Article

Living under stressful conditions: Fish life history strategies across environmental gradients in estuaries

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  • Marine and Environmental Sciences Centre, University of Lisbon, Portugal
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The life history strategies of fishes can be defined by specific combinations of demographic traits that influence species performances depending on environmental features. Hence, the constraints imposed by the local conditions restrict the range of successful strategies by excluding species poorly adapted. In the present study, we compared the demographic strategies of fish caught in 47 estuaries of the North East Atlantic coast, aiming to determine the specific attributes of resident species and test for changes in trait associations along the environmental gradients. Eight demographic traits were considered to project our findings within a conceptual triangular model, composed on three endpoint strategies: (i) periodic (large size, long generation time, high fecundity); (ii) opportunistic (small size, short generation time, high reproductive effort); and (iii) equilibrium (low fecundity, large egg size, parental care). We demonstrated that various life history strategies co-exist in estuaries, but equilibrium species were scarce and restricted to euhaline open-water. Resident species form a specialised assemblage adapted to high spatiotemporal variability of estuarine conditions, i.e. opportunistic attributes associated with parental care. Even with these singular attributes, our findings revealed changes in distribution of resident species across the estuarine gradients linked to their life history traits. Among other patterns, the diversity of life history strategies significantly decreased from euhaline to oligohaline areas and along gradient of human disturbances. These trends were associated with a convergence of species traits toward short generation times, suggesting that long-lived species with late maturation are more severely impacted by disturbance and environmental stress.
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... Such analyses provide information on the functioning and structure of fish communities and their ecosystems (Elliott et al., 2007). It is often assumed that estuarine residents, which rely on estuarine habitats throughout their ontogeny, are most sensitive to habitat degradation and that their response to environmental change reflects local conditions (e.g., Harrison & Whitfield, 2021;Teichert et al., 2017). However, the differential use of shallow coastal and estuarine habitats by different guilds means that any changes to these habitats will have different impacts on each guild, resulting in different effects on performance of individual fish and fish population dynamics. ...
... Different guilds are often associated with particular life histories. For example, many estuarine residents produce relatively large demersal eggs to prevent seaward flushing, whereas marine estuarinedependent species primarily produce many small pelagic eggs adapted for dispersal to nursery grounds (Franco et al., 2008;Teichert et al., 2017). Furthermore, marine estuarine-dependent species are more frequently associated with a large body size and longer life spans compared to estuarine residents (Teichert et al., 2017). ...
... For example, many estuarine residents produce relatively large demersal eggs to prevent seaward flushing, whereas marine estuarinedependent species primarily produce many small pelagic eggs adapted for dispersal to nursery grounds (Franco et al., 2008;Teichert et al., 2017). Furthermore, marine estuarine-dependent species are more frequently associated with a large body size and longer life spans compared to estuarine residents (Teichert et al., 2017). Lifehistory traits, such as maximum body size and parental care, strongly impact population dynamics (Savage et al., 2004) and therefore the guild-specific responses to environmental change. ...
Article
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Shallow coastal and estuarine habitats play an essential role in the life cycles of many fish species, providing spawning, nursery, feeding, and migration areas. However, these ecologically valuable habitats are increasingly threatened by anthropogenic activities, causing substantial changes in both habitat availability and quality. Fish species use these shallow coastal habitats and estuaries during various life stages, leading to their categorization into guilds based on how and when they rely on these areas. This differential functional use of estuaries means that changes to these habitats may affect each guild differently. To understand the impact of estuarine habitat degradation on fish populations, it is therefore necessary to consider the full life cycle of fish and when they rely on these coastal habitats. Here, we use conceptual size‐structured population models to study how estuarine habitat degradation affects two functionally different guilds. We use these models to predict how reduced food productivity in the estuary affects the demographic rates and population dynamics of these groups. Specifically, we model estuarine residents, which complete their entire life cycle in estuaries, and marine estuarine–dependent species, which inhabit estuaries during early life before transitioning offshore. We find that total fish biomass for both guilds decreases with decreasing food productivity. However, the density of juveniles of the marine estuarine–dependent guild can, under certain conditions, increase in the estuary. This occurs due to a shift in the population biomass distribution over different life stages and a simultaneous shift in which life stage is most limited by food. At the individual level, somatic growth of juveniles belonging to the estuarine‐dependent guild decreased with lower food supply in the estuary, due to increased competition for food. The somatic growth rates of fish belonging to the resident guild were largely unaffected by low food supply, as the total fish density decreased at the same time and therefore the per‐capita food availability was similar. These outcomes challenge the assumption that responses to habitat degradation are similar between fish guilds. Our study highlights the need to assess not only fish biomass but also size distributions, survival, and somatic growth rates for a comprehensive understanding of the effects of habitat degradation on fish populations. This understanding is crucial not only for estuary fish communities but also for successful conservation and management of commercially harvested offshore population components.
... The application of this concept was recognised as difficult by Beck et al. (2003) and others (e.g. Kraus & Secor 2003, Heupel et al. 2007, who have made attempts at further clarification of nursery function, especially in terms of effective juvenile habitat (i.e. based on the overall level of contribution of recruits from any given habitat regardless of area coverage) (Dahlgren et al. 2006, Layman et al. 2006, Sheaves et al. 2006 or how selection of alternative juvenile habitats affects overall population fitness (Fodrie et al. 2009, Muller & Strydom 2017 Habitat types follow descriptions in this chapter, geomorphological and hydrological conditions follow Teichert et al. (2017), and physico-chemical variables are modified from Whitfield (2019). Ecological context is included to incorporate a broad ecosystem perspective. ...
... In the tidal portion of estuaries, these shallow intertidal waters can generally support a high abundance of fishes (Boström et al. 2018) and this pattern has been found in Europe (Teichert et al. 2017), North America (Ruiz et al. 1993, Kneib 2000, South Africa (Becker et al. 2017) and New Zealand (Morrison et al. 2002). These patterns are likely a reflection of estuarine and region-specific variation in tidal regime or tidal subsidy (Odum et al. 1995), and especially relative to microtidal and macrotidal estuaries, which can differ in geomorphology, water movements, salinity regimes, residence times, turbidity and intertidal area (Tweedley et al. 2016). ...
... Tidal range also appears to influence fish habitat use in estuaries (Teichert et al. 2018). This appears to be especially important when comparing micro-tidal (<2 m) relative to macro-tidal (>2 m) systems (Taylor et al. 2016), perhaps because the extremes of tidal range influence the amount of productive intertidal habitat as in eastern North Atlantic (Nicolas et al. 2010a, 2010b, Teichert et al. 2017 and Australian (Warry et al. 2018) estuaries. The tidal range also influences aspects of larval dispersal and adult migration, especially along the salinity gradient (Jager 1999, Le Pape & Cognez 2016. ...
Chapter
Many complex factors determine the role of estuarine habitats and landscapes in fish growth and survival that ultimately contribute individuals to adult populations. In this chapter, we recognise the diversity of habitats, both those frequently (e.g. submerged aquatic vegetation, mangroves) and infrequently (e.g. shellfish beds, woody debris) evaluated and how these vary in use among life history stages and among estuaries from the tropics to the poles. Some factors that clearly influence habitat diversity and use vary with temperature, salinity, geomorphology, hydrology and niche availability coupled with species‐specific and intraspecific differences in habitat fidelity and landscape context. This diversity of factors hampers our ability to fully determine habitat quality and connectivity requirements but provides opportunities to enhance our understanding with multiple approaches from basic natural history to application of developing techniques.
... The estuaries are characterized by their high geomorphological and environmental complexity, which is reflected in their high physicochemical variability (Elliott and Quintino 2007;Day et al. 2012), which is strongly related to hydrological circulation patterns, mainly due to changes in the discharge of freshwater into the system (Wolanski et al. 2004(Wolanski et al. , 2006Sun et al. 2009). These environmental variations generate different responses from the community of estuarine organisms (Chícharo et al. 2009;Teichert et al. 2017), related to the characteristics of their life cycle, the possibility of taking advantage of shelter and food opportunities, and their physiological characteristics (Sheaves et al. 2013;Potter et al. 2015;Winemiller et al. 2015). This generates individual distribution patterns of organisms, which is evidenced by changes in density and biomass (Able 2005;Sheaves et al. 2013). ...
... The effect of the environmental variability on the structure of estuarine fish assemblages at different scales is well documented (Whitfield 1999), and in general, it is important to have a comprehensive understanding of the estuarine processes and their mechanisms at each particular estuary (Sheaves and Johnston 2009;França et al. 2011;Vilar et al. 2013;Teichert et al. 2017), which is somewhat addressed in this study. Estuaries are important not only for their importance as spawning areas, which influence the distribution of fish and invertebrates Martino and Houde 2010; Communicated by S. E. Lluch-Cota Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12526-019-01023-0) ...
... Other factors include the use of the estuary as nursery grounds (Sheaves et al. 2013) and shelter during different stages of their life cycle Sheaves et al. 2013;Potter et al. 2015), which lead to changes in species composition, density, and biomass along the estuary (Blaber et al. 1989;Sheaves et al. 2013;Ferreira et al. 2016). On the other hand, the supply of resources and competition (Blaber et al. 1989;Day et al. 2012;Le Pape and Bonhommeau 2015;Whitfield 2016;Teichert et al. 2017), along with tolerance or preference for specific environmental conditions (Blaber et al. 1989;Able 2005;Sheaves and Johnston 2009;Whitfield et al. 2012), also influence the use that fish have of estuaries, which is reflected in variations of the fish assemblage, spatially and temporally. All these processes and forms of use of estuaries are regulated by changes in the environmental conditions, mainly in the hydrological patterns (Wolanski et al. 2004(Wolanski et al. , 2006Sun et al. 2009). ...
Article
Full-text available
Three fish assemblages (functional groups according to estuary use) were examined, which presented different responses to environmental variations, mainly associated to the dry and rainy seasons and high and low salinities and temperatures in the Buenaventura Bay estuary, Colombia, Tropical Eastern Pacific. In total, 4674 individuals were collected, belonging to 69 species of 29 families. The most abundant species was Sphoeroides trichocephalus (35% of the total density). The assemblage of estuarine-resident fishes showed high tolerance to environmental variations since these were present all along the estuary and throughout the year. The assemblage of marine estuarine–dependent species was associated with the rainy season and low salinities and temperatures. The assemblages of marine estuarine opportunist fishes were associated with areas of higher environmental variability in both seasons, dry and rainy. Fish species belonging to the same functional group showed variations in their response to environmental changes which evidenced complex spatial and temporal dynamics. Understanding these changes is necessary to generate effective management plans based on scientific ecological knowledge, which include environmental impacts present in this estuary such as microplastics, heavy metals, and effects of dredging, and their effects on the ecosystem.
... Our results therefore indicate that ongoing climate change may impact marine fish nurseries through declines in overall abundance and shifts in dominance toward fishes with environmentally-tolerant traits. While our study was limited in spatial extent, because estuaries and nursery habitats generally favor r-selected strategists, our findings are likely applicable to nurseries in other regions (Steele et al., 2009;Teichert et al., 2017;Thomson and Lehner, 1976). For example, Teichert et al. (2017) showed that estuaries across the Northeast Atlantic were dominated by opportunistic species with life history traits adapted to unstable environments, while Thomson and Lehner (1976) showed that even rocky, intertidal pools (used as nurseries by coastal species (Dias et al., 2016)) favor rselected strategists. ...
