A series of three feeding trials investigating different feed types (live and fresh-frozen polychaetes, fresh-frozen squid and mussel, and commercially available formulated moist feed) and feeding ration (apparent satiation vs 50% restriction) and their effects on the hepatopancreas composition and reproductive performance of females broodstock P. monodon were carried out at CSIRO’s prawn broodstock facility at Bribie Island Research Centre.
Trial 1 compared three diets including (1) a control composed of live polychaetes and fresh-frozen squid and mussel, (2) same live and fresh-frozen ingredients supplemented with a commercial moist feed (EZ Mate), and (3) the latter supplemented with cordyceps. Trial 2 tested two feeding rations with animals housed individually fed to apparent satiation and 50% restriction. Additional control treatment consisted of animals housed in a traditional communal tank fed to apparent satiation was added for comparative purposes. Trial 3 investigated the relevance of live polychaetes by replacing them with fresh-frozen squid at 100, 50 and 25% levels.
In trial 1, dietary treatments did not affect ovarian development parameters (ovarian stage on the day of eyestalk ablation, percentage of females reaching ovarian stage 3 and 4, and stage 3 that continued developing to stage 4 in the reproductive period) and spawning parameters (percentage of females spawning, numbers of spawning per female, egg numbers per spawning event, percentage of spawnings that hatched, nauplii numbers per hatching spawning, and percentage of nauplii hatching per hatching spawning). Modest replacement of live and fresh-frozen ingredients with commercial moist feed supplemented or not with cordyceps did not reduce or enhance reproductive outcomes. Trial 2 validated the individual housing approach compared to a standard communal tank for research purposes. No significant effects of feeding ration on ovarian development were observed, likely due to the lack of eyestalk ablation and high biological variability. Trial 3 supported the hypothesis about the relevance of live polychaetes in broodstock maturation in the context of feeding at the expense of or in combination with fresh-frozen squid. Feeding 100% fresh-frozen squid impaired reproductive outcomes, while a ratio of 50% live polychaetes and 50% fresh-frozen squid corrected this effect equally performing to 100% live polychaetes in the context of females’ reproductive performance.
Details of the differences or lack of them in each experiment will be discussed. Collectively, these findings provide valuable insights into the broodstock and hatchery prawn industry.