Fish Habitat Associations Research Articles

Local size structure and distribution of demersal fish in relation to sea pens and other benthic habitats in a deep-sea soft-bottom environment

Many fish species undergo ontogenetic habitat shifts as they grow to fulfill new biological, ecological and environmental requirements. While relationships between fishes and large hard-substrate cold-water corals (CWC) (e.g., Desmophyllum pertusum reefs) have frequently been studied, there are relatively fewer studies examining the relationships of fish with habitats specifically provided by smaller corals (e.g., sea pens) in soft-bottom environments. Despite this knowledge gap around soft-bottom corals, growing evidence of their importance has nonetheless justified their inclusion as conservation targets in numerous Marine Protected Areas (MPA), including the Canadian Laurentian Channel MPA. Here, we performed ROV and near-seabed drift-camera system surveys within the Laurentian Channel MPA in 2017 and 2018 to assess the influence of fish body size and habitat type on fish small-scale distribution in a low-relief deep-sea soft-sediment environment. We compared the local size structure of the four most abundant deep-sea demersal fish taxa of the channel (Redfish (Sebastes spp.), Witch Flounder (Glyptocephalus cynoglossus), Marlin-Spike Grenadier (Nezumia bairdii) and Longfin Hake (Phycis chesteri)) across one barren and five structural benthic habitats defined by the presence of nine dominant epibenthic invertebrates (actiniarians and CWCs). We used generalized additive models to identify biotic (benthic habitats) and abiotic (depth, bottom types) covariates of size for each taxon. We observed 15,381 fish within the 43.6-ha study area, of which 7,511 fish were measured. Juveniles represented 99% of all fish measured, with a notable increase in average fish size in 2018. While we did not find any associations between benthic habitats and fish life stages, the analysis revealed a significant increase in fish size within sea pen habitats for all four taxa. Conversely, we found a taxon-specific influence of bottom type on fish size for all taxa. In addition, Redfish and Longfin Hake size was positively correlated with depth. For deep-sea demersal fish taxa of the MPA, our results suggest that 1) sea pens provide nursery habitat for early-life stages, 2) fish undergo ontogenetic shifts in micro-habitat use and specialization, and 3) fish-habitat associations appear to be facultative rather than obligate. Through the use of in-situ video data, this study provided evidence that small and large fish do not use the same micro-habitats, and that sea pens contribute significantly to fish habitat despite providing less habitat heterogeneity than reef-forming scleractinians or large gorgonians. These results contribute to empirical understanding of fish-habitat relationships at different fish life stages and may inform fisheries management, as well as monitoring efforts in the MPA and other protected deep-sea environments.

Do longsnout seahorses Hippocampus reidi (Syngnathiformes: Syngnathidae) have a holdfast preference?

Abstract Coastal systems encompass a range of ecotones that are important for fish species, providing diverse micro-habitats and grounds for foraging, protection from predation, reproduction and areas for recruitment. However, most of these systems face major threats from human activities. Considering the increasing levels of human disturbance in coastal ecosystems, understanding fish-habitat associations may provide important insights into patterns of species occurrence and distribution in human-impacted systems, which can support the development of effective conservation and management measures. In this context, we investigated the relationship between seahorses (Hippocampus reidi) and both habitat complexity and different holdfast species, to determine possible variation between locations and among seasons. Data were obtained from the rocky reefs of Guanabara (Urca Beach) and Sepetiba (Duas Irmãs Island) bays, in southeastern Brazil. Seahorses were counted, and the holdfast being used by each individual was recorded and identified to species or assigned to a morphofunctional group. The beaches differed in holdfast composition and morphofunctional groups, yet sharing some morphofunctional groups. Seahorses were more frequently associated with branching holdfasts at both sites, and also with foliaceous and massive. Association with algae were particularly found in Urca, while the coral Carijoa riisei in Duas Irmãs Island.

The context dependency of fish-habitat associations in separated karst ecoregions.

