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AND D. ORTMANN. 



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 Hunter, M. A. 



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J. P. Fisher 

 W C Pearcy 



College of Oceanography 

 Oregon State University 

 Corvallis, OR 97331 



DAILY GROWTH INCREMENTS IN OTOLITHS 



OF JUVENILE BLACK ROCKFISH, 



SEBASTES MELANOPS: AN EVALUATION OF 



AUTORADIOGRAPHY AS A NEW METHOD 



OF VALIDATION 



Investigations into the temporal periodicity of 

 growth increment formation in otoliths of larval 

 and juvenile fishes have produced conflicting ac- 

 counts. Taubert and Coble (1977), Barkman 

 (1978), Wild and Foreman (1980), and Campana 

 and Neilson (1982), among others, have con- 

 firmed daily increment formation in otoliths from 

 various species of larval and juvenile fishes. 

 There have been a few studies, however, in which 

 increment counts were not representative of ac- 

 tual age of the fish (Wild and Foreman 1980; Gef- 

 fen 1982; Neilson and Geen 1982). Nondaily in- 

 crement formation has been explained by the 

 inclusion of subdaily rings in age estimates as 

 well as by methodological errors in preparing and 

 viewing the otoliths (Campana 1983a; Campana 

 and Neilson 1985). Since size and age offish, food 

 limitations, and environmental conditions have 

 been suggested to affect increment formation, 

 validation is necessary in each study where fish 

 age is estimated. 



Several techniques have been used to validate 

 daily growth increments in larval and juvenile 

 fish otoliths. Fish of known age, raised from fer- 

 tilization or birth under controlled laboratory 

 conditions, provide the best material to determine 

 frequency of increment formation (Taubert and 

 Coble 1977; Barkman 1978; Tanaka et al. 1981; 

 Miller and Storck 1982). For many species, how- 

 ever, rearing the larvae from birth through the 

 juvenile stage is difficult or impossible. An alter- 

 nate method of age validation introduces a chem- 

 ical mark onto those calcified structures which 

 exhibit periodic growth zones, such as otoliths, 

 scales, and spines. The antibiotic oxytetracycline 

 hydrochloride (OTC) has been used most success- 

 fully in this manner (Wild and Foreman 1980; 

 Campana and Neilson 1982; Ralston and 

 Miyamoto 1983; Dabrowski and Tsukamoto 

 1986). The OTC is taken up at the site of calcifica- 

 tion and fluoresces bright yellow under ultravio- 

 let light, compared with the blue autofluores- 

 cence of normal tissue. Most recently, stable 

 strontium has been used to demonstrate daily in- 

 crement formation in squid statoliths (Hurley et 

 al. 1985) and in mass marking of coho salmon 

 (Yamada et al. 1979). For some species, a time- 

 mark may also be induced on the otolith by stress, 



826 



FISHERY BULLETIN: VOL. 85, NO. 4, 1987. 



