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Studies of migratory fish species in Neotropical Basins have generally focused on adult fishes, especially on their reproductive migration, whereas sites of growth and refuge of juveniles remain poorly investigated. We aimed to evaluate if smaller rivers play a role in the life cycle of these species. We used 13 rivers of different sizes in the upper São Francisco Basin, Brazil. We found that smaller rivers, especially when draining regions close to floodplains, were the first places where juveniles moved after leaving floodplain lakes. We also found that individuals moved downstream as they grew, and were found in increasingly larger rivers that were more distant from floodplains. Currently, the best‐known strategy for conservation of neotropical migratory fishes is the maintenance of free‐flowing stretches encompassing necessary habitats for life cycle completion. We conclude that small tributaries near floodplain regions are also needed in these protected free‐flowing river systems. [ABSTRACT FROM AUTHOR]

This study assessed the effects of tidal stages and habitat conditions on nekton assemblage and distribution in the Kakum River estuarine mangrove system in the Central Region of Ghana. Teleosts and crustaceans were sampled using pole seine and cast net from a tidal mangrove pond and a channel, and characterised using morphometry and ecological guilds concept. In total, 1 146 specimens were collected, with 35 species from 19 families represented. The most abundant species encountered were Liza spp. (Mugilidae; 36%), Sarotherodon melanotheron (Cichlidae; 16%), Elops lacerta (Elopidae; 6%) and Sardinella aurita (Clupeidae; 5%), which exhibited pronounced spatial distribution. Sarotherodon melanotheron showed preference for ponds with minimal water flow and depth, Sardinella aurita occurred only in deeper sections of the mangrove channel with significant flow velocity, and Elops lacerta in the pond and all channel stations. Mugilids were found exclusively in the channel, whereas Palaemonidae (Macrobrachium macrobrachion and M. vollenhoveni) occurred in specific locations in the channel, with species- specific preferences for tidal stages. Most species encountered were identified to be predominantly marine migrants with bentophagous feeding habit. Site selection and tidal stages were found to affect the occurrence and distribution of fishes over a tidal cycle and interactively influence species diversity. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The effect of flooding phase and water quality on the littoral fish species of the Zambezi/Chobe floodplain was assessed between March 2017 and February 2018. Using the similarity percentage analyses (SIMPER), a 61.9% dissimilarity was detected in fish assemblages among the four flooding phases of the Zambezi/Chobe floodplain (rising, peak, recession and low flooding phase). Cichlids (63.1%) were the most dominant taxa during the peak flooding phase while cyprinids were dominant during the rising (40.7%), recession (45.3%) and low flooding phases (40.9%), respectively. Juveniles of the two commercially important species, Oreochromis andersonii and Coptodon rendalli, were among the four abundant species across the four flooding phases of the Zambezi/Chobe floodplain. Higher densities of these two species were in synchrony with the peak flooding phase, characterised by high levels of dissolved oxygen (5.7 ± 1.0 mg/L), neutral pH (7.9) and moderate water temperature (27.6 ± 1.1°C). During the flood recession phase, a severe decline in juvenile of the commercially important species (O. andersonii and C. rendalli) coincided with fish migration off the littoral zone into the main river at a mean size between 70 and 80 mm SL. Generally, the observed variations in the fish species composition during the different stages of flooding might reflect the influence of water quality and water volume to sustain large fish assemblages on the littoral zone of the Zambezi/Chobe floodplain. Any change in the natural flow and reduction in water volume of the Zambezi/Chobe floodplain might negatively affect the recruitment of juvenile fish into adult populations. [ABSTRACT FROM AUTHOR]

We evaluated connectivity, resiliency, and spatiotemporal variation in fish associations between the Tramandal River estuary (TRE) and the adjacent coast (AC). This was based on intermittent and seasonal data covering a discontinuous 21-year period (1995 to 2016) obtained using a standard beach seine with replicate samples collected at several points. In the TRE (405 samples; 42,987 individuals) 55 species were captured. In the AC (297 samples; 54,295 individuals) 41 species were captured. After data standardization the expected richness of the TRE [E(S) = 18.2] was significantly greater (P < 0.05) than that of the AC [E(S) = 14.4]. The fish association structure and distribution patterns in TRE and AC were dynamic and interconnected but quite different in terms of species composition, especially due to the influence of local salinity. The TRE association was richer in a number of species but numerically dominated by marine estuarine-dependent juveniles. The AC association was represented by a few typical marine species in addition to a couple of estuarine-related transient species who used the surf-zone as a passageway to enter the estuary. Even if there was a higher percentage of common species reported (30 out of 66), the monthly average Jaccard index of similarity (IJ = 28%) and the monthly average percent similarity index (IPS = 30%) were low, suggesting that the shallow water functional connectivity between AC and TRE was represented by few species that occur equally in abundance in both environments. Trachinotus marginatus and Mugil liza numerically dominated in the AC and M. liza, Mugil curema, and Atherinella brasiliensis at TRE. Juvenile M liza and M curema added up to >70% of the total individuals sampled in both environments. General linearized models (GLM) revealed that diversity was not influenced by interannual variations, evidencing that juvenile fish assemblage of AC and TRE are resilient through the years. Standardized beach samples are able to reveal long-term fluctuation in shallow estuarine fish communities but without an apparent loss in species composition, richness, and relative total abundance. The only observed interdecadal trend was the reduction in abundance of juvenile M. liza that seemed to parallel the reduction in abundance of the adult fishing stocks in southern Brazil.

