Meeting Abstract

P3.141  Thursday, Jan. 6  Comparative stereology of female Atlantic bluefin tuna, Thunnus thynnus, from the Mediterranean Sea and the Gulf of Mexico KNAPP, J.M.*; MEDINA, A.; LUTCAVAGE, M.; University of New Hampshire; University of Cadiz, Spain; University of Massachusetts Amherst jessie.knapp@unh.edu

The Atlantic bluefin tuna (Thunnus thynnus; ABFT) is a highly exploited, long-lived, highly migratory species and an economically valuable fisheries resource. ABFT are managed as two separate stocks assuming spawning site fidelity to two separate areas: the Gulf of Mexico and Mediterranean Sea. The western and eastern spawning stocks are assumed to have vastly different maturity schedules (8–16 vs. 3–5 yrs, respectively). Whether these profiles are realistic or result from sampling bias is not resolved, but inaccurate determination of the maturity ogive would hinder in stock assessments. Extensive research has been conducted on the eastern spawning stock, but similar research is outdated or lacking for the western stock. Our study provides a comparative analysis of the reproductive biology of western and eastern spawners using stereological methods allowing for quantification of otherwise qualitative maturity status classifications. Ovarian tissue was collected from 156 ABFT in the Gulf of Mexico during the known spawning period (April–June) from 2007–2009. Sampled ABFT ranged in length and weight from 180–341 cm, and 101–655 kg, respectively. Gonadosomatic index (GSI) of western fish ranged from 0.94–6.85. Ovarian tissue was collected from 174 ABFT in the Mediterranean Sea from 2008–2010. Length and weight of sampled fish ranged from 120–259 cm and 35–353 kg, respectively. GSI of eastern fish ranged from 0.2–6.9. A stereological comparison of the two spawning stocks in known spawning areas is the first step in the process of defining Atlantic-wide maturity profiles; the next challenging step is to examine ABFT across a broader range of size classes and beyond known spawning locations.