Prey abundance, channel structure and the allometry of growth rate potential for juvenile trout

Abstract  The application of a drift-foraging bioenergetic model to evaluate the relative influence of prey abundance (invertebrate drift) and habitat (e.g. pool frequency) on habitat quality for young-of-the-year (YOY) and yearling juvenile cutthroat trout, Oncorhynchus clarki (Richardson) is described. Experiments and modelling indicated simultaneous limitation of fish growth by prey abundance and habitat, where depth and current velocity limit the volume of water and prey flowing through a fish's reactive field as well as swimming costs and prey capture success. Predicted energy intake and growth increase along a depth gradient, with slower deeper pool habitat generating higher predicted growth for both YOY and yearling trout. Bioenergetic modelling indicated that fish are constrained to use progressively deeper habitats to meet increasing energy requirements as they grow. Sensitivity of growth to prey abundance identified the need to better understand how variation in invertebrate drift and terrestrial drop affects habitat quality and capacity for drift-feeding fishes.     

Seasonal spatial distribution of juvenile lake sturgeon in Muskegon Lake,Michigan, USA

We examined seasonal spatial distribution and diel movements of juvenile lake sturgeon Acipenser fulvescens in Muskegon Lake, Michigan (a protected, drowned river mouth lake that links the Muskegon River to Lake Michigan). We surgically implanted ultrasonic tags in 20 juveniles (age 1–7) captured in gill nets to track their locations during August–December 2008/2009 and September 2010–October 2011. Most juveniles were observed ≤1.5 km from the mouth of the Muskegon River in Muskegon Lake at a mean depth of 7.5 m (SE = 1.3 m) during summer. In fall, juveniles moved away from the river mouth to the deepest part of Muskegon Lake and were observed at a mean depth of 15.8 m (SE = 1.3 m) during winter. The shift in spatial distribution coincided with fall turnover (i.e., loss of thermal stratification) and with changes in dissolved oxygen (DO) concentrations in the hypolimnion. During summer, DO concentrations in the hypolimnion were typically <4 mg·l^?1 in the deepest part of Muskegon Lake and DO concentrations at locations of tagged lake sturgeon were >7 mg·l^?1 in 94% of instances. Tracking in 2009 revealed no significant change in depth distribution or movement over the diel cycle. We only observed two tagged juveniles immigrating to Lake Michigan, suggesting that juveniles use Muskegon Lake for multiple years. Our results suggest that: (i) Muskegon Lake serves as an important nursery habitat for juvenile lake sturgeon that hatched in the Muskegon River before they enter Lake Michigan and (ii) seasonal changes in DO concentration in the hypolimnion likely affect the spatial distribution of juveniles in Muskegon Lake.     

Use of GIS to predict effects of water level on the spawning area for smelt, Retropinna retropinna, in Lake Taupo, New Zealand

A GIS model of the littoral bathymetry and substrate composition of Lake Taupo was created using ArcInfo. Littoral substrates were mapped by aerial photography and confirmed by ground-truthing. Water depths were determined by echosounding linked to a differential GPS. These data were imported into ArcInfo where a 3D GIS model was used to calculate the total area of smelt, Retropinna retropinna Richardson, spawning habitat (i.e. clean sand between depths of 0.5–2.5 m) at each of five lake levels. There was little change in area over the first 50 cm below the natural maximum lake level, but spawning habitat decreased rapidly over the next 1.4 m such that a 30% reduction occurred at the natural minimum level. Anecdotal information on inter-annual variations in lake level and smelt abundance supported the notion that high lake levels in spring result in high recruitment of smelt. The GIS model also predicted effects of lake level change on areas of macrophyte cover and on other littoral substrates, and could be used to assess effects of lake level changes on the habitats of other biota.     

Diel habitat selection of largemouth bass following woody structure installation in Table Rock Lake,Missouri

Largemouth bass Micropterus salmoides (Lacepède) use of installed habitat structure was evaluated in a large Midwestern USA reservoir to determine whether or not these structures were used in similar proportion to natural habitats. Seventy largemouth bass (>380 mm total length) were surgically implanted with radio transmitters and a subset was relocated monthly during day and night for one year. The top habitat selection models (based on Akaike's information criterion) suggest largemouth bass select 2–4 m depths during night and 4–7 m during day, whereas littoral structure selection was similar across diel periods. Largemouth bass selected boat docks at twice the rate of other structures. Installed woody structure was selected at similar rates to naturally occurring complex woody structure, whereas both were selected at a higher rate than simple woody structure. The results suggest the addition of woody structure may concentrate largemouth bass and mitigate the loss of woody habitat in a large reservoir.     

