SURVIVAL AND GROWTH OF STRIPED BASS, MORONE SAXATILIS, 



AND MORONE HYBRID LARVAE: 

 LABORATORY AND POND ENCLOSURE EXPERIMENTS 1 



Edward D. Houde 2 and Lawrence Lubbers IIP 



ABSTRACT 



Survival and growth of striped bass, Morone saxatilis, and its hybrids were compared in the first 30 

 days after hatching to determine if the reported heterosis of hybrid striped bass is evident in the larval 

 stage. Larvae of striped bass (SB); striped bass x white bass (WBX), M. saxatilis 9 x M . chrysops or; 

 and striped bass x white perch (WPX), M. saxatilis 9x1, americana c, were reared under controlled 

 conditions in the laboratory (19°C, 3°/oo) and under ambient conditions in freshwater pond enclosures. 

 In the laboratory SB had a significantly higher mean survival rate at 30 days of age than either hybrid. 

 In the pond enclosures neither mean survival nor size at 30 days differed significantly among the types 

 of larvae. Mean rates of growth in length, which ranged from 0.28 to 0.36 mm d" 1 in the laboratory 

 and from 0.30 to 0.32 mm d" 1 in the enclosures did not differ significantly among the types of larvae. 

 Mean rates of growth in weight of 15.0 to 19.0% d" 1 were not significantly different in the laboratory, 

 but the rates did differ significantly in the pond enclosures, where the WBX (17.9% d~ x ) and WPX (17.3% 

 d" 1 ) rates were significantly higher than the SB (15.5% d" 1 ). If 30-day-old fry were to be reared in 

 hatcheries, there is no clear production advantage for hybrids. A possible initial expression of hybrid 

 vigor, recognized by faster rates of growth in weight, was evident in WBX and WPX at 1 month of 

 age in the pond enclosures but not in the laboratory tanks. 



A series of recruitment failures (Cooper and Polgar 

 1981; Boreman and Austin 1985) has stimulated the 

 development of hatcheries to culture juvenile striped 

 bass, Morone saxatilis, or its hybrids for stocking 

 in the Chesapeake Bay region. The striped bass and 

 the striped bass x white bass, M. chrysops, hybrid 

 have been cultured for stocking in freshwater and 

 estuarine systems for several years and also have 

 potential for commercial aquaculture (Bonn et al. 

 1976; Kerby et al. 1983). A second hybrid, striped 

 bass x white perch, M. americana, has been pro- 

 duced (Bayless 1972; Kerby and Joseph 1979) 

 although its potential is less known. The striped bass 

 x white bass hybrid demonstrates an apparent 

 heterosis and usually grows and survives better dur- 

 ing the first two years of life than does striped bass 

 under similar culture conditions (Logan 1968; Ware 

 1975; Williams et al. 1981; Kerby et al. 1983). 



'Contribution No. 1721, Center for Environmental and Estuarine 

 Studies of the University of Maryland. 



2 University of Maryland, Center for Environmental and Estu- 

 arine Studies, Chesapeake Biological Laboratory, Solomons, MD 

 20688-0038. 



3 University of Maryland, Center for Environmental and Estu- 

 arine Studies, Chesapeake Biological Laboratory, Solomons, MD; 

 present address: Maryland Department of Natural Resources, 

 Tidewater Administration, Tawes State Office Building, Annapolis, 

 MD 21401. 



The objective of our experiments was to determine 

 if the apparent heterosis of the striped bass x white 

 bass hybrid is established in the larval stage, 

 between hatching and 30 d posthatch. We compared 

 growth and survival of striped bass, striped bass x 

 white bass, and striped bass x white perch (referred 

 to hereafter as "striped bass", "white bass hybrid", 

 and "white perch hybrid") in laboratory experiments 

 and in fine-mesh enclosures within hatchery ponds. 



METHODS 



Laboratory Experiments 



Larvae originated from eggs of a single female 

 striped bass, 15.4 kg, gillnetted in the Patuxent 

 River, transported to the Manning Hatchery, Cedar- 

 ville, MD, on 24 April 1982 and spawned by injec- 

 tion of human chorionic gonadotropin on 27 April. 

 Sperm from 2 male striped bass (Patuxent River), 

 12 male white bass (Tennessee Fish Commission), 

 and 2 male white perch (Patuxent River) were used 

 to fertilize portions of the spawned eggs. Embryos 

 were incubated in 114 L polyethylene incubation 

 chambers and larvae were held there in 15°-16°C 

 freshwater until 6 d after hatching when some were 

 brought to the Chesapeake Biological Laboratory. 



Manuscript accepted July 1986. 



FISHERY BULLETIN: VOL. 84, NO. 4, 1986. 



905 



