Southern Biscayne Bay Nearshore Fish and Invertebrate Community Structure
David Kieckbusch, Michael Robblee, André Daniels
USGS, Water and Restoration Studies Center, Miami, FL
Joan Browder, Jeremy Hall
NOAA Fisheries, Southeast Fisheries Science Center, Miami, FL
Loss and/or degradation of coastal wetlands and nearshore estuarine habitats are
long-term threats to Biscayne Bay’s ecological function and its production of
natural resources. Because of its clear, shallow waters, Biscayne Bay’s benthic
community is a principal source of its productivity and diversity. The
seagrass/algae associated animal community, consisting of small forage fish,
juvenile gamefish, and invertebrates such as pink shrimp, Farfantepenaeus
duorarum, is particularly well developed in the shallow nearshore zone adjacent
to the mainland and may be dependent upon freshwater inflow. The purpose of
this study is to describe the spatial patterns of faunal community composition and
species abundance in relation to salinity in the shallow, nearshore habitats of
southern Biscayne Bay and ultimately to evaluate the influence of freshwater
discharge on community structure.
A random stratified sampling design is being employed to characterize the spatial
and temporal patterns of fish and invertebrate community structure in nearshore
habitats and to facilitate a throw-trap/commercial roller trawl comparