016. The purpose of this research is to describe feeding effectivity of the fish at several levels of water turbidity. The fish samples used in the treatment, collected from Nimbai Stream, Prafi River system, Manokwari were acclimatized for a month in the laboratory. The fish were selected based on the body length and categorized into six size classes. Each individual of the fish was treated with 200 individuals of mosquito larvae (instar IV stage) at seven turbidity levels (2.54, 25.07, 50.52, 100.20, 500.60, and 800.40 Nephelome-tric Turbidity Unit, NTU) using particles with size of <63um. Feeding effectivity was indicated by the level of preda-tion in a period of 15 minutes. The results of the research showed that average level of predation did not differ among size classes at the low level of turbidity (<50,52 NTU). The significant decrease in the average level of predation occurred at the higher level of turbidity (<100,12 NTU) with the values range from 23.2% to 65.9%. This indicated a decrease in the feeding effectivity as the turbidity levels increase. AbstrakPenelitian efektivitas ikan pelangi arfak dalam mencari makan dilaksanakan di Laboratorium Perikanan FPIK Univer-sitas Papua pada bulan Juli sampai Desember 2016. Tujuan penelitian ini untuk mendeskripsikan efektivitas ikan pela-ngi arfak mencari makan pada beberapa tingkat kekeruhan air. Contoh ikan yang digunakan dalam perlakuan dikoleksi dari Sungai Nimbai, sistem Sungai Prafi, Manokwari yang diaklimatisasi selama satu bulan di laboratorium. Individu ikan yang digunakan dalam penelitian ini dipilih berdasarkan panjang tubuh dan dikelompokkan ke dalam enam kelas ukuran. Setiap individu ikan diberi perlakuan pakan berupa larva nyamuk (tahap instar IV) sebanyak 200 individu pada tujuh tingkat kekeruhan yang berbeda (2,54; 25,07; 50,52; 100,20; 200,20; 500,60 dan 800,40 Nephelometric Turbidity Unit, NTU) dengan menggunakan partikel berukuran <63um. Efektivitas mencari makan akan ditunjukkan berdasarkan tingkat pemangsaan dalam periode 15 menit. Tingkat pemangsaan rata-rata tidak berbeda pada tingkat kekeruhan yang rendah (<50,52 NTU) dalam setiap kelas ukuran. Penurunan tingkat pemangsaan rata-rata secara nyata mulai berlang-sung pada tingkat kekeruhan yang lebih tinggi (<100,12 NTU) dengan nilai sebesar 23,2%-65,9%. Kondisi ini menun-jukkan penurunan efektivitas mencari makan seiring dengan semakin meningkatnya tingkat kekeruhan air.
... Although the species detection using eDNA metabarcoding remains incomplete, data were not influenced by the physical characteristics of the stream. In contrast, deep pools or burden areas, such as fallen submerged trees, cannot be sampled by rotenone (no access to the fish lying above branches or at the bottom), although these areas are known to be inhabited by a rich fish fauna (Wright & Flecker, 2004). Using traditional methods, the same habitat types are therefore sampled at all investigated sites , which probably hides interdrainage discrepancies and therefore causes the underestimation of faunistic distinctiveness between river drainages. ...
Determining the species compositions of local assemblages is a prerequisite to understanding how anthropogenic disturbances affect biodiversity. However, biodiversity measurements often remain incomplete due to the limited efficiency of sampling methods. This is particularly true in freshwater tropical environments that host rich fish assemblages, for which assessments are uncertain and often rely on destructive methods. Developing an efficient and non‐destructive method to assess biodiversity in tropical freshwaters is highly important. In this study, we tested the efficiency of environmental DNA (eDNA) metabarcoding to assess the fish diversity of 39 Guianese sites. We compared the diversity and composition of assemblages obtained using traditional and metabarcoding methods. More than 7,000 individual fish belonging to 203 Guianese fish species were collected by traditional sampling methods, and ~17 million reads were produced by metabarcoding, among which ~8 million reads were assigned to 148 fish taxonomic units, including 132 fish species. The two methods detected a similar number of species at each site, but the species identities partially matched. The assemblage compositions from the different drainage basins were better discriminated using metabarcoding, revealing that while traditional methods provide a more complete but spatially limited inventory of fish assemblages, metabarcoding provides a more partial but spatially extensive inventory. eDNA metabarcoding can therefore be used for rapid and large‐scale biodiversity assessments, while at a local scale, the two approaches are complementary and enable an understanding of realistic fish biodiversity.
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... Because of this strong link between riparian and lotic ecosystems, the removal of forests is expected to disrupt allochthonous resource inputs and negatively affect the trophic structure of ichthyofauna (e.g., Wright and Flecker 2004;Leite et al. 2015). Over the past several years, the advancement of agriculture and cattle farming has been identified as the primary cause of deforestation in Brazilian rainforests (Morton et al. 2006;Santos et al. 2015). ...
The role of riparian forests in the functioning of aquatic ecosystems is well known, and they are recognized as an important food source for riverine fauna. This study investigates the trophic structure of coastal freshwater stream fishes from a large conservation area in an Atlantic rainforest using stomach content and food availability analyses. Four samples were collected from 19 sample sites. Fishes were caught with electrofishing. Prey were sampled with trays, Surber, traps, and electrofishing to evaluate the availability of food resources. The diets of 20 fish species were determined from the stomach contents of 1691 individuals. Terrestrial and aquatic insects and detritus were the most consumed items. Fish diet and prey availability were not seasonally dependent. A cluster analysis showed five trophic functional groups: terrestrial insectivores, aquatic insectivores, detritivores, carnivores, and omnivores. Insectivores predominated in species richness (60%), abundance (47%) and biomass (39%). Allochthonous and autochthonous items were found in similar proportions in the environment; however, allochthonous items were representative for insectivores and detritivores, whereas autochthonous items were important for primarily aquatic insectivores. The preference for certain insects by insectivorous fishes was associated with food selectivity rather than the availability of the resource and demonstrated the strong relationship between feeding behavior and food preference. The absence of seasonal variation in the diets of the fishes was possibly related to the consistent food supply. Our results confirm the role of the forest as a food provider for stream fishes, such as terrestrial insects and plant debris/detritus (also consumed by aquatic insects, which subsequently serve as food for fish), highlighting the importance of conserving the Brazilian Atlantic rainforests.
... cyprinid, energetics, global change, Kibale National Park, land use, mark-recapture, predator- prey interaction, thermal adaptation and the invertebrates on which they prey (Wantzen, 2006;Wright & Flecker, 2004). Streams affected by land use therefore constitute an excellent system to compare the relative importance of meta- bolic vs. other (temperature-unrelated) anthropogenic influences on the performance and trophic interactions of ectotherms such as fish. ...
In ectotherms, anthropogenic warming often increases energy requirements for metabolism, which can either impair growth (when resources are limiting) or lead to higher predator feeding rates and possibly stronger top-down trophic interactions. However, the relative importance of these effects in nature remains unclear because: 1) thermal adaptation or acclimation could lower metabolic costs; 2) greater prey production at warmer temperatures could compensate for higher predator feeding rates; and/or 3) temperature effects on trophic interactions via altered biological rates could be small relative to other, temperature-unrelated human impacts on food webs. 2.Here, we examined effects of deforestation-associated warming on the minnow Enteromius neumayeri, occurring in both forested (cool) and deforested (warm) streams located inside or nearby an afrotropical rainforest. Combining approaches from physiological and community ecology, we quantified impacts of anthropogenic warming on the metabolism, growth, and trophic interactions of this tropical ectotherm. We then compared these effects with impacts of land use unrelated to temperature. 3.In a long-term laboratory acclimation experiment quantifying the temperature-dependence of growth and metabolism in E. neumayeri, warming increased metabolic rates and decreased growth (at a limited ration). We found no evidence of local (thermal) adaptation, with warming affecting farm and forest populations similarly. 4.Then, using mark-recapture methods to quantify impacts of warming on performance in situ, we found similar growth rates in fish from deforested and forested streams despite their distinct thermal environments. This suggests higher prey consumption at deforested sites to compensate for greater metabolic costs, which could strengthen fish-invertebrate interactions. 5.Finally, we developed a bioenergetics model to estimate fish-invertebrate interaction strength and quantify temperature-related and unrelated impacts of land use on this interaction. We found that although warming increased fish consumption, it apparently increased invertebrate production even more and thus had a net weakening effect on estimated interaction strength. Most importantly, variation in both fish and invertebrate density not directly related to temperature had a much stronger influence on estimated interaction strength than temperature effects on predator consumption and prey growth. 6.We conclude that ectotherms can sometimes offset the metabolic costs of warming with a small increase in consumption that hardly effects food web interactions compared to non-metabolic impacts of anthropogenic disturbances. Future research should assess whether this is a common feature of heavily-impacted ecosystems facing multiple stressors. This article is protected by copyright. All rights reserved.
