Fish Community Assemblages Research Articles

A Comparison of Electrofishing and Visual Surveying Methods for Estimating Fish Community Structure in Temperate Rivers

AbstractStudies attempting to describe fish community structure in shallow riverine environments typically rely on electrofishing and/or visual (snorkelling) surveys, but few have addressed the relative efficiencies of these two methods at estimating fish density and biomass across wide ranges of geography, taxonomy and life history stages. Multiple paired electrofishing and visual surveys were conducted in 18 temperate Canadian rivers in order to obtain community‐wide density and biomass estimates from both methods. Partial canonical multivariate analyses were applied to the paired fish community matrices comparing the results of both surveying methods at the taxonomic levels of family, genus and species, as well as size classes within families and species, to assess the particular effectiveness of each sampling method. Although electrofishing estimates of family and species richness were generally greater, snorkelling surveys tended to generate higher density and biomass estimates for different size classes of many salmonid and cyprinid species. Moreover, mean river biomass estimates derived from visual surveying matched those obtained from our best mean river biomass estimates arising from the two methods combined. This study provides empirical evidence that electrofishing and visual survey methods generate different types of information when assessing fish community structure at the family level or by size classes. Our results provide ample background information for determining the most accurate sampling method for a particular fish community assemblage, which is fundamental to fisheries management and research. Copyright © 2014 John Wiley & Sons, Ltd.

Effects of habitat relocation on fish community structure- a case study

Local habitat structure and the environment in which it occurs are some of the key components in the development of fish communities. In this case study we examined a snapshot of their relative role following relocation of four artificial reefs (ARs) from a coral reef environment to a sandy area with adjacent sea grass beds. Monitoring the fish communities on ARs and in the surrounding areas revealed that in their new locations, the ARs contained greater fish richness and abundance, with more diurnal than nocturnal fish, but their feeding guilds were similar to those of fish in the reef location. A multivariate analysis showed that the ARs had distinctly different fish assemblage from those of their surroundings regardless of their location. Nonetheless, we identified an effect of the surroundings on AR fish community assemblage. We propose that on a meso- scale, fish community structure is primarily dependent on the properties of the AR rather than on those of the surrounding environment.

Fish community assemblages changed but biomass remained similar after lake restoration by biomanipulation in a Chinese tropical eutrophic lake

While the effects of lake restoration by fish manipulation are well-studied in the temperate zone, comparatively little information is available on this issue from tropical lakes. It may be expected that fish removal leads to faster recovery of the fish stock here than in temperate lakes due to more frequent and earlier reproduction, which may, in turn, delay positive effects of the restoration. We studied the community composition, feeding type and abundance of fish in three basins of a tropical shallow lake: one unrestored basin (UR) and two basins restored by fish manipulation and transplantation of submerged macrophytes. While omni-benthivorous fish dominated the biomass in the restored basins 3 and 5 years after restoration, planktivores were most abundant in the UR, although total fish biomass remained similar. One-way analyses of similarities based on fish species presence/absence, abundance and biomass data revealed significant differences in fish community composition among the restored basins and UR, and redundancy analyses further indicated that submerged macrophytes were a key driver behind this difference. Our results indicate that active implantation of submerged macrophytes to stabilise the fish community is a tool to consider when planning lake restoration by biomanipulation in the tropics.

Predator density and timing of arrival affect reef fish community assembly

Most empirical studies of predation use simple experimental approaches to quantify the effects of predators on prey (e.g., using constant densities of predators, such as ambient vs. zero). However, predator densities vary in time, and these effects may not be well represented by studies that use constant predator densities. Although studies have independently examined the importance of predator density, temporal variability, and timing of arrival (i.e., early or late relative to prey), the relative contribution of these different predator regimes on prey abundance, diversity, and composition remains poorly understood. The hawkfish (Paracirrhites arcatus), a carnivorous coral reef fish, exhibits substantial variability in patch occupancy, density, and timing of arrival to natural reefs. Our field experiments demonstrated that effects of hawkfish on prey abundance depended on both hawkfish density and the timing of their arrival, but not on variability in hawkfish density. Relative to treatments without hawkfish, hawkfish presence reduced prey abundance by 50%. This effect increased with a doubling of hawkfish density (an additional 33% reduction), and when hawkfish arrived later during community development (a 34% reduction). Hawkfish did not affect within-patch diversity (species richness), but they increased between-patch diversity (beta) based on species incidence (22%), and caused shifts in species composition. Our results suggest that the timing of predator arrival can be as important as predator density in modifying prey abundance and community composition.

