In 1996, the Inter-American Tropical Tuna Commission (IATTC) stocked its first yellowfin tuna (YFT) Thunnus albacares broodstock fish in a semi-recirculated concrete tank (17 m diam x 6 m depth, 1,362 m3 volume) at the Achotines Laboratory, Republic of Panama. Today, after 27 years and more than 5,800 natural spawning events, we summarize the broodstock management, reproductive biology, and spawning profile observed during these years.
YFT were captured off the coast of the Peninsula de Azuero, in the Panama Bight, at an average size of 59 cm fork length (FL) and transported to the Laboratory, where they were weighed, measured, and kept in quarantine tanks to conduct prophylactic treatments. Subsequently, the fish were held in tanks of 170 m3 volume until reaching an average size of 74 cm FL and 8.8 kg in weight (WT), when they were transferred to the main broodstock tank (T1). Since 1996, a total of 236 fish became broodstock fish in the main tank, of which 50% were males, and 50% females. The average yearly relative mortality was 55%, and the main cause of death was wall strikes, followed by death by starvation and blindness. The average residence time in T1 was 1.4 years, and the fish with the longest residence time in captivity spent 5.8 years in T1 and had an estimated age of 7 years.
Broodstock was fed a diet of fresh fish (sardines) and squid at approximately 3–4% body weight per day, with a supplement of vitamin and mineral pre-mix. Estimated growth rates in FL ranged from approximately 12 to 68 cm year-1, and in WT, ranged from approximately 9 to 46 kg year-1.
From October 1996 to October 2023, a total of 1.87 billion eggs of yellowfin tuna were collected from T1, averaging 67 million eggs per year. Eggs were collected in 80% of the 328 analyzed months. Spawning occurred at water temperatures ranging from 23.3 to 29.7 °C and spawning generally ceased during the lower temperature ranges (< 24 °C), when coastal upwelling occurred from January through March. An analysis of the average egg production per mature female biomass per month was conducted, and the standardized egg production was compared with water quality parameters measured daily such as temperature, salinity, pH and dissolved oxygen, with a linear regression.
The yellowfin tuna broodstock program of the IATTC not only represents an important milestone for the management and conservation of the species, enabling research on the various aspects of early life history, but it also demonstrates feasibility towards the aquaculture development for commercial purposes.