Fish Habitat Use Research Articles

Linking Hydroclimate to Fish Phenology and Habitat Use with Ichthyographs.

Streamflow and water temperature (hydroclimate) influence the life histories of aquatic biota. The relationship between streamflow and temperature varies with climate, hydrogeomorphic setting, and season. Life histories of native fishes reflect, in part, their adaptation to regional hydroclimate (flow and water temperature), local habitats, and natural disturbance regimes, all of which may be affected by water management. Alterations to natural hydroclimates, such as those caused by river regulation or climate change, can modify the suitability and variety of in-stream habitat for fishes throughout the year. Here, we present the ichthyograph, a new empirically-based graphical tool to help visualize relationships between hydroclimate and fish phenology. Generally, this graphical tool can be used to display a variety of phenotypic traits. We used long-term data sets of daily fish passage to examine linkages between hydroclimate and the expression of life-history phenology by native fishes. The ichthyograph may be used to characterize the environmental phenology for fishes across multiple spatio-temporal domains. We illustrate the ichthyograph in two applications to visualize: 1) river use for the community of fishes at a specific location; and 2) stream conditions at multiple locations within the river network for one species at different life-history stages. The novel, yet simple, ichthyograph offers a flexible framework to enable transformations in thinking regarding relationships between hydroclimate and aquatic species across space and time. The potential broad application of this innovative tool promotes synergism between assessments of physical characteristics and the biological needs of aquatic species.

Temperature‐ and light‐dependent ratio of energy gain to metabolic costs explains spatial and temporal habitat use of zooplanktivorous fish

AbstractUnderstanding the forces that drive habitat selection of species in communities is important in both ecology and evolution. In nature, species face variation in competition, predation and physical characters among habitats. Vendace (Coregonus albula (L.)) is a specialised zooplanktivorous fish predominantly using deeper water in lakes during summer, while roach (Rutilus rutilus (L.)) uses mainly the shallow littoral zone as well as the upper layer of the pelagic zone. To understand mechanisms behind habitat use of these species, I first conducted a predation experiment to investigate their sensitivity to predation by perch (Perca fluviatilis L.). Second, I performed a foraging experiment using different temperature and light treatments. I then used metabolic calculations to estimate energetic costs when foraging. I found no difference between species regarding sensitivity to predation. Vendace was the most efficient forager on zooplankton but also swam faster spending more energy compared to roach. Roach had a comparatively high metabolic rate in the lowest temperature, where their foraging efficiency was lowest. The energy gain ratio at 6°C was highest for vendace, while it was lowest for roach. In the highest temperature (18°C) and the lowest light level (1 lux), both species were similar in their energy gain ratio. The relative energy gain ratio provides a mechanism to explain habitat distribution for the two species. An increased understanding of the role of metabolism in combination with biotic interactions and habitat use may help to foresee effects of environmental change for different species.

Coral colony size and structure as determinants of habitat use and fitness of coral-dwelling fishes

