TABLE 13. Annual median densities (number per 500 m ) of winter flounder larvae in entrainment samples 

 during their season of occurrence and total entrainment estimates with approximate 95% confidence intervals for 

 MNPS in 1976 through 1987. 



61% and 62%; and Stage 4, 15% and 8%. The 

 proportion of each developmental stage entrained 

 was similar to previous years with Stage 3 pre- 

 dominating (NUSCO 1987). 



The 1 2 years of entrainment sampling provided 

 a long time-series of data that were examined to 

 determine if seasonal water temperatures affected 

 the timing of peak abundance. Seasonal water 

 temperatures were expressed as the deviation from 

 the 12- year mean. The date of peak abundance 

 was highly correlated to water temperatures during 

 March and April (Fig. 21). The warmer the water 

 temperature, the earlier the peak that occurred, 

 which suggested that the rate of larval development 

 increased with increasing temperature. This was 

 in agreement with the findings of Laurence (1975), 

 who found that winter flounder larvae metamor- 

 phosed 31 days earlier at 8°C than at 5°C. 



The date of peak abundance, estimated from 

 the inflection point of the Gompertz function. 



was calculated using the p and K parameters. The 

 K parameter was correlated to February water 

 temperatures and as temperatures decreased, the 

 parameter declined (Fig. 22). The K parmeter 

 determined the shape of the abundance curve with 

 steeply peaked curves for larger K values. To 

 demonstrate how the this parameter affects abun- 

 dance distribution, abundance curves were simu- 

 lated with two different K values, but with the 

 same a and P values (Fig. 23). For winter floun- 

 der, February water temperatures would primarily 

 affect spawning and egg incubation, because peak 

 larval abundance occurs later (Table 12). A sig- 

 nificant relationship was found between the annual 

 K value and the age 3 recruitment indices that 

 were used for the analysis of stock and recruitment 

 (Fig. 24). It appeared that the shape of the larval 

 abundance curve, as determined by February wa- 

 ter temperature, was important in determining 

 year-class strength, although the actual causal 

 mechanisms were not known. 



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