same for the two ranges. For the larvae collected in 

 1982, with an overall mean of 30.8 increments, the 

 mean difference was 1.67 increments (n = 71, stan- 

 dard deviation (SD) = 1.45). For the 1981 juvenile 

 collections, with overall mean of 109.5 increments, 

 the mean difference between the two estimates was 

 6.57 increments {n = 21, SD = 5.03). 



Growth rates of field-collected larval and juvenile 

 sablefish differ considerably. The data for the 1982 

 larval collections is described by the line 



SL = 0.375 (age, d) + 5.27 

 n = 71, r2 = 0.838, 



suggesting a mean growth rate for small larvae of 

 0.375 mnVd and an intercept of 5.27 mm, which coin- 

 cides with the size of newly hatched larvae (Mason et 

 al. 1983). Similarly the 1981 juvenile data is de- 

 scribed by the line 



SL = 1.469 (age, d) - 0.926 

 n = 21, r2 = 0.822, 



tain of these growth differences may have been a 

 function of gear selection. If net avoidance is a func- 

 tion of fish size, as for most other planktonic 

 organisms (Barkley 1972), then the oldest specimens 

 taken in the neuston gear may have been only the 

 slow-growing members of that cohort. Alternatively, 

 interruptions of increment formation, resulting in 

 underestimates of age, may occur. This has been 

 observed for some species by Geffen (1982). In the 

 laboratory specimens, however, one individual (L2 = 

 60.4 mm SL, Table 1) ceased eating for 5-6 d, 

 became emaciated, and died. The last five incre- 

 ments near the margin were smaller than the re- 

 mainder, but the 1 : 1 correspondence of days to incre- 

 ments suggests that increment formation continued. 

 Estimated age-at-length data from all years were 

 combined to describe the growth of sablefish to an 

 age of about 200 d. Comparing exponential, logistic, 

 and Laird-Gompertz growth models, the best fit (as 

 judged by residual sums of squares) was provided by 

 the Laird-Gompertz growth model (Fig. 3) in the 

 form: 



suggesting a mean growth rate of 1.47 mm/d. Cer- 



L( = L^{AJa){l - exp(- at)) 



280 



Figure 3. -Estimated age at length for all Aru/plorpcmm 

 fimbria in the study. Specimens taken in neuston nets (n = 

 84, including the 13 from 1983) are represented by circles, 

 1981 juvenile specimens from purse seine collections (n = 

 21) are represented by triangles. The equation and line 

 represent the least squares fit of the Laird-Gompertz 

 growth model. 



20 40 60 80 100 120 140 160 180 200 

 MEAN AGE (DAYS) 



478 