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 553:163-172 (2016) - DOI: https://doi.org/10.3354/meps11745 Coral colony size and structure as determinants of habitat use and fitness of coral-dwelling fishes Pedro Henrique Cipresso Pereira*, Philip L. Munday College of Marine and Environmental Sciences and ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia *Corresponding author: pedro.pereira@my.jcu.edu.au ABSTRACT: Competition for space affects patterns of habitat use and individual performance of coral-dwelling fishes; however, the physical attributes of corals that influence habitat preferences are uncertain. In this study, we investigated the influence of coral colony size and branching structure of 2 coral species, Acropora nasuta and Acropora spathulata, on habitat use and growth rate of 2 coral gobies, Gobiodon histrio and G. erythrospilus. First, we examined 2 key aspects of coral colony structure (interbranch depth and interbranch width) that may influence habitat preferences. We then used laboratory and field-based experiments to test the effects of coral species, coral colony size and branching structure on habitat preference and growth rates of G. histrio and G. erythrospilus. The preferred coral species, A. nasuta, had smaller interbranch width than A. spathulata. A binary-choice laboratory experiment demonstrated that both goby species preferred coral colonies with smaller interbranch width, except when they had the opportunity to occupy A. nasuta over A. spathulata. A field transplant experiment showed that both goby species grew faster on larger coral colonies and in colonies with smaller interbranch width. G. erythrospilus grew faster than G. histrio on A. spathulata, indicating that it suffers less fitness loss when occupying this alternative habitat. Our results show that coral physical attributes are important factors driving habitat preference of coral-dwelling gobies; however, there must also be additional factors that influence their habitat use. Declining average coral size and reduced habitat complexity on coral reefs could have significant impacts on the performance of fishes, affecting ecological processes such as competition. KEY WORDS: Habitat complexity · Competition · Growth rate · Goby · Gobiodon spp. · Acropora spp. Full text in pdf format PreviousNextCite this article as: Pereira PHC, Munday PL (2016) Coral colony size and structure as determinants of habitat use and fitness of coral-dwelling fishes. Mar Ecol Prog Ser 553:163-172. https://doi.org/10.3354/meps11745 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 553. Online publication date: July 14, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Differences in movements of northern pike inhabiting rivers with contrasting flow regimes

AbstractLittle is known about the effect of short‐term flow changes on the movement of northern pike (Esox lucius L.). We conducted a comparative study in two rivers with different flow regimes (i.e. one regulated and one unregulated) to evaluate the extent to which adult northern pike movement is influenced by short‐term river flow conditions. Data on northern pike hourly movement were collected in northeastern Ontario on 40 individuals in the Mississagi River, a river subjected to extreme daily flow variations associated with hydro‐electric operations (i.e. hydropeaking), and the Aubinadong River, an unregulated river. Using manual tracking by radio‐telemetry, we found that northern pike moved at a higher rate in the river subjected to short‐term changes in river flow than in the unregulated river. Results also show that the relationship between movement of northern pike and flow can vary among rivers. In the Mississagi River, flow had a significant positive effect on northern pike activity, while the effect of flow in the Aubinadong River depended on water temperature. Moreover, fish in the Mississagi River utilized a restricted river section and travelled more laterally in comparison to fish inhabiting the Aubinadong River, where longer upstream‐downstream movements were more common. The present study contributes to our understanding of the effects of short‐term changes in flow on fish movement. This constitutes the first step towards assessing the effect of flow on fish habitat use, and eventually developing flow management strategies to mitigate impacts on fish. Copyright © 2016 John Wiley & Sons, Ltd.

Resource selection by juvenile pallid sturgeonScaphirhynchus albus(Forbes and Richardson, 1905) in the channelized Missouri River, Nebraska, USA

Habitat selection has been quantified for age-0 and adult pallid sturgeon Scaphirhynchus albus Bull. Illinois State Lab. Nat. Hist., 7, 1905, 37, but little is known regarding habitat use of the juvenile fish. The objective of this study was to quantify habitat use and selection of juvenile pallid sturgeon in the Missouri River, Nebraska, USA. Thirty-seven age-4 pallid sturgeon with transmitters were released in July of 2014, plus an additional 21 in September, with habitat monitored using biotelemetry. Age-1 and age-4 hatchery reared pallid sturgeon were found to avoid areas associated with the outside bend and thalweg habitats that were characterized by rapid water velocity (>1 ms−1), which accounted for 50% of the area in the channelized Missouri River. Age-1 pallid sturgeon selected an off-channel habitat and inside bend habitat while age-4 pallid sturgeon selected an off-channel and inside bend channel border habitat. Juvenile pallid sturgeon in unaltered rivers have been shown to associate with island tips and sand bars, habitat that is largely absent in the channelized Missouri River. This study indicates that juvenile pallid sturgeon in the Missouri River, Nebraska are selecting habitats with shallow water and slow water velocity, similar to those associated with island tips and sand bars in unaltered reaches.

