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Behavior and space utilization of two common fishes within Caribbean mangroves: implications for the protective function of mangrove habitats
Abstract
Behaviors, activity budgets, and spatial locations of reef-associated schoolmaster snapper (Lutjanus apodus) and non-reef-associated checkered puffer (Sphoeroides testudineus) were cataloged in mangrove forests in Caribbean Honduras to see how and where they spent their time and whether this changed as they grew. For schoolmasters, swimming was the most common behavior, while checkered puffers spent the majority of their time resting. Both remained completely within (as opposed to outside) the mangrove roots and in the lower half of the water column most of the time. However, as the size of the fish increased there was a clear decrease in the time spent both within the root system and closer to the substrate; the larger fish spent more time higher up in the water column and outside the root system. This was observed in both the schoolmaster and the puffer; the schoolmaster subsequently moves to reefs while the puffer does not. Coupled with limited feeding, the results suggest a primarily protective function for mangroves.
... For example, it is estimated that 80% of global commercial fish catches rely directly or indirectly on mangrove systems (Sandilyan and Katherisan, 2012). Given that many aquatic prey species rely on the physical complexity of the mangrove ecosystem for protection from predators (Buchan, 2000;MacDonald et al., 2009), destruction of mangrove communities may influence the stress physiology of these prey species. ...
... This was accomplished by examining the baseline and stressinduced changes in glucose and cortisol concentrations of fish placed in artificial environments in which substrate type and the presence of mangrove roots and predator cues were manipulated. The checkered puffer (Sphoeroides testudineus) was chosen as a model species because of its wide distribution, ease of capture, and abundance in mangrove communities (MacDonald et al., 2009;Shipp, 1974). Checkered puffers are thought to rely heavily on mangrove habitats for protection from predators (MacDonald et al., 2009), sheltering in the roots and blending in with the heterogeneous substrate using their cryptic dorsal colouration (Austin and Austin, 1971;Targett, 1978). ...
... The checkered puffer (Sphoeroides testudineus) was chosen as a model species because of its wide distribution, ease of capture, and abundance in mangrove communities (MacDonald et al., 2009;Shipp, 1974). Checkered puffers are thought to rely heavily on mangrove habitats for protection from predators (MacDonald et al., 2009), sheltering in the roots and blending in with the heterogeneous substrate using their cryptic dorsal colouration (Austin and Austin, 1971;Targett, 1978). Therefore, we hypothesized that homogeneous substrate, the absence of mangrove roots, and the presence of predator cues would result in higher baseline and post-stress glucose and cortisol concentrations in the puffers as well as a magnified physiological stress response. ...
... Observer effects are expected to be negligible as focal fish routinely approached within 5m of the observer with no apparent affects (such as sharp changes in feeding or swimming). As non-herbivorous coral reef fish exhibit relatively constant rates of feeding and swimming throughout the day (Fulton 2007, MacDonald et al. 2009), this small observation window, repeated multiple times for each species and colour phase, is expected to provide an adequate representation of diurnal time budgets during routine foraging for these species. Observations were conducted throughout the hours 0800-1600, with randomisation of filming of individuals of each species and site to homogenise any tidal or diurnal effects across sample observations. ...
... In the three species examined here, steady swimming accounted for approximately 75-98% of their activity budgets. This is congruent with the findings of previous field studies, demonstrating very high incidences of swimming behaviour in reef fishes (Fulton & Bellwood 2002, Lowe 2002, Verweij et al. 2006, MacDonald et al. 2009). Interestingly, this is in distinct opposition to most studies of activity budgets in terrestrial animals (including birds), where locomotory behaviour is in fact a relatively uncommon behaviour (Tatner & Bryant 1986, Kenagy & Holt 1989, Kuntz et al. 2006, Talebi & Lee 2010. ...
... Despite occurring frequently, the very short duration (~0.01s sensu Westneat 1994) of feeding reduces this category to a minor component of the time budget. Such underestimation of feeding activity has been highlighted in several activity budget studies of fish (Polunin & Klump 1989, Verweij et al. 2006, MacDonald et al. 2009). ...
Estimates of the energetic costs associated with locomotion in free-living animals are difficult to find for aquatic animals. This is largely due to the technical difficulties of applying methods commonly used for air-breathing terrestrial taxa (e.g. doubly-labelled water) to aquatic environments. Consequently, there is a paucity of information on the activity costs of free-living fishes. Preliminary indications are that swimming can be a significant energetic expense for fishes. Swimming may therefore affect the allocation of metabolic energy to other fundamental functions such as growth, reproduction and cellular maintenance and thus is expected to be significant target for natural selection. However, without quantitative information on either the time or energy budgets associated with field swimming behaviours, we are unable to explore this further. In this study I observed both similarities and differences in the swimming activity during foraging of three species of coral reef wrasses. Regardless if measured in terms of time or frequency of events, all three species allocated most of their time to steady swimming (75-98% of total time). Searching and feeding were also prominent behaviours, with the extent varying across species with different feeding ecologies (benthic macrocarnivore, benthic microcarnivore and planktivore). Antagonism also varied across and within species, possibly as a consequence of the varying territoriality among species. When combined with the observed differences in field swimming speeds among species, it appears that wrasses vary their activity budgets according to their particularly trophic ecology and social structure. Combining the field observations of swimming behaviour with lab-based measures of the cost of swimming yielded estimates of the aerobic costs associated with locomotor activity by these wrasses. Such estimates of activity cost varied approximately seven-fold across species. Comparing our results with the limited current data available for field activity costs in other fishes, Stethojulis bandanensis appears to have the highest mass-specific activity cost reported for a fish to date. More broadly, it appears that my estimates for these ectothermic species are well below those for locomotor activity costs calculated for a range of endothermic taxa. Estimating and validating field activity costs in free-living fishes is still a challenge. Moreover, placing these estimates of activity cost within a broader context of field energetics is hindered by a lack of consistency in how values are reported in the literature. A convention on a common currency of costs would greatly facilitate future comparative analyses of field energetics, both within and across taxa from aquatic and terrestrial realms.
... The higher consumption of such preys is presumably related to their availability in the estuary and often within the mangrove canopy. The dominance of carnivorous over other groups has been reported in estuaries in temperate latitudes (Sá et al. 2006), in Caribbean mangroves (McDonald et al. 2009) and in demersal fish assemblages of coastal areas (Abdurahiman et al. 2010). ...
... Acurate vision and prey attacking techniques are two factors considered important when capturing very active swimming organisms such as fishes and shrimps (Hajisamae 2009), which were items with higher frequency of occurrence in the diet of the studied species. The presence of piscivorous along the estuaries, especially in the mangroves, may be related to the fact that the spatial heterogeneity created by the mangrove roots provides a suitable place to stay in ambush (McDonald et al. 2009). ...
The current work investigates dietary overlap and food partitioning among nine abundant carnivorous fishes caught in the shallow waters of the Paraíba do Norte river estuary, Paraíba State, Brazil. Fishes were sampled with a beach seine net between January and December 2008 and a total of 958 specimens had their stomach content analyzed. Crustacea was the dominant food resource for Lutjanus alexandrei, L. jocu and Bathygobius soporator, whereas Telostei were consumed mainly by Centropomus undecimalis and C. parallelus. In contrast, Polychaeta were preyed upon mainly by Diapterus rhombeus, Eucinostomus argenteus, Sciades herzbergii and S. parkeri. Although most species consumed similar food items, they did that in varying proportions and amounts. Overall, the niche overlap among species was low (< 0.60), but there were several cases where pair of species had their feeding niche highly overlapped (between 0.72 and 0.97). These findings corroborate the hypothesis that food resource partitioning determines species coexistence in estuarine tropical environments.
... Mangrove roots can be characterized on the basis of various structural properties, but so far very few studies have tested the role of these properties experimentally. Examples include those that tested the effect of root epibiont complexity (MacDonald et al., 2008), degree of shading (Cocheret de la Morinière et al., 2004;Verweij et al., 2006a), root density (Cocheret de la Morinière et al., 2004;MacDonald et al., 2009), and presence of decomposing leaves (Rajendran and Kathiresan, 1999) on fish communities. Equally few studies have assessed the effect that newly introduced complexity, such as in newly planted mangroves, has on fish or other marine communities (Bosire et al., 2004;Huxham et al., 2004;Bosire et al., 2008). ...
... observ.). Conversely, the demersal L. apodus is typically known to seek shelter in-between hanging prop-roots higher up in the water column at the size observed in the present study (MacDonald et al., 2009). ...
Benthic structure plays an important role as shelter and feeding habitat for demersal fauna. While many studies have investigated the relationship between structural complexity of aquatic vegetation and the number of species or abundance of motile organisms, little is known of the attractiveness of submerged mangrove roots. We tested the importance of various root attributes in attracting fish species in a field experiment using different artificial mangrove units (AMUs) with PVC pipes mimicking roots to exclude interaction with other environmental and biotic factors. We manipulated length, vertical orientation, and three-dimensional structural complexity of root mimics in the AMUs to explore their effects on the fish community variables: fish abundance, number of species and community composition. Pipe length and three-dimensional structure did not have an effect on fish community variables. Vertical pipe orientation had a significant effect and AMUs with standing pipes showed higher total fish abundances and number of species than AMUs with hanging pipes. Also community composition differed greatly between AMUs with standing versus hanging pipes. At species level, demersal fish species mainly occupied AMUs with standing pipes and occurred only at very low abundances when hanging pipes dominated in the AMUs; in contrast, the semi-pelagic swimmer Sphyraena barracuda showed a trend of higher abundance in AMUs with mainly hanging pipes. When analyzed across all AMUs, fish abundances of demersal as well as semi-pelagic species decreased significantly with increasing interspatial pipe distance among AMUs, suggesting that distance to refuge may be the underlying mechanism for the observed patterns. The above findings are important in the context of the worldwide degradation of mangroves, because human alteration to mangrove vegetation affects its structure and thus composition and size of fish communities.
... Kamal et al. (2014) found a relationship between body shape of fishes and mangrove root height, and demonstrated that small fishes have more space to manoeuvre among the roots than larger fishes. Others have reported that the percentage of time spent within the roots decreases as the individual size increases (MacDonald et al. 2009;Ochoa-Gómez et al. 2018). Therefore, several studies conducted in mangrove root structure suggest a relationship between mangrove habitat complexity and fish distribution patterns (Ley et al. 1999;Verweij et al. 2006;Muzaki et al. 2019). ...
Shallow estuarine habitats are well recognized for providing a positive correlation to the abundance and diversity of juvenile fish species. This has been associated with the hypotheses of refuge from predators and the availability of food. Therefore, this study aimed to evaluate the importance of two adjacent habitats to mangrove fringes (area adjacent to pneumatophore zone and mudflat) as an ecological habitat for Diapterus auratus juveniles. Sampling was carried out in the rainy (January–July 2016) and dry (August–December 2016) periods. This study indicated that D. auratus juveniles did not show significant differences in abundance and biomass between adjacent habitats. However, univariate analyses found there was a significant increase in fish abundance in the dry season, due to influx of young-of-the-year. Further, the size-frequency of D. auratus showed a recruitment pattern recorded between August and January, suggesting a broad spawning period between the end of the rainy season and a recovery period between March and May. There were distinct changes in the diet between seasons for D. auratus, according to the dendrogram of the food eaten by the fish. The combined results from the distribution and feeding ecology suggest a connectivity among adjacent areas, and indicate that both habitats provide critical foraging and refuge habitat for D. auratus in this tropical estuary.
