accumulation to the edge of the otoHth. The pos- 

 terodorsal area of the sagittal sections showed the 

 heaviest accumulation of the isotope and was also 

 the easiest area in which to count increments. 

 This observation is consistent with Irie (1960) 

 and Mugiya (1974), who concluded that high cal- 

 cium uptake occurred in the dorsal region, as well 

 as in the anterior and posterior tips of otoliths; 

 these are the regions of fastest otolith growth. 



The number of growth increments from the 

 band of densest accumulation of silver grains to 

 the edge of the otolith section closely approxi- 

 mated the number of days the fish were held in 

 the laboratory following injection (Table 1), 

 thereby validating the occurrence of daily growth 

 increments in these juvenile black rockfish. Vali- 

 dation of the frequency of growth increment for- 

 mation, obtained from fish held under optimal 

 growth conditions in the laboratory, and the ap- 

 parent lack of otolith resorption, as demonstrated 

 by the increasing retention of calcium-45 with 

 time, suggest that daily increments on otoliths 

 could provide accurate representation of age 

 and growth for field-caught juvenile Sebastes 

 melanops. Daily increments have recently been 

 suggested to occur on otoliths of early larvae of 

 S. marinus (Penny and Evans 1985). In previous 

 work on juvenile Sebastes, growth increments 

 had been counted but not validated (Moser and 

 Ahlstrom 1978; Boehlert 1981). Our study is thus 

 the first confirmation of daily increments on 

 otoliths of juvenile Sebastes. 



Checks, or exceptionally dense and dark bands 



Table 1 . — Age validation using otoliths from black rockfish marked 

 with calcium-45 or oxytetracycline. Number of days from capture to 

 injection is compared with number of growth increments from cap- 

 ture check to time-mark; number of days from injection to sacrifice 

 is compared with number of increments from time-mark to margin 

 of otolith. 



1 Scattered silver grains associated with margin. 

 830 



deposited as daily increments, were observed in 

 otoliths from fish used in the calcium-45 experi- 

 ments. One check preceded the radioactive time- 

 mark and another check was associated with the 

 time-mark itself Ten growth increments were 

 noted from the earliest check to the time-mark in 

 each otolith (Table 1). Formations of checks in 

 otoliths have been documented for many species, 

 including coho salmon (Campana 1983b), goldfish 

 (Mugiya and Muramatsu 1982), and several trop- 

 ical species (Brothers et al. 1983). Such checks 

 have been attributed to periods of physiological 

 stress to the fish due to collection, migration, 

 change in feeding or habitat, temperature, life 

 history stages, or anything else that disrupts 

 growth. In the present study, the time from fish 

 collection to injection of the isotope marker was 

 10 days (Table 1). It seems clear that the observed 

 checks were produced as a consequence of stress 

 encountered during capture and transport to lab- 

 oratory conditions and can be used as additional 

 evidence of daily deposition of growth increments. 

 If such checks are reliably produced, they may be 

 better than chemical time-markers for validation 

 studies such as these. 



Oxytetracycline 



The OTC was incorporated into the otoliths of 

 each of the 15 fish injected and produced a distinct 

 fluorescent band. The growth increments follow- 

 ing injection of OTC, however, were less distinct 

 on most of the otoliths and consequently all 

 otoliths could not be used to validate daily incre- 

 ment formation. Weak increment definition fol- 

 lowing OTC incorporation in otoliths of larval 

 spot and pinfish has been reported by Hettler 

 (1984). Although Hettler suggested that the lack 

 of distinct increments resulted from experimental 

 stress, postinjection increments were clearly visi- 

 ble in otoliths from the juvenile rockfish which 

 were injected with calcium-45 and held under lab- 

 oratory conditions similar to the OTC experi- 

 ments. Five of the rockfish otoliths did display 

 clear growth bands following the fluorescent 

 time-mark; enumeration of these increments is 

 summarized in Table 1. These otoliths show the 

 same results as those from calcium-45 treat- 

 ments, demonstrating the daily periodicity of 

 growth increment formation in juvenile black 

 rockfish. It is unclear, however, why 67% of the 

 otoliths failed to produce prominent daily incre- 

 ments after OTC incorporation. 



The fluorescent OTC mark was more intense 