Fish populations may be isolated via natural conditions in geographically separated ecoregions. Although reconnecting these populations is not a management goal, we need to understand how these populations persist across landscapes to develop meaningful conservation actions, particularly for species occupying sensitive karst ecosystems. Our study objective was to determine the physicochemical factors related to the occurrence of four spring-associated fishes. Arbuckle Uplift and Ozark Highlands ecoregions, USA. We used a hierarchical approach to identify habitat relationships at multiple spatial scales. We collected detection data using snorkeling and seining. We examined the physicochemical relationships related to the detection and occurrence of four spring-associated fishes using occupancy modeling in a Bayesian framework. We found physicochemical relationships that differed and were similar between ecoregions for several fishes. For three species, we found different water temperature relationships between ecoregions. Smallmouth bass were ubiquitous in their use of drainage areas in the Ozark Highlands but only associated with the lower network of the Arbuckle Uplift. There were several mirrored relationships between ecoregions, including an interaction between residual pool depth and water temperature, where sites with deeper pools were more likely to be occupied during warmer water temperatures. There were single-species occurrence relationships with percent vegetation and percent agriculture. Lastly, snorkeling was a more efficient sampling method compared to seining for all fishes. Our results indicate stream temperature mitigation may be possible via the maintenance of key channel morphologies, and we identify shared stressors between ecoregions. Channel mitigation to maintain reaches with deeper pools may be an important strategy for maintaining thermal refugia, particularly when considering climate change. Identifying the mechanistic underpinning of other multiscale ecological relationships would be helpful to discern if some of the different ecoregion relationships represent warning signals or interactions with unmeasured biotic or abiotic factors.

Discrete seafloor features associated with juvenile haddock (Melanogrammus aeglefinus): A coarse-graining approach for identifying habitat scale

Ecological patterns and processes occur at a myriad of spatial and temporal scales. Determining the appropriate scale(s) to collect and analyze data depends on the phenomena being studied and no one scale is appropriate for all of these. Knowing relevant measurement scales avoids the risk of presenting results that are merely a function of measurement scale rather than those relevant to actual ecological processes. Attribution of patterns to ecological processes requires a means to measure and evaluate these patterns. We present a standardized method to determine relevant spatial scales of fish-habitat associations observed from linear transect data on juvenile haddock (Melanogrammus aeglefinus), collected from six sites on the Scotian Shelf, off Canada's eastern coast. The survey data came from a large spatial scale research project undertaken by Fisheries and Oceans Canada to investigate spatial distribution of demersal fish in relation to seabed habitat in 2002 and 2003. We examined the relationship between two elements of this extensive dataset – the “towcam” video survey of demersal fish, and the interpreted surficial geology maps derived from sidescan sonar. We used the data from these surveys (48 towcam survey transect lines; 6 study sites, 2 5-km transect lines per site, day and night surveys per line, in each of 2 years = 240 km of transects), superimposed on the interpreted surficial geology layer collected at the same time. The resolution of the observations (∼2.5 m) facilitated a detailed examination of the spatial scales of juvenile haddock association with seabed habitat. This was achieved using a “coarse-graining” approach, which we applied by summarizing fish abundance and seabed habitat proportions across bin sizes starting at 5 m and progressively doubling to 640 m. We tallied significant correlations by bin size to observe patterns in fish-habitat associations as a function of measurement scale, for each age group and diel period. We found that Juvenile haddock-seabed associations deteriorated at the grain limits marking the range of spatial scaling relevant for this phenomenon. We present a robust approach for quantifying appropriate scales of aggregations across linear transects which can serve as an important tool for basing observations to describe ecological patterns in space.