... While our study was limited in spatial extent, because estuaries and nursery habitats generally favor r-selected strategists, our findings are likely applicable to nurseries in other regions (Steele et al., 2009;Teichert et al., 2017;Thomson and Lehner, 1976). For example, Teichert et al. (2017) showed that estuaries across the Northeast Atlantic were dominated by opportunistic species with life history traits adapted to unstable environments, while Thomson and Lehner (1976) showed that even rocky, intertidal pools (used as nurseries by coastal species (Dias et al., 2016)) favor rselected strategists. Teichert et al. (2017) additionally showed that life history strategies were useful predictors of disturbance impacts on estuarine fish communities. ...
... For example, Teichert et al. (2017) showed that estuaries across the Northeast Atlantic were dominated by opportunistic species with life history traits adapted to unstable environments, while Thomson and Lehner (1976) showed that even rocky, intertidal pools (used as nurseries by coastal species (Dias et al., 2016)) favor rselected strategists. Teichert et al. (2017) additionally showed that life history strategies were useful predictors of disturbance impacts on estuarine fish communities. Thus, dominance by opportunistic, r-selected fishes may indicate nurseries that could be heavily impacted by future warming. ...
Thesis
The ensemble of biological, geochemical, and physical processes that occur within ecosystems is driven by the interplay between biological communities and the abiotic environment. Explaining the spatial and temporal dynamics of biological communities in relation to environmental conditions is therefore essential for understanding ecosystem functioning, and ultimately for achieving sustainable development. In marine ecosystems, fish communities are key to ecosystem functioning, and fisheries provide livelihoods for over 10% of the world’s population. However, understanding the processes structuring fish communities remains difficult because community structure varies with both natural environmental fluctuations and, increasingly, human pressures. Effectively managing fisheries and marine ecosystems under global change therefore requires better characterizing fish community dynamics over time and space and disentangling the underlying drivers and mechanisms. While fish ecologists have traditionally relied on species-based approaches (i.e., taxonomic approaches) to study community structure, trait-based approaches (i.e., functional approaches) are increasingly used because they can provide better insight into community assembly and the mechanisms driving community responses. To meet this need for a better understanding of biodiversity dynamics, the present thesis took advantage of long-term scientific monitoring data to characterize the functional responses of fish communities to environmental gradients in the North Sea, Eastern English Channel, and Bay of Somme. All three ecosystems experienced temperature rises and oceanographic changes associated with a warming phase of the Atlantic Multidecadal Oscillation (AMO), which rapidly impacted fish community structure. Consistent biological responses were observed across the three ecosystems despite their different spatial scales, demonstrating that fish communities were affected by environmental change through bio-ecological traits associated with habitat preference and life history. In the North Sea and Eastern Channel, pelagic species were the most responsive and contributed largely to community dynamics, which is likely explained by their greater mobility, higher dispersal rates, and fewer habitat requirements. However, beyond habitat preference, species with r-selected life histories (e.g., low size and age at maturity, low parental investment, small offspring) had the fastest environmental responses whether or not they were pelagic, likely due to their rapid population turnover and generation time. Importantly, the way these species’ responses shaped community structure depended on environmental context. R-selected, pelagic species rapidly declined in the Bay of Somme and Eastern Channel, but rapidly increased in the North Sea. This likely reflects environmental suitability, indicating that after the phase change of the AMO, the Eastern Channel became a less favorable environment for these species, while the North Sea became more favorable. Thus, species with high mobility and fast life history cycles appear capable of rapidly tracking environmental conditions, shifting in abundance in response to environmental suitability. Additionally, as these ecosystems have warmed over the last 30 years, community responses were characterized by increases in mean thermal preference. Importantly, the amplitude of community changes was partially determined by communities’ initial structure and redundancy of bio-ecological traits, showing that community responses depended not only on environmental changes but also on biodiversity itself. Lastly, while fish community responses were consistently associated with climatic changes, historical fishing pressure on large-bodied, demersal species appeared to render fish communities more sensitive to environmental changes by increasing the relative of abundance of pelagic and r-selected species.
... The impact of environmental variability on the structure of fish communities in estuaries at different scales has been extensively studied (Molina et al. 2020). Additional environmental variables have been investigated to reflect the level of anthropogenic stress in the estuarine water (Teichert et al. 2017), and this study partially addresses that. Estuaries play a significant role not only as spawning grounds influencing the distribution of fish but also due to the abundant food resources they offer. ...
... All these processes and patterns of estuary utilization are regulated by changes in environmental conditions, particularly hydrological patterns (Molina et al. 2020). However, due to the complexity of estuarine ecosystems, understanding how fish respond to environmental fluctuations remains an ongoing endeavor (Sheaves et al. 2016;Teichert et al. 2017) Many studies have evaluated the importance of different environmental variables in assemblages of estuarine fishes at different spatial scales, concluding that variations in their specific environmental and morphological characteristics generate unique dynamics in the assemblages of fishes in each estuary, which must be understood within patterns at larger scales (Paumier et al. 2018;Molina et al. 2020;Romero-Berny et al. 2020;Chen et al. 2023). For instance, the unique rivers in Nepal are abundant in aquatic biodiversity, hosting about 252 fish species from different climatic zones (Adhikari 2013;Shrestha 2019). ...
Article
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Siriwattanarat R, Wongroj W, Ngamniyom A, Vilasri V, Chungthanawong S, Punnarak P. 2024. Fish diversity and environmental factors at the Don Hoi Lot Ramsar Site, Thailand. Biodiversitas 25: 1394-1403. The Don Hoi Lot mudflat, recognized as a Ramsar site, is a globally acclaimed wetland located in the Khlong Khon Sub-district of Samut Songkhram Province, Thailand. This research aims to study fish diversity and environmental variables at the Don Hoi Lot Ramsar Site; fish samples were collected using cast nets (mesh size 1.5 cm and 2.5 cm) and gill nets (mesh size of ¾ inch, 1.5 inches, and 2 inches) by local fisheries from four sampling stations which represented upstream (KK1), midstream (KK2), downstream (KK3), and estuary (KK4) zones in Khlong Khon Bay during January to April 2023. A total of 1,389 fish specimens were collected, representing 36 species belonging to 26 families. Higher diversity in number of species (28-35 species), Shannon index (2.90-2.98), and species richness (10.40-13.11) were found at downstream and estuary stations, while the lowest number of fish species (three species), Shannon index (0.75), and species richness (0.68) were recorded at the upstream station. Similarly, the higher relative abundance of fish (84-173 specimens) was observed at downstream and estuary stations, and the lowest relative abundance (29-50 specimens) was also reported at the upstream station. The blackchin tilapia (Sarotherodon melanotheron Rüppell 1852) was the dominant species at the Don Hoi Lot Ramsar Site during the study periods, followed by the Mozambique tilapia (Oreochromis mossambicus Peters 1852)). Principal component analysis (PCA) further revealed that altitude, temperature, pH, salinity, transparency, ammonia, phosphate and silicate had significant relationships within fish assemblages, whereas nitrite and nitrate were less important in this study. Nonetheless, the rapid expansion of the blackchin cichlid population has had an adverse impact on native fish populations, which could pose a real threat to fish diversity and population, and other aquatic organisms.
... The main advantage here is that fish assemblages integrate the direct and indirect effects of environmental stressors on the entire aquatic ecosystem, which helps to understand the ecological significance of the perturbation (Fausch et al., 1990). The habitat requirements of fish species are directly linked with their indicator value (Teichert et al., 2017). For example, the benthic habitat use by demersal fishes allows researchers to understand sediment and water compartments simultaneously, resulting in a more complete approach to the environment (Whitfield and Elliott, 2002). ...
... Araújo et al. (2000) argued that fish assemblages have been used as ecological Table 2 Average similarity within group, average dissimilarity among groups, and species contribution (%) identified in SIMPER analysis, based on fish density in estuarine zones from Guanabara Bay (southeastern Brazil). indicators of environmental changes because they are known to change in composition and structure as their habitats are modified (see also Fausch et al., 1990;Harrison and Whitfield, 2004;Breine et al., 2007;Silva Junior et al., 2013;Whitfield and Harrison, 2014;Izzo et al., 2016;Teichert et al., 2017). As observed from environmental data, the lower precipitation and higher salinity in 2013-2015 could influence the observed change in species composition and dominance. ...
Article
Well-established indicator species for specific areas may change over time. Distinguishing between the influences of natural or anthropogenic environmental drivers on such temporal change is quite tricky, especially in estuaries. Thus, two main questions drove the present quest to properly identify indicator species: “Which? When?“. Analysis covered two datasets of demersal fishes sampled using a bottom trawl in a highly impacted tropical estuary. As expected, changes in the composition of indicator species were observed between sampling periods. Estuarine-dependent and estuarine-opportunist fish species were identified as persistent indicators. The proper interpretation of results from Indicator Species Analysis (ISA) was discussed and some insights were suggested. Analysis of specificity and fidelity of candidate indicator species was suggested to identify more feasible species to be monitored. In a broad sense, constant validation of indicator species is advised since it is essential to guarantee their appropriate use in estuarine environmental monitoring programs. Further studies should focus on the reproductive success and biomarkers for pollution using the indicator species identified for the studied bay.
... These stressors are seriously affecting the ecological quality of transitional waters and particularly their fish communities (Elliott et al. 2015;Teichert et al. 2016). Resident fish species that experience the estuarine environment throughout their life are more responsive to the local interaction of stressors, than non-resident fish using estuaries during a specific life stage (Teichert et al. 2017). ...
... The flounder (Platichthys flesus) is an estuarine resident species excepted during its pelagic larval stage. This species lives principally in the oligo and mesohaline areas which are displaying the most stressful estuarine conditions (Dando 2011;Teichert et al. 2017). Thus, for the past ten years, numerous ecotoxicological studies were conducted in Europe using the flounder which was considered to be a very relevant species for the assessment of the water quality of transitional waters (Evrard et al. 2010;Williams et al. 2011;Henry et al. 2012;Kerambrun et al. 2013;Capela et al. 2016;Dabrowska et al. 2017;Borcier et al. 2020). ...
Article
Full-text available
The main objective of this study was to improve our knowledge on the responses of fish populations to multistress (diffuse pollution and warming waters) in estuaries. Adult flounders were caught in two estuaries in the Eastern English Channel: the heavily polluted Seine estuary vs the moderately contaminated Canche estuary. Fish samplings were conducted in January just before the reproduction period, and in July when gonads were at rest. The overall rise in coastal winter water temperatures detected over the Channel impairs the flounder’s phenology of reproduction in the two estuaries, inducing a delay of maturation process and probably also spawning. The higher liver histopathology index in Seine vs Canche could be the consequence of the fish exposition to a complex cocktail of contaminants in a strongly industrialized estuary. Higher levels of neurotoxicity, gill lipid peroxidation, and liver EROD activity were observed in Seine vs Canche. Furthermore, a possible impairment in mitochondrial metabolism was suggested in the Seine flounder population. We confirmed in this study the potential role of two membrane lipids (sphingomyelin and phosphatidylserine) in the resistance towards oxidative stress in Seine and Canche. Finally, we suggest that the Seine flounder population (and possibly the connected Eastern English Channel flounder populations over the French Coast) could be seriously impacted in the future by multistress: higher winter temperatures and chemical contamination.
... As an additional concern, these models largely exclude critical biological and life history attributes, which could affect the responses and overall sensitivity of species to environmental changes (Willis et al., 2015). For example, fish species with different features related to the processes of growth, reproduction, and survival are likely to respond differently to climate change (Liu et al., 2017;Teichert et al., 2017). Small-bodied fish with early maturation, low fecundity, and extended spawning season are mostly met in dynamic environments. ...
