Hatchery salmon are not all the same!

Published 2018-02-08

Photo: Oregon State University

Salmon are an important member of the ecosystem, economy, and culture in the Pacific Northwest region of the United States. However, over the past several decades, wild populations of salmon in the region have decreased significantly, with many stocks listed as threatened or endangered under the US Endangered Species Act. In the 19th century, hatcheries for salmon were developed and now serve a role in providing salmon and steelhead stock for fisheries and contributing to conservation efforts. Although hatcheries show the potential to have a positive impact, many questions remain on the effectiveness and impact of these facilities.

A new study published in Environmental Biology of Fishes, authored by researchers at Oregon State University, documented differences in the biology of young fish reared in the hatchery environment. They found that not all young salmon are the same and that there is significant variation among individuals. During their work on hatchery salmon, the researchers noticed that a group of individuals stayed near the top of the tank to feed, while others remained on the bottom. They then separated these individuals to different tanks to see if their behavior remained the same when competition with the other group was removed. Interestingly, the behavior of each group was consistent after separation. Researchers then compare body sizes between the groups after six months and found that individuals which remained on the bottom of the tank where smaller with deeper bodies than those on the top of the tank. These findings were consistent across four years of hatchery broods. The variation may relate to the genetics of these groups as the trend also varied between families.

This documented difference in fish behavior and body condition indicates that not all salmon are the same and may have implications for rearing practices in hatchery settings.