Telemetry-based spatial–temporal fish habitat models for fishes in an urban freshwater harbour

Fish habitat associations are important measures for effective aquatic habitat management, but often vary over broad spatial and temporal scales, and are therefore challenging to measure comprehensively. We used a 9-year acoustic telemetry dataset to generate spatial–temporal habitat suitability models for seven fish species in an urban freshwater harbour, Toronto Harbour, Lake Ontario. Fishes generally occupied the more natural regions of Toronto Harbour most frequently. However, each species exhibited unique habitat associations and spatial–temporal interactions in their habitat use. For example, largemouth bass exhibited the most consistent seasonal habitat use, mainly associating with shallow, sheltered embayments with high aquatic vegetation (SAV) cover. Conversely, walleye seldom occupied Toronto Harbour in summer, with the highest occupancy of shallow, low-SAV habitats in the spring, which corresponds to their spawning period. Others, such as common carp, shifted between shallow summer and deeper winter habitats. Community level spatial–temporal habitat importance estimates were also generated, which can serve as an aggregate measure for habitat management. Acoustic telemetry provides novel opportunities to generate robust spatial–temporal fish habitat models based on wild fish behaviour, which are useful for the management of fish habitat from a fish species and community perspective.

Spatial variability in the structure of fish assemblages associated with Laminaria hyperborea forests in the NE Atlantic

Understanding fish-habitat associations is critical for ecosystem-based approaches to management and conservation. Kelp species, which are estimated to inhabit around 25% of the world's coastline and underpin highly productive and biodiverse ecosystems, are widely recognised as important nursery and foraging habitats for coastal fish species. However, quantitative assessments of fish assemblages within kelp forests are lacking for many regions. Here, we used Baited Remote Underwater Video (BRUV) and Underwater Visual Census (UVC) to quantify fish assemblages in Laminaria hyperborea forests at eight shallow subtidal rocky reefs that spanned 9° of latitude in the United Kingdom (UK). Fish assemblages were a ubiquitous and conspicuous component of kelp forest communities at all sites. BRUV surveys recorded marked regional-scale variability, with latitudinal shifts in assemblage structure and particularly distinct assemblages recorded in southwest England. These patterns were largely due to greater abundances of Pollachius spp. (i.e. saithe and pollock) in northern regions and higher numbers of Gobiusculus flavescens (two-spotted goby) and labrid species (i.e. rock cook, goldsinny and ballan wrasses) in southern regions. Unlike BRUVs, UVC surveys did not detect significant regional-scale variation in assemblage structure but did detect significant site-level differences, highlighting differences between the two techniques. BRUV surveys also recorded clear latitudinal trends in richness, with more taxa recorded at lower latitudes. Fish assemblages in the NE Atlantic have been, and will continue to be, impacted by ocean warming and fishing activities. Greater spatiotemporal coverage of kelp forest surveys and ongoing robust monitoring is needed to better understand and manage future ecological changes.

Habitat associations of riverine fishes among rocky shoals

AbstractUnderstanding species' associations with physical habitat conditions is a fundamental goal of ecology. For organisms that occupy lotic ecosystems, relationships to streamflow are of particular importance, but these associations are unstudied for most species. We tested the predictability of fish–microhabitat relationships in river shoals (shallow, rocky areas with relatively swift water flow) using a large data set from the Conasauga River in Georgia, USA. Our objective was to assess the consistency of species‐specific relationships with flow‐dependent variables (depth, velocity, Reynolds number and Froude number) while accounting for other microhabitat variables (e.g. vegetation). We used data from 8285 seine‐sets collected during late summer or autumn at 26 sites over 12 years to relate occurrence and counts of 22 fish species to habitat variables using generalised linear multiple regression models. Results showed that microhabitat models explained a substantial amount of the variation in counts for some species, although other species were poorly predicted. We classified 16 species as velocity specialists and nine species as depth specialists, with six species specialised for depth and velocity and three species classified as depth and velocity generalists. The variability in habitat associations that we observed suggests that species will be unevenly affected by anthropogenic activities that alter flows.

Habitat associations of imperilled fishes after conservation intervention in the Cape Fold Ecoregion, South Africa.

