Maturation of Squalus mitsukurii and Cirrhigaleus asper (Squalidae, Squaliformes) in the southwestern equatorial Atlantic Ocean

Abstract

Specimens of Squalus mitsukurii (n = 206) and Cirrhigaleus asper (n = 93) were opportunistically collected from the catches of a research vessel using traps and benthic longlines off the coast of northeastern Brazil between March 1997 and August 2002. For both species, larger females than males were captured. Catches of S. mitsukurii were biased toward females (1:4.6), while no significant disequilibrium in sexes was detected for C. asper (1:0.86). Common regressions for total length (TL) and eviscerated weight (EW) were calculated as LnEW = 3.13LnTL-6.217 (S. mitsukurii) and LnEW = 3.22LnTL-7.01 (C. asper). Based on changes to the reproductive tract, females and males of each species were categorized into several stages of maturation. Sizes at sexual maturity for female (n = 169) and male (n = 37) S. mitsukurii were 77.8 and 65.0 cm TL, respectively. Gravid S. mitsukurii had between 3 and 11 embryos that ranged in size from 2.0 to 22.5 cm TL (n = 262). No significant bias in the sex ratio of embryos was detected. A clear relationship between embryonic development and maturation of the ovary demonstrated that female S. mitsukurii are ready to ovulate immediately after parturition. Female (n = 43) and male (n = 50) C. asper approached sexual maturity at 110.0 and 91.0 cm TL, respectively. Uterine fecundity in gravid C. asper ranged from 12 to 19 embryos that varied in size between 4.0 and 21.9 cm TL. Unlike S. mitsukurii, there was no concurrent development of the ovary and embryos. The results are discussed in terms of the reproductive plasticity of S. mitsukurii and the need for further life history studies on both species.