In the past, Bristol Bay, Alaska has produced more wild-caught sockeye salmon (Oncorhynchus nerka) than any other region in the world, with record runs exceeding 50 million fish annually.  Recently, however, adult sockeye runs in Bristol Bay have declined dramatically, even though counts of both juvenile fish leaving the rivers for the ocean, and adults returning to the rivers to spawn, have indicated strong sockeye salmon production in the freshwater tributaries to the Bay.

Sockeye salmon in this region support a long-established fishery, generating millions of dollars annually and providing thousands of jobs.  They also play a critical role in Alaska’s sensitive coastal ecosystems.  Adult sockeye salmon returning to Bristol Bay's tributaries provide food for killer whales, grizzly bears, eagles and other predators.  Eggs deposited in the streams and rivers feed many other species of fish throughout the system.  Even in death after spawning, tons of decaying salmon flesh contribute marine-derived nutrients used by both plants and animals along Alaska’s rivers.

Recent scientific studies have linked salmon survival in the Pacific Ocean to large-scale climate change or climate fluctuations, however, little is known about the causes of such fluctuations or how they impact salmon production.

    
New integrative work is needed to understand how salmon growth and survival are linked to climate change at the local and regional scales.

Our study is designed to measure historical patterns of sockeye growth in marine and freshwater environments and identify linkages between growth rates and climatic conditions.  Growth rates will be measured using data derived from archived fish scales collected from the 1950’s to today.  We will examine the relationship between the climatic record for the Bristol Bay area and adjacent ocean environments and (a) juvenile growth in freshwater, (b) early marine growth, and (c) adult sockeye salmon production.

    
Using time-series statistical analyses, we will attempt to relate juvenile growth in freshwater to:

• adult escapement (number of adults entering tributaries to reproduce)
• terrestrial climate factors such as air temperature and precipitation
• the magnitude and age/size composition of smolt (juvenile fish) leaving the rivers

Early marine sockeye growth and adult sockeye production will be analyzed in relation to coastal sea surface temperature.

This study will provide a thorough analysis of the effects of climate change on sockeye salmon production in Bristol Bay during the freshwater and early marine life stages that are most likely to be sensitive to fluctuations in climate.