Fish Habitat Use Research Articles

Environmental habitat use and migration of Plecoglossidae and Osmeridae fish

The life histories of Plecoglossidae and Osmeridae fish collected from Japanese fresh, brackish, and seawaters were studied by examining the strontium (Sr) to calcium (Ca) ratios in their otoliths. The Sr:Ca ratios in the otoliths changed with the salinity of the habitat. The fish living in a freshwater environment showed consistently low Sr:Ca ratios throughout the otolith. The fish were identified as a standard freshwater type. In contrast, fish collected from the intertidal zone showed higher otolith Sr:Ca ratios than those in the standard freshwater type, and the ratios fluctuated along the growth phase. In the present study, in addition to the representative migration pattern reported previously, other migration patterns were found to show consistently high Sr:Ca ratios throughout the otolith in several Osmeridae fish. Those results indicate that these fish have a flexible migration strategy with a high degree of behavioural plasticity and an ability to utilize the full range of salinity throughout their life history.

Reproduction and spawning habitat of white trevally, <em>Pseudocaranx dentex</em>, in the Azores, central north Atlantic

Reproductive biology and habitat preferences of the white trevally, Pseudocaranx dentex (Carangidae), were studied in the Azores islands, central north Atlantic, to determine the spatial and seasonal dynamics of habitat use of immature and mature fish. The sex ratio was close to 1:1 and fish matured at about 30 cm fork length. There were no differences in the maturation or length-weight relationships between sexes. The spawning season lasts from June to September. Underwater visual censuses showed that schools of mature individuals preferentially aggregate around the summits of offshore reefs during the spawning season. In contrast, schools of smaller, immature fish use inshore habitats all year round. Our data support the hypothesis that offshore reefs are a preferential spawning habitat of larger white trevally, and most possibly for a number of visitor pelagic predators as well. Inverse relationships between exploitation levels, abundance and size composition at the two different islands suggest that the summer fishery targeting trevally schools around offshore reefs has negatively impacted the population. These findings bring additional ecological and management relevance to offshore reefs.

Seasonal Habitat Use of Brook Trout and Juvenile Atlantic Salmon in a Tributary of Lake Ontario

The seasonal habitat use of Salvelinus fontinalis (Brook Trout) and sub-yearling Salmo salar (Atlantic Salmon) was examined in Hart Brook, a tributary of Lake Ontario. Fish habitat use and available habitat were examined during summer and autumn. Interspecific differences in habitat use occurred as well as intraspecific seasonal differences. Overyearling Brook Trout were more selective in their habitat preferences than subyearling Brook Trout or juvenile Atlantic Salmon. Depth and the amount of cover were significantly different among the three fish groups. Salmon occupied faster and shallower water than either age group of trout. Atlantic Salmon were also associated with larger-sized substrate materials than either trout age group, and salmon occurred in habitats with less cover than trout. Overyearling Brook Trout occupied deeper water with more cover than subyearling trout. All three salmonid groups occupied areas with more cover in autumn compared to summer. In autumn, subyearling Brook Trout used deeper areas than they had in the summer. In Hart Brook, the habitat of subyearling Atlantic Salmon can be generally characterized as riffles, the habitat of overyearling Brook Trout was deep pools with extensive cover (35%), and that of subyearling trout was any area with moderate flow and at least 20% cover. As efforts proceed to reintroduce Atlantic Salmon in Lake Ontario, further research is needed to ensure the conservation of Brook Trout populations.

Habitat utilization by coral reef fish: implications for specialists vs. generalists in a changing environment

