FISHERY BULLETIN: VOL. 80, NO. 1 



70 



50 



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 I 



a; 



1 



5 



25 



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Mi. . 



7"7' \ 



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5 10 15 



STANDARD LENGTH (mm) 



20 



FIGURE 4.— Number of otolith growth increments related to 

 standard length of 338 larval and transforming, field-caught 

 Parophrys vetulus. 



Our description of early growth of P. vetulus in 

 Oregon coastal waters at temperatures ranging 

 from 9° to 11°C is based on the ages and lengths 

 of 331 specimens, 3.1-20.0 mm SL, with otolith 

 growth increments. Gompertz and von Berta- 

 lanffy models yielded good and nearly identical 

 fits to the data and similar estimates of growth 

 rate; therefore, the results of only one model 

 (Gompertz) are presented (Table 3; Fig. 5). 

 RSS and linear estimate RSS of the Gom- 

 pertz growth parameters were very similar; 

 thus, the assumption of linearity in computing 

 95% confidence limits is reasonable, and the 

 computed limits indicate relatively narrow con- 

 fidence regions around the parameters (Table 



3). 



Previous estimates of age at length of larval 

 P. vetulus were derived from the progression of 



modes in length-frequency distributions of 

 larvae from a time series of (10% Formalin pre- 

 served) plankton samples (Laroche and Richard- 

 son 1979). A comparison of those results with age 

 at length estimated by the Gompertz equation 

 (Zwiefel and Lasker 1976) indicates that the 

 length-frequency method overestimated the age 

 of larvae >5.5 mm SL by 2-3 times (Table 4). 



Estimates of specific and absolute rates of 

 growth were calculated from length at age for 

 various ages as predicted by the Gompertz model 

 (Table 5). Specific growth rate steadily de- 

 creased between 8 and 74 d. Absolute growth 

 rate was fairly uniform between 8 and 31 d, 

 slowed somewhat between 31 and 41 d, but was 

 more drastically reduced between 73 and 74 d, at 

 which time larvae undergo transformation, a 



Table 3.— Gompertz equation and estimated parameters 

 describing the growth of 331 Parophrys vetulus larvae in 

 Oregon waters during the 1977-78 spawning season. RSS = 

 residual sum of squares; SE = standard error of the regres- 

 sion; S 2 = variance; CL = confidence limits. 



Table 4.— Age of Parophrys vetulus larvae; (A) 

 estimated from modal progression in length-frequency 

 distributions of larvae caught during 1971 in biweekly 

 and weekly Formalin-preserved plankton samples 

 (Laroche and Richardson 1979), (B) estimated by the 

 Gompertz equation based on otolith increment counts 

 from ethanol-preserved larvae caught in 1977-78. 



Estimated age (weeks) 



SL (mm) 



5.5 

 7.5 



95 

 11.5 

 13.5 

 15.5 

 17.5 



Table 5.— Growth rates of Parophrys vetulus larvae predicted 

 from the Gompertz equation at various times from hatching. 



100 



