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Fishery Bulletin 96(3), 1998 
Results 
Fishing effort and sampling intensity 
Trends in nominal fishing effort, measured as the 
numbers of licensed recreational, commercial, and 
headboats vessels in Monroe County, show that rec- 
reational fishing effort has increased sharply since 
1965 (Fig. 3). Since 1981, the largest increase has 
clearly come from the recreational sector and con- 
tinues to increase whereas commercial and headboat 
sectors have been relatively stable. 
In the 18-year (1979-96) visual survey, 4,571 point 
samples were collected over a variety of bottom types 
from 72 reefs located throughout the Florida Keys 
at depths to 21 m (Table 1; Fig. 1). The complete da- 
tabase contains information on 226 reef fish species 
in 55 families with 42 biological, habitat, and physi- 
cal covariates. 
Table 2 
Parameters, definitions, and units for population dynamics 
variables common to the LBAR and REEFS numerical mod- 
els used in simulation analysis of Florida Keys reef fish popu- 
lation dynamics. See Table 3 for parameter values. 
Parameter 
Definition 
Units 
s 
Reef fish species (s=l, . . . ,n) 
a 
Cohort age class (a=l, . . . ,t x ) 
t 
r 
Age of recruitment 
months 
L r 
Size at recruitment 
mm 
L 
Minimum age of maturity 
months 
K 
Minimum size of maturity 
mm 
t' 
Minimum age of first capture 
months 
L' 
Minimum size of first capture 
mm 
h 
Oldest (largest) age 
years 
W 
Largest (oldest) size 
mm 
Ultimate weight 
kg 
Ultimate length 
mm 
K 
Brody growth coefficient 
per year 
1 0 
Age at which size equals 0 
years 
a WL 
Scalar coefficient of 
weight-length function 
dimensionless 
P\VL 
Power coefficient of 
weight-length function 
dimensionless 
W(a,t ) 
Weight at age a at time t 
g 
L(a,t ) 
Length at age a at time t 
mm 
N(a,t) 
Numbers at age a at time t 
number of fish 
M(a,t) 
Natural mortality rate at 
age a at time t 
per year 
F(a,t) 
Fishing mortality rate at age 
a at time t 
per year 
S(a ) 
Survivorship to age a 
dimensionless 
Z(t) 
Total mortality rate in year t 
dimensionless 
0(a) 
Sex ratio at age a 
dimensionless 
B(a,t) 
Biomass at age a in year t 
kg 
YJt) 
Yield in weight in year t 
metric tons 
SSB(t) 
Spawning stock biomass in 
year t 
metric tons 
SPR(t) 
Spawning potential ratio in 
year t 
percent 
Average size and mortality 
Average annual length was estimated for headboat 
catch statistics (1981-95) and for visual survey data 
(1979-96). Headboat data were used in the compara- 
tive analysis with the visual survey data because they 
provide consistent catch statistics and effort data. 
Typical comparisons of average length in the exploit- 
able phase of the stock for the two data sets are shown 
for eight representative, economically important reef 
fishes: black grouper, red grouper, gray snapper, yel- 
lowtail snapper, white grunt, bluestriped grunt, hog- 
fish, and great barracuda (Fig. 4). The 95% confi- 
dence intervals were computed for the visual esti- 
mates but could not be determined for the headboat 
data at this time owing to the survey estimation pro- 
cedures used to calculate total numbers and total 
weight for the entire Florida Keys. In a few instances 
(e.g. 1985 and 1986), the computed confidence bounds 
were large owing to low sample sizes, but these mean 
estimates still correlated well with the rest of the 
data. 
The estimated average lengths in the exploitable 
phase from the two independent data sources were 
highly correlated for groupers, snappers, and grunts 
(Fig. 4). The trend in average size also was relatively 
flat over the last 18 years and close_to L' (Fig. 4). 
Although the relation between L for visual and 
headboat data was similar for all groupers, snappers, 
and grunts, it differed somewhat for hogfish and 
barracuda (Fig. 4, G and H). Average length ( L ) for 
hogfish was consistently smaller in visual samples 
than in headboat landings. In both data sets, how- 
ever, L declined in the early 1980s but has steadily 
increased since the late-1980s (F=3.96, df=9, 
PcO.OOOl) (Fig. 4G). Average length for barracuda 
increased significantly (F= 2.2, df=10, P<0.018) in 
visual surveys but declined in headboat landings 
beginning in the early 1980s (Fig. 4H). Increased 
mean barracuda size in visual samples indicates that 
there has been a corx^sponding increase in abun- 
dance because larger L requires increased survival. 
In visual samples, barracuda are now the top ranked 
species in biomass among all Florida Keys reef fishes. 
