Subcutaneous Diazo Film Tag for Small Fishes

Abstract A small subcutaneous tag of inexpensive diazo film, in the shape of a rear-notched arrowhead and bearing a 4-digit serial number, was surgically implanted into the dorsal musculature of small poeciliid fishes. In the laboratory, tag retention after 18 months was 62.5% and no mortality was attributable to tagging; mortality in the field was 3.5% of 750 fish tagged. The tag must be implanted manually, which limits the number of fish tagged to about 300 per day.