BEACHAM. VARIABILITY EM SIZE AND AGE OF ATLANTIC COD 

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Female 



Male 



No Data Available 



1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 



Figure 9. — Median age at sexual maturity for Atlantic cod caught during summer Canadian groundfish sur- 

 veys in Division 4W, 1959-79. Vertical bars indicate 95% confidence limits. 



60% from the 1959 values. The A 50 value increased in 

 1979, though further data are necessary to determine 

 if this is a general trend. 



The maturity ogives, based on length, indicated that 

 the trend for elimination of larger, immature Atlantic 

 cod seen in other cod in other areas was also present 

 in this area (Fig. 10). L 50 values for Atlantic cod in 

 1959-64 were 46 cm for males and 52 cm for females, 

 but in 1975-79, these values were 37 and 39 cm, re- 

 spectively. The values in 1975-79 were lower than 

 those in any of the previous three periods (P<0.05). 

 The trend for a transition from an immature to a ma- 

 ture state over a smaller length interval through time 

 was also apparent. The transition occurred over a 45 



cm length interval in 1959-64, but over a 25 cm inter- 

 val in 1975-79. 



Changes in percent mature by age indicate an in- 

 crease through time (Table 3), and males and females 

 ages 3-5 showed marked increases in percent mature 

 over time. Age-2 Atlantic cod also showed marked in- 

 creases, with about 18% of the males and 11% of the 

 females classified as mature in 1975-79, whereas 

 <1% were mature during 1959-64. A J0 values in 

 1959-64 were 4.7 yr for males and 5.0 yr for females, 

 and these values declined in 1975-79 to 2.7 yr for 

 males and 2.9 yr for females (P<0.01). These trends 

 are indicative of a shifting of the A J0 to younger 

 ages. 



313 