Abstract Brackish lagoons, on the edge between marine and freshwater ecosystems, are vulnerable aquatic environments that act as nursery grounds for several of the most commercially exploited fish families. We used long-term passive gear data, to investigate whether the moon and tides affected fish movement between inner and outer habitats in a Northern Mediterranean coastal lagoon. In particular, we used multivariate, threshold and non-linear correlation analyses to explore the relationship between fish catches and moon and tide variables in transitional habitats, accounting for the presence of potential prey and other major temporal and environmental variables. Fish movements between habitats were influenced by moon and tide factors, which had effects comparable to annual and seasonal variations, respectively. Overall, the magnitude of effects related to the moon parameters were smaller than most environmental parameters examined, but still larger than e.g. the presence of invertebrate prey (lagoon shrimp) or some of the tide factors. European flounder catches were positively correlated with disk illumination, while sand and black goby were influenced by the moon phase. Other benthic and pelagic species showed no significant correlation. Tide direction affected negatively the movement of boxlip mullet and tide amplitude prior to sampling had far more effect than tide amplitude during sampling. Water temperature, salinity and the presence of invertebrate prey (grey shrimp) had significant but contrasting effects on some, but not all, of the species examined. Ultimately, this information could improve the understanding of the drivers in these ecosystem as well as potentially provide useful insights for improved fisheries management. Highlights • Juvenile fish movement in a brackish lagoon were influenced by moon and tide factors. • Moon and tide factors had effects comparable to annual and seasonal variations, respectively. • The magnitude of moon effects was smaller than most environmental parameters examined. • Some of the tide effects were smaller than moon effects. • Water temperature, salinity and invertebrate prey had significant but contrasting effects. [ABSTRACT FROM AUTHOR]

Temporal variations over short and medium time scales play an important role in fish assemblage dynamics, but have been poorly investigated in tropical estuaries. This study evaluates the hypothesis that fishes co-occurring on a tidal mudflat have different patterns of temporal segregation at short- and medium-term scales that optimize resource use and habitat partitioning. A total of 6222 individuals and 66 fish species were caught during different hours covering the entire 24 h cycle, tidal regimes and the wet and dry seasons. Biomass and species richness, and to a lesser extent CPUE and evenness, showed statistically significant interactions across short- and medium-term scales. Biomass was higher during the dry season and its oscillation along tidal cycles revealed distinct patterns over the photoperiod in each season. A similar complex pattern was also observed for species richness, which showed distinct temporal patterns between high and low tides over the photoperiod in each season. Overall, shorter-term variations on fish assemblage attributes were correlated mainly with photoperiod and, to a lesser extent, tidal regime. Medium-term variations in fish abundance and species richness, in contrast, could result from seasonality in recruitment patterns and higher availability of allochthonous food resources during the wet period. [ABSTRACT FROM AUTHOR]

Tropical ocean-exposed sandy beaches have an essential ecological function for marine fish species, which use these turbulent areas as nurseries. These habitats are characterized as homogeneous environments, but previous studies report the influence of drifting algae in providing physical structure, which increases habitat complexity and heterogeneity. This additional habitat complexity is expected to have a crucial impact on fish assemblages. Here, we analyzed the influences of wave exposure and drifting algae volume on abundance and functional diversity on two beach types: wave-dominated and tide-modified. Beach seine samplings were carried out in the rainy and dry seasons to collect the fish at each beach. Four volume categories of drifting algae were selected: bare sand, low, mid and high. A total of 97 fish species were captured. The community attributes of fishes (abundance, richness and biomass), as well as algal volume, were higher in tide-modified beaches. For abundance, three distinct patterns emerged: 1) there was a trend of decreasing herrings and anchovies compared to other species, from the bare to high-volume drifting algae in tide-modified beaches, with the opposite trend for the wave-dominated beaches; 2) L. breviceps , M. littoralis , S. naso , S. rastrifer and S. stellifer increased in abundance from the bare to high drifting algae in wave-dominated beaches; 3) P. virginicus was abundant in both beach types. These trends were accompanied by functional diversity, principally by responses in the two types of traits: diet and habitat use. The differences in habitat characteristics (wave exposure and drifting algae) among beaches affected the composition and functional diversity and consequently supported distinct fish assemblages. The presence of drifting algae in this habitat favors the attractiveness for fishes, such as larvae and juveniles, and seems to drive habitat use by tropical fishes. • The community attributes of fishes, as well as algal volume, were higher in tide-modified beaches. • There was a trend of decreasing herrings and anchovies compared to other species, from the bare to high-volume drifting algae in tide-modified beaches. • The increase in functional diversity was principally by responses in the two types of traits: diet and habitat use. • The presence of drifting algae in this habitat favors the attractiveness for fishes. [ABSTRACT FROM AUTHOR]

