mm 



Figure 2. - Sagitta otolith from a larval Anoplopomafiynbria (22.0 

 mm SL; duplicate increment counts were 37 and 40 d). Scale bar 

 = 0.1 mm. 



internal surface was ground until the focus was visi- 

 ble. The microscope slide was heated and the section 

 was turned over to expose the external surface. 

 Grinding and polishing continued, while care was 

 taken to insure that material was not lost from the 

 margin. The result was a clear, thin section of the 

 otolith in the sagittal plane. For some of the larger 

 juveniles (> 100 mm SL), transverse sections were 

 cut from the otoliths using a diamond saw, mounted 

 on microscope slides, and ground to make the incre- 

 ments clear. All otoliths were read under a com- 

 pound microscope at 400 x or 1,000 x magnifica- 

 tion. Two independent counts were made for each 

 otolith. These counts were made at least 2 wk apart; 

 the age assigned to each specimen was the mean of 

 the two counts. 



Increments, comprised of adjacent light and dark 

 ring pairs, were distinct and clear in the smallest 

 otoliths (Fig. 2), but interpretation became more dif- 

 ficult as the increments became progressively 

 smaller and as changes in growth patterns occurred 

 in the otolith structure of the older specimens. There 

 was no evidence of subdaily patterns in the incre- 

 ments, and each increment was assumed to repre- 



sent 1 d. Support for the daily deposition of incre- 

 ments was provided by data on three live juvenile 

 sablefish held in the laboratory (Table 1). The 

 specimens were captured by neuston net off 

 Newport, OR, and transported to the laboratory 

 where they were fed to satiation daily on Artemia. A 

 check, apparently associated with capture and 

 transfer to the laboratory, was evident on the otolith 

 of each fish. The numbers of increments past this 

 check corresponded closely to days captive; the 

 minor differences are attributed to counting error 

 and/or difficulty in interpretation of the check (Table 

 .1). We thus consider the increments to be deposited 

 with a daily periodicity. Hereafter increment counts 

 will be equated with days after first increment for- 

 mation; as we discuss later, first increment forma- 

 tion may occur at first feeding. 



Data from the 1982-83 larval collections and the 

 1981 juvenile collections were fitted separately with 

 simple linear regressions. Nonlinear curves (expo- 

 nential, logistic, and Laird-Gompertz) were fitted to 

 combined data with the NLIN procedure on the 

 SAS- statistical package (SAS Institute, Inc. 1982). 



Table 1. — Growth and increment formation in captive 

 specimens of Anoplopoma fimbria. L^, L2: standard length 

 (mm) at capture and death, respectively. 



Results and Discussion 



This study considers a total of 105 individuals, in- 

 cluding 71 larvae and juveniles (9.8 to 41.2 mm SL) 

 from the 1982 neuston collections, 21 juveniles 

 (102.8 to 259.6 mm SL) from the 1981 purse seine 

 collections, and 13 larvae (10.4 to 25.3 mm SL) taken 

 in the 1983 neuston collections. Mean increment 

 counts ranged from 9 increments for the youngest 

 larva to 180 increments for the oldest juvenile. The 

 abundance of larval sablefish in the neuston (Kendall 

 and Clark footnote 1) at such young ages suggests 

 that larvae move rapidly after hatching from the 

 deep spawning region rather than early growth oc- 

 curring at depths as suggested by Mason et al. 

 (1983). The difference between the two increment 

 counts for each otolith increased with increasing 

 count, but the coefficient of variation remained the 



^Reference to trade names does not imply endorsement by the Na- 

 tional Marine Fisheries Service, NOAA. 



477 



