A METHOD OF SIMULTANFX)USLY 



TAGGING lARGE OCEANIC FISH AND 



INJECTING THEM WITH TETRACTCLINE 



A simple method of marking large oceanic fish 

 such as yellowfin tuna, Thunnus albacares, and 

 wahoo, Acanthocybium solandri, for age determi- 

 nation studies is described. The method, devel- 

 oped for tagging and injection with tetracycline of 

 yellowfm tuna >45 kg from the deck of sport fish- 

 ing vessels, is easily adaptable to other species, 

 including billfish and possibly marine mammals. 

 The use of calcium-specific markers, such as 

 oxytetracycline (OTC), to validate the temporal 

 significance of natural marks in hard parts has 

 become increasingly widespread. Validation is 

 recognized as a basic requirement of age and 

 growth studies (Beamish and McFarlane 1983). 

 OTC is usually administered orally, intraperi- 

 toneally, or intramuscularly (Weber and Ridg- 

 way 1967; Wild and Foreman 1980; Campana and 

 Neilson 1982). Boating and restraining while 

 OTC is injected causes stress and trauma to the 

 fish and may result in injury to the tagger when 

 large, powerful pelagic fish are tagged. Neverthe- 

 less, biologists from the Inter-American Tropical 

 Tuna Commission (lATTC) have successfully 

 tagged and injected medium-sized (up to 36 kg) 

 yellowfin tuna (Anonymous 1982) where, using 

 multiple poles (two pole method, described in 

 Godsil 1938), the crew pulled the fish onto the 

 padded aft deck (Bayliff and Holland 1986) of a 

 dedicated tuna baitboat. Although this method 

 would probably suffice when tagging even larger 

 fish, dedicated vessels are costly and there is no 

 guarantee of locating adequate-sized fish during 

 the charter period. Opportunistic tagging by the 

 crews of long-range sportfishing boats, which fre- 

 quently capture large tuna but lack gear to han- 

 dle live fish on deck, was an attractive prospect. 



Methods and Materials 



A device used for administering drugs to zoo 

 animals (Extend-0-Jector\ model A, Kay Re- 

 search Products, Hyde Park Bank Bldg., Suite 

 503, 1525 East 53rd St., Chicago, IL 60605 USA) 

 was modified (Fig. 1) by adding a stainless steel 

 dart tag applicator held at an appropriate dis- 

 tance with 13 mm thick PVC sheet press-fitted to 

 the distal end of the injector head. The applicator 



'Reference to trade names doe.s not imply endorsement by the 

 National Marine Fishers Service, NOAA. 



was then fastened to the grooved base of the injec- 

 tor head with a hose clamp, stabilizing it during 

 use. Other types of applicators, such as those used 

 for metal anchor tags (Bayliff and Holland 1986) 

 can be easily substituted. Depending on the tag 

 type, a rubber band may be used to hold the tag in 

 place during application. 



The device utilizes either a 3 to 5 cc disposable 

 syringe and a 2-in (51 mm) needle. For tunas, a 17 

 gauge needle provided the best combination of 

 sufficiently high delivery rate and minimum 

 puncture diameter. 



As the decks of most long-range sportfishing 

 boats are quite far off the water (2 m), the device 

 was bolted inside a 25 mm ID telescoping tubular 

 aluminum pole, the type normally used with 

 swimming pool cleaning equipment. The length 

 may then be adjusted to suit individual situa- 

 tions. 



When a large tuna was captured by an angler, 

 the tag and injection was administered below the 

 second dorsal fin while the fish was still in the 

 water. Through trial and error, application was 

 found most efficient when the device is con- 

 tinuously pushed toward the fish's body after ini- 

 tial insertion of the applicator needles. Best re- 

 sults are obtained when the device is kept as near 

 to perpendicular to the body of the fish as possi- 

 ble, preventing the needles from bending, damag- 

 ing the fish, or both. The fish is released by 

 removing the hook by jerking the bend of the hook 

 with a gaff forwards while pulling the line back- 

 wards, or cutting the leader as close to the hook as 

 possible. Under certain conditions, free- 

 swimming fish found at the surface may be 

 tagged and injected. 



A previous experiment (unpubl. data, Inter- 

 American Tropical Tuna Commission, La Jolla, 

 CA) determined that doses as low as 10 mg/kg 

 body weight formed readable marks in the verte- 

 brae of mackerel. Scomber japonicus. Wild and 

 Foreman (1980) and Foreman (1987) determined 

 that a dosage of 27 mg OTC/kg body weight 

 formed a brilliant mark in the otoliths of yel- 

 lowfin and skipjack, Katsuwonus pelamis , tunas 

 and in otoliths and vertebrae of bluefin tuna, 

 Thunnus thynnus . For large fish (near 45 kg), the 

 volume required using standard veterinary in- 

 jectable (100 mg/mL) OTC would be unmanage- 

 able; a more concentrated form (200 mg/mL; 

 Pfizer Liquamycin LA-200) was substituted. Be- 

 cause the marks formed in smaller fish were suf- 

 ficiently bright, the dose was reduced by half, to 

 about 13.5 mg/kg. 



FISHERY BULLETIN: VOL. 8.5, No. 3. 1987. 



645 