The distribution and feeding ecology of two puffer fish, Sphoeroides testudineus (Linnaeus, 1758) and Colomesus psittacus (Bloch & Schneider, 1801), were investigated in a tropical estuary (north-eastern Brazil). The hypothesis tested was that these two species partition available resources spatially, and that the effects of interspecific competition can be reduced by changes in the feeding strategy and using alternative resources. This study was carried out between February 2011 and January 2012, on a beach and three tidal creeks of the Mamanguape River estuary. Data on the distribution and relative abundance of the two species were collected using beach seine, with data on temperature, salinity and turbidity also recorded. The diets of the species (S. testudineus N = 399; C. psittacus N = 108) were analysed by the Index of Relative Importance (IRI). Sphoeroides testudineus was found in the entire area, but was particularly abundant in the upper estuary, while C. psittacus was captured exclusively in the upper estuary, with all individuals assumed to be juveniles. In regard to feeding, juvenile S. testudineus predated on Bivalves, Ceratopogonidae larvae, calanoids and gastropods; whilst C. psittacus showed a diet more specialized in Brachyura and Cirripedia. These results suggest that there are differences in both habitat utilization and feeding habits of these two puffer fish species in this estuary. [ABSTRACT FROM AUTHOR]

Stahr KJ, Kaemingk MA. 2017. An evaluation of emergent macrophytes and use among groups of aquatic taxa. Lake Reserv Manage. 00:1–10. Aquatic vegetation serves an important ecological role. Previous research on the interactions of macrophytes and aquatic organisms has focused primarily on submersed macrophytes due to their structural complexity and associated ecological impacts. However, the role of emergent vegetation is far less understood and often overlooked because they lack structural complexity. We evaluated 3 common emergent macrophytes and an open water habitat, and determined use among multiple aquatic taxa. Pelican Lake, Nebraska, USA, served as our study system because it is dominated by 3 emergent macrophytes: common cattail (Typha latifolia), softstem bulrush (Schoenoplectus tabernaemontani), and common reed (Phragmites australis). Juvenile fishes (yellow perch [Perca flavescens] and bluegill [Lepomis macrochirus]), zooplankton, and benthic macroinvertebrates were sampled concurrently in each habitat patch over 3 months (Aug, Sep, and Oct). We identified few clear or consistent overall patterns in habitat use among emergent vegetation species across these aquatic taxa. However, bluegill and some zooplankton taxa were more abundant in emergent vegetation compared to open water habitats. Conversely, habitat use for some macroinvertebrate taxa differed among emergent vegetation species. Our results suggest that managers could select from a variety of emergent vegetation species to address management objectives, while also balancing ecological and social tradeoffs. [ABSTRACT FROM PUBLISHER]

Channel reconfiguration is a common but debated method used to restore streams, often causing disturbance and producing subsequent negative impacts on biota. Here, we report results from short-term assessment (i.e., one and three years’ post-restoration) of habitat variables (e.g., reach depth, substrate, and canopy cover) and fish community composition and structure (using electrofishing surveys; e.g., proportion of juveniles and tolerant fishes) from a 675 m section of Eagle Creek (Portage County, OH, USA) restored using channel remeandering in August 2013. Mesohabitat analysis was not conducted as part of this study. Sites upstream and downstream of restoration efforts were also monitored. Surveys were completed in 10 separate 50 m stretches: one upstream control site, three new channel sites, two old channel sites, and three downstream sites. Following restoration, fish communities in downstream sites became more similar to new channel sites and diverged from the upstream control site over time, as reflected in increased proportions of juvenile and tolerant fishes. Shifts in fish communities were not explained by habitat variables. Diversity was significantly lower in new channel sites post-restoration than in the upstream control, while downstream sites remained similarly high in diversity compared to the upstream control site over time. Overall, in the short-term, new channel colonizing communities were unable to recover to reflect upstream community composition and structure, and fish communities downstream of restoration were negatively impacted. [ABSTRACT FROM AUTHOR]

Although mojarra species usually demonstrate a wide distribution in tropical and subtropical estuaries, relatively little is known about the process influencing the spatial resource partitioning to nearshore habitats. Therefore, the aim of this study was check the existence of habitat and food partitioning among confamiliar species in a hypersaline estuary. The dietary compositions of three co-occurring species of mojarras were determined, using samples collected with a beach seine from an inverse tropical estuary in Northeastern Brazil, during the rainy and the dry seasons of 2012. Eucinostomus argenteus and Ulaema lefroyi were abundant throughout the year, while Eugerres brasilianus was most abundant during the rainy season. Although these mojarras were found together in all areas of the estuary, there was evidence of habitat partitioning: E. argenteus and E. brasilianus were dominant in areas with submerged vegetation, while U. lefroyi was most abundant in areas with little habitat complexity and minimal shelter. All mojarras consumed, to different degrees, zooplankton, Bivalvia and Polychaeta. However, E. brasilanus also consumed a considerable amount of algae. Although the niches of the mojarra species appeared to significantly overlap, some resource partitioning patterns were apparent. While E. brasilanus was clearly different along the trophic niche, segregation of the other species was more important with respect to the spatial dimension. The different feeding strategies appear to minimize inter-specific overlap and allow the co-occurrence of these species in this hypersaline tropical estuary. [ABSTRACT FROM AUTHOR]