Trait contributions to fish community assembly emerge from trophic interactions in an individual-based model

Community ecology seeks to understand and predict the characteristics of communities that can develop under different environmental conditions, but most theory has been built on analytical models that are limited in the diversity of species traits that can be considered simultaneously. We address that limitation with an individual-based model to simulate assembly of fish communities characterized by life history and trophic interactions with multiple physiological tradeoffs as constraints on species performance. Simulation experiments were carried out to evaluate the distribution of 6 life history and 4 feeding traits along gradients of resource productivity and prey accessibility. These experiments revealed that traits differ greatly in importance for species sorting along the gradients. Body growth rate emerged as a key factor distinguishing community types and defining patterns of community stability and coexistence, followed by egg size and maximum body size. Dominance by fast-growing, relatively large, and fecund species occurred more frequently in cases where functional responses were saturated (i.e. high productivity and/or prey accessibility). Such dominance was associated with large biomass fluctuations and priority effects, which prevented richness from increasing with productivity and may have limited selection on secondary traits, such as spawning strategies and relative size at maturation. Our results illustrate that the distribution of species traits and the consequences for community dynamics are intimately linked and strictly dependent on how the benefits and costs of these traits are balanced across different conditions.

Predicting fish assemblages and diversity in shallow lakes in the Yangtze River basin

Habitat modifications induced by humans severely impact biotic components of freshwater ecosystems. In China, shallow lakes in the Yangtze River basin are facing severe habitat degradation induced by pollution, habitat losing, macrophytes disappearing and fishery activities. Effectively modeling the fish communities on the basis of biotic and abiotic environmental descriptors would be helpful to understand the relationships between fish and their environment, and to develop suitable conservation strategies to sustain the biodiversity in these ecosystems. From 2007 to 2009, investigations were carried out on fish and their environment in 6 lakes distributed in the mid-reach of the Yangtze River basin. According to the CPUE values of each fish species from each sampling, 117 datasets were ordinated using self-organizing map (SOM). Fish communities were classified into three clusters of species assemblages, spatial and temporal distributions were showing in it. Seasonal changes in fish community were more obvious in vegetated habitats than in unvegetated areas. The total CPUE, fish diversity and species richness were significantly different among the assemblages ( p < 0.01). Based on the indicative value of each species in each cluster calculated by Indval method, 16 species were identified as indicators: 13 indicators in cluster G1 are pelagic or benthopelagic fish, the only one indicator species in G2 is a tolerant species ( Culter dabry B.), while the other two indicator species in G3 are demersal fish ( Rhinogobius giurinus R. and Odontobutis obscurus T. & G.). These results are in agreement with the contributions of different ecological groups of fish in each assemblage in the trained SOM, pelagic and benthopelagic fish were found having more activities in spring and winter, while more activities of demersal fish were found in summer and autumn. Fish community assemblages, the total fish CPUE, diversity and species richness in those lakes were then predicted by 15 abiotic and biotic factors using random forest (RF) and classification and regression tree (CART) predictive models. The predicted assignment of each site unit to the correct assemblage had an average success of 74.4% and 60.7% in RF and CART models, respectively. The dominant variables for discriminating three fish assemblages were water depth, distance to the bank and total phosphorus. While the two important variables in prediction fish CPUE, diversity and species richness were lake surface area and water depth, density of rotifer and water depth, water depth and water temperature, respectively. The overall percentages of successful prediction varied from 56.5% to 67% utilizing leave-one-out for cross-validation tests.

Spatiotemporal patterns of catch and discards of the Israeli Mediterranean trawl fishery in the early 1990s: ecological and conservation perspectives

The spatiotemporal patterns of discards and catch composition of Israeli trawlers were examined using a 4-year (1990-1994), 324 haul dataset. Haul depth was found to be the main grouping variable for hauls, although significant seasonal differences were also found. 28.3% of the total catch was discarded, and there was a 40.1% discard percentage in shallow hauls. According to these figures, annual discards for the Israeli trawl fleet for the study period are estimated at ca. 440 to 700 t. Both the biomass and the number of discarded specimens peaked in summer, as well as the percentage of juvenile fish of commercial species. These findings suggest that a summer moratorium on trawling would reduce discards. The percentage of specimens of Indo-Pacific origin decreased from 51% in depths shallower than 37 m to 24% between 38 and 73 m, and 8% in deeper strata. Discards along the Israeli coast were comparable to those observed elsewhere in the Mediterranean. The findings presented here are the first quantitative account of fish community assemblages in the nearshore waters of the easternmost part of the Mediterranean, and thus provide valuable information for comparisons with more current datasets that are currently being assembled.