... Small-bodied fish with early maturation, low fecundity, and extended spawning season are mostly met in dynamic environments. In contrast, fish with late maturation, well-developed offspring, and high investment in offspring survival tend to benefit from stable and predictable habitat conditions (Teichert et al., 2017). ...
Article
Understanding how climate change would affect biota inhabiting sensitive and highly valuable ecosystems, spanning broad regions, is essential to anticipate implications for biodiversity and humans, and to identify management and mitigation measures. Traditionally, assessments to evaluate climatic risks over broad regions and for many species, implement models that allow the projection of a climate driven redistribution of diversity. Still, the wealth and quality of the background information (e.g., species presence data) constrain the accuracy and representativeness of such frameworks. As an alternative, here, we developed a twofold approach to assess the vulnerability of 86 European freshwater fish. We accounted for shifts in a multidimensional climatic space of broader hydrological units that host freshwater bodies in Europe, and linked metrics of their climatic stability with groups of species, which were generated from six intrinsic traits that shape species adaptive capacity to climate change. Our results demonstrated that the climate of all (n = 538) river sub-basins hosted in the European Union territory would change by 2100, with more than 10% of them being projected to gain completely novel climates. Sub-basins predicted to lose more than 90% of their current climatic space were mainly identified in the area around the Baltic Sea, but also in Mediterranean regions (i.e., Iberian Peninsula). Important numbers of fish species with life history strategies that are considered susceptible to climate change were identified in sub-basins that were predicted to completely lose their current climatic conditions. Clearly, the climate of valuable freshwater ecosystems is changing, affecting species and their communities in varying ways. The risk is high, and is not limited to specific regions; thus, new effective strategies and measures are needed to conserve freshwater fish and their habitats across Europe.
... than marine migrant species. In a study of fish, functional attributes and environmental gradients in 47 north-east Atlantic estuaries,Teichert et al., (2017) only considered estuarine-resident species as this group of fishes are subject to the environmental conditions in estuaries throughout their life; non-resident (migratory) species, on the other hand, only occur in estuaries temporarily, often during a specific life stage. A significant decline in the distribution and diversity of life-history strategies of resident estuarine species was reported along gradient of human disturbance(Teichert et al., 2017).The application of the FEAS to fish communities of estuaries that were subjected to either degradation or rehabilitation allowed functional estuary-use change to be numerically described and statistically compared. ...
... In a study of fish, functional attributes and environmental gradients in 47 north-east Atlantic estuaries,Teichert et al., (2017) only considered estuarine-resident species as this group of fishes are subject to the environmental conditions in estuaries throughout their life; non-resident (migratory) species, on the other hand, only occur in estuaries temporarily, often during a specific life stage. A significant decline in the distribution and diversity of life-history strategies of resident estuarine species was reported along gradient of human disturbance(Teichert et al., 2017).The application of the FEAS to fish communities of estuaries that were subjected to either degradation or rehabilitation allowed functional estuary-use change to be numerically described and statistically compared. The general response of applying the FEAS was an increase in E-FEAS with increasing anthropogenic pressure or degradation; the E-FEAS declined in response to remedial measures(Table 2).While the FEAS is a useful method of numerically expressing and analysing the functional estuary-association composition of a fish community, as with most fish community studies this system requires a representative sample of the fishes present. ...
Article
A novel fish estuary‐association scoring (FEAS) system that numerically expresses the relative position or level of estuarine‐association for each species has been developed. A dataset numerically describing the degree or level of estuarine‐association for some 6,000 fish species has been established based on an extensive review of the scientific literature on coastal and freshwater fishes. The FEAS reflects both globally recognized fish estuary‐association functional guilds as well as the continuum of fish estuarine use and dependence. The application of FEAS to numerically analyse and functionally compare estuarine fish communities using a range of statistical and analytical methods is demonstrated by examples from a variety of studies around the world; its use as a potential environmental monitoring and assessment tool is also presented.
... L'ensemble de ces activités humaines entraînent une chute importante du nombre d'espèces de coraux et de poissons coralliens, amenant à la disparition de certaines fonctions clefs nécessaires à la résilience et à la survie des récifs [D'agata et al., 2014]. Récemment, les perturbations subies par les écosystèmes marins et en particulier les écosystèmes récifaux s'accélèrent [Butchart et al., 2010] [Teichert et al., 2017] [Hoegh-Guldberg et al., 2017] [Weijerman et al., 2018] [Hughes et al., 2018] [Sully et al., 2019] et appellent à un effort de surveillance sans précèdent [Veitch et al., 2012] [Hughes et al., 2017]. L'utilisation de protocoles d'observations des écosystèmes récifaux ponctuels (spatialement et temporellement) ne permet plus de suivre le rythme des perturbations qu'ils subissent. ...
... Les effets négatifs de telles méthodes sur la biodiversité marine à court et à long terme ainsi que sur le fond marin ont été discutés de nombreuses fois, que ce soit à des fins scientifiques [Jouffre et al., 2009] [Trenkel and Cotter, 2009] ou commerciales [Jones, 1992] [Kaiser et al., 1996] [Eigaard et al., 2015] [Kaiser et al., 2002] [Thrush and Dayton, 2002]. ...
Thesis
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Les récifs coralliens soutiennent une forte biodiversité en poissons (environ 7000 espèces) qui est la source de plusieurs services écosystémiques comme l’apport en protéines via la pêche, la régulation des flux de matière mais aussi le support d’activités récréatives comme la plongée. Cependant, ces poissons subissent des pressions croissantes comme la surexploitation par la pêche et la destruction du corail par réchauffement climatique. Dans ce contexte, un des enjeux majeurs de l’écologie marine est d’estimer précisément la biodiversité, l’abondance et la biomasse de ces poissons récifaux et ce, avec une fréquence temporelle permettant de détecter les modifications liées aux changements environne-mentaux, aux pressions anthropiques et aux stratégies de gestion (e.g. réserves marines). Jusqu’à récemment, le recensement des poissons récifaux s’effectuait principalement en plongée au cours desquelles l’observateur identifiait toutes les espèces visibles et estimait leurs abondances (nombre d’individus). Ce protocole induit des limites comme la durée et la profondeur des plongées ainsi que des erreurs ou des biais liés à l’expérience du plongeur qui ne sont pas quantifiables ou corrigibles a posteriori. Face à ces limitations, les récents développements technologiques dans la prise de vidéos sous-marines en haute définition à moindre coût offrent des protocoles beaucoup moins contraignants. Cependant, il n’existe à l’heure actuelle aucun moyen rapide et fiable d’analyser ces quantités de données ce qui empêche l’essor de ces suivis vidéos à grande échelle. Au cours de cette thèse, nous avons mis en place des algorithmes d’identification et de localisation automatiques de poissons dans des vidéos sous-marines. L’ensemble du processus fut abordé, depuis les campagnes terrain permettant de récolter les vidéos à l’annotation de ces données afin de les rendre exploitables par des algorithmes d’apprentissage profond (ou Deep Learning), à la conception des modèles, au test de ces modèles et au traitement des sorties des différents modèles. Nous avons ainsi récolté plus de 380.000 images appartenant à plus de 300 espèces de poissons récifaux. Nous avons développé des méthodes d’identification précises (94% de bonnes classifications) pour 20 espèces parmi les plus présentes sur les récifs coralliens autour de Mayotte, ainsi que des méthodes de post-traitement permettant de détecter et de supprimer les erreurs commises par le modèle (diminuant ainsi le taux d’erreur jusqu’à 2%). Nous avons aussi développé un algorithme de détection permettant de localiser plus de 84% des individus présents à l’image sur une vidéo.
... This is a common feature of fish communities in estuary waters. The number of fish species found at the Bogowonto River Estuary was more than previous studies carried out in other areas such as the number of fish species found in the Sepang Besar Estuary (Selangor-Malaysia, 29 species) [12], the Aksu River Estuary (Antalya-Turkey, 26 species) [13], and Mar Chiquita coastal lagoon (Argentina, 28 species) [14], but fewer than the Lima Estuary (Portugal, 50 Species) [15], and coastal lagoon in the Gulf of California (México, 95 species) [16]. Visiting, distribution, clustering and assemblage for fish larvae in estuaries were influenced by a complex combination of biotic and abiotic factors. ...
... The area of Bogowonto River Estuary provides a habitat for growing up for most fishes with the discovery of various species of marine, brackish and fresh water fishes in the juvenile stage. Estuaria is a coastal environment which naturally experiences high variability in physicochemical conditions, which affects the composition of the aquatic community [13]. Most fish species that live permanently or temporarily at the Bogowonto River Estuary have a wide tolerance limit to the fluctuating conditions found in this ecosystem. ...
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The aim of this study was to determine the diversity of fish species, and the role of the Bogowonto River estuary as the nursery and feeding ground of fishes. Seven sampling stations were determined in the estuary of Bogowonto River. Fish samples were identified, and measured the length and weight. The results showed that 2235 fishes were caught consisting of 38 species. The monthly Shannon-Wiener diversity index (H’) ranged from 1.05 to 2.38, while the evenness index (E) ranged from 0.44 to 0.74, and the species richness index (D) ranged from 0.22 to 0.45. The diversity index at each station showed the range of 1.72 to 2.29, and the evenness index ranged from 0.59 to 0.85, while the evenness index ranged from 0.22 to 0.34. The presence of the most numerous species namely Mystus gulio had the occurrence of 35.35%, and the second largest number was Moolgarda engeli 14.08% then Ambassis macrachantus 11.54%. Most fishes were juvenile with average size of <10 cm and weight <15 g. Bogowonto River estuary has played an important role in providing a nursery, feeding and spawning ground for marine, brackish and freshwater fishes.
... Among the most valuable marine fish species, the marine-estuarine opportunist (MEO) fish species constitute one fifth of the species richness of estuarine systems along the French and Iberian coasts of the Northeast Atlantic (Teichert et al., 2017). Indeed, MEO fish species are unique species distinguished by their complex life cycle involving dependence to estuarine or coastal environments (Potter et al., 2015;Cabral et al., 2022). ...
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Marine-estuarine opportunist (MEO) species are fish that occur in the continental shelf and use estuaries and/or shallow coastal areas as nurseries. These commercially important resources are facing significant environmental modifications caused by direct and/or indirect anthropogenic climate change effects. In this study, we investigated the directionality and the magnitude of the distribution shifts (i.e., range size, gravity centroids, and margins) in marine environment suitability for six main MEO fish species within the Northeast Atlantic expected for the end of the 21st century. In the framework of this study, we have distinguished ‘sub-boreal’ from ‘sub-tropical’ species. The ‘hierarchical filters’ concept was adopted for modelling the potential species distributions and combined the predictions of i) a bioclimatic model with ii) a habitat model. The bioclimatic model is based on large-scale and time-variant variables while variables of the habitat model are fine-grained and time-invariant. Two Intergovernmental Panel on Climate Change (IPCC) scenarios are tested: an intermediate (SSP2-4.5) and a pessimistic one (SSP5-8.5). We applied this framework using international databases of biodiversity occurrences, ensemble forecasting producing consensual predictions, and innovative indices of distribution shifts. A visible north-westward shift was predicted for all six species in our study area. However, the northward expansion was greater for ‘sub-tropical’ than for ‘sub-boreal’ species due to faster gravity centroid displacement shifts and faster margins shifts. These range shifts may lead to major ecological impacts (e.g., changes in recruitment to estuarine and coastal nurseries, as well as changes in spawning grounds) that may alter populations’ connectivity.
