Harris and McGovern: Changes in the life history of Pagrus pagrus 
739 
the three latitudinal zones. However, signifi- 
cant differences were apparent in the size 
and age distribution between the two depth 
zones (P<0.05), with larger and older fish 
occurring in the deeper zone. There were no 
significant differences in the size-at-age be- 
tween these two zones (P>0.05). 
Discussion 
Samples were collected from throughout the 
SAB during 1988-94. However, 69% of the 
collections and 73% of the aged red porgy 
were taken from zone 2 (32°N-33°N). Zone 2 
was sampled most frequently because it was 
most accessible from Charleston, South Caro- 
lina, the base of operations (latitude 32° 
45'N). Once settled, red porgy do not appear 
to move very much (Parker, 1990) and could 
experience differential growth rates because 
of differing environments. Therefore the con- 
centration of sampling in zone 2 could have 
resulted in biased estimates of size-at-age. 
However, the comparison of size-at-age of red 
porgy showed no significant differences be- 
tween latitudinal or depth zones; therefore, 
although there may be localized differences 
in growth rates, perhaps associated with dif- 
ferent patches of live bottom, the mean 
growth rate appears to be similar throughout the 
region. The mean depth and temperature of areas 
sampled in the MARMAP surveys have not changed 
significantly since 1987; thus these environmental 
variables, at least, have not caused the life history 
changes in red porgy (Fig. 11). 
There were significant differences in size and age 
by depth, with larger and older fish occurring in 
deeper water. This difference may be due to fisher- 
men operating in deeper water with larger hooks and 
baits to target groupers, thus reducing the availabil- 
ity of this gear to red porgy, particularly to smaller 
Table 5 
Percentage of red porgy females that were sexually mature relative to all females collected during 1979-81 and 1991-94. 
A significant difference (^ 2 ; PcO.Ol) in the proportion of mature females is denoted by “A”. 
Size (mm TL) 
1979-81 
1991-94 
Total 
females 
Number 
mature females 
Percent 
mature females 
Total 
females 
Number 
mature females 
Percent 
mature females 
<200 
16 
— 
— 
55 
2 
3.64 
200-225 
91 
1 
1.10 
182 
4 
2.20 
226-250 
85 
11 
12.94 
156 
26 
16.67 
251-275 
103 
28 
27.18 
157 
85 
54.14 a 
276-300 
78 
77 
98.72 
211 
189 
89.57 
>300 
512 
512 
100.00 
615 
606 
98.54 
Total 
885 
62 
1,376 
912 
