Status of rainbow trout in the Goodnews River, Togiak National Wildlife Refuge, Alaska 1988-1989

Irving, David; Faustini, Mary

The population characteristics of rainbow trout (Oncorhynchus mykiss) in the Goodnews River on the Togiak National Wildlife Refuge (Refuge) were studied from June through September, 1988 and 1989. The study objectives were to: (1) describe length, weight, age, and sex composition of rainbow trout; (2) estimate the annual survival rate of each year class of rainbow trout vulnerable to the sport fishery; (3) estimate seasonal sport fishing catch rates of rainbow trout; (4) evaluate scale versus otolith ageing methods; (5) compare rainbow trout population characteristics with other southwest Alaska stocks; and (6) describe length and weight data of Dolly Varden and Arctic Char (Salvelinus sp.) and Arctic grayling (Thymallus arcticus). Three hundred and eighty-seven rainbow trout were captured using hook and line, minnow traps, and electrofishing. Lengths ranged from 27-686 mm and weights from 1-2,550 g. Otolith ages ranged from 0-11 years and scale ages ranged from 0-8 years. The female to male sex ratio was 1:2.04. Comparisons between scale and otolith aged rainbow trout revealed that scale ages underestimated the otolith age by 1-3 years for fish 3 years and older. The Goodnews fish populations were compared to those of the Kanektok River. More large rainbow trout were caught in the Goodnews River than in the Kanektok River. Goodnews River rainbow trout also exhibited larger length at age than fish from the Kanektok River. However, creel survey data revealed that catch rates of rainbow trout from the Goodnews River were one-third that of the Kanektok River. Based on catch data, the population probably does not have the capacity to support large increases in fishing pressure without suffering a decrease in the size composition. One hundred and seventy-five Salvelinus sp. and 130 Arctic grayling were also sampled. Salvelinus sp. lengths and weights ranged from 278-629 mm and 225-2,825 g, and Arctic grayling ranged from 275-510 mm and 250-1,550 g, respectively. These species were found to be slightly larger than other Arctic grayling and Salvelinus sp. populations in southwestern Alaska. We recommend continued monitoring of the sport fishery through the Refuge's Special Use Permits and public use surveys; that the resident fish populations be sampled again in five years to note any changes in size composition; and that a conservative approach be practiced in management of the Goodnews River rainbow trout population.