ANALYSIS OF AGE DETERMINATION METHODS FOR 



YELLOWTAIL ROCKFISH, CANARY ROCKFISH, 



AND BLACK ROCKFISH OFF OREGON 1 



Lawrence D. Six 2 and Howard F. Horton 3 



ABSTRACT 



Age determination methods and their application are presented for yellowtail rockfish, Sebastes 

 flavidus; canary rockfish, S. pinniger; and black rockfish, S. melanops, collected off Oregon during 

 1972-75. Of 25 anatomical structures examined, those compared for consistency of readings were the 

 anal fin pterygiophore, opercle, otolith, scale, and vertebra. Various heating, staining, and micros- 

 copy techniques were applied to otoliths and scales with little success. The effect of deviation between 

 otolith readings on survival estimates and age-length relationships is discussed. Consistency of otolith 

 readings was generally superior to other structures for these three species. For yellowtail, canary, and 

 black rockfishes, respectively, 71, 76, and 76% of two independent otolith readings deviated by no more 

 than ±1 assumed annulus. Consistency of otolith readings for all three species decreased with age. 

 Even though age estimates were not completely consistent, Chapman-Robson and catch curve esti- 

 mates of survival, as well as age-length relationships, each derived from two readings of the same set 

 of otoliths, were not significantly different at the 95% level for the three species. Age-length relation- 

 ships are given for both male and female yellowtail, canary, and black rockfishes. 



In 1973, yellowtail rockfish, Sebastes flavidus 

 (Ayres); canary rockfish, S. pinniger (Gill); and 

 black rockfish, S. melanops Girard, composed 41, 

 38, and 4%, respectively, of the total Oregon 

 commercial trawl catch of rockfishes consisting of 

 19 species (Oregon Department of Fish and 

 Wildlife 4 unpubl. data). Because little is known of 

 the biology of these fishes, information on age, 

 length, and weight are needed for estimates of 

 mortality, growth, and ultimately sustainable 

 yield. 



The investigation was based on analysis of 

 samples taken off Oregon from 1972 to 1975. The 

 overall objective was to determine if an acceptable 

 technique! s) could be developed for age determi- 

 nation of these species. Specific objectives were: 1) 

 to determine if counts of annuli on aging 

 structures can be reproduced consistently; and 2) 

 to determine if deviations between successive 



'Supported by funds from the Oregon Department of Fish and 

 Wildlife. Technical Paper No. 4254, Oregon Agricultural 

 Experiment Station, Corvallis, OR 97331. 



department of Fisheries and Wildlife, Oregon State Univer- 

 sity, Corvallis, OR 97331; present address: Pacific Marine 

 Fisheries Commission, 1400 SW. Fifth Avenue, Portland, OR 

 97201. 



department of Fisheries and Wildlife, Oregon State Univer- 

 sity, Corvallis, OR 97331. 



4 Formerly known in part as the Fish Commission of Oregon. 



Manuscript accepted October 1976. 

 FISHERY BULLETIN: VOL. 75, NO. 2. 1977. 



counts of annuli significantly affect estimates of 

 survival and the age-length relationships. 



Considerable effort has been expended on age 

 determination of commercially important species 

 of Sebastes in the North Atlantic. Perlmutter and 

 Clarke (1949) used scales to age juvenile redfish, 

 iS. marinus, but did not include older fish in the 

 study because of difficulty in discerning annuli. 

 Kelly and Wolf (1959) reported 100% agreement 

 between independent readings of redfish otoliths 

 with less than 10 annuli, but agreement between 

 readings for fish from 7 to 20 + yr was only 31%. 

 Sandeman (1961) used scales for juvenile redfish 

 ( <5 yr), but found otoliths to be superior for older 

 fish. 



In the North Pacific Ocean, the majority of 

 research relative to our study has been conducted 

 on the Pacific ocean perch, S. alutus. Alverson and 

 Westrheim (1961) reported readability of scales 

 for Pacific ocean perch was only fair, while 

 Chikuni and Wakabayashi (1970) were satisfied 

 with scales for the same species. Westrheim 

 (1973) subsequently found that agreement be- 

 tween readings of Pacific ocean perch otoliths 

 decreased from 100% for 0-zone otoliths to 26% for 

 19-zone otoliths. Phillips ( 1964) found both scales 

 and otoliths could be used for valid age estima- 

 tions for 10 species of California rockfish, includ- 



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