Abstract
As concerns regarding the growing human population, rising seafood demand, and up to present limited success of fisheries management intensify, aquaculture is increasingly posited as a means to more efficiently produce seafood commodities. However, aquaculture expansion raises contentious issues itself. The current study addresses a number of these issues in attempts to improve hatchery production and related activities. Investigation of less-harmful chemotherapeutants for disease reduction at the egg stage could lead to improved hatchery microbial management, increased survival during early larval stages, increased efficacy of bacterial probiotic incorporation, and reductions in disease transfer between hatcheries and locations. Attempts to surface sterilize and disinfect cobia Rachycentron canadum eggs with 3 and 2% hydrogen peroxide solutions significantly reduced survival through the yolk-sac larvae stage. Furthermore, timing of treatment application at differing stages of egg development was found to significantly impact survival, highlighting the importance of this compounding factor. Bacterial probiotics can remediate water quality, reduce target host stress, and improve survival and population growth rates of live feed organisms. Two of the following studies investigated the benefits of incorporation of a Bacillus spp. probiotic blend in aquaculture activities. During closed container mock shipment of yellowfin tuna Thunnus albacares yolk-sac larvae, significant reductions in total ammonia nitrogen resultant from probiotic incorporation were observed. Furthermore, significantly reduced dissolved oxygen utilization might have resulted from stress reduction, as suggested by a non-significant lower degree in the breakdown of osmoregulation of the larvae. Incorporation of probiotics within rotifer Brachionus plicatilis cultures resulted in significantly higher daily mean populations, significantly lower population variability among replicates, and non-coincident logistic population growth regressions which yielded higher population growth rates and system carrying capacities. Broodstock management should not only maximize quantity of reproductive output, but quality as well. Significant increases in cobia egg diameter with increasing broodstock female age were detected, as well as significant increases in egg diameter with decreasing salinity. Confirmation of potentially increased larval growth rates resultant from increased energy stores of larger eggs when produced by older females, as demonstrated in other species, is warranted. Attempts to find production parameters which maximize cobia larval growth and survival would lead to increased sustainability via reducing demand for wild-collected Artemia and economic efficiency. Gaps in knowledge for achieving this goal continue to exist, but conclusions drawn from analysis of multiple production scale trials indicate temperatures of 29-31 °C maximize growth and survival. Improvement in sampling design and data analysis would increase statistical rigor and ease comparability of larvicultures outcomes across ranging influential factors. Further investigation of all of these matters is certainly warranted, although conclusions drawn could be effectively utilized to improve success of hatchery operations.