Temporal soundscape patterns and processes in an estuarine reserve

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 550:25-38 (2016) - DOI: https://doi.org/10.3354/meps11724 Temporal soundscape patterns and processes in an estuarine reserve Shannon W. Ricci1,*, David B. Eggleston1,2, DelWayne R. Bohnenstiehl1, Ashlee Lillis1,3 1Department of Marine, Earth & Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina 27695-8208, USA 2Center for Marine Sciences and Technology, North Carolina State University, Morehead City, North Carolina 28557, USA 3Present address: Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA *Corresponding author: swbrown@ncsu.edu ABSTRACT: Underwater acoustic recordings can be used to measure the distribution and activity of sound-producing species and investigate variability in the physical and biological characteristics of marine ecosystems. This study characterized the summer soundscape of a coastal estuarine reserve, Middle Marsh, near Beaufort Inlet, North Carolina, USA. Passive recorders were deployed at 8 sites, within a mixture of seagrass, saltmarsh, oyster reef and soft-bottom habitats, and sampled for 2 min every 20 min between June and August 2014. Sound pressure levels (SPLs) in a high-frequency band (7-43 kHz) exhibited a periodicity of once per day, being 11 dB higher during the nighttime. This pattern is correlated with snapping shrimp sounds, with an average excess of ~12% more snaps detected at night. The same analysis for SPLs in a low-frequency band (150-1500 Hz) revealed a periodicity of twice per day, with diurnal sound levels varying by up to 29 dB. Temporal variability in the low-frequency soundscape is correlated with fish chorusing, as well as tidal water level, which may influence both the presence and absence of fish and the propagation of sound in the water column. The greatest SPLs are observed in association with periods of high biological activity during nighttime high tides. Sampling marine animals and their activities over ecologically relevant time scales is challenging using conventional techniques (trawls and throw traps) within complex shallow water habitats, particularly at night. Soundscape monitoring provides an additional method to assess spatiotemporal variation in essential fish habitat use within a complex mosaic of habitat types. KEY WORDS: Passive acoustics · Habitat-related sound · Soundscapes · Estuarine habitats Full text in pdf format Supplementary material PreviousNextCite this article as: Ricci SW, Eggleston DB, Bohnenstiehl DR, Lillis A (2016) Temporal soundscape patterns and processes in an estuarine reserve. Mar Ecol Prog Ser 550:25-38. https://doi.org/10.3354/meps11724 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 550. Online publication date: May 25, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Assessing the transferability of hydraulic habitat models for juvenile Atlantic salmon

Hydraulic habitat models are logistically and technically challenging and expensive to produce. They are therefore frequently transferred between rivers, often with different environmental conditions, without validation. Although studies have recognised problems with model transfer, few have assessed the consequences for model predictions. This study investigated the local (within sub-catchment) transfer of hydraulic habitat models developed for Atlantic salmon (Salmo salar) fry. Two adjacent reaches were chosen for the study, each containing pool, riffle, glide and run habitats. Detailed topographic surveys were used to develop hydraulic models for the study reaches. Substrate and cover were characterised using transects. Seasonal fish habitat use was characterised by electrofishing. Uniform saturation stocking was employed to ensure standard starting densities across all habitats. Generalised additive models were fitted to fry abundance data. Depth, velocity, dominant substrate and cover were used as predictor variables. The distribution of depth, velocity, dominant substrate and cover differed between the two reaches, but was consistent within reaches across seasons. Substrate exhibited the greatest inter-reach difference. Velocity and depth were the most important individual predictors of fry abundance, with the highest densities observed at moderate velocities (∼0.4ms−1) and low depths (∼0.1m) across all seasons. When models were transferred locally between reaches, those that were adjusted for inter-reach differences in mean fry abundance (i.e. those predicting changes in relative abundance) performed better than those transferred without adjustment. Complex models that included substrate and cover typically explained some of the variation in abundance in the transferred reach but performed less well than models containing hydraulic parameters alone. This potentially reflected inter-reach differences in the distribution of substrate and cover. This study suggests that (1) uniform stocking is useful for examining habitat-abundance relationships free from the influence of patchy egg deposition; (2) habitat models should be developed at sites offering maximum environmental complexity at a local level; (3) scientists and managers should avoid transferring models between locations with different environmental characteristics, especially in the absence of model validation; (4) complex models should be avoided, and those containing hydraulic variables alone should be considered, if predictions of habitat quality are to be made at new sites.

