Abstract. — Factors that affect 

 survival and growth of larvae and 

 influence recruitment variability of 

 striped bass, Morone saxatilis, 

 were investigated in the Potomac 

 River and Upper Chesapeake Bay 

 from 1987 to 1989. Ages and growth 

 rates of larvae hatched within 3- 

 day periods (cohorts) were esti- 

 mated from otolith daily incre- 

 ments. Cohort-specific mortality 

 rates were estimated from declines 

 in cohort abundances over time. 

 Temperature strongly affected lar- 

 val cohort dynamics and potential 

 to recruit. Storm fronts caused 

 water temperature to drop near to 

 or below 12°C, resulting in episodic 

 mortalities of eggs and newly 

 hatched larvae. Cohort-specific 

 growth rates of larvae were vari- 

 able, ranging from 0.11 to 0.46 

 mm-d -1 in the Potomac and from 

 0.18 to 0.36 mm d" 1 in the Upper 

 Bay, and were positively correlated 

 with mean water temperatures. 

 Cohort instantaneous mortalities 

 (d~M also ranged widely, from Z = 

 0.05 to 0.92 in the Potomac and 

 from Z = 0.02 to 0.28 in the Upper 

 Bay, but were not correlated with 

 temperature, growth rate, or other 

 measured variables. The medians 

 of cohort G/Z ratios (ratios of 

 weight-specific growth rate to in- 

 stantaneous mortality rate) and 

 productions of 8.0-mm standard 

 length larvae in each year were 

 positively correlated with juvenile 

 recruitment indices. Larval produc- 

 tions at 8.0 mm also were positively 

 correlated with mean water tem- 

 peratures because temperature 

 strongly affected larval growth and 

 because of the strong selection for 

 survival of cohorts hatched later in 

 the spawning seasons when water 

 temperatures were consistently 

 >17°C. 



The influence of temperature on 

 cohort-specific growth, survival, 

 and recruitment of striped bass, 

 Morone saxatilis, larvae in 

 Chesapeake Bay 



Edward S. Rutherford 



Chesapeake Biological Laboratory 



Center for Environmental and Estuanne Sciences 



University of Maryland, 1 Williams St., Solomons, MD 20688 



Present address: Institute for Fisheries Research 



Michigan Department of Natural Resources 



2 1 2 Museums Annex Bldg.. II 09 N University St. 



Ann Arbor, Ml 48 1 09 



Edward D. Houde 



Chesapeake Biological Laboratory 



Center for Environmental and Estuarine Sciences 



University of Maryland, 1 Williams St., Solomons, MD 20688 



Manuscript accepted 17 October 1994. 

 Fishery Bulletin 93:315-332 (1995). 



Landings of anadromous striped 

 bass, Morone saxatilis, along the 

 Atlantic Coast of the United States 

 declined sharply in the 1970's and 

 1980s owing to overfishing and a 

 series of poor recruitments (Bore- 

 man and Austin, 1985). Indices of 

 striped bass recruitments in the 

 Chesapeake Bay vary more than 

 100-fold (Schaefer et al. 1 ). Recruit- 

 ment levels are established by the 

 juvenile stage, when seine-survey 

 indices correlate with subsequent 

 commercial catches of adults (Good- 

 year, 1985). 



Striped bass spawn in Chesa- 

 peake Bay tributaries from April to 

 June, when frequent storms and 

 heavy rainfall cause temperature, 

 river flow, and pH levels to fluctu- 

 ate. Temperatures experienced by 

 eggs and larvae during the two- 

 month spawning season may range 

 from 10 to 29°C and may have dra- 

 matic effects on production, sur- 

 vival, and growth of cohorts. Initia- 

 tion of spawning in Chesapeake Bay 



tributaries occurs at 12-18°C when 

 temperatures are increasing rapidly 

 (Olney et al., 1991; Setzler-Hamil- 

 ton and Hall, 1991; Setzler Hamil- 

 ton et al. 2 ). Rapid drops in tempera- 

 ture to below 12°C are lethal to 

 striped bass eggs and larvae (Bar- 



1 Schaefer, R. K., R. H. Bradford, J. L. 

 Markham, and H. T. Hornick. 1991. Char- 

 acterization of striped bass stocks in Mary- 

 land, p. 1-74. In H. T. Hornick (project 

 leader), Investigation of striped bass in 

 Chesapeake Bay. US Fish and Wildlife 

 Serv. Fed. Aid Proj. F-42-R-3, MD Dep. 

 Natl. Resour., Tidewater Admin., Annapo- 

 lis, MD. Available: Maryland Department 

 of Natural Resources, Tidewater Admin- 

 istration, Tawes State Office Bldg., Taylor 

 Ave., Annapolis, MD 20688. 



2 Setzler-Hamilton, E. M., J. A. Mihursky, 

 K. V. Wood, W. R. Boynton. D. Shelton, M. 

 Homer, S. King, and W. Caplins. 1980. 

 Potomac estuary fisheries program, 

 ichthyoplankton and juvenile investiga- 

 tions. 1977 Final Rep. to Maryland Dep. 

 Natl. Resour., Power Plant Siting Program. 

 Univ. of Maryland. Ref. No. [UMCEES]CBL 

 79-202. Available: University of Maryland 

 Center for Environmental and Estuarine 

 Studies, Chesapeake Biological Labora- 

 tory, 1 Williams St., Solomons, MD 20688. 



315 



