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Fishery Bulletin 99(2) 
at age from these two studies, both of which 
used otoliths and comprised samples from the 
same geographic area, validates the aging of 
gray snapper determined in the present study. 
Back-calculated lengths at age of gray snapper 
determined from scales by Starck and Schro- 
eder ( 1970) were generally smaller than those 
determined from otolith sections, reasons for 
which are unclear. My samples, as well as 
those of Manooch and Matheson (1981), were 
from Florida’s east coast, whereas Starck and 
Schroeder (1970) used fish from only one loca- 
tion in the Florida Keys. A geographic bias 
may account for the difference in ages between 
the two studies. 
Marginal increment analysis demonstrated 
that gray snapper ages 2-9 deposit one annu- 
lus per year, in June. These ages account for 
the majority of age classes in the fishery; thus 
I posit that the critical evaluations stressed 
by van Oosten (1929) and Beamish and Mc- 
Farlane (1983) were met. Annual deposition of 
growth increments on otoliths of gray snapper was not val- 
idated by previous investigators and thus was an essential 
part of my study. 
I constructed area-specific age-length keys using Sebas- 
tian Inlet, FL (27.8°N latitude), as the north-south divid- 
ing line. In addition to being the traditional division point 
for sample coverage for the south Atlantic headboat sur- 
vey, it also approximates the nearshore-offshore break in 
distribution of reef habitat. I did not have enough data to 
construct annual ALKs as recommended by Ricker (1975) 
and Westrheim and Ricker ( 1978), and my decision to pro- 
duce area-specific ALKs was based on a priori informa- 
tion gained as a port agent in Florida from 1982 to 1987. 
Gray snapper from headboats in north Florida were larger 
than gray snapper from headboats in south Florida. More- 
over, Manooch and Matheson (1981) found differences 
in length-frequency distributions and estimates of total 
mortality by area (smaller fish and higher mortality, Z, in 
south Florida). 
The difference in growth of gray snapper between north 
and south Florida is readily apparent . Mean observed and 
back-calculated sizes at age were largest for fish from 
north Florida, and these fish achieved a much greater 
maximum size and age than did their south Florida coun- 
terparts; significant differences in theoretical maximum 
size between areas were observed (Fig. 3A). Johnson et 
al. ( 1994) found similar results for gray snapper collected 
from the east coast of Florida and the Gulf of Mexico. 
They compared back-calculated size at age for fish cap- 
tured from north and south of 27°N latitude and conclud- 
ed that fish from the northern region were significantly 
larger than fish from the southern region for ages 1-13. 
Their latitude was proximal to the headboat survey divi- 
sional line used in the present study. 
The differences observed in size at age become greater 
in older ages of gray snapper, although estimates for south 
Florida are affected by small sample sizes (few fish >age 
8). The small sample size of older fish in south Florida 
probably reflect a lack of abundance rather than sam- 
pling deficiencies. Commercial and headboat data (Fig. 
5) showed larger and presumably older fish taken from 
north Florida than from south Florida. The headboat fish- 
ery modal length intervals were 400-424 mm TL for north 
Florida and 300-324 mm TL for south Florida. Modal val- 
ues of commercial length frequencies showed a greater dif- 
ference between areas: 550-574 mm TL for north Florida 
compared with 325-349 TL mm for south Florida. Given 
the efficiency of modern fishing fleets (all using hook-and- 
line gear), this finding is strong evidence that the south 
Florida population of gray snapper has a truncated size 
distribution. Manooch and Matheson (1981) found a sim- 
ilar disparity in size distribution of gray snapper from 
headboats from north and south Florida, with respective 
modes at 450-499 mm TL versus 300-349 mm TL. 
One possible explanation for the lack of older, larger 
fish in south Florida is the much greater fishing pressure 
there. Manooch and Matheson (1981) estimated the in- 
stantaneous rate of fishing mortality (F) to be 0.17 and 
0.38 for north and south Florida, respectively. I estimated 
F = 0.16 and F = 0.66 for the respective areas for all fish- 
eries combined, using Hoenig’s (1983) estimates of M - 
0.18 and M = 0.29 and the area-specific estimates of Z 
(F=Z-M). 
The demography and geography of the Florida peninsu- 
la probably affect fishing pressure on gray snapper. South 
Florida is more densely populated than north Florida and 
thus has many more potential anglers. Specifically, an- 
glers fished an average total of 186,687 days from south 
Florida headboats annually from 1982 to 1997, compared 
with an annual average total of 82,325 days from north 
Florida headboats. Shorter distance to the fishing grounds 
in south Florida (5-8 km) than to those in north Florida 
(40-50 km) also leads to increased exploitation. Increased 
pressure on younger inshore fish could lead to growth 
overfishing, whereas easier access to the mature adults 
offshore may contribute to recruitment overfishing. The 
