Fluorescent elastomer injection was used to mark newly settled Hawaiian coral reef fishes (8-56 mm SL) in the laboratory and in the field. Marking success was influenced by depth of subcutaneous tag injection, anatomical location of the tag, pigmentation of the skin at that location, and investigator's experience with the technique. Visibility up to several months and little mortality was achieved with careful handling of the fish and skillful placement of the injection. In the laboratory, mortality related to marking occurred within 24 h of the procedure. Within this time, one mortality was observed for fish > 20 mm SL; fish < 20 mm SL experienced 13% mortality. Fish marked and held in the laboratory showed 100%, tag visibility and retention for observation periods up to 76 d. Of 286 fish marked, released and tracked in the field, 67% were regularly resighted for observation periods up to 130 d. Of 59 fish observed in the field for at least 45 d, 36% were resighted; four were resighted at least 100 d after marking. Visibility of one tag was reduced over the first 30 d by growth of surrounding tissue. Because of small tag size and the large number of unique combinations of tag color and injection location, field identification of individuals was possible. Success in recognizing individually marked fish in the field required some observer experience. Although not necessary in this study, under low visibility conditions, resighting success could be enhanced with the use of UV-A filtered light.