... S. testudineus (also known as checkered puffer) was chosen in the present work for several reasons: (1) its high abundance in tropical nvironments; (2) it had already proven to be very useful as a Hg bioindicator [79]; (3) in juvenile stage, the species tends to orient towards the substrate for feeding and defense, being in close contact with the contaminated sediment particles; and (4) they are intermediate predators in the estuarine food chain [80,81]. Juvenile S. testudineus (n = 15) were collected in Ceará River estuary (3 • 42 S; 38 • 36 W) and in a reference site, Pacoti River estuary (3 • 49 S; 38 • 25 W), using a hand-operated trawl net during low tide. ...
Due to global warming, in the northeastern semiarid coastal regions of Brazil, regional and global drivers are responsible for decreasing continental runoff and increasing estuarine water residence time, which promotes a greater mobilization of bioavailable mercury (Hg) and allows increasing fluxes and/or bioavailability of this toxic trace element and an acceleration of biogeochemical transformation of Hg. In this work, an application of dendrochemistry analysis (annular tree rings analysis) was developed for the reconstruction of the historical pattern of mercury contamination in a contaminated area, quantifying chronological Hg contamination trends in a tropical semiarid ecosystem (Ceará River Estuary, northeastern coast of Brazil) through registration of mercury concentration on growth rings in specimens of Rhizophora mangle L. and using the assessment in sediments as a support for the comparison of profiles of contamination. The comparison with sediments from the same place lends credibility to this type of analysis, as well as the relationship to the historical profile of contamination in the region, when compared with local data about industries and ecological situation of sampling sites. In order to evaluate the consequences of the described increase in Hg bioavailability and bioaccumulation in aquatic biota, and to assess the biological significance of Hg concentrations in sediments to fish and wildlife, muscle and liver from a bioindicator fish species, S. testudineus, were also analyzed. The results of this work reinforce the indicators previously described in the semiarid NE region of Brazil, which showed that global climate change and some anthropogenic factors are key drivers of Hg exposure and biomagnification for wildlife and humans. Considering the Hg concentration present in the top layers of sediment (~20 cm around 15 to 20 years) with the outer layers in the tree ring cores and in the sediment’s cores from Pacoti estuary and the Ceará estuary, overall the data indicate an increase in mercury in recent years in the Hg surface sediments, especially associated with the fine sediment fraction, mainly due to the increased capacity of small particles to adsorb Hg. There was revealed a positive and significant correlation (p < 0.05) between Hg trends in sediments and Hg trends in annular tree rings. This shared Hg pattern reflects local environmental conditions. The Hg concentration values in S. testudineus from both study areas are not restrictive to human consumption, being below the legislated European limit for Hg in foodstuffs. The results from S. testudineus muscles analysis suggest a significant and linear increase in Hg burden with increasing fish length, indicating that the specimens are accumulating Hg as they grow. The results from both rivers show an increase in BSAF with fish growth. The [Hg] liver/[Hg] muscles ratio >1, which indicates that the S. testudineus from both study areas are experiencing an increase in Hg bioavailability. Possible climate-induced shifts in these aquatic systems processes are inducing a greater mobilization of bioavailable Hg, which could allow an acceleration of the biogeochemical transformation of Hg.
... Juvenile Schoolmaster snapper (Lutjanus apodus; hereafter referred to simply as snapper) is a common tropical fish species frequently found in shallow estuaries and back reef ecosystems (Laegdsgaard and Johnson, 2001;Luo et al., 2009;Mateo et al., 2010). Given their high abundance they are also a food source for a variety of marine predators (MacDonald et al., 2009;Mateo et al., 2010;Serafy et al., 2015). Snapper appear to target similar prey to lionfish, small fish and crustaceans (Morris and Akins, 2009;Côté and Maljković, 2010;Jud et al., 2011;Layman and Allgeier, 2012), indicating that they may compete with lionfish for food, although this has yet to be explored. ...
Species invasions are a widely-recognized threat to regional and global biodiversity. Lionfish (Pterois spp.), are an invasive marine fish that have been shown to reduce the recruitment and biomass of native reef fish throughout the Caribbean. Recently, it has become clear that lionfish are able to colonise a wide range of ecosystems (mesophotic reefs to brackish estuaries to mangroves) and tolerate a wider range of salinities than previously thought. Estuarine ecosystems often experience hyposaline conditions and act as critical foraging habitats for many ecologically and economically important species. Using a habitat competition experiment at two salinity treatments (10 practical salinity units (psu) and 37 psu control) we investigated the potential effects of lionfish on native Schoolmaster snapper (Lutjanus apodus; a tropical fish species found in high abundance in estuarine ecosystems). Schoolmaster snapper showed a 62 % and 47 % reduction in cover use when in the presence of lionfish in the 10 psu and 37 psu treatments, respectively. Further, five of the seven behaviours investigated during the interaction period, where both lionfish and snapper had access to the shelter, showed a significant reduction at low salinity, suggesting physiological or behavioural impairment of lionfish at low salinity. Because estuarine habitats are disproportionately important habitats for juvenile fishes, even physiologically or behaviourally compromised lionfish are likely to have some impact.
... These fishes allegedly exploited the mangrove area as feeding ground or nursery ground, as indicated by the fish catch, which ranged from juvenile to almost adult. Some studies suggest that mangroves are thought to provide more food for juvenile fish than other ecosystems, and there are about 70% -90% of juvenile-sized fish located within the mangroves (MacDonald et al. 2009;Mwandya et al. 2009). This hypothesis was reinforced by Nip and Wong (2010), showing that in the waters of the mangrove East of Hongkong half of the number of fish caught was still in juvenile size. ...
Lombok Island’s waters are the main gateway of the mass water flow from the Pacific and Indian Oceans. Therefore, it is suspected the fish species that inhabit them is very diverse. The aim of the research was to reveal the diversity of mangrove fish species, with a case study in West Lombok and Central Lombok. Fishes were caught using cast net with mesh sizes of 1.5 cm and 2.5 cm, gill net with mesh sizes of 3/4 inch, 1.5 inch and 2 inches. This research found 38 species belonging to 28 genera and 20 families. Oryzias javanicus and Periopthalmus argentilineatus were distributed at all research stations.Species diversity index (H) of fish was in the range of 2.618 to 3.072, evenness index (E) 0.803 to 0.950 and species richness index (d) from 4.328 to 6.206. Based on the similarity of fish species that exist in each station, the species of fish in station IV were different from those of other stations. © 2017, Society for Indonesian Biodiversity. All rights reserved.
... Checkered puffers, Sphoeroides testudineus (Linnaeus, 1758), are a common inhabitant of coastal habitats along the eastern United States and throughout the Caribbean (Pauly, 1991;MacDonald et al., 2009;Thiem et al., 2013). S. testudineus are common foragers within intertidal areas, often following rising tides to feed. ...
Sphoeroides testudineus (Linnaeus, 1758), is a common, widely distributed fish in coastal ecosystems. To better understand the trophic niche of S. testudineus, we collected individuals from tidal creeks on Abaco Island, The Bahamas, and employed stomach content and stable isotope analysis. Examination of stomach contents showed that mollusks, such as West Indian false cerith snails, cerith snails, and tellin clams, were the most common prey items. Diet data were consistent with stable isotopes data such that S. testudineus seem to feed at an intermediate trophic position in the food web. These preliminary data suggest that S. testudineus may be a critical intermediate link in these wetland food webs, serving as pathways through which energy is transferred from primary consumers to other predator species.
... Furthermore, seines are not deployable in many shallow water habitats obstructed by complex structures, i.e. reefs and harbors, though these areas have great ecological significance. For example, natural and man-made structures may offer refugia, e.g., mangrove prop roots (MacDonald et al., 2009), sea-grass beds (Sogard and Olla, 1993) and pile fields (Able et al., 1999), while other altered coastlines (harbors) may prove sub-optimal for fish (Able et al., 2013). Sonar cameras like the DIDSON and ARIS (Sound-Metrics Inc.) are valuable tools used to sample fish abundance non-destructively, size and behavior within hard-to-observe, structurally complex, turbid and dark environments. ...
Recent developments in sonar imaging provide an efficient way of obtaining near video quality of free-swimming fish in hard to reach areas, e.g., permanent structures like docks and piers, and hard to see environments, e.g., highly turbid waters. However, processing large volumes of data output by sonar imaging systems remains a major challenge. In the present study, we developed an automated image processing procedure to process footage recorded for 59 consecutive hours using an Adaptive Resolution Imaging Sonar, ARIS Explorer 3000 (Sound Metrics INC) deployed at a fixed location. Our approach successfully counted large free swimming fish at a precision rate >94% and estimated sample volume with manual and automatic calculations being highly correlated (r = 0.96). An auto-regressive time series model (of the sixth or higher order) with a zero-inflated Poisson distribution was used to estimate local abundance. Fish counts were low to zero during the first 31 h of sampling, and a major influx of fish occurred in the last 28 h. The observed pattern was co-incidental with local weather patterns: intermittent thunderstorms in the first 32 h and relatively calm weather in the last 24 h. Though thunderstorms limited our conclusions on fish-pier usage with tidal and diurnal cycles, it is apparent that weather conditions play a role in pier usage by large fish. Overall, the ARIS3000 deployment, automated data processing and statistical analyses used in this study proved successful in studying fish affiliations with piers in shallow habitats.
Keywords
Sonar imaging system; Fish abundance; Image analysis; Automated enumerating; Time series analysis
... The edge of both narrow and wider mangroves could provide equivalent hydrodynamic benefit to fish, because current flow decreases significantly within as little as 0.5 m from the edge of structured habitats, including mangroves and seagrass beds (Warry et al. 2009). Similarly, a small amount of structure along the edge may be all that is needed to provide sufficient refuge from predators for prey fish species, meaning that narrow mangroves may be sufficient to fulfil the needs of any fish that use mangrove structures for protection (MacDonald et al. 2009). In addition, although wider mangrove forests may provide a large area of potential habitat, oxygen levels deeper within the forest may rapidly become depleted because of bacterial breakdown of detrital material (Mazda et al. 1990;Wolanski et al. 1992). ...
The size and shape of a habitat patch can influence patterns of species utilisation. The present study examined how the width of fringing mangrove habitats affects the composition and use patterns of the fish assemblage using mangrove edge habitats on the flooding tide. Underwater cameras surveyed fish approaching mangrove habitats, ranging from a thin fringe 5m wide to forests over 75m wide, in a highly modified tropical estuary. The fish assemblage composition was similar across all mangrove widths, although the temporal patterns of use varied among mangrove widths for some species. The mean maximum number of individuals in the field of view was similar among mangrove widths, but fish were visible for a significantly greater proportion of time in videos from narrow (<20m) than wide (≥20m) mangrove stands (15v. 3% respectively). At least some fish were visible in the field of view in narrow mangrove fringes throughout the first hour of the flood tide, whereas in wide mangroves areas the presence of fish declined over time. The findings suggest that estuarine fish are using mangrove edge habitat regardless of width, making narrow mangroves viable habitats for estuarine fish.