The spatial and temporal patterns in settlement of the juveniles of around 30 littoral species along the Croatian part of Adriatic Sea were studied from May 1998 to the present days. Sparidae was the most abundant family comprising 61,47% (13 species), followed by Labridae (10,37%, 11 species) and Atherinidae (9,35%, two species). The most abundant juvenile taxa were the sparid Boops boops and the atherinid Atherina boyeri accounting together for 76,91% of the total catch. Settlement intensity varied spatially, temporally and among species. Sparid species recruit at different times of the year, whereas labrids recruit during summer months, from July to September. Most of the juveniles studied settle to well defined habitats with characteristically distinctive substrate types. Depth was one of the main factors regulating the distribution of settlers. Sparid species recruit primarily in the shallowest zone (0 to 3 m), and most of them prefer varied bottoms (sand, gravel or rocky; vegetated or unvegetated). Labrid species show a high degree of seasonal and spatial co-occurrence, and are normally found on rocky substrates with high algal cover, while atherinids show no clear link with the type of substrates. Some species with similar habitat requirements show a clear seasonal segregation, with each species occupying successively the same zones at a different time of the year. Observed temporal staggering of recruitment was probably a mechanism for reducing possible interspecific competition. Settlement intensity to nearshore habitats exhibited high year-to-year variations at both local and regional scales. The implications of this study are important not only for better understanding the patterns of recruitment dynamics in various juvenile inshore populations, but also in terms of management of these resources in the Adriatic Sea.

Channel reconfiguration is a common but debated method used to restore streams, often causing disturbance and producing subsequent negative impacts on biota. Here, we report results from short-term assessment (i.e., one and three years’ post-restoration) of habitat variables (e.g., reach depth, substrate, and canopy cover) and fish community composition and structure (using electrofishing surveys; e.g., proportion of juveniles and tolerant fishes) from a 675 m section of Eagle Creek (Portage County, OH, USA) restored using channel remeandering in August 2013. Mesohabitat analysis was not conducted as part of this study. Sites upstream and downstream of restoration efforts were also monitored. Surveys were completed in 10 separate 50 m stretches: one upstream control site, three new channel sites, two old channel sites, and three downstream sites. Following restoration, fish communities in downstream sites became more similar to new channel sites and diverged from the upstream control site over time, as reflected in increased proportions of juvenile and tolerant fishes. Shifts in fish communities were not explained by habitat variables. Diversity was significantly lower in new channel sites post-restoration than in the upstream control, while downstream sites remained similarly high in diversity compared to the upstream control site over time. Overall, in the short-term, new channel colonizing communities were unable to recover to reflect upstream community composition and structure, and fish communities downstream of restoration were negatively impacted.

Dietary analysis was conducted on juveniles of 10 numerically abundant fish species inhabiting tropical seagrass beds in North Queensland, Australia. Gammarid amphipods were consumed by all of the species, but their contribution to the diet of each varied. Crab larvae and copepods contributed to the diets ofLeiognathus bindus,Pranesus endrachtensisandStolephorussp.; polychaetes and isopods were consumed bySillago maculata burrus,Lethrinussp.,Pelates sexlineatusandSiganus canaliculatus; andFavonigobius reichei,Coris caudimaculaandArothron manilensisfed on bivalves. Seagrass and gastropods were rarely ingested by most of these fishes, but made a moderate contribution to the diet ofA. manilensis.With the exception ofL. bindus, the diet of each species was correlated with size: smaller species consumed copepods, crab larvae and gammarid amphipods, while larger species ate polychaetes, bivalves, isopods and gastropods. Non-metric multidimensional scaling (MDS) ordination plots emphasised the variation in dietary composition between species, and showed that this was often correlated with mouth length and width of the fish—for example, species with larger mouth dimensions tended to have broader diets. These interspecific differences in dietary composition increase the number of food resources available to these fishes, thereby reducing the potential competition for resources within the fish community. [ABSTRACT FROM PUBLISHER]

Fish assemblages in an insular (preserved) and a continental (disturbed) sandy beach were compared to assess any changes that could be attributed to anthropogenic influences and/or the proximity of the fish spawning grounds. We expected that the closer geographical position to the spawning grounds and the small amount of anthropogenic disturbance on the insular beach would be likely to provide more suitable conditions for early fish development compared with the continental beach. A total of 192 samples (96 in each beach) were taken, yielding 68 fish species, mostly young-of-the-year. Fish assemblage structure differed significantly between the two beaches. Moreover, the insular beach had higher number of species, number of individuals and biomass compared with the continental beach. The commercially important Clupeiformes Harengula clupeola, Anchoa tricolor and Anchoa januaria, Perciformes Micropogonias furnieri and Mugiliformes Mugil liza were typical species on the insular beach, partitioning the seasonal use of the beach. On the other hand, a few abundant non-commercial species, mainly the Atheriniformes Atherinella brasiliensis and the Perciformes Eucinostomus argenteus and Diapterus rhombeus, occurred all year round at the continental beach. The high fish richness and abundance and the more conspicuous species turnover across seasons on the insular beach are probable indications of more complex and dynamic organization of the communities favored by better geographical position and less anthropogenic disturbance in the area. [ABSTRACT FROM AUTHOR]

