HISTORY
September/October 2019 GASPARILLA ISLAND 49
As the old saying goes, “Fishermen go
where the fish are” and, by all accounts,
the fish populations of Charlotte Harbor
in the 18th, 19th, and early 20th centuries were
extraordinarily abundant. One of Florida's
principal estuaries, the harbor in its pristine state
must have provided an ideal habitat for many
species of fish.
The photic zone – a relatively thin layer of
water that can be penetrated by light – is an
ocean's primary production area. In the photic
zone, growth rate depends on the intensity of
light and the supply of available nutrients. When
its waters are sufficiently clear and placid,
Charlotte Harbor is shallow enough to permit
transmission of abundant light to the
phytoplankton (minute plant life) and to the sea
grasses that provide a habitat favorable to fish.
Three major rivers, the Myakka, Peace and
Caloosahatchee, flow into the estuarine system,
delivering the nutrients needed to replace
those used up by the harbor's teeming marine
life. These freshwater streams also provide the
zones of reduced salinity that some fish,
especially juvenile forms, require.
Unfortunately, fish-nursery conditions in
Charlotte Harbor are not as favorable as they
once were. Ecologists report that, overall, the
Harbor's seagrass meadows declined by about
29 percent between 1945 and 1982. A little
more than half of this reduction was found in
Pine Island Sound, Matlacha Pass and San
Carlos Bay. An adverse impact on the estuary's
seagrass – probably transient – appears to have
resulted from dredging associated with
construction of the Intracoastal Waterway and
the Sanibel Causeway.
Later studies have shown short-term ups and
downs in the health of the Harbor's seagrass
meadows (sometimes related to excessive
rainfall or drought), but, since 1982, it has not
been possible to document a long-term
downward trend. One can only speculate on
what the total decline may have been during
the 20th century, which saw an accelerating
human population growth and a large
expansion of phosphate mining operations in
the Peace River basin. Die-off in seagrass –
when it occurs – is attributable in considerable
part to overall changes in drainage patterns,
dredging
activities, and
introduction of
massive quantities
of sewage
pollutants and
storm-water
runoff, with a resulting increase in the dissolved
and suspended load of particulate matter in the
Harbor.
All of the foregoing factors – and others –
could have acted to increase the water's turbidity,
reduce its ability to transmit sunlight, and thereby
contribute to the loss of seagrass meadows in the
deeper waters of the Harbor. The anticipated
result? Fewer fish.