In Arctic ecosystems, freshwater fish migrateseasonally between productive shallow water habitatsthat freeze in winter and deep overwinter refuge in riversand lakes. How these movements relate to seasonal hydrologyis not well understood.We used passive integratedtransponder tags and stream wide antennae to track1035 Arctic grayling in Crea Creek, a seasonally flowingbeaded stream on the Arctic Coastal Plain, Alaska. Migrationof juvenile and adult fish into Crea Creek peakedin June immediately after ice break-up in the stream. Fishthat entered the stream during periods of high flow andcold stream temperature traveled farther upstream thanthose entering during periods of lower flow and warmertemperature. We used generalized linear models to relatemigration of adult and juvenile fish out of Crea Creek tohydrology.Most adults migrated in late June – early July,and there was best support (Akaike weight = 0.46; wi) fora model indicating that the rate of migration increasedwith decreasing discharge. Juvenilemigration occurred intwo peaks; the early peak consisted of larger juvenilesand coincided with adult migration, while the laterpeak occurred shortly before freeze-up in Septemberand included smaller juveniles. A model that includeddischarge, minimum stream temperature, year, season,and mean size of potential migrants was most stronglysupported (wi = 0.86). Juvenile migration rateincreased sharply as daily minimum stream temperaturedecreased, suggesting fish respond to impendingfreeze-up. We found fish movements to be intimatelytied to the strong seasonality of discharge and temperature,and demonstrate the importance of smallstream connectivity for migratory Arctic grayling duringthe entire open-water period. The ongoing andanticipated effects of climate change and petroleumdevelopment on Arctic hydrology (e.g. reduced streamconnectivity, earlier peak flows, increased evapotranspiration)have important implications for Arctic freshwaterecosystems.
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