Effects of larval stocking density on laboratory-scale and commercial-scale production of summer flounder Paralichthys dentatus

Three experiments investigating larval stocking densities of summer Rounder from hatch to metamorphosis, Paralichthys dentatus, were conducted at labo ratory-scale (75-L aquaria) and at commercial scale (1,000-L tanks). Experi ments 1 and 2 at commercial scale tested the densities of 10 and 60 larvae/ L, and 10, 20, and 30/L, respectively. The laboratory scale experiment test ed the densities of 10, 20, 30, and 40 larvae/L. Experiments were carried o ut in two separate filtered, Row-through seawater systems at URI Narraganse tt Bay Campus (laboratory-scale), and at GreatBay Aquafarms, Inc. (commerci al-scale). At both locations, the larvae were raised in a "greenwater" cult ure environment, and fed rotifers and brine shrimp nauplii according to fee ding regimes established for each location. Water temperature was maintaine d at 21C (+/- 2) and 19C (+/- 1) for the duration of laboratory and commerc ial experiments, respectively. Experiments 1 and 2 at the commercial locati on were terminated at 42 and 37 d post hatch (dph), respectively, and the l aboratory experiment lasted 34 DPH. Larvae initially stocked at 10/L grew t o an average length of 14.3 and 14.4 mm, and were significantly larger (P < 0.05) than those stocked at 30/L (13.1 mm) and 60/L (11.7 mm) in commercia l scale experiments 1 and 2, respectively. At laboratory scale, no signific ant differences in length were detected, although mean total length tended to decrease with increasing stocking density (average length of 14.2, 13.3, 12.7, and 12.7 mm for treatments of 10, 20, 30, and 40/L, respectively). F inal survival percentage was not affected by stocking density in either com mercial experiment, and was 61 and 40% for treatments of 10 and 60/L in Exp eriment 1, respectively, and 62, 59, and 56% for Experiment 2, respectively . Similarly, there was no significant difference in final survival percenta ge among treatments in the laboratory experiment, which averaged 59, 55, 56 , and 37% for treatments of 10, 20, 30, and 40/L, respectively. Since larva l length was not different between the intermediate densities (20 and 30 la rvae/L), and because high-density rearing can produce a much greater numeri cal yield per tank, we recommend a density of 30 larvae/L as an optimal sto cking density for the hatchery production of summer flounder.