Breeding of Panulirus longipes cygnus George under natural and controlled conditions

Abstract

Fertilization of eggs is external: the female does not need to be newly moulted to be mated. The incubation period of eggs (19-68 days) varied inversely with water temperature, being longest at 19º C and shortening towards an asymptote at 25º C.

Most adult females breed every year. When given abundant food, 77% of those breeding in aquaria at ambient temperature had two successive spawnings in a breeding season, whereas in a relatively crowded part of the natural population less than 12% of the breeding females spawned twice in a season. When held at a constant temperature of 25º C and given abundant food, adult females bred continuously, averaging six spawnings and three moults each year.

In the natural population, size at first breeding and mean size of breeding females did not vary with depth but differed from one locality to another. At the Abrolhos Islands where the present density of breeding stock is highest, adults appear to be stunted and fecundity is relatively low. This situation may have existed to some extent in other parts of the population before heavy commercial fishing of the past 20 years or more reduced the density of the breeding stock to present levels.

The operation of density-dependent regulation of fecundity in this population is discussed.