Risk assessment of polychlorinated biphenyls (PCBs) and trace metals in River Nile up- and downstream of a densely populated area.

Cairo city is the largest populated area along the whole course of River Nile with a wide range of anthropogenic activities. Efforts to restore fish habitat and recreational use of the river have raised concerns about its water, sediment and biota quality. This study provides a baseline data on the levels of PCBs and trace metals in River Nile along Cairo sector and implements the formulation of monitoring activities of the river's pollution status. Water, sediment and Nile tilapia (Oreochromis niloticus) samples were collected during summer season, 2013 from two sites, up- and downstream, for detection and determination of 11 PCB congeners (PCBs 28, 44, 52, 70, 101, 105, 118, 138, 152, 180 and 192) as well as six trace metals (Cu, Zn, Mn, Cd, Pb and Fe). Evidences of long- or short-term exposures to these contaminants as well as its accumulation tendency were assessed by integrating the obtained analytical results of biotic and abiotic components of this aquatic ecosystem. All calculated lifetime cancer risk values for PCBs showed unacceptable risk of cancer for human consumers at both normal and subsistence fish consumption rates. The calculated hazard index for total PCBs indicates that fish are not safe for human consumption except in site 1 at normal consumption rate. Meanwhile, trace metals do not pose unacceptable risks at both consumption rates except for Pb in site 1 at subsistence consumption rate.

Fatty acid profiles are biomarkers of fish habitat use in a river-floodplain ecosystem

Fatty acid (FA) analyses of fish tissues offer the potential to gain new knowledge of habitat- or forage-specific energy inputs to fishes in river-floodplain ecosystems, although limited information exists regarding among-habitat differences in FA biomarkers. The goal of this study was to determine if differences in fish FA profiles among main channel and connected and disconnected floodplain lakes exist in large river-floodplain systems. Bluegill Lepomis macrochirus FA profiles were generated to assess differences among two reaches of the Illinois River, USA, and its connected and disconnected floodplain lakes and determine whether FA signatures could be used to reclassify fish to their source habitat. Bluegill FA profiles differed among habitats and river reaches, including differences in levels of individual FAs (e.g., 18:2n−6, an indicator of allochthonous inputs, was higher among main channel fish) and FA groupings (e.g., n−3:n−6 FA ratio, an indicator of aquatic primary productivity, was higher among floodplain lake fish), which enabled >87.5% reclassification accuracy of fish to their source environment. We demonstrated that bluegill FA profiles differed among reaches and laterally among river channel and floodplain habitats, suggesting that FA profiles can be used to infer recent habitat use and habitat-specific foraging of fishes in large river-floodplain ecosystems.

Ice cover affects the growth of a stream-dwelling fish.

Protection provided by shelter is important for survival and affects the time and energy budgets of animals. It has been suggested that in fresh waters at high latitudes and altitudes, surface ice during winter functions as overhead cover for fish, reducing the predation risk from terrestrial piscivores. We simulated ice cover by suspending plastic sheeting over five 30-m-long stream sections in a boreal forest stream and examined its effects on the growth and habitat use of brown trout (Salmo trutta) during winter. Trout that spent the winter under the artificial ice cover grew more than those in the control (uncovered) sections. Moreover, tracking of trout tagged with passive integrated transponders showed that in the absence of the artificial ice cover, habitat use during the day was restricted to the stream edges, often under undercut banks, whereas under the simulated ice cover condition, trout used the entire width of the stream. These results indicate that the presence of surface ice cover may improve the energetic status and broaden habitat use of stream fish during winter. It is therefore likely that reductions in the duration and extent of ice cover due to climate change will alter time and energy budgets, with potentially negative effects on fish production.

