562 



Fishery Bulletin 88(3), 1990 



Figure 6 



Low-magnification scanning electron micrograph of a sagittal otolith of Notothenwpf! nvdifrorif^, showing concentric 

 incremental patterns. The sagitta is from a lOO-mmSL specimen. 



not appear to affect the fish's metabolism. Linear re- 

 gression results indicated a slope of 0.962 (95% CI of 

 0.983-0.941) and a (/-intercept of -5.40 (95% CI of 

 -2.80 to -8.01). The significance of this analysis is 

 suspect because of the small sample size (A'^ = 5). The 

 discrepancy between postinjection days and microin- 

 crements counted increased from 5 to 12 with length 

 of incubation period. However, this apparent increase 

 in the discrepancy represents an actual percentage 

 decrease in error from 50% to less than 10%. The 

 longest incubation period in the acetazolamide experi- 

 ment was 158 days, which was three times longer than 

 the longest tetracycline incubation. This may explain 

 why in the tetracycline experiment we did not observe 

 an increase in the discrepancy between number of in- 

 crements and days after injection. 



During the experiment, the photoperiod varied from 

 9:15 hours Light:Dark, to a minimum of 5:19 L:D in 

 June, to 15:9 L:D in October. The microincrements 

 formed during incubation were uniform. Despite con- 

 siderable variation in photoperiod, we found no indica- 

 tion that microincrements cease to form on a daily 

 basis. 



Age and growth 



Microincrements were counted in the sagittal otoliths 

 of 32 fishes. Ages ranged from 1.3 years for the small 

 juveniles collected by hand, to 8.5 years for the largest 

 individual collected. Fish length was related to the 

 number of microincrements in the sagitta (Fig. 10). 

 Length (mm) increased linearly with age (years), and 

 was best described by the equation: 



SL = 14.87(Age) -t- 23.56; (R- = 0.93, /KO.OOOl) 



No difference in growth was observed between the 

 sexes in our sample (Fig. 10). When separate regres- 

 sions were calculated for males (A^= 11) and females 



Figure 7 



(a) Scanning electron micrograph of a .sagittal otolith of a 

 1.30-mmSL Notolkeniops nudifrons, showing the characteristic 

 central core area, or nucleus, separated by a well-defined transi- 

 tional zone from the outer zone with microincrements radiating 

 outward, (b) Microincrements from a 100-mmSL fish found 

 within the core area of the otolith. 



