Use of Primary Nursery Ponds for Red Snapper Larvae Culture and Associated Zooplankton Dynamics

Abstract

The challenge with red snapper aquaculture has centered around meeting the food requirements for larvae at the time of exogenous feeding. Snapper larvae demand sufficient quantities of small prey organisms at the onset of first-feeding. Copepod nauplii have proved to be an appropriate prey for red snapper larvae. In 2004 experiments were conducted to formulate red snapper culture methods using marine primary nursery ponds. Twenty 0.1 ha ponds were prepared with either 250 or 500 kg/ha rice bran organic fertilizer. Two day-old red snapper larvae were stocked in ponds at either 5, 7, or 10 days post-filling (dpf). At the end of 30 d the ponds were harvested. Zooplankton results showed high densities of copepod nauplii (averaging 774.65 ± 962.9 org/L) during the first 5 days following larval stocking in ponds receiving the 250 kg/ha fertilizer rate. These low rate ponds experienced significantly higher densities of nauplii than the 500 kg/ha ponds (p=0.021). A high degree of variation in nauplii abundance was observed between and within ponds during the study period. Average red snapper survival also varied greatly between treatments, ranging from nearly 0% survival in treatment 2 (250 kg/ha and stocked 7 dpf) to 1.07 % in treatment 5 (500 kg/ha, stocked 10 dpf, and continuous aeration). The treatment receiving 250 kg/ha of rice bran and stocked 10 days post-filling resulted in higher snapper survival when compared to the remaining low fertilizer treatments. Following these results recommendations for future research might suggest incorporating continuous aeration with the low rate fertilizer treatment and stocking larvae at 10 dpf. In addition to the pond study a computer model was constructed to predict the best day to stock red snapper determined by copepod nauplii density. The model used a forecasting method incorporating 29 pond parameters and resulted in an adjusted R² of 0.6954. The model was inconsistent at predicting nauplii abundance for 3 out-of-sample pond nauplii counts and therefore was not recommended as an appropriate management design. Alternatively, an empirical approach was evaluated to determine the number of ponds that would be needed to satisfy stocking requirements under conditions of uncertainty. This approach yielded more manageable results.