FISHERY BULLETIN: VOL. 75, NO. 2 



ing S. flavidus and S. pinniger, but used scales 

 because they were obtained with less effort. Miller 

 and Geibel (1973) preferred scales to otoliths for 

 blue rockfish, S. mystinus, off California because 

 scales allowed greater ease in back-calculation of 

 growth. Wales (1952), working on the same 

 species, reported that scales were easier to read 

 than otoliths. Chen (1971) found scales were 

 frequently regenerated on rockfish of the sub- 

 genus Sebastomus, so he used otoliths for age 

 determination. 



Otoliths were used to age copper rockfish, S. 

 caurinus, in Puget Sound (Patten 1973) and 

 northern rockfish, S. polyspinis, in the Gulf of 

 Alaska ( Westrheim and Tsuyuki 1971 ). There are 

 no published reports on the life of S. melanops, 

 although Miller (1961) indicated that the ages of 

 several specimens were estimated. Westrheim 

 and Harling ( 1975) used otoliths to determine age- 

 length relationships for 26 scorpaenids in the 

 northeast Pacific. 



TABLE 1. — Structures examined from yellowtail rockfish, 

 canary rockfish, and black rockfish with a description of their 

 suitability for age determination. 



Structure 



Description 



Anal fin pterygiophore 



Anal spine 



Articular 



Astenscus 



Basipterygium 



Ceratohyal 



Cleithrum 



Dentary 



Epihyal 



Hypurals 



Interopercle 



Lachrymal 



Lapillus 



Maxilla 



Mesopterygoid 



Neurocranial bones 



Opercle 



Pelvic fin rays 



Postcleithrum 



Premaxilla 



Sagitta 



Scale 



Subopercle 



Supracleithrum 



Vertebral centrum 



enumerable zones present 



zones present, but not enumerable 



insufficient calcification 



insufficient calcification 



zones present, but not enumerable 



insufficient calcification 



zones present, but not enumerable 



zones present, but not enumerable 



insufficient calcification 



insufficient calcification 



zones present, but not enumerable 



insufficient calcification 



insufficient calcification 



zones present, but not enumerable 



insufficient calcification 



insufficient calcification 



enumerable zones present 



zones present, but not enumerable 



insufficient calcification 



zones present, but not enumerable 



enumerable zones present 



enumerable zones present 



insufficient calcification 



zones present, but not enumerable 



enumerable zones present 



METHODS AND MATERIALS 



Most fish used in this study were sampled 

 randomly from the commercial trawl landings in 

 Astoria and Coos Bay, Oreg., from 1972 to 1975. 

 Sex, length to the nearest centimeter, and weight 

 to the nearest gram were recorded, and one or both 

 saccular otoliths (sagittae) were extracted. 

 Twenty-five anatomical structures (Table 1), 

 including the anal fin pterygiophores (largest), 

 opercles, otoliths, scales, and several anterior 

 vertebrae were sampled from carcasses obtained 

 from fish processing plants in Newport, Oreg., 

 from 1974 to 1975. Juvenile fish were collected on 

 research cruises on the Oregon continental shelf 

 from 1972 to 1974, and by scuba and hook-and- 

 line in Yaquina and Tillamook bays from 1973 to 

 1975. 



Otoliths were stored in a 50:50 solution of 

 glycerine and water and read using reflected light 

 on a dark background utilizing a binocular 

 dissecting microscope at 10 x. Otolith sections 0.3 

 mm thick were obtained with a thin sectioning 

 machine after being embedded in polyester 

 casting resin. Scales were cleaned, dried, and 

 mounted between glass slides or impressed on 

 acetate cards and read using a scale projector with 

 a 48-mm objective. Other structures, including 

 opercles, pterygiophores, and vertebrae were 

 heated in a detergent-water solution at 50°C for 20 

 min to remove adhering tissue and air dried. 



Opercles were examined with the naked eye and 

 pterygiophores and vertebrae were examined by 

 use of a binocular dissecting microscope at 10 x. 



One year of the life of the fish was assumed to be 

 represented by an opaque zone followed by a 

 hyaline zone on otoliths (Kelly and Wolf 1959; 

 Westrheim 1973) as well as on opercles, pterygio- 

 phores, and vertebrae. A scale annulus was 

 defined as a zone of closely spaced circuli (check) 

 following a zone of widely spaced circuli (Van 

 Oosten 1929; Tesch 1968). True annuli are 

 represented by pronounced hyaline zones on 

 otoliths and bony structures and by pronounced 

 checks on scales. Indistinct zones or zones that are 

 split or discontinuous were considered accessory 

 (false) annuli. A zone that obviously interrupts 

 the periodicity of the pattern of zonation was 

 considered to be accessory unless it occurred in 

 many fish in the same sample. 



Consistency of readings of aging structures was 

 measured by the ability of the reader to reproduce 

 successive, independent counts of annuli. To 

 insure independence there was a period of several 

 months between most otolith readings. When the 

 period was less than 2 wk, a five digit code number 

 was assigned to each structure to prevent possible 

 memorization of previous age estimations. Inde- 

 pendent readings of yellowtail rockfish otoliths 

 were made by two people, while those of canary 

 and black rockfishes were made by the same 

 person. 



406 



