These practices are changing, however. Managers have recognized that passing fish upstream of the hatchery has many benefits: River habitat can be used for natural production of coho salmon; coho eggs, juveniles, and decomposing carcasses in the river have many food web and ecosystem benefits; and people just plain like to see salmon spawning naturally in our rivers and streams! In 2008 and 2009, hatchery managers allowed 200 adult coho to move upriver. During this time, USFWS biologists performed spawner and carcass surveys to evaluate how successful these fish were at spawning. We also performed snorkel surveys and installed a screw trap to evaluate rearing success of the juveniles.
|USFWS biologist checks the screw trap for fish|
So far, results have been encouraging. In the spring of 2010, we estimated that 1,000 to 2,500 outmigrating smolts resulted from the 2008 spawners. Not bad for a system recognized as having minimal spawning and rearing habitat! We will be continuing our studies next spring to see what results from the adults passed in 2009. Sadly, for various reasons, no adults were passed upstream this year. Nonetheless, passing coho upstream to spawn naturally is something we plan on doing every year as standard practice.
|Andrew measures, weighs, and marks the fish captured in the screw trap|