COVARIATION BETWEEN GROWTH AND MORPHOLOGY SUGGESTS ALTERNATIVE SIZE LIMITS FOR THE BLACKLIP ABALONE, HALIOTIS-RUBRA, IN NEW-SOUTH-WALES, AUSTRALIA

Growth of the blacklip abalone, Haliotis rubra, was estimated from 1,464 individuals that were tagged and left at large for up to five years at seven sites in New South Wales, Australia. Both the shape of the fitted growth curves and the average growth rates differed significantly among sites, separated by only 1-20 km. There was also significant variation in the growth of individual abalone within sites and this variation differed among sites. Abalone at sites where they grew quickly reached larger lengths and were morphologically different from those at sites where they grew slowly. For example, the shells of abalone from sites where they grew slowly were wider and heavier at a given length than those from sites where they grew quickly. The implication that rates of growth in width are less variable than growth in length suggests that a minimum legal width limit may be more appropriate than the present size limit that is based on length. A minimum legal width limit would redistribute fishing effort away from sites where abalone grow in length quickly towards sites where they grow slowly, including sites which are presently unfished because few individuals reach the minimum legal length. If this were possible, it would reduce the differences in exploitation among sites which, at present, have the potential to seriously deplete populations at sites where individuals grow quickly.