324 
Fishery Bulletin 96(2), I 998 
Mortality 
The estimates of Z were calculated from the decline 
in indices of relative abundance at shallow-water 
fixed stations from May (month of secondary peak 
in abundance) to June for Choctawhatchee Bay, and 
April (month of peak abundance) to May for Tampa 
Bay and Charlotte Harbor. Relative abundance in- 
dices were averaged over all years prior to calcula- 
tion in order to reduce the effects of interannual vari- 
ability. Estimates of Z were 0.022/d, 0.021/d, and 
0.023/d for Choctawhatchee Bay, Tampa Bay, and 
Charlotte Harbor, respectively (Table 4). 
Discussion 
Seasonal changes in YOY abundance and 
size structure 
Pelagic pinfish larvae are transported 
from oceanic spawning areas and dis- 
persed into estuaries via near-surface 
water currents (Darcy, 1985). After 
metamorphosis, postlarvae settle more 
or less near the bottom in estuaries 
(Hildebrand and Cable, 1938; Caldwell, 
1957). Initial appearance of postlarvae 
(9-12 mm) and larger YOY (<28 mm) in 
shallow and deep water within a one- 
month period suggests pinfish settle to 
both areas in Choctawhatchee Bay and 
Tampa Bay. In Charlotte Harbor, settle- 
ment appears to occur first to shallow 
water, and then to deep water, because 
YOY pinfish were absent in trawls un- 
til 1-3 months after their first appear- 
ance at fixed seine stations. One expla- 
nation for these different patterns of 
settlement may lie with the bathymetry 
of each bay: more shallow-water area 
with seagrass beds (YOY pinfish are 
dependent on seagrass for protection 
from predators and food [Stoner, 1980; 
1983]) is available in Charlotte Harbor 
(seagrass area=202 km 2 ) than in Choc- 
tawhatchee Bay (33 km 2 ) or Tampa Bay 
(83 km 2 )( Sargent et al., 1995). 
The occurrence of YOY pinfish mostly 
in water <3.5 m suggests that pinfish 
distribution is depth-restricted. The pro- 
pensity of YOY pinfish to limit their 
depth is probably due to their depen- 
dence on seagrasses for cover (sea- 
grasses are generally restricted to wa- 
ters <2.3 m in Choctawhatchee Bay, 
Tampa Bay, and Charlotte Harbor 
[Durako 1 ]), the distribution of pelagic 
and mobile epibenthic prey (Stoner, 
1980), and light intensity (Gulbrandsen, 
1996) (YOY pinfish must see their prey 
100 
80 - 
60 
40 
20 -I 
0 
Choctawhatchee Bay 
1989 1990 1991 1992 1993 1994 
Figure 7 
Annual indices of young-of-the-year abundance and 95% confidence inter- 
vals for Choctawhatchee Bay, Tampa Bay, and Charlotte Harbor from 1989 
to 1994. 
1 Durako, M. 1996. Florida Marine Research 
Institute, 100 Eighth Avenue SE, St. Peters- 
burg, FL 33701-5095. Personal commun. 
