State Water Resources Research Institute Program
Project Id: 2010AK93B
Title: Characterization of major watersheds draining into Bristol Bay, Alaska using strontium isotopes: a new method for tracking water resources in Alaska
Project Type: Research
Start Date: 3/01/2010
End Date: 2/28/2011
Congressional District: AK-001
Focus Categories: Hydrogeochemistry, Water Use, Methods
Keywords: Isotopes, Strontium, Alaska, Rivers.
Principal Investigator: Wooller, Matthew John
Federal Funds: $ 20,536
Non-Federal Matching Funds: $ 6,477
Abstract: We propose developing an approach for tracking the use of rivers and streams by salmon. Many of the rivers of Alaska, such as Yukon, Kuskokwim and those flowing into Bristol Bay (Kvichak and Nushagak), support active salmon populations. Salmon use the freshwater resources in rivers and the lakes attached to these rivers as the locations to breed before returning again to the ocean. Salmon frequently return to the same rivers and streams, which means that river-specific populations exist. However, once salmon return to the ocean it is very difficult to tell the different populations apart and to determine which freshwater resources (rivers, streams and lakes) are important to which salmon populations. A State need exists to determine the relative importance of different freshwaters resources in Alaska in terms of the salmon that return to them each year. A State need also exists to be able to tell different salmon populations apart in the ocean, as this is where human activities can have dramatic influences. One of these activities includes catching salmon as bycatch, which is an unfortunate consequence of trawling for other fish species in the ocean (e.g. Pollock). We propose conducting fieldwork to collect salmon and water from Nushagak river, which flows into Bristol Bay, Alaska. We will compile these samples with water and salmon we already have collected from the George, Andrafsky, Yukon, Kuskokwim, Kvichak (supplied to us by our collaborators). We propose measuring the strontium isotope composition of these samples to determine if water and salmon can be used to differentiate salmon in terms of their strontium isotope ratios (87Sr/86Sr) and subsequently pinpoint the identity of the freshwater resources used by these different salmon populations. The strontium isotope composition of a river is dictated by the strontium isotope composition of the geology in the river's basin. Variation in the geology of different watersheds results in rivers and streams with very different strontium isotope ratios. Preliminary strontium isotope data (supplied to us by our collaborator Dr. Naidu) from water samples collected at the mouths of our six study rivers show that they have different strontium isotope compositions. Organisms that have lived in these different waters will have strontium isotope compositions that reflect the strontium isotope compositions of the river waters. This is a particularly useful hydro-geo-bio chemical relationship for tracking fish back to the river that they originated from. Salmon have ear bones (otoliths) that grow incrementally, like tree rings. By measuring the strontium isotope composition of the earliest rings in a salmon's otolith it is possible to determine the likely river of origin. This relationship relies on a base map of river strontium isotopes compositions. The approach of mapping strontium isotope values in different rivers and relating this to values in salmon otoliths is actually well established in the literature and has been applied in other parts of the world that have rivers supporting salmon runs. However, this approach has not been widely applied in Alaska. This is partly because there have been insufficient measurements of the strontium isotope composition of waters from rivers and streams in Alaska. Our study will generate strontium isotope compositions for waters from six major rivers that open into the Eastern Bering Sea and are major birth and rearing rivers of salmon. All of the funds in this proposal are dedicated to supporting fieldwork and research to be conducted by a new graduate student (Sean Brennan) in the Water and Environmental Research Center (WERC) at the University of Alaska Fairbanks (UAF). We seek correlation between the strontium isotope composition of river water and otoliths in juvenile salmon in these different river waters. The ultimate goal of our study is to develop a technique, based on the hydro-geochemistry of otoliths to relate salmon stocks to the rivers they originated from, which will have practical applications in the management of water and salmon resources.
Progress/Completion Report, 2010, PDF