Davis (1940) reports that, in numerous instances, fishermen and guides pointed out changes 
they observed during the past 20 to 40 yrs, and some of these observations, when checked 
against maps, were found to be reliable. 
Snedaker (1994) suggests that changes in precipitation and runoff are the most important 
factors concerning mangrove survival in the face of global change. Reduced rainfall and runoff 
would result in higher salinity and greater seawater sulfate exposure. This change would likely 
be associated with decreased primary production and increased sediment organic matter 
decomposition leading to subsidence. Higher rainfall and runoff would result in reduced salinity 
and exposure to sulfate, and also increase delivery of terrigeneous nutrients. Consequently, 
mangrove production would increase and sediment elevations would be maintained. Support for 
this scenario derives from studies of the high production in saline mangrove impoundments 
which are depleted in seawater sulfate. 
6.7. Fish dieoffs 
During the summer/fall period of 1990, three large fish kills occurred in the Snake Bight area, 
east of Flamingo in north central Florida Bay (Schmidt and Robblee, 1994). Based on summaries 
of historical park fish kill events, it was found that 38 kills have occurred since 1944; seven 
took place during the passage of south Florida cold fronts while the remaining 31 occurred 
between March and November and appear to have resulted from hypoxic conditions due to local 
environmental extremes. Nearly half of the kills took place in the waters of either Florida or 
Whitewater Bays; 24% occurred east of Flamingo in Snake Bight. Over half of the Snake Bight 
kills were considered severe (1,000 to 100,000 fish reported as dead); most took place over 
the past 15 yrs. 
6.8. Fish catch changes 
The recorded history of fishing in Florida Bay and the Florida Keys can be traced back to the 
Caloosa Native Americans at the time of the early Spanish explorers (Tilmant, 1989). Native 
Americans from the Upper Keys grew and exported fish to Cuba and early explorers reported 
excellent fish catches in the Keys. Prior to the 1940s, fishing was largely subsistence 
oriented. Fishing activities increased during the 1950s and commercial activities reached a 
peak in the late 1970s. During this time, fishing guides became concerned with declining catches 
(Thayer and Chester, 1989). Evidence of the effect of salinity changes on the fish population of 
Florida Bay is circumstantial but there is evidence that the population size and behavior of 
several species have changed in recent years (Boesch et al., 1993). These effects do not seem 
to extend to the open areas of the Bay. 
Bohnsack et al., (1994b) examined data from commercial, recreational, and marine life 
fisheries in Monroe County. Invertebrates comprised the majority of commercial landings. In 
1992, the total reported commercial landings were composed of 52% invertebrates, 28% reef 
fishes, and 21% non-reef fishes. Landings for some species varied greatly over time. Total 
commercial and recreational catches of reef and non-reef fish for Monroe County are shown in 
Figure 6. The most conspicuous declines were for pink shrimp, combined grouper, and king 
mackerel (Figure 7), while the most conspicuous increases were for amberjack, stone crab, 
blue crab, and yellowtail snapper (Figure 8). Landings of spiny lobster have generally remained 
constant. Fisheries closed to harvest included queen conch, Nassau grouper, jewfish, and stony 
corals. Effective fishing effort has increased over time with more participants and more 
effective fishing technology. Since 1965, the number of registered private recreational vessels 
has increased over six times, while the number of commercial and headboat vessels has 
remained stable. The number of management actions have continually increased and become 
more restrictive with increased fishing effort. 
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