Retention of fin clips and fin and operculum punch marks in rainbow trout

Abstract

Fin clips (complete fin removal) or punch marks (stamping of a hole) in fins or operculum are quick and inexpensive methods to identify individuals or groups of fish. This study evaluated the retention of 6 mm diameter punch marks on the operculum, caudal (upper and lower lobes), dorsal, pelvic, and anal fins, and fin clips on adipose, pectoral, pelvic, dorsal and anal fins of rainbow trout Oncorhynchus mykiss for 279 days. Growth and survival were not significantly different among fish with the different mark types or locations. At the end of the experiment, 100% of adipose clips, 97% of pectoral and anal fin clips, and 93% of dorsal clips and pelvic fin clips were retained. Retention of punch marks was 57% and 50% for the lower and upper caudal fin lobe locations respectively, 23% for the dorsal fin, and 3% for the operculum. No pelvic or anal fin punch marks were identified at the end of the trial. Significant differences in retention among the treatment groups did not occur until 125 days post marking, after which all fin clip treatments had significantly greater retention than pelvic and dorsal punch marks. Beyond 244 days, fin clips outperformed all punch mark locations.