Harris and McGovern: Changes in the life history of Pagrus pagrus 
735 
females to males, no comparison of size-at-age or 
growth rates were undertaken for the sexes sepa- 
rately. Life history data collected during four peri- 
ods (1972-74, 1979-81, 1988-90, and 1991-94) were 
compared. The first study (1972-74) used red porgy 
sampled from headboats operating from North and 
South Carolina (see Manooch, 1976; Manooch and 
Huntsman, 1977). Specimens were collected through- 
out the year and gonads from 736 fish were exam- 
ined macroscopically to assess sex and stage of ma- 
turity (Manooch, 1976). Scales from 3,278 individu- 
als were examined to determine ages, and 222 fish 
were aged from whole otoliths ( Manooch and Hunts- 
man, 1977). 
Red porgy collected during 1979-81, 1988-91, and 
1991-94 were grouped by period. Otolith radius to 
fork length least-squares regressions were fitted 
separately for each period (except that of 1972-74) 
owing to concerns about temporal changes in somatic 
growth. Von Bertalanffy growth curves (von Ber- 
talanffy, 1938) were fitted to the mean back-calcu- 
lated size-at-age for each of the four study periods. 
Size-at-age was backcalculated for all increments 
measured. Mean observed and back-calculated sizes- 
at-age were compared between periods for each age 
with a single-factor ANOVA. Size and age distribu- 
tions and size-at-age were compared between the 
three latitudinal zones sampled with single factor 
and two-way ANOVA’s. It appeared from observations 
during sampling that larger fish may be associated 
with the shelf break; therefore size and age distribu- 
tions, and size-at-age were also compared for differ- 
ent depths. Because the shelf break is located at 
about 48 m, two depth zones — 0 to 45 m and 46 to 90 
m — were compared. The same tests were performed 
in comparing annual data collected between 1988-94. 
Reproduction 
The posterior portion of the gonads of red porgy from 
1979 to 1994 was removed from the fish and fixed in 
10% seawater formalin for 1-2 weeks, then trans- 
ferred to 50% isopropanol for 1-2 weeks. Gonad 
samples were processed with an Auto-Technicon 2A 
Tissue Processor, vacuum infiltrated, and blocked in 
paraffin. Three transverse sections (6-8 pm thick) 
were cut from each sample with a rotary microtome, 
mounted on glass slides, stained with double- 
strength Gill haematoxylin, and counter-stained with 
eosin y. Sex and reproductive state were assessed by 
one reader according to histological criteria (Table 
1). Specimens with developing, ripe, spent, or rest- 
ing gonads were considered sexually mature. For fe- 
males, this definition of sexual maturity included 
specimens with oocyte development at or beyond the 
yolk vesicle stage and specimens with beta, gamma, 
or delta stages of atresia. Sex ratios, size-at-first- 
maturity, and the percent of mature females by 20- 
cm size class were calculated for all functional males 
and females, 1989-94. Sex ratio, size-at-first-matu- 
rity, and the percent of mature females were deter- 
mined by size class for 1979-81, 1988-90, and 1991- 
94, and chi-square (% 2 ) analysis was used to deter- 
mine if there were significant differences in the pro- 
portion of males to all fish collected during the three 
periods and if there were differences in size-at-ma- 
turity between periods. 
ResuSts 
1979-1994 
A total of 20,756 ( 13,120 during 1972-74) red porgy 
were sampled during the four periods, of which 4,503 
were aged and 4,293 sexed and staged (Table 2). The 
mean FL of fish collected from 1979 to 1994 showed 
a declining trend; however, there was no trend in 
mean age (Table 2). Increment formation was as- 
sumed to be annual (Collins et al., 1996; Manooch 
and Huntsman, 1977). 
Age and growth 
The mean observed size-at-age declined markedly 
from 1972-94 through 1991-94. Except for fishes 
aged 2-8 yr collected during 1979-81, the mean sizes- 
at-age for all ages for the three periods between 1979 
and 1994 were smaller than those during 1972-94 
(Fig. 2). The observed sizes-at-age in 1988-90 and 
1991-94 were significantly smaller than those dur- 
ing 1979-81 (P<0.01) for ages 2 through 8. Red porgy 
aged 3 through 5 collected during 1991-94 were also 
significantly smaller than fish of the same age col- 
lected during 1988-90 (PcO.Ol). We were unable to 
include data collected by Manooch and Huntsman 
(1977) in our statistical analyses. The mean back- 
calculated size-at-age showed trends similar to the 
mean observed size-at-age (Fig. 3). Fish aged 2-8 
were significantly smaller during 1988-90 and 1991- 
94 than during 1979-81, and fish aged 2-5 significantly 
smaller in 1991-94 than in 1979-81 and 1988-90. 
The von Bertalanffy growth curves derived from 
mean back-calculated lengths for each period (Fig. 
4) showed similar trends. The theoretical mean maxi- 
mum fork length (LJ declined by 100 mm from 1972- 
74 to 1991-94 (Table 3). The theoretical growth rate 
(&) was higher between 1991 and 1994 than between 
1972 and 1974. This difference is a reflection of the 
large decline in L to , rather than an increase in growth 