The aim of this study was to examine the habitat associations of a native cyprinid community of the recovering Rondegat River in the Cape Fold Ecoregion of South Africa as part of a long-term native fish abundance monitoring project. Relative abundance data were extracted from underwater video camera footage across the longitudinal gradient of the river in three sampling instances. Using multivariate methods the authors assessed community composition with respect to habitat, its overlap with a protected area and species-specific abiotic predictors of relative abundance. Distance from the uppermost site in the river was the most significant predictor of species abundance, indicating spatial segregation and varying overlap between species. The protected status of sites in the upper reaches, vegetated substrates and the size of individual sites were the most impactful on the relative abundance of the endangered fiery redfin Pseudobarbus phlegethon. The results of this study indicate that underwater video monitoring is an effective and low-cost approach that can inform conservation recommendations. Reducing agricultural runoff and sedimentation in the lower reaches may be useful further interventions to maintain key habitats of submerged vegetation.

Seamount seascape composition and configuration shape Southwest Indian Ridge fish assemblages

Seamounts are commercially important fishing grounds. Yet, little is known about their physical characteristics as fish habitat, important for informing conservation and ecosystem-based management.This study examines how multiscale seabed spatial heterogeneity influences commercially important fish families at three Southwest Indian Ridge seamounts (Coral Seamount, Melville Bank and Atlantis Bank). We quantified seascape heterogeneity from bathymetry and geomorphological habitat maps and identified 15 focal fish families from video data. Fish-habitat associations were examined using spatial pattern metrics that measured terrain morphology, seascape composition (variety and relative abundance of patch types) and seascape configuration (spatial arrangement of patches). Broader seascape context was characterised by geographic location and water depth. Multivariate regression trees and random forests modelled fish-habitat associations and identified the most influential explanatory variables.Assemblage characteristics and individual families were strongly influenced by geographic location and depth, and at finer scales (500 m buffers) seascape composition and configuration helped explain fish-habitat associations. Spatially continuous summit habitat and complex shaped ridge features supported high abundance and diversity of commercial fish families. Metrics of seascape composition and configuration (i.e., habitat size, shape and structural connectivity) had higher predictive power than the terrain metrics commonly used in developing proxies for deep-water fish species and biodiversity.These outcomes indicate that seascape metrics, commonly applied on land and in shallow marine environments, are also relevant environmental predictors of fish distributions in deep-sea environments. We highlight strong context dependency and depth-specific associations that hinder attempts to draw wider generalisations on fish-seascape linkages for seamounts.

Scale‐dependence of fish habitat associations in a North American river system

Abstract Determining the appropriate measurement scale to assess habitat variables is critical for ecologists assessing biological or ecological conditions. Depth, velocity, substrate, woody debris and other fish cover variables occur on both reach and microhabitat scales, and fish habitat associations with these variables may be scale‐dependent. The aim of this work was to better understand the importance of scale for fish–habitat associations with these variables in a framework consistent with environmental filtering and to test the hypothesis that habitat variable importance is scale‐dependent. I used prepositioned areal electrofishing in wadeable streams of the Delaware River basin to evaluate the associations of fish with the same variables summarised on different reach and microhabitat scales. The importance of scale for fish–habitat associations was assessed using two approaches that approximate an environmental filtering framework: variance partitioning with (1) ordination and (2) generalised linear mixed models. Variables on both the reach and microhabitat scales explained a significant fraction of the total variation in fish community composition (p < 0.05). Variation decomposition of reach‐ and microhabitat‐scale effects revealed 20.2% and 2.0% of all variation were due uniquely to reach and microhabitat scales, respectively. Measures of coarseness, embeddedness, amount of riffle and areal coverage of five fish cover variables were significant explanatory variables of community composition at the reach scale only (p < 0.05). Velocity and mesohabitat (amount or presence of riffle) were the only two habitat features that were significant explanatory variables of fish community composition at both the reach and microhabitat scales (p < 0.05). Individual models of species occurrence revealed similar patterns as seen with analyses of community composition. For many fishes, habitat features quantified at the reach scale were more explanatory than at the microhabitat scale. Longnose dace (Rhinichthys cataractae) were more dependent upon microhabitat variables than reach‐scale variables, relative to other fishes. Mean velocity at the reach scale was the most important explanatory variable for explaining fish community composition and indicated support for the concept of environmental filtering at the reach and microhabitat scales. Few studies of fish occurrence have incorporated a study design and analytical framework that approximates the hierarchical nature of habitat. This study identifies important scales and predictors, demonstrates the importance of a multiscale approach, and provides support for the environmental filtering concept at the reach and microhabitat scales. These findings will allow ecologists to better account for scale‐dependent habitat associations and justify the use of fish habitat associations on reach and microhabitat scales for assessing biotic integrity, restoration and conservation of fishes.

