Culture of triploid greenlip abalone (Haliotis laevigata Donovan) to market size: Commercial implications

Triploid greenlip abalone (Haliotis laevigata) were produced via a 15 min exposure to 100 μM 6-dimethylaminopurine at 20 min post-fertilization and grown under commercial conditions for up to 48 months. Differential mortality of the ploidy classes resulted in a decline in the proportion of triploid abalone from 83% in trochophores (2 h post-hatch), 55% in post-larvae (29 days post-hatch) and 50% in adults. A random sample of 540 juvenile triploid and diploid abalone from the same cohort were tagged, biopsied (for ploidy determination), weighed and measured at 13 months. Measurements of the tagged abalone for growth were recorded at 17, 25, 32, 36, 39, 42, and 48 months, and sampling for meat yield performed at 36, 42 and 48 months. There were significant differences in the length and weight of diploid and triploid abalone by 13 months, with the latter being impaired by the equivalent of 23 to 25 days growth by this time. Comparisons of growth from 13 to 48 months showed that diploid abalone were consistently 11–15% longer than their triploid siblings. However, larger triploid abalone yielded up to 30% higher meat weight than diploid abalone of comparable length during the spring–summer maturation periods (at 36 and 48 months), making harvesting of triploid abalone for canned product at this time cost effective. Diploid abalone exhibited compensatory growth and had meat weights comparable to those of triploids between the maturation periods (at 42 months). The fatty acid composition of the meat from 48 month old greenlip abalone was not affected by ploidy, maturity or sex. Half of the triploid abalone were male and most of the remainder did not develop gonad. Attempts to spawn triploid abalone were unsuccessful as females did not mature and those males which did mature, failed to respond to artificial spawning stimuli.