... Changes in land use along the catchment, such as agriculture, affect negatively the structure of remaining riparian vegetation (Heartsill-Scalley and Aide 2003). Consequently, these changes affect the stream habitat due to a higher incidence of light, reduction of allochthonous organic matter input (Fernandes et al. 2012), changes in chemical elements of water (De Souza et al. 2013), and reducing the offer of shelter for organisms (Crook and Robertson 1999;Wrigth and Flecker 2004). The network of dirt roads used for cash crops has also been considered an important modifying agent of stream habitat, mainly contributing with the siltation of this system, which affects the water physical-chemical feature and biodiversity (McClain and Elsenbeer 2001;Wantzen and Mol 2013). ...
The aim of this research is to assess the effects of oil palm plantations on stream habitat and their fish assemblage diversity. We hypothesize that streams which drain through oil palm plantations tend to be less heterogeneous, limiting the occurrence of many species, than streams that drain through forest fragments, which support higher fish diversity. A total of 17 streams were sampled; eight in forest fragments and nine in oil palm plantations. Environmental and biological variables were sampled along 150 m stretch in each stream. Of the 242 environmental variables measured, ten were considered important to assess the condition of structural habitat, and out of these variables, four were considered relevant in the distinction between streams in oil palm plantations and forest fragments. A total of 7245 fishes were collected, belonging to 63 species. Unlike our original hypothesis, the species richness did not differ between forest fragment and oil palm plantations streams, showing that it is not a good divert measure in streams disturbance assessment. However, fish assemblages differed in species composition, and 56 species were recorded in oil palm plantation streams, while 44 species were recorded in forest fragments streams. Some species were identified as indicators of either altered (Aequidens tetramerus and Apistogramma agassizii) or undisturbed areas (Helogenes marmoratus). Overall, oil palm plantations were proven to change stream habitat structure and fish species distribution, corroborating other studies that have evidenced changes in patterns of biological community structure due to impacts by different land uses.
... changing species composition; Smokorowski & Pratt, 2007). In line with these expectations, studies of riparian deforestation of streams have found varied effects on fish biomass but consistent changes in assemblage structure (Bojsen, 2005;Bojsen & Barriga, 2002;Dias, Magnusson, & Zuanon, 2010;Giam et al., 2015;Iwata, Nakano, & Inoue, 2003;Jones, Helfman, Harper, & Bolstad, 1999;Kouamé, Yao, Bi, Kouamélan, & N'Douba, 2008;Lorion & Kennedy, 2009;Sweeney et al., 2004;Teresa & Casatti, 2012;Wright & Flecker, 2004). Loss of stream canopy cover generally increases light intensity and decreases inputs of allochthonous materials, increasing the portion of the fish community that is supported by autochthonous food sources such as phytoplankton (Allan, 2004;Angermeier & Karr, 1983). ...
Inland fisheries underpin food security in many tropical countries. The most productive inland fisheries in tropical and subtropical developing countries occur in large river–floodplain systems that are often impacted by land cover changes. However, few studies to date have assessed the effects of changes in floodplain land cover on fishery yields. Here, we integrated fisheries and satellite-mapped habitat data to evaluate the effects of floodplain deforestation on fishery yields in 68 floodplain lake systems of the lower Amazon River, representing a wide range in relative amounts of woody, herbaceous and non-vegetated land cover. We modelled relative fish yields (fish capture per unit effort [CPUE]) in the floodplain lakes as a function of the relative amounts of forest, shrub, aquatic macrophyte and bare/herbaceous habitats surrounding them. We found that forest amount was positively related (p = .0003) to multispecies CPUE. The validity of these findings was supported by rejection of plausible alternative causative mechanisms involving habitat-related differences in amount of piscivores, fishing effort, lake area, and habitat effects on CPUE of the nine taxa dominating multispecies yields. Our results provide support to the idea that removal of floodplain forests reduces fishery yields per unit effort. Increased protection of floodplain forests is necessary to maintain the food, income and livelihood security services provided by large river–floodplain fisheries.
... For example, deforestation contributes to widespread biodiversity change in streams through its effects on flow complexity, depth, substrate composition, stream bank stability, and structural complexity (Gorman & Karr 1978;Cruz et al. 2013). Previous studies in the Neotropics demonstrate that high deforestation rates in rainforests, either in the past or in the present, affect many of the ecological processes occurring in streams (Wright & Flecker 2004;Paula et al. 2011). This includes the alteration of stream fish diversity and assemblage structure (Bojsen & Barriga 2002;Ferreira et al. 2012;Casatti et al. 2015). ...
Deforestation is a primary driver of biodiversity change through habitat loss and fragmentation. Stream biodiversity may not respond to deforestation in a simple linear relationship. Rather, threshold responses to extent and timing of deforestation may occur. Identification of critical deforestation thresholds is needed for effective conservation and management. We tested for threshold responses of fish species and functional groups to degree of watershed and riparian zone deforestation and time since impact in 75 streams in the western Brazilian Amazon. We used remote sensing to assess deforestation from 1984 to 2011. Fish assemblages were sampled with seines and dip nets in a standardized manner. Fish species (n = 84) were classified into 20 functional groups based on ecomorphological traits associated with habitat use, feeding, and locomotion. Threshold responses were quantified using threshold indicator taxa analysis. Negative threshold responses to deforestation were common and consistently occurred at very low levels of deforestation (<20%) and soon after impact (<10 years). Sensitive species were functionally unique and associated with complex habitats and structures of allochthonous origin found in forested watersheds. Positive threshold responses of species were less common and generally occurred at >70% deforestation and >10 years after impact. Findings were similar at the community level for both taxonomic and functional analyses. Because most negative threshold responses occurred at low levels of deforestation and soon after impact, even minimal change is expected to negatively affect biodiversity. Delayed positive threshold responses to extreme deforestation by a few species do not offset the loss of sensitive taxa and likely contribute to biotic homogenization.
... Higher abundance and/or diversity of biotic communities, as evident here, can also be associated with habitat heterogeneity driven by LW presence (Wright & Flecker, 2004;Lester & Boulton, 2008;Pilotto et al. 2014;. However, such biotic responses are not ubiquitous, with a synthesis of restoration studies, albeit primarily with wood absent, largely failing to increase biodiversity following habitat diversification (Pretty et al. 2003;Palmer et al. 2010). ...
River systems are under pressure from anthropogenic influences which both degrade habitat, through modification and pollution, and threaten biodiversity. Mitigation of impacts and recovery of natural states, reversing inadequate hard engineering, is of paramount importance. Rewilding offers a holistic approach to ecological recovery, targeting totipotent and naturally functioning habitats of native components. However, attempts at restoring these ecosystems are compounded by a dearth of standardised, larger-scaled and adequately-appraised projects which can detect ecological response and inform wider prediction. Multiple Before-After-Control-Impact (MBACI) designs provide greater spatiotemporal coverage capable of detangling human impacts from natural variation.
Large wood (LW) is a natural characteristic of riparian forested rivers, considered vital for habitat complexity and biodiversity and has thus gained recent popularity in river restoration. In addition, aquatic macrophytes occupy a crucial role as ecosystem engineers, maintaining key ecological functions, whilst providing good bioindicators of restoration success. However, study of LW effects on macrophyte response had not been undertaken. An MBACI design was applied to LW restoration on five chalk streams, sampled before and after at control, impact (felled LW) and reference (natural LW) sites to test restoration effects on macrophytes. A combination of spatially nested scales (stream-reach-habitat), macrophyte structural measures (α-diversity, abundance and size parameters) and environmental determinants (LW, substrate and water depth) were tested in order to quantifiably assess the ecological impact of restoration.
LW presence impacted both substrate and macrophyte community structure at the meso-scale. Significant positive correlation and explanation of variance was evident for silt cover as well as α-diversity and size parameters of macrophytes which increased in LW habitat, for both natural (Reference) and experimental (Impact) LW variants. Equivalent links, and potential feedback, existed between silt cover and macrophyte parameters. Reaches were otherwise largely similar, with insignificant differences for most environmental and macrophyte parameters pre- and post-restoration. Conversely, significant differences characterised antecedent conditions between streams. Macrophyte parameter values were initially highest on Hampshire streams, suggestive of large-scale drivers of variability. However, rivers in which LW explained significant variance in more plant parameters, increased to peak macrophyte values post-restoration, mainly in Norfolk.
Initial conclusions are promising, particularly for ecological improvements at the meso-scale. Detangling LW effects from other drivers will be necessary to assess impacts on macrophytes at larger scales, providing impetus for future study, especially given the low-costs and wider ecological benefits associated with rewilding, and the pressing need for further contributions to the river restoration discipline.
... Desde esta perspectiva, muchos autores consideran que los efectos de las modificaciones en el ámbito regional pueden ser más importantes para los ríos que los efectos de perturbaciones locales como la contaminación orgánica o química (Hughes et al., 1990;Roth et al., 1996;Lammert y Allan, 1999;Karwan et al., 2001;Allan et al., 2002;Wrigt y Flecker, 2004). Esta concepción ha sido determinante para que la cuenca hidrográfica sea considerada como la unidad geográfica e hidrológica de integración de los diferentes procesos que afectan la condición ecológica de los ambientes fluviales (Naiman, 1992). ...