Effects of habitat heterogeneity at multiple spatial scales on fish community assembly

Habitat variability at multiple spatial scales may affect community structure within a given habitat patch, even within seemingly homogenous landscapes. In this context, we tested the importance of habitat variables at two spatial scales (patch and landscape) in driving fish community assembly using experimental artificial reefs constructed across a gradient of seagrass cover in a coastal bay of The Bahamas. We found that species richness and benthic fish abundance increased over time, but eventually reached an asymptote. The correlation between habitat variables and community structure strengthened over time, suggesting deterministic processes were detectable in community assembly. Abundance of benthic fishes, as well as overall community structure, were predicted by both patch- and landscape-scale variables, with the cover of seagrass at the landscape-scale emerging as the most important explanatory variable. Results of this study indicate that landscape features can drive differences in community assembly even within a general habitat type (i.e., within seagrass beds). A primary implication of this finding is that human activities driving changes in seagrass cover may cause significant shifts in faunal community structure well before complete losses of seagrass habitat.

INFLUENCES OF CANAL STRUCTURE AND CANAL CONNECTIVITY TO RIVER ON FISH COMMUNITY IN A SUBURBAN AREA

Fish community assemblages between earth canals and concrete canals were compared in a land consolidation area, Tokushima City, Japan. This survey recognized 17 genuine freshwater species in eight families in this area. However, differences of species composition, the number of species and population densities of several species between in the both types of canals were small. On the other hand, the population densities of several species showed inverse correlations with distances from survey canals to rivers. In addition, the canals without weirs or drop structures, which prevented migration of fishes, showed higher population densities than the canals with these barriers. These results demonstrate that connectivity to rivers is more important than canal structures for the fish community conservation in land consolidation areas.

Habitat Influence on Fish Community Assemblage in an Agricultural Landscape in Four East Central Indiana Streams

ABSTRACT The objective of this study was to relate the quality of the fish community with habitat using the Index of Biotic Integrity (IBI) and Qualitative Habitat Evaluation Index (QHEI) in four agriculturally influenced streams in east central, Indiana. A total of 48 species was collected from 42 sites. IBI scores ranged from 14 to 48, and QHEI scores ranged from 29 to 83. There was a significant positive correlation between IBI and QHEI scores. Furthermore, we found significant positive correlations between IBI scores and four individual QHEI metrics (channel morphology, substrate, poollglide and riffletrun quality, and in-stream cover). Habitat influenced the fish assemblages with channelization and substrate being the primary structuring factors. The land use in this area is 70% agriculture, which has heavily influenced lotic character through anthropogenic practices.

Fish assemblages on fringe coral reefs of the northern coast of Cuba near Havana Harbor

It is difficult to separate effects on fish community assemblages due to anthropogenic stressors from natural factors. We examined small-bodied-fish communities along the northern coast of Cuba near Havana Harbor during the dry (February/March of 2000) and wet (June 2000) seasons. Over 35,000 individual fish were visually counted at 15 sites along the coast in three areas located 0–2.4, 2.4–6.1, and 6.1–10.3 km from the entrance to Havana Harbor. Fish communities in four substrate biotopes did not vary significantly between wet and dry seasons, but did vary with water depth. Proximity to Havana Harbor was the second most important factor affecting fish assemblages, and sites closest to the harbor had reduced populations of the bluehead wrasse ( Thalassoma bifasciatum) and an increased abundance of slippery dick ( Halichoeres bivittatus). More studies are required at the population and individual levels to link stressors (e.g., contaminants, siltation) directly to observed effects.

Low-head Sea Lamprey Barrier Effects on Stream Habitat and Fish Communities in the Great Lakes Basin

Low-head barriers are used to block adult sea lamprey ( Petromyzon marinus) from upstream spawning habitat. However, these barriers may impact stream fish communities through restriction of fish movement and habitat alteration. During the summer of 1996, the fish community and habitat conditions in twenty-four stream pairs were sampled across the Great Lakes basin. Seven of these stream pairs were re-sampled in 1997. Each pair consisted of a barrier stream with a low-head barrier and a reference stream without a low-head barrier. On average, barrier streams were significantly deeper (df = 179, P = 0.0018) and wider (df = 179, P = 0.0236) than reference streams, but temperature and substrate were similar (df = 183, P = 0.9027; df = 179, P = 0.999). Barrier streams contained approximately four more fish species on average than reference streams. However, streams with lowhead barriers showed a greater upstream decline in species richness compared to reference streams with a net loss of 2.4 species. Barrier streams also showed a peak in richness directly downstream of the barriers, indicating that these barriers block fish movement upstream. Using Sørenson's similarity index (based on presence/absence), a comparison of fish community assemblages above and below low-head barriers was not significantly different than upstream and downstream sites on reference streams (n = 96, P > 0.05), implying they have relatively little effect on overall fish assemblage composition. Differences in the frequency of occurrence and abundance between barrier and reference streams was apparent for some species, suggesting their sensitivity to barriers.