Microhabitat use, movements and abundance of gilt darters (Percina evides) in southern Appalachian (USA) streams

Abstract –  We examined microhabitat use by gilt darters ( Percina evides ) in two streams in the south-eastern USA. Darters were over-represented in erosional microhabitats with higher average velocities and more cobble. Male darters tended to show stronger selection than females. Size-based analyses showed that larger (≥60 mm) gilt darters tended to use microhabitats with more heterogeneous substrata and more boulder than smaller (≤59 mm) darters. We also conducted a short-term movement study and calculated population estimates based on mark–recapture data in autumn 2005. Darters moved both long and short distances with 40% of all recaptures occurring within 5 m of the initial capture point. Using Program mark and model-averaged parameter estimates gilt darter density was 0.31 darters·m⁻² (225 darters/730 m²). Conservation of this species will require the preservation of erosional habitats in streams.     

Linking temperate demersal fish species to habitat: scales,patterns and future directions

Adoption of the ecosystem approach to fisheries management relies on recognition of the link between fish and other components of the ecosystem, namely their physical and biological habitat. However, identifying the habitat requirements of marine fishes and hence determining their distribution in space and time is scientifically complex. We analysed the methodologies and findings of research on temperate, demersal fish habitat requirements to highlight the main developments in this field and to identify potential shortfalls. Many studies were undertaken over large spatial scales (≥100s km²) and these generally correlated abundances of fish to abiotic variables. Biological variables were accounted for less often. Small spatial scale (≤m²), experimental studies were comparatively sparse and commonly focused on biotic variables. Whilst the number of studies focusing on abiotic variables increased with increasing spatial scale, the proportion of studies finding significant relationships between habitat and fish distribution remained constant. This mismatch indicates there is no justification for the tendency to analyse abiotic habitat variables at large spatial scales. Innovative modelling techniques and habitat mapping technologies are developing rapidly, providing new insights at the larger spatial scales. However, there is a clear need for a reduction in study scale, or increase in resolution additional to the integration of biotic variables. We argue that development of sound predictive science in the field of demersal fish habitat determination is reliant on a change in focus along these lines. This is especially important if spatial management strategies, such as Marine Protected Areas (MPA) or No Take Zones (NTZ), are to be used in future ecosystem‐based approaches to fisheries management.     

Oceanographic features that define the habitat of Pacific ocean perch, Sebastes alutus

This study investigates the possibility that oceanographic features could have effects on the variations observed in the apparent abundance of a demersal rockfish, Pacific ocean perch, Sebastes alutus. Simultaneous monitoring of physical variables and indices of fish abundance was achieved by attaching oceanographic equipment to the fishing gear of commercial vessels and sampling the fish catch. It was found that perch prefer a temperature range from at least 4.8C to 6.7C and that their movement patterns are linked to the movement of these temperatures by coastal wind patterns. Perch prefer areas with steep bathymetry, characterized by turbulent activity due to interactions between the local bathymetry and tidal currents.     

Effects of instream structures on Kirikuchi charr, southernmost population of genus Salvelinus, in a small mountain stream of Japan

ABSTRACT:   The changes in physical habitats and responses of fish, e.g. the Kirikuchi charr Salvelinus leucomaenis japonicus , were examined by placing instream structures in a stream on the upper drainage of the Totsu River system of the Kii Peninsula, Japan, over a two-year period. Instream structures created pools below the structures, and these pools have maintained their functions as fish habitats over two years. In two treatment sections, sections A and B (some red-spotted masu salmon were removed in advance in section B), mean water depth increased soon after placing the structures, but decreased over two years. Mean water velocity slowed after placing the structures in both sections. Total fish abundance has been relatively high at the two treatment sections compared with a control section after placing the structures. Age 1 Kirikuchi charr, however, increased only in section B. These results indicate that instream structures can serve as habitat enhancement for fish, including Kirikuchi charr, in the study area if other appropriate habitat factors for respective species are taken into consideration.     

