Effects of temperature on embryonic development of Atlantic bluefin tuna (Thunnus thynnus, L 1758) and Atlantic bonito (Sarda sarda, Bloch 1793)

Abstract

Temperature is the most important abiotic factor controlling the very early life of fish. Data on development, hatching, and survival responses of fertilized fish eggs to varying temperatures are essential to understand fitness of Atlantic bluefin tuna (ABFT) and Atlantic bonito (AB). In this study, we investigated i) the effect of tem- perature on viable hatching rate and ii) the relationship between temperature and the timing necessary to reach different developmental stages. Our findings show that the thermal range for viable egg hatching is colder in AB than in ABFT. ABFT eggs hatch from 18 to 33 ºC, highest around 26–27 ºC; below 21 ºC or above 30 ºC at least 50 % of the hatched larvae were abnormal, while below 19 ºC and above 32 ºC the larvae had no chance to survive, having highest survival chance at around 26 ºC. In AB, eggs hatched from 16 ºC to 28 ºC, being optimal around 21–22 ºC, the incidence of abnormal larvae was very high above 27 ºC and at 16.5 ºC, and larvae had no chance to survive above 28 ºC and had the highest survival chance at around 21 ºC. ABFT eggs required longer times to hatch than other tuna species. The results obtained in this study are an important tool for aquaculture; here, we describe the best temperature conditions for successful and viable hatching in ABFT and AB, which may help to improve modelling tools and to develop better indices of annual recruitment and the possible impact of future global temperature changes.