Both otoliths were removed and placed in 95% 

 ethyl alcohol .- 



Age Determination Procedure 



Studies by Hatanaka (1968) of yellowfin sole 

 from the southeastern Bering Sea indicate that 

 the translucent zone of an otolith is formed once a 

 year during the winter months. In our readings on 

 otoliths from all species, each translucent zone was 

 considered an annular mark. The outermost edge 

 of each otolith was also translucent except in the 

 younger fish where there was evidence of some 

 beginnings of opaque summer growth. Thus, the 

 ages recorded are the number of translucent rings 

 starting with the smallest observable and includ- 

 ing the outermost. For example, a fish captured in 

 July 1961 with 10 rings on its otolith was con- 

 sidered to have been spawned and hatched in 1951. 

 Fadeev (1965), through gonad examination, stated 

 that Bering Sea yellowfin sole spawn in June- 

 August, Alaska plaice in April-June, and rock sole 

 in February-May. Shubnikov and Lisovenko 

 (1964), who reported that rock sole in Bristol Bay 

 spawn in March-June, are in general agreement 

 with Fadeev. 



For reading, the otoliths were immersed in 

 water in a petri dish with a black mat background 

 and examined at 10 x under reflected light with a 

 dissecting microscope. Both otoliths were con- 

 sidered in age determination, but when a 

 discrepancy occurred between the two otoliths, a 

 decision was based on the eyed-side (right) otolith. 

 In situations where the annular rings were not 

 clear, the otoliths were ground on fine, water 

 soaked, carborundum paper. In most samples 

 grinding improved interpretation of annular 

 rings, but the grinding of rock sole otoliths often 

 exposed additional opaque and translucent zones 

 to further confuse the readers. 



Consistency of Age Determinations 



Without reference to fish size, otoliths were in- 

 terpreted by each author. A third, independent 

 interpretation was made by an experienced otolith 

 reader at the Northwest Fisheries Center. The 

 observed ages, as agreed upon between the two 

 authors, were compared with ages determined by 

 the experienced reader. Initial agreement 



between authors and reader was 76% for yellowfin 

 sole, 72% for Alaska plaice, and 85% for rock sole. 

 Disagreements were not confined to a particular 

 age class; only 3% differed by more than 1 yr, and 

 these differences were equally negative and posi- 

 tive. The similarity of results by authors and 

 reader suggests that the method used produced 

 consistent age-growth data. Otolith interpreta- 

 tions not in agreement between the authors and 

 the reader were reread and a joint decision was 

 made on the most probable age of the fish. 



Results and Discussion 



Distribution 



Yellowfin sole is the most abundant flatfish 

 taken in the eastern Bering Sea. Alaska plaice 

 (33% by weight of yellowfin sole caught) was 

 usually encountered together with yellowfin sole 

 and share a similar distribution within the 

 sampling area (Figure 2). Fadeev (1970) and 

 Maeda et al. (1967) note that yellowfin sole con- 

 centrate in the colder waters of Bristol Bay during 

 the spring and summer months. In July of 1961, a 

 tongue of cold water extended into the sampling 

 area and the greatest concentrations of yellowfin 

 sole and Alaska plaice were taken at bottom 

 temperatures of 3°C or less. 



The distribution of rock sole within the 

 sampling area (28% by weight of yellowfin sole 

 catch) was spotty with the denser concentrations 

 occurring toward the eastern edge of the area 

 inhabited by yellowfin sole and Alaska plaice. The 

 1961 observations are compatible with the conten- 

 tion of Shubnikov and Lisovenko (1964) that rock 

 sole disperse during the summer into shallower 

 water than they occupy in winter and spring. 



Age-Length Observations 



The age-length-weight composition for the 

 three southeastern Bering Sea flatfish species 

 sampled in 1961 are given in Tables 1-3.' It is 

 difl^cult to compare the 1961 data with any earlier 

 reports except in a generalized manner since in 

 only one instance (Pruter and Alverson 1962) is 

 there a determination of age by sex. The data 

 presented in Tables 1-3, and also in studies of eas- 



-All otoliths from the 1961 collection are inpermanent storage 

 at the Northwest Fisheries Center, Seattle, Wash. 



'Individual age determinations and related lengths and 

 weights, by sex, are available upon request from the Northwest 

 Fisheries Center, National Marine Fisheries Service, NOAA, 

 Seattle, Wash. 



920 



