The larval phase of marine fish is one the most challenging stages of production. Small mouth gapes and historical poor performance on exclusively artificial diets have resulted in feeding regimes that rely heavily on live zooplankton, primarily rotifers and Artemia. Effective culture protocols have facilitated the incorporation of Artemia into larval feeding regimes, but recent issues with supply, demand, cost, and other concerns have warranted investigation into reducing or eliminating the amount of Artemia in feeding regimes. As Artemia are usually the live prey item fed before or during weaning onto artificial micro diets, partial or complete reductions in either the period of time Artemia are fed or overall daily amounts fed during weaning could result in cost savings and also simplify larval culture protocols. Thus, the objective of this experiment was to evaluate the potential to reduce Artemia levels during the larval phase of different marine batifish- spot (Leiostomus xanthurus), pinfish (Lagodon rhomboides), and pigfish (Orthopristis chrysoptera).
Eggs for each of the three species were obtained from conditioned, captive broodfish at the Waddell Mariculture Center in Bluffton, South Carolina. Larvae were batch-cultured under standard conditions in 140-L tanks in-line with a recirculating aquaculture system utilizing best culture practices available for each species until the day at which Artemia feedings were to begin (approximately 17 days post hatch). The morning Artemia were to be fed, larvae were redistributed into new 140-L tanks at 250 larvae per tank. Two trials were conducted for each species and 17 tanks were stocked each trial to generate one starvation tank (negative control) and 16 experimental tanks (4 tanks per treatment). The first trial examined feeding Artemia at reduced rates (66%, 33%, and 0%) compared to a standard satiation ration (100%) and supplementing the reduced rations with a 1:1:1:1 mix of micro diets (Otohime A and B1, and ArteMac No.2 and EconMac No.2) fed five times per day at 0.5 g per feeding. The second trial examined feeding a standard satiation ration (100%) for different durations (2, 4, 8, and 14 days) with acute switches to the 1:1:1:1 mix of micro diets fed five times per days at 0.5 g per feeding the day after Artemia feedings ended. Experiments were conducted for 14 days and larval survival of each tank along with larval growth (n ≤ 25 larvae per tank) were recorded.
For spot, reductions of Artemia in both a daily ration and total duration fed resulted in significant decreases in survival and growth (e.g. 47.1±1.6% compared to 33.2±.5% for a 100% and 0% ration, respectively). However, larvae were still able to be produced without using any Artemia at all or only for a duration of two days. Thus, future refinement of micro diets and the regime