1. The impact of environmental disturbance and habitat loss on associated species is expected to be dependent on a species' level of specialization. We examined habitat use and specialization of coral reef fish from the diverse and ecologically important family Pomacentridae, and determined which species are susceptible to declines in coral cover due to disturbance induced by crown-of-thorns seastar (COTS, Acanthaster planci L.). 2. A high proportion of pomacentrid species live in association with live coral as adults (40%) or juveniles (53%). Adults of many species had strong affiliations with branching corals, while juveniles favoured plating growth forms, reflecting the sizes of refuge provided by coral types. 3. Juveniles of species that associated with coral had narrower niche breadths than adult conspecifics, due to associations with specific coral types. The especially high coral association and narrower niche breadth of juveniles suggest that the presence of live coral is crucial for many species during early life history, and that disturbance-induced coral loss may have serious flow-on effects on adult abundance. 4. Microhabitat availability was a poor predictor of fish species abundance. Significant correlations between coverage of coral types and abundance of five adults and two juvenile species were detected; however, these relationships explained <35% and <10% of the variation in abundance of adult and juvenile species, respectively. 5. Niche breadth explained 74% of the variation in species' mean response to coral decline and it is clear that disturbance has a greater impact on resource specialists, suggesting that increasing frequency and intensity of coral loss will cause reef fish communities to become dominated by habitat generalists at the expense of coral-dwelling specialists.

Life in the ice lane: the winter ecology of stream salmonids

AbstractDespite the common view that conditions in winter strongly influence survival and population size of fish, the ecology of salmonids has not been as extensively studied in winter as in other seasons. In this paper, we review the latest studies on salmonid winter survival, habitat use, movement and biotic interactions as they relate to the prevailing physical and habitat conditions in rivers and streams. The majority of research conducted on the winter ecology of salmonids has been carried out in small rivers and streams, where temperatures are above zero and where there is no ice. Investigations in large rivers, regulated and dredged rivers, and under conditions of different ice formations are almost totally lacking, presumably related to sampling difficulties with these systems. The studies‐at‐hand indicate that a multitude of physical and biological factors affect the survival, behavior, and habitat use of salmonids in winter. The general concept that winter functions as a critical period for the survival of young salmonids is not well supported by the literature. Instead, overwinter survival of juvenile fish appears to be context‐dependent, related to specific habitat characteristics and ice regimes of streams. In general, over wintering salmonids prefer sheltered, low velocity microhabitats, are mainly nocturnal, and interact relatively little with conspecifics or interspecifics. Specific descriptions of microhabitat preferences of salmonids are difficult to make due to highly disparate results from the literature. We suggest that future research should be directed towards (1) being able to predict the dynamics of freezing and ice processes at different scales, especially at the local scale, (2) studying fish behavior, habitat use and preference under partial and full ice cover, (3) evaluating the impacts of man‐induced environmental modifications (e. g. flow regulation, land‐use activities) on the ecology of salmonids in winter, and (4) identifying methods to model and assess winter habitat conditions for salmonids. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Linkages Between Salt Marshes and Other Nekton Habitats in Delaware Bay, USA

Although the importance of salt marsh habitats for fishes and crabs has been accepted for nearly a half century, the linkages between marshes and adjacent estuarine habitats have been ill-defined. In this synoptic study (n > 19,000 samples, 14 species, 10 million individuals), we provide fresh insights into the patterns of fish and blue crab habitat use for the Delaware Bay and River (upstream to tidal fresh water) over 211 km of aquatic habitats. Our examination was based on 7 years (1998–2004) of sampling (with multiple gears) across 12 habitat types along the entire salinity gradient. While this study reinforces the importance of salt marsh creeks as fish and blue crab habitat, it also makes clear that there are few marsh-dependent species because almost all species simultaneously use a variety of other bay and river habitats. The pattern of use varies over seasons and with ontogeny. This facultative use of marshes, due in large part to the extensive migrations for many of the species, makes an improved focus on the linkages across this ecoscape critical to understanding the functional significance of marshes (and estuaries) to fishes and crabs and their continental shelf metapopulations.

Evaluating day–night changes in shallow Mediterranean rocky reef fish assemblages by visual census