... Tidal driven movements were logical for this N. brevirostris population, as are well documented for sharks inhabiting shallow primary and secondary nurseries in response to predation risk (Carlisle and Starr, 2009, Wetherbee et al., 2007, Ortega et al., 2009). It appears that areas of isolated shallow seagrass beds were favoured (Figure 94), probably the result of a combination of increased predator protection, from the shallow areas and slim channels running between them, and the potential increased prey availability provided by the seagrass beds (Valle and Bayle-Sempere, 2009, MacDonald et al., 2009, Kessel, 2004, Jennings et al., 2007 and marine life the structural relief attracts (Paramo et al., 2009, Vasquez-Yeomans et al., 2009, Nagelkerken and Faunce, 2008. This theory is supported as the greatest documented excursions away from the central area of the lagoon appeared to be orientated to the most easterly shallow seagrass bed and the direction of the subsequent depth contour in a WNW to ESE orientation. ...
Coastal shark populations have been subject to increasing anthropogenic pressure over the past two decades. This study focused on two lemon shark (Negaprion brevirostris) populations, the site-attached maturing sub-adults at the Island of Bimini, Bahamas, threatened by a large-scale resort development, and adults forming winter aggregations off the coast of Jupiter, Florida, subject to direct fishing pressure. For the sub-adult population, analysis was carried out on the long-term temporal patterns in abundance and population structure, relative to potential driving factors, and the influence of variables affecting longline catch-rates used as the basis for stock assessment. For the aggregating adult population, life-history aspects of population structure and distribution were investigated for relative implications on the species' vulnerability status. The following analysis and methodologies were utilised to investigate the two populations: longline catch records from 1982 – 2008; monitoring of variables potentially affecting longline catch-rates; documentation of shark behavioural interactions with longline equipment using underwater video surveillance; aerial surveying for abundance estimates; comparison of spatial utilisation patterns with longline catch locations; external tagging; the utilisation of archival satellite tags; passive tracking with Vemco acoustic monitoring system and research collaborations with other scientific groups utilising the same acoustic monitoring system. The key findings of this study were that in the northwest Atlantic, N. brevirostris populations are experiencing considerable anthropogenic pressure at all life-stages. In Bimini, the effects of a large-scale resort development have resulted in a significant decline in abundance, to a level (~52 individuals) well below the temporal average (~158). On the U.S. east coast, seasonal aggregating behaviour has further increased Steven Kessel Ph.D Thesis ii vulnerability through increased catchability, beyond the highly vulnerable status already attributed to this species, and targeted N. brevirostris fisheries appear to be currently operating at unsustainable levels. Shark longline catchability was noted to be significantly influenced by multiple shark presence, resulting in greater susceptibility for N. brevirostris (and other similar species) that naturally exhibit group behaviour. Incidental encounterability and predation risk significantly influenced longline catch-rates. Adult N. brevirostris exhibited large-scale seasonal migrations on the U.S. east coast, which, in addition to documented international transitions, supports existing evidence for genetic mixing across the distribution. Water temperature was found to be a significant driver of N. brevirostris behaviour at all life-stages, with an apparent adult temperature preference of ~24°C. This study represents the first long-term abundance assessment for sub-adult N. brevirostris, and the first in-depth study to focus on an adult N. brevirostris population. The results provide essential life-history information, revealing that at all life-stages N. brevirostris appear to be highly sensitive to anthropogenic activities, relative to other species, and therefore require enhanced management for species protection. It is therefore highly recommended that N. brevirostris be added to the U.S. prohibited species list.
... This article was interesting as it began to investigate particular features of the mangrove forest environment (vegetation density, hydrodynamics) that were important for sustaining large fish populations. These factors have been confirmed in contemporary mangrove-fisheries research as important in controlling fish population density and diversity at different life stages [32,33]. ...
Ecosystem services are now strongly applied to mangrove forests, though they are not a new way of viewing mangrove-people interactions; the benefits provided by such habitats, and the negative interactions (ecosystem disservices) between mangroves and people have guided perceptions of mangroves for centuries. This study quantified the ecosystem services and disservices of mangroves as written by colonial explorers from 1823-1883 through a literature survey of 96 expedition reports and studies. Ecosystem disservices were most commonly discussed (60%), with settlers considering mangroves as reservoirs of diseases such as malaria, with wide-ranging implications, such as the global drainage of wetlands in the 19th-20th centuries. Multiple ecosystem services were discussed, especially provisioning services for export, representing colonial views of new lands as ripe for economic use. Interestingly, regulating services of mangroves such as erosion control and sediment accretion that are a focus of much contemporary research were recognized as early as 1865. This study shows that the ecosystem service paradigm has a long history in mangroves. We should not underestimate mangrove ecosystem disservices, and how contemporary perceptions of mangroves may be influenced by such historical viewpoints; archival materials provide a rich resource to study human-environment interactions, and how they change through time.
... Three hypotheses have been postulated as to why mangrove 16 ecosystems are such effective nursery grounds for fish stocks: 17 (1) juveniles face less predation in the mangroves, (2) mangroves 18 provide more food for juvenile fish than other ecosystems and 19 (3) the structural heterogeneity of mangroves attracts juveniles 20 (Laegdsgaard and Johnson, 2001; MacDonald et al., 2009; Nanjo 21 et al., 2014). ...
... Where possible, disc width of animals was visually estimated, as habitat use in mangrove areas is known to vary with animal size (e.g. MacDonald et al. 2009). Rays were recorded as being present in one of the following four microhabitats: ...
Understanding the extent of movements and space use of animals is necessary to identify vital habitats and better conserve and manage vulnerable species. We used acoustic telemetry to examine movement patterns and habitat use of juvenile mangrove whiprays (Himantura granulata) in an intertidal bay at Orpheus Island, Australia. Thirteen juveniles were acoustically monitored between March and December 2012, and in July 2012, four active tracks were completed. The majority of the acoustically monitored rays remained within the intertidal bay for the entire monitoring period. Tidal changes caused rays to move from the inner-bay mangrove (high tide) habitat to coral reef in the outer bay (low tide). Actively tracked rays moved in a directed way during running tides, remaining in shallow water. During periods of high and low tide, when rays refuged in mangrove or reef habitats, movement was limited and sinuosity was high. In mangrove areas, rays were most commonly observed refuging under or close to mangrove roots, and rarely in open sand areas. Refuging behaviour in mangrove and reef habitats suggested that predation risk may be the predominant factor influencing the movement of small rays. The continuous use of intertidal habitats demonstrates their importance to Himantura granulata.
... These variations and the relatively higher diversity could probably be due to estuarine habitat characteristics such as geography, mangrove species, sampling procedure, human activities and sampling time (Dyer 1997; McLusky & Elliot 2004; Nabi et al. 2011). Mangrove forests dominated by Rhizophora apiculata such as the present study area are a favourable habitat for fishery resources, as most of the piscivorous predators are limited in their ability to attack their prey due to the complex systems of prop roots (Blaber 2000; Laegdsgaard & Johnson 2001; MacDonald et al. 2009; Nyanti et al. 2012). In addition, mangroves produce and supply enormous organic matter and nutrients to near-shore fishery resources (Ferdous & Muktadir 2009; Hasrizal et al. 2009). ...
This study was carried out to assess the fishery resources of the Sibuti River estuary, Sarawak, Malaysia. Data were collected from the study area for a period of one year in different seasons. The estuary is relatively species-rich and a total of 4675 individuals of 32 families from 60 species of fish (55), crab (four) and shrimp (one) were collected. Coilia dussumieri was the dominant species (22.63%) followed by Nemapteryx caelata (11.85%), Otolithes ruber (7.85%) and Ilisha elongata (5.80%). Marked seasonal variations were found among most of the hydrobiological factors; however, seasonal variations were not significant for the diversity indices such as Shannon–Wiener, Margalef and Evenness. The number of fish taxa caught in different mesh size gill nets was 1 inch (42 species) > 2 inch (36 species) > 4 inch (25 species), suggesting that smaller mesh nets are more suitable for assessing the diversity of fishery resources. SIMPER analysis showed that Coilia dussumieri was the most abundant species in the dry (10.3%) and intermediate (8.1%) seasons, whereas N. caelata was most abundant in the wet season (7.1%). Significant differences (ANOSIM and nMDS) were observed in the species community structure between dry–intermediate and dry–wet seasons; however, species compositions were not significantly different between intermediate and wet seasons. Canonical correspondence analysis (CCA) showed that most of the species assemblages were positively correlated with turbidity and chlorophyll a, followed by phosphate, nitrate and zooplankton density. The findings suggest that the Sibuti mangrove estuary is productive in terms of diversified fishery resources, which are influenced by the hydrobiological factors.
... These variations and the relatively higher diversity could probably be due to estuarine habitat characteristics such as geography, mangrove species, sampling procedure, human activities and sampling time (Dyer 1997;McLusky & Elliot 2004;Nabi et al. 2011). Mangrove forests dominated by Rhizophora apiculata such as the present study area are a favourable habitat for fishery resources, as most of the piscivorous predators are limited in their ability to attack their prey due to the complex systems of prop roots (Blaber 2000;Laegdsgaard & Johnson 2001;MacDonald et al. 2009;Nyanti et al. 2012). In addition, mangroves produce and supply enormous organic matter and nutrients to near-shore fishery resources (Ferdous & Muktadir 2009;Hasrizal et al. 2009). ...
The study was carried out to assess the fishery resources of the Sibuti river estuary, Sarawak, Malaysia. Data were collected from the study area for a period of one year in different seasons. The estuary is relatively species-rich and a total of 4675 individuals of 32 families from 60 species of fish (55), crab (four) and shrimp (one) were collected. Coilia dussumieri was the dominant species (22.63%) followed by Nemapteryx caelata (11.85%), Otolithes ruber (7.85%) and Ilisha elongata (5.80%). Marked seasonal variations were found among most of the hydro-biological factors; however, seasonal variations were not significant for the diversity indices such as Shannon–Wiener, Margalef and Evenness. The number of fish taxa caught in different mesh size gill nets was 1 inch (42 species) > 2 inch (36 species) > 4 inch (25 species), suggesting that smaller mesh nets are more suitable for assessing the diversity of fishery resources. SIMPER analysis showed that Coilia dussumieri was the most abundant species in the dry (10.3%) and intermediate (8.1%) seasons, whereas N. caelata was most abundant in the wet season (7.1%). Significant differences (ANOSIM and nMDS) were observed in the species community structure between dry–intermediate and dry–wet seasons; however, species compositions were not significantly different between intermediate and wet seasons. Canonical correspondence analysis (CCA) showed that most of the species assemblages were positively correlated with turbidity and chlorophyll a followed by phosphate, nitrate and zooplankton density. The findings suggest that the Sibuti mangrove estuary is productive in terms of diversified fishery resources, which are influenced by the hydro-biological factors.
