Re-formation of Excised Fins of King Salmon Fingerlings and its Effects on Recognition of Marked Adults

Abstract

In marking experiments with king salmon (Oncorhynchus tshawytscha) fingerlings at Coleman Fisheries Station, California, in 1945 and 1946 half the fingerlings were held over for 6 months after marking. The extent of fin re-formation was studied during these periods. Standards based on the numbers of rays present were used in grading except in the adipose fin where size was the basis. Accidental suffocation of 1,200 fingerlings marked by removal of the adipose and left ventral fins provided a sample for careful analysis. These fish had been marked 3 months previously, but another 2,099 fingerlings from the same lot were examined at the time of release. Approximately 72 percent of these fish showed no or negligible fin re-formation; 21 percent had partially re-formed fins; 5 to 8 percent exhibited considerable re-formation. Of the fingerlings marked by removal of the left ventral and dorsal fins, 2,367 were examined at the time of release. In this lot 87 percent had no or negligible fin re-formation; 6 percent partial; and 7 percent considerable. Examination of 2,192 fingerlings marked by removal of the left ventral and anal fins was likewise made at the time of release. Eighty-one percent showed either no or negligible re-formation; 6 percent partial; and 13 percent considerable. Decided differences were shown in the extent of re-formation among the four fins studied. Correlation analysis of quality of mark in relation to length of fish was also made. The ventral fin showed slight correlation whereas the dorsal fin showed none.