Algunos ecosistemas son estratégicos por su dinámica de regulación hídrica local y regional, entre ellos se encuentra el Páramo. Este es un ecosistema con alta diversidad biológica y capacidad de captación de agua, por lo cual su mayor servicio ambiental es la oferta de agua. No obstante, alteraciones de diferente índole amenazan el estado de conservación de los páramos venezolanos y por ende el de los sistemas fluviales presentes en él, en consecuencia la estructura y funcionamiento de la biota acuática se ven afectados.
Existen diferentes maneras de cuantificar el grado de afectación de los ecosistemas fluviales, una de ellas es a través de la macrofauna de invertebrados bentónicos. Los Índices Bióticos Integrados (multimétricos) o IBI, emplean los atributos o métricas de este ensamblaje de la fauna, que responden ante las perturbaciones. Los IBI se basan en el concepto de Integridad biótica, la cual operativamente se puede considerar como el extremo óptimo de un gradiente que se extiende desde los más bajos hasta los más altos niveles de calidad biológica. Estos permiten evaluar que tan lejos o cerca se encuentra un ecosistema de su Integridad Biótica, a partir de la comparación de elementos representativos de la biota de sitios impactados, con los mismos elementos presentes en la biota de sitios referenciales con ninguna o poca intervención.
En función de la situación de deterioro en que se encuentra el páramo en la cuenca alta del río Chama en la Cordillera de Mérida, y su importancia como proveedor de agua, nos planteamos desarrollar un IBI para evaluar la condición biológica y el estado ecológico de los ríos y quebradas de la zona. Para ello obtuvimos información cuantitativa y cualitativa en campo sobre la comunidad de macroinvertebrados bentónicos y las variables fisicoquímicas, hidromorfológicas y de hábitat interno y externo al cauce de los ríos de la zona en 60 sitios durante un ciclo anual. Esta información permitió, caracterizar biológica y ambientalmente los sitios bajo estudio. Analizamos la existencia de gradientes ambientales naturales y debidos al impacto antrópico, a través del uso de herramientas de análisis multivariado y univariado. Encontramos que existen tres gradientes ambientales marcados: uno de condiciones hidromorfológicas, otro de condiciones fisicoquímicas, que varió según la estacionalidad de las precipitaciones, y un tercero que corresponde con la altitud y calidad del hábitat fluvial y ribereño.
La caracterización biológica de los sitios revelo que la macrofauna bentónica, dominada por insectos y oligoquetos, respondió al gradiente altitudinal de calidad ambiental, con variaciones en la abundancia y composición de sus taxa. Estas no presentaron cambios debidos a la estacionalidad de las precipitaciones.
Posteriormente, el IBI fue construido a partir de un conjunto de métricas biológicas indicadoras que respondieron consistentemente a variaciones del impacto antrópico. Estas fueron examinadas por medio del análisis de los percentiles de su distribución en sitios con mínimo impacto antrópico o sitios de referencia, y sitios bajo distintos niveles de intervención. La composición de dicho conjunto de métricas fue variable de acuerdo con la época del año. Finalmente, el IBI con un alto nivel de eficacia, permitió concluir que alrededor de un 65% de los sitios de los ríos estudiados se encuentran bajo un nivel de intervención Grave a Muy Grave y por tanto con en una condición biológica Pobre a Muy Pobre. El porcentaje restante varía entre las categorías de condición biológica Buena a Muy Buena. Los sitios con la mejor condición biológica se encuentran hacia las zonas más elevadas de la cuenca en donde el nivel de intervención es Mínimo o Leve.
Se requiere con urgencia la acción conjunta de los distintos actores afectados directa o potencialmente por este estado de deterioro del ecosistema, para la promoción y aplicación de acciones capaces de frenar y mitigar el mismo. A nivel agrícola la alternativa es la adopción de un modelo de producción agroecológico que resulte más amigable con el ambiente que el modelo productivo empleado en la actualidad. A través de campañas de educación ambiental se podría incentivar el uso racional del recurso agua, asegurando en el futuro el acceso al mismo.
... The hyporheic exchange zone can also be affected by large woody debris that play an important role in macroinvertebrate and fish habitats (Angermeier and Karr, 1984;Wallace et al., 1995;Abbe and Montgomery, 1996;Wright and Flecker, 2004). Sawyer et al. (2011) developed Cardenas and Wilson's (2007) model to include bed pressure profile and hyporheic exchange rates near the channel-spanning log that can be used to evaluate the impact of large woody debris removal or reintroduction in hyporheic mixing. ...
Computational fluid dynamics (CFD) is defined as a branch of fluid mechanics that solves fluid flow problems using numerical algorithms and methods. Using CFD to model water and contaminants transport in rivers, lakes, and coastal areas can significantly improve our understanding to manage these hydrodynamic systems. In this paper, 111 studies have been reviewed on different aspects of CFD application in ecohydrology that include: flow simulation and pressure distribution, sediment transport, hyporheic zone, fish habitat and temperature distribution. In general, three-dimensional models are reported to be more capable than two-dimensional models to predict flow features and have been used more recently due to their ability to capture secondary flow. Two-dimensional models with secondary flow correction terms are acceptable and are being used as well. Discretization techniques and turbulence closures are also reported with comparisons. In general, majority of the studies were focused on flow and sediment transport; however, our knowledge about temperature distributions in near-bed regions and pool-riffle structures is limited and can be the subject of future studies.
... Modifications in riparian vegetation through logging affect the structure and processes within the peat swamps. It leads to the alteration of the swamp characteristics, reduction of food resources (Tabacchi et al., 1998;Wright & Flecker, 2004) and subsequent loss of biodiversity (Bruenig & Droste, 1995). ...
A review of literature showed that numerous intensive surveys have been carried out on the ichthyofauna of the peat swamp forests (PSFs) of Malaysia. This review was aimed at providing a checklist of black water fish species in Malaysia from available published literature, addressing their economical importance, conservation status and problems of PSFs. A total of 189 peat swamp fish species from 32 families have been recorded from Malaysia. From that, a total of 114 species from 23 families, representing about 40% of the known fish fauna in Peninsular Malaysia was recorded from north Selangor PSF. Meanwhile, totals of 49 species belonging to 18 families, 13 species from seven families, 58 species belonging to 19 families, and nine species from five families were recorded from the peat swamps of Perak, Johor, Pahang and East Peninsular Malaysia (part of Pahang and Terengganu) respectively. Thirty-one species from 12 families and 40 species belonging to 13 families were recorded from Sabah and Sarawak respectively. Family Cyprinidae has the highest recorded species, followed with Osphronemidae, Bagridae and Siluridae. The IUCN Red List revealed 12 threatened species facing risk of extinction. The importance of conserving PSFs was outlined and suggestions made in line with the objectives of conservation. Findings from literature revealed that the Malaysia PSFs are rich in fish diversity contrary to previous belief, and should be conserved and protected to ensure the richness of their fish diversity.
A revision of the genus Salminus, excluding the large-sized species S. brasiliensis and S. franciscanus, is presented. In addition to the two large-sized species, four additional Salminus species are recognized: Salminus affinis Steindachner, from the río Magdalena, río Sinú, and río Rancheria basins, Colombia; Salminus hilarii Valenciennes, from the rio Paraná, rio São Francisco, and rio Jaguaribe basins, Brazil, Argentina, and Paraguay; Salminus iquitensis (Nakashima), new combination, from the western portion of the Amazon basin, rio Branco, and río Orinoco basins, Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela; and Salminus santosi new species, from the rio Tocantins basin, Brazil. These four species are described/redescribed and illustrated, and a key to the species belonging to the genus is presented. Comments on the diagnosis of the genus Salminus and its biogeography taking into account recent phylogenetic hypotheses published for the genus, are presented.
Freshwater fish are one of the most diverse groups of vertebrates, but are also amongst the most threatened. With contributions from leaders in the field, this is the first assessment of the global state of freshwater fish diversity, synthesising the opportunities, challenges and barriers facing the conservation of freshwater fish biodiversity. The book includes the first global assessment of the number, type and distribution of threatened freshwater fish species, discussing the features of freshwater fish biology and ecology that render so many species vulnerable to extinction. Introductory chapters on why freshwater fish are so sensitive to environmental change and disturbance lead into chapters providing detailed reviews of the key threatening processes and potential solutions. A concluding chapter summarises the key issues and looks to the future for opportunities and challenges for the conservation and management of freshwater fish.
Freshwater fish are one of the most diverse groups of vertebrates, but are also amongst the most threatened. With contributions from leaders in the field, this is the first assessment of the global state of freshwater fish diversity, synthesising the opportunities, challenges and barriers facing the conservation of freshwater fish biodiversity. The book includes the first global assessment of the number, type and distribution of threatened freshwater fish species, discussing the features of freshwater fish biology and ecology that render so many species vulnerable to extinction. Introductory chapters on why freshwater fish are so sensitive to environmental change and disturbance lead into chapters providing detailed reviews of the key threatening processes and potential solutions. A concluding chapter summarises the key issues and looks to the future for opportunities and challenges for the conservation and management of freshwater fish.
