Inter-annual fidelity to summer feeding sites in Arctic grayling

Inter-annual fidelity to summer feeding sites was assessed in adult Arctic grayling, Thymallus arcticus, in the Kuparuk River, Alaska using long-term (15 years) records of individually tagged fish. The Kuparuk River has been the site of a long-term fertilization experiment which allowed us to evaluate the effects of habitat quality on site fidelity. Fidelity to the entire 5 km experimental reach, the reference or fertilized zone of the river and to specific river locations was examined. On average, 32% of the arctic grayling caught in the experimental reach were recaptured within the reach in subsequent years. Grayling that returned to the reach displayed strong fidelity to river zones as well as to specific sites on the river. More than half of the fish were recaptured within 300 meters of the site where they were captured in previous years. There was no significant difference in fidelity to either the reference or the more productive fertilized zone. Unexpectedly, fidelity was unrelated to fish size (29-43 cm TL) or previous summer's growth. Strong site fidelity appears to be an adaptation to a short summer during which sufficient resources must be acquired to sustain the fish through the long (9 month) Arctic winter leaving little time to explore alternative locations.