Ecological information on coastal fish distribution patterns and habitat use can be greatly improved by nocturnal samplings and observations. To this purpose, the structure of a Mediterranean fish assemblage inhabiting the shallow rocky littoral of Linosa Island (Sicily Strait, Italy) was examined by using visual census to detect possible diel variations in species composition and abundance. Day–night fish distribution patterns were investigated by multivariate and univariate analyses. Overall, 42 fish taxa belonging to 19 families were recorded: 35 during the day and 24 during the night. Seventeen species were common to both diurnal and nocturnal assemblages. Within the diurnal assemblage, Chromis chromis was the most represented species (37.2%), followed by Thalassoma pavo (23.2%) and Sparisoma cretense (10.8%). Within the nocturnal assemblage, the most abundant taxon was Atherina spp. (33.9%), followed by Apogon imberbis (26.4%) and Boops boops (11.5%). Our results indicated wide variation in the abundance and species composition during the day and during the night. Multi Dimensional Scaling plot showed a clear-cut separation between the two assemblages and analysis of similarities found significant differences as well. SIMPER analysis revealed that ten species individually contributed by more than 2.5% to the dissimilarity between diurnal and nocturnal assemblages, T. pavo, C. chromis and S. cretense being the first three species in order of decreasing percentage. ANOVA performed on species richness and fish abundance detected significant differences between diurnal and nocturnal assemblages, the latter showing far lower average values for both variables.

Quantitative assessment of the area of shallow habitat for fish on the Swedish west coast

Abstract Stål, J., and Pihl, L. 2007. Quantitative assessment of the area of shallow habitat for fish on the Swedish west coast. – ICES Journal of Marine Science, 64: 446–452. Much effort has been focused recently on juvenile and adult fish habitat use in shallow coastal areas. However, to understand fully the importance of such habitats for fish production it is necessary also to quantify the area of existing habitat types. We inventory and quantify the area of major habitat types in a 1000 km2 area of the Swedish west coast, on a scale appropriate for coastal-zone management. An echosounder and GPS-transmitter mounted on a small boat were used to estimate the distribution of habitat along transects in seven regions of differing coastal morphology. The signal from the echosounder separated major habitat types, and recordings were verified by video documentation and visually. The information was used with GIS-software to estimate the quantitative extent of bottom habitats at depth ranges of 0–3, 3–6, and 6–10 m. Of the major habitat types, soft substrata dominated all except one region, and increased in size with depth in all regions. There were rocky substrata in all regions, but as steep rock walls in the north and more gently sloping substrata with pebbles and boulders in the south. Approximately half the rocky habitat was in the shallowest depth range. Seagrass meadows on soft substrata were mainly in the shallow protected archipelago of the central coast.

Impact of environmental factors on fish distribution assessed in rangeland streams

We sampled fish in pools located on tributaries of Cow Creek in the northern Sacramento Valley, and related fish distribution and habitat use to environmental factors across the 2003 agricultural growing season. This rangeland watershed experiences extensive livestock use, and many landowners divert stream water for pasture irrigation. Our goal was to provide landowners and managers with current baseline information about the conditions in which fish were found. Our results provide a basis for the development and comparison of irrigation best management practices that may improve conditions for native fish in rangeland streams.

A Decade of Research on the Environmental Impacts of Pulp and Paper Mill Effluents in Canada: Field Studies and Mechanistic Research

Studies conducted in Sweden in the early 1980s provided some of the first evidence that effluents from some pulp mills were capable of inducing toxic responses in fish at very low concentrations in the receiving environment. In response to these findings, studies were initated in Canada and impacts of primary treated bleached kraft mill effluent on reproductive function in fish were found. Reproductive impacts in fish were not limited to mills that used chlorine in the bleaching process and were also evident at some mills that employed secondary effluent treatment. In 1992, new federal regulations were passed under the Canadian Environmental Protection Act to control releases of dioxins and furans, and a new Pulp and Paper Effluent Regulation under the Fisheries Act set stricter limits for biological oxygen demand and total suspended solids. Very importantly, the new regulations included requirements for environmental effects monitoring (EEM) at all mill sites. This allowed the effectiveness of the control limits in protecting fish, fish habitat, and human use of fisheries resources to be assessed. At the same time, the Minister of the Environment launched an intensive government, industry, and university research program. Results from this research program along with feedback from the EEM program would then be used to define what additional control actions might be necessary. This article reviews the field studies and mechanistic research conducted in Canada following the implementation of the new federal regulations. Great progress has been made in this area, first demonstrating reproductive effects at various locations, then determining the mechanisms responsible for the reproductive effects at specific sites, followed by the demonstration of partial recovery in reproductive function following process and treatment changes in response to the new regulations. However, it is clear from the results of the first two cycles of the EEM program that mill effluents still affect the local receiving environments at a number of locations across Canada, and that continued research combining field studies, bioassay application, and chemical identification is required. Completion of this assessment would not have been possible without the helpful comments and scientific reviews provided by Drs. John Carey, Jim Maguire, Kelly Munkittrick, Glen Van Der Kraak, Jim Sherry, and Olöf Sandstrom.

