FECUNDITY AND REPRODUCTIVE PERIOD, AND THEIR RELATIONSHIP TO CATCH RATES OF SPANNER CRABS, RANINA RANINA, OFF THE EAST COAST OF AUSTRALIA

Abstract

The occurrence of ovigerous females in a large-scale, stratified, randomized survey of exploited populations of spanner crabs (Ranina ranina) off the east coast of Australia identified their reproductive period to be around December each year. Patterns in the catch rates of male and female crabs showed that females were less susceptible to capture during this period, presumably due to reduced feeding when ovigerous. Greater susceptibility occurred immediately afterward when feeding activity may have increased. The fecundities of ovigerous R. ranina collected in 2 locations and during 2 reproductive periods were quantified, using an electronic Coulter counter to count eggs. There was marked variability in the numbers of eggs per brood among reproductive periods, with estimates ranging from 78,000-256,000 eggs per brood. There were positive correlations between fecundity and body size in each reproductive period. The results are discussed in terms of the management of this fishery, involving a minimum size restriction and closures on the capture of crabs during the reproductive period.