The role of flow dependency and water availability in fish assemblage homogenization in tributaries of the Chattahoochee River,Alabama, USA

The availability of water is becoming more variable as flow regime alterations intensify both locally and on a global scale. This pattern has been observed in the tributaries of the central Chattahoochee River System as water withdrawal and natural drought have caused flows to diminish. Stream discharge has steadily decreased in the study area by 31% over the last 50 years, and during this time, fish assemblage homogenization has occurred throughout the system. Our primary objective was to assess whether spawning mode and water availability are catalysts for fish assemblage change in tributaries of the Chattahoochee River System. We found that species which prefer or have adapted to low flow conditions (e.g. blacktail shiner Cyprinella venusta, redbreast sunfish Lepomis auritus and blackbanded darter Percina nigrofasciata) are becoming dominant and replacing historically dominant fluvial specialists. When examining short‐term changes between a dry year (2009) and a wet year (2010), some species preferring higher flows such as the highscale shiner Notropis hypsilepis were detected during the wet year, suggesting that the amount of water is important for the presence of these species in upstream reaches where they were historically abundant. Species that can reproduce successfully in low flow conditions are thriving and expanding their native ranges as more habitat becomes suitable. Species that require higher flows for part of their life cycle, however, appear to be declining from upstream areas as water availability continues to decrease, despite temporary recovery from downstream refugia during wet years.     

Comparison of spatial distribution models to predict subtidal burying habitat of the forage fish Ammodytes personatus in the Strait of Georgia,British Columbia,Canada

1. The Pacific sand lance (Ammodytes personatus) is a key forage species for many commercially important fish (e.g. salmon and groundfish), marine birds, and whales found in nearshore coastal waters of British Columbia, Canada.
2. Sand lance lack a swim bladder and have a requirement for low-silt, medium-coarse sandy sea-bed habitat for burying. Little information is available describing the distribution of burying habitat, partly because there are no commercial fisheries for A. personatus in British Columbia.
3. This information is required by habitat and wildlife managers to identify and protect uncommon patches of burying habitats from detrimental activities, including dredging, infilling, and oil spills.
4. In this study, habitat distribution results from five suitability modelling algorithms were evaluated: maximum entropy, generalized linear model, generalized additive model, random forest, and an ensemble model of the latter three.
5. The maximum entropy model had the highest performance score (area under the receiver operator characteristic curve was 0.78) and was selected as the model that most accurately identified the presence of suitable A. personatus burying habitat.
6. Model results indicate that suitable burying habitat is primarily influenced by derived sea-bed substrate, distance to estuary, distance to sand-gravel beaches, and bottom sea temperature.
7. Overall, the spatial modelling identified only 105 km² of highly suitable sand lance burying habitat, or 2.6% of the study area (0–150 m), primarily in Haro Strait, along the east coast of Vancouver Island, and in northern regions of the strait near Cortes, Savary, and Harwood islands.
8. Identification of this uncommon and patchy burying habitat will contribute to the ongoing conservation of an important coastal prey species.

     

Feeding ecology and habitat of the threespine stickleback, Gasterosteus aculeatus microcephalus, in a remnant population of northwestern Baja California, México

Abstract – The feeding ecology and habitat of the threespine stickleback ( Gasterosteus aculeatus microcephalus Girard, 1854) was studied from November 1996 to May 1997 in a remnant population of northwestern Baja California, México. The analysis of the stomach content of 179 individuals (25 to 56 mm standard length [SL]) showed a diet dominated by cyclopoid copepods (43.8%) and chironomid larvae (39.1%). Diet in relation to size and sex of the fish was dominated by copepods in autumn and winter and by chironomid larvae during spring. Diet overlap (Schoener's index) was significant (≥60%) between fish size-classes in January, March and April and between sexes for most sampling months. The average size of prey consumed was independent of fish mouth size. The feeding strategy of the threespine stickleback shifted from opportunist in winter to specialist in spring.     