Marine nurseries and effective juvenile habitats: concepts and applications

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 312:291-295 (2006) - doi:10.3354/meps312291 Marine nurseries and effective juvenile habitats: concepts and applications Craig P. Dahlgren1,*, G. Todd Kellison2,10, Aaron J. Adams3, Bronwyn M. Gillanders4, Matthew S. Kendall5, Craig A. Layman6, Janet A. Ley7, Ivan Nagelkerken8, Joseph E. Serafy9 1Perry Institute for Marine Science, 100 N. US Highway 1, Suite 202, Jupiter, Florida 33477, USA 2Biscayne National Park, 9700 SW 328th Street, Homestead, Florida 33033, USA 3Mote Marine Lab, Charlotte Harbor Field Station, PO Box 2197, Pineland, Florida 33945, USA 4Southern Seas Ecology Laboratories, Darling Building, School of Earth and Environmental Sciences, University of Adelaide, South Australia 5005, Australia 5NOAA Biogeography Team, 1305 East West Highway, Silver Spring, Maryland 20910, USA 6Department of Ecology and Evolutionary Biology, Yale University; PO Box 208106, New Haven, Connecticut 06520-8106, USA 7Australian Maritime College, PO Box 21, Beauty Point, Tasmania 7270, Australia 8Department of Animal Ecology and Ecophysiology, Institute for Water and Wetland Research, Radboud University Nijmegen, Toernooiveld 1, 6525 ED, Nijmegen, The Netherlands 9National Marine Fisheries Service, Southeast Fisheries Science Center, 75 Virginia Beach Drive, Miami, Florida 33149, USA 10Present address: National Marine Fischeries Service, Southeast Fisheries Science Center, 75 Virginia Beach Drive, Miami, Florida 33149, USA *Email: cdahlgren@perryinstitute.org ABSTRACT: Much recent attention has been focused on juvenile fish and invertebrate habitat use, particularly defining and identifying marine nurseries. The most significant advancement in this area has been the development of a standardized framework for assessing the relative importance of juvenile habitats and classifying the most productive as nurseries. Within this framework, a marine nursery is defined as a juvenile habitat for a particular species that contributes a greater than average number of individuals to the adult population on a per-unit-area basis, as compared to other habitats used by juveniles. While the nursery definition and framework provides a powerful approach to identifying habitats for conservation and restoration efforts, it can omit habitats that have a small per-unit-area contribution to adult populations, but may be essential for sustaining adult populations. Here we build on the nursery concept by developing a framework for evaluating juvenile habitats based on their overall contribution to adult populations, and introduce the concept of Effective Juvenile Habitat (EJH) to refer to habitats that make a greater than average overall contribution to adult populations. KEY WORDS: Habitat · Juvenile · Nursery · Nearshore Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 312. Online publication date: April 24, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Habitat and resource use by larval and juvenile fishes in an arid‐land river (Rio Grande, New Mexico)

Summary1. Studies of mesic temperate and tropical rivers suggest an important role for floodplain habitats as nursery areas for larval and juvenile fishes. In arid‐land rivers the extent and duration of flooding is diminished and habitats and resources used by larval fishes are poorly known. Our study documented habitat and resource use of larval fishes in the Rio Grande, New Mexico, an arid‐land river.2. Spatial and temporal distribution of larval and juvenile fishes and their inferred microhabitat preferences were studied during spring, summer and autumn, 2003. Stable carbon (13C : 12C) and nitrogen (15N : 14N) isotope ratios were measured to identify nutrient sources and characterise trophic positions of young‐of‐year fishes in this system.3. Some fishes recruited during high flows (in spring), whereas others recruited during low‐flow periods in late summer. Regardless of the timing of reproduction, microhabitats with lower current velocity and higher temperature appeared to serve as vital nursery grounds for Rio Grande fishes. Ephemeral backwaters and disconnected side channels held the highest abundance and diversity of larvae and juveniles.4. Stable isotope analyses revealed that fish larvae obtained carbon predominately from algal production in early summer, but used organic carbon derived from emergent macrophytes as river discharge decreased in mid‐summer. This shift may have been facilitated by microinvertebrate prey that grazed down edible algae and then switched to macrophytes in mid‐summer. Nitrogen isotope ratios did not differ among species or early life stages, suggesting that larval and juvenile fishes use similar food resources, especially when restricted to isolated pools in summer.

