Rutherford and Houde: The influence of temperature on growth of Morone saxatilis 



325 



Potomac River 1987 



Potomac River 1989 



0.5- 

 



Potomac River 1988 



Upper Bay 1989 



Cohnrl Hatch Dale 



Cullort Hatch Date 



Figure 9 



Cohort-specific, instantaneous daily mortality rates (Z, •) and G/Z ratios (bars) of striped 

 bass, Morone saxatilis, larvae by hatch date from the Potomac River, 1987-89, and Upper Bay, 

 1989. Error bars on mortality rates indicate 1 standard error of mean. Scale on Y-axis varies 

 among panels. 



related to cohort growth rates, and in the Upper Bay to 

 water temperature. The relationships are 



for the Potomac River, 



Ln(iV 8 ) = 6.43 + 31.43 (G); (r 2 =0.22, P<0.01, re=28) 



for the Upper Bay, 



Lnl/Vg) = -36.65 + 4.75 (T) - 0.11 (T 2 ); (r 2 =0.91, 



P<.001, 72 = 12) 



where ln(./V 8 ) is the log e -transformed cohort production 

 of 8-mm-SL larvae, G=cohort growth rate ( mm-d" 1 ) and 

 T=mean temperature experienced by the cohort from 

 5-20 days posthatch. In the Potomac River, cohort 

 larval productions at 8 mm SL also tended to be posi- 

 tively correlated with water temperature, but the 

 correlation was not significant (P>0.10). In the Up- 

 per Bay, cohort production at 8 mm SL was not cor- 

 related with cohort growth rate (P>0.50). 



The relative cohort abundances of larvae collected 

 in the 2-m 2 Tucker trawl on the last day of the sam- 



pling season, standardized to 8-mm-SL productions 

 from cohort-specific stage durations and survival 

 rates, provided another indicator of larval survival 

 and potential recruitment. Tucker trawl catches in 

 the Potomac River on 4-5 June 1987 indicated that 

 surviving cohorts, which potentially contributed to 

 recruitment, were hatched from 22 April to 19 May 

 and that most survivors hatched in the 22-25 April 

 and 4-10 May periods (Fig. 11A). In 1988, Tucker 

 trawl catches on 2-3 June indicated that surviving 

 8-mm larvae were hatched from 3 May to 30 May 

 and that most hatched during the 18-24 May period 

 (Fig. 11B). The 1989 Tucker trawl index of 8-mm lar- 

 vae on 8-9 June suggested that, while some poten- 

 tial recruits were hatched in every 3-day period from 

 20 April to 23 May (Fig. 11C), cohorts hatched on 20 

 April and 14 and 17 May accounted for >809r of the 

 total numbers represented on 8 June. 



Relative cohort abundances of 8-mm larvae in the 

 Upper Bay on the last sampling day in 1989 ( 14 June) 

 indicated that potential recruits were hatched from 

 5 May to 4 June (Fig. 11D). More than 80% of these 

 larvae were hatched between 14 May and 1 June. 



