Comparing Two Methods Used to Mark Juvenile Chinook Salmon: Automated and Manual Marking

Abstract

Hatcheries in the U.S. Pacific Northwest are increasingly implementing programs that use an adipose fin clip and coded wire tag to mark a large number of juvenile salmonids Oncorhynchus spp. Traditionally, fin-clipping and tagging were done by hand, but the need to mass-mark large numbers of fish has led to the development of an automated tagging trailer system (Northwest Marine Technology, Inc.). We compared the adipose fin clip quality, coded wire tag retention, and injury rates of juvenile stream-type spring Chinook salmon O. tshawytscha marked and tagged at automated and manual tagging trailers at Warm Springs National Fish Hatchery (NFH) and Carson NFH, two hatcheries located in the Columbia River basin. Clip quality (99% good clips), tag retention (>98%), and injury rates (<7%) were similar between the two types of trailers at Carson NFH, where the manual markers had several years' experience clipping and tagging fish. At Warm Springs NFH, where the majority of manual markers had no previous experience, injury rates were similar (<14%) but the fish marked and tagged in the automated trailer had significantly higher clip quality (95% good clips) and tag retention (98%) than those marked and tagged in the manual trailer (70% good clips, 87% retention), where the clip quality and tag retention were poorest during the first day of tagging. Our results show that automated and manual trailers can perform similarly with regard to fin clip quality, tag retention rate, and injury rate when staffed by experienced markers. We recommend focusing efforts on training and quality control during the initial days of tagging and incorporating postmarking clip quality and coded wire tag retention sampling into all marking programs.