Adult Recovery of Hatchery Spring Chinook Salmon Adipose Fin‐Clipped and Coded‐Wire‐Tagged Using an Automated and Manual Marking Trailer

Abstract

AbstractMarking and tagging fish is a critical component of many hatchery monitoring and evaluation programs, and coded wire tags are part of the foundation for managing Pacific salmon Oncorhynchus spp. Fin‐clipping and coded‐wire‐tagging large numbers of juvenile salmonids is done either by hand or by using an automated tagging trailer system. We compared the hatchery adult recovery rate of spring Chinook Salmon O. tshawytscha marked and tagged as juveniles by manual and automated tagging trailers at Warm Springs National Fish Hatchery (NFH) and Carson NFH. At Warm Springs NFH, the adult recovery rate for fish marked in the automated trailer was 0.16%, compared with a recovery rate of 0.14% for fish marked in the manual trailer. A fish was 1.17 times more likely to be recovered as an adult at the hatchery if marked in an automated trailer. Coded wire tag retention rates were more variable for manually marked fish. At Carson NFH, there was no difference in recovery rate or coded wire tag retention rate between marking trailers. These data suggest that the automated marking procedure does not reduce adult recovery rates from the time of marking to adult return when compared with manual marking. The lower recovery rate of manually marked fish at Warm Springs NFH may have been due to manual marker inexperience, use of anesthetic, or other factors. Additional information on the implications of differential coded wire tag retention and adult survival related to marking methods is necessary for hatchery managers to make decisions on how to mark and tag their fish.