Compensatory Growth of Pond-reared Hybrid Striped Bass, Morone chrysops×Morone saxatilis, Fingerlings

Compensatory growth (CG) or ‘‘catch-up growth’’ is a period of super-accelerated growth following a period of suboptimal conditions (i.e., lack of prey availability or overwintering). Little is known about the CG response in pond-raised fish and whether hybrid striped bass (HSB), Morone chrysops 3 Morone saxatilis, might exhibit the rapid growth states or improvements in other production characteristics that may accompany the response. To evaluate the potential for CG in HSB culture, a 16-wk growth trial in twelve 0.1-ha earthen ponds was conducted. Approximately 2850 fish (mean weight 6 SD 5 3.2 g 6 1.1) were stocked into ponds and subjected to one of four cyclic feeding regimens. Treatment regimens included a control (0 wk, fed twice daily to apparent satiation) and cycles of 1, 2, or 4 wk of feed deprivation, followed by 1, 2, or 4 wk of feeding to apparent satiation. Fish in the 4-wk feeding regimen were offered feed twice during the feed-deprivation period (once every other week). Growth, specific growth rate (SGR), hepatosomatic index (HSI), intraperitoneal fat ratio, and condition factor (CF) were measured every other week, while overall growth, feed efficiency (FE) (FE 5 [weight gain/feed fed] 3 100), and survival were calculated at the trial termination. The effect of these feeding regimens on water quality was examined by monitoring pH, turbidity, total ammonia nitrogen, nitrite–nitrogen, nitrate–nitrogen, soluble reactive phosphorus, and chlorophyll a weekly; total nitrogen and phosphorous biweekly; and dissolved oxygen and temperature twice daily. Cyclic feeding elicited CG; fish subjected to the 2-wk regimen had a significantly higher SGR than 0-wk controls during all but the final refeeding period. FE was higher for all fish in the cyclic regimens, although only FE for fish in the 2-wk regimen was statistically greater (40%) than the controls. HSI was the most responsive measure and significantly decreased in the 2and 4-wk treatments during feed-deprivation period and overcompensated during the refeeding period. CF also varied with feeding cycle and proved to be an effective nonlethal measure of predicting a CG response. No statistical differences in water quality parameters were observed. These data suggest that CG can be effectively induced in pond-raised HSB and that the increase in FE warrants further research for practical application. Future pond studies with fingerling HSB fish should be conducted with emphasis on feed-deprivation periods of 2 wk and refeeding periods of at least twice that of the feed-deprivation period. Hybrid striped bass (HSB), Morone chrysops 3 Morone saxatilis, culture is a major contributor to the US aquaculture industry, with total production for 2004 at 12 million pounds (Carlberg 2005). High costs of production and low fillet yield have slowed expansion (Carlberg 2005). Regulations on water usage and discharge could further negatively impact efforts to expand production and economic viability. Economic sustainability will therefore rely on the development of methods to reduce production costs and minimize environmental impacts. One potential means of improving production and management of water quality is to develop methods that take advantage of compensatory growth (CG). This response, also known as ‘‘catch-up’’ growth, is a physiological process whereby an organism exhibits accelerated growth after a period of restricted development, usually as a result of reduced feed intake, in 1 Corresponding author. JOURNAL OF THE WORLD AQUACULTURE SOCIETY Vol. 38, No. 2