Freshwater fish are one of the most diverse groups of vertebrates, but are also amongst the most threatened. With contributions from leaders in the field, this is the first assessment of the global state of freshwater fish diversity, synthesising the opportunities, challenges and barriers facing the conservation of freshwater fish biodiversity. The book includes the first global assessment of the number, type and distribution of threatened freshwater fish species, discussing the features of freshwater fish biology and ecology that render so many species vulnerable to extinction. Introductory chapters on why freshwater fish are so sensitive to environmental change and disturbance lead into chapters providing detailed reviews of the key threatening processes and potential solutions. A concluding chapter summarises the key issues and looks to the future for opportunities and challenges for the conservation and management of freshwater fish.
Freshwater fish are one of the most diverse groups of vertebrates, but are also amongst the most threatened. With contributions from leaders in the field, this is the first assessment of the global state of freshwater fish diversity, synthesising the opportunities, challenges and barriers facing the conservation of freshwater fish biodiversity. The book includes the first global assessment of the number, type and distribution of threatened freshwater fish species, discussing the features of freshwater fish biology and ecology that render so many species vulnerable to extinction. Introductory chapters on why freshwater fish are so sensitive to environmental change and disturbance lead into chapters providing detailed reviews of the key threatening processes and potential solutions. A concluding chapter summarises the key issues and looks to the future for opportunities and challenges for the conservation and management of freshwater fish.
Freshwater fish are one of the most diverse groups of vertebrates, but are also amongst the most threatened. With contributions from leaders in the field, this is the first assessment of the global state of freshwater fish diversity, synthesising the opportunities, challenges and barriers facing the conservation of freshwater fish biodiversity. The book includes the first global assessment of the number, type and distribution of threatened freshwater fish species, discussing the features of freshwater fish biology and ecology that render so many species vulnerable to extinction. Introductory chapters on why freshwater fish are so sensitive to environmental change and disturbance lead into chapters providing detailed reviews of the key threatening processes and potential solutions. A concluding chapter summarises the key issues and looks to the future for opportunities and challenges for the conservation and management of freshwater fish.
Freshwater fish are one of the most diverse groups of vertebrates, but are also amongst the most threatened. With contributions from leaders in the field, this is the first assessment of the global state of freshwater fish diversity, synthesising the opportunities, challenges and barriers facing the conservation of freshwater fish biodiversity. The book includes the first global assessment of the number, type and distribution of threatened freshwater fish species, discussing the features of freshwater fish biology and ecology that render so many species vulnerable to extinction. Introductory chapters on why freshwater fish are so sensitive to environmental change and disturbance lead into chapters providing detailed reviews of the key threatening processes and potential solutions. A concluding chapter summarises the key issues and looks to the future for opportunities and challenges for the conservation and management of freshwater fish.
Freshwater fish are one of the most diverse groups of vertebrates, but are also amongst the most threatened. With contributions from leaders in the field, this is the first assessment of the global state of freshwater fish diversity, synthesising the opportunities, challenges and barriers facing the conservation of freshwater fish biodiversity. The book includes the first global assessment of the number, type and distribution of threatened freshwater fish species, discussing the features of freshwater fish biology and ecology that render so many species vulnerable to extinction. Introductory chapters on why freshwater fish are so sensitive to environmental change and disturbance lead into chapters providing detailed reviews of the key threatening processes and potential solutions. A concluding chapter summarises the key issues and looks to the future for opportunities and challenges for the conservation and management of freshwater fish.
Freshwater fish are one of the most diverse groups of vertebrates, but are also amongst the most threatened. With contributions from leaders in the field, this is the first assessment of the global state of freshwater fish diversity, synthesising the opportunities, challenges and barriers facing the conservation of freshwater fish biodiversity. The book includes the first global assessment of the number, type and distribution of threatened freshwater fish species, discussing the features of freshwater fish biology and ecology that render so many species vulnerable to extinction. Introductory chapters on why freshwater fish are so sensitive to environmental change and disturbance lead into chapters providing detailed reviews of the key threatening processes and potential solutions. A concluding chapter summarises the key issues and looks to the future for opportunities and challenges for the conservation and management of freshwater fish.
The city of Manaus has been growing in an accelerated and disorderly way, which causes
the fragmentation of the forest and condemns the urban streams to disappearance. Along with these streams, an important part of the local aquatic biodiversity is lost, even before it is properly known. In this context, fish assemblages from streams of 52 urban forest fragments were studied, in addition to laboratory experiments, aiming to evaluate the effects of forest fragmentation and of alteration in structural and limnological characteristics of streams (pollution) on the composition and diversity of fish assemblages. Sixty-eight fish species from seven orders and 14 families were collected. Richness ranged from one to 14 species per 50-m stream stretch. Streams subjected to anthropic impacts showed changes both in structural and limnological parameters, as
well as in the composition and structure of fish assemblages. Streams in a good state of
conservation showed higher species richness, associated with high values of dissolved oxygen and low values of electrical conductivity and pH, and the opposite situation was recorded in polluted streams. The species richness per stream (1-14 species) was small in relation to the total richness found (68 species), indicating a high regional diversity. The similarity in fish species composition varied with the degree of environmental integrity of the streams. Well-preserved streams presented richer and more diverse assemblages, while heavily degraded streams presented assemblages with few species and more similar to each other. Differences in the original environmental characteristics of the streams, as well as the subsequent isolation of fish populations by chemical barriers (highly polluted stream tretches among forest fragments) may be responsible for the current differences in species composition in nearby streams. Laboratory experiments showed that water quality affects agonistic interactions between three cichlid species
(Aequidens pallidus; native; Cichlasoma amazonarum, non-native and allochthonous; and
Oreochromis niloticus, non-native and exotic). In general, agonistic interactions decreased
between species in polluted water when compared to interactions in clean water, and this
reduction was especially intense in the native species A. pallidus. In polluted waters there were weak interspecific interactions between species when analyzed in mixed groups of two species at a time, but there were strong intraspecific interactions in the three species, both in monospecific and mixed groups. These results indicate that water quality modulates the agonistic interactions of the studies cichlid species and may play an important role in the process of replacing native species with non-native ones in the urban streams of Manaus. The set of results obtained in this thesis indicate that the conservation of forest remnants in the urban area of Manaus is essential for the maintenance of the local diversity of stream fishes, and that the loss of any fragment can
result in the local extirpation of several fish species, with loss of regional fish diversity. The continuous population growth brings environmental degradation, as well as social and economic disorder for the city of Manaus, because the process of recovery of these areas is much more onerous and takes more time than their conservation. Thus, it is necessary to implement projects for the recovery of urban streams, as well as the implementation of an efficient system for the collection and treatment of the domestic sewage, so avoinding its direct discharge into the streams. Projects to recompose native riparian vegetation would have highly beneficial effects on the environmental recovery of urban streams, on the conservation of local and regional aquatic biodiversity, and on the formation of ecological corridors for fauna and flora, which could feed back the ecological processes of environmental recovery in a regional spatial scale.
We evaluated the beta diversity patterns of aquatic macroinvertebrate assemblages at two spatial scales in streams in the Eastern Amazon, as well as tested whether environmental and spatial factors affected these assemblage patterns differently for non-flying (i.e., shrimps) and flying (i.e., insects) macroinvertebrate groups. Fifteen streams were sampled, focusing on two hierarchical spatial levels: sampling units (length: five meters) and stream sites (length: 150 m). We additively partitioned gamma diversity to test the relative importance of each spatial level to regional diversity. The total beta diversity at each spatial level was decomposed into the components of replacement and abundance difference. To test whether there was an effect of spatial distances and environmental variables on the dissimilarity matrices, we used multiple regression on distance matrices (MRM). Our results showed that: (1) In both macroinvertebrate groups, alpha diversity contributed less than beta diversity, and dissimilarity between stream sites presented a greater contribution to gamma diversity; (2) the decomposition of beta diversity showed similar patterns in both groups and between the two spatial levels, with a greater contribution of abundance difference than replacement; and (3) the MRM models showed that only environmental distance was important to explain beta diversity of insects, while for shrimps both environmental and spatial distances were significant. We conclude that different ecological processes and environmental variables were important to explain the distributions of insects and shrimps, which is probably related to the different dispersal modes and environmental niche requirements.
Substantial amounts of dead wood in the intertidal zone of mature mangrove forests are tunnelled by teredinid bivalves. When the tunnels are exposed, animals are able to use tunnels as refuges. In this study, the effect of teredinid tunnelling upon mangrove forest faunal diversity was investigated. Mangrove wood not containing teredinid tunnels had very few species and abundance of animals. However, with a greater cross-sectional surface area of teredinid tunnels, the numbers of species and abundance of animals was significantly higher. Temperatures within teredinid-attacked wood were significantly cooler compared with air temperatures, and the animals in tunnels inside the wood may avoid desiccation by escaping the higher temperatures. Animals co-existing in teredinid tunnelled wood ranged from animals found in terrestrial ecosystems including centipedes, crickets and spiders, and animals found in subtidal marine ecosystems such as fish, octopods and polychaetes. There was also evidence of breeding within teredinid-attacked wood, as many juvenile individuals were found, and they may also benefit from the cooler wood temperatures. Teredinid tunnelled wood is a key low-tide refuge for cryptic animals, which would otherwise be exposed to piscivorous fishes and birds, and higher external temperatures. This study provides evidence that teredinids are ecosystem engineers and also provides an example of a mechanism whereby mangrove forests support intertidal biodiversity and nurseries through the wood-boring activity of teredinids.
