Hams and McGovern: Changes in the life history of Pagrus pagrus 
743 
found in the present study. Further- 
more, the red porgy population has re- 
sponded to increased fishing pressure 
by undergoing sexual transition and by 
producing significantly more males at 
smaller sizes in recent years than dur- 
ing 1979-81. Koenig et al. (1996) re- 
ported that gag, Mycteroperca micro- 
lepis, a protogynous grouper, was un- 
dergoing sexual transition at much 
smaller sizes during 1991-93 in the 
Gulf of Mexico than were reported by 
Hood and Schlieder (1992 ) for the same 
region, during 1977-80. Changes in life 
history aspects of gag from the Gulf of 
Mexico were attributed to steadily in- 
creasing fishing pressure. 
The decrease in mean size-at-age, 
growth rates, and size-at-maturity dur- 
ing 1988-1994 is probably a continua- 
tion of the changing life history pattern 
of the population that has resulted from 
sustained fishing pressure and indi- 
cates the degree of change that can oc- 
cur over relatively short periods of time. 
These relatively rapid changes in size- 
at-age may reflect the inability of an 
overfished or depressed population to 
absorb or respond to further decreases in 
population size. Apart from the decreases in 
size-at-age apparent from recent years, the 
mean age and fork length of the population 
has increased since 1988. These increases 
may be due to a decline in the number of 
younger fish recruiting to the population. The 
net effect of fewer young fish in the popula- 
tion (and therefore samples) would be an in- 
crease in the mean age and size of the 
sampled fish. Length-frequency data col- 
lected in MARMAP surveys since 1988 indi- 
cates no strong recruiting year class (age-1) 
since 1990. Huntsman et al. 2 found that the 
estimated number of 1-year-old red porgy had 
declined steadily since 1973 (Murphy VPA, 
M=0.28); their results also indicate that the 
population may be experiencing a decline in 
recruitment. 
A decline in recruitment may be attributed 
to several factors that are the result of sus- 
tained overfishing. First, as the number of 
fish in the population declines, fewer and 
fewer females are available to spawn, result- 
ing in a decline of total potential egg production in fish that are less fecund than larger fish (Manooch, 
(Vaughan et al., 1992; Huntsman et al. 2 ). Second, 1976). Finally, smaller females may produce eggs that 
decreases in size-at-maturity and size-at-age result are poorer in quality than those produced by larger 
i- 
£ 
•o 
<u 
£ 
450 
400 - 
350 - 
300 - 
250 - 
200 
Age (years) 
Figure 7 
'he mean observed size-at-age of red porgy for every second year between 
988 and 1994. 
Age (years) 
Figure 8 
The mean back-calculated size-at-age for every second year between 
1988 and 1994. 