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Abstract: In the California Current coastal boundary zone, the spring transition between downwelling and upwelling conditions, along with the fluctuating structure of the Columbia River plume, creates highly dynamic interactions. In this study, we investigated whether the surface distribution of brachyuran larvae and ichthyoplankton would track the dynamics of the Columbia River plume. By happenstance, the cruise period coincided with the spring transition from downwelling to sustained upwelling conditions in 2010, a year when the transition was delayed and Columbia River flow was substantially higher than average. We used time series of wind and freshwater input to evaluate the influence of physical forcing on oceanographic patterns, and sampled hydrography and surface plankton concentrations within a 182km2 grid off Willapa Bay, WA. Additionally, two longer transects, one cross-shelf and the other along-shore, were made to discern the extent of plume influence on larval crab and fish abundance. We found that plume waters that were trapped in a northward-flowing coastal-boundary current during downwelling conditions were advected offshore after several days of upwelling-favorable winds. Neustonic collections of brachyuran larvae and ichthyoplankton varied in response to this large seaward advective event. Megalopae of cancrid crabs exhibited patterns of both offshore transport (Cancer oregonensis/productus) and nearshore retention (C. magister). Additionally, abundant numbers of large juvenile widow (Sebastes entomelas) and yellowtail (S. flavidus) rockfish of a size appropriate for settlement were sampled during a period when ocean conditions favored high recruitment success. These results demonstrated that the response of planktonic crab larvae and ichthyoplankton to large-scale advection varied by species, with larger and more vagile fish exhibiting less evidence of passive transport than smaller crab larvae. Importantly, portions of the planktonic fish and crab community were able to maintain nearshore distributions in favorable settlement habitat, despite physical advection offshore. [Copyright &y& Elsevier]

Whereas diel fish migration between mangrove and seagrass habitats has been recognized for decades, quantitative studies have focused mainly on diurnal patterns of fish distribution and abundance. In general, previous studies have shown that fish abundances decline with increasing distance from mangroves; however, evidence for such a pattern at night, when many fishes are actively feeding, is scarce. The present study is the first to report nocturnal fish abundances along a continuous distance gradient from mangroves across adjacent seagrass habitat (0–120 m). Here, we used nocturnal seine sampling to test the null hypothesis (based on diurnal studies and limited nocturnal work) that fish abundance would decrease with increasing distance from shoreline. We focused on species and life-stage-specific abundance patterns of Lutjanus griseus, Sphyraena barracuda, Archosargus rhomboidalis, and Haemulon sciurus. Results indicated that assemblage composition and structure differed significantly by season, likely influenced by temperature. However, within each season, the fish habitat use pattern at both the assemblage and species-specific level generally failed to support our working null hypothesis. Species-specific analyses revealed that, for most species and life-stages examined, nocturnal abundance either did not change with distance or increased with distance from the mangrove-seagrass ecotone. Our results suggest that analyses where taxa are grouped to report overall patterns may have the potential to overlook significant species- and stage-specific variation. For fishes known to make nocturnal migrations, we recommend nocturnal sampling to determine habitat utilization patterns, especially when inferring nursery value of multiple habitats or when estimating fish production. [ABSTRACT FROM AUTHOR]

The presence of multiple habitat types results in differences in provision types and functions for a number of fish species along tropical estuaries, which use these ecosystems as nursery, feeding, and reproduction grounds. We compared fish assemblages along three habitat types (beaches, mudflats and mangrove fringes) in a tropical estuary using samples collected during rainy and dry seasons. A total of 11,260 individuals belonging to 31 families and 93 species were collected. The abundance and biomass of fishes declined from mudflats and mangrove fringes to beaches, with the highest values occurring in the dry season. Species richness showed the same tendency. Temporal trends were found among habitats during this study. Overall, 56 fish species were recorded in at least two habitats, and only 19 species were recorded in all three habitats; the number of species recorded only in mangrove fringes was higher than in other habitats. The fish composition between mudflats and mangrove fringes was more similar, indicating that connectivity plays an obvious and crucial role in the movements of fishes between them. A combination of four (salinity, coarse sand, clay, and organic matter) and three (salinity, coarse sand, and organic matter) environmental predictors accounted for 94.8% of the variation in abundance and 94.7% of the variation in biomass in the fish community structure among estuarine habitats. The multiple habitat types in this tropical estuary maximize opportunities for the survival and growth of numerous fish species. Specifically, we show that there was high similarity in species composition among habitats, which reinforces the hypothesis that most juvenile fishes do not necessarily move from one shallow habitat to another, but simply occupy shallow estuarine waters regardless of habitat type. • Fish assemblages from estuarine mangroves, mudflats and beaches were assessed. • Juvenile fish stages were dependent on multiple habitats as nursery ground. • Majority of fish species (56 species) inhabit multiple habitats. • Similar fish composition between mudflats and mangroves suggests spatial links between habitats. • Sediment grain size and salinity are relevant predictors of fish abundance and biomass. [ABSTRACT FROM AUTHOR]

