Technical Notes: A Technique to Minimize the Adverse Effects Associated with Handling and Marking Salmonid Smolts

Abstract

A system that allows anesthetization of juvenile salmonids before netting during a handling and marking operation is described. Our purpose for designing the system was to reduce or minimize any debilitating effects associated with these activities. When compared with smolts handled and marked in the traditional manner, use of the technique resulted in a significant reduction in the mortality of naturally migrating smolts of spring‐summer chinook salmon Oncorhynchus tshawytscha during a posthandling and marking seawater challenge performance test. The treatment resulted in lower, but not significantly lower, plasma cortisol levels; however, sample sizes may have been too small for statistical verification. With a little ingenuity, the technique should be adaptable to most smolt handling or marking operations.

Migration Timing, Growth, and Estimated Parr‐to‐Smolt Survival Rates of Wild Snake River Spring–Summer Chinook Salmon from the Salmon River Basin, Idaho, to the Lower Snake River

“…Up to 100 wild fish from each study stream were collected using this separation-by-code system (Marsh et al 1999;Downing et al 2001). Recaptured fish were handled using water-to-water transfer and other best handling practices described by Matthews et al (1997). Fish were anesthetized, scanned for PIT tags, measured, weighed, and allowed to recover before their return to the bypass system for release below the dam.…”