Age and size compositions, growth and reproductive biology of the breaksea cod Epinephelides armatus, a gonochoristic serranid

Abstract

Details of the reproductive biology, size and age compositions and growth of the breaksea cod Epinephelides armatus, the sole representative of Epinephelides, were obtained by collecting monthly samples of a wide total length (LT) range of individuals from coastal marine waters at 31–32° S on the lower west coast of Australia. Although the modal LT class of females (250–299 mm) was markedly less than that of males (400–449 mm), the modal ages of the two sexes were similar, i.e. 4 v. 5 years, respectively. The similarity in the age compositions and the histological demonstration that the gonads of all E. armatus consist solely of either ovarian or testicular tissues demonstrate that this species is gonochoristic, which is highly unusual for an anthiinine serranid. The absence of a central, membrane‐lined ‘ovarian’ lumen in the testes of juveniles would account for adult testes containing neither this ovarian remnant nor the peripherally located sperm sinuses that are found in the mature testes of almost all other serranids. The results demonstrate that E. armatus exhibits a very unusual pattern of sexual development for a serranid. The spawning period of E. armatus lasts for c. 9 months, which is long for a species in temperate Western Australian waters, but comparable with that of many other relatively small serranids elsewhere. Females grow slower than males, attaining LT at 3, 5 and 10 years of c. 200, 285 and 420 mm, respectively, compared with c. 215, 315 and 450 mm, respectively. Females, however, attain maturity at a greater LT and older age than males.