Summary

Description

All National Wildlife Refuges in Alaska except Kenai include continued use for subsistence activities as a defined refuge purpose under the Alaska National Interest Lands Conservation Act. Contaminant burdens in fish and wildlife species used for subsistence can limit or preclude the continued opportunity for traditional subsistence activities on these refuges. Northern pike Esox lucius are heavily used subsistence foods on NWRs in Alaska, and have mercury concentrations that often exceed critical values for human consumption. However, few NWR managers in Alaska have data sets on mercury in pike and other fish that would allow them to manage for continued subsistence uses and to mitigate hazards from consumption of those fish. To address this lack of data, we conducted a multiyear, systematic sampling for mercury and methylmercury in northern pike on the largest refuges in western and interior Alaska: Yukon Delta, Selawik, Koyukuk, Nowitna, Innoko and Yukon Flats NWRs. From 2005 2007, we collected 440 northern pike from these Refuges, in six major watersheds. Sample sites were traditional and wellused subsistence fishing locations, identified by local residents. Pike were collected during the time of year that they were normally collected for subsistence purposes, either in the spring caught through the ice during spawning migration or summer caught in open water, postspawning. Fish were necropsied and an approximately 10 g muscle sample was analyzed for mercury. Methyl mercury was analyzed in about a third of all samples. Mercury and methyl mercury were correlated in fish muscle, allowing calculation of a robust MeHg:THg ratio 0.96. Mercury was also correlated with fish length. We compared average calculated based on the MeHg:THg ratio methyl mercury concentrations from Refuges and watersheds to State consumption advisory values for mercury and found that some consumption advice was warranted, especially on the lower Yukon River in the Yukon Delta NWR. Mercury concentrations in pike muscle were of no apparent concern for fish health. These data will help Refuge managers provide continued subsistence opportunities and mitigate potential hazards associated with mercury in northern pike, a commonly used subsistence food. These data can also be used as baseline biomonitoring data for NWRs in Alaska, as mercury deposition, mobilization, and transport is likely to increase in light of increasing industrialization upwind of Alaska and in response to climate change.