The Inter-American Tropical Tuna Commission’s Early-Life History Group’s Achotines Laboratory, which has conducted research on tropical tunas in the Republic of Panama since 1986, recently reached the milestone of successfully sustaining spawning yellowfin tuna in captivity for 25 years.
The project began in 1994 with an expansion of the laboratory’s tank and seawater system at its site in Las Escobas del Venado, Panama, financially supported by IATTC and the Overseas Fishery Cooperation Foundation (OFCF) of Japan. The expansion was to accommodate research of yellowfin tuna in the lab. Staff at the lab then collected wild yellowfin in local waters near the laboratory, which were initially stocked into small reserve tanks before being transferred to an in-ground, concrete spawning tank.
By October 1996, the captured yellowfin tuna had commenced spawning. The laboratory officially celebrated 25 years of sustained spawning in captivity, and the program considers itself to have achieved the only sustained spawning of yellowfin tuna in captivity in the world. The ELH Group has published descriptions of the spawning and courtship behavior of the adult fish, and the effects of physical factors on spawning and egg production.
Since the first spawn in 1996, laboratory staff have collected over two billion fertilized eggs for research on reproductive biology and early-life history. The ELH Group continues to conduct ecological experiments to estimate the effects of biotic and environmental factors on the egg, larval, and early juvenile stages of yellowfin and uses the results to develop growth and survival models of early life stages prior to recruitment to the tuna fisheries in the eastern Pacific Ocean.
The average yellowfin at capture is approximately 60 cm long and 1.2 years old. The average residence time in the spawning tank is two years, though individual fish have resided in the tank up to six years. Fish in the spawning tank are fed a diet of 50 percent squid and 50 percent sardines, and gain 22 to 23 kilograms per year on average.
The group is now expanding its research from the egg/larval stages (0-1 month) to the early-juvenile stages (1-6 months). The studies of yellowfin growth and survival during the first six months after capture have strong application to tuna ecology and aquaculture. Improved rearing success of early-juvenile yellowfin now provides opportunities to study density-dependence in juvenile growth, to release tagged early-stage juveniles in coastal waters of the Panama Bight in order to provide more information on pre-recruitment movements and distribution, and to support the potential completion of full life-cycle rearing of yellowfin.
The ELH Group is also studying the potential effects of climate change on early yellowfin life-stages. This research has included laboratory investigations of the effects of ocean warming, ocean acidification, and oxygen stress on the egg and larval stages of yellowfin, and the results have been used to develop models of the current and future effects of a variable climate on the yellowfin populations in the Pacific Ocean.
Most of the yellowfin research has been conducted by the ELH Group of IATTC, but investigations have also been conducted in collaboration with Japanese scientists, the University of Miami’s aquaculture program, and other academic and non-governmental researchers. In 2015, in collaboration with Japan's Kindai University, the first transfer worldwide of yellowfin juveniles from land-based tanks to a sea cage was successfully completed at the Achotines Laboratory.
Photo courtesy of IATTC Achotines Laboratory