... Mangrove forests provide a wide range of niches maintained by substrata such as mangrove roots, which maintain a high level of biodiversity (Gratwicke & Speight, 2005). The complexity of root structures provides cover and protection for small and juvenile fish communities (Ronnback et al., 1999; Correa & Uieda, 2008; Wang et al., 2009) that decrease their risk of becoming predated upon (Verweij et al., 2006; Tse, Nip & Wong, 2008; MacDonald, Shahrestani & Weis, 2009). The structural heterogeneity provided by the roots may either impede the movement of hunting predatory fish or the prey-fish are able to reduce their visibility by using the roots to hide behind (Laegdsgaard & Johnson, 2001; Kruitwagen et al., 2010)—therefore the diversity of animals and abundance of individuals are largely considered to be attributed to deterministic factors such as habitat complexity (Syms & Jones, 2000). ...
... Mangrove forests provide a wide range of niches maintained by substrata such as mangrove roots, which maintain a high level of biodiversity (Gratwicke & Speight, 2005). The complexity of root structures provides cover and protection for small and juvenile fish communities (Ronnback et al., 1999; Correa & Uieda, 2008; Wang et al., 2009) that decrease their risk of becoming predated upon (Verweij et al., 2006; Tse, Nip & Wong, 2008; MacDonald, Shahrestani & Weis, 2009). The structural heterogeneity provided by the roots may either impede the movement of hunting predatory fish or the prey-fish are able to reduce their visibility by using the roots to hide behind (Laegdsgaard & Johnson, 2001; Kruitwagen et al., 2010)—therefore the diversity of animals and abundance of individuals are largely considered to be attributed to deterministic factors such as habitat complexity (Syms & Jones, 2000). ...
Substantial amounts of dead wood in the intertidal zone of mature mangrove forests are tunnelled by teredinid bivalves. When the tunnels are exposed, animals are able to use tunnels as refuges. In this study, the effect of teredinid tunnelling upon mangrove forest faunal diversity was investigated. Mangrove forests exposed to long emersion times had fewer teredinid tunnels in wood and wood not containing teredinid tunnels had very few species and abundance of animals. However, with a greater cross-sectional percentage surface area of teredinid tunnels, the numbers of species and abundance of animals was significantly higher. Temperatures within teredinid-attacked wood were significantly cooler compared with air temperatures, and animal abundance was greater in wood with cooler temperatures. Animals inside the tunnels within the wood may avoid desiccation by escaping the higher temperatures. Animals co-existing in teredinid tunnelled wood ranged from animals found in terrestrial ecosystems including centipedes, crickets and spiders, and animals found in subtidal marine ecosystems such as fish, octopods and polychaetes. There was also evidence of breeding within teredinid-attacked wood, as many juvenile individuals were found, and they may also benefit from the cooler wood temperatures. Teredinid tunnelled wood is a key low-tide refuge for cryptic animals, which would otherwise be exposed to fishes and birds, and higher external temperatures. This study provides evidence that teredinids are ecosystem engineers and also provides an example of a mechanism whereby mangrove forests support intertidal biodiversity and nurseries through the wood-boring activity of teredinids.
... In recent years a number of experimental studies have contributed to a better understanding of the possible protective function of mangrove habitats for juvenile and small fishes in relation to predation risk. MacDonald et al. (2009) showed that in the Caribbean, time spent by juvenile Lutjanus apodus and Sphoeroides testudineus in mangrove prop root habitats was related to size e smaller individuals spend more time in the prop root areas. Working with tethered Lagodon rhomboides in Florida, Hammerschlag et al. (2010) showed that predation losses were highest near the edge of the mangroves. ...
Since 2002 there has been an increase in knowledge of many aspects of the biology and ecology of tropical estuarine fishes, as well as significant changes to many estuarine fisheries. Analyses of literature databases (2002–2012) show that: of the c. 600 relevant papers, 52% are primarily related to ecology, 11% to conservation, 11% to anthropogenic and pollution effects on fishes, 9% to fisheries, 7% to aquaculture, 4% to study techniques, and 1% each to fish larvae, effects of fishing, taxonomy, climate change, evolution and genetics. In terms of geographic spread 17% are from North America, 15% from south Asia, 14% from the Caribbean, 13% from Australasia, 12% from Africa and 9% each from South America and SE Asia. Research papers came from 50 countries of which the dominant were USA (15%), India (12%), Australia (11%) and Brazil (7%). Increasing numbers of studies in West Africa, SE and South Asia and South America have increased basic knowledge of the ecology of estuarine fish faunas. Increases in understanding relate to: roles of salinity, turbidity and habitat diversity; connectivity between habitats; water flow; ecological drivers of spatial variability; scale dependent variation; thermal tolerances; movement patterns; food webs; larval adaptations; and the viability of areas heavily impacted by human activities. New reviews both challenge and support different aspects of the estuarine dependence paradigm – still perhaps one of the main research issues – and the protective function of estuaries and mangroves for juvenile fishes has received attention in relation to e.g. predation risks and fisheries. There have also been significant advances in the use of guilds and biodiversity models. Fishing pressures have continued unabated in most tropical estuaries and are summarised and management issues discussed. Understanding of the relationships between fisheries production and mangroves has advanced and significant differences have emerged between Indo-West Pacific and Atlantic systems. The effects of fishing itself have also received attention and research is often related to conservation studies. The effects of anthropogenic activities are reviewed and important advances in mitigation are discussed. Restoration of estuarine habitats, such as mangroves, previously taking place mainly in countries such as Australia and USA, is now occurring in more countries. The design of reserves and the use of protected areas as management tools are gaining credence. Finally, the evidence for actual and potential effects of climate change is discussed.
... A lot of coralline algae was removed in these transects; its removal decreased some heterogeneity and a lot of hard substrate, but not of as many complicated structures where larger fish may hide. Smaller individuals of some species have been shown to make greater use of structure compared to larger individuals (MacDonald et al., 2009). The smallest fish are able to utilize a broader range of structure sizes as shelter, or feed more easily in the crevices of the coralline algae. ...
Using visual census, fish and sessile epifaunal communities were compared in Rhizophora mangle (red mangrove) prop roots in Bocas Del Toro, Panama, and Utila, Honduras. A separate field experiment where epibionts were removed was also conducted at the Panama site. The results revealed a significant positive correlation between epibiont diversity and fish species diversity as well as between epibiont abundance and fish biomass. The trend was consistent in both sites, although there were differences in the details at each location. Depth also weakly correlated with fish diversity in Panama, but not in Honduras. Results of field experiments also support a correlation between epibiont communities and fish habitat, although primarily for smaller individuals.
... Mangrove roots can be characterized on the basis of various structural properties, but by far the most study of mangrove's root structures were not enough to explore the characteristics of their root caps. Most of the study in mangrove's roots were focus on the architecture567, aerenchyma tissue8910, anatomy and morphology111213, gravitropism [6,14,15], the effect of root epibiont complexity [16], degree of shading [17,18], root density [17,19], and gas exchange20212223. The morphology of the root and root cap is determined primarily by the root apical meristem, because typically the radially symmetric meristem forms a cylindrical root. ...
The anatomy of the root caps in four root types of Avicennia marina were studied using conventional histological tech- niques by Ligth Microscopy (LM) in order to relate their development and structure of their function as environmental adaptation in mangrove’s root and to identify cellular polarities with respect to gravity. In columella cells, nuclei are located proximally. The result reveals that root caps consisted of two regions, i.e., central columella or statenchyma and peripheral regions. The columella cells (statocyte) are in the form of oval to rectangular. We also found that all root with marked gravitropism have statoliths that settle along different walls of that statocyte. Caps vary in form and size within root system of A. marina. The most striking feature of the root is the distinct and extensive root cap with quite long files of cells. From its shape, structure, and location, it seems clear that the root caps protects the cells under it from abrasion and assists the root in penetrating the soil.
... In addition to numerous reports of higher fish densities in mangrove than in non-mangrove soft-shore habitats (Thayer et al. 1987, Chong et al. 1990, Nagelkerken and van der Velde 2002), many studies noted the benefits provided to fish by mangroves. For example, structurally complex habitats created by the roots and branches of mangroves may provide refuge for juvenile fish (Thayer et al. 1987, Blaber 2000, MacDonald et al. 2009). Juveniles of some species of fish depend on mangroves as feeding grounds (Chong et al. 1990, Blaber 2000). ...
Conducted in subtropical coastal waters of eastern Hong Kong, this study provides information on species compositions of juvenile fish communities in several mangrove and non-mangrove habitats, and evaluated the influences of water temperature, salinity, turbidity, sediment organic matter (SOM), water depth, and sediment grain size on fish assemblages. In total, 85,427 fish belonging to 76 species from more than 29 families were collected. Fish densities were higher in mangrove mudflats than in non-mangrove habitats, but only a few of the dominant species were significantly more abundant in mangrove than in non-mangrove habitats. Fish assemblages in mangrove and non-mangrove mudflats were quite similar. Fish compositions were influenced by environmental factors including the SOM and water depth, but not by the presence of mangroves. The present study suggests that the nursery function of mangroves is both site- and species-specific. Compared to shallow mudflats with and without mangroves, deep-water sandy beaches may be less suitable for juvenile fish because of their low SOM content and high piscivorous fish abundances. More studies need to be conducted before definitive conclusions can be made on the nursery function of mangroves in Hong Kong and subtropical Asia.
Mangroves are considered as ecosystems that provide shelter, food and breeding grounds for many groups of inhabiting fauna. Much of the fauna present are organisms in different stages of their life cycle, mostly juveniles. The three-dimensional structure of the mangrove roots and the combination of the aquatic and terrestrial environments are factors that bring together a great diversity. Such diversity within mangrove sites includes aquatic and terrestrial vertebrates and invertebrates such as fish, amphibians, reptiles, mammals and birds. Present within the fauna are representatives of different trophic guilds that perform key functions in the ecosystem, such as pollination, seed dispersal and nutrient recirculation. The food produced by the ecosystem is based on the production of detritus caused by leaf litter and its decomposition, where transformation of energy and accumulation of biomass for higher trophic levels begins with the invertebrates. With regard to breeding activity, many fish families spawn in the mangrove roots (e.g. Fundulidae), or nest in the canopy (herons and cormorants) that provides protection against predators and food for juvenile organisms. Undoubtedly, mangroves function as feeding and breeding grounds that are essential in maintaining populations of marine organisms, especially fish. Many fish species that grow in the mangroves are important for fisheries. Unequivocally, maintaining these breeding sites for marine and terrestrial fauna is crucial to the general functioning of adjacent ecosystems.
Substantial amounts of dead wood in the intertidal zone of mature mangrove forests are tunnelled by teredinid bivalves. When the tunnels are exposed, animals are able to use tunnels as refuges. In this study, the effect of teredinid tunnelling upon mangrove forest faunal diversity was investigated. Mangrove wood not containing teredinid tunnels had very few species and abundance of animals. However, with a greater cross-sectional surface area of teredinid tunnels, the numbers of species and abundance of animals was significantly higher. Temperatures within teredinid-attacked wood were significantly cooler compared with air temperatures, and the animals in tunnels inside the wood may avoid desiccation by escaping the higher temperatures. Animals co-existing in teredinid tunnelled wood ranged from animals found in terrestrial ecosystems including centipedes, crickets and spiders, and animals found in subtidal marine ecosystems such as fish, octopods and polychaetes. There was also evidence of breeding within teredinid-attacked wood, as many juvenile individuals were found, and they may also benefit from the cooler wood temperatures. Teredinid tunnelled wood is a key low-tide refuge for cryptic animals, which would otherwise be exposed to piscivorous fishes and birds, and higher external temperatures. This study provides evidence that teredinids are ecosystem engineers and also provides an example of a mechanism whereby mangrove forests support intertidal biodiversity and nurseries through the wood-boring activity of teredinids.