Substantial amounts of dead wood in the intertidal zone of mature mangrove forests are tunnelled by teredinid bivalves. When the tunnels are exposed, animals are able to use tunnels as refuges. In this study, the effect of teredinid tunnelling upon mangrove forest faunal diversity was investigated. Mangrove wood not containing teredinid tunnels had very few species and abundance of animals. However, with a greater cross-sectional surface area of teredinid tunnels, the numbers of species and abundance of animals was significantly higher. Temperatures within teredinid-attacked wood were significantly cooler compared with air temperatures, and the animals in tunnels inside the wood may avoid desiccation by escaping the higher temperatures. Animals co-existing in teredinid tunnelled wood ranged from animals found in terrestrial ecosystems including centipedes, crickets and spiders, and animals found in subtidal marine ecosystems such as fish, octopods and polychaetes. There was also evidence of breeding within teredinid-attacked wood, as many juvenile individuals were found, and they may also benefit from the cooler wood temperatures. Teredinid tunnelled wood is a key low-tide refuge for cryptic animals, which would otherwise be exposed to piscivorous fishes and birds, and higher external temperatures. This study provides evidence that teredinids are ecosystem engineers and also provides an example of a mechanism whereby mangrove forests support intertidal biodiversity and nurseries through the wood-boring activity of teredinids.
Habitat homogenization has been a major impact in stream ecosystems, and it is considered one of the main drivers of biotic homogenization as well, leading to the loss of water quality and fish diversity. In this study, we added artificial woody structures and leaf packs in physically impacted streams to test if the additions can improve habitat complexity and change the taxonomic and functional structure of fish communities. The experiment was done in eight streams impacted by siltation, deforestation, and habitat homogeneization, inserted in an agricultural landscape from the Upper Paraná River Basin, and lasted 112 days. The provision of artificial microhabitats increased instream habitat diversity by creating patches of organic matter deposits, changing flow, and providing substrate for grass colonization of the instream habitat. The experimental manipulation also changed fish species abundance. Nine species contributed to these changes, five decreased and four increased in abundance, indicating species responded differently to the experimental manipulation. However, overall species richness, diversity, and community functional traits remained unaltered. These results indicate that short-term habitat restoration on a local scale may not be enough to promote changes in fish community attributes of streams that are heavily impacted.
A destruição de habitats, promovida pela extração de areia de leitos de riachos, pode causar a perda de algumas espécies e a alteração na dinâmica das assembleias de peixes. Assim, o presente estudo investigou o efeito da extração de areia sobre as assembleias de peixes em riachos de Campinarana, localizados na região de Cruzeiro do Sul, Acre, entre junho a agosto de 2017 e 2018. Seis riachos foram avaliados, sendo três degradados (pela extração de areia) e três florestados. Riqueza, diversidade de Shannon, equitabilidade e abundância de espécies foram avaliadas. Para verificar diferenças entre esses parâmetros, foi realizado o teste t de Student. NMDS e PERMANOVA foram sumarizadas para avaliar a composição de espécies de peixes. Foram coletadas 60 espécies de peixes com 705 indivíduos. Houve uma diferença significativa entre as áreas com relação à riqueza (t = 11,1; p = 0,0001), à abundância (t = 4,5; p = 0,006) e à diversidade (t = 4,1; p = 0,01). A composição de espécies também variou (Pseudo-F = 3,79; p = 0,01), onde 35% das espécies foram restritas aos ambientes preservados. Assim, sugere-se que a perturbação antrópica nas campinaranas, causou perda das espécies mais sensíveis e especializadas, permitindo o aumento dos indivíduos oportunistas, alterando a organização das assembleias e reduzindo a diversidade local.
Freshwater fish are one of the most diverse groups of vertebrates, but are also amongst the most threatened. With contributions from leaders in the field, this is the first assessment of the global state of freshwater fish diversity, synthesising the opportunities, challenges and barriers facing the conservation of freshwater fish biodiversity. The book includes the first global assessment of the number, type and distribution of threatened freshwater fish species, discussing the features of freshwater fish biology and ecology that render so many species vulnerable to extinction. Introductory chapters on why freshwater fish are so sensitive to environmental change and disturbance lead into chapters providing detailed reviews of the key threatening processes and potential solutions. A concluding chapter summarises the key issues and looks to the future for opportunities and challenges for the conservation and management of freshwater fish.
Three pairs of cobble riffle study sites were established in a second-order stream in North Carolina and logs added to the downstream riffle at each site. At log addition transects, stream depth increased, current velocity decreased, cobble substratum was covered by sand and silt, and both coarse and fine paniculate organic matter increased dramatically. Log additions had less dramatic effects on uptake lengths of ammonium, nitrate, and phosphate, but they had immediate,and significant impacts,on invertebrate community,structure: abundances,and biomass of scrapers and filterers decreased; collectors and predators increased; overall shredder,biomass did not change, but biomass of trichopteran and dipteran shredders increased, while that of most plecopteran,shredders decreased; and plecopteran,predators also decreased despite greater abundances,of potential prey. These observations,suggest that physiological,and morpho- behavioral,constraints preclude,many,animals,from,tracking resources among,patches when patches,display very different abiotic conditions. Secondary,production,of scrapers and filterers decreased, whereas that of collectors and predators increased. The shifts in functional group abundances, biomass, and production between reference and debris-dam transects, which differed considerably from those previously reported for low-gradient, sandy-bottom streams, accentuate the importance,of localized abiotic factors in structuring invertebrate communities,within patches. Resume : Trois paires de sites d'etude constitues par des radiers de cailloux ont 6t6 etablies dans
A total fish yield of 85,200 t was realized in the middle and upper Amazon basin in Brazil during 1977, of which 20% was exported from the region. A comparison with yields based on higher exploitation rates in African rivers suggested that the resource was being underexploited as a whole. However, it is hypothesized that even the present yields of the very large species (comprising over a third of the yield) could not be maintained, and managing the fishery on the basis of the present species composition may not be economically feasible. Management on a higher-yield basis would depress the stocks of the larger species. Although this would reduce the cost of management, the feasibility of the strategy would depend on increased commercial values of many smaller species.
Abundance of woody debris was manipulated in a small Illinois stream to determine the importance of this material to fish. When a stream reach was divided along midchannel, and debris was added to one side, but removed from the other, fish and benthic invertebrates were usually more abundant on the side with woody debris than on the cleared side. In further experiments during a low-flow year (1980), debris removal was followed by rapid decreases in water depth and occurrence of benthic organic litter, and increases in current velocity and proportion of sand bottom. These changes were less apparent in unaltered reaches during 1980, and in all reaches during 1981, which was a high-flow year. Artificial debris was colonized by many invertebrates, including chironomids, trichopterans, and ephemeropterans. Most large fish (age 2+) avoided reaches without debris, whereas some smaller fish (such as johnny darter) preferred them; preferences for reach treatments were stronger in 1980 than in 1981. The adaptive significance of associations between fish and woody debris appeared more closely related to the advantages of camouflage than those of increased food availability or protection from strong currents. Extensive removal of woody debris may disrupt structure and function in small streams, especially low-gradient ones. If the biological integrity of stream resources is to be maintained despite agricultural and urban uses, less disruptive management protocols will need to be employed.
Fresh gut contents of the wood-eating loricariid Panaque and a generalized loricariid Liposarcus sp. had enzymatic activity directed against both cellulose and hemicellulose. Aerobic cultures made from the guts of Panaque exhibited growth on a minimal salts medium containing only crystalline cellulose as a carbon source as well as on a variety of other substrates containing carbon polymers found in wood. Anaerobic cultures made from Panaque guts only grew with glucose as a carbon source. Cultures of whole gut contents grown on a yeast extract basal salts medium had significant cellulolytic activity. However, no culture of individual microbes had significant cellulolytic activity, suggesting that any cellulose breakdown which occurs in loricariid guts is by a consortium of micro-organisms. A variety of aerobes, microaerophiles and facultative anaerobes were found in the guts of Panaque; several of these bacteria appear to be new species.
The influence of deforestation on tropical watersheds has received limited study. We compared seven catchments in the Venezuelan Andes to examine variation in the relative extent of forested versus disturbed land and the potential consequences of changing land use on river ecosystems. These watersheds formed a northeast ( Río Acarigua) to southwest ( Río Bumbun) transect and exhibited a gradient in readily observable human settlement and disturbance. Overall, forest cover increased and agriculture and pasture land decreased from the Acarigua to the Bumbun. Human building density and road density showed a parallel trend. Catchments varied in intrinsic characteristics as well. Catchments to the northeast originated at lower elevations and had wider, flatter valleys in the lowest piedmont zone, compared with rivers to the southwest. All seven catchments had broadly similar forest cover at approximately 50–60% within the lowest ( 200–800 m) elevation zone, but they exhibited a strong gradient in the amount of forested versus disturbed land in zones at 800–1400 m and 1400–2600 m. Although the number of buildings was greatest in the 200- to 800-m zone, building density was greater in the 800- to 1400-m zone for the more disturbed catchments, possibly reflecting the areas suitable for coffee production. Land-use change within these catchments is likely to alter hydrology, sediment transport, and habitat conditions within river systems, with adverse consequences for aquatic biodiversity.