... Thus, the life cycle strategies of sh can be determined by speci c combinations of population traits that in uence the behavior of the species, including their diet, according to environmental characteristics (Teichert et al., 2017). Diet is a crucial tool to identify functional groups, trophic level, and prey preference, in a habitat with different environmental gradients, such as those contaminated with microplastics (Martins et al., 2017). ...
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The abundance of microplastic particles may be linked to fish populations through ingestion, due to the presence of debris throughout the marine environment. In this study, the influence of biological characteristics on the ingestion of microplastics was evaluated in 28 species of fish from the Sciaenidae family and 12 from the Ariidae family in the estuaries of Tumaco and Buenaventura Bay. The samples were collected in high and low precipitation seasons during the years 2020 and 2021, then a characterization of the stomach contents of 894 specimens in Tumaco Bay (479 Sciaenidae and 415 Ariidae) and 758 specimens in Buenaventura Bay was carried out. (267 Sciaenidae and 491 Ariidae) the number of microplastics per stomach was recorded. Additionally, their trophic level (TL) was calculated, and they were grouped into three groups (high, medium, low). As the main result, a positive correlation was found between the trophic level and the consumption of microplastics for both the Ariidae family (p=0.0254) and the Sciaenidae family (p=0.0028). Additionally, differences in consumption were found between TL for the Ariidae family (p(Per)=0.017) and Sciaenidae (p(Per)=0.031), with the high TL being the one that presented the greatest presence of microplastics (MP). This agrees with what was found in studies carried out in estuarine coastal areas, where a positive relationship is shown between the abundance of microplastics and the trophic level of organisms. Likewise, the Condition Factor (CF) presented lower values (<1) in adult individuals that consumed MP, which indicates that the well-being of fish species decreases with this contaminant. These findings indicate that microplastics generate a negative effect on the normal development of fish, as has been reported in other parts of the world.
... Fish functional diversity tends to decrease with climate change, leading to functional convergence toward traits that are more adapted to novel environments [148]. Such patterns have emerged in marine [148], estuarine [149], and freshwater [150] fish communities, with longlived species with late maturation and/or large body sizes being disproportionately impacted [139,151]. However, different proxies of functional richness can sometimes show opposing effects to climate change stressors, highlighting the importance of testing complimentary measures of diversity [152]. ...
Chapter
Fishes comprise the most diverse group of aquatic vertebrates and are found across the world’s aquatic biomes and ecosystems — in freshwater, estuaries, as well as in the ocean. With this diversity also comes an extensive array of life histories, behaviors, physiologies, and adaptations. In addition to long-term direct human perturbations on fish populations and communities, such as overfishing, habitat destruction, and aquatic pollution, indirect human stressors such as various climate change stressors are now increasingly having an impact on many fish species as well. It is predicted that climate change stressors such as warming, acidification, and hypoxia will alter fish biodiversity, change their geographic distributions, alter their fitness and performance, and create novel community structures. Due to their rich diversity, it is difficult to predict how each fish species will respond to the interplay of various climate stressors. However, fish species can often be classified into guilds, functional groups, life history strategies, etc., based on various traits. As such, some generalizable patterns may emerge on how specific (taxonomic/functional) groups of fish species might respond to current and future climate change. This bibliography covers key studies on climate change effects on (predominantly marine) fishes, through the lens of fish ecology. It assesses the current published literature in terms of various research fields in fish ecology, scaling up from cellular, individual, and population levels to higher levels of biological organization such as communities, ecosystems, and biogeographies. Such a broad bibliography might provide for a better appreciation of the complexity of studying climate change impacts on fishes, as their ecology is intertwined with that of many other species, habitats, and environmental drivers. The ecological responses of fishes at multiple levels of biological organization mediate their fitness, performance, and persistence, and generalizable insights are needed for their biodiversity conservation, and to evaluate their importance for various ecosystem services, including fisheries.
... Abiotic and biotic factors influence estuarine habitats and associated fish assemblages [36]. For example, substrate composition, estuarine depth, estuarine surface area, and proportion of intertidal area are important predictors of total fish abundance in European estuaries (e.g., [37,38]). The intensification of local anthropogenic disturbances in estuaries is also associated with a decrease in species richness and fish abundance [39,40]. ...
Article
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The aim of this study was to investigate the influence of environmental characteristics and anthropogenic pressures on the abundance of estuarine European eels (Anguilla anguilla L.) during their continental growth phase. European eels were collected with fyke nets from spring to autumn in twenty-nine estuaries along the French English Channel and the Atlantic coast. Eel abundance (catch per unit effort, CPUE) was assessed for all eels and by size class for small (total length < 300 mm), intermediate (≥300 to <450 mm), and large (≥450 mm) eels. The environmental characteristics of the French estuaries were described by twelve descriptor variables, mainly related to hydro-morphological and sedimentary factors. Based on principal component analysis and hierarchical clustering analysis, estuary size was identified as the main explanatory variable and used to compare eel abundance. Eel abundance differed significantly according to estuary size, with higher abundances observed in small estuaries (7.22 to 13.00 ind. fyke nets 24 h−1) compared to large estuaries (0.13 to 0.71 ind. fyke nets 24 h−1). Spatial variation in eel abundance was correlated with differences in estuary size for all eel size classes. The influence of anthropogenic pressures on eel abundance was assessed by nine anthropogenic estuarine pressure indicators. The results indicate that high values of the anthropogenic pressure indicators were correlated with low eel abundance. This study highlights that large French estuaries subject to stronger anthropogenic pressures were less favourable habitats than small estuaries with less anthropogenic pressure.
... All the variables measured in sediment and in the water column were individually correlated with Page 11 of 17 1316 Vol.: (0123456789) THg in sediments, except for temperature, which suggests a complex dynamic of the distribution and accumulation processes of mercury in sediments in Buenaventura Bay Quintana et al., 2020). This complexity has been associated with the environmental dynamic proper of the estuarine ecosystems (Elliott & Quintino et al., 2007;Teichert et al., 2017;Li & Li, 2018;Pérez-Ruzafa et al., 2019). This variation in mercury distribution and accumulation could be produced by the interaction of different environmental variables with the chemical and hydrodynamic processes controlling mercury deposit and resuspension Curtis et al., 2019;Fiorentino et al., 2011;Garcia-Ordiales et al., 2018;He et al., 2019;Padalkar et al., 2019;Wasserman et al., 2002). ...
Article
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Estuaries are the main entry areas of mercury to the marine environment and are important to understand the effect of this contaminant on marine organisms, since it accumulates in the sediments becoming available to enter the food trophic chain. This study aims to determine the environmental variables that mainly influence the spatiotemporal dynamics of total mercury accumulation in sediments of tropical estuaries. Sediment samples were collected from interior and exterior areas of the estuary during the dry and rainy seasons, representing the spatiotemporal gradients of the estuary. The grain size, organic matter content (OM), and total mercury concentration (THg) of the sediment samples were determined. In addition, salinity, temperature, dissolved oxygen, and pH of the water column associated with each sediment sample were assessed. The variations in environmental conditions, OM and THg in sediment were in accordance with a gradient which goes from conditions influenced by fresh water in the inner estuary to conditions influenced by sea water in the outer part of the estuary. The OM and THg in sediments presented similar variation patterns; they were higher in the rainy season than in the dry season and in the interior area of the estuary than in the exterior area. Despite the complex dynamic observed in the distribution and accumulation processes of mercury in sediments, these processes could be modeled from OM and salinity parameters. Due to the correlations found, in the process of accumulation of mercury in sediments the OM could represents the pathway of transport and accumulation of THg, and salinity could represent the influence of the hydroclimatic variations and environmental gradients of the estuary. Supplementary Information The online version contains supplementary material available at 10.1007/s10661-023-11721-9.
... Fish functional diversity tends to decrease with climate change, leading to functional convergence toward traits that are more adapted to novel environments [148]. Such patterns have emerged in marine [148], estuarine [149], and freshwater [150] fish communities, with longlived species with late maturation and/or large body sizes being disproportionately impacted [139,151]. However, different proxies of functional richness can sometimes show opposing effects to climate change stressors, highlighting the importance of testing complimentary measures of diversity [152]. ...
Article
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Ocean warming and acidification are set to reshuffle life on Earth and alter ecological processes that underpin the biodiversity, health, productivity, and resilience of ecosystems. Fishes contribute significantly to marine, estuarine, and freshwater species diversity and the functioning of marine ecosystems, and are not immune to climate change impacts. Whilst considerable effort has been placed on studying the effects of climate change on fishes, much emphasis has been placed on their (eco)physiology and at the organismal level. Fishes are affected by climate change through impacts at various levels of biological organisation and through a large variety of traits, making it difficult to make generalisations regarding fish responses to climate change. Here, we briefly review the current state of knowledge of climate change effects on fishes across a wide range of subfields of fish ecology and evaluate these effects at various scales of biological organisation (from genes to ecosystems). We argue that a more holistic synthesis of the various interconnected subfields of fish ecology and integration of responses at different levels of biological organisation are needed for a better understanding of how fishes and their populations and communities might respond or adapt to the multi-stressor effects of climate change. We postulate that studies using natural analogues of climate change, meta-analyses, advanced integrative modelling approaches, and lessons learned from past extreme climate events could help reveal some general patterns of climate change impacts on fishes that are valuable for management and conservation approaches. Whilst these might not reveal many of the underlying mechanisms responsible for observed biodiversity and community change, their insights are useful to help create better climate adaptation strategies for their preservation in a rapidly changing ocean.
... For example, seasonal fluctuations in freshwater discharge may shift the locality of estuary salinity classifications (i.e., oligohaline [0.5-5 psu], mesohaline [5-18 psu], polyhaline [18-30 psu]) several miles within a single year. Any study seeking to understand fish movement and habitat use patterns across salinity gradients should consider spatiotemporal variations in salinity and resulting water chemistry due to interannual differences in freshwater discharge (Teichert et al. 2017). Another limitation is that elemental incorporation into otoliths may differ across salinity gradients (Nelson and Powers 2020). ...
Article
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Otolith chemistry is a useful natural tracer for discerning habitat‐use of estuarine fishes. For Southern Flounder Paralichthys lethostigma, recent otolith chemistry studies have revealed a diversity of residency patterns across salinity gradients. However, the contribution of recruits with specific residency patterns to fisheries is poorly understood. The objectives of this study were to (1) use otolith chemistry from fishery‐independent and fishery‐dependent collections in Mobile Bay, Alabama, to classify lifetime residency patterns (i.e., freshwater, transient, estuarine) in Southern Flounder collected across a large estuarine salinity gradient (0–30 psu); (2) to test if Southern Flounder exhibited resident or migratory behavior by determining if lifetime residency patterns in fishery‐independent samples matched expected salinity patterns in the region of collection after accounting for annual variation in river discharge; and (3) to examine which residency patterns contributed to the commercial and recreational Southern Flounder fisheries in nearby coastal waters. Age‐0 residency patterns in fishery‐independent samples were strongly correlated with region of collection and annual river discharge, suggesting that the majority of Southern Flounder had resided in the same region in which they spent their age‐0 growth phase. Southern Flounder with a combination of freshwater and estuarine salinity signals and classified as “transient” did not appear to have conducted large‐scale movements across salinity gradients, but instead resided in regions of the estuary experiencing seasonal fluctuations in salinity. The majority (57%) of commercially and recreationally harvested Southern Flounder were transients, while a minority (39%) were estuarine residents and lifetime freshwater residents (4%) were rarely harvested. Results from this study suggest that Southern Flounder settle in and remain in the certain habitats during the estuarine residency phase. Given the lack of movement across habitats, future efforts to understand how habitat‐specific conditions (e.g., abiotic, biotic, fishing exploitation) affect vital rates seems warranted for a species currently experiencing population declines.
