Oocyte dynamics for Atlantic bluefin tuna (Thunnus thynnus) in the southern Gulf of Mexico: A comparative assessment of Mediterranean spawners using two stereological methods.

Although most research focused on the northern Gulf of Mexico for western Atlantic bluefin tuna, the histological records of reproductive activity of this species in the southern Gulf of Mexico (Mexican waters) have been presented for the first time. This work is the first to study oocyte dynamics in Atlantic bluefin tuna caught in the southern Gulf of Mexico by assessing and comparing them with Mediterranean stock (BFT-E) through stereology using two different methods. Regardless of Atlantic bluefin tuna females returning to their respective spawning grounds at different months in the southern Gulf of Mexico and the Mediterranean, both stocks arrived reproductively inactive and remained in these zones during periods of similar length; they were reproductively active until March for the southern Gulf of Mexico and May for the Mediterranean females.

A possible new spawning area for Atlantic bluefin tuna (): the first histologic evidence of reproductive activity in the southern Gulf of Mexico.

The number of studies of reproductive biology for Atlantic bluefin tuna carried out in the Gulf of Mexico is significantly lower than those undertaken in the Mediterranean Sea. Four spawning areas have been found for the eastern Atlantic bluefin tuna stock in the Mediterranean Sea, so it is not implausible that there is more than one spawning area in the Gulf of Mexico for the western Atlantic bluefin tuna stock. The individuals used in this study were caught as bycatch by the Mexican surface longline fleet between January and April 2015.

Reproductive biology of little tunny (Rafinesque, 1810) in the southwest Gulf of Mexico.

The aim of this study was to describe the reproductive dynamic of in the southwest Gulf of Mexico. The annual variation of the volume fraction occupied by gametes and tissues in gonads were related with main body indexes, such as the gonadosomatic index ( ), the hepatosomatic index ( ), and the nutrition index ( ), and compared with the sea surface temperature. A total of 951 individuals were sampled, where a sex ratio of 1:1 and a size interval strongly skewed towards organisms with a fork length ( ) of 36-40 cm were observed.