The effects of tertiary treated municipal wastewater on fish communities of a small river tributary in Southern Ontario, Canada

Fish community changes associated with a tertiary treated municipal wastewater effluent outfall in the Speed River, Ontario, Canada, were evaluated at nine sites over two seasons (2008) using standardized electrofishing. Habitat evaluations were conducted to ensure that the riffle sites selected were physically similar. The fish community was dominated by several species of darters that differed in their response to the effluent outfall. There was a significant decrease in Greenside Darter (Etheostoma blennioides) but an increase in Rainbow Darter (E. caeruleum) abundance directly downstream of the outfall. Stable isotope signatures (δ¹³C and δ¹⁵N), which indicate shifts in energy utilization and flow, increased in Rainbow Darter downstream, but showed no change in Greenside Darter. Rainbow Darter may be exploiting a food source that is not as available at upstream sites giving them a competitive advantage over the Greenside Darter immediately downstream of the outfall.     

Temperate marine reserves enhance targeted but not untargeted fishes in multiple no-take MPAs.

Although many papers report the effects of no-take marine protected areas (MPAs or reserves), scientifically rigorous empirical studies are rare, particularly for temperate reef fishes. We evaluated the responses of fish populations to protection from fishing in reserves by comparing densities and sizes inside and outside of five no-take reserves in southern California, USA. Our results are robust because we compared responses across multiple rocky-reef reserves in two different years and controlled for possible site differences by (a) ensuring that habitat characteristics were the same inside and outside reserves, and (b) sampling species that are not targeted, which would not be expected to have a direct response to fishing. We compared fish density and size and calculated biomass and egg production across all five sites. Fishes targeted by recreational and/or commercial fisheries consistently exhibited increases in mean density (150%), size (30%), biomass (440%), and egg production (730%) inside reserves. Reserve effects were greatest for legal-sized targeted fishes: significantly greater densities were found exclusively inside reserves for targeted species (580%), the largest size classes existed only inside reserves, and mean biomass was 1000% higher. These responses were unlikely to have been caused by habitat differences because there were no significant differences in habitat characteristics between reserve and control locations. Densities of non-targeted species did not differ between reserve and non-reserve locations, further supporting the conclusions that differences in targeted species between reserve and control locations were due to harvesting rather than site-specific effects. Although MPAs cannot replace traditional fisheries management, the concentration of increased biomass and egg production is a unique MPA benefit that serves both reserves and fisheries. Scientifically rigorous studies that include multiple reserves, such as this study, are needed to inform management and policy decisions.     

邻近油砂活动的鱼类性能指标：对邻近油砂开采活动的阿尔伯塔省Steepbank河中粘杜父鱼性能指标的响应

自2009年以来，加拿大和阿尔伯塔省政府一直在制定Athabasca河下游及其支流（2010-2013年）地表水质量和水量的监测计划。这项对鱼类监测计划的贡献的目标是1）评估该河支流中鱼类的当前状态，2）识别上游参考物和油砂沉积物暴露位点之间存在的差异，和3）识别鱼类性能指标相对于历史研究的趋势和变化。本研究考察了阿尔伯塔省Steepbank河中粘杜父鱼（Cottus cognatus）在生长、性腺大小、生长状况和肝脏7-乙氧基甲氧基甲酰胺基脱氢酶（EROD）活性方面的鱼类性能指标，以此作为暴露于油砂相关化合物的指标。采样程序遵循历史采样方法（1999-2000年），随着开发的进展，随着时间的推移提供可比数据，同时增加一个上游参考位点（n=2）。2010年至2013年，从油砂矿床（n=2）内的Steepbank河下游收集的杜父鱼中记录到了一致的变化。杜父鱼的数据显示，肝脏增大的同时相应的EROD活性诱导与历史数据一致，与生殖发育和性腺类固醇生产能力相关的能量投资减少。没有一致的证据表明，随着露天采矿开发的增加使得鱼类性能指标发生了变化，特别是在Steepbank河中段附近。尽管在过去15年里，Steepbank河流域的物理开发有所增加，但这些结果与历史数据一致，表明开发区附近的水环境的响应程度没有改变。     

Fishing the line near marine reserves in single and multispecies fisheries.

Throughout the world "fishing the line" is a frequent harvesting tactic in communities where no-take marine reserves are designated. This practice of concentrating fishing effort at the boundary of a marine reserve is predicated upon the principle of spillover, the net export of stock from the marine reserve to the surrounding unprotected waters. We explore the consequences and optimality of fishing the line using a spatially explicit theoretical model. We show that fishing the line: (1) is part of the optimal effort distribution near no-take marine reserves with mobile species regardless of the cooperation level among harvesters; (2) has a significant impact on the spatial patterns of catch per unit effort (CPUE) and fish density both within and outside of the reserve; and (3) can enhance total population size and catch simultaneously under a limited set of conditions for overexploited populations. Additionally, we explore the consequences of basing the spatial distribution of fishing effort for a multispecies fishery upon the optimality of the most mobile species that exhibits the greatest spillover. Our results show that the intensity of effort allocated to fishing the line should instead be based upon more intermediate rates of mobility within the targeted community. We conclude with a comparison between model predictions and empirical findings from a density gradient study of two important game fish in the vicinity of a no-take marine-life refuge on Santa Catalina Island, California (USA). These results reveal the need for empirical studies to account for harvester behavior and suggest that the implications of spatial discontinuities such as fishing the line should be incorporated into marine-reserve design.