BEACHAM: VARIABILITY IN SIZE AND AGE OF ATLANTIC COD 



TABLE 3.— Percentage of sexually mature Atlantic cod by age and 

 sex caught during Canadian groundfish surveys in Division 4W, 

 1959-79. Sample sizes are in parentheses for individual ages and 

 95% confidence limits for A (years). 



Age 

 (V) 



1959-64 



1965-69 



1970-74 



1975-79 



Male 



1 

 2 

 3 

 4 

 5 

 6 

 7 

 8 

 9 

 10 

 11 



1 

 2 

 3 

 4 

 5 

 6 

 7 

 8 

 9 

 10 



0.0 

 0.7 

 50 

 26.3 

 57.7 

 83.6 

 90.0 



(59) 

 (143) 

 (282) 

 (205) 

 (208) 

 (280) 

 (250) 



99.3 (141) 



97.2 (71) 



93.1 (58) 



100.0 (21) 



4.69(4.58- 

 4.80) 



(7) 

 (81) 

 178) 

 177) 

 (91) 

 (71) 

 (63) 

 (14) 

 (12) 

 (14) 

 (1) 



3.72(3.58- 

 3.86) 



0.0 



7.4 



25.3 



48.6 



91.2 



95.8 



984 



100.0 



100.0 



100.0 



100 



0.0 



16.1 



51.7 



82.8 



87.7 



91 3 



100.0 



100.0 



100.0 



100.0 



100 



(146) 



(416) 



(395) 



(250) 



(114) 



(46) 



(36) 



(17) 



(4) 



(3) 



(1) 



2.94(2.85- 

 3.03) 



0.0 (120) 



17.5 



65.6 



89.3 



94.3 



97.9 



100.0 



100.0 



100.0 



100.0 



(307) 



(466) 



(421) 



(261) 



(95) 



(26) 



(6) 



(2) 



(0) 



(1) 



2.67(2.59- 

 2.76) 



Female 



(60) 

 (177) 

 (259) 

 (212) 

 (184) 

 (236) 

 (245) 

 (170) 

 (105) 



(77) 



4.95(4.83- 

 5.07) 



0.0 



06 



7.0 



14.6 



45.7 



75.4 



90.2 



95.9 



95.2 



100.0 



0.0 



10.1 



1 7.2 



36.3 



81.9 



898 



90.6 



100.0 



100.0 



1000 



(4) 

 (79) 

 (221) 

 (171) 

 (72) 

 (49) 

 (64) 

 (14) 

 (17) 

 (14) 



4 16(3.99- 



4.35) 



0.0 (144) 

 8.2 (486) 

 (404) 

 (284) 

 (134) 

 (40) 



43.6 

 73.9 

 91.8 

 95.0 



97.1 

 100.0 

 100.0 

 100 



(34) 

 (15) 

 (14) 

 (12) 



3.19(3.1 1- 

 3.28) 



0.0 



11.0 



54.3 



88.4 



99.3 



98.2 



100.0 



100.0 



100 



(106) 



(287) 



(421) 



(445) 



(228) 



(110) 



(31) 



(4) 



(4) 



(0) 



2.87(2.80- 



2.95) 



Division 4X 



Atlantic cod in Division 4X are managed as a 

 separate unit, though inshore and offshore stocks 

 may mix. Trends in L 50 were not as clear as in other 

 stocks, although there was a decrease with time until 

 1978 (Fig. 11). The L 50 values were 51 cm for males 

 and 52 cm for females in 1963, but these values had 

 declined to 38 cm for males and 35 cm for females in 

 1978. Females generally attained maturity at greater 

 lengths than did males, but there has been little dif- 

 ference between sexes over time. The data suggest 

 that there was a decrease in L 50 in 1970-71, as hap- 

 pened in 4VsW Atlantic cod. 



A J0 values have declined with time, but age samples 

 in the early 1960's had small sample sizes. There was 

 a rapid decline in A J0 between 1969 and 1972 with 

 values for males declining from 3.9 to 2.2 yr and for 

 females from 5.0 to 2.4 yr (Fig. 12). In 1978, A 50 

 values were calculated to be < 2 yr for both males and 

 females. Males generally matured at younger ages 

 than did females. 



The maturity ogives, based on length, indicate that 

 there has been some elimination of larger, immature 

 fish from Division 4X Atlantic cod with time, but that 

 the transition from the immature to the mature state 

 during 1975-79 still occurred over the largest length 

 interval of the areas analyzed, being about 35 cm for 



males and 40 cm for females (Fig. 13). In 1959, L 30 

 was 57 cm for males and 46 cm for females, but these 

 values declined to 45 cm for both males (P<0.05) and 

 females during 1975-79. The 100% mature value 

 during 1975-79 was not attained until lengths were 

 >65 cm. 



Changes in percent maturity with age indicate an in- 

 creasing trend with time, but the increase in percent 

 maturity with time has not been as marked as in other 

 Atlantic cod stocks (Table 4). A 50 values in 1959-64 

 were 4.8 yr for males and 3.7 yr for females, but dur- 

 ing 1975-79 these values declined to 2.8 yr for males 

 (P<0.01) and 2.9 yr for females (P<0.05). Increases 

 in percent mature were most apparent in males ages 

 2-5 and females ages 2-4. Median age at maturity has 

 been generally <3 yr in the 1970's. 



Table 4. — Percentage of sexually mature Atlantic cod by age and 

 sex caught during Canadian groundfish surveys in Division 4X, 

 1959-79. Sample sizes are in parentheses for individual ages and 

 95% confidence limits for A 50 (years). 



Age 



(yr) 



Comparisons Among Areas 



Several trends were apparent when all areas were 

 considered in the multiyear grouping of groundfish 

 surveys. Median lengths at maturity tended to 

 decline through time in all areas in which Atlantic cod 

 were surveyed (Table 5). The differences in L 50 

 values among Atlantic cod decreased with time, so 

 that values for Atlantic cod in all areas except those in 

 Division 4X were similar in the period 1975-79. 



In an analysis of trends in A J0 , there was a trend for 

 younger ages at maturity over time. Differences 

 among areas generally decreased with time, so that in 

 the period 1975-79, A 50 values were about 2.7 yr for 



315 



