742 
Fishery Bulletin 95(4), 1997 
in the life history of red porgy during a 22-year pe- 
riod ( 1972 to 1994). The first study of age and growth 
on red porgy (1972-74) (Manooch and Huntsman, 
1977) was assumed to describe a stock with the same 
life history as the virgin population, even though it 
was subject to light fishing pressure. By the late 
1970’s and early 1980’s, the growth pattern of the 
stock had changed. The mean observed and back- 
calculated lengths-at-age as well as the von 
Bertalanffy growth curve for the 1979-81 period 
showed a larger size at age for ages 2-6 but a 
lower theoretical maximum size. The increase 
in growth rate, and resultant increase in size- 
at-age observed during this period, is consid- 
ered a typical density-dependent response to 
an increase in mortality as the depressed 
population responds to an increased avail- 
ability of resources (Pitcher and Hart, 1982; 
Rothschild, 1986). The decrease in theoreti- 
cal maximum size between 1979 and 1981 
may have resulted from the selective removal 
of larger individuals from the population by 
fishermen and not from a biological change 
in the theoretical maximum size that the fish 
could attain. 
During the mid 1980’s through the early 
1990’s, increasing fishing pressure appar- 
ently continued the selective removal of 
larger, faster growing individuals from the 
population, further exacerbating the changes 
in the life history of red porgy. By 1988-90, 
mean back-calculated sizes-at-age were sig- 
nificantly smaller for all ages except age 1 in 
comparison with 1979-81. In 1988-90, the 
values of k and were smaller than during 
1979-81 and 1972-74, indicating a reduced 
growth rate and a lower theoretical maximum 
attainable size. Mean back-calcu- 
lated size-at-age for specimens col- 
lected between 1991 and 1994 were 
significantly smaller than those col- 
lected in 1988-90, except for ages 
1, 7, and 10. These temporal reduc- 
tions in the size-at-age and growth 
rates suggest that many individu- 
als genetically predisposed towards 
rapid growth and larger size may 
have been selectively removed from 
the population, leaving behind in- 
dividuals that tend to be slower 
growing and smaller. 
Red porgy also responded to the 
continued removal of larger indi- 
viduals from the population over 
many generations by females be- 
coming sexually mature at smaller 
sizes during 1991-94 than during 
1979-81. Manooch (1976) reported 
that female red porgy became ma- 
ture at much larger sizes than those 
70 
60 
50 - 
S' 40 
C 
u. 
30 - 
20 - 
10 - 
V/////A Hook and line 
62ZZ2 Blackfish trap 
l l Florida trap 
nwni Chevron trap 
iP 
P 
23j 
140-159 180-199 220-239 260-279 300-319 340-359 380-399 
Size class (mm fork length) 
Figure 5 
Length frequency for all red porgy sampled in MARMAP surveys 
between 1988 and 1994 by gear type. 
o 
?T 
?T 
£3 
3 “ 
3 
3 
Year 
Figure 6 
The mean age of red porgy sampled in MARMAP surveys between 1988 and 
1994. 
