Stock Origins of Dolly Varden Collected from Beaufort Sea Coastal Sites of Arctic Alaska and Canada

—Anadromous northern Dolly Varden Salvelinus malma support a summer subsistence fishery in Beaufort Sea coastal waters. These same waters coincide with areas of oil and gas exploration and development. The purpose of this study was to assess variation in stock origins of Dolly Varden collected from sites along 400 km of Beaufort Sea coast. Mixed-stock analyses (MSA) of allozyme data were used to compare collections from four sites (Endicott near Prudhoe Bay, Mikkelsen Bay, and Kaktovik in Alaska and Phillips Bay in Canada) and to assess variation in stock contributions among summer months and between 1987 and 1988. The MSA estimates for individual stocks were summed into estimates for three stock groups: western stocks from the area near Sagavarnirktok River and Prudhoe Bay (SAG), Arctic National Wildlife Refuge stocks (Arctic Refuge), and Canadian stocks. The MSA of Endicott samples taken in 1987 and 1988 did not differ among months in terms of contributions from local SAG stocks (range, 71–95%). Contributions from nonlocal (.100 km distant) Canadian and Arctic Refuge stocks were not different from zero in 1987, but contributions from Canadian stocks were so in July (17%) and August (20%) but not in September of 1988. Thus, stock contributions to Endicott collections were different between 1987 and 1988. Samples from the Kaktovik area in 1988 were different between months in terms of contributions from nonlocal SAG stocks (July, 7%; August, 27%). Significant contributions to these samples were made both months by Canadian (25% and 17%) and local Arctic Refuge stocks (68% and 56%). Among the four coastal sites, local stocks typically contributed most to collections; however, every site had collections that contained significant contributions from nonlocal stocks. The MSA estimates clearly revealed the movement of Dolly Varden between U.S. and Canada coastal waters. If local stocks are affected by oil and gas development activities, distant subsistence fisheries along the coast could also be affected. Dolly Varden Salvelinus malma (herein also referred to as char) use the coastal waters of the Beaufort Sea during summer months to access food resources essential for growth and reproduction. Most Dolly Varden growth occurs in the short summer season when food items, such as mysids and amphipods, concentrate in the highly productive marine waters (Craig 1984; Fechhelm et al. 1997). These fish return to North Slope streams in * Corresponding author: [email protected] 1 Present address: National Marine Fisheries Service, Alaska Fisheries Science Center, Auke Bay Laboratory, 11305 Glacier Highway, Juneau, Alaska 99801–8626, USA. 2 Deceased. Received November 28, 1998 Accepted May 4, 1998 late summer to escape lethal winter sea temperatures and to overwinter in deep pools or springs (Reynolds 1997). Some large fish (.400 mm, about age 6 or 7) at this time also mature and spawn (McCart 1980; Underwood et al. 1996). Eggs incubate for 7–8 months before young emerge in the spring. Young Dolly Varden smolt in early summer, sometimes as young as age 1, but more commonly as age-3 or age-4 fish (Armstrong and Morrow 1980; McCart 1980). The overwintering habitats used by char in this region are scarce and represent ‘‘critical’’ habitat for the species. In the winter, fish cannot move between pools or out of springs because channels freeze to the stream bottom. Char must use these locations to survive and are held captive in them until spring breakup (Craig 1989a). Any oil and gas exploraD ow nl oa de d by [ M ic hi ga n St at e U ni ve rs ity ] at 0 6: 03 0 7 Fe br ua ry 2 01 4