Substantial amounts of dead wood in the intertidal zone of mature mangrove forests are tunnelled by teredinid bivalves. When the tunnels are exposed, animals are able to use tunnels as refuges. In this study, the effect of teredinid tunnelling upon mangrove forest faunal diversity was investigated. Mangrove wood not containing teredinid tunnels had very few species and abundance of animals. However, with a greater cross-sectional surface area of teredinid tunnels, the numbers of species and abundance of animals was significantly higher. Temperatures within teredinid-attacked wood were significantly cooler compared with air temperatures, and the animals in tunnels inside the wood may avoid desiccation by escaping the higher temperatures. Animals co-existing in teredinid tunnelled wood ranged from animals found in terrestrial ecosystems including centipedes, crickets and spiders, and animals found in subtidal marine ecosystems such as fish, octopods and polychaetes. There was also evidence of breeding within teredinid-attacked wood, as many juvenile individuals were found, and they may also benefit from the cooler wood temperatures. Teredinid tunnelled wood is a key low-tide refuge for cryptic animals, which would otherwise be exposed to piscivorous fishes and birds, and higher external temperatures. This study provides evidence that teredinids are ecosystem engineers and also provides an example of a mechanism whereby mangrove forests support intertidal biodiversity and nurseries through the wood-boring activity of teredinids.
DeYoe, H.; Lonard, R.I.; Judd, F.W.; Stalter, R., and Feller, I., 2020. Biological flora of the tropical and subtropical intertidal zone: Literature review for Rhizophora mangle L. Journal of Coastal Research, 36(4), 857–884. Coconut Creek (Florida), ISSN 0749-0208.
Rhizophora mangle L. is a tropical and subtropical mangrove species that occurs as a dominant tree species in the intertidal zone of low-energy shorelines. Rhizophora mangle plays an important role in coastal zones as habitat for a wide range of organisms of intertidal food webs, as a natural barrier to coastal erosion, and as carbon sequestration. A review of mangrove literature has been performed, but a review specifically on red mangroves has not. The approach was to cover a broad range of topics with a focus on topics that have seen significant work since the 1970s. This review includes a brief introduction to red mangroves and then focuses on the following topics: biogeography, habitats and zonation, geomorphological interactions, taxonomy, histology, anatomy, physiological ecology, productivity, biomass, litter, reproduction, population biology, plant communities, interactions with other species, impacts of storms, reforestation, remote sensing, modelling, and economic importance.
The stress axis in teleost fish attempts to maintain internal homeostasis in the face of allostatic loading. However, stress axis induction has been associated with a higher predation rate in fish. To date, the physiological and behavioural factors associated with this outcome are poorly understood. The purpose of the present study was to investigate the impact of experimental cortisol elevation on anti-predator behaviour and physiological responses to predator presence. We hypothesized that semi-chronic cortisol elevation would increase susceptibility to predation by increasing stress-induced risk taking behaviours. To test this hypothesis, schoolmaster snapper were given cocoa butter implants without cortisol (sham) or with cortisol (50 mg/kg body weight) and tethered to a set of cover. Fish were exposed to either a lemon shark or control conditions for 15 minutes. Space-use and activity were recorded throughout and fish were terminally sampled for blood. Cortisol implantation, relative to shams, resulted in higher blood glucose and plasma cortisol concentrations with a lower plasma lactate concentration. Shark exposure, relative to controls, elicited higher blood glucose and lactate concentrations but had no effect on plasma cortisol concentration. No interactions were detected between shark exposure and cortisol treatment for any physiological trait. Behavioural metrics, including shelter use and activity, were unaffected by either cortisol implantation or shark exposure. Physiological responses to cortisol implantation likely resulted from enhanced gluconeogenic activity whereas alterations under predator exposure may have been the product of catecholamine mobilization. Further work should address context-specific influences of stress in mediating behavioural responses to predation. This article is protected by copyright. All rights reserved
Os micronúcleos (MN) e as alterações morfológicas nucleares (AMN) em
eritrócitos são compostos por pequenos fragmentos de cromatina, como
resultado das quebras cromossômicas após ações genotóxicas, ou por
cromossomos inteiros que não migram durante a anáfase como resposta aos
contaminantes presentes no ambiente. O presente trabalho objetiva a
comparação da ocorrência dos micronúcleos e alterações morfológicas
nucleares entre as duas espécies de baiacus os Sphoeroides testudineus e
Sphoeroides greeleyi na Gamboa do Perequê. Os exemplares foram coletados
mensalmente na maré de quadratura, com uma rede Fyke, entre julho de 2009
e junho de 2010. As hemácias foram obtidas pela punção cardíaca, as lâminas
permaneceram secando por 24 horas. Posteriormente foram fixadas durante 20
minutos com metanol (100%), lavadas com água destilada e coradas com
Giemsa 5% por 40 minutos. Para cada lâmina, foram contadas 1000 células
com o auxílio do microscópio ótico no aumento de 100 vezes. S. testudineus
apresentou maior freqüência de MN no outono com valores médios de 0,04 ( n
= 21 ± 0,082)% e a menor no verão com valores médios de 0,01 ( n = 3 ±
0,02)% , e as AMN apresentaram maiores médias no outono 9,15 (n = 4089 ±
7,22)% e menores no verão com 3,84 ( n= 1239 ± 3,73)%. O S. greeleyi
apresentou as maiores médias de MN no inverno 0,04 (n= 5 ± 0,11)% não
ocorrendo na primavera, já as AMN tiveram maiores médias no outono 10,51 (n
= 1049 ± 6,04) %. Quando calculada a matriz da correlação de Pearson para o
S. testudineus foi identificada uma significância entre os MN e o comprimento
padrão, peso do corpo, ocorrendo também com a temperatura da água.
Entretanto para o S. greeleyi não ocorreu significância entre os MN e as
variáveis biométricas e os parâmetros ambientais. A partir do presente estudo
pode-se concluir que as espécies S. testudineus e S. greeleyi são bons
bioindicadores em ambientes estuarinos, desde que ambos sejam capturados
na mesma proporção para facilitar uma comparação entre as taxas de
freqüências de MN e AMN entre as espécies.
Utilization of fish as indicators of environmental quality in estuarine systems has received much recent attention, although some results have raised questions about using these taxa for such a role. We attempted to identify a fish response to a horticultural practice which removes portions of mangrove forest canopy to create unobstructed vistas. Fish were sampled monthly from six pairs of sites within the mangrove-forested intertidal zone of Rookery Bay, FL over two years. Following a first year of baseline sampling, the mangroves in one site from each pair of sites were pruned in accordance to Florida State law (Mangrove Trimming and Preservation Act of 1996), resulting in a mean 46% and 50% reduction in canopy coverage and litter fall, respectively. However neither the abundance nor species composition of fish in trimmed versus control plots were significantly different (Two-Way Repeated Measures ANOVA's for paired plot differences in fish density and biomass; nonmetric multidimensional scaling, and ANOSIM) suggesting that fish did not respond to mangrove canopy damage. Our results show that due to rather high spatial and temporal variability in fish abundance, it would be difficult to detect any but extreme changes of these taxa in the mangrove intertidal zone, and this may be a common feature of the fish communities of mangrove intertidal zones and other coastal systems. We suggest that improved use of fish as indicators of intertidal habitat quality would benefit from improved information on environmental factors which determine fish distribution and abundance in these areas. Moreover, since a majority of the fish in the intertidal zone is habitat generalists, we propose that individual-level measures of fish response to habitat quality may be more effective than fish abundance.
The considerable quantities of dead wood in the intertidal zone of mature mangrove forests are tunnelled by bivalves of the family Teredinidae. When the surface of heavily tunnelled wood is broken open, cryptofauna are able to use tunnels as refuges. In this study, the exploitation of this niche during low tide by the dartfish, Parioglossus interruptus was investigated. The majority of tunnels offer a close fit that fall within the range of typical dartfish diameters. The fish found within wood tended to be smaller than fish found swimming between mangrove roots at high tide. Dartfish were found in tunnelled wood even where it was emersed for over 11 hours per day, but favoured wood in the lower intertidal. Within the wood, daytime thermal maxima were reduced by 6.5°C compared with adjacent tidepools. Wind-tunnel observations indicated that this lowering could be due to evaporative cooling. However, dartfish were found to be notably tolerant of high temperatures, with a critical thermal maximum that exceeded temperatures reached in tunnelled wood and pools. Nonetheless, such tolerance may impose a metabolic cost that would be reduced by occupying tunnels. Teredinid tunnels are also likely to give dartfish protection from desiccation and predation. During high tide free-swimming dartfish were observed to favour areas of Rhizophora roots over open creeks. In aquaria, fish swam actively during the day, but took refuge in teredinid tunnels at night. Sampling of wood at low tide and direct observations at high tide indicate that a substantial proportion of the dartfish population takes refuge in wood during low tide. Thus, teredinid-tunnelled wood is a key low-tide refuge especially for younger fish, which would otherwise be exposed to predators. This study provides an example of a mechanism whereby mangrove forests support intertidal biodiversity.
Mangrove forests are one of the world's most threatened tropical ecosystems with global loss exceeding 35% (ref. 1). Juvenile coral reef fish often inhabit mangroves, but the importance of these nurseries to reef fish population dynamics has not been quantified. Indeed, mangroves might be expected to have negligible influence on reef fish communities: juvenile fish can inhabit alternative habitats and fish populations may be regulated by other limiting factors such as larval supply or fishing. Here we show that mangroves are unexpectedly important, serving as an intermediate nursery habitat that may increase the survivorship of young fish. Mangroves in the Caribbean strongly influence the community structure of fish on neighbouring coral reefs. In addition, the biomass of several commercially important species is more than doubled when adult habitat is connected to mangroves. The largest herbivorous fish in the Atlantic, Scarus guacamaia, has a functional dependency on mangroves and has suffered local extinction after mangrove removal. Current rates of mangrove deforestation are likely to have severe deleterious consequences for the ecosystem function, fisheries productivity and resilience of reefs. Conservation efforts should protect connected corridors of mangroves, seagrass beds and coral reefs.
Mangroves are often considered to be important nurseries for coral reef fishes, yet this assumption has rarely been tested. At Ishigaki Island, southern Japan, black-tail snapper Lutjanus fulvus juveniles often occur in mangroves, whereas subadults and adults are usually found on coral reefs, To test the hypothesis that L. fulvus uses mangroves as a nursery, we conducted stomach content and stable isotope analyses of L. fulvus collected from mangroves and an adjacent coral reef. Stomach content analysis showed that specimens from mangroves fed on mangrove-associated prey, whereas those from the coral reef took coral reef-associated prey, indicating that the species undergoes ontogenetic changes in resource use from the mangroves to the coral reef, i.e. coral reef individuals did not migrate to the mangroves to feed. Stable isotope analysis showed that potential prey and mangrove red snapper L. argentimaculatus (control fish for mangroves) collected from the mangroves had C-13-depleted values of -23 to -17 %., distinct from the -16 to -8%. values of potential prey and humpback red snapper L. gibbus (control fish for coral reef) collected from the coral reef. VC values of L. fulvus in the mangroves had a mangrove signature, whereas individuals on the coral reef gradually shifted from a mangrove signature to a coral reef signature with growth, indicating that small individuals on the coral reef were recent migrants from the mangroves. Based on the delta C-13 values of the subadult population of L fulvus on the coral reef, 36 of 41 individuals were estimated to have inhabited the mangroves during their juvenile stage, demonstrating that L. fulvus used the mangroves as a nursery.
