CAPTURE, ACCLIMATION AND TRANSPORT OF ATLANTIC TUNAS Ben Daughtry, and Forrest A. Young. June 2010
CONTENTS Collection technique, Early captive husbandry, Feeding and Acclimation of: Blackfin Tuna (Thunnus atlanticus) Skipjack Tuna (Euthynnus pelamis) Little Tunny (Euthynnus alletteratus) Transport and Post Transport Husbandry of Blackfin Tuna Conclusion Acknowledgements
Capture Technique Use of lures and live bait at seamounts more than 20 nautical miles out to sea Hook and line fishing using 20lb spin tackle Fish are lifted into live well while on line and released into tank with no contact to the fish’s skin by any foreign object (ie. Net or hands) Transported 4 fish (3 Blackfin and 1 Skipjack) in for a maximum time of 4.5 hours in 8’ (2.5 meter) well Used 2 , 5’ (1.5 meter) wells to transport all fish from dock to Dynasty Marine main holding facility (15 minutes) Used same technique to transport one Little tunny several days after initial capture
EARLY CAPTIVE HUSBANDRY All fish are very sensitive to handling and capture trauma, especially to the skin Due to their other eccentricities they appear to require high water quality standards and significant swim area. Tank size was 22’ Long X 18’ Wide X 5’ deep (15,000 Gallons) All fish were feeding with in 2 week of capture. They appear to need to feed multiple times daily and the Blackfin are finicky about their food. Smaller tuna (2-5 lbs) survive well in existing holding systems that we use for pelagic sharks and other pelagic fishes. Larger fish (6-8 lbs) had longer term issues.
SHORT TERM CAPTIVE HUSBANDRY Tunas can be challenging to acclimate to feeding in captivity. We have felt it best to acclimate them to feeding prior to any attempted transports. The Blackfins prefer eating small silvery fish and are fussy about the size of food presented. Best results were achieved by feeding small/medium fish like pilchards and small scads. (1.5”-2”). The Skipjack tuna and Little tunny fed more readily than Blackfin tuna.
SHORT TERM CAPTIVE HUSBANDRY We had good results from feeding to satiation on a daily basis, this meant 3-4 feeding times daily and offering a variety of foods. Small fishes were preferred in many cases, specifically with the tunas. Tunas appeared to be more temperamental feeders. They showed loss of weight and vitality quickly during fasting periods. Based on their high energy budget we feel they would do poorly if fasted prior to transport Both the largest Tuna and the Skip jack had problems with apparent self sustained injuries in the holding tank after 3-4 weeks and eventually had to be euthanized.
TRANSPORT OF TUNAS On October 29th of 2009 we attempted a mock transport of the 2 smaller tunas. This was done at our facility in Marathon. This was a 24 hours, simulation of a 1500 mile road trip or cross Atlantic air transport. We transported 2 Blackfin tuna, one 40 cm and the other 45 cm. (estimate) We used plastic sheeting and bags to remove the tunas from their tank without touching them. The mock transport was accomplished in a circular 2.5m (8’) diameter pelagic transport tanks, approx 3000L (750 gal). Dissolved O2 was kept at 130%-150% of saturation at 27-28 C. We did have some ammonia challenges due to feeding right up to the transport. This was handled with the addition of Amquel and bi-carb as needed.
POST TRANSPORT CAPTIVE HUSBANDRY The tunas both survived. Only one of the individuals began eating immediately after the mock transport and this same one ate in the transport tank while underway. It took dedicated efforts to get both tuna feeding regularly post transport. Eight days after the mock transport one of the tunas hit the tank wall and had to be euthanized due to excessive damage. The second tuna lived for more than 2 ½ months after transport before a cold front dropped the water temperature to 15 C. At this point the tuna began to swim erratically and rub the wall. The Little Tunny (Euthynnus alletteratus) was able to survive the cold temperatures , but succumbed some 4 months later to a Dylox treatment.
Conclusion The Blackfin tuna, Skipjack tuna, and the Little tunny are all very interesting potential display species. They do have certain eccentricities that will need to be overcome for long term success, but with maximum sizes in the 20-25KG range they hold a unique opportunity for displaying truly pelagic fishes in “smaller” tanks.
Acknowledgments Yoshitaka Abe, Aquamarine Fukushima, Fukushima Prefecture Japan Kenichi Fuji, Aquamarine Fukushima, Fukushima prefecture Japan Toshiki Matsuyama, Tokyo Sealife Park, Tokyo Japan Manny Ezcurra, Monterey Bay Aquarium, CA John O’Sullivan, Monterey Bay Aquarium, CA Collection staff, Husbandry staff at Dynasty Marine Associates, Inc Josh Moreira, Dynasty Marine Associates, Inc. Marathon, FL USA