Table 42. — Estimated biomass and population numbers of Pacific cod by subarea and for all subareas combined, 1976 Bering 



Sea spring trawl survey. 





Percentage 

 frequency of 

 occurrence 



Mean 

 CPUE 

 (kg/km) 



Estimated 



biomass 



(t) 



Proportion 

 of total 



estimated 

 biomass 



Estimated 

 population 

 (millions) 



Proportion 



of total 



estimated 



population 



Mean size 



Subarea' 



Weight 

 (kg) 



FL 



(cm) 



Inner shelf 



















4N 



59.1 



0.02 



41 



< 0.001 



1.2 



0.009 



0.034 



— 



4S 



66.1 



0.12 



534 



0.005 



20.9 



0.163 



0.026 



13.2 



1 



41.0 



0.20 



989 



0.010 



15.1 



0.118 



0.066 



18.4 



Outer shelf 



















and slope 

 3 



60.7 



4.59 



21,496 



0.210 



11.0 



0.086 



1.953 



52.5 



3 Slope 



63.6 



16.72 



3,239 



0.032 



0.9 



0.007 



3.536 



65.4 



2 



84.3 



17.21 



64,285 



0.629 



73.1 



0.570 



0.879 



37.1 



2 Slope 



77.5 



27.39 



11,698 



0.114 



6.0 



0.046 



1.944 



53.7 



All subareas 



















combined 



63.2 



5.12 



= 102.282 





128.2 





0.809 



33.2 



'See Figure 3. 



! 95% confidence limits: 70,581-133.983 t. 



comparison to the distribution of population biomass, 29.0% of 

 the apparent population number were distributed in the inner 

 shelf (subareas 1, 4S, and 4N); 9.3% in subareas 3N, 3S, and 3 

 Slope; and 61.6% in subareas 2 and 2 Slope. 



Size composition. — Pacific cod ranged from 9 to 97 cm FL, 

 with an overall mean fork length of 33.2 cm (based upon 3,938 

 field measurements; Fig. 54). In general, three distinct types of 

 size-frequency distributions were shown by populations in the dif- 

 ferent geographical regions. In the inner shelf (subareas 1 and 4S), 

 size distributions were unimodal and exclusively composed of 

 small, 1-yr-old individuals (range in fork length: Subarea 1, 12-21 

 cm; subarea 4S, 9-19 cm). In outer continental shelf subarea 2, 

 where 63% of the apparent population biomass was located, the 

 size distribution was trimodal (sexes combined) and included a 

 broad size range (10-85 cm). The three principal modes — at fork 

 lengths 17, 35, and 47 cm — approximately correspond to the 

 mean fork lengths of the age 1, 2, and 3 yr populations. In 

 subareas 3S, 3 Slope, and 2 Slope, Pacific cod populations were 

 primarily composed of large (>45 cm) individuals. Mean fork 

 lengths (sexes combined) in those areas were subarea 3S, 52.5 cm 



(range 21-97 cm); subarea 3 Slope, 65.4 cm (31-90 cm); and 

 subarea 2 Slope, 53.7 cm (31-97 cm). 



Age composition. — Estimates of age- frequency distribution 

 were determined from an overall collection of 200 male and 185 

 female scale scrape samples. Scales were taken from the dorsal 

 surface, below and lateral to the second dorsal fin. The ranges in 

 ages observed were males, 1-6 yr, and females, 1-6 yr. 



The apparent number of individuals within each age group of 

 the sampled population is summarized in Table 43. Although 

 subareas 3N and 4N are excluded because no length-frequency 

 data were collected, the estimates of age composition include 

 126.% million (99.0%) of the 128.21 million individuals of the 

 overall apparent population (Table 42). 



The distribution of year -class populations was related to bot- 

 tom depth (Fig. 55). Populations in inner shelf subareas 1 and 4S 

 were exclusively composed of 1-yr-old individuals spawned in 

 1975. In outer shelf subarea 2, 56% of the population was aged 1 

 or 2 yr. In subareas 3S, 3 Slope, and 2 Slope, approximately 89% 

 (range 84-97%) of the apparent populations were 3 yr of age or 

 older. Overall, age groups 1 and 3 yr were most abundant. 



Table 43. — Estimated population size of Pacific cod age groups and year classes within 

 surve> subareas of the eastern Bering Sea, 1976 spring trawl survey.' 





1 



2 



• 



4 



5 



6 



Age 



All ages 



Subarea 1 



1975 



1974 



1973 



19-: 



1971 



1970 



unknown 



combined 

















Inner shelf 



















4S 



1 



20.86 

 15.09 















20.86 

 15.09 



Outer shelf 



















and slope 



















3S 



0.54 



1.52 



4.59 



3.18 



0.95 



0.08 



0.08 



10.94 



3 Slope 



<0.01 



0.02 



0.15 



0.43 



0.27 



0.04 



— 



0.91 



2 



24.51 



16.55 



23.10 



7.00 



1.64 



0.05 



0.29 



73.14 



2 Slope 



0.03 



0.65 



3.02 



1.80 



0.42 



0.01 



0.09 



6.02 



All subareas 



















combined 



61.03 



18.74 



30.86 



12.41 



3.28 



0.18 



0.46 



126.% 



Proportion 



















of total 



0.481 



0.148 



0.243 



0.098 



0.026 



0.001 



0.004 





'The populations in subareas 3N and 4N are not included because no length-frequency 

 data were collected. 

 'See Figure 3. 



76 



