Sex ratios, size at sexual maturity, and spawning seasonality of dolphinfish ( Coryphaena hippurus) captured in the Gulf of Tehuantepec, Mexico

Abstract

Aspects of the reproductive biology of dolphinfish ( Coryphaena hippurus) in the Gulf of Tehuantepec, Mexico, were analysed. A total of 7371 fish were obtained from catches of artisanal fisheries during the period of December 2004–2007. The reproductive activity was assessed using gonad histology, oocyte development, maximum whole oocyte size, maturity, and gonadosomatic index. The sex ratio (males:females) was 1:1, except in April–May (1:1.5, P < 0.05) and November (1:0.5, P < 0.05). The sex ratio at different size classes showed a significant bias towards females at smaller sizes (<75 cm FL), whereas the males were predominant in the larger size classes (>100 cm FL). The estimated size-at-50%-maturity for females was 48.38 ± 0.84 cm, whereas for males it was 50.57 ± 2.16 cm. The batch fecundity for female fish between 49 and 129 cm FL was 45,022–1,930,245 hydrated oocytes per female. The average interval between spawns was 2.0 days. The size distribution of oocytes, with at least two groups of oocytes in the ovaries, suggests that C. hippurus is a multiple spawner with an extended spawning season in the study area. The results suggest a pre-spawning migration and evidence of two main spawning events occurring in May–July and November–January as well as intense utilisation of the coastal zone of the Gulf of Tehuantepec as an area for reproduction, with aggregation behaviour during spawning.