Structure‐from‐motion photogrammetry demonstrates that fine‐scale seascape heterogeneity is essential in shaping mesophotic fish assemblages

AbstractBenthic components of tropical mesophotic coral ecosystems (MCEs) are home to diverse fish assemblages, but the effect of multiscale spatial benthic characteristics on MCE fish is not well understood. To investigate the influence of fine‐scale benthic seascape structure and broad‐scale environmental characteristics on MCE fish, we surveyed fish assemblages in Seychelles at 30, 60 and 120 m depth using submersible video transects. Spatial pattern metrics from seascape ecology were applied to quantify fine‐scale benthic seascape composition, configuration and terrain morphology from structure‐from‐motion photogrammetry and multibeam echosounder bathymetry and to explore seascape–fish associations. Hierarchical clustering using fish abundance and biomass data identified four distinct assemblages separated by the depth and geographic location, but also significantly influenced by variations in fine‐scale seascape structure. Results further revealed variable responses of assemblage characteristics (fish biomass, abundance, trophic group richness, Shannon diversity) to seascape heterogeneity at different depths. Sites with steep slopes and high terrain complexity hosted higher fish abundance and biomass, with shallower fish assemblages (30–60 m) positively associated with aggregated patch mixtures of coral, rubble, sediment and macroalgae with variable patch shapes. Deeper fish assemblages (120 m) were positively associated with relief and structural complexity and local variability in the substratum and benthic cover. Our study demonstrates the potential of spatial pattern metrics quantifying benthic composition, configuration and terrain structure to delineate mesophotic fish–habitat associations. Furthermore, incorporating a finer‐scale perspective proved valuable to explain the compositional patterns of MCE fish assemblages. As developments in marine surveying and monitoring of MCEs continue, we suggest that future studies incorporating spatial pattern metrics with multiscale remotely sensed data can provide insights will that are both ecologically meaningful to fish and operationally relevant to conservation strategies.

Developing habitat associations for fishes in Lake Winnipeg by linking large scale bathymetric and substrate data with fish telemetry detections

Understanding relationships between freshwater fishes and habitat is critical for effective fisheries and habitat management. Habitat suitability indices (HSI) are commonly used to describe fish–habitat associations in rivers and other freshwater ecosystems. When applied to large lakes however, standard sampling procedures are inadequate because of larger sampling areas and an increased risk of fish collection bias through one-time observations. Here, we use lake bathymetry, substrate, and multiple fish telemetry detections collected from a systematically deployed receiver grid to develop HSI for four fish species (lake sturgeon, freshwater drum, common carp, and walleye) in Lake Winnipeg. Seasonal variations in habitat use based on water depth and substrate were observed in three of four species. Lake sturgeon remained in shallow locations with predominantly gravel substrate near the mouth of the Winnipeg River regardless of season. Freshwater drum persisted over fine substrate in both summer and winter but had a broader depth range in the summer compared to winter. Common carp shifted from mid-range depths and silt substrate in the summer to shallow depths and gravel substrate in the winter. Walleye showed an unchanging association to fine substrate but expanded from primarily mid-range depths in the summer to include shallower depths in the winter. These findings show how multiple telemetry detections per fish can be combined with hydroacoustic data to provide informative habitat associations for fishes in a large lacustrine ecosystem.

