Linking North Slope Climate, Hydrology, and Fish Migration

Fish and wildlife species in the Arctic have developed life history strategies to deal with the extreme climate of the North. In the case of Arctic grayling, these strategies include long life, yearly spawning, and migration. In order to understand how such a species will be affected by a changing climate, we must determine how these adaptive strategies may be at odds with the changing Arctic landscape. Arctic grayling migrate in the spring and early summer to spawning and feeding sites and then in the fall migrate back to overwintering sites. Migration to spawning sites occurs just after break up when rivers are quite swollen from the melting of an entire winter’s worth of snow. Low precipitation and high evapotranspiration rates early in the summer can lead to low water levels and a fragmentation of the hydrologic landscape. This fragmentation creates a barrier to fish migration. As the summer progresses, precipitation tends to increase and evapotranspiration decreases. Hydrologic connectivity is generally restored by the end of summer and soils are wet prior to freeze-up. Increased temperatures associated with climate change lead to greater evapotranspiration. This may lead to increased drying in the summer in the Arctic. Although annual precipitation rates are expected to increase, the direction and magnitude of the change in summer precipitation is less clear. Another possible change in precipitation may be in the form of increased variability or in the probability of extreme events. The research to be presented here details an attempt to recreate the occurrence of hydrologic barriers to fish migration in the Upper Kuparuk River on the North Slope of Alaska. Locations along the Upper Kuparuk which become barriers to migration during low flows were identified and monitored during the summer of 2010. These locations were chosen because during previous low flow events, these stretches run dry even though water is seen flowing both up and downstream of these stream segments. Although not fully understood yet, the geomorphological conditions along these stream segments are such that the flow becomes 100% hyporheic during periods of low flow. The data collected at these locations over the summer is then compared to 15 years worth of discharge data collected in the Upper Kuparuk to determine when, how often, and under what conditions these barriers have occurred. This is the first step in an ongoing research effort to predict how future changes in the hydrologic regime of the Arctic may affect Arctic grayling. Migration of Arctic grayling provides a useful mechanism of study as most arctic fish species migrate between or within streams, rivers, lakes, wetlands and coastal waters during some period in their life cycle. Although this research aims to help answer whether barriers to fish migration are occurring frequently enough to create an impact on Arctic grayling, an increase in the formation of these barriers has the potential to affect all fish utilizing these same migration routes.