... The responses of fish assemblages to external stimulus differ over time are commonly observed in highly variable coastal ecosystems as a function of habitat selection to attain their ecological requirement range in order to complete their life history and growth (Teichert et al., 2017). In TL, the first relationships between hydrographic variables and fish composition were explored by Ramos-Miranda et al. (2008), but because a short dataset was used, the results were poorly predictive. ...
Article
The distribution of biological communities is structured at multiple spatiotemporal scales. The identification of trends and patterns in highly variable coastal ecosystems contributes to explaining the relative importance of the different scales. Herein, a temporally nested hierarchical analysis was applied to a fish community in order to determine the temporal variation in three time scales (month, season, and year) for four community attributes (species richness, abundance, biomass, and taxonomic distinctness) and two facets of species assemblages (species composition and abundance, and species composition and biomass). The analysis relied on data from four similar sets of samples belonging to a multidecadal series of Terminos Lagoon (1980, 1998, 2010, and 2016). In accordance with the hydrographic variability over time, the results revealed recurrent configurations of fish community characteristics, where the year (long term) and season (intermediate term) scales determined distribution trends and species composition patterns. In particular, trends emerged for the community attributes in the long term, whereas in the intermediate term, fluctuations were mostly recorded, which had higher values during the rainy and cold fronts seasons. Distribution patterns in both facets of species assemblages were consistent in the long and intermediate term, with the first one corresponding to an associated group of species for each year and the second one corresponding to a variable interaction with transparency and salinity according to the weather season. The present study highlights the fish adaptive response, which contributes to the ecological processes driving their temporal variability in Terminos Lagoon and is associated with hydrographic variability and estuarine condition shifts.
... Regulated river flows might also affect the habitat connectivity between the estuary and the sea, with periods of high flows causing the flushing of marine larvae with limited swimming ability, and/or preventing their entry and reach of suitable estuarine habitats, not only affecting recruitment but ultimately, species life cycle closure. Hence, this study reinforces that the regulation of freshwater input into estuaries affects not only the hydrodynamics of the system but also the biological communities and their ecological functioning, namely their nursery role for larval and juvenile stages of fishes (Teichert et al., 2017;Miró et al., 2020). ...
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Larval stages of fishes are highly vulnerable to environmental shifts and anthropogenic pressures can pose additional stress to such a critical phase. The present study aimed to investigate environmental controls on the larval fish assemblages of the Douro Estuary, a heavily modified water body with several anthropogenic pressures. Monthly sampling surveys were conducted over two years along the estuarine horizontal gradient. The estuarine larval fish assemblage was dominated by a few very abundant taxa. Resident Pomatoschistus microps and members of the marine Clupeidae and Soleidae families were the most abundant taxa, accounting for 87.5% of the total catch. Canonical correspondence analysis identified e.g., river flow and salinity as the main environmental variables regulating the larval fish assemblages in the Douro Estuary. River flow had a significant impact on larval fish abundances with the lowest abundances observed when river flow surpassed 900 m³ s⁻¹. Overall, the Douro larval fish assemblage exhibited similar features to other less impacted temperate estuaries. However, the results of this study highlighted the negative impact of regulating river flows that can compromise the connectivity of estuaries with adjacent coastal areas and, ultimately, their nursery function for the early life stages of fishes.
... Using multiple sources of monitoring data from 1980 to 2018, we modeled the abundance of juvenile fish species with diverse life history strategies and quantified the effects of freshwater flow and SST across five regions of the estuary. We expected abundance trends and environmental effects to vary widely based on species identity, estuarine use type, and thermal and salinity tolerances (Elliott et al., 2007;Feyrer et al., 2015;Teichert et al., 2017). Next, we asked, does biological or spatial structure buffer long-term aggregate fish abundance from environmental variability? ...
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Investigating the effects of climatic variability on biological diversity, productivity, and stability is key to understanding possible futures for ecosystems under accelerating climate change. A critical question for estuarine ecosystems is, how does climatic variability influence juvenile recruitment of different fish species and life histories that use estuaries as nurseries? Here we examined spatiotemporal abundance trends and environmental responses of 18 fish species that frequently spend the juvenile stage rearing in the San Francisco Estuary, CA, USA. First, we constructed multivariate autoregressive state-space models using age-0 fish abundance, freshwater flow (flow), and sea surface temperature data (SST) collected over four decades. Next, we calculated coefficients of variation (CV) to assess portfolio effects (1) within and among species, life histories (anadromous, marine opportunist, or estuarine dependent), and the whole community; and (2) within and among regions of the estuary. We found that species abundances varied over space and time (increasing, decreasing, or dynamically stable); and in 83% of cases, in response to environmental conditions (wet/dry, cool/warm periods). Anadromous species responded strongly to flow in the upper estuary, marine opportunist species responded to flow and/or SST in the lower estuary, and estuarine dependent species had diverse responses across the estuary. Overall, the whole community when considered across the entire estuary had the lowest CV, and life histories and species provided strong biological insurance to the portfolio (2.4- to 3.5-fold increases in stability, respectively). Spatial insurance also increased stability, although to a lesser extent (up to 1.6-fold increases). Our study advances the notion that fish recruitment stability in estuaries is controlled by biocomplexity—life history diversity and spatiotemporal variation in the environment. However, intensified drought and marine heatwaves may increase the risk of multiple consecutive recruitment failures by synchronizing species dynamics and trajectories via Moran effects, potentially diminishing estuarine nursery function.
... The effects of climate change on estuaries vary with estuarine morphology and the structure of surrounding watersheds, but globally, estuaries are experiencing more extreme salinities, acidification, and in some cases, warming at twice the rate of the surrounding ocean (Gillanders et al. 2011;Scanes et al. 2020). These habitat changes are driving a variety of ecological outcomes, including shifts in diversity and abundance of estuarine communities (Gillanders et al. 2011;Nyitrai et al. 2012;Teichert et al. 2017). Growth and body condition of juvenile fishes may vary with changes in temperature, salinity, and suspended sediment during the period of estuarine rearing (Sogard 1992;Lankford and Targett 1994;Lowe et al. 2015). ...
Article
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Coastal ecosystems in Alaska are undergoing rapid change due to warming and glacier recession. We used a natural gradient of glacierized to non-glacierized watersheds (0–60% glacier coverage) in two regions along the Gulf of Alaska—Kachemak Bay and Lynn Canal—to evaluate relationships between local environmental conditions and estuarine fish communities. Multivariate analyses of fish community data collected from five sites per region in 2019 showed that region accounted for the most variation in community composition, suggesting that local effects of watershed type were masked by regional-scale variables. Seasonal shifts in community composition were driven largely by the influx of juvenile Pacific salmon ( Oncorhynchus spp.) in late spring. Spatiotemporal differences among fish communities were partly explained by salinity and temperature, which accounted for 19.5% of the variation in community composition. We used a multi-year dataset from Lynn Canal (2014–2019) to examine patterns of mean length for two dominant species. Generalized additive mixed models indicated that Pacific staghorn sculpin ( Leptocottus armatus ) mean length varied along site-specific seasonal gradients, increasing gradually through the summer in the least glacially influenced sites and increasing rapidly to an asymptote of ~ 150 mm in the most glacially influenced sites. Starry flounder ( Platichthys stellatus ) mean length was more strongly related to environmental conditions, increasing with temperature and turbidity. Together, our findings suggest that community compositions of estuarine fishes show greater variation at the regional scale than the watershed scale, but species-specific variation in size distributions may indicate differences in habitat quality across watershed types within regions.
... Delpech et al. 2010) or to characterise the response of a fish community to disturbance (e.g. Chevillot et al. 2016, França & Cabral 2016, Teichert et al. 2017. In all these studies, anthropogenic disturbance metrics were included along with environmental variables to account for the control of natural variability on the estuarine fish community (Fonseca et al. 2014). ...
Chapter
This chapter addresses the use of fish as indicators of environmental health. The main anthropogenic pressures impacting estuarine fishes are reviewed, as well as the main types of responses by fishes at different levels of biological organisation. Fishes have been widely used to assess estuarine health through different methodological approaches, namely comparisons with historical data or reference conditions, experimental approaches, environmental impact or risk assessment methods, as well as qualitative or quantitative indicators and models. A large number of multi‐metric indices based on fish have been proposed and are routinely used in environmental assessments, although to disentangle natural variability from anthropogenic pressures in a multi‐stress context of global change is still a major challenge.
... Although modes of reproduction are diverse, relatively few species reproduce within estuaries, possibly because of extreme and sometimes rapid changes in temperature and salinity, as well as microbialrich conditions that can prevail (Dando 1984). In addition, other water quality conditions such as hypoxia can be stressful to young fishes (Teichert et al. 2017). ...
Chapter
The patterns of reproduction and ontogeny in the taxonomically rich estuary- associated fishes from around the world, including all the major groups from elasmobranchs to bony fishes, are as diverse as documented for fishes living in other ecosystems. Further, the diversity in the life histories of bony fishes, the dominant group in estuaries, is complex with egg, larval, juvenile and adult stages having different ecologies. Moreover, some stages that use estuaries also use the adjacent, downstream ocean and upstream freshwaters for parts of their life history. Given these complexities in patterns and modes of reproduction, it is not surprising that recruitment processes of estuary- associated fishes are also diverse. In Introduction, we listed six broad topic areas that framed the scope of the chapter. We summarise major conclusions in the six areas.
... The reason for highlighting the very limited fish species redundancy in temperate compared with tropical estuaries is linked to the pervading view that fishes in estuaries are resilient to external stressors and therefore do not require as much conservation attention (Teichert et al., 2017) as some of the more environmentally sensitive taxa that occur in freshwater (Frederico, Olden & Zuanon, 2016) or marine environments (Olden, Hogan & Van der Zanden, 2007). ...
Article
• Fish assemblages in estuaries have a much lower species richness (number of taxa) when compared with the combined numbers of freshwater and marine species from adjacent aquatic ecosystems. This is primarily because of the relatively harsh and fluctuating physico‐chemical conditions in estuaries compared with the more stable freshwater and marine environments. • A comprehensive fish survey of estuaries in South Africa is used as a basis to determine fish species richness in subtropical, warm temperate, and cool temperate systems along the coast, and to assess the degree of redundancy in the different biogeographic regions. • In general, only one or two species belonging to each of the detritivorous, piscivorous, zoobenthivorous, and zooplanktivorous fish guilds are numerically well represented in the larger cool temperate estuaries, but between four and 10 species in each of these guilds are usually recorded in the larger subtropical estuaries. • Although the overall low redundancy of fish species groups in estuaries has already been formally recognized in the literature, this short note highlights the sensitivity of certain trophic guilds in temperate South African estuaries to any form of redundancy, a characteristic that may be equally applicable, based on declining species richness with increasing latitude, to temperate estuaries in other parts of the world.
