Temperature and dissolved oxygen requirements for survival of yellowfin tuna, Thunnus albacares, larvae

Abstract

We determined the optimal water temperature and oxygen ranges for survival, development, and growth of yellowfin tuna ( Thunnus albacares) eggs and yolk-sac and first-feeding larvae by conducting a series of experiments between 2004 and 2006 at the Achotines Laboratory on the Pacific coast of the Republic of Panama. Based on the results of our experiments, yolk sac and first-feeding yellowfin larvae exhibited lethal limits for their survival at temperatures less than 21 °C and greater than 33 °C. Embryos hatched alive at all temperatures tested except 36 °C; however, larvae were malformed after hatching at temperatures < 20 °C and ≥ 34 °C. Egg and larval development were significantly slower at mean incubation temperatures < 23 °C. Mean egg diameters were significantly greater at mean incubation temperatures < 26 °C compared with those incubated at temperatures > 27 °C. Within the temperature range for survival and normal development, mean specific growth rates in weight for larvae after 2 days of feeding maintained at mean temperatures of 21.3 °C, 26.6 °C, 27.5 °C, and 31.5 °C were 1.8%, 20.9%, 27.2%, and 45.0%, respectively. The optimal range of temperatures for rapid growth and moderate to high survival in first-feeding larvae was from about 26° to 31 °C. Lethal conditions (100% mortality) for larvae after hatching and shortly after the onset of first feeding occurred at dissolved oxygen concentrations of < 2.2 mg O 2 L −1 (< 34% oxygen saturation) at temperatures between 26° and 29 °C. Significantly lower survival first occurred for first-feeding larvae when the larvae were exposed to dissolved oxygen concentrations of 2.65 mg O 2 L −1 (40.4% oxygen saturation). Based on our experimental results, critical depths for survival of yolk-sac and first-feeding yellowfin larvae within the Panama Bight of the Pacific Ocean would occur at depths less than 30 m during the upwelling season and at depths less than 50 m during the reduced upwelling season, based on temperature alone. Limiting oxygen levels may occur at depths greater than 30 m during the upwelling season and greater than 50 m during the reduced upwelling season.