Site fidelity of slimy sculpin (Cottus cognatus): insights from stable carbon and nitrogen analysis

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 δ 15 N 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 15 N in sculpin collected in the agricultural region. However, there was an incremental enrichment in the fish muscle tissue of approximately 5‰ in δ 13 C 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.