Concerns regarding sentinel species for assessing environmental impacts include residency, abundance, and suitability for measuring responses, if effects are to be attributable to local conditions. Stable isotope analysis was used as a tool to investigate site fidelity of slimy sculpin (Cottus cognatus) to establish residency and exposure for the sculpin. We predicted that sculpin collected from sites adjacent to agricultural activity would show higher δ15N values than those collected from sites in forested areas because of isotopic enrichment by fertilizers in the former. The predominant use of chemical fertilizer applications in the region, however, resulted in no specific enrichment of 15N in sculpin collected in the agricultural region. However, there was an incremental enrichment in the fish muscle tissue of approximately 5‰ in δ13C values in a downstream direction, irrespective of surrounding land use. As a result, the dual-isotope comparison was successful at demonstrating site-specific isotopic signatures across sites for 30 km of the river system. The site-specific signatures suggest that slimy sculpin are not moving considerable distances among sites and are incorporating their isotopic signatures over a narrow spatial scale. The results support the use of the slimy sculpin as a sentinel species for investigating site-specific environmental impacts.

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Smolt characteristics such as lipid-moisture dynamics, ATPase activity, salinity tolerance, and condition factor were determined for Atlantic salmon parr (Salmo salar) moving to, or residing in, estuaries of two rivers in eastern Canada. Lipid and water content and gill Na+K+-ATPase activity of these parr differed markedly from river-resident parr. ATPase activity, sex ratio, and condition factor indicated more similarity between estuarine parr and smolts. Estuarine parr were unable to tolerate high salinities in spring, summer, or autumn, but there was an indication of an autumnal increase in salinity tolerance which coincided with maximum levels in ATPase activity and a secondary downstream movement of parr and smolt-like salmon in the autumn. The data suggest that the largest estuarine parr are essentially presmolts which utilize the estuary as a rearing environment prior to subsequent emigration seaward when environmental conditions are again amenable to a reopening of the 'smolt window.' These observations also highlight some inadequacies in applying existing criteria for the smoking process and for modelling life histories of salmonids.

Slimy sculpin (Cottus cognatus) are increasingly being used as indicator species. This has primarily entailed measuring their condition, the assumption being that condition can be used as a surrogate for lipid content. While there is evidence to suggest this assumption is applicable to some fish, it has yet to be validated for C. cognatus. Further, there are several means by which one may calculate condition, the most commonly employed of which are indirect measurements of lipid content (namely, Fulton's K, somatic K (Ks), and Le Cren's relative condition factor (Kn)). We compared the ability of each of these morphometric indices to predict whole-body lipid content in C. cognatus. There was a moderate degree of evidence that Fulton's K, Ks, and Kn are reliable predictors (Ks and Kn in particular). Of the latter we recommend Kn be used because, unlike Ks, it does not require that fish be killed. And while Fulton's K did not perform quite as well, we consider it a sufficient substitute if the data necessary to calculate Kn are unavailable.

RESUMEN: NSERC's HydroNet es un programa nacional colaborativo de investigación a cinco años que inició en el año 2010 e involucra a los sectores académico, gubernamental e industrial. El objetivo general de HydroNet es comprender los efectos que tienen las operaciones hidroeléctricas en los ecosistemas acuáticos y ofrecer herramientas científicas defendibles y transparentes tendientes a mejorar los procesos en la toma de decisiones que están asociados al uso de la energía hidroeléctrica. Diversos proyectos se encuentran insertos en tres grandes tópicos: 1) análisis ecosistémico de la capacidad productiva de los Modelación de meso-escala de la capacidad productiva de los hábitats para peces en lagos y embalses, y 3) predicción del riesgo de arrastre de peces hacia los embalses hidroeléctricos, en función del poder generador de las operaciones, combinando la ecología conductual y la ingeniería hidráulica. El conocimiento generado por HydroNet es fundamental para evaluar el balance entre la demanda por recursos hídricos limitados, para asegurar que la energía hidroeléctrica sea sustentable, que promueva la salud de los ecosistemas acuáticos así como también a la pujante economía canadiense. ABSTRACT: NSERC's HydroNet is a collaborative national fiveyear research program initiated in 2010 involving academic, government, and industry partners. The overarching goal of HydroNet isto improve the understanding of the effects of hydropower operations on aquatic ecosystems, and to provide scientifically defensible and transparent tools to improve the decision-making process associated with hydropower operations. Multiple projects are imbedded under three themes: 1) Ecosystemic analysis of productive capacity of fish habitats (PCFH) in rivers, 2) Mesoscale modelling of the productive capacity of fish habitats in lakes and reservoirs, and 3) Predicting the entrainment risk of fish in hydropower reservoirs relative to power generation operations by combining behavioral ecology and hydraulic engineering. The knowledge generated by HydroNet is essential to balance the competing demands for limited water resources and to ensure that hydropower is sustainable, maintains healthy aquatic ecosystems and a vibrant Canadian economy.