he number of days over which a single brood hatches highlights subtle differences between temperate and tropical spiny rock lobster species. Temperate species such as J.edwardsii have been shown to hatch larvae from the same brood of eggs over a possible eight consecutive nights ( Smith et al., 2002) as compared to a maximum of two nights for P.ornatus in this study. For temperate species, this gives greater flexibility in choosing either suitable larvae or a suitable stocking date when compared to tropical species. This also places greater importance on the accuracy of hatch modelling for tropical species as there are relatively fewer opportunities for larval collection when compared to temperate species.