Abstract: Shallow soft-bottom habitats including mangroves and mudflats provide important nursery functions for juvenile fishes, but little information exists concerning the relative nursery value of these habitats for juvenile fishes. We compared the potential of a mangrove and a mudflat in a semi-enclosed bay in Hong Kong to serve as fish nurseries by measuring species composition, dietary composition, gut fullness and diet breadth of juvenile fishes. Fish abundance was higher in mangrove than mudflat, but species richness was almost similar between the two habitats. After excluding Ambassis gymnocephalus, which was found mainly in the mangrove, difference in fish abundance between the two habitats was small. The gut fullness and diet breath of most species did not differ between mangrove and mudflat, suggesting that the two habitats were very similar in terms of providing feeding opportunity for juvenile fishes. While the importance of mangrove as nursery of fishes has been repeatedly emphasized, our data suggest that other soft-bottom habitats, such as mudflats, are also important and need to be protected. [Copyright &y& Elsevier]

Otolith chemical composition differed between juveniles of five fish species ( Solea solea, Solea senegalensis, Platichthys flesus, Diplodus vulgaris and Dicentrarchus labrax) in nursery areas of six estuaries along the Portuguese coast (Douro, Ria de Aveiro, Mondego, Tejo, Sado and Mira). Spatially consistent patterns in the concentration of some elements were responsible for differences between species. Discrimination of estuaries using data from all species simultaneously averaged 44·7% of correctly classified cases, whilst discrimination of species averaged 76·2%. Moreover, species-related patterns in otolith fingerprints were highlighted when comparing species for each estuarine nursery area, with intra estuarine species discrimination averages ranging from 86·2 to 100·0%. Similarities in the otolith elemental fingerprints were larger between species with close phylogeny and ecology, particularly between flatfish and perciform species. In addition to the differences in physiological regulation of species, specific microhabitat use in a common environment was suggested as a relevant factor for the differentiation of otolith chemistry among species occurring in the same locations. Despite positive results in specific estuaries, variation in otolith composition limited the use of species as proxies to classify others to their system of origin. [ABSTRACT FROM AUTHOR]

Abstract: The Magnuson-Stevens Fishery Conservation and Management Act defines essential fish habitat (EFH) as “the waters and substrate necessary to fish for spawning, breeding, feeding, and growth to maturity” and the protection of nursery areas has become a key element in US Federal fisheries management. Distribution and abundance by habitat for age-0, young-of-the-year (YOY) winter flounder, Pseudopleuronectes americanus, were compared for 28 Maine estuaries to help define essential fish habitat for this life history stage. The Maine coast was divided into three broad geographic zones based upon geological features and sampled over 5 consecutive years; during April–November of 2000 in the Mid-coast, in 2001 and 2002 along the Southwest coast and in 2003 and 2004 along the Eastern Maine coast. One beam trawl (2.0m width, 3mm mesh) sample was collected in one to four habitats in estuaries: eelgrass (Zostera marina), kelp (Laminaria longicruris), drift algae (Phyllophora sp.) and unvegetated sand/mud. Fish were sampled every 2 weeks, April–November 2000–2004. Abundance of YOY winter flounder was greatest in Mid-coast estuaries between Casco and Penobscot Bays and was significantly lower in Southwest and Eastern estuaries. Abundance was similar across all four habitats in Mid-coast estuaries in 2000. In the other years, YOY were found in higher abundance in eelgrass relative to other habitats. A logistic regression model based on nearshore habitat characteristics was developed to predict the distribution of this species along the three broad geological zones of the Maine coast with the physical and biological variables most important in discriminating between habitats with and without individual fish identified. This logistic regression model correctly classified winter flounder 72.4% of the time based on the year, zone, the physical habitat variables (temperature, salinity, depth) and the presence–absence of submerged aquatic vegetation (eelgrass, kelp or algae). These results indicate that the type of habitat most important to YOY winter flounder varies among estuaries and EFH for this species and life stage must be defined with care. [Copyright &y& Elsevier]

