The Effects of Cyclic Feeding on Compensatory Growth and Water Quality in Hybrid Striped Bass, Morone chrysops x M. saxitilis.

Abstract

A series of pond and tanks studies were conducted to determine if compensatory growth (CG) could be elicited in hybrid striped bass (HSB; Morone chrysops x M. saxitilis) through manipulations in feeding that involve sequential cycles of feed deprivation followed by daily satiation feeding. Growth, feed efficiency (FE), hepatosomatic index (HSI), intraperitoneal fat ratio (IPF), and condition factor (CF) were assessed at intervals throughout the growth trials to characterize the nutritional status (catabolic state) and CG response of HSB. Measurements of pituitary growth hormone (GH) cell activity (gene expression, protein stores), and plasma GH were assessed in tank studies to identify the potential catabolic and anabolic role of this growth promoting hormone during feed deprivation and CG. Lastly, the effects of the cyclic feeding regimes on water quality were assessed in ponds trials. In each of the three studies, growth compensation, defined by growth rates that exceed that of control fish fed daily, was observed when treatment fish were realimentated to a control daily satiation feeding following a period of feed deprivation. Cyclic feeding increased overall FE of treatment fish over the controls by 10.8-40.0 % in the first pond study (HSB fingerlings), and 7.0-8.5% in the second pond study (HSB food fish) but not in the tank study. Hepatasomatic index and CF varied significantly with feed deprivation and refeeding, and were useful predictors of the CG response following feed deprivation. There was an inverse relationship between all GH measurements and nutritional status, with no reported compensatory changes in GH. Changes in water quality parameters due to cyclic feeding were only observed in the pond study with HSB food fish. Ponds subjected to the cyclic feeding regimes had 25-38 % lower levels of total phosphorus, 23.9-41.3 % less soluble reactive phosphorus, and 11.6-27.8% less chlorophyll-a. Based on these results, CG can be repeatedly induced in HSB in both ponds and tanks, albeit full growth compensation was not achieved under the cyclic feeding conditions used in these studies. Regardless, these studies suggest that cyclic feeding can improve overall FE and water quality in pond-raised HSB. Further studies are required to ascertain the optimal catabolic conditions needed to induce full growth compensation during HSB production.