Salmon life stories recorded in...( MADISON Wis.---In work that has implic...)

MADISON, Wis.---In work that has implications for sport fisherman, scientists and natural resource agencies, University of Michigan researchers have developed a method that lets them reconstruct the environmental history of individual salmon and identify the juvenile habitat of an adult fish returning from the ocean to spawn.

In research to be presented at the annual meeting of the Ecological Society of America on Aug. 7, U-M researchers Brian Kennedy, Andrea Klaue, and Joel Blum, along with Dartmouth College researcher Carol Folt, have found that the element strontium, relatively common in bedrock beneath streams, accumulates in the bony tissues of Atlantic salmon and leaves a specific chemical signature, depending on the geology of the watershed in which the fish is living. This discovery could reveal whether certain rivers or tributaries produce fish that are more likely to survive their time in the ocean and successfully make the return trip to spawn in the stream where they hatched.

Conventional methods of tracing fish movements involve tagging thousands of juvenile fish in hatcheries with fin clips, dyes, or PIT (passive integrated transponder) tags and then hoping that the tagged fish are among the fraction that get re-caught as returning adults years later. It is a labor-intensive procedure that does not yield as much information as scientists would like. Young fish do not necessarily stay in the streams into which they are released, so the tag on a recaptured adult fish may only indicate where the fish was released as a juvenile, not where it spent most of its life. By taking advantage of the natural variation in strontium isotopes (alternate forms of the element that are present in different watersheds), scientists now can differentiate fish from specific geologic areas without having to use a man-made marker previously attached to a fish.

"It's a natural tag," says Kennedy, a research fellow in the Department of Geologica
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Contact: Nancy Ross-Flanigan
rossflan@umich.edu
734-647-1853
University of Michigan
6-Aug-2001

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