... A few fish species are adapted, however, to completing their whole life cycle in their natal estuary, and these are most prevalent in microtidal estuaries in Mediterranean climates, such as those along the southern coasts of Australia and Africa, where warm and dry summer periods and limited tidal water movement provide a relatively benign environment for spawning and larval development (Potter et al., 1990(Potter et al., , 2015bPotter and Hyndes, 1999;Whitfield, 2019). These species, which often belong to families such as the Atherinidae, Gobiidae and Syngnathidae, are almost invariably small and short-lived and exclusively so along the southern African coast where there are 25 such species (Whitfield, 2019) and the same is true for estuaries along the North Atlantic coast (Teichert et al., 2017). While this generalisation is also true for the extensive southern coast of Australia, the sparid Acanthopagrus butcheri provides a stark exception as it can live for up to 30 years and attain substantial fork lengths of ~600 mm (Morison et al., 1998: Potter et al., 2008. ...
Article
This study has elucidated the environmental factors associated with spawning and the ecology of early life cycle stages of the sparid Acanthopagrus butcheri, which is atypically long-lived and large for a species confined to its natal estuary. The prevalence of A. butcheri eggs in monthly plankton samples from the Blackwood River Estuary, southwestern Australia, in 2014/15, allied with long-term gonadal data, imply that spawning in this estuary commences in mid-spring (October) as water temperatures increase to ~17 • C and peak at ~22 • C in early summer (December). Eggs were initially found only in deeper, downstream areas, where a salt wedge had started to penetrate following precipitous seasonal decline in freshwater discharge. Spawning occurred progressively further upstream during November/December as the salt wedge continued its intrusion of the upper estuary. The concentrations of eggs and yolk-sac and preflexion larvae, which were related positively to salinity and temperature and less so to oxygen concentration, were located predominantly below the halocline, implying that successful spawning typically requires salinities ≥15. Concentrations of eggs and yolk-sac and preflexion larvae peaked in December and of flexion larvae in January. As the concentrations of copepod nauplii exceeded by orders of magnitude those of larval A. butcheri, with which they co-occur and constitute their main prey, it is unlikely that restricted food resources accounted for the poor recruitment of the 2014/15 year class. In this context, the presence of many yolk-sac larvae and preflexion larvae in the low oxygen concentrations, which have become increasingly prevalent in microtidal estuaries of southwestern Australia due to climate change, is likely to have led to considerable mortality. In most populations throughout its range in southern Australia, A. butcheri spawns in a restricted period between the austral mid-spring and midsummer , with the synchrony achieved through differences in the temperatures that cue spawning at different latitudes, i.e. higher temperature cues at lower and thus warmer latitudes. Spawning occurs earlier, however, in atypical estuaries in which sa-linities and temperatures are high in late winter/spring. Despite experiencing episodic recruitment, A. butcheri sustains substantial populations through maturing early relative to its maximum age, and therefore producing numerous offspring in those few years when spawning conditions are optimal. Episodic recruitment could thus be related to subtle inter-annual differences in environmental conditions during the short spawning periods, with oxygen levels greater than usual a potential key factor. The adaptability of A. butcheri makes this sparid useful in assessing the degree, direction and scale of climate change effects.
... For instance, the abundance and richness of fish are influenced by the physicochemical parameters of the water column. Previous studies (Strydom 2014;Teichert et al. 2017;Young et al. 2018) discuss the influence of temperature and salinity, changing the distribution of fish in the estuary. The salinity results in a distribution in which marine fish are found in the most saline parts of the estuary while freshwater fish are found in the least brackish parts (Akin et al. 2005;Selleslagh and Amara 2008). ...
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Accidents involving economic activities of great impact, such as mining, have caused massive environmental damage. In November 2015, the dam of Fundão, located in the city of Mariana, MG, broke and released 5 × 107 m3 of tailings in the nearby ecosystems, including the Doce River. The physicochemical changes that occurred in the Doce River estuary were analyzed, as well as the trace metal concentrations, both 1 day before and 1 month after the disaster. The analyses of the collected samples (water and sediment) showed changes to the physicochemistry regarding dissolved oxygen, SPM, and temperature (p = 0.008, 0.001, 0.036, respectively). It also detected metals (Fe and Al) in the dissolved fraction beyond the limits recommended by the Brazilian legislation. There was an increase in the total concentrations of Fe and Cd in the sediment after the rupture of the dam and a change in mobile metals (Al, Cd, Cr, Cu, Fe, Ni, Pb, and Zn), with higher concentrations of mobile metals being found closer to the ocean (p = 0.06356). After the rupture of the dam, there was a change in the granulometric fraction of the sediment, which became composed mainly of silt and clay. All of the results showed a change on the Doce River estuary, caused by the arrival of the tailings, which can result in future harmful effects with the release of metals present in the sediment and adsorbed to the particles. The changes to the sediment, such as changes in the granulometric fraction, can have negative consequences for the benthic community.
... Taking into consideration the multiple potential environmental impacts, it is critical to study estuarine biodiversity and its dynamics at different scales to understand their processes and mechanisms (Duque et al. 2018;França et al. 2011;Sheaves and Johnston 2009;Teichert et al. 2017;Vilar et al. 2013), as well as to elucidate the effects of eutrophication in these ecosystems. Species richness, abundance, and fish biomass can be measured to assess the effect of variations in nutrient concentrations in the ecosystem. ...
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In tropical estuaries, fish diversity varies spatially and temporally due to behavioral processes such as reproductive migrations, predator avoidance, and foraging, which are affected by water quality. Eutrophication is one of the main factors affecting water quality in estuaries. The objective of this study was to determine variation in fish assemblage explained by fluctuating water quality in the Buenaventura Bay. Fish were captured using artisanal trawl nets during the wet, dry, and transitional seasons at four sampling sites. Additionally, alkalinity; phosphate, nitrite, and nitrate concentrations; dissolved oxygen; pH; temperature; and suspended solids were measured. Multivariate analysis was used to assess the effect of water quality on fish assemblage. In Buenaventura Bay, the assemblage composition of Pseudupeneus grandisquamis, Daector dowi, and Citharichthys gilberti was affected by nitrate concentration. Moreover, large fish biomasses were associated with high nitrite concentration, intermediate salinity, and low dissolved oxygen, suggesting that these estuaries are dominated by species tolerant to poor water quality. Species richness was associated with low nitrate and phosphate concentrations, more suitable water quality indicators, and intermediate temperatures. These results suggest that the deteriorating water quality of estuaries as a result of the anthropogenic impact could increase dominance and decrease richness, resulting in structural changes of fish assemblages.
... The life history of fish consist of physiological changes influenced by environmental stressors, which affect the allostatic load, the energetic cost to mount the stress response, in order to promote conditions to overcome challenges, including immunological challenges, and increase survival (Wilber et al. 2016;Teichert et al. 2017;Abdel-Tawwab et al. 2019). In production systems, fish undergo different situations of acute stress, including capture, air exposure, transportation, confinement, and changes in water quality. ...
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Fish metabolic allostatic dynamics, when animal present physiological modifications that can be strategies to survive, are important for promoting changes to ensure whole body self-protection and survival in chronic states of stress. To determine the impact of sequential stressors on pacu (Piaractus mesopotamicus), fish were subjected to two trials of stressful treatments, administration of exogenous dietary cortisol, and parasite challenge. The first experiment consisted of a two-day acute stress trial and the second, an eight-day chronic stress trial, and after both experiments, fish parasite susceptibility was assessed with the ectoparasite Dolops carvalhoi challenge. Physiological changes in response to acute trial were observed in glycogen, cortisol, glucose, osmolarity, sodium, calcium, chloride, potassium, hematocrit, hemoglobin, red blood cells and mean corpuscular volume, and white blood cell (P < 0.05), whereas response to chronic trial were observed in glycogen, osmolarity, potassium, calcium, chloride, mean corpuscular volume, white blood cell, neutrophil, and lymphocyte (P < 0.05). Acute trials caused physiological changes, however those changes did not induce the consumption of hepatic glycogen. Chronic stress caused physiological changes that induced hepatic glycogen consumption. Under acute trial, stress experience was important to fish to achieve homeostasis after chronic stress. Changes were important to modulate the response to stressor, improve body health status, and overcome the extra stressor with D. carvalhoi challenge. The experiments demonstrate that pacu initiate strategic self-protective metabolic dynamics in acute states of stress that ensure the maintenance of important life processes in front of sequential stressors.
... Correlations between biological fish traits and environmental parameters, e.g. salinity and human disturbances, have been identified (Keck et al., 2014;Pecuchet et al., 2016;Teichert et al., 2017;Beukhof et al., 2019) and morphological fish traits have been linked to the structural complexity of stream habitats in Brazil (Ribeiro et al., 2016). ...
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Coastal habitats are used by a great variety of organisms during some or all stages of their life cycle. When assessing the link between biological communities and their environment, most studies focus on environmental gradients, whereas the comparison between multiple habitats is rarely considered. Consequently, trait-based aspects of biodiversity in and between habitats have received little attention. Here, we use the biological trait approach in addition to the more common species-based approach to examine trait and taxonomic diversity and composition of invertebrate and fish communities in different coastal habitats, common in the northern Baltic Sea. The habitats include bladderwrack (Fucus), seagrass (Zostera), rock with associated algal species (Rock), and bare sand (Sand). We found distinct differences in community diversity and composition between the habitats. For invertebrates, the sediment of the seagrass meadow had the highest taxonomic and trait richness and diversity, whereas Sand had the highest for fish. The highest dissimilarity in invertebrate community composition was between epifaunal (Rock, Fucus, Zostera Epifauna) and infaunal habitats (Sand, Zostera Infauna) on the one hand, and between vegetated (Zostera Infauna) and unvegetated sediments (Sand) on the other hand, emphasizing the major role vegetation plays in structuring communities. We demonstrate that fish community composition is distinct based on species, and to a lesser degree also distinct based on traits, in the different studied habitats. Both invertebrate and fish communities were more similar on a trait level than taxonomically among the habitats highlighting the presence of similar trait identities in the different habitats. Among the traits examined, Body size contributed most to dissimilarities among habitats for both invertebrates and fish, pointing out the ecological importance of body size for differentiating trait composition of communities. Based on our assessment of biodiversity, using the biological trait approach parallel to the taxonomic approach, we show that trait-based measures clearly provide additional information, such as key functions present in a habitat. This aspect cannot be captured by solely using taxonomic indices, which only shed light on diversity from a species identity point of view. Consequently, to include the ecological role of species, we recommend using biological traits in addition to species-based measures in the assessment of biodiversity, and especially in the management and conservation of coastal habitats, given the important ecosystem goods and services these areas provide.
... Natural nearshore ecosystems are threatened worldwide by coastal development and degradation (Schmitter-Soto et al. 2017). The habitats within these systems play a crucial role as nursery habitats for fish and invertebrates due to their high primary and secondary productivity as well as structural complexity (Beck et al. 2001;Sathirathai and Barbier 2001;Nagelkerken et al. 2008;Teichert et al. 2017). The loss of these habitats worldwide -50% of salt marshes (Brown 2006), 35% of mangroves (Valiela et al. 2001), 29% of seagrass meadows (Orth et al. 2006), and 85% of oyster reefs (Beck et al. 2011) -has directly impacted productivity and recovery of fish populations (Lotze et al. 2006;Barbier et al. 2011;Halpern et al. 2012;Schmitter-Soto et al. 2017). ...
