Relative Abundance, Length Frequency, Age, and Maturity of Dolly Varden in Nearshore Waters of the Arctic National Wildlife Refuge, Alaska

Uncertainty about the environmental effects of oil development prompted a study of Dolly Varden Salvelinus malma in the nearshore waters of the Arctic National Wildlife Refuge, Alaska. Abundance of fish less than 400 mm fork length (FL), as indexed by tyke net catch per unit effort (CPUE), was significantly different among years, with the highest daily catch rates occurring in 1991, a year of heavy pack ice and relatively cold water temperatures. The CPUE for fish 400 mm or greater did not differ significantly among years. Within each sampling year, both large and small fish appeared to be more abundant in nearshore waters earlier in the summer. Lengths ranged from 53 to 734 mm. Growth was greater early in the season and in the years 1989 and 1990, and site-specific temporal changes in distribution were reflected in analysis of length data. Individual fish were aged at 1–13 years. A gonadosomatic index indicated that sexually mature fish were greater than 400 mm FL. Wide summer dispersal makes Dolly Varden less vulnerable to local coastal perturbations during the summer; however, vulnerability may be greater for stocks that must migrate seasonally through particular areas (e.g., a river mouth during fall migrations). The significant differences in local abundance patterns makes effective monitoring of the overall population size difficult. Monitoring spawners or overwintering fish in freshwater may be a more accurate means of assessing overall abundance trends.