Regeneration of Adipose Fins Given Complete and Incomplete Clips

Abstract

Three groups of 12-month-old coho salmon Oncorhynchus kisutch (averaging 21 g/fish; 120 mm fork length) were adipose-fin-clipped in February 1993, and each group was coded-wire-tagged with a distinct tag code. We clipped the entire adipose fin from one group, the back two-thirds of the adipose fin from the second group, and the top two-thirds of the adipose fin from the third group. The fish were released in May 1993. During autumn 1994 (21 months after clipping), we checked all returning adult coho salmon for the presence of a coded wire tag, whether or not the adipose fin was present. Adipose fins were scored as having “no regeneration,” “partial regeneration,” or “complete regeneration” without knowledge of the type of clip applied. No fish from which the entire adipose fin was clipped exhibited regeneration. Complete regeneration was observed in 23% of the fish that had either the back two-thirds or the top two-thirds of the adipose fin clipped and partial regeneration was observed in an additional 35% and 63%, respectively.