It is often suggested that there are few piscivorous fishes in shallow estuarine habitats worldwide, and consequently that these habitats are valuable as nurseries for juvenile fishes because they provide refuge from predation. Information on the dietary habits of predatory fishes from tropical estuaries remains limited to broad summaries that lack quantitative detail on the fish components of the diet. Consequently, it remains unclear which predators in shallow tropical estuarine nurseries target new recruits. To define the assemblage of piscivorous fishes relevant to the functioning of shallow water nurseries, we examined the diets of predatory fishes from shallow (< 1.5 m) sandy habitats in the lower reaches of 17 tropical estuaries over 6 yr. In total, 51 taxa from 21 families fed on fish, and the piscivore assemblage included many taxa and size classes that have been previously overlooked. Piscivores ranged in size from 15 to 755 mm and the majority of taxa were piscivorous to some degree from sizes well below 100 mm. All of the smaller piscivores (< 100 mm) mainly preyed on small new recruits, while only some of the larger piscivores did so. The taxonomic and functional diversity in the piscivore assemblage, and the fish community as a whole, highlights the complexity of the role of predation in the functioning of shallow tropical estuarine nurseries. Despite this complexity, it is apparent that predation has the potential to be a major structuring force on shallow water tropical estuarine fish communities.
Little evidence is available on how juvenile fishes utilise seagrass beds and adjacent mangroves as feeding habitats. In this study we tested the degree to which Caribbean mangroves are utilised as feeding grounds by the fish community from adjacent seagrass beds. Stable carbon and nitrogen isotope analyses were performed on several potential food items from seagrass beds and adjacent mangroves, on muscle tissue of 23 fish species from seagrass beds on a Caribbean island (Curacao, Netherlands Antilles), and on juveniles of 2 common reef fish species, Haemulon flavolineatum and Ocyurus chrysurus, from seagrass beds in 7 bays on 5 Caribbean islands. Only the herbivore Acanthurus chirurgus and the carnivore Haemulon chrysargyreum appeared to feed predominantly in the mangrove habitat, whereas the carnivores Mulloidichthys martinicus and O. chrysurus (only on 2 islands) showed a stable carbon signature suggestive of food intake from the mangrove as well as the seagrass habitat. The piscivore Sphyraena barracuda foraged on fish schooling at the mangrove/seagrass interface. For the other 18 seagrass fish species, which contributed 86 % of the total seagrass fish density, the contribution of food sources from the mangroves was minor to negligible. The same was true for H, flavolineatum and 0, chrysurus on most of the other Caribbean islands. The results contrast with the situation in the Indo-Pacific, where intertidal mangroves serve as important feeding habitats for fishes from adjacent systems during high tide. This difference is most probably explained by both the absence of large tidal differences on Caribbean islands and the greater food abundance in seagrass beds than in mangroves.
Mangroves and seagrass beds are important daytime shelter habitats for juvenile Caribbean reef fish species, but little is known about their relative importance as feeding grounds. In the present study, we tested the degree to which these 2 habitats are used as a feeding ground for 4 nocturnally active fish species on Curacao, Netherlands Antilles. Stable isotope analysis was used as a technique to distinguish between feeding in mangroves and seagrass beds. Individuals of the 4 species which were sheltering during the daytime in permanently inundated fringing mangroves subject to low tidal exchange showed a stable carbon isotope signature indicative of a mixed diet composed of crustaceans from mangroves as well as seagrass beds, with the contribution from mangrove food items lying between 57 and 92%. However, individuals of the same species sheltering on adjacent (
Juveniles of a number of reef fish species develop in shallow-water 'nursery' habitats such as mangroves and seagrass beds, and then migrate to the coral reef. This implies that some reef fish species are distributed over the mangrove-seagrass-reef continuum in subpopulations with different size distributions that are spatially separated for considerable periods of time. To test this assumption, and to determine ontogenetic dietary changes (which may drive fish migrations from nursery habitats to the coral reef), we selected 9 herbivorous and carnivorous reef fish species whose juveniles are highly abundant in nearby nursery habitats. 13C:12C and 15N:14N ratios were measured in fish muscle tissues and in potential food items collected from each of the 3 habitats, and fish gut contents were identified. All d13C signatures of fishes sampled from the coral reef were close to the carbon isotope signatures of food items on the reef, and were significantly depleted compared to those of fishes from the nursery habitats (with the exception of Scarus iserti). Gut-content analysis of herbivorous fishes entailed problems with identification of the ingested food items, but there was no change in the d13C or d15N signatures of the muscle tissue as a function of fish size. Regression analysis showed significant positive relationships between d15N content and fish size in all carnivorous fish species; this was correlated to the decreasing dietary importance of small crustaceans and the increasing consumption of decapod crabs or prey fishes with increasing size. The combined study of stomach contents and stable isotopes showed that the juveniles and adults of these reef fish species are separated ecologically and spatially for a considerable period of time, and that herbivorous fishes do not change their trophic status with increasing size, whereas carnivorous fishes feed on increasingly larger prey at increasingly higher trophic levels prior to their migration from the nursery habitat to the coral reef. [KEYWORDS: Reef fishes; Seagrass beds; Mangroves; Coral reef; Nursery habitats; Diet shift; Fish size; Stable isotopes; Life cycle migrations]
We examined whether the abundance and diversity of recently settled fish associated with artificial habitats varied with the position of the habitat in the water column (surface versus seafloor), its vertical movement (moving vertically with the tide versus stationary), and whether it was shaded. The total abundance of recently settled fish did not vary due to position or movement in an experiment designed to test for the effects of these two factors. However, in a second experiment that tested for both shading and movement, significantly greater numbers of fish settled to shaded habitats that were stationary. The number of species of settlers did not vary significantly due to position. movement or shade in either experiment. However, the abundance of several species varied significantly with at least one of these factors, suggesting that habitat may be provided for a greater number of species if artificial structures are installed under a wide range of conditions. Extra habitat will be of most benefit where there is a good supply of competent larvae and where habitat is limited.
Fringing mangrove forests and seagrass beds harbor high densities of juvenile snappers and grunts compared to bare substrates, but their occupancy of these habitats is not homogeneous at ecologically meaningful scales, thus limiting our ability to compare habitat value. Here, density and size information were used to determine how gray snapper, Lutjanus griseus (Linnaeus, 1758) and bluestriped grunt, Haemulon sciurus (Shaw, 1803), use vegetated habitats during their ontogeny, and how their use of mangrove forests varied with season across broad spatial scales and physicochemical conditions. Both species exhibited a three-stage ontogenetic strategy: (1) settlement and grow-out (8-10 mo) within seagrass beds, (2) expansion to mangrove habitats at 10-12 cm total length, and (3) increasing utilization of inland mangroves during the dry season and with increasing body size. For fishes inhabiting mangroves, multivariate tests revealed that the factors distance from oceanic inlet and water depth were stronger predictors of reef fish utilization than the factors latitude, temperature, or habitat width. These findings highlight that the nursery function of mangrove shorelines is likely limited to the area of immediately accessible habitat, and that more expansive forests may contain a substantial number of larger adult individuals.
The importance of mangroves as feeding grounds for fish and other macrozoob-enthos in the Indian Ocean and elsewhere has been a subject of debate. This could partly be due to the fact that studies describing this role have been conducted in mangrove systems that differed in their settings. By using stable isotope analysis of carbon and nitrogen, we investigated two different settings of mangroves along the Tanzanian coast, to establish if mangrove setting influences the extent to which this habitat is utilized as a potential feeding ground by fish. The two mangrove settings were: mangrove-lined creeks which retain water during low tides and fringing mangroves that drain completely during low tides. The δ13C signatures of most fishes from the mangrove-lined creeks were similar to those of food items from the mangrove habitat, which suggests that these fishes feed from the mangrove habitats. In contrast, the overlap in δ13C of some food items from the fringing mangroves with those from adjacent habitats, and the more enriched δ13C signatures of fishes from the fringing mangroves with respect to most typical food items from the mangrove habitat could be an indication that these fishes feed from both habitats but to a lower extent from the fringing mangroves. The results suggest that fishes feed more from the mangrove-lined creeks as compared to fringing mangroves which is probably related to differences in the degree of mangrove inundation. The more or less continuous access provided more time for fishes to stay and feed in the mangrove-lined creeks compared to fishes from the fringing mangroves, which have access to these mangroves only during high tide and have to migrate to adjacent habitats with the ebbing tide.
Biscayne Bay is a shallow subtropical lagoon on Florida's southeastern coast that is bordered to the west by the mainland and to the east by barrier islands and keys. Fish assemblages inhabiting two types of mangrove-lined shoreline that encompass the Bay were examined using a visual 'belt-transect' census method over four consecutive seasons. Several significant differences were evident between shoreline habitats in terms of fish species composition, taxonomic richness and taxon-specific densities; seasonal changes and fish size-structure differences were few. The mangrove shorelines along the mainland (ML) consistently harbored less fish taxa than those on the leeward side of the islands and keys (LK), but harbored higher densities of several euryhaline forms (i.e., killifishes and livebearers). Densities of fishes that are typically associated with coral reef habitats (i.e., snappers and grunts) tended to be higher within LK vs ML mangrove shorelines, but there were exceptions (e.g., great barracuda, Sphyraena barracuda). For five fish species, length-frequency distributions were compared between the Bay's mangrove shorelines and nearby coral reef habitats. These data comparisons lent partial support to an ontogenetic 'mangrove-to-reef' migration model for only two of the five species examined. Results suggest that these shoreline habitats play varying ontogenetic and trophic roles, depending on location, season and fish species. Biscayne Bay's mangrove shoreline fish assemblages appear to reflect: (1) proximity of the mangroves that they occupy to offshore reef habitats; (2) salinity regime along the shoreline; and (3) water depths within the mangrove forest interior. The fish assemblage information collected here may serve as a 'baseline' in future assessments of fishing impacts or the effects of other anthropogenic changes to Biscayne Bay and its watershed.
