Reproductive biology of the totoaba (Totoaba macdonaldi), an endangered species in the Gulf of California

The totoaba (Totoaba macdonaldi) is an emblematic species endemic to the Gulf of California, which has been protected since the mid-70 s by Mexican and international laws. For the present study, 153 totoaba individuals were collected from 2011 to 2014, on which gonad histology analyses were carried out. We identified six ovarian phases and eleven oocyte subphases in the gonad development of females; in males, four development phases were identified. The totoaba is an iteroparous species based on the number of breeding opportunities. According to the organization of the ovary and the presence of oocyte subphases, ovarian dynamics can be considered asynchronous, as demonstrated by the multimodal distribution of oocyte diameter. The totoaba is a batch spawner that releases oocytes over several months. The reproductive period spans from February to May, with a reproductive peak in March. Likewise, the gonadosomatic index showed that the reproductive activity of totoaba peaked in March and April. The female:male sex ratio, although variable throughout the sampling period, yielded an overall value of 0.89:1, with non-significant differences between the number of females and males (P > 0.05). The length at first sexual maturity (L-50%) was 1 354 mm TL for females and 1 299 mm TL for males. The average fecundity was 2 662 626 (standard error, s.e., 1 021 124) oocytes, and the average relative fecundity was 99 (s.e. 22) oocytes g(-1) (ovary-free). The mean and maximum oocyte diameter showed a positive and non-significant (P > 0.05) relationship with the mean sea surface temperature.