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Coastal habitats are threatened worldwide by habitat loss and degradation. These habitats play a crucial role as fish nurseries. Unfortunately, it is difficult to determine the impact of habitat degradation for many species because data are lacking on early life history metrics including growth (0.07 ± 0.04 SE mm/day in this study), survival (apparent annual survival 0.007 (95% CI: 0.001–0.033 in this study), emigration (27% in this study) and the spatial extent and condition of these habitats. The juvenile life stage of Atlantic tarpon (Megalops atlanticus), an economically important species in the Caribbean, sub-tropical and tropical Atlantic, and Gulf of Mexico, depends upon wetlands and marshes. A mark-recapture study designed to measure juvenile tarpon growth in an altered mangrove habitat in Florida (USA) found that juvenile tarpon exhibited slow growth and emigrated at small sizes. The low scores on these metrics, in combination with a broad knowledge gap on the extent and condition of juvenile tarpon habitats in Florida, caused concern about the conservation prospects for tarpon and the fishery it supports. To provide information necessary to formulating an effective conservation plan for tarpon, we used citizen science to identify juvenile tarpon habitats and to characterize them as natural or altered (a first-level measure of direct, physical habitat change). A comparison of angler reports and habitat assessments with scientific field assessments showed that using anglers is an efficient and effective means of identifying juvenile tarpon habitats and providing a first-level assessment of habitat condition. This study provides a baseline for ongoing and future habitat conservation and restoration efforts for juvenile tarpon and other species that also use these habitats as nurseries.
... Beam trawl surveys have been carried out since 2005 in the transitional waters of metropolitan France to assess their ecological status as required under the European Water Framework Directive 2000/60/EC (Delpech et al., 2010 ;Teichert et al., 2017). The transitional waters include mainly estuaries of the Atlantic and the Channel coasts. ...
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A null model to account for the species tolerance to salinity. (PDF)
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The trade-off between current and future reproduction remains a central issue for understanding the diversity of fish life-histories along a slow-fast continuum. Fish living in rivers of tropical oceanic islands generally have a fast type life-history, but variations in key reproductive traits can occur in response to spatial changes in selection pressures. Here, we investigated the reproductive strategies of two sympatric amphidromous gobies widely distributed in Caribbean streams, Sicydium plumieri (n = 308) and Sicydium punctatum (n = 383), along a river gradient of Guadeloupe Island. Beyond the new insights provided on the reproductive traits (ovarian organization, gonadal development, length at maturity, and spawning season), the histological observations of testes and ovaries revealed variation in reproductive strategies. Sicydium punctatum showed a time-minimizing strategy, featuring early reproduction, a high spawning frequency, an extended reproductive period, and a broad spawning area along the river course. Sicydium plumieri displayed a size-maximizing strategy, featuring a delayed maturity, lower spawning frequency, and a shorter reproductive period restricted to the upper reaches of rivers. We discuss the advantages provided by these two strategies in response to the spatial changes in predation and disturbance levels along the upstream–downstream continuum, which probably affects the survival rate and mortality risk before the first reproduction.
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Estuarine zonation and community assemblages are frequently correlated with salinity, although the extent or nature of this correlation varies considerably among the published studies. While a smooth transition in biological communities is often conceptualized in association with estuarine fresh, brackish, and marine conditions, many studies have shown more distinct communities and the altogether absence of a brackish community. We explore these viewpoints in light of plant observations and soil and aquatic microbial analyses from permanent plots established on the Elbe River Estuary of northern Germany. Generally, two distinct communities were observed, a polyhaline assemblage towards the mouth of the system, and another that was associated with both the fresh and brackish mesohaline regimes further upriver. This was most pronounced among plant and soil bacteria communities, while aquatic 16S assemblages reflected little distinction at all. The proportion of marine classified taxa declined from the mouth to upriver and suggests that while the transition from marine to brackish or fresh vegetation falls within the sampled area, the same transition for microbial taxa could not be observed and may be further upriver. Thus, although we were able to identify two distinct communities, the “limit” of marine taxa was only evident for vegetation. While tidal and weather-related hydrology, as well as soil properties were also influential in distinguishing the communities, much of the variance remains unexplained. Further sampling, classification, and partitioning is necessary to determine the origin and/or autochthonous habitat, if any, for the Elbe River estuarine taxa. Geographic bounds bottom left: 53.556216°N, 8.824398°E top right: 53.917760 °N, 10.155669 °E
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Coastal and estuarine environments are under endogenic and exogenic pressures jeopardizing survival and diversity of inhabiting biota. Information of possible synergistic effects of multiple (a)biotic stressors and holobiont interaction are largely missing in the Elbe estuary but are of importance to estimate unforeseen effects on animals’ physiology. Here, we seek to leverage host-transcriptional RNA-seq and gill mucus microbial 16S rRNA metabarcoding data coupled with physiological and abiotic measurements in a network analysis approach to deconvolute the impact of multiple stressors on the health of juvenile Sander lucioperca along one of the largest European estuaries. We find mesohaline areas characterized by gill tissue specific transcriptional responses matching osmosensing and tissue remodeling. Liver transcriptomes instead emphasized that zander from highly turbid areas were undergoing starvation which was supported by compromised body condition. Potential pathogenic bacteria, including Shewanella , Acinetobacter , Aeromonas and Chryseobacterium , dominated the gill microbiome along the freshwater transition and oxygen minimum zone. Their occurrence coincided with a strong adaptive and innate transcriptional immune response in host gill and enhanced energy demand in liver tissue supporting their potential pathogenicity. Overall, we demonstrate the information gain from integration of omics data into biomonitoring of fish and point out bacterial species with disease potential.
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Brackish water ecosystems often have high primary production, intermediate salinities, and fluctuating physical conditions and therefore provide challenging environments for many of their inhabitants. This is especially true of the Baltic Sea, which is a large body of brackish water under strong anthropogenic influence. One freshwater species that is able to cope under these conditions in the northern Baltic Sea is the vendace (Coregonus albula), a small salmonid fish. Here, we review the current knowledge of its ecology and fishery in this brackish water environment. The literature shows that, by competing for resources with other planktivores and being an important prey for a range of larger species, C. albula plays a notable role in the northern Baltic Sea ecosystem. It also sustains significant fisheries in the coastal waters of Sweden and Finland. We identify the need to better understand these C. albula populations in terms of the predator–prey interactions, distributions of anadromous and sea spawning populations and other putative (eco)morphs, extent of gene exchange between the populations, and effects of climate change on their future. In this regard, we recommend strengthening C. albula‐related research and management efforts by improved collaboration and coordination between research institutions, other governmental agencies, and fishers, as well as by harmonization of fishery policies across national borders.
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Responses to lunar cycles vary amongst taxonomically distinct marine creatures. We calculated larval fish diversity and density over four successive lunar phases: new, first quarter, third quarter, and full. A bongo net with a mesh size of 300µm mesh size from a tropical nearshore water of the Straits of Malacca, Malaysia. We collected 5,305 fish larvae from 27 different families. Diversity indices for richness (Shannon-Wiener, H), dominance (Simpson, D) and evenness (Pielou, E) decreased from the full lunar phase onwards. Larval density, on the other hand, was much higher during the new lunar phase. We also determined that the larval fish family was either selectively present during each lunar phase or had a peak density during full and new moons. The larval fish assemblages revealed a preference for spawning events during the lunar phases. Human activities in the vicinity area are advised to be minimised during this period to mitigate harmful influence on larval fish recruitment in the nearshore area.
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Small-scale sector fisheries associated with tropical wetland were found to be highly vulnerable to various socio-economic, ecological and climatic factors. The present study conducted in Vembanad lake in India attempted to identify and assess vulnerabilities of wetland fishers to climate variability at spatial scale. One hundred and eighty fishers distributed across three villages (Vaikkom, Muhamma and Thycattussery) who were representative of marine, freshwater and brackish water fishers, respectively, were surveyed based on a structured schedule prepared by National Innovations for Climate Resilient Agriculture and ICAR-Central Inland Fisheries Research Institute. Potential indicators of vulnerability as perceived from survey were segregated under seven drivers such as health, livelihood, social, food, ecological, resource and resource user. These indicators which were represented by attributes were scored, based on fishers’ perception, and were used for identifying the highly contributing drivers of vulnerabilities. Kruskal–Wallis parametric test was used for analyzing the vulnerabilities statistically. The overall wetland vulnerability indices derived from various villages indicated that Thycattussery was highly vulnerable compared to Muhamma and Vaikkom. A transactional analysis across each sampling station indicated that in Vaikkom, fishers were less vulnerable to resource, food security and resource user vulnerabilities in a climate changing context. Poor status of livelihood, social and food related insecurities and resource user-based uncertainties were the factors attributing to fishers' vulnerability in Thycattussery. The fishers of Muhamma experienced greater ecological and resource-based vulnerabilities. The study suggested that a bottom-up approach involving the primary stakeholders (fishers) along with the community will adequately position them to climate change adaptation and mitigation.
Article
In a large river with significant environmental variations in space (i.e., microhabitat) or over time (i.e., seasonality and/or long‐term trend), discovering the spatial changes in fish diversity, distributions, and functional traits would provide an important foundation for the understanding of ecosystem structure and function. In the Pearl River in China, three datasets as fish distribution, species functional traits, and environmental variables were constructed and sorted to (1) test the relationships between and congruence of taxonomic diversity, functional diversity, and phylogenetic diversity by a randomisation procedure, (2) map the spatial pattern of diversity and the correlation to environmental variables by maximal information coefficient, and (3) determine the fish traits tendency under environmental changes by the fourth‐corner method. The Pearl River possesses the highest fish richness among all the rivers in China, with 438 freshwater fish species including 119 cave species. At basin scale, phylogenetic diversity showed faster change than functional diversity, suggesting a little divergence of functional traits despite high phenotypic or genetic diversity across species, as parallel evolution. However, at a small scale, when only considering cave fishes, the variation rate of species traits was faster than that of species increase, as evolutionary radiation in a variety of microhabitats. For all three aspects of diversity, random permutation tests confirmed that congruence values in each grid cell were significantly different from the random expectations. Besides widely accepted variables such as altitude, precipitation, and slope concerned with fish biogeography, hydrochemical variables showed influential impacts on the morphological and growth traits of fishes in the Pearl River characterised by the dominance of the karst habitat.
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Estuaries are important fish nursery areas, yet little is known of how environmental forcing influences estuarine fishes during their early life stages. We analyzed environmental and larval-juvenile fish community data in the upper San Francisco Estuary (SFE) from spring to early-summer 1995 ̶ 2017, to better understand drivers of spatiotemporal community patterns in this highly modified estuary. We evaluated community patterns based on the relative abundance and diversity of native and introduced fish in the SFE and their predominant distribution (pelagic, demersal). The upper SFE experienced downward trend of freshwater outflow and upward trends of temperature and salinity intrusion. Fish relative abundance only showed long-term downtrends for native and introduced pelagic fish groups. The most influential habitat components for relative abundance and diversity of fish groups were in decreasing order: temperature, salinity, Secchi depth, bottom depth, and zooplankton biomass. Early life stages of native and introduced fishes were generally segregated spatially and temporally, with native fishes more associated with cooler, saltier and higher turbidity habitats during early-to mid-spring compared to introduced fishes during late spring to early summer. Community ordination showed that environmental (temperature, salinity, outflow, Secchi depth, and zooplankton biomass) and spatiotemporal factors (month and depth), explained nearly 40% of the total variance. Our results suggest that the shorter duration of planktonic and nektonic stages of demersal fish groups results in higher resiliency compared to pelagic fishes. Declining abundance of pelagic fishes overall seem to be linked to drought effects and human-induced synergistic interactions intensified by climate change.
