BOWERING: DlSTRIBl'TION OK WITCH FLOUNDER 



slightly less marked and peaked at 3.1°-4.0°C and 

 then declined. The data were too few at the higher 

 temperatures to evaluate the significance of the 

 decline. 



Since depth and bottom temperature are gener- 

 ally related, a mean catch per 30-min set by depth 

 and temperature is presented in Figure 6. When 

 depth and bottom temperature are combined the 

 range of best catches for Div. 2J is about 201-600 

 m and 2.1°-5.0°C. For Div. 3K it is about 201- 

 500 m and 2.1°-4.0°C. For Div. 3L the range of 

 best catches appears to be about 301-600 m and 

 2.1'-4.0 C. Despite the variations in depth and 

 temperature distribution throughout the three 

 divisions shown in Figures 5 and 6, the depth and 

 temperature relationships among the divisions 

 did not differ greatly or at least not among the 

 locations fished (Fig. 7). 



Mean length (cm) and mean age (years) for 

 each depth and temperature interval are pre- 

 sented in Figures 8 and 9 respectively. Mean 

 lengths and ages by depth interval for the three 

 divisions showed similar trends in that they were 

 highest in the shallower depths and declined to 

 reach a low at some intermediate depth then in- 

 creased and stabilized. For the three divisions 



combined there was a significant decrease in 

 mean length from about 52 cm at < 100 m to about 

 43 cm at 401-500 m. Mean lengths increased be- 

 yond this to near 47 cm and stabilized in the 600- 

 900 m range. The mean age decreased from near 

 11 years old at <100 m to about 8 years old at 

 401-500 m. It stabilized at about 10 years old be- 

 yond that. 



For all three divisions there was a general de- 

 clining trend in mean length and age from the 

 lower to intermediate temperatures (Fig. 9). In all 

 cases (except Div. 2J where catches were gener- 

 ally low), the lowest mean size and age occurred 

 at the 3.1°-4.0°C range. For the three divisions 

 combined, there was a significant decline in mean 

 length from about 50.5 cm and 10.0 years old in 

 the 0.1°-1.0°C temperature range to about 45.5 cm 

 and 9 years old in the 3.1-4.0 temperature 

 range. Beyond this range the mean length and 

 age increased again. 



Age Composition 



The age compositions of male and female witch 

 flounder by division and time period are pre- 

 sented in Figure 10. For Div. 2J during 1973-78, 



BOTTOM TEMPERATURE (•C) 



ZERO CATCH 

 Q < I FISH 

 O I -5 FISH 



© 



II- 15 FISH 



16-20 FISH 



21 -30 FISH 



>30 FISH 



Figure 6— Mean number of witch flounder caught per .30-min set by depth and temperature intervals in NAFO Div 



from 1977 to 198.3. (Numbers in parentheses are number of sets ob.served.i 



2.J. 3K, and 3L 



617 



