Shi et al.: Growth and survival of Pleuronectes vetulus 
165 
between estuarine and nearshore areas and because 
of differences in mean bottom temperatures between 
estuarine and nearshore systems (2-8°C, Fig. 3). 
3 % 
P T 
isjm isj 
PWMBT jm = > (3) 
p 
isjm 
i= 1 s = 1 
where, PWMBT /m = population-weighted mean bot- 
tom temperature in month j for mode m\P is j m - popu- 
lation of mode m in system i, stratum s, month j; T iy 
= mean bottom temperature in system i, stratum s, 
and month j; and s- = number of strata in system i. 
PWMBT ]m is the best estimate of the average tempera- 
ture experienced by the population in our study area. 
Growth rates A linear model was developed to de- 
termine competing factors that had significant ef- 
fects on the growth of 0 + English sole. 
Iji = a + a x c + a 2j y j + /ft, + /^c^, 
( 4 ) 
+A> jJ + (3 4 T l t l + e Jt , 
where, F = mean modal length (MML) at time F and 
year j; y ; and c are dummy variables for year and 
settlement time; t i = population weighted mean date 
(PWMD); = density (no/ha), monthly mean den- 
sity from May through September; T = population 
weighted mean bottom temperature ( PWMBT ); and 
Ej i = residual. The d t and T terms were used to ex- 
amine whether or not there were density or tempera- 
ture effects (or both) on the growth of 0 + English sole 
in the study areas. The dummy variable y . (year) was 
defined as follows: 
[ 1 1986 f 1 1987 
Vi = 1 ’ y 2 ={ ’ 
[0 otherwise [0 otherwise 
_ ( 1 1988 
' 3 jo otherwise 
Since, settlement time obviously differed between 
cohorts (Fig. 4), the dummy variable (c) was used to 
denote early (1) and the late (0) settlement groups: 
j 1 early settlements ( 1985, 1986 - 1, 1988) 
j 0 late settlements ( 1986 - 2, 1987 ). 
