An Automated Device to Release Marked Juvenile Fish for Measuring Trap Efficiency

We describe a floating device that allows for the automated release of juvenile salmonids into rivers and streams at a predetermined time. This device is useful in studies using floating traps to estimate the number of downstream‐migrating juvenile salmonids. The device assists these projects by enabling the release of fish at dusk, when juvenile salmonids typically begin to move downstream. Release of fish at dusk or night is preferable to daylight releases to reduce potential predation on juvenile fish. This device eliminates the need for project personnel to remain at the release site to perform this function.