Using Movements and Habitat Utilization as a Functional Metric of Restoration for Estuarine Juvenile Fish Habitat

AbstractResource managers use habitat restoration to offset estuarine habitat loss; however, there is limited information about how functionally successful restorations have been, particularly with respect to their use by mobile marine predators. Restoration monitoring efforts typically use point‐of‐capture metrics to assess fish community recovery and habitat use, but this provides little insight into how fish habitat use changes through time. Using translocation experiments, we integrated the movements of California Halibut Paralichthys californicus, a conservation target species, into a point‐of‐capture monitoring program in a restored tidal creek estuary. Large halibut (>25 cm) were captured more frequently in the main stream channel, while small ones (<25 cm) were typically caught in the innermost marsh creeks. We actively tracked these fish (n = 20; size range = 26.6–60.5 cm TL) acoustically to identify their preferred habitats and challenged these habitat associations by means of translocations to a different habitats. Large fish tended to have small localized convex hull activity spaces, remaining in areas with high water flow and sandy substratum near eelgrass Zostera marina beds. Individuals that were translocated to marshes returned to the channel and exhibited movements over long distances from their initial locations to their last tracked positions; however, fish that were translocated from marshes to the channel remained in channel habitat and moved smaller distances between their first and last tracked points. Large halibut likely selected the channel because higher water flow would lead to higher concentrations of prey. Small halibut used marshes more frequently, likely because marshes have temperatures thought to maximize growth rates. Our study can serve as a proof of concept that linking point‐of‐capture and tracking data provides valuable information for habitat restoration, including the fact that California Halibut utilize estuaries in a size‐segregated manner based on environmental conditions. This suggests that tidal creek estuaries with a variety of channel types and morphologies—like our study site—are well‐suited to support this species.Received August 18, 2015; accepted March 1, 2016

Seasonal Variation in Habitat Use of Juvenile Steelhead in a Tributary of Lake Ontario

Abstract We examined seasonal-habitat use by subyearling and yearling Oncorhynchus mykiss (Rainbow Trout or Steelhead) in Trout Brook, a tributary of the Salmon River, NY. We determined daytime fish-habitat use and available habitat during August and October of the same year and observed differences in habitat selection among year classes. Water depth and cover played the greatest role in Steelhead habitat use. During summer and autumn, we found yearling Steelhead in areas with deeper water and more cover than where we observed subyearling Steelhead. Both year classes sought out areas with abundant cover during both seasons; this habitat was limited within the stream reach. Subyearling Steelhead were associated with more cover during autumn, even though available cover within the stream reach was greater during summer. Principal component analysis showed that variation in seasonal-habitat use was most pronounced for subyearling Steelhead and that yearling Steelhead were more selective in their habitat use...

Otolith chemistry discriminates water mass occupancy of Arctic fish in the Chukchi Sea

The microchemistry of otoliths has the potential to reconstruct fish movement patterns and habitat use between environmentally different habitats for individual age classes of Arctic marine fish. Herein, we tested the relationship between the bottom water mass from which a fish was collected and the microchemistry of the most recent growth edge of the fish’s otolith using Mg, Sr, Ba and Ca, and then determined the physical and biological factors that affected the chemical signatures. A discriminant function post hoc analysis of fish occupying bottom water masses resulted in 76% correct classification of Arctic or Polar cod (Boreogadus saida) and 82% correct classification of Arctic staghorn sculpin (Gymnocanthus tricuspis) into bottom water masses of capture when ages were pooled. By separating age classes, correct classifications into water masses of capture were as high as 87% for Arctic cod (three water masses) and 90% for Arctic staghorn sculpin (two water masses). Otolith Ba:Ca, Mg:Ca and Sr:Ca ratios were most consistently affected by bottom water temperature; the latter two were also affected by fish age and fish length. The use of otolith microchemistry to determine occupancy of water masses over time is most promising for Arctic cod, which is widespread and occupies the most thermally diverse habitats in Arctic waters.

