Thursday, March 10, 2011

How Many Salmon Live in a River?

Screw trap in the Big Quilcene River
It’s that time of year again when young Big Quilcene River coho salmon (smolts) begin to outgrow the home they have lived in for the past year. Soon they will begin to make their way downstream and into Hood Canal where they will find habitat that will allow them to continue to grow. The fish will spend up to 2 years there, out of the fresh water of the Big Quilcene River, eating and growing to adult size.  Some of these fish will return to the river after only 1 year; these fish are called jacks. The majority, though, will return after spending 2 full years in the ocean.
Staff preparing to install trap
To monitor the number of juvenile smolts leaving the river and going out to the salt water, we installed a trap that gently collects fish as they swim downstream. The trap we installed is a screw trap; it is made of a metal cone in the shape of a funnel that spins in the water. This type of trap allows fish to be funneled through the trap into a live box where they are held. The cone and live box are suspended on the water by two pontoons. An employee from our office will check the trap daily and take data on any fish caught in it. Any coho smolts caught in the trap are tagged and then released to complete their journey to the ocean. This tag will allow us to identify these fish when they return as adults. 

The trap will remain in the Big Quilcene River for the next couple of months, the entire time period when fish are headed out of the river to the ocean.  From the data collected during this time, we will be able to determine how many coho salmon left the Big Quilcene River for the ocean and how many fish call the Big Quilcene River home.

Looking upstream at the screw trap