New findings suggest that, contrary to current theory, life for young salmon is most treacherous in the sea.
Survival of young salmon has previously been thought to be most affected by disturbances and environmental quality in the freshwater lakes, streams, and rivers where they spend their early and late life stages. However, researchers from the Pacific Ocean Shelf Tracking (POST) project of the Census of Marine Life have found that up to 40% of young salmon that make it to the sea, perish soon afterward, and never return to freshwater to spawn. By implanting acoustic tracking tags in young salmon, researchers were able to track their movements from the freshwater environment, out to sea during their saltwater phase, and then back again as they return to spawn. The results of these efforts show a vastly different picture than conventional biological theories previously suggested.
Formerly, the freshwater phase of salmon was thought to be the most critical component of their life cycle. As Pacific salmon populations have declined in recent decades, huge effort has been placed in conserving, restoring, and buffering the freshwater habitats that support salmon populations in an effort to bolster these populations. These new data, however, are suggesting that survival during the saltwater phase of a salmon's life cycle is more difficult.
By comparing two similar freshwater systems in close proximity to one another, one being relatively "natural" and untouched and one being heavily dammed and "altered", researchers were able to show that young salmon survived the trek to the sea in relatively equal numbers. This suggests that the alterations to the freshwater environment did not affect their survival. The data also show that almost half of the salmon that made it to the sea did not return to spawn. Thus, as this research produces more data, and the importance of the ocean's role in salmon life cycles becomes more clear, sea survival may become a critical issue in the future management of Pacific salmon.
||New findings in the survival of Pacific salmon may change views on conservation and manangement.
||POST Scientists --> D. Welch, S. McKinley, E.L. Rechisky, M.C. Melnychuk, C.J. Walters, C. Schreck, B. Clemens, and R. Bison
||Fraser River system in Southern British Columbia, Canada and the Columbia River system in the Pacific Northwest United States
||Acoustic tracking arrays and implanted tags allow researchers to track movements of young salmon during their migrations.
||Submitted for Publication