• hemp3quilt posted an update 1 week, 4 days ago

    Future surveys to assess potential anthropogenic disturbances in one specific area could be confounded if fluctuations in environmental conditions across time and space are not taken into consideration. The effect of Study Area became insignificant after adding environmental variables, thus providing evidence that the most important environmental gradients affecting the fish community were among those we measured, i.e., Depth, Bottom temperature, Bottom salinity, Percent gravel, Percent mud, Latitude, Longitude, and Distance offshore. Measuring Alisertib ic50 and including these environmental variables in future investigations of potential disturbance will control for their confounding fluctuations across space and increase the power of any future before-after-control-impact (BACI) analyses designed to assess the suspected effects of a disturbance ( Smith, 2002). The observed changes in the fish communities across two years are problematic for assessing the potential effects of anthropogenic disturbance. This temporal variability will hinder the power of a BACI analysis if insufficient before and after years are sampled in relation to the suspected disturbance. Consistent use of one type of trawl that targets the appropriate size-spectra of fish would eliminate an important source of variation, the only one over which researchers have control. This study shows small-scale spatial differences in fish communities in the northeastern Chukchi Sea. Contrary to our initial expectation, we were able to document heterogeneity in species richness, density and assemblage structure. Additionally indicator species from five dominant fish families are not similarly or uniformly distributed across the three study areas. The higher fish richness and density are explained by salinity, temperature, percent gravel and percent mud of the more southerly area. These physical characteristics of the area explain the erosional nature that influences the fish. The importance of this conclusion is to emphasize the inclusion of measurement of physical characteristics in all studies to control for their confounding fluctuations across even small spatial scales. The type of net used to capture the fish can be confounding and must also be considered. Though larger fishes were not collected by the small nets used, most were <150 mm and are likely representative of the demersal fishes of the northeastern Chukchi Sea. Consistent collection methods for fishes and physical measurements are required now to detect future effects of a suspected climatological or anthropological disturbance. We thank ConocoPhillips, Shell Exploration and Production Co., and Statoil USA E&P for funding this research.