Snags are important to fish communities in small rivers and streams, but their importance to fishes in large rivers has not been investigated. This study examined snag use by fishes during autumn in backwater and channel border habitats in the upper Mississippi River, and compared these to fish communities in reference sites without snags. Species assemblages differed significantly between backwater and channel border habitats, and between snag and reference sites within the channel border, likely responding to differences in substrate, depth, and current velocity. In both habitats, average fish biomass and abundance were higher (2 to 50 ) at snag sites than at reference sites, but these differences were significant only for channel border biomass. Fish taxa richness differed between backwater and channel border habitats, but not between snag and reference sites. Most large piscivorous fishes (e.g., Micropterus spp., Stizostedion spp.), several insectivorous fishes (Lepomis macrochirus, Ambloplites rupestris, Minytrema melanops), and a few prey fishes (L. macrochirus, Notropis atherinoides) were significantly more abundant at snag sites than at reference sites, suggesting active selection of snags for foraging or protection. Snag quality, as assessed by a snag rating index, had a direct effect on attracting fish communities with greater biomass, especially within the channel border habitat. These results indicate that snags are important habitat for fish communities in both backwaters and channel border habitats of the upper Mississippi River.
Scenarios of changes in biodiversity for the year 2100 can now be developed based on scenarios of changes in atmospheric carbon
dioxide, climate, vegetation, and land use and the known sensitivity of biodiversity to these changes. This study identified
a ranking of the importance of drivers of change, a ranking of the biomes with respect to expected changes, and the major
sources of uncertainties. For terrestrial ecosystems, land-use change probably will have the largest effect, followed by climate
change, nitrogen deposition, biotic exchange, and elevated carbon dioxide concentration. For freshwater ecosystems, biotic
exchange is much more important. Mediterranean climate and grassland ecosystems likely will experience the greatest proportional
change in biodiversity because of the substantial influence of all drivers of biodiversity change. Northern temperate ecosystems
are estimated to experience the least biodiversity change because major land-use change has already occurred. Plausible changes
in biodiversity in other biomes depend on interactions among the causes of biodiversity change. These interactions represent
one of the largest uncertainties in projections of future biodiversity change.
Driftwood is an important source of habitat and food for the marine ecosystem, including the deep-sea floor. Driftwood, during its seaward journey, is both habitat and food source for many aquatic and terrestrial plants and animals. In addition, some driftwood controls stream velocities, stabilizes stream banks, and creates and protects fish spawning areas. Part I of the book looks at some present-day actions, including damming streams and rivers, which prevent driftwood reaching the sea. Without driftwood, stream channels and coastal sand dunes are destabilized and wood is eliminated from the food chains of estuaries and the deep ocean. In part II the journey taken by water and wood from the mountains to the ocean is described. The story is set prior to the settlement of the Pacific Northwest by Europeans. Part III looks at the collision of European settlement with the environment. Settlement began immediately to affect the waterways and ancient forests of the Pacific Northwest, contributing to current environmental crises. -from Authors
Large Woody Debris (LWD) in running waters provides complex and important habitat for fish communities. Quantifying the structure of LWD should improve the understanding of habitat choice of fish as well as fish habitat management. Therefore, we evaluated the efficiency of techniques to describe physical habitat and fluvial fish community characteristics that are required to quantify fish-habitat relationships for LWD. An open electrofishing technique for 15 minutes with two electrodes captured more than 70 % of the fish through a single removal in a 50 m2 zone. On average only 3.4 % of the fish escaped from the zone during electrofishing. Mean conditions and variability of physical LWD habitat in a sampled zone could be accurately and precisely described with 10 (water depth, current velocity, mineral bottom substrate size) or 20 (LWD variables) point measurements. Partial Least Square (PLS) regressions showed the potential of the LWD sampling procedure to relate fish community characteristics to physical habitat. Fish abundance was significantly related to current velocity, water depth and mineral substrate size, which are traditionally used in studies of fish-habitat relationships. In addition, depending on the species, abundances were significantly related to various LWD variables that characterised density, location, shelter function and structural diversity of LWD.
This revised and updated edition of the bestselling Methods in Stream Ecology reflects the latest advances in the technology associated with ecological assessment of streams. In this second edition, all chapters have been updated and modified to reflect the most contemporary protocols covering 6 vital areas of stream ecology: Physical Stream Ecology; Material Transport, Uptake, and Stora Stream B Community Interactions; Ecosystem Processes; and Ecosystem Quality. Each chapter contains basic methods suitable for teaching undergraduate or graduate students and advanced methods for conducting state-of-the-art research. Suitable as a textbook for a course in stream or river ecology, this book is also a critical reference for professional aquatic ecologists, natural resource managers, and for those entering the field of stream ecology who wish to evaluate the condition of streams or their watersheds.
Removal of all organic debris dams from a 175-m stretch of second-order stream at the Hubbard Brook Experimental Forest in New Hampshire led to a dramatic increase in the export of organic carbon from this ecosystem. Output of dissolved organic carbon (<0.50 @mm) increased 18%. Fine particulate organic carbon (0.50 @mm-1 mm) export increased 632% and coarse particulate organic matter (>1 mm) export increased 138%. Measurement of the standing stock of coarse particulate organic matter on streambeds of the Hubbard Brook Valley revealed that organic debris dams were very important in accumulating this material. In first-order streams, debris dams contain nearly 75% of the standing stock of organic matter. The proportion of organic matter held by dams drops to 58% in second-order streams and to 20% in third-order streams. Organic debris dams, therefore, are extremely important components of the small stream ecosystem. They retain organic matter within the system, thereby allowing it to be processed into finer size fractions in headwater tributaries rather than transported downstream in a coarse particulate form.
An Annual nitrogen budget is presented for a small steam draining Watershed 10, H. J. Andrews Experimental Forest, Oregon. The role of allochthonous debris in the input, flux, and export of nitrogen is emphasized in the material balance budget. All material entering the stream channel was presumed to enter the water sometime during the year. Material estimates are based on total channel area. The major annual nitrogen input (1974-1975) was subsurface flow (11.06 g/m^2) as dissolved organic nitrogen (10.56 g/m^2) and nitrate (0.50 g/m^2).Biological inputs of nitrogen amounted to 4.19 g/m^2 as direct terrestrial inputs of: litterfall (1.35 g/m^2), lateral movement (1.78 g/m^2), and throughfall (0.30 g/m^2). Nitrogen fixation on fine wood debris contributed an additional 0.76 g/m^2 based on rates from a nearby watershed. Total nitrogen input was 15.25 g/m^2. The nitrogen pool was dominated by large amounts of particulate organic matter. Coarse wood constituted 32% of the nitrogen pool (3.80 g/m^2) and fine wood fractions 18% (2.18 g/m^2). The coarse wood fraction greatly influenced stream morphology. Fine organic particulates constituted an additional 40% of the nitrogen pool (4.77 g/m^2). DON (dissolved organic nitrogen) export (8.38 g/m^2) was less than input, presumably due to biological uptake associated with litter mineralization, sorption, and chemical flocculation. Due to effective retention of particulate inputs by debris dams, biological processing in the particulate nitrogen pool, and uptake and sorption of DON, most particulate organic inputs increased in nitrogen concentration prior to export. Particulate organic nitrogen input (3.13 g/m^2) was greater than export (2.53 g/m^2). Total annual nitrogen output was 11.36 g/m^2, resulting in a gain of 3.89 g@?m^-^2@?yr^-^1 to the stream. Thus, the stream was not operating on an annual steady state, but on an input-output regime related to the processing of refractory wood debris and resetting by major storms. Although particulate and dissolved nitrogen loss per hectare was small for the 10-ha watershed, these losses passed through or were accumulated in a pool encompassing <1% of the watershed area. This concentration of N in the stream allowed establishment of a separate ecosystem whose processing efficiency and capabilities for nutrient cycling were related to the retention capacity of the channel and nutrient quality of inputs within the reach.
Four species of armored catfish (Loricariidae) have size-specific depth distributions in a Panamanian stream, with larger fish in deeper water. Depth distributions do not change from the dry to the rainy season, despite a two- to three-fold increase in habitat area for larger loricariids. Throughout the year, standing crops of the loricariids' attached algal food are relatively high in shallow water, but decrease rapidly with depth. Over 2@1 yr, large Ancistrus spinosus, the most common pool-dwelling loricarriid, showed significant seasonal changes in somatic growth rates, with maximum rates in the early rainy season and minimum rates in the late dry season. Significant seasonal changes in mortality rates, estimated from rates of disappearance of marked individuals, were not detected. These data are consistent with the following hypothesis: small loricariids are limited, perhaps by predation, at densities below those necessary to deplete algae in shallow water. Larger loricariids avoid shallow water where they are vulnerable to fishing birds, even in the dry season when food is in short supply in deeper areas.