Characterizing Fish–Habitat Associations through Paired Fisheries‐Independent and In Situ Habitat Assessments

AbstractEstuarine habitat has a significant influence on the growth, recruitment, and survival of fish and invertebrate species, and understanding habitat dynamics can improve fisheries management. However, the cost and effort associated with habitat monitoring can be limiting, and many large‐scale fisheries‐independent monitoring programs do not capture habitat and biological data concurrently. Consequently, fisheries and their associated habitats are often managed separately. We designed a pilot study to assess the utility and effectiveness of incorporating rapid in situ habitat characterization into a statewide fisheries management program. The occurrence of six focal species (Red Drum Sciaenops ocellatus, Spotted Seatrout Cynoscion nebulosus, blue crab Callinectes sapidus, Atlantic Croaker Micropogonias undulatus, brown shrimp Farfantepenaeus aztecus, and white shrimp Litopenaeus setiferus) and the overall faunal community composition were compared across estuarine habitats to assess the ability of this method to accurately depict fish–habitat associations. Focal species’ occurrence and community composition was significantly correlated with shoreline vegetation, seagrass presence, presence of mangroves, substrate type, and heterogeneity in vegetated habitat. This study demonstrates an effective approach to integrating habitat into fisheries‐independent monitoring in pursuit of an ecosystem‐based approach to fisheries management.

Offshore snapper and shark distributions are predicted by prey and area of nearby estuarine environments in the Gulf of Mexico, USA

Seascape ecology has demonstrated that marine fishes are associated with multiscale habitat characteristics; however, most species distribution models focus on only a few predictors (e.g. depth, temperature), and this limits knowledge of essential fish habitat characteristics. Our objectives were to (1) determine habitat associations of offshore predatory marine fishes using a comprehensive suite of predictors, including area of nearby estuarine environments, (2) assess variable influence, and (3) model the spatial distribution of selected fishes in the families Carcharhinidae and Lutjanidae. We hypothesized that the concept of coastal outwelling would be evidenced by species associations with areas of nearby estuarine environments, and prey abundance would correlate with predator distributions. Species distribution models were developed for 2 snapper and 3 shark species in the northern Gulf of Mexico, USA. We used 34 multiscale predictors to evaluate how fish probability of presence or catch per unit effort (CPUE) were associated with oceanography, geography, substrate, area of nearby wetlands and estuaries, and prey abundance. Boosted regression trees, a machine-learning technique, modeled the most influential variables and predicted distributions. Model validation showed an overall accuracy of 79-86%, and CPUE models explained >40% of model deviance. Oceanographic variables, particularly mixed layer depth, were most influential and most frequently selected. As hypothesized, predatory fish distributions were predicted by prey abundances, and shark distributions were predicted by area of nearby coastal wetlands and estuaries. Our findings suggest that spatial models can provide novel insights into prey associations and linkages of marine species with nearby wetlands and estuaries.

Effects of habitat on reef fishes biodiversity and composition in rocky reefs

Reef fish are highly valuable to human society—socially, nutritionally and economically. However, they are vulnerable to both overfishing and habitat degradation. Understanding the community structure and habitat associations of reef fish is important for their management and conservation. Using a gillnet survey conducted in a subtropical rocky reef area of Ma’an Archipelago, China, we developed habitat models linking reef fish diversity and community composition with habitat factors. The parsimonious generalized additive model results showed that higher reef fish diversity was associated with southern shallower water, temperature of 25°C, lower levels of dissolved oxygen and chlorophyll a, and rock bottom type. The multivariate generalized linear model identified that month, depth, bottom type, and location significantly influenced the local reef fish; these habitat variables explained 18% of the variation in reef fish community composition. However, the lack of strong patterns and correlations between species derived from the joint species distribution model revealed that reefs within our study area are difficult to classify based on habitat-driven patterns in their associated reef fish assemblages. These findings enhance our understanding of the habitat effects on reef fish diversity and community composition and have relevance for the management of reef fish, including habitat zonation and deployment of artificial reefs.