Assessment of genetic structure,habitat suitability and effectiveness of reserves for future conservation planning of the Euphrates soft‐shelled turtle Rafetus euphraticus (Daudin, 1802)

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Physical habitat utilization of fish in a Sonoran Desert stream, Arizona, southwestern United States

Abstract– The physical habitat utilization of 7 species of native fishes in a Sonoran Desert stream, Aravaipa Creek, Arizona is described. The species occupied significantly different depths and velocities of water. Longfin dace ( Agosia chrysogaster ), speckled dace ( Rhinichthys osculus ) and loach minnow ( Tiaroga cobitis ) used similar depths and velocities. Two of the three larger species (Sonora sucker [ Catostomus insignis ] and roundtail chub [ Gila robusta ]) used areas of greater depth and reduced velocity. Desert sucker ( Catostomus clarki ) grouped with loach minnow and speckled dace in the velocity of water occupied, but utilized deeper waters. The spikedace ( Meda fulgida ) aligned very closely with desert sucker in use of all 3 physical habitat variables.     

Hydromorphological parameters indicating differences between single‐ and multiple‐channel mountain rivers in Germany,in relation to their modification and recovery

• 1. Despite a growing number of river restoration projects in Central Europe targeting hydromorphological improvements, it is still uncommon to evaluate the effects of restoration. Hydromorphological diversity in straightened, single‐channel sections was compared with restored or naturally developed multiple‐channel sections in German mountain rivers to identify parameters suitable for judging conservation value or restoration success.
• 2. Seven multiple‐channel sections were compared with nearby straightened single‐channel sections. Six hydromorphological parameters at macro‐, meso‐ and micro‐scales were recorded with transect point protocols, including aquatic, terrestrial and transient areas and width of channel features (main and secondary channels, sidearms, standing water bodies, bars, banks, floodplains and embankments). Depth, velocity and substrate type were measured at 400 points per river section. With these data 12 metrics were calculated, to provide comparison between the sections.
• 3. All macro‐ and meso‐scale parameters were well differentiated between single‐channel and multiple‐channel sections: mean channel width and shoreline length increased by factors of 2.1 and 2.4, respectively; the average number of channel feature types increased from two to 10 per section.
• 4. Micro‐scale parameters, such as velocity and depth variance, were significantly different between single‐channel sections and most multiple‐channel sections. Substrate composition was more diverse in the restored sections; the share of the major substrate was on average reduced from 75% to 62%. The Spatial Diversity Index described differences in substrate patterns best. The individual parameters correlated only within scales, but rarely between them.
• 5. Rapid assessment of restoration success or judgement of conservation value is made possible by combining simple macro‐ and meso‐scale parameters, e.g. increase of overall width or of transient areas, and presence of bars and islands. Increase in aquatic area and diversity of habitats are the most appropriate micro‐scale parameters required to evaluate habitat suitability for aquatic organisms. For depth and velocity data, variance should be analysed.

Copyright © 2008 John Wiley & Sons, Ltd.     

Seasonal variation in habitat use by salmon, Salmo salar, trout, Salmo trutta and grayling, Thymallus thymallus, in a chalk stream

Abstract A portable multi‐point decoder system deployed in a tributary of the River Itchen, a southern English chalk stream, recorded the habitats used by PIT‐tagged juvenile salmon, Salmo salar L., trout, Salmo trutta L. and grayling, Thymallus thymallus L., with a high degree of spatial and temporal resolution. The fishes’ use of habitat was monitored at 350 locations throughout the stream during September/October 2001 (feeding period) and January/February 2002 (over‐wintering period). Salmon parr tended to occupy water 25–55 cm deep with a velocity between 0.4 and 1.0 m s^?1. During both autumn and winter, first year salmon (0+ group) were associated with gravel substrate during the daytime and aquatic weed at night. In autumn, 1+ salmon were strongly associated with hard mud substrates during the day and with marginal tree roots at night. In winter, they were located on gravel substrate by day and gravel and mud at night. Trout were associated with a greater range of habitats than salmon, generally occupying deeper and faster water with increasing age. During the autumn, 0+ trout were located along shallow (5–10 cm) and slow (?0.1–0.4 m s^?1) margins of the stream, amongst tree roots by day and on silty substrates at night. During winter the 0+ trout occupied silty substrates at all times. As age increased, trout increasingly used coarse substrates; hard mud, gravel and chalk, and weed at night. All age groups of grayling (0+, 1+ and 2+) tended to occupy hard gravel substrate at all times and used deeper and faster water with increasing age. The 1+ and 2+ groups were generally found in water 40–70 cm deep with a velocity between 0.3 and 0.5 ms^?1, whilst the 0+ groups showed a preference for shallower water with reduced velocity at night, particularly in the winter. There were greater differences in the habitats used between species and age groups than between the autumn and winter periods, and the distribution of fish was more strongly influenced by substrate type than water depth or velocity. The results are discussed in relation to the habitat requirements of mixed salmonid populations and habitat management.     