Patterns of Fish Assemblage Structure and Habitat Use among Main‐ and Side‐Channel Environments in the Lower Kootenai River, Idaho

AbstractThe lower Kootenai River, Idaho, was sampled during the summers of 2012 and 2013 to evaluate its fish assemblage structure at seven sites within main‐ and side‐channel habitats where large‐scale habitat rehabilitation was undertaken. Understanding the current patterns of fish assemblage structure and their relationships with habitat is important for evaluating the effects of past and future rehabilitation projects on the river. Species‐specific habitat associations were modeled, and the variables that best explained the occurrence and relative abundance of fish were identified in order to guide future habitat rehabilitation so that it benefits native species. The results indicated that the side‐channel habitats supported higher species richness than the main‐channel habitats and that nonnative fishes were closely associated with newly rehabilitated habitats. This research provides valuable insight on the current fish assemblages in the Kootenai River and the assemblage‐level responses that may occur as a result of future rehabilitation activities.

Changes in depth occupied by Great Lakes lake whitefish populations and the influence of survey design

Understanding fish habitat use is important in determining conditions that ultimately affect fish energetics, growth and reproduction. Great Lakes lake whitefish (Coregonus clupeaformis) have demonstrated dramatic changes in growth and life history traits since the appearance of dreissenid mussels in the Great Lakes, but the role of habitat occupancy in driving these changes is poorly understood. To better understand temporal changes in lake whitefish depth of capture (Dw), we compiled a database of fishery-independent surveys representing multiple populations across all five Laurentian Great Lakes. By demonstrating the importance of survey design in estimating Dw, we describe a novel method for detecting survey-based bias in Dw and removing potentially biased data. Using unbiased Dw estimates, we show clear differences in the pattern and timing of changes in lake whitefish Dw between our reference sites (Lake Superior) and those that have experienced significant benthic food web changes (lakes Michigan, Huron, Erie and Ontario). Lake whitefish Dw in Lake Superior tended to gradually shift to shallower waters, but changed rapidly in other locations coincident with dreissenid establishment and declines in Diporeia densities. Almost all lake whitefish populations that were exposed to dreissenids demonstrated deeper Dw following benthic food web change, though a subset of these populations subsequently shifted to more shallow depths. In some cases in lakes Huron and Ontario, shifts towards more shallow Dw are occurring well after documented Diporeia collapse, suggesting the role of other drivers such as habitat availability or reliance on alternative prey sources.

Demersal fish distribution and habitat use within and near Baltimore and Norfolk Canyons, U.S. middle Atlantic slope

