BOWERING: DISTRIBUTION OK WITCH FLOUNDER 



Table 1. — Regressions and correlation coefficients for age and 

 growtfi (lOQe length (cm) = a + b log^ age (years)) of male and 

 female witch flounder in NAFO Divisions 2J, 3K and 3L. 



sizes at age are likely to be lower than here calcu- 

 lated. As a result, the predicted size at age is 

 probably only meaningful up to about age 12 for 

 males and age 15 for females for the earlier pe- 

 riod, and age 10 for males and age 12 for females 

 in the later period (Fig. 11). Predicted size for 

 males in Div. 3L during the earlier period is also 

 somewhat biased below age 6. Despite these con- 

 cerns there has been a substantial increase in size 

 at age of both males and females in all three divi- 

 sions between the earlier periods and later peri- 

 ods (Fig. 12). A comparison of growth curves by 

 division, for each sex and time period (Fig. 13), 

 suggests that the size at age of witch flounder in 

 Div. 3K is higher in all cases than that of Div. 3L. 

 It is also higher than that of Div. 2J in the earlier 

 period; however, in the later period the mean size 

 at age of the younger fish in Div. 2J is generally 

 higher. 



Changes in mean size at age in terms of weight 

 are presented in Table 2. With the exception of 

 some of the younger age groups, where there was 

 some small reduction in size at age over the time 

 period, there was a substantial increase in weight 

 at age for all commercial size age groups (age 7 + ). 

 The amount of increase in weight at age varied 

 (Table 2) among divisions but most age groups 

 had increases in weight between 25 and 62%. 



Sexual Maturity 



The proportions of mature and immature witch 

 flounder are shown in Figure 10. Most males 

 caught were in a mature condition for all divi- 

 sions and time periods. Few mature males caught 

 were <6 years old and all were mature beyond 10 

 years old. The proportions of mature and imma- 



ture fish at particular ages, however, varied 

 among divisions and time periods. For females, 

 few mature fish were caught <8 years old in most 

 divisions and time periods, with the possible ex- 

 ception of Div. 3K during 1970-78. Most were ma- 

 ture beyond age 12. As with the males, the pro- 

 portions mature and immature at particular ages 

 varied among divisions and time periods (Fig. 10). 



Lengths and ages at M50 with 959f fiducial lim- 

 its are presented in Figure 14. For males there 

 was no significant difference in length at M50 for 

 either Div. 3K or 3L between the earlier and later 

 periods (no data for Div. 2J). For females there 

 was no significant change in M50 for Div. 3K be- 

 tween the 1970-78 and 1979-83 periods but there 

 were statistically significant reductions in M50 

 from about 47.0 cm in 1973-78 to about 44.2 cm in 

 1979-83 for Div. 2J and from about 44.8 cm in 

 1968-78 to 41.5 in 1979-83 for Div. 3L (Fig. 14). 



For males there was no significant change in 

 age at M50 for Div. 3K between 1970-78 and 1979- 

 83. However, the age at M50 for males in Div. 3L 

 was significantly reduced from about 6.0 years in 

 1968-78 to 3.5 years in 1979-83 (no data available 

 for Div. 2J). For females there was no significant 

 change in age at M50 for Div. 3K between 1970-78 

 and 1979-83. There was a statistically significant 

 reduction in age at M5Q for Div. 2J from about 

 10.4 years in 1973-78 to 7.5 years in 1979-83. 

 There was a slight overlap in fiducial limits for 

 Div. 3L, however, for practical purposes the age 

 at M50 was reduced from 9.8 years in 1968-78 to 

 7.8 years in 1979-83. 



DISCUSSION 



Distribution 



Witch flounder are distributed throughout the 

 management zone from the northern slopes of 

 Hamilton Bank to the northern slopes of the New- 

 foundland Grand Bank. Bowering (1976) sug- 

 gested that witch flounder reaches its northern 

 limits in the Northwest Atlantic at the northern 

 slopes of Hamilton Bank although catch statistics 

 of NAFO occasionally reported commercial 

 catches north of here. Unpublished data from sur- 

 veys in Div. 2G and 2H by the Northwest Altantic 

 Fisheries Center, St. John's, Newfoundland have 

 never reported catches of witch flounder in these 

 areas and support the contention of Bowering 

 (1976) and question the accuracy of some com- 

 mercial catch reports. For the area surveyed, the 

 distribution of witch flounder presented here is 



623 



