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Fish Surveys (fish + survey)
Selected AbstractsInvestigating the link between pulp mill effluent and endocrine disruption: Attempts to explain the presence of intersex fish in the Wabigoon River, Ontario, CanadaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2010Michael S. Pollock Abstract The ability of some pulp mill effluents (PME) to act as reproductive and endocrine disrupters in fish is well documented in the literature. However, changes are not always consistent with regard to species, gender, hormones, or reproductive effects. In the present study, the presence of the first intersexed fish that, to our knowledge, has been found in a Canadian river exposed to PME, is reported. A field survey of the Wabigoon River near Dryden, Ontario, in the fall of 2000 found intersexed walleye (Sander vitreus vitreus) with significantly altered hormone levels and reduced gonad size. The Wabigoon River receives discharge from a bleached kraft pulp and paper mill and a municipal wastewater (MWW) plant. It also has historical sediment contamination (wood fiber mats) contributing to extended periods of low dissolved oxygen under low flow, drought conditions. A mesocosm-based partial life cycle test exposing fathead minnows (Pimephales promelas) to reference water, 20% effluent volume to river volume (v/v), 40% (v/v), or 60% (v/v) PME as well as a field survey of the walleye in the Wabigoon River were conducted. The only change in our mesocosm exposure was a decrease in testosterone in males with increasing effluent concentration and vitellogenin induction in males exposed to 60% (v/v) effluent. These results did not reflect the magnitude of endocrine disruption seen in the wild fish survey. Several hypotheses that may explain these discrepancies are proposed. Specifically, evidence is offered from published studies indicating that either hypoxia or MWW, alone or in combination with PME, may explain the discrepancy between our field experiment and the wild fish survey. The present study illustrates the complexities of multistressor receiving environments and the need for the development of cumulative effects assessment approaches. Environ. Toxicol. Chem. 2010;29:952,965. © 2010 SETAC [source] Spatial distribution and overlap between ichthyoplankton and pelagic fish and squids on the southern flank of Georges BankFISHERIES OCEANOGRAPHY, Issue 5 2002Lance P. Garrison Abstract We conducted larval and adult fish surveys on the southern flank of Georges Bank during the spring of two years (1990 and 1995) with contrasting physical conditions. We employed canonical correspondence analysis (CCA) to examine the relationships between physical variables and the spatial distribution of pelagic fish and ichthyoplankton. Surface temperature bottom temperature, and vertical stratification were significant factors affecting larval fish distributions, and there were groups of species with similar responses to these variables. There were also consistent relationships between physical variables and pelagic fish and squid abundances and spatial distributions. Pelagic fish and ichthyoplankton with similar responses to hydrographic variables had high spatial overlap, and variation in hydrographic regimes modulated the strength of this interaction. Pelagic fish and squids are potentially important predators of both larval and juvenile fish on Georges Bank. Hydrographic structure modulates the degree of spatial overlap and therefore likely influences the strength of predator,prey interactions. [source] Fish community comparisons along environmental gradients in lakes of France and north-east USAGLOBAL ECOLOGY, Issue 3 2007Pascal Irz ABSTRACT Aim, To assess whether eight traits of fish communities (species richness, three reproductive traits and four trophic traits) respond similarly to environmental gradients, and consequently display convergence between the lakes of France and north-east USA (NEUSA). Location, 75 French and 168 north-east USA lakes. Methods, The data encompass fish surveys, the assignment of species into reproductive and trophic guilds, and environmental variables characterizing the lakes and their catchments. The analytical procedure was adapted from the recommendations of Schluter (1986) [Ecology, 67, 1073,1085]. Results, The comparison of the regional pools of lacustrine fishes indicated that NEUSA was about twice as speciose as France, mostly due to higher species turnover across lakes, although NEUSA lakes were consistently about 20% more speciose than French lakes for a given surface area. Warmer environments were consistently inhabited by a higher proportion of phytophilous and guarder species than were colder lakes. Hence there was convergence in community reproductive traits. Conversely, there was no evidence of convergence in the trophic structure of lacustrine fish communities between regions. Main conclusions, The influence of temperature on the availability and quality of spawning substrates appears to be a major constraint on present-day lacustrine fish communities. In parallel, phylogenetic constraints, past events such as the diversification of the North American fish fauna, and selective extinctions during Pleistocene glaciations and subsequent recolonizations contribute to explaining the dissimilarities between the communities of the two regions and differences in their relationship to the environment. [source] Mixed stream channel morphologies: implications for fish community diversityAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 2 2009Christina M. Cianfrani Abstract 1.Stream classification systems are widely used in stream management and restoration. Whereas the principal morphological types of these classification systems are increasingly recognized for their ecological connections, the roles of intermediate and mixed morphologies are still poorly understood, yet may be biologically significant. 2.Twenty-five stream reaches in north-western Vermont were classified by channel morphology to determine whether fish community diversity differed among pool-riffle, mixed (i.e. pool-riffle/cascade, pool-riffle/other) and forced pool-riffle stream morphological groups. Stream reach surveys included cross-sectional surveys, longitudinal profiles, bed substrate characterization, and fish surveys. 3.Three fish community diversity measures were calculated: (1) species richness (S); (2) Shannon,Weaver Index (H,); and (3) Simpson's Index (1/D). Multivariate analysis of covariance (MANCOVA) followed by analysis of variance (ANOVA) were used to explore potential differences in fish diversity among stream morphological groups. Fish diversity was significantly different for all three community diversity measures (P,0.05), with pool-riffle/cascade morphology consistently exhibiting the greatest fish diversity and forced pool-riffle the lowest. 4.These results suggest that fish community diversity is significantly associated with distinct channel morphologies. Generally, pool-riffle/cascade and pool-riffle/other stream morphological groups supported habitats that fostered greater species diversity than more homogeneous and uniform pool-riffle reaches. The observed patterns of diversity are likely to be the result of habitat patches created by variations in flow and other physical characteristics in reaches of mixed morphologies. 5.These results support fish sampling schemes that incorporate morphological heterogeneity, such as proportional-distance designation. Sampling strategies that focus on homogeneous reaches may underestimate diversity, and misrepresent stream condition when fish community data are used in indices of biological integrity (IBIs). Reaches of mixed stream morphologies should be recognized as areas of biological importance in stream and catchment management and in conservation efforts. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||