We compared benthic community structure among stands of Typha angustifolia (narrow-leaf cattail) and herbicide-treated (Glypro) and untreated Phragmites australis (common reed) over two summers in a Lake Erie coastal wetland (i.e., drowned river mouth). Both macrophytes are invasives, but only Phragmites is currently controlled by herbicides because of its reputed "undesirable" effects on wetland community structure and function. Macroinvertebrate diversity was similar among stand types and relatively high (Shannon-Weaver indices ∼2.6-4.2), probably because of high system primary productivity and a mix of lentic and riverine species. Proportions of macroinvertebrate functional feeding groups were also similar, but Jaccard's similarity indices were relatively low (29%-57%), suggesting macroinvertebrate compositional differences among stand types. Coleopterans particularly affected species presence/absence patterns, but their presence was associated with low water level rather than hydrophyte type per se. Moreover, total macroinvertebrate densities were greater in both Phragmites treatments than in Typha; a pattern generated mostly by gastropods (≥ 95% Gyraulus deflectus and Physella gyrina) and chironomids. Microalgal food supply likely plays a part in explaining these density differences, given diatom-dominated epiphyton was denser on submerged shoots of Phragmites than on Typha. Common diatom assemblages were similar among stand types, but species richness was significantly greater on untreated-Phragmites than on herbicide-treated, early senescent Phragmites and untreated-Typha. However, advanced senescence from herbicide application (∼3 months) did not apparently affect macroscale habitat suitability and structure above and below the waterline, given counts of ovipositing odonates (mostly Isehnura and Enallagma) and captures of juvenile fishes (> 90% Lepomis spp.) were similar among stand types. Overall, our results suggest that benthic community structure is comparable between similarly-aged stands (∼4 yrs old) of invading reed and cattail and is not directly or indirectly affected by Glypro application. [ABSTRACT FROM AUTHOR]

The relative importance of bay habitats, consisting of mangrove creeks and channel, seagrass beds, and mud and sand flats, as feeding grounds for a number of fish species was studied in Chwaka Bay, Zanzibar, Tanzania, using gut content analysis and stable isotope analysis of carbon and nitrogen. Gut content analysis revealed that within fish species almost the same food items were consumed regardless of the different habitats in which they were caught. Crustaceans (mainly copepods, crabs and shrimps) were the preferred food for most zoobenthivores and omnivores, while fishes and algae were the preferred food for piscivores and herbivores, respectively. The mean δ13C values of fishes and food items from the mangrove habitats were significantly depleted to those from the seagrass habitats by 6·9 and 9·7‰ for fishes and food items, respectively, and to those from the mud and sand flats by 3·5 and 5·8‰, respectively. Fishes and food items from the mud and sand flats were significantly depleted as compared to those of the seagrass habitats by 3·4 and 3·9‰, for fishes and food, respectively. Similar to other studies done in different geographical locations, the importance of mangrove and seagrass themselves as a primary source of carbon to higher trophic levels is limited. The different bay habitats were all used as feeding grounds by different fish species. Individuals of the species Gerres filamentosus, Gerres oyena, Lethrinus lentjan, Lutjanus fulviflamma, Pelates quadrilineatus and Siganus sutor appeared to show a connectivity with respect to feeding between different habitats by having δ13C values which were in-between those of food items from two neighbouring habitats. This connectivity could be a result of either daily tidal migrations or recent ontogenetic migration. [ABSTRACT FROM AUTHOR]

A modification(termed the slide-glass-embed-method, SGEM) of the embed method for preparing fish sagittae is described. The SGEM is based on a very simple principle: a dome of mixed resin containing the embedded sagittae loses hardness after being heated and can be easily cut with dissecting scissors. [ABSTRACT FROM AUTHOR]

The mining of sand resources from the inner continental shelf for beach nourishment may lead to impacts or increase stress on commercial and noncommercial living resources that utilize these areas. The objective of our work was to characterize benthos present in areas likely to be mined and to predict impacts of sand mining. In 1998 and 1999 we used a combination of methods (grab samples, sediment profile cameras, video sled, and trawl) to collect data on the benthos, both fishes and invertebrates, which utilized several potential sand mining areas. We found benthic communities and fish assemblages to be typical of middle Atlantic sandy inner continental shelf habitats. A sand mining scenario that removed the top meter of sand from Fenwick Shoal would disturb approximately 7.7 km² with the potential acute impact on noncommercial sessile species being the loss of about 150 × 106 individuals representing 300 kg of wet weight biomass that could have functioned as trophic support to fishes. In addition, mobile species would be displaced and have to search for replacement habitat. To minimize impacts and promote recolonization of mined areas the total removal of substrate should be avoided. Small areas with a project area should be left to serve as refuge patches that would promote recolonization and serve as habitat for mobile species. Predicted impacts on demersal fishes would be lessened by a rapid recolonization, particularly the recovery of mobile epifaunal crustacean that serve as the primary trophic support species. Project timing and engineering could also be used to lessen impacts on fishes by reducing stress on crustaceans. For example, mining activities that ended in time for Spring/Summer recruitment would favor crustaceans while a Fall/Winter end would favor annelids. [ABSTRACT FROM AUTHOR]