Michael W. Beck, Kenneth L. Heck, Jr., Kenneth W. Able, Daniel L. Childers, David B. Eggleston, Bronwyn M. Gillanders, Benjamin Halpern, Cynthia G. Hays, Kaho Hoshino, Thomas J. Minello, Robert J. Orth, Peter F. Sheridan and Michael P. Weinstein
Mangroves and seagrass beds have received considerable attention as nurseries for reef fish, but comparisons have often been made with different methodologies. Thus, relative importance of different habitats to specific size-classes of reef fish species remains unclear. In this study, 35 transects in 11 sites of mangroves, seagrass beds and coral reef were surveyed daily, in and in front of a marine bay on the island of Curaçao (Netherlands Antilles). The density and size-frequency of nine reef fish species (including herbivores, zoobenthivores and piscivores) was determined during a five-month period using a single methodology, viz. underwater visual census. All species were ‘ nursery species ’ in terms of their high densities of juveniles in mangroves or seagrass beds. Relative density distribution of the size-classes of the selected species over mangroves and seagrass beds suggested high levels of preference for either mangroves or seagrass beds of some species, while other species used both habitats as a nursery. Spatial size distribution of the nine species suggested three possible models for Post-settlement Life Cycle Migrations (PLCM). Haemulon sciurus, Lutjanus griseus, L. apodus, and Acanthurus chirurgus appear to settle and grow up in bay habitats such as mangroves and seagrass beds, and in a later stage migrate to the coral reef (Long Distance PLCM). Juveniles of Acanthurus bahianus and Scarus taeniopterus were found only in bay habitats at close proximity to the coral reef or on the reef itself, and their migration pattern concerns a limited spatial scale (Short Distance PLCM). Some congeneric species carry out either Long Distance PLCM or Short Distance PLCM, thereby temporarily alleviating competition in reef habitats. Haemulon flavolineatum, Ocyurus chrysurus and Scarus iserti displayed a Stepwise PLCM pattern in which smallest juveniles dwell in the mouth of the bay, larger individuals then move to habitats deeper into the bay, where they grow up to a (sub-) adult size at which they migrate to nearby coral reef habitats. This type of stepwise migration in opposite directions, combined with different preference for either mangroves or seagrass beds among (size-classes of) species, shows that reef fish using in-bay habitats during post-settlement life stages may do so by choice and not merely because of stochastic dispersal of their larvae, and underline the necessity of these habitats to Caribbean coral reef systems.
Movement by the larger more mobile species of coral reef fish plays a significant role in determining patterns in abundance
and population structure. Fish movement is also relevant to the use and effectiveness of marine reserves in managing fish
populations. Coral trout are large piscivorous serranids supporting major fisheries on the Great Barrier Reef (GBR). This
study reports on the within-reef movement of the common coral trout, Plectropomus leopardus, at Heron Reef, southern GBR, over a twelve month period, investigated by tagging and underwater tracking. Tracking of coral
trout revealed no apparent relationship between the area moved and stage of tide or time of day. However, movement areas were
affected by the size of fish: in spring a linear relationship between fish size and area of movement was measured, but in
summer the largest (male) fish moved over significantly smaller areas than medium-sized fish. Movement of males may be related
to cleaning behaviour and spawning. Fifty nine percent (n=101) of the tagged fish were resighted over periods of 4–5 months, in “home sites” measuring ∼2000 m2. Coral trout were not restricted to home sites, but moved on average 2 km along the reef slope; maximum distances of 7–7.5 km
were measured. Coral trout appear to range as mobile, opportunistic predators, but also maintain home sites for access to
shelter and cleaning stations.
The nursery function of various biotopes for coral reef fishes was investigated on Bonaire, Netherlands Antilles. Length and abundance of 16 commercially important reef fish species were determined by means of visual censuses during the day in six different biotopes: mangrove prop-roots (Rhizophora mangle) and seagrass beds (Thalassia testudinum) in Lac Bay, and four depth zones on the coral reef (0 to 3 m, 3 to 5 m, 10 to 15 m and 15 to 20 m). The mangroves, seagrass beds and shallow coral reef (0 to 3 m) appeared to be the main nursery biotopes for the juveniles of the selected species. Mutual comparison between biotopes showed that the seagrass beds were the most important nursery biotope for juvenile Haemulon flavolineatum, H. sciurus, Ocyurus chrysurus, Acanthurus chirurgus and Sparisoma viride, the mangroves for juvenile Lutjanus apodus, L. griseus,Sphyraena barracuda and Chaetodon capistratus, and the shallow coral reef for juvenile H. chrysargyreum,L. mahogoni , A. bahianus and Abudefduf saxatilis. Juvenile Acanthurus coeruleus utilized all six biotopes, while juvenile H. carbonarium and Anisotremus surinamensis were not observed in any of the six biotopes. Although fishes showed a clear preference for a specific nursery biotope, most fish species utilized multiple nursery biotopes simultaneously. The almost complete absence of juveniles on the deeper reef zones indicates the high dependence of juveniles on the shallow water biotopes as a nursery. For most fish species an (partial) ontogenetic shift was observed at a particular life stage from their (shallow) nursery biotopes to the (deeper) coral reef. Cluster analyses showed that closely related species within the families Haemulidae, Lutjanidae and Acanthuridae, and the different size classes within species in most cases had a spatial separation in biotope utilization.
There is a long-standing debate whether mangrove and seagrass habitats in the Indo-Pacific region function as nurseries for coral reef fishes. We studied the use of all major shallow-water habitat types by juvenile coral reef fish using visual census surveys at 4 islands along the Tanzanian coast (East Africa) and at the island of Grande Comoros (Comoros archipelago). We investigated the value of mangroves, seagrass beds, coral reefs, macroalgae and intertidal flats as a juvenile habitat for fish by studying density distribution patterns of juveniles and adults of 76 reef fish species in these habitats. We assessed (1) which part of the reef fish-community used mangrove-seagrass habitats as juvenile or adult habitats, (2) whether adult fish densities and diversity on adjacent reefs were related to the presence of these shallow habitats, and (3) whether adults of species that use these habitats when juvenile were less abundant on coral reefs situated far away from these juvenile habitats. Sea-grass beds and coral reefs were the most important juvenile fish habitats. Ontogenetic migrations between seagrass beds and reef habitats possibly occur, since several species showed their highest juvenile densities on seagrass beds, whereas adults showed their highest densities on reefs adjacent to these seagrass beds. The presence of areas with seagrass beds positively influenced adult densities of many reef fish species on adjacent coral reefs. Of the 36 fish species whose juveniles were observed in seagrass beds along the Tanzanian coast, 32 species were absent from or showed low densities on coral reefs of the island of Grande Comoros (lacking seagrass beds or mangroves). On reefs far from seagrass beds and mangroves along the Tanzanian coast, 25 of these 36 species were absent or showed low densities in comparison with reefs adjacent to these habitats.
Mangroves and seagrass beds have long been considered important nursery grounds for various species of juvenile reef fishes due to their higher abundances in these habitats compared to coral reefs. It is assumed that these putative nurseries provide juveniles with more shelter, higher
food availability and higher growth and survival rates than on the reef. However, this nursery function is still ambiguous, and few experimental field studies have tested this hypothesis in these tropical habitats. In the present study, the growth rate of juvenile Haemulon flavolineatum and the availability
of its preferred food were determined in seagrass, mangrove and coral reef habitats. It was hypothesized that somatic growth rates as well as the amount of preferred food are higher within these putative nurseries than on the reef (according to the nursery hypothesis). The growth of small
juveniles (3.5 to 4.2 cm total length, TL) was studied at 2 Caribbean islands using in situ experimental growth cages. Gut content analysis of the caged fishes showed that Copepoda were by far the most consumed food items by juveniles in all 3 habitats. Copepoda in the plankton samples were
more abundant on the reef than in the mangrove/seagrass habitats. Growth rates of fishes showed the same pattern: higher growth rates in length and weight (significant for Aruba, a trend for Curaçao), and a higher weight–length ratio on the reef compared to the mangrove/seagrass habitats. Based on these observations it appears that the coral reef would be a more suitable habitat for small juveniles, when not taking other factors such as predation risk into account. Nevertheless, the highest juvenile fish abundances are found in mangrove/seagrass nurseries where predation risk, but also growth rate, is lower. Therefore, it appears that a tradeoff exists between food abundance/growth rate and predation pressure/mortality risk, where fish select habitats that minimise the ratio of mortality risk to growth rate.
Mangroves and seagrass beds are considered nurseries for juvenile fish, but little experimental evidence exists to elucidate which factors make them attractive habitats. A multifactorial field experiment on the use of these habitats by juvenile reef fish and their behaviour was performed during daytime with experimental units (EUs: 1 × 1 × 0.8 m), each representing a unique combination of the factors structure, shade, and food, using artificial seagrass leaves (AS) and artificial mangrove roots (AM). Diurnally active herbivores were most abundant in EUs containing food, and grazed on algae growing on the structures, but were not attracted to structures in the absence of food. The most abundant diurnally active zoobenthivores (Eucinostomus spp.) were present in highest numbers in any EU with food, where they fed on zoobenthos or rested on the bottom. The nocturnally active zoobenthivore/zooplanktivore Ocyurus chrysurus and the diurnally active piscivore Sphyraena barracuda were primarily attracted to structure, in which they rested and were not observed to feed. Haemulon flavolineatum was mainly attracted to AS, Lutjanus mahogoni was attracted to AS or shade, whereas L. apodus, O. chrysurus and S. barracuda were found in AM as well as in AS. The data suggest that during daytime, herbivores and diurnally active zoobenthivores are probably attracted to mangroves and seagrass beds primarily by food, and nocturnally active zoobenthivores by structure (in interaction with shade) that offers shelter from predation. S. barracuda is also attracted primarily to structure, but the larger individuals probably use this for ambush predation rather than for protection. In conclusion, our experiment clarifies that presence of structure, food and shade significantly contribute to the attractiveness of mangroves and seagrass beds to juvenile reef fish
Mangrove forests are one of the world's most threatened tropical ecosystems with global loss exceeding 35% (ref. 1). Juvenile coral reef fish often inhabit mangroves, but the importance of these nurseries to reef fish population dynamics has not been quantified. Indeed, mangroves might be expected to have negligible influence on reef fish communities: juvenile fish can inhabit alternative habitats and fish populations may be regulated by other limiting factors such as larval supply or fishing. Here we show that mangroves are unexpectedly important, serving as an intermediate nursery habitat that may increase the survivorship of young fish. Mangroves in the Caribbean strongly influence the community structure of fish on neighbouring coral reefs. In addition, the biomass of several commercially important species is more than doubled when adult habitat is connected to mangroves. The largest herbivorous fish in the Atlantic, Scarus guacamaia, has a functional dependency on mangroves and has suffered local extinction after mangrove removal. Current rates of mangrove deforestation are likely to have severe deleterious consequences for the ecosystem function, fisheries productivity and resilience of reefs. Conservation efforts should protect connected corridors of mangroves, seagrass beds and coral reefs.
J. lngles and D. PauJypresented at the Fourth lntl'mational Coral ReefSymposium a seasonally oscillating growth curve for the puffer Sphoaoides ttstudineus (retraodontidae). based on length-frequency data collected in 1974 in Aorida by T.E. Targett. but forgot to include the corresponding growth parameters In the ensuing publication. These are given here
Both cover and light intensity are important factors in microhabitat selection of fishes, suggesting a possible hierarchical relationship. Many centrarchids have been shown to prefer low light intensities and heavy submerged cover, but adult nonbreeding longear sunfish are reported to occupy sparsely vegetated, clear, shallow water during the brightest part of the day, probably for foraging. To determine the relative importance of cover and light intensity to longear sunfish, we presented nonbreeding adults with choices between these two conditions in a series of three laboratory experiments. Longear sunfish preferred low light to high light intensity and preferred submerged cover to no cover. However, when given a choice, they preferred to occupy low light intensity conditions without cover rather than submerged cover under higher light intensity conditions. Thus, low light intensity, such as is found in greater pool depths, may be the preferred refuge from predation for longear sunfish.