Using Geomorphology to Better Define Habitat Associations of a Large-Bodied Fish, Common Snook Centropomus undecimalis, in Coastal Rivers of Florida

To adequately protect habitat for economically important fishes, the habitats used must first be identified and described. Coastal geomorphology is often overlooked as an influential parameter of fish habitat use in favor of readily available data taken at the time of sampling. We hypothesized that river dynamics (e.g., length, watershed, floodplain connectivity) and mesohabitat categories based on geomorphology (e.g., backwater, river bend) were at least as important as fine-scale microhabitat (e.g., depth, shore type) for describing the distribution and habitat affinities of Common Snook Centropomus undecimalis (hereafter referred to as snook) in coastal rivers of the Atlantic coast and Tampa Bay, Florida. Contrary to previously studied rivers where adult snook abundance increased during a seasonal prey pulse, adult snook abundance in the study rivers differed little between seasons and the rivers were used as nurseries by juveniles. Mesohabitat categories were important for describing snook distribution. For example, the smallest snook (≤ 250 mm total length, TL) strongly selected for backwater habitats while the largest (≥ 851 mm TL) selected river bends. Detailed microhabitat data collected at individual capture locations were helpful in describing the habitat associations of the smallest size group of snook (shallow depths and aquatic macrophytes with various shore types) and for characterizing river bends (high flow, deep water, and lower salinities) but were not strongly associated with other snook sizes or mesohabitat categories. Thus, broader scale habitat features were found to be equally as important as detailed microhabitat and should be considered when informing conservation efforts.

Quantifying links between instream woody habitat and freshwater fish species in south‐eastern Australia to inform waterway restoration

Abstract Removal of instream woody habitat (IWH) is one factor attributed to declines in fish populations worldwide. Restoration of IWH to help fish populations recover is now common; however, quantitative predictions about the outcomes of these interventions is rare. As such, quantitative links between IWH and fish abundance is of interest to managers to inform conservation and restoration activities. Links between instream habitat attributes, especially IWH, and selected fish species of recreational, cultural, and ecological significance were explored at 335 sites spanning eight streams across south‐eastern Australia. Data were collected on fish abundance and length, IWH density and a range of other habitat attributes at a scale that incorporated at least one of each of the major mesohabitat types (functional river elements). The data were analysed using Bayesian hierarchical generalized linear mixed models to examine fish habitat associations and used to make quantitative predictions of responses to future restoration. Strong positive relationships were found between fish abundance and IWH density and the strength of this relationship varied between species and waterways. Murray cod (Maccullochella peelii), a species commonly targeted by IWH interventions, displayed the strongest association with IWH density. River blackfish (Gadopsis marmoratus) also showed a significant relationship with IWH, but this effect was waterway specific. Fish length was only related to IWH for river blackfish. These results may reflect differences in the life histories of these two species. We suggest that differences in habitat association through ontogeny may be more relevant at smaller spatial scales. The results generated in this study can be used to guide waterway restoration and develop quantitative predictions about how fish might respond to IWH interventions across south‐eastern Australia. This approach provides a powerful quantitative framework within which to explore management options and objectives, and to test our predicted responses to habitat restoration.

The influence of habitat on the spatio-temporal dynamics of fish assemblages in a lagoon-estuarine system of the Mexican Pacific

Fish assemblages change significantly with physical and chemical characteristics of water; however, their response to the variability of geomorphic habitats has been rarely evaluated in lagoon-estuarine in one of these systems of the Mexican Pacific. Spatio-temporal variation of fish assemblage structure was assessed for three habitats: lagoon, estuarine, channel and inlet. The hypothesis was that sheltered areas support comparatively higher richness and abundance of fish species, with more small-sized specimens than the most exposed areas. We found that the ichthyofauna differed significantly among habitats. Several species were smaller in the lagoon compared with the other habitats, suggesting a use of the lagoon as a nursery ground. Moreover, dominant species for the lagoon were rarely found or absent in the inlet, whereas others were found only present or with higher abundance in the inlet. Although seasonal differences in richness and composition were detected, the evidence of fish-habitat associations for many species was noticeable regardless of seasonality, probably due to a high percentage of resident species during the annual cycle. The lagoon supports a greater abundance and species richness, due to a more sheltered and structured habitat, evidencing habitat-driven segregation in fish assemblages, and an aspect that should be incorporated for management of coastal ecosystems.