Long‐term changes in the fish assemblage of the Laja River,Guanajuato, central Mexico

• 1. The structure and composition of fish communities in rivers of central Mexico have been altered as a result of water over‐exploitation, habitat fragmentation, introduction of exotic species, and pollution. However, the specific pattern and degree of change are poorly documented.
• 2. Long‐term information from the Laja River (Guanajuato, Mexico) in the Lerma River basin was used to explore trends in fish species richness and community composition (species origin, trophic niche, tolerance, and preferred habitat) from the 1960s to the present in both river and reservoir sites.
• 3. Declines in native, sensitive, benthic native and carnivore species ranging from 11% to 30% per decade, and increases in the number of tolerant and exotic species by 9–20% per decade, are documented. Repeated measures ANOVA and sign tests revealed significant declines in the number of benthic, native, carnivore and sensitive species. Species richness, number of exotics, tolerant species and omnivore species did not change statistically, though statistical power was low. Some important changes occurred in these variables, such as the expansion and establishment of exotics such as Xiphophorus variatus and Micropterus salmoides, which pose a serious potential threat to native species.
• 4. The changes in fish community composition for the Laja portray how the fish communities in other rivers in central Mexico, for which long‐term data do not exist, have changed or could change if environmental deterioration continues.

Copyright © 2006 John Wiley & Sons, Ltd.     

Habitat characterization,anthropogenic impacts and conservation of rhodolith beds off southeastern Malta

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Beware of changes: Conservation of Indo‐Pacific humpback dolphins in disturbed habitats

1. Protecting critical habitats of the Indo‐Pacific humpback dolphin, Sousa chinensis, is a hot topic of discussion for marine biodiversity conservation in China and many Southeast Asian countries. In practice, sound habitat protection action (HPA) planning often suffers from information gaps in macroscopic habitat configurations and changes in the habitat conditions of humpback dolphins.
2. Recent publications in the journal Aquatic Conservation: Marine and Freshwater Ecosystems (AQC) have served to advance humpback dolphin conservation in Chinese waters by resolving such habitat configurations and indicating significant changes in distribution patterns and habitat characteristics under intense coastal anthropogenic activity.
3. We highlight an integrative research framework to investigate habitat configuration and long‐term habitat changes when planning a holistic HPA programme for humpback dolphins. When constructing habitat configuration baselines, field surveys should be designed and conducted in a systematic manner to ensure survey efforts cover diverse environments equally, in either a spatially stratified or gridded pattern, to minimize potential spatial sampling biases. Long‐term habitat changes can be revealed by comparing satellite images from different decades. Changes in habitat preferences and habitat characteristics can be explored through questionnaire surveys on local ecological knowledge, associating historical occurrences with coastline features and projecting historical habitat configuration by species distribution modelling exercises.
4. A lack of good communication and sharing of information between research and management sectors can still be an obstacle to the implementation of sound conservation practices, however, even though there is robust scientific evidence to fill knowledge gaps in distribution and habitat baselines. We have addressed the need to establish a mechanism to improve and streamline information sharing between research teams, management sectors, and stakeholder groups.

     

Habitat of pike gudgeon Pseudogobio esocinus esocinus in Nakagawa River, northern Kyushu, Japan

ABSTRACT:   Habitat selection of the pike gudgeon Pseudogobio esocinus esocinus (Cyprinidae) was examined in the Nakagawa River in northern Kyushu, Japan. The study area was 80 m long with two meanders comprising three riffles and two pools, located 20 km upstream from the river mouth. The pike gudgeon were visually counted underwater. Larvae and juveniles were observed in the shallow and slow-flowing water near the shores. Simultaneously, young and adult individuals were observed to inhabit the river bed. Principal component analysis and cluster analysis were applied to estimate the microhabitat selections of the larvae, juveniles and other individuals by using four variables (water depth, current velocity, particle size of substrate and amount of organic matter). The larvae and juveniles inhabited the shallow (<30 cm) and slow-flowing waters (<6.5 cm/s) near the shore; habitat selection was independent of particle size of the substrate and the amount of organic matter present. Young and adult individuals inhabited the river bed independent of the four variables.