Numerous submarine canyons along the United States middle Atlantic continental margin support enhanced productivity, diverse and unique habitats, active fisheries, and are vulnerable to various anthropogenic disturbances. During two cruises (15 Aug–2 Oct 2012 and 30 Apr–27 May 2013), Baltimore and Norfolk canyons and nearby areas (including two cold seeps) were intensively surveyed to determine demersal fish distributions and habitat associations. Overall, 34 ROV dives (234–1612m) resulted in 295h of bottom video observations and numerous collections. These data were supplemented by 40, 30-min bottom trawl samples. Fish observations were assigned to five general habitat designations: 1) sand-mud (flat), 2) sloping sand-mud with burrows, 3) low profile gravel, rock, boulder, 4) high profile, canyon walls, rocks or ridges, and 5) seep-mixed hard and soft substrata, the later subdivided into seven habitats based on amounts of dead mussel and rock cover. The influence of corals, sponges and live mussels (seeps only) on fish distributions was also investigated. Both canyon areas supported abundant and diverse fish communities and exhibited a wide range of habitats, including extensive areas of deep-sea corals and sponges and two nearby methane seeps (380–430m, 1455–1610m). All methods combined yielded a total of 123 species of fishes, 12 of which are either new records for this region or have new range data. Depth was a major factor that separated the fish faunas into two zones with a boundary around 1400m. Fishes defining the deeper zone included Lycodes sp., Dicrolene introniger, Gaidropsaurus ensis, Hydrolagus affinis, Antimora rostrata, and Aldrovandia sp. Fishes in the deep zone did not exhibit strong habitat affinities, despite the presence of a quite rugged, extensive methane seep. We propose that habitat specificity decreases with increasing depth. Fishes in the shallower zone, characterized by Laemonema sp., Phycis chesteri, Nezumia bairdii, Brosme brosme, and Helicolenus dactylopterus, exhibited a variety of habitat use patterns. In general, fish assemblages in the soft substrata areas (dominated by P. chesteri, N. bairdii, Glyptocephalus cynoglossus, Lophius americanus, Merluccius albidus) were different from those in more complex habitats (dominated by Laemonema spp., Hoplostethus spp., B. brosme, Benthocometes robustus, L. americanus, Dysommina rugosa). Although, when present, the dense coral and sponge cover did not statistically affect general fish assemblage patterns in hard bottom habitats, these sessile organisms markedly increased habitat complexity, and some fish species exhibited close association with them. Fish species compositions in the two canyons were not substantially different from the surrounding slopes. However, the diversity of habitats within both the canyons and seeps exerted an important influence on assemblage structure. At least for some species (e.g., B. brosme) canyon and seep environments may be a refuge from intensive bottom fishing activities. We frequently observed evidence of commercial and recreational fishing activity (lost gear on bottom and fishing boats in the area) throughout the canyons and some resulting habitat damage. Conservation measures for the unique and more vulnerable areas (seep and coral habitats) have recently been approved.

Tides, Salinity, and Biogeography Affect Fish Assemblage Structure and Function in Macrotidal Mangroves of the Neotropics

Identifying the drivers that explain the distribution of tropical coastal fishes remains a central goal in biogeography. However, a lack of comparisons with standardized data still prevents more robust generalizations. Here, we assess if general assembly rules apply in two intertidal mangrove fish assemblages from different biogeographical regions (Tropical Eastern Pacific and Western Atlantic). Using multivariate analyses on field data collected for about 1 year at each location, we examined if different community attributes (species richness, taxonomic, and trophic composition, density, and catch mass) varied temporally (according to tidal–diel rhythms) and spatially (salinity gradients and between biogeographical regions). Similar total fish species richness (ca. 50 species) mirrored the regional species richness of coastal fishes in these regions. Pufferfishes (Tetraodontidae) and catfishes (Ariidae) dominated (in catch mass) fish assemblages in both regions. Closely related species within these families responded in similar ways to tidal–diel changes suggesting the existence of a phylogenetic signal in temporal niche use. The strength of the influence of tidal–diel forces determining fish habitat use were likely related to differences in mangrove topography. The biogeography of the adjacent freshwater fish fauna could explain differences in taxonomic and trophic composition between regions. Our results highlight the role that tidal–diel dynamics play in influencing the structure of fish assemblages in macrotidal areas, and suggest that considering the regional biogeographical history and the local seascape configurations could help to explain differences in mangrove fish assemblage structure across regions.