Fish-habitat associations on a subsea pipeline within an Australian Marine Park

Subsea pipelines have been installed in all major hydrocarbon basins across the globe to support the offshore Oil & Gas (O&G) industry. These artificial structures provide hard substratum that can be colonised and utilised by sessile and mobile organisms. The present study utilises industry-collected remotely operated vehicle (ROV) video to assess fish species richness and abundance, and marine growth type, extent and complexity along sections of a subsea gas pipeline, in 56–82 m depth, that traverses the Australian Commonwealth Montebello Marine Park (MMP). A total of 7493 fish from 81 species and 33 families were recorded from 606 analysed 10 m transects spaced across sections of the pipeline. Of these 81 species, 27 are considered fishery-target species in the Pilbara Demersal Scalefish fishery (PDSF), with select commercial fishing activities permitted with authorisation within the Marine Park. A moderate abundance (175) of sub-adult red emperor (Lutjanus sebae), a fishery-indicator species, were observed along the pipeline. Eleven different categories of marine growth habitat were observed, with the pipeline possessing quite uniform coverage of encrusting marine growth (coralline algae, bryozoans, ascidians, etc.) with patchy occurrences of more structurally complex sponges and black/octocoral forms. Fish species richness and abundance of the commercially targeted Moses’ snapper (Lutjanus russellii) were correlated positively with increasing cover of sponges. The pipeline itself had very few spans and was never more than fractionally buried. Despite the somewhat homogenous habitats, depths, and position of the pipeline relative to the seafloor, presence of a field joint indent had a positive influence on the abundance of some common and commercially important fish species. This study demonstrates the ecological value of ROV footage obtained during industry inspection operations that were conducted for reasons unrelated to the determination of ecological information. The pipeline offers a corridor of hard bottom habitat within a marine park that facilitates epibiotic growth and the presence of reef-associated species in a region characterised by sandy sediments. Results indicate the potential importance of subsea O&G infrastructure as a habitat for fish, and in consequence, potentially also as structures with value to fisheries.

Estuary habitat associations for juvenile Pacific salmon and pelagic fish: Implications for coastal planning processes

Abstract Assessment of risk from industrial developments often relies on simple habitat descriptions for focal species. However, simple habitat metrics may not be accurate predictors of locations that species actually use. Understanding the nature of habitat is particularly pressing for estuaries, as they are among the most degraded ecosystems globally but provide critical rearing habitat for many species, including Pacific salmon. Canadian environmental impact assessment approaches use simple habitat‐type models to assess risk from developments and assume that different species of salmon rely on the same habitat. This study asked what combination of habitat type and biophysical covariates best predicted use of estuary habitat by juvenile salmon and two dominant small pelagic fish. Fish were sampled via purse seine throughout the Skeena River estuary (British Columbia, Canada) for 2 years across different habitat types (eelgrass, open water, sandy banks, and rocky shores). Simple habitat‐type models were compared with models with more complex biophysical variables to predict the variability in relative abundance of juvenile Chinook (Oncorhynchus tshawytscha), coho (Oncorhynchus kisutch), and sockeye (Oncorhynchus nerka) salmon, along with pelagic fish species Pacific herring (Clupea pallasii) and surf smelt (Hypomesus pretiosus). The combination of variables that best predicted abundance differed across fish species. Pelagic fish were associated with near‐shore sites, increased temperature (herring), and increased salinity (smelt). Juvenile coho and sockeye salmon (but not Chinook), were more abundant in higher turbid waters. Chinook and sockeye salmon used eelgrass habitat more frequently than other habitat types, whereas coho salmon were more abundant in areas with high macroalgae cover. Models with these variables had greater predictive power than those using habitat type alone for juvenile salmon. Simple classifications of estuary habitat currently used in environmental risk assessment may not reflect the complex nature of fish–habitat associations. Understanding biophysical factors associated with estuary fish abundance can inform management of estuary habitat to support their nursery function for important fish.