Habitat and life history are critical elements in assessing the production dynamics of invertebrates and their role in aquatic ecosystems. We studied invertebrate productivity at two sites in a subtropical blackwater river (the Satilla) in the Lower Coastal Plain of Georgia, USA, and found that submerged wooden substrates, or snags, are heavily colonized by aquatic insects. We compared invertebrate productivity on the snag habitat with productivity in the sandy benthic habitat of the main channel, and the muddy benthic habitat of the backwaters. The size-frequency method was applied to individual taxa in order to determine total invertebrate productivity. Emphasis was placed on the importance of the length of larval life, or the cohort production interval, in determining biomass turnover rates. The diversity of taxa was much higher on the snag habitat than in either of the benthic habitats. Filter-feeding caddisflies (especially Hydropsyche spp.) and black flies (Simulium spp.) were the major consumers on the snag habitat. Several species of midges, mayflies, and beetles also were abundant. Total densities, standing stock biomass, and production were very high for primary consumers on snags. Annual production was 51.9 and 67.1 g m-2. yr- I (dry mass per surface area of snag, or effective habitat) for the two sites. Hellgrammites, dragonflies, and stoneflies were the major insect predators colonizing snags, and their production was 5.5 and 5.2 g m-2 yr-t (effective habitat). Annual pro- duction/biomass ratios (P/B) were usually 5-10 for insects that had univoltine or bivoltine life cycles. Annual P/B estimates were very high for midges (> 100) and black flies (>70), since length of larval life was estimated to be very short. The sandy-substrate benthos consisted almost exclusively of very small midges with oligochaetes of lesser abundance. Densities were quite high (>20 000/M2), but biomass was very low (I 100 mg/ m2 or less). Production of primary consumers was >11 g m-2 yr- t with a very high estimate of annual P/B (166-227). The major predators were Ceratopogonidae (biting midges) larvae with an annual production of 1.6-2.6 g.m-2 yr-t. The muddy-substrate benthos consisted primarily of oligochaetes (Limnodrilus) and midges. Annual production was 7-10 g.m-2 yr-t for primary consumers. The major predators were larger Tanypodinae midges. On a substrate surface area basis, standing stock biomass on snags was 20-50 times higher than in the sandy habitat and 5-10 times higher than in the muddy habitat. Production on snags was only 3-4 times higher than production in the benthic habitats, with higher annual P/B in the latter. The production estimates for the snag habitat are among the highest yet reported for lotic ecosystems, and it appears that production on snags is limited by available substrate. Habitat areas per length of shoreline were estimated so that we could approximate relative amounts of biomass and production for a stretch of river. Although the snag habitat accounted for only 6/6% of the effective habitat substrate over a stretch of river, it was responsible for over half of invertebrate biomass, and 15- 16% of production. Taxa within each habitat were categorized to functional feeding groups, and habitat-specific func- tional groupings were evaluated using numbers, biomass, and production. Filtering collectors pre- dominated on snags, and gathering collectors in benthic habitats. When corrected for habitat abun- dance, the distribution of biomass among filtering collectors, gathering collectors, and predators was very close. However, the distribution of production was 12% filtering collectors, 71% gathering collectors, and 17% predators. We suggest that production is the most meaningful parameter to consider in functional group analysis and that the use of numbers or biomass alone can sometimes result in misleading conclusions. As a middle order (5th-6th) stream, the distribution of production or biomass among functional groups in the Satilla River differs considerably from that predicted by the river continuum concept, predicting a high percentage of grazing consumers.
This paper reviews the form, function, and management of woody debris in streams, and reaches three major conclusions: (1) Large woody debris enhances the quality of fish habitat in all sizes of stream. Removal of most trees in the riparian zone during logging, combined with thorough stream cleaning and short-rotation timber harvest, h as altered the sources, delivery mechanisms, and redis- tribution of debris in drainage systems, leading to changes in fish population abundance and species composition. (3) There is an urgent need for controlled field experiments and long-term studies t hat focus on the protection of existing large woody debris in stream channels and the recruitment of new debris from the s urrounding forest. logjams that could block river navigation, water-based log transport, and the upstream passage of salmon and trout on their way to spawning grounds, but is now understood to play an important role in the crea- tion and maintenance of fish habitat throughout entire rivers. Although wood itself eventually enters the food web of the stream ecosystem as it gradually decays, the major importance of debris lies in its structural characteristics and the way these features influence channel hydraulics. Physical processes associated with debris in streams include the forma- tion of pools and other important rearing areas, control of sediment and organic matter storage, and modification of water quality. Biological properties of debris-created structures can include blockages to fish migration, provision of cover from predators and from high streamflow, and maintenance of organic matter processing sites within the benthic community. The locations and principal roles of woody debris change throughout the river system. In steep headwater streams where logs span the channel, debris creates a stepped longitudinal profile that governs the storage and release of sediment and detritus, a function that facilitates the biological processing of organic inputs from the surrounding forest, When the stream channel becomes too wide for spanning by large logs, debris is deposited along the channel margins, where it often forms the most productive fish habitat in main-stem rivers. In all but the smallest streams there is some degree of clump- ing, although the size and spacing of debris clumps generally increase in a downstream direction, Debris-related fish habitat can be found anywhere in small forested streams. In large rivers it is primarily Woody debris h as long been considered a potential source of
Coho salmon fry (Oncorhynchus kisutch) and steelhead parr (O. mykiss) occupied previously infrequently-used mid-channel areas of Kloiya Creek, British Columbia, Canada, once artificial rootwads were placed there. Ninetynine percent of all coho salmon fry and 83% of steelhead parr occupied positions downstream of natural or artificial rootwads during artificially created drought, normal, and flood streamflows. Fish associated with rootwads regardless of distance from shore, but steelhead parr preferred rootwads away from shore while coho salmon fry preferred rootwads next to shore. Coho salmon fry increased their use of natural rootwads where currents were slow during floods, while steelhead parr increased their use of artificial and natural rootwads where light remained low during droughts. Young fish apparently selected areas having slower water 80% of the time because they provided shelter from adverse current, and areas having reduced light intensities 20% of the time because they provided protection from predators, juvenile coho salmon and steelhead in Kloiya Creek selected locations with slower water velocities and reduced light intensities irrespective of the physical structure that caused them.
We examined the relationships of timber harvest, stream habitat complexity, and diversity of juvenile anadromous salmonid assemblages in 14 small- to intermediate-sized basins in coastal Oregon between 1985 and 1989. Diversity (the inverse of a species dominance index) of assemblages in streams in basins with low harvest levels (25% of the basin area harvested) (P = 0.02). Assemblages in basins with high levels of harvest were more dominated by a single species than were assemblages in basins with low harvest. Percent of basin harvested was more strongly associated with assemblage diversity (P = 0.07) than were basin area (P = 0.90) or gradient (P = 0.22) when the influence of the other two factors was controlled. Habitat features were compared between three pairs of streams. Streams in basins with low timber harvest had more complex habitat, as manifested by more large pieces of wood per 100 m (P < 0.01). We conclude that a community and basin-level perspective is necessary to fully assess the effects of timber harvest and other human activities on stream fish.
Small low gradient meandering streams may not have the competency to redistribute the debris. In larger streams flowing water may move large organic debris, concentrating it into distinct accumulations (debris jams). Organic debris may increase or decrease stability of stream banks; influence development of midchannel bars and short braided reaches; and facilitate development of meander cutoffs. In small to intermediate size mountain streams with steep valley walls and little or no floodplain or flat valley floor, large organic debris jams may locally accelerate or retard channel bed and bank erosion and/or deposition; create sites for significant sediment storage; and produce a stepped channel profile which provides for variable channel morphology and flow conditions. - from Authors
SUMMARY 1. There is little information on the impacts of deforestation on the fish fauna in neotropical streams, and on parameters influencing species diversity and community structure of fish. We analysed these aspects in 12 stream sites in the Ecuadorian Amazon. The stream sites represented a large gradient in canopy cover and were located in an area of fragmented forest. While some streams had been deforested, they had not suffered gross degradation of the habitat.
2. The species richness of stream fish was not related to deforestation. Local fish diversity (Fisher's Alpha) was positively related to the surface area of stream pools (m2). Beta diversity was higher among forested than deforested sites, indicating greater heterogeneity in species composition among forested than deforested sites. The percentage of rare species was positively correlated with canopy cover.
3. Total fish density increased with deforestation, and the fish community changed from dominance by omnivorous and insectivorous Characiformes at forested sites to dominance of periphyton-feeding loricariids at deforested sites.
4. Multidimensional statistical analysis of fish community structure showed that six environmental variables (the area of stream bottom covered by leaves, relative pool area, particulate organic matter, mean depth, conductivity and suspended solids) were related to the ordination axes. The presence of leaves, which was strongly correlated to canopy cover, was the variable most closely related to fish community structure, while relative pool area was the second strongest variable. Thus, fish community structure was strongly affected by deforestation.
