Wednesday, November 24, 2010

Measuring Survival of Salmon Produced at Federal Hatcheries

We are often interested in determining if salmon grown and released at a U.S. Fish and Wildlife Service hatchery survive in the ocean better than salmon from other hatcheries. Likewise, we need to determine how many hatchery fish are caught in commercial, tribal, and recreational fisheries that occur in the Pacific Ocean and Puget Sound. In order to do this, we sample the fall Chinook, winter steelhead and coho salmon when they return to Makah, Quilcene and Quinault National Fish Hatcheries to detect how many contain a tag made from a small piece of wire.

Dissecting salmon snout
These tags are inserted into the noses of thousands of baby salmon each year before we release them from the hatcheries. Each tag has a 6-digit number that identifies each group of fish that we are responsible for monitoring. When the fish are released from the hatchery, we enter the tag number into a database along with information about where and when these fish are released. When the fish return to the hatchery 2 to 6 years later, the adult fish are put through a metal detector to check for a tag. If a tag is present, the fish is measured and the head is taken back to our lab. 

Back at the lab, we dissect the tag from the salmon’s snout and read the number with a microscope. The tag numbers are then entered into the same database along with other biological information we collect. State and tribal agencies similarly enter the tag numbers they detect in adult salmon caught in fisheries taking place in the Pacific Ocean and Puget Sound. At the end of the year, we summarize information in this database to evaluate the success of each U.S. Fish and Wildlife Service hatchery and its ability to produce enough fish for the many anglers who rely, in part, on hatchery fish for tribal culture, commercial interest, and recreation.

Here are two short videos showing how we process the salmon heads to recover the tags: