Evaluations of Visible Implant Fluorescent Tags for Marking Coho Salmon Smolts

Abstract

Groups of about 10,000 smolts of coho salmon Oncorhynchus kisutch were marked with one of two types of fluorescent tags: visible implant fluorescent filament (VIF) and visible implant fluorescent elastomer (VIE). Fish were also tagged with coded wire tags and adipose fin clipped to assess fluorescent tag retention and marine survival. Ocean recoveries were reported through the coastwide mark–recovery database. Returning fish were examined for the presence of tags, and survival and exploitation data were compared among groups. Fluorescent tags in approximately 90% of fish bearing them were easily seen in natural light. Probabilities of recovery, either in fisheries or spawning escapements after fisheries, and survival rates, did not differ significantly between coded-wire-tagged fish with and without fluorescent tags (either type). Short-term losses of fluorescent marks were about 5%; long-term losses between application and recovery were about 28% for VIE but were not statistically significant for VIF. Losses were attributed mainly to the inexperience of the people marking the fish, to handling related losses, and to problems with the catalyst in the elastomer.