GROWTH AND BODY-COMPOSITION OF POND-RAISED HYBRID STRIPED BASSES, MORONE-SAXATILIS X MORONE-CHRYSOPS AND MORONE-SAXATILIS X M-MISSISSIPPIENSIS, FED LOW AND MODERATE LEVELS OF DIETARY-LIPID

Differences in growth of original-cross hybrid striped bass and striped bass X yellow bass hybrids have been documented in tank-reared fish. This experiment was conducted to compare growth and body composition of hybrids raised in ponds, and determine the extent to which growth and body lipid content was influenced by addition of a fish oil top-spray to the diet. Sixteen 0.04-ha earthen ponds were stocked with 300 fingerling striped bass hybrids per pond-8 ponds with a striped bass female X white bass male hybrid (SB X WB) and 8 with a striped bass female X yellow bass male hybrid (SB X YB). The two hybrids were hand-fed to apparent satiation, once daily, with either a menhaden-oil-supplemented diet (OSD; 6.78% total lipid) or a diet with no oil supplement (USD; 4.12% total lipid). Fish were harvested after 295 days. Mean production yields were 3974 kg/ha for SB X WB hybrids fed OSD; 3629 kg/ha for SB X WB hybrids fed USD; 2462 kg/ha for SB X YB hybrids fed OSD; and 2048 kg/ha for SB X YB hybrids fed USD. Weight gains of SB X WB hybrids fed oil-supplemented and unsupplemented diets were higher than weight gains of SB X YB hybrids fed either diet. Weight gain, feed efficiency ratio, and dietary protein and energy retention of SB X WB hybrids did not differ significantly among fish fed oil-supplemented or unsupplemented diets. However, SB X YB hybrids fed OSD had lower dietary protein and energy retention than those fed USD. Percentages of lipid in whole body and fillets of both hybrids increased with time, regardless of diet fed, but lipid content of fish did not differ among treatments. Fillet yield did not differ between SB X WB and SB X YB hybrids or among fish fed either diet. Results indicated that (1) SB X WB hybrids produced higher yields in ponds than SB X YB hybrids, and (2) increasing the dietary lipid level above 4% had no beneficial effect on production, feed efficiency, or body composition of either hybrid. A low-lipid practical diet of the type used in this study was suitable for production of SB X WB and SB X YB hybrids in ponds.