Species richness is a fundamental measurement of community and regional diversity, and it underlies many ecological models and conservation strategies. In spite of its importance, ecologists have not always appreciated the effects of abundance and sampling effort on richness measures and comparisons. We survey a series of common pitfalls in quantifying and comparing taxon richness. These pitfalls can be largely avoided by using accumulation and rarefaction curves, which may be based on either individuals or samples. These taxon sampling curves contain the basic information for valid richness comparisons, including category–subcategory ratios (species-to-genus and species-to-individual ratios). Rarefaction methods – both sample-based and individual-based – allow for meaningful standardization and comparison of datasets. Standardizing data sets by area or sampling effort may produce very different results compared to standardizing by number of individuals collected, and it is not always clear which measure of diversity is more appropriate. Asymptotic richness estimators provide lower-bound estimates for taxon-rich groups such as tropical arthropods, in which observed richness rarely reaches an asymptote, despite intensive sampling. Recent examples of diversity studies of tropical trees, stream invertebrates, and herbaceous plants emphasize the importance of carefully quantifying species richness using taxon sampling curves.
Trophic interactions, including “top-down” predator-prey interactions, are particularly important in influencing the structure of fish communities. While the varied impacts of piscivorous fish have been well investigated, the effects of fish-eating birds on riverine fish behaviour and population dynamics still remain controversial, mainly because they are undervalued. Summer experiments were conducted in an experimental outdoor stream to evaluate the effects of avian predation threat, stream flow, and overhead cover on growth and behavioural tactics of wild juvenile chub (Leuciscus cephalus). Groups of fifteen chub maintained in riffle-pool sequences were submitted to combinations of different conditions, namely absence or presence of a simulated fish-eating bird, low or high flow, and absence or presence of medium or high cover. In the absence of predation threat, chub foraged in the riffles and maximized feeding opportunities. Under predation threat, they sheltered, foraged less and grew slowly and as expected, they increased their use of the riffles at high flow as water turbulence is an efficient shelter from birds but only in the absence of cover. In the presence of cover, fish sheltered exclusively under pool covers and were more prone to take risks at low flow because of higher costs in terms of lost feeding opportunities associated with these conditions. This result indicates that flow velocity altered cover use tactics through its impact on food supply, suggesting that it may affect the outcome of predator-prey relationships. So, chub use cover in a flexible manner according to both the benefits in terms of predator avoidance and the costs in terms of lost feeding opportunities. A striking finding of the experiments is the drastic reduction in the range of growth variances amongst fish when they are maintained under predation threat, suggesting a homogenization of fitness between individuals. From all our results, we argue that in lowland streams, under summer field situations, fish-eating birds may affect local prey population dynamics more through sub-lethal effects on growth rates than directly through death rates.
The shape of a river channel is linked to surrounding land use through interacting hydrologic and geologic processes. This study analyzes the relationship between the change in near-stream land use and the shape of the adjacent river channel over time. Three watersheds in the foothills of the Venezuelan Andes that have experienced differing degrees of development were studied to determine river channel width, sinuosity, and position relative to surrounding land use. Change in land use over time was obtained from multiple-date aerial photographs (1946 and 1980) referenced to 1996 Landsat Thematic Mapper (TM) satellite imagery, and verified by field inspection. Measurements of land-use type and amount and river channel morphology from the two dates were made using geographic information system (GIS) methods. The three watersheds differed in the extent of deforestation, the location of remaining forested land, and how much land-use change had already occurred by 1946. Change in river channel morphology was greatest at the most deforested sites. Valley shape and channel constraint also had a discernible effect on change in channel morphology. This study introduces a method for analyzing change in coupled terrestrial-aquatic systems based on multiple-date, remotely sensed data and GIS analysis of spatial properties. The results document human impacts on river channels through a comparison of multiple watersheds over a 35-year time interval.
This study demonstrates experimentally that coarse woody debris (CWD) can provide refuge from predation in aquatic habitats. In the Rhode River subestuary of Chesapeake Bay, Maryland, (USA), we (1) measured the abundance of CWD, (2) examined the utilization of CWD by mobile epibenthic fish and crustaceans, and (3) tested experimentally the value of CWD as a refuge from predation. CWD was the dominant above-bottom physical structure in shallow water, ranging in size from small branches (50 cm diameter). In response to experimental additions of CWD, densities of common epibenthic cpecies (Callinectes sapidus, Fundulus heteroclitus, Fundulus majalis, Gobiosoma bosc, Gobiesox strumosus, Palaemonetes pugio, and Rithropanopeus harrisii) increased significantly compared to control sites without CWD. In laboratory experiments, grass shrimp (P. pugio) responded to predatory fish (F. heteroclitus and Micropogonias undulatus) by utilizing shelter at CWD more frequently than in absence of fish. Access to CWD increased survivorship of grass shrimp in laboratory and field experiments. These experimental results (1) support the hypothesis, commonly proposed but untested for freshwater habitats, that CWD can provide a refuge from predation for epibenthic fish and invertebrates and (2) extend the recognized functional importance of CWD in freshwater to estuarine and marine communities. We hypothesize that CWD is an especially important refuge habitat in the many estuarine and freshwater systems for which alternative physical structure (e.g., vegetation or oyster reefs) are absent or in low abundance.
BACI (Before/After and Control/Impact) sampling is widely used in investigations of environmental impacts on mean abundance of a population. The principle is that an anthroppogenic disturbance in the “impact” location will cause a different pattern of change from before to after it starts compared with natural change in the control location. This can be detectable efficiently as a statistical interaction in an analysis of variance of the data. Usually, samples are taken at replicated, random intervals of time before and after the putative impact starts; this ensures that chance temporal fluctuations in either location do not confound the detection of an impact. These designs are, however, insufficient because any location-specific temporal difference that occurs between the two locations will be interpreted as an impact even if it has nothing to do with the human disturbance. Alternatively, abundance in the single control location may change in the same direction, cancelling the effects of an impact. Here, asymmetrical designs are developed that compare the temporal change in a potentially impacted location with those in a randomly-selected set of control locations. An impact must cause a different temporal change in the disturbed location from what would be expected in similar locations. This can be detected for short-term (pulse) or long-term (press) impacts by different patterns of sigficance in the temporal interactions between of sampling and locations. Frolm these novel designs, tests are that demonstrate whether an usual pattern of temporal change in abundance of organisms is specific to the supposedly impacted location and correlated with the onset of the disturbance. Examples are presented of how to use these designs to detect impacts at different spatial scales. Other aspects of their use are discussed.
Prochilodus mariae (Characiformes: Prochilodontidae) is a detritivorous fish distributed throughout the Orinoco river basin of South America. Spectacular migrations of these fishes occur at the end of the rainy season into the Andean foothills. Prochilodus ingest large quantities of sediments and may thereby modify habitats in neotropical streams. The major objectives of this study were (1) to explore experimentally the importance of Prochilodus in structuring a tropical stream in the Venezuelan Andean piedmont, and (2) to determine whether there was sufficient ecological redundancy in a diverse and abundant assemblage of epibenthic fishes to compensate for the removal of Prochilodus. Community structure was compared among three experimental treatments: (1) Prochilodus exclusion, (2) Prochilodus enclosure, and (3) the natural fish assemblage. Selective exclusion of Prochilodus resulted in striking changes in community structure as measured by patterns of sediment accrual and the composition of algal and invertebrate assemblages. Highly significant increases in total dry mass and in ash-free dry mass of sediments accruing on stream-bottom substrates were observed almost immediately following the exclusion of Prochilodus. Moreover the composition of algal and invertebrate assemblages was significantly modified by Prochilodus. Taxa such as diatoms were reduced in number when Prochilodus was present; in contrast, Prochilodus appeared to facilitate nitrogen-fixing cyanobacteria. Total invertebrate densities were greatest in the Prochilodus removal treatment; however, a variety of responses to the experimental treatments was observed among different taxa analyzed individually, including density reductions, increases, and no measurable effects. This study suggests that the detritivore Prochilodus is a functionally dominant species in Andean foothill streams via sediment-processing activities. Moreover, it provides little evidence to support the notion that strongly interacting species are limited to simple systems with few food web components.
"Proyecto: Estudio de manejo Anbiental de la Región Guanare Masparro" Incluye bibliografía
Preface Acknowledgements Part I: Introduction: 1. Introduction Part II. Freshwater Studies: 2. The African fish fauna 3. Man-made lakes 4. Lacustrine fish communities in the Great lakes of eastern Africa 5. Speciation: the African Great lakes as laboratories of evolution 6. The Neotropical fish fauna 7. Far Eastern freshwater fish faunas and their distributions Part III. Marine Fish Studies: 8. Underwater observations: coral reef fishes 9. Demersal fish studies 10. Pelagic fishes Part IV. Syntheses: 11. Responses of fishes to conditions in tropical waters 12. Trophic interrelationships 13. Diversity: its maintenance and evolution 14. The exploitation and conservation of tropical fish stocks Appendix References Index.
The Charciform fishes of the Apure River drainage