Gonad development in farmed male and female South African abalone, Haliotis midae, fed artificial and natural diets under a range of husbandry conditions

Abstract

Growth rate is one of the most important factors in the farming of Haliotis midae, and somatic growth rates decline after abalone reach sexual maturity. Artificial diets are suspected to accelerate maturation, in particular when soya meal is used as a protein source, because of this plant’s high concentration of phytoestrogens. The effect of diet on the gonad development of 27-month-old farmed Haliotis midae, raised at two stocking densities, was analysed. We fed two artificial diets and a natural diet, kelp, to cultured abalone. The first artificial diet had fishmeal as its main source of protein, while in the other, Abfeed® S34, 32% of the fish meal was replaced with soya meal. For each gonad sample, the development phase was determined based on both histological criteria and the gonad bulk index (GBIn). The hypothesised link between dietary protein source and gonad development could not be established by either morphological criteria or GBIn. Similarly, stocking density did not have a significant effect on GBIn-values. GBIn values were significantly correlated to the results from the histological analyses in males and females. The results from this study suggest that artificial diets including those using soya meal are a valid alternative in the feeding of abalone. The research provides a database for future research on factors influencing gonad development in this species.