Reproductive biology of little tunny, Euthynnus alletteratus (Rafinesque), from the north-eastern Mediterranean Sea

Abstract

The study aimed at identifying spawning season and potential year classes reaching maturity in the north-eastern Mediterranean, an area where little information on tuna spawning is available. Gonads (60 ovaries and 36 testis) were obtained from little tunny, Euthynnus alletteratus. The fish were caught between November 2002 and May 2005 in the north-eastern Mediterranean Sea. The ovaries were histologically examined to determine the reproductive conditions and developmental stages of oocytes. Seven females sampled in May, July, and August were sexually mature (stage III or IV). The gonado-somatic index (GSI) indicated that spawning generally occurred between May and September. The most intensive spawning period was observed between July and August. The sex ratio was calculated as 1 : 1.7 M/F (total n = 96). The length and weight relationship was calculated with W = 0.038 L(2.77), ages from year I to IV being included in the analysis.