Effects of Stocking Density on Growth, Survival, and Stress Physiology of Pigfish

Abstract

AbstractStocking density is an important consideration in the intensive commercial production of fishes. Decreased growth and survival may result from overcrowding in the culture environment, while understocking may lead to inefficient use of resources. The Pigfish Orthopristis chrysoptera is a marine baitfish species with great potential for commercial production in the southeastern United States. To date, no studies have assessed the effect of culture density on Pigfish in recirculating aquaculture systems. Thus, we conducted two experiments to evaluate the effect of stocking density on Pigfish growth, survival, and stress physiology. The small‐scale trial included three densities—0.1, 0.3, and 0.5 fish/L (0.94, 2.82, and 4.70 kg/m3)—evaluated over the course of a 65‐d growth period. The large‐scale experiment encompassed four lower stocking densities—0.05, 0.1, 0.2, and 0.4 fish/L (0.10, 0.19, 0.38, and 0.76 kg/m3)—investigated over a 50‐d growth period. Growth, survival, specific growth rate, and feed conversion ratio were assessed for each treatment at the conclusion of the experiments. Additionally, plasma osmolality, chloride, cortisol, and glucose in Pigfish were evaluated at the completion of the large‐scale experiment. Trends in growth and survival were similar among most of the Pigfish densities tested. However, 50‐d survival was significantly lower in the 0.05‐fish/L treatment (mean±SD = 14.8±6.4%) than in the 0.2‐fish/L (37.6±11.6%) and 0.4‐fish/L (41.9±9.3%) treatments. Specific growth rate estimates ranged from 2.02±0.31% to 4.38±0.59% (mean±SD) during both trials. Differences in primary and secondary stress responses among treatments were generally unclear. Densities of up to 0.5 fish/L (4.70 kg/m3) appear to be conducive to the culture of juvenile Pigfish. Further research is needed to examine stocking densities greater than those investigated in this study. Results of physiological analyses represent the first published data on stress physiology in Pigfish.