Article
Estuaries are one of the most important ecosystems with high biological productivity. They connect freshwater and marine ecosystems, and the fish community assemblages face intense environmental changes, so estuarine fish communities have unique ecological characteristics. With the increase of human activities and the discharge of pollutants, the pressure on the ecosystem of the Pearl River Estuary (PRE) is intensifying, and its ecosystem functions and services are inevitably affected. To better understand the functional structure of the fish community in the PRE and its response to environmental changes, we analyzed the trait composition of the community and its relationships to environmental factors based on 10 functional traits of 130 fish species collected in the PRE during the summer and winter of 2020–2021. In addition, we built a multi-dimensional functional space to visualize the overall functional structure of the PRE and explore the seasonal variation of the selected traits in the functional space. Our findings suggest that the functional traits of the fish communities in the PRE were mainly affected by temperature, dissolved oxygen, chlorophyll-a, and depth. Among them, the effects of dissolved oxygen, temperature, and chlorophyll-a on CWM traits were reflected in seasonal differences, while the effects of depth were reflected in spatial differences. We also found the main trait categories that occupied the most functional space and contributed the most to the seasonal differences in functional space. The results of this study are significant for understanding the seasonal variation of the functional structure in the PRE and how environmental gradients drive the functional traits of fish communities, and also provide insights for effective ecosystem-based management in the PRE.
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Estuaries are the main entry areas of mercury to the marine environment and are important to understand the effect of this contaminant on marine organisms, since it accumulates in the sediments becoming available to enter the food trophic chain. This study aims to determine the environmental variables that mainly influence the spatiotemporal dynamics of total mercury accumulation in sediments of tropical estuaries. Sediment samples were collected from interior and exterior areas of the estuary during the dry and rainy seasons, representing the spatiotemporal gradients of the estuary. The grain size, organic matter content (OM), and total mercury concentration (THg) of the sediment samples were determined. In addition, salinity, temperature, dissolved oxygen, and pH of the water column associated with each sediment sample were assessed. The variations in environmental conditions, OM and THg in sediment were in accordance with a gradient which goes from conditions influenced by fresh water in the inner estuary to conditions influenced by sea water in the outer part of the estuary. The OM and THg in sediments presented similar variation patterns; they were higher in the rainy season than in the dry season and in the interior area of the estuary than in the exterior area. Despite the complex dynamic observed in the distribution and accumulation processes of mercury in sediments, these processes could be modeled from OM and salinity parameters. Due to the correlations found, in the process of accumulation of mercury in sediments the OM could represents the pathway of transport and accumulation of THg, and salinity could represent the influence of the hydroclimatic variations and environmental gradients of the estuary.
Chapter
This chapter synthesises the current knowledge and future directions of research into estuarine fish, their habitats and the estuarine fisheries. It also aims to present the main lessons for our current and future understanding of fish in estuaries. There is a focus on developing an understanding of the socioecological system by considering the relationship between the organisms and their environment, and fish tolerance of environmental master factors. It covers the current ideas on ecosystem structure and functioning, such as growth, productivity, competitive interactions and predator‐prey relationships. A knowledge of these then leads to an understanding of the estuarine ecosystem services, for example the delivery of fish which can be exploited and ensuring clean water and nutrient and carbon cycling. These services in turn lead to the creation and exploitation of estuarine goods and benefits.
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Shallow coastal habitats are ruled by fluctuating environmental conditions, which lead to shifts in fish communities. Functional groups of habitat use and trophic strategy were used to address the responses of fish composition and diversity, since comparisons of rich tropical systems are often complex through species-based approaches. We hypothesized that fish groups will have specific affinities in response to the prevailing environmental conditions, especially those reflecting the prevalence of oceanic or estuarine conditions, where guilds of habitat use would perform better as indicators. Despite the importance of other environmental factors (i.e. temperature and transparency), salinity was the key structuring factor irrespective of the coastal lagoon. Although harbouring the greatest biomass of piscivores, the harsh environmental conditions at Araruama lagoon were related to low diversity. A great number of indicator species, typically of marine affinity, was found at the Saquarema lagoon, probably due to the continuous and broad connection to the sea leading to the predominance of euhaline conditions. Despite the presence of non-native species (i.e. Oreochromis niloticus), the Maricá lagoon function as an important refuge for freshwater groups. Our results stressed the key role played by coastal lagoons of varied water conditions in supporting fish diversity at regional levels.
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This study evaluated the relative importance of the Narragansett Bay estuary (RI and MA, USA), and associated tidal rivers and coastal lagoons, as nurseries for juvenile winter flounder, Pseudopleuronectes americanus, and summer flounder, Paralichthys dentatus. Winter flounder (WF) and summer flounder (SF) abundance and growth were measured from May to October (2009–2013) and served as indicators for the use and quality of shallow-water habitats (water depth <1.5–3.0 m). These bioindicators were then analyzed with respect to physiochemical conditions to determine the mechanisms underlying intraspecific habitat selection. WF and SF abundances were greatest in late May and June (maximum monthly mean = 4.9 and 0.55 flounder/m2 for WF and SF, respectively) and were significantly higher in the tidal rivers relative to the bay and lagoons. Habitat-related patterns in WF and SF abundance were primarily governed by their preferences for oligohaline (0.1–5 ppt) and mesohaline (6–18 ppt) waters, but also their respective avoidance of hypoxic conditions (<4 mg DO/L) and warm water temperatures (>25 °C). Flounder habitat usage was also positively related to sediment organic content, which may be due to these substrates having sufficiently high prey densities. WF growth rates (mean = 0.25 ± 0.14 mm/day) were negatively correlated with the abundance of conspecifics, whereas SF growth (mean = 1.39 ± 0.46 mm/day) was positively related to temperature and salinity. Also, contrary to expectations, flounder occupied habitats that offered no ostensible advantage in intraspecific growth rates. WF and SF exposed to low salinities in certain rivers likely experienced increased osmoregulatory costs, thereby reducing energy for somatic growth. Low-salinity habitats, however, may benefit flounder by providing refugia from predation or reduced competition with other estuarine fishes and macroinvertebrates. Examining WF and SF abundance and growth across each species’ broader geographic distribution revealed that southern New England habitats may constitute functionally significant nurseries. These results also indicated that juvenile SF have a geographic range extending further north than previously recognized.
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Fish species numbers and surface area of 13 California bays and estuaries and the California continental shelf were positively correlated, and the slope (z) of the log-log regression was 0.21. Mouth width of bays was the only significant variable accounting for variation of species numbers in stepwise multiple regression. Clustering based on presence or absence of fish species produced a southern and a northern group of bays. A two-way table (bay vs. species) distinguished three broad distributional categories of fish species. Comparisons of area and species numbers of Chesapeake Bay and King Harbor (southern California) with those of California bays and estuaries supported the view that the present study has relevance for the preservation and management of bay/estuarine systems.
Book
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For the inhabitants of many of the world’s major cities and towns, estuaries provide their nearest glimpse of a natural habitat; a habitat which, despite the attempts of man to pollute it or reclaim it, has remained a fascinating insight into a natural world where energy is transformed from sunlight into plant material, and then through the steps of a food chain is converted into a rich food supply for birds and fish. The biologist has become interested in estuaries as areas in which to study the responses of animals and plants to severe environmental gradients. Gradients of salinity for example, and the problems of living in turbid water or a muddy substrate, prevent most animal species from the adjacent sea or rivers from entering estuaries. In spite of these problems, life in estuaries can be very abundant because estuarine mud is a rich food supply, which can support a large number of animals with a large total weight and a high annual production. Indeed estuaries have been claimed to be among the most productive natural habitats in the world. When the previous editions of this book appeared, biologists were beginning to realise that the estuarine ecosystem was an ideal habitat in which to observe the processes controlling biological productivity. In the interven¬ing period, several more estuaries and their inhabitants have been studied intensively, and it is now possible to answer many of the questions posed by the earlier edition, and to pursue further the explanation of high productivity in estuaries and of energy utilisation at different trophic levels within the estuarine food web. Users of the previous editions were kind enough to welcome the framework of the book, which first outlined the estuarine environment and the physical and biological factors which are important within it. We then examine the responses of the animals and plants to these factors, consider the problems of life in estuaries and why so few species have adapted to estuaries, and then propose a food web for an estuary. Thereafter we shall examine each trophic level in the food web in turn, first the primary producers (plants and detritus), then the primary consumers (herbivores and detritivores) and finally the secondary consumers (carnivores). These chapters have been fully revised in this third edition, to reflect our latest knowledge in these topics. In the period since the publication of the previous editions of this book, a vast amount of new information on pollution in estuaries has accumulated. It has been widely recognised that although the world’s seas are huge and may appear capable of receiving unlimited quantities of man’s waste, such waste is often discharged first into the confined waters of estuaries. Many international experts have stated that, whilst the open oceans may not be generally polluted, the coastal waters of the sea and especially the waters of estuaries are widely polluted. Thus in practice, marine pollution is often essentially estuarine pollution. To reflect this large impact of mankind on estuaries, and to consider how mankind may either destroy or enrich the estuarine ecosystem, new chapters have been prepared in this edition. These consider pollution in estuaries, and the diverse uses and abuses of the estuarine habitat by man, as well as the methods used to study human induced changes in estuaries and the ways in which estuarine management can either monitor, control or prevent pollution or destruction of the estuarine ecosystem. This latest edition therefore retains the concept of the study of the ecosystem as the basis for our understanding of the natural world, and shows that estuaries are ideal habitats for such studies. The new content and chapters reflect our attempts to recognise both the problems of pollution in estuaries and the solutions which estuarine management can offer, as estuarine ecosystems come under increasing pressure from a wide range of demands made by an increasing world population. The topic of estuarine pollution, estuarine uses and abuses and their management has moved on considerably in the past decade. As many of the problems of “point” source pollution have been attended to, different problems of “diffuse” pollution have become apparent. In addition, while some pollution problems are seen as capable of being solved, habitat loss and degradation is more of a threat. Hence the third edition concentrates on these as well as including sections on the effects of fisheries, dredging, structures, aquaculture, etc. on estuarine ecosystems. The third edition seeks to include considerably more applied material and present case studies of estuarine change. Estuaries can be perceived as either the originators of pollutants, or more often as the recipients of pollution that originate on land, freshwater, or from the sea. The problems of estuarine pollution and management are those dealing with a sheltered environment that acts as a trap for sediment and contaminants, and as areas subject to intense pressure from mankind’s activities such as land-claim (or reclamation). Estuaries are the most protected habitat in the UK and elsewhere (measured as the percentage of the total habitat that is subject to protection orders), and for most students on aquatic biology are their most accessible marine habitat. Whilst few UK, European or American Universities have ships for access to the sea, many are located on the shores of estuaries. Thus for many University courses, their local estuary is the marine habitat which can be studied, whilst the open seas have to be studied only in films or video. Throughout the book examples are drawn from Britain, Europe and America, as well as other areas which have been well studied such as South Africa and Australia.
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Marine sediments provide the largest habitat on planet earth, yet knowledge of the structure and function of their flora and fauna continues to be poorly described in current textbooks. This concise, readable introduction to benthic ecology builds upon the strengths of the previous edition but has been thoroughly revised throughout to incorporate the new technologies and methods that have allowed a rapid and ongoing development of the field. It explores the relationship between community structure and function, and the selection of global examples ensures an international appeal and relevance. The economic value of marine sediments increases daily, reflected in the text with a new emphasis on the effects of pollution and fisheries and the management of marine sediments. This accessible textbook is suitable for both advanced undergraduate and graduate students who have had a general ecology course, but no further training in benthic ecology. It will also be of relevance and use to professional researchers and consultants in marine ecology and environmental science who seek a compact but comprehensive introduction to benthic ecology.