Development and experimental assessment of an underwater video technique for assessing fish-habitat relationships

Developing tools that aquatic managers can use to understand the impact of human development on fish habitat is important in an era where our aquatic resources are under increasing pressure. To this end, we examined whether an underwater video camera was useful for quantifying fish habitat use in inland lakes by 1) examining patterns in fish habitat use, residency time and feeding behaviour among habitat types, 2) determining the precision and statistical power of the aforementioned estimates, and 3) assessing whether our habitat-specific camera estimates were reflective of whole-system estimates. Lastly, we used our protocol in an experimental situation to test site-specific fish habitat use at sites where habitats were manipulated (removed or added). We demonstrated that our underwater video protocol could successfully capture site-level habitat use that corresponded with whole-system abundance estimates, addressing the concern that habitat-based surrogates of fish productivity be validated on a whole-system scale. Unfortunately, our underwater video technique was unable to discriminate fish habitat use patterns among simple habitat types and unable to consistently separate differences in among-habitat fish feeding and residency behaviours. Our ability to detect a difference was low in all among-habitat comparisons. In the aquatic systems where habitat was added, we documented a significant shift in fish habitat use towards the addition sites and away from control sites, but no corresponding increase in system-wide fish biomass or production; no changes were apparent in the habitat removal lakes. A combination of longer filming duration, more filming sites or changing to a mobile transect method would likely address the data deficiencies that limited our ability to make site-level inferences about fish habitat use.

하천의 어류 서식환경을 고려한 생태학적 추천유량 산정

금번 연구는 낙동강 유역의 영강, 위천, 회천, 거창위천, 청도천, 단장천에서 산란기와 성어기에 어류의 서식과 수심, 유속, 하상재료 등 수리학적 특성에 관한 자연과학과 공학의 학제간 상호 연계조사를 시행하였으며, 어종별(피라미와 갈겨니), 성장단계별(산란기와 성어기), 서식처조건별(수심, 유속과 하상재료) 어류 서식 적합도 기준을 작성하였다. 유지유량 증분법 개념의 물리적 서식처 모의시스템을 적용하여, 낙동강 유역의 주요 하천에서 어류서식에 적합한 유량을 산정하고, 그 중 가장 큰 유량값을 생태학적 추천유량으로 결정하였다. 금번 결정한 생태학적 추천유량은 내성천 <TEX>$6.5\;m^3/s$</TEX> 등 <TEX>$5.0\;m^3/s{\sim}10.0\;m^3/s$</TEX> 이었다. 또한 생태학적 추천유량과 기존에 산정된 생태계 필요유량 및 유황분석 결과를 비교<TEX>${\cdot}$</TEX>검토 하였다. The detailed interdisciplinary surveys were conducted on the pattern of habitat use of dominant fishes during the spawning and adult stage. The hydraulic parameters of the depth and velocity, discharge, substrate cover streams, and distribution of fish in the Yeonggang, WiCheon, HoeCheon, GeochangwiCheon, CheongdoCheon, DanjangCheon (the Nakdong River Basin) were measured. The Habitat Suitability Criteria was developed for the two fish species (Zacco Platypus and Zacco Temmincki) and life stages(spawning and adult), habitat conditions (depth, velocity and covet). The Physical Habitat Simulation of the Instream Flow Incremental Methodology was applied to calculate for optimal flow and the ecological flow recommendation was proposed by choosing the largest one in the optimal flow. The ecological flow recommendation was <TEX>$5.0\;m^3/s{\sim}10.0\;m^3/s$</TEX> (e.g., <TEX>$6.5\;m^3/s$</TEX> in the NaeseongCheon). Also, the ecological flow recommendations were compared with the existing ecological flow and flow duration analysis.