Fish communities across a spectrum of habitats in the western Beaufort Sea and Chukchi Sea

The increased scientific interest in the Arctic due to climate change and potential oil and gas development has resulted in numerous surveys of Arctic marine fish communities since the mid-2000s. Surveys have been conducted in nearly all Arctic marine fish habitats: from lagoons, beaches and across the continental shelf and slope. This provides an opportunity only recently available to study Arctic fish communities across a spectrum of habitats. We examined fish survey data from lagoon, beach, nearshore benthic, shelf pelagic and shelf benthic habitats in the western Beaufort Sea and Chukchi Sea. Specifically, we compare and contrast relative fish abundance and length (a proxy for age) among habitats and seas. We also examined ichthyoplankton presence/absence and abundance of dominant taxa in the shelf habitat. Our synthesis revealed more similarities than differences between the two seas. For example, our results show that the nearshore habitat is utilized by forage fish across age classes, and is also a nursery area for other species. Our results also indicated that some species may be expanding their range to the north, for example, Chinook Salmon. In addition, we documented the presence of commercially important taxa such as Walleye Pollock and flatfishes (Pleuronectidae). Our synthesis of information on relative abundance and age allowed us to propose detailed conceptual models for the life history distribution of key gadids in Arctic food webs: Arctic and Saffron Cod. Finally, we identify research gaps, such as the need for surveys of the surface waters of the Beaufort Sea, surveys of the lagoons of the Chukchi Sea, and winter season surveys in all areas. We recommend field studies on fish life history that sample multiple age classes in multiple habitats throughout the year to confirm, resolve and interpret the patterns in fish habitat use that we observed.

Variation in fatty acid composition of the bigeye snapper Lutjanus lutjanus collected in coral reef habitats of the Malaysian South China Sea.

BackgroundIn order to understand trophic ecology, habitat use and migration of coral reef fish, fatty acid composition and levels were examined in the bigeye snapper Lutjanus lutjanus collected in the Malaysian South China Sea.ResultsProportions of saturated fatty acids (SAFA) ranged from 55.0% to 66.5%, with the highest proportions in fatty acids, the second highest was monounsaturated fatty acids (MUFA) ranged from 30.7% to 40.2% while the proportion of polyunsaturated fatty acids (PUFA) was the lowest ranged from 2.8% to 4.8%. Palmitic acid (16:0) was the most common in SAFA, oleic acid (C18:1ω9c) was the dominant in MUFA and linolenic acid (C18:3n3) showed the highest value in PUFA. Fatty acid concentrations, especially in SAFA and MUFA, increased with fish growth, suggesting diet and habitat shifts during the fish life history. Most of the fish had more than 1 of EPA: DHA ratio, which suggested that diets of L. lutjanus tended to be higher trophic organisms such as zooplankton and crustacean in coral ecosystem.ConclusionsThe diet shift revealed by the composition and levels of the fatty acid profile revealed potential pattern in the habitat use and migration scale in coral reef environment of L. lutjanus.

Ecoregional, catchment, and reach-scale environmental factors shape functional-trait structure of stream fish assemblages

Patterns of association between functional traits and environmental gradients can improve understanding of species assemblage structure from local to regional scales, and therefore may be useful for natural resource management. We measured functional traits related to trophic ecology, habitat use, and life-history strategies of fishes and examined their associations with environmental factors in the Brazos and Trinity River basins in Central Texas. We also examined the relationship between functional diversity of fish assemblages and indices of biotic integrity and habitat quality. Environmental characteristics at the local reach and catchment scales, including the extent of forested area in the watershed, amount of land developed for urban and agricultural uses, stream size, substrate characteristics, and availability of riffle and pool habitats, were significantly associated with functional trait composition of fish assemblages. Broad physiographic differences between ecoregions also had a large influence on taxonomic and functional assemblage structure. In general, the volume of functional trait space occupied by fish assemblages was greatest in streams with high habitat quality scores located within landscapes having less alteration from agriculture and urban development. Distributions of functional traits in fish assemblages might provide an additional basis for assessment of stream condition in relation to environmental impacts.