We conducted a series of size-structured laboratory experiments to quantify and compare the susceptibility of several estuarine and marine forage fishes to attack and capture by piscivorous predators. Size-dependent estimates of capture success, handling time, and prey profitability were generated from single-species experiments offering bay anchovy, Atlantic menhaden, Atlantic silverside, and age-0 striped bass to piscivores. Bay anchovy and Atlantic menhaden were most susceptible to capture and yielded high profitability compared to Atlantic silverside and age-0 striped bass prey. Variation in capture success among forage species was particularly influential in generating disparate profitability functions. Although morphological differences among forage species contributed to variation in susceptibility to predation, behavioral analyses indicated that variable reaction distances to approaching predators and activity levels of prey may explain a large fraction of the observed differences in susceptibility. When several forage species were offered to predators simultaneously in larger enclosures, mortality was highest and occurred earlier for bay anchovy and Atlantic menhaden compared to other prey, which points to the strong influence of predator capture success on overall forage fish vulnerability. Our results demonstrate species-specific differences among forage fishes in the ability to avoid attack and capture by piscivores, and we conclude that the expression of antipredator behaviors contributes significantly to variation in forage species vulnerability. [Copyright &y& Elsevier]

Daphnia lumholtzi comprises a substantial component of the zooplankton community during mid- to late-summer in Lake Chautauqua, a floodplain lake along the Illinois River near Havana, Illinois. In order to quantify the utilization of D. lumholtzi by juvenile fishes, diet analyses were conducted for seven juvenile fish species collected from Lake Chautauqua during the 2001 annual drawdown period. Freshwater drum Aplodinotus grunniens and emerald shiner Notropis atherinoides demonstrated negative selectivity for D. lumholtzi relative to native zooplankton species whereas four species of fish (bluegill Lepomis macrochirus , white bass Morone chrysops , white crappie Pomoxis annularis and black crappie Pomoxis nigromaculatus ) consumed substantial amounts of D. lumholtzi . Although selectivity values for D . lumholtzi varied among these fish species, positive selection for D. lumholtzi increased similarly among larger size classes of each fish species, and corresponded with ontogenetic shifts in diet. Mean body length of D. lumholtzi consumed by 20–69 mm L T juvenile fishes ranged from 0·75 to 0·99 mm with a calculated total length range of 2·0–2·6 mm. Results from this study provide evidence that high abundances of D. lumholtzi in mid- to late-summer provide an additional food source for several juvenile fish species during a time when abundances of large native cladoceran species (i.e. Daphnia ) are low, and juvenile fishes are searching for larger prey associated with ontogenetic shifts from zooplankton to macroinvertebrates and fishes. Because zooplankton production is typically lower in rivers than in lakes, survivorship of juvenile fishes produced in floodplain lakes may be higher in riverine systems if they are not reliant on zooplankton as a primary food resource. Therefore, high abundances of D. lumholtzi may benefit juvenile fishes in managed floodplain lakes, such as Lake Chautauqua, by increasing growth and... [ABSTRACT FROM AUTHOR]

Although the total migratory activity of fishes from floodplain lakes in the Lower Rhine (Germany) into the connected drainage channels, estimated using electrofishing, fyke nets and visual observations, was low during summer 1997, conspicuous diel migrations of adult bream Abramis brama in June and July were recorded in one of the channels studied. A considerable proportion of the population of the floodplain lake immigrated into the channel at dusk and left it at dawn. During two winters (1994–1995, 1997–1998) the abundance of fishes increased considerably in the channels. The winter migrations, studied in detail in one of the channels in 1997–1998, started in late October, when the water temperature dropped below 10° C. In contrast to the mean of 500 fishes per 100 m channel length between May and October, >5000 fishes were found from November to March, with maximum values of >50 000 fishes per 100 m channel length in February 1998. More than 90% of these shoals were 0+ year fishes, dominated by roach Rutilus rutilus, bream, perch Perca fluviatilis and rudd Scardinius erythrophthalmus. These shoals entered the channel at sunrise and left it around sunset. Generally, the 0+ year fishes in the shoals swam separately from the older fishes, and different reactions towards the attack of predatory fishes were observed. The migrating shoals of juvenile fishes during the winter were interpreted as a strategy to minimize predation risk.Copyright 2002 The Fisheries Society of the British Isles. Published by Elsevier Science Ltd. All rights reserved. [Copyright &y& Elsevier]

We characterized demersal fish and decapod crustacean habitats in 14 shallow (< 12 m) areas in Penobscot Bay, Maine, by mapping the distribution of subtidal substrata with an acoustic sea bottom profiler. We identified the aquatic vegetation and the fishes and decapods associated with these habitats. Samples of fishes and decapods in each habitat were collected with a small beam trawl. The seabed at most of the stations sampled was composed of a mosaic of substrata. More species of fishes tow-1 and higher abundances of fishes and decapods were found in stations with vegetation present, particularly eelgrass, Zostera marina. Decapod species richness tow-1 was similar between vegetated and unvegetated habitats. Shallow habitats in Penobscot Bay were dominated by juvenile fishes and function as nursery areas. The greater species diversity and higher abundances of epibenthic fishes and decapod crustaceans observed in vegetated habitats, particularly beds of Zostera marina, compared with unvegetated areas in Penobscot Bay conform to the hypothesis that increased habitat complexity results in increased species richness and abundance. [ABSTRACT FROM AUTHOR]

The lowest frequency of metacercariae of Posthodiplostomum cuticola on the bodies of six young-of-the-year cyprinid species was found on the head and ventral body. Metacercariae distribution differed among host species which may have been related to the behaviour of the fish host. [Copyright &y& Elsevier]