Development and application of a predictive model of riverine fish community assemblages in the Taranaki region of the North Island, New Zealand

A predictive model of fish community composition using a reference condition approach is proposed for the Taranaki region of New Zealand. The model is used to quantify the effects of barriers on the migration of native fish in the region. Occurrence records of fish in streams without migratory barriers (reference sites) obtained from the New Zealand freshwater fish database were used to establish trajectories of occurrence for each of 12 fish species with altitude. The relative occurrence per site for each of the species was calculated and used as the probability of the presence of that species in that altitudinal range. Comparison of these probabilities with the fauna actually found at a test site expressed as an observed over predicted ratio (O/P) is then used to compare sites to quantify barrier effects on fish communities. In a similar way this process can be used to monitor the effectiveness of fish passes, where present on dams. Independent data from 85 sites sampled over the summer of 1997/98 were used to test the predictive model. As an example of a typical use of the methodology, the effect of a single hydrodam on fish communities is illustrated.

Populations and assemblages of parasites in hake, Merluccius gayi, from the southeastern Pacific Ocean: stock implications

To assess fish stocks, the populations and community assemblages of metazoan parasites were compared in 1172 Chilean hake Merluccius gayi landed at two major ports, and caught during 1991–1992 in three major fishing areas off central Chile. At least two ecological stocks are suggested, based on consistent differences in parasitism between body length classes for Grillotia dollfusi, Hysterothylacium sp., Clestobothrium crassiceps and Aporocotyle wilhelmi. More use should be made of the information on whole parasite assemblages including, for example, patterns of co‐occurrence of parasite species. Univariate analyses on selected taxa in samples from different areas may show no differences because of the same prevalence or abundance for each parasite taxon, but opposite numerical arrangements of co‐occurring taxa in community assemblages would remain undetected.

Interactions between stochastic and deterministic processes in stream fish community assembly

Numerous studies have attempted to determine whether stream fish communities are structured primarily by deterministic or stochastic processes. Previous work has assumed that stream fish communities will show either persistence about an equilibrium because of strong density-dependent processes or random variation in structure as a result of environmental stochasticity. In a 10-year study of a California stream, fish community structure changed under the influence of storm-induced high discharge events that impacted recruitment. Species' relative abundances were altered as pre-recruitment stream discharges differentially influenced year-class strength among species with contrasting life histories. Simulation of stream fish community assembly under flow-driven recruitment variation indicates that community structure will vary depending on how particular high-flow events affect species' relative abundances and ongoing density-dependent processes, including competition and predation. Results suggest that stream fish communities are likely to show alternate states rather than a single persistent equilibrium. However, community assembly will not be random but will depend on situation-specific interactions between density-independent and density-dependent processes.

Description of the subareas of Ragay Gulf, Philippines, and their fish assemblages by exploratory data analysis

Exploratory data analysis using four different techniques of classification and ordination was applied to the catch data from a 15-month demersal trawl survey in Ragay Gulf, Philippines, in order to characterize the area. The four techniques yield almost identical results and therefore lend confidence to the three subareas identified: shallow, coralline and deep. Species characteristic of the subareas were also identified. The observed pattern remained consistent during the study period, suggesting that seasonal variability is not pronounced. This study provides further empirical evidence of the zonation of fish communities by depth. Preliminary comparison of the results of this study with those of studies of demersal fish community assemblages in the Samar Sea shows that boundary depths defining zonation are different in the two areas because of their different depth ranges and spatial scales. This comparison leads to the question of whether the boundary depths as identified via classification and ordination methods could be a function of the shape of the depth distribution of the samples. The use of a bootstrapping method to investigate this question is suggested. The importance of applying exploratory data analysis to the catch data from a demersal trawl survey done to assess fish stocks is also discussed.

Stochasticity and Assemblage Organization in an Indiana Stream Fish Assemblage

Site d'etude: zone situee sous le barrage de Markles; problemes d'echantillonnage; nombre d'especes incluses dans l'analyse. Inclusion des jeunes d'un an dans cette analyse; interpretation et nouvelle analyse des modeles alternatifs

Stochasticity in Stream Fish Communities: An Alternative Interpretation

Stochasticity in Stream Fish Communities: An Alternative Interpretation