Reproductive biology of the greeneye spurdog Squalus chloroculus
Published online on 21. January 2015
Reproductive biology of the greeneye spurdog Squalus chloroculus (Squaliformes, Squalidae)
B. E. A. Rochowski, K. J. Graham, R. W. Day, T. I. Walker
ABSTRACT:
The reproduction of the greeneye spurdog Squalus chloroculus was studied based on animals caught in the multispecies and multi-gear southern and eastern scalefish and shark fishery on the upper continental slope off southern Australia. One hundred and ninety-nine females (502–990 mm, total length, LT) and 189 males (515–810 mm LT) were examined. The female reproductive cycle, based on 41 breeding animals, is continuous and triennial, with the pregnancy period estimated to be 31–34 months, seasonal and synchronous with the ovarian cycle; a third of the breeding female population is estimated to give birth between September and December each year. The estimated LT at which 50% of females are mature is 799 mm (95% c.i.: 794, 804), whereas the LT at which 50% are maternal is 825 mm (95% c.i.: 817–833), but these estimates are probably biased by the phenomenon of apparent change of LT at maternity and LT at maturity following severe length-selective fishing mortality. Litters ranged from four to 15 embryos with a 1:1 sex ratio, and litter size increased with maternal length. The breeding cycle of males is neither seasonal nor synchronous with the female cycle. The estimated LT of males where 50% are mature was 629 mm (95% c.i.: 603, 645).
Journal of Fish Biology. doi: 10.1111/jfb.12593