The spatial size distribution of grunts and snappers have previously indicated the separation of juveniles in nursery habitats from the adults on the coral reef. This implies life cycle migrations from nursery habitats (such as seagrass beds and mangroves) to the coral reef. If diet shifts are related to such migrations, then the diets of these fish must change before or around the fish size at which such migrations take place. A wide size range of juveniles of two grunt species (Haemulon sciurus and Haemulon flavolineatum) and of two snapper species (Lutjanus apodus and Ocyurus chrysurus) were caught in seagrass beds and mangroves, and their gut contents identified and quantified. Regression analysis between fish size and dietary importance of small crustaceans showed a negative relationship in all four species. Positive relations were found for H. sciurus, L. apodus and O. chrysurus between fish length and the dietary importance of decapods, and for L. apodusand O. chrysurus between fish length and prey fish importance. Critical changes in the fish diets with fish size were examined by application of a Canonical Correspondence Analysis (CCA). The CCA yielded three clusters of size-classes of fishes with similar diets, and application of a Mantel test showed that each of these clusters had significantly different diets, and that each cluster diet was significantly specialised. The size at which a fish species ‘switched’ from one cluster to another was compared with size-at-maturity data and with the typical size at which these species migrate from the nursery habitats to the coral reef. H. sciurus and H. flavolineatum may be prompted to migrate from the nursery habitats to coral reef habitats because of dietary changes, or because of the development of the gonads. For L. apodus and O. chrysurus, a dietary changeover forms a more likely explanation for nursery-to-reef migrations than does sexual maturation because these species reach maturity at sizes much larger than the maximum size of individuals found in nursery habitats. Although other factors may theoretically initiate or promote the migration patterns, the results of this study indicate that ontogenetic dietary changes may crucially influence the nursery-to-coral reef migrations of these reef fish species.
Partitioning of the food resources by two coexisting pufferfishes (Sphoeroides spengleri and S. testudineus) from Biscayne Bay, Florida, USA, was investigated. Gut contents from 453 bandtail and 339 checkered puffers were analyzed. The diets of both species consisted of a variety of benthic prey, but only crustaceans and molluscs were important prey groups. While differences were found in the proportions of general prey categories eaten by these fishes, both species consumed substantial quantities of brachyuran crabs, bivalves, and gastropods. Specific identification of the prey items within these three food categories revealed additional differences in prey between the two puffer species. This partitioning of the food resources by bandtail and checkered puffers was found between both species overall, between overlapping size ranges, and between both species' most abundant size group. Differences in food habits between these two fishes illustrate that congeners with virtually identical mouth structure and complete spatial overlap can significantly partition the food resources.
Field observations quantified the effects of fish size and time of day on activity patterns, intraspecific encounters, and foraging styles in mutton snapper,Lutjanus analis, during the spring and winter of 1991. Fish ranged in size from 15 to 65 cm fork length (FL), and were associated with an artificial patch reef system located on a shallow seagrass meadow in the Exuma Cays, Bahamas. The most common, non-resting diurnal activities were intraspecific chasing and displacing, and feeding. Intraspecific displacing was significantly higher during midday compared to morning or evening. The highest proportion of intraspecific encounters (combined chasing and displacing events) occurred among medium (25–35 cm FL) and large (> 35 cm FL) fish. The few large fish observed (13% of population) initiated the same proportion of encounters as the predominant (50%) medium fish. The remaining (37%) small fish (> 25 cm FL) were the least aggressive. Dark barred and dark nape color patterns were associated with displacing and chasing, respectively. Fish exhibited considerable variability in feeding behavior, Proportionally fewer fish fed during midday compared to morning or evening, although small fish fed proportionally more often than medium or large fish despite time of day. Picking was the primary feeding mode and was observed during all times of day. Winnowing was observed during midday and evening, whereas midwater strikes were confined to morning and evening. Small fish displayed proportionally higher picking and midwater strikes during morning and evening, respectively, compared to medium or large fish. However, large fish winnowed proportionally more often than small or medium fish during evening. Dark barred color patterns were associated with feeding on the substrate, whereas no color changes occurred during midwater strikes. Our results indicate thatL. analis forms dominance hierarchies and that high variability in foraging styles, according to fish size and time of day, may be a means to reduce intraspecific competition.
The value of mangroves for fish species is usually explained in terms of high food abundance or shelter against predators as a result of high turbidity and structural complexity. In a field experiment, artificial mangrove units (AMUs) were designed as open cages, each of which was provided with a different degree of structural complexity and shade. Fish species that were attracted to the AMUs were identified and counted and the effects of shade and structural complexity, as well as the interaction between the two factors, were tested. Diurnal fish showed a preference for the greatest structured complexity and for a moderate increase in shade. Two nocturnal species common in local mangroves as well as seagrass beds showed statistically significant effects: densities of Haemulon sciurus were positively related to both shade and structural complexity, whereas only shade had a significant positive effect on densities of Ocyurus chrysurus. The experiment indicated that the attractiveness of mangrove vegetation for H. sciurus may be influenced by the structural complexity of the habitat as well as by the degree of shade, and that both factors are equally and separately important. Individuals of O. chrysurus that are attracted to mangroves are more likely to be influenced by the presence of shade than by the degree of structural complexity. The data thus indicated that the positive relationship between fish densities in mangrove habitats and the degree of shade and structural complexity, or both, is species-specific.
The flooded intertidal zone in coastal estuarine systems (e.g., mangroves and salt marshes) is thought to provide nekton with
both food and refuge from predators. The primary aim of this study was to identify the relative contribution of root structure,
shading, and leaf litter, all characteristic features of mangrove forests, in shaping the intertidal distribution of tidally
migrating fishes. We manipulated the structure and shade in 9-m2 sample plots in a shallow, mangrove-fringed, intertidal embayment in Tampa Bay, Florida. In a separate field experiment,
we compared fish association with standing mangrove leaf litter and bare sand substrate. Shade and leaf litter had a water
depthdependent effect on the distribution of the fish; no effect was associated with the presence of mangrove roots. In shallow
water (<45 cm), fish were captured primarily in plots without shade, but this distribution shifted progressively with increasing
water depth, so that when water was greater than 55 cm most fish were captured in shaded plots. Fish were more frequently
associated with, and feeding in, plots covered in leaf litter than bare sand plots. This relationship did not persist at depths
greater than 15 cm because fish abundance declined gratly. Tethering experiments usingCyprinodon variegatus demonstrated that predation pressure was quadratically correlated with water depth (inflexion point approximately 60 cm).
Our results suggest that small fishes will abandon well-lighted foraging grounds in favor of the potential refuge of shaded
waters as water depth increases. We suggest that studies of intertidal nekton should be carefully interpreted in the context
of water depth.
Caribbean seagrass beds are important feeding habitats for so-called nocturnally active zoobenthivorous fish, but the extent to which these fishes use mangroves and seagrass beds as feeding habitats during daytime remains unclear. We hypothesised three feeding strategies: (1) fishes feed opportunistically in mangroves or seagrass beds throughout the day and feed predominantly in seagrass beds during night-time; (2) fishes start feeding in mangroves or seagrass beds during daytime just prior to nocturnal feeding in seagrass beds; (3) after nocturnal feeding in seagrass beds, fishes complete feeding in mangroves or seagrass beds during the morning. We studied the effect of habitat type, fish size, social mode and time of day on resting and feeding behaviour of large juvenile (5–10cm) and sub-adult (10–15cm) Haemulon flavolineatum in mangroves and seagrass beds during daytime. Sub-adults occurred in mangroves only, spent most time on resting, and showed rare opportunistic feeding events (concordant with strategy 1), regardless of their social mode (solitary or schooling). In contrast, large juveniles were present in both habitat types and solitary fishes mainly foraged, while schooling fishes mainly rested. Exceptions were small juveniles (±5cm) in seagrass beds which foraged intensively while schooling. Large juveniles showed more feeding activity in seagrass beds than in mangroves. In both habitat types, they showed benthic feeding, whereas pelagic feeding was observed almost exclusively in the seagrass beds. In both habitat types, their feeding activity was highest during 8:00–10:30hours (concordant with strategy 3), and for seagrass fishes, it was also high during 17:30–18:30hours (concordant with strategy 2). The study shows that both mangroves and seagrass beds provide daytime feeding habitats for some life-stages of H. flavolineatum, which is generally considered a nocturnal feeder.
Stomach contents from 449 schoolmaster snapper, Lutjanus apodus, from southwestern Puerto Rico were examined. Hierarchical cluster analysis identified two primary trophic groups: less than or equal to 70 mm FL and >70 mm FL. Small L. apodus (less than or equal to 70 mm) fed almost exclusively on crustaceans (89% by weight; 95% by number; 98% frequency of occurrence), particularly amphipods and crabs. By contrast, L. apodus greater than 70 mm preferred piscine prey (57% by weight; 37% by number; 63% frequency of occurrence) and supplemented their diets with crabs, shrimp, and stomatopods. Ontogenetic patterns in diet were related to changes in jaw morphology (i.e., gape dimensions). Moreover, spatial and temporal variations were size-related and appeared to play some role in structuring the diet of L. apodus. Small L. apodus (less than or equal to 70 mm) were found only in mangrove prop- root habitats and showed peak feeding at midday. Larger L. apodus (>70 mm) were present in both mangrove and coral reef habitats and showed little variation in diurnal feeding periodicity. Prey selection patterns of L. apodus were influenced by habitat and season.
Job number added acc. to DOCREP assignment illus.
Three hypotheses to discern the strong positive association between juvenile fish and mangrove habitat were tested with field and laboratory experiments. Artificial mangrove structure in the field attracted slightly more juvenile fish than areas without structure. Artificial structure left to accumulate fouling algae attracted four-times the total number of juvenile fish than areas without structure or areas with clean structure. Community composition of fish attracted to structure with fouling algae was different when compared with areas with no structure or clean structure; five species were attracted by structure with fouling algae whilst two species were associated with structure regardless of fouling algae. Algae were linked to increased food availability and it is suggested that this is an important selection criteria for some species. Other species were apparently attracted to structure for different reasons, and provision of shelter appears to be important. Predation pressure influenced habitat choice in small juvenile fish in laboratory experiments. In the absence of predators, small juveniles of four out of five species avoided shelter but when predators were introduced all species actively sought shelter. Large fish were apparently less vulnerable to predators and did not seek shelter when predators were added to their tank. Feeding rate was increased in the mangrove habitat for small and medium-sized fish compared with seagrass beds and mudflats indicating increased food availability or foraging efficiency within this habitat. Larger fish fed more effectively on the mudflats with an increased feeding rate in this habitat compared with adjacent habitats. The most important aspect of the mangrove habitat for small juvenile fish is the complex structure that provides maximum food availability and minimises the incidence of predation. As fish grow a shift in habitat from mangroves to mudflat is a response to changes in diet, foraging efficiency and vulnerability to predators.
Fishbase. World wide web electronic publication
- R Froese
Froese, R., Pauly, D. (Eds.), 2008. Fishbase. World wide web electronic publication.
www.fishbase.org.