Accuracy of Aerial Telemetry in Fisheries Studies

AbstractRadiotelemetry has become an important method for examining movement patterns of fishes. The use of aircraft allows transmitter‐implanted fish to be tracked over long distances and in areas difficult to access on the ground. However, the accuracy of aerially determined locations can limit the types of conclusions one can draw about fish habitat use. We utilized aerial telemetry while studying the effects of irrigation canals on a population of cutthroat trout Oncorhynchus clarkii. To determine the accuracy of aerially determined locations, we used a method common in terrestrial studies whereby transmitters are placed at known locations and then located by a naïve pilot. These aerially determined locations were then compared with the known locations of transmitters to determine the mean error associated with aerial telemetry. In our study, we found that aerially acquired location errors ranged from 22 to 426 m and had a mean of 178 m. In a review of recent studies that used aerial telemetry, we found that 15 of 34 (44%) terrestrial studies but only 4 of 17 (24%) aquatic studies reported an estimate of the error associated with aerial telemetry locations. The overall mean location error of these studies was 158 m. We urge aquatic biologists to consider location errors when using aerial telemetry, especially when making inferences about fish habitat use or movement patterns.

Effect of dietary fatty acids on the body tissues of larval and juvenile cobia and their prey

Polyunsaturated fatty acids (PUFAs) have been used as biomarkers in pelagic ecosystems although previous studies have failed to quantify the timing of conservation of dietary PUFAs in pelagic fishes and invertebrates. Here we investigated the influence of diet upon the timing of conservation of PUFAs throughout multiple trophic exchanges in larval and juvenile cobia ( Rachycentron canadum) and their prey. Cobia, rotifers ( Brachionus plicatilis), and Artemia ( A. franciscana) were fed laboratory processed or natural diets resembling prey and dietary modification of fatty acid signatures was quantified using two-source mixing models. Specimens were collected throughout the experiment to track dietary influences over time. Cobia larvae underwent significant dietary modification of PUFAs after 24 h and conserved > 90% of dietary PUFAs after an average of 6 days. Similar results were identified in juvenile cobia as significant dietary modification of PUFAs took place after 3 days and > 90% were conserved after an average of 12 days. In addition, no significant ontogenetic changes in PUFA signatures were identified in juvenile cobia throughout the 30-day experiment. PUFA signatures in prey items (rotifers and Artemia) underwent significant dietary modification in 24 h, with over 90% incorporation after 5–7 days. Results from this study support the premise that fatty acids are promising dietary indicators and may be useful for future studies examining trophic relationships in marine ecosystems and habitat use of marine fishes.

Diel activity and home range size in relation to food supply in a drift-feeding stream fish

Individuals within a species often compete for resources in both space and time. In dominance hierarchies individuals with the greatest competitive ability will occupy prime locations during optimal periods. We compared spatial and temporal use of habitat, aggression, and feeding success among giant kokopu (Galaxias argenteus) in dominance hierarchies under normal and reduced food supply. Under normal food supply conditions dominant fish were predominantly nocturnal and maintained large home ranges at night. Conversely, subdominant fish were diurnal and occupied large home ranges by day but were generally not observed at night. When the food supply was limited, the utilization of pools was determined by social rank. Dominant fish from each pool increased diurnal activity, home range size, aggressiveness, and the capture of food items offered by day while simultaneously reducing the spatial and temporal activity and habitat use of subdominant fish. These results indicate that behavioral changes in large dominant fish influence and reduce the amount of resources available to subdominant fish. Copyright 2005.

