GROWTH AND SURVIVAL OF SPISULA-SOLIDISSIMA SIMILIS LARVAE FED DIFFERENT RATIONS OF TAHITIAN STRAIN ISOCHRYSIS SPECIES

Laboratory-spawned veliger-stage larvae of the southern Atlantic surfc lam, Spisula solidissima similis (Say 1822), were reared to late pediv eliger stage on five different cell concentrations of Tahitian strain Isochrysis species (T-Iso) to determine an optimal food ration for thi s subspecies. Larvae were fed daily 0, 50,000, 100,000, 200,000, or 30 0,000 cells/mL of T-Iso. Day-old veliger larvae were stocked in 150 (I -L) replicate flasks at mean densities of 0.7 or 0.8 larvae/mL for tri als A and B, respectively. Larval growth and survival were assessed ev ery 2 days over the 14-day trial periods. Significantly greater growth and survival of larvae occurred in both trials in the lower food rati ons of 50,000 and 100,000 cells/mL. A reduction in larval growth rate and survival was observed at the higher ration treatments. A decline i n overall larval health may be associated with the deliterious effects of surplus ration degradation.