LABORATORY RESEARCH ON EARLY LIFE STAGES OF YELLOWFIN TUNA Thunnus albacares WITH AN EMPHASIS ON JUVENILE REARING STUDIES  

The Inter-American Tropical Tuna Commission (IATTC) has maintained a spawning population and studied the reproductive biology and early life history of yellowfin tuna Thunnus albacares at its Achotines Laboratory, Republic of Panama, since 1996.  The yellowfin research has been focused on ecological questions aimed at understanding the recruitment process and the factors that affect it.  Experimental investigations of the early life history have been conducted from the egg stage to over 140 days after hatching.  The ecological research conducted on yellowfin also has strong application to tuna aquaculture, providing important insights into reproductive biology in captivity and patterns of growth and survival during early life stages.  

Based on life history characteristics, the yellowfin is an attractive candidate species for full-life-cycle aquaculture.  Yellowfin exhibit high fecundity, reach sexual maturity in as little as 2 years in tropical waters, and grow rapidly as larvae, juveniles and adults.  However, challenges exist in the development of successful rearing methods for pre-adult stages of yellowfin.  The early life stages are characterized by fast growth, high metabolic demands and high mortality.  Mortality during the yolksac and early larval stages is particularly high, even though initial larval feeding incidence is elevated compared to most other marine fish larvae.  Starvation can occur rapidly (28 to 55 hrs) at first feeding at the high water temperatures (24 to 30°C) at which yellowfin develop.

Growth during the larval and early-juvenile stages is an important regulator of cohort survival of yellowfin in rearing systems.  Larval and early-juvenile growth is exponential in both length and weight, and the timing of the onset of piscivory during the post-flexion larval stage seems to promote fast growth and greater survival.  The juvenile stage of yellowfin is relatively long and the development of improved diets and husbandry techniques for juveniles will play a crucial role in successful development of full-life-cycle rearing.      

As part of a 5-year research project (2011-2016) of the SATREPS Program (Science and Technology Research Partnership for Sustainable Development), funded by JICA (Japan International Cooperation Agency) and JST (Japan Science and Technology Agency), the IATTC, Kindai University (KU) of Japan, and the Autoridad de los Recursos Acuáticos de Panama (ARAP) have conducted rearing studies of early-juvenile yellowfin at the Achotines Laboratory.  These studies have included laboratory trials investigating improved rearing practices, diet sequences, and for the first time worldwide, the successful transfer of early-juvenile yellowfin to a sea cage during 2015.  These juvenile rearing studies will be described.