Two-dimensional modelling of habitat suitability as a function of discharge on two Colorado rivers

The quantity of water that should be retained in streams and rivers for the benefit of fish during periods of water scarcity is a question of considerable interest to river managers and biologists. Although instream flow methodologies have existed since the 1970s, no single method has been widely accepted for use on large warm-water rivers because of their high species richness and generalized fish habitat use patterns. In this paper, we present an approach similar to instream flow incremental methodology, but which uses two-dimensional flow models and biomass estimates derived from multiple sites on two Colorado rivers for predicting the effect of discharge on adult standing stocks of two native fish species. Suitability criteria are developed for bluehead and flannelmouth sucker (Catostomus discobolus and C. latipinnis) by comparing adult biomass in individual meso-habitat units with modelled depths and velocities. We find that roundtail chub (Gila robusta) biomass is not correlated with depth and velocity, but appears to be positively associated with indices of habitat heterogeneity. Species biomass and total usable habitat area are predicted as a function of discharge for each site and data show good correlation between predicted and measured biomass. Results suggest that the Colorado and Yampa Rivers have similar potential for native fish biomass, but low summer discharges limit native fish biomass on the Yampa River. Copyright © 2005 John Wiley & Sons, Ltd.

Fish Habitat Use Within and Across Wetland Classes in Coastal Wetlands of the Five Great Lakes: Development of a Fish-based Index of Biotic Integrity

The relative importance of Great Lake, ecoregion, wetland type, and plant zonation in structuring fish community composition was determined for 61 Great Lakes coastal wetlands sampled in 2002. These wetlands, from all five Great Lakes, spanned nine ecoregions and four wetland types (open lacustrine, protected lacustrine, barrier-beach, and drowned river mouth). Fish were sampled with fyke nets, and physical and chemical parameters were determined for inundated plant zones in each wetland. Land use/cover was calculated for 1- and 20-km buffers from digitized imagery. Fish community composition within and among wetlands was compared using correspondence analyses, detrended correspondence analyses, and non-metric multidimensional scaling. Within-site plant zonation was the single most important variable structuring fish communities regardless of lake, ecoregion, or wetland type. Fish community composition correlated with chemical/physical and land use/cover variables. Fish community composition shifted with nutrients and adjacent agriculture within vegetation zone. Fish community composition was ordinated from Scirpus, Eleocharis, and Zizania, to Nuphar/Nymphaea, and Pontederia/Sagittaria/Peltandra to Spargainium to Typha. Once the underlying driver in fish community composition was determined to be plant zonation, data were stratified by vegetation type and an IBI was developed for coastal wetlands of the entire Great Lakes basin.

Consistency of diel behaviour and interactions of stream fishes and invertebrates during summer

We examined the consistency of diel patterns observed in fish and aquatic invertebrates over three 24-h cycles within a 10-day period in summer (28–29 July, 4–5 and 7–8 August 1997) in the River Lee, Hertfordshire, England. We tested for temporal variations in epibenthos density and population size structure, age-specific fish density, microhabitat use and contagion as well as for correlations between fish length and prey number (in the gut) per millimetre fish standard length, a surrogate of foraging success, and fish density in point samples (an estimator of shoal size). Consistent patterns were observed in invertebrates and fish, though variability was greater in the former. Epibenthic invertebrates (except Chironomidae) demonstrated few or no diel differences in density, but some differences in size (based on head widths) were found in larvae of Chironomidae and Ephemeroptera (mainly Baetis rhodani (Pictet) and Ephemerella ignita Poda) between times of day. Fish density varied consistently and diel variations were observed in fish shoaling behaviour, habitat use, prey size and prey composition. Prey numbers in the gut generally decreased with increasing shoal size, but this was significant in Gobio gobio L. only. In some fish species/size classes, prey numbers correlated either positively or negatively with habitat variables, in particular with the distance fish were captured from the bank. Despite relatively low epibenthic densities, Chironomidae larvae were a prominent and preferred food item in the diet of all fish species, followed by Ephemeroptera in some (0 + Barbus barbus (L.), 0 + and 1 + Barbatula barbatula (L.), 1 + and ≥ 2 + Cottus gobio (L.)) and Simuliidae in others (0 + and ≥ 1 +G. gobio, 0 + Leuciscus cephalus (L.), 0 + and 1 + Phoxinus phoxinus (L.)), with Trichoptera larvae, Asellus sp., Ostracoda and Annelida as tertiary prey taxa. The relatively consistent diel patterns observed suggest that data from single 24-h cycles in late summer can be representative of daily patterns. Day-time only surveys of European riverine fishes may give unreliable estimates of mean fish population size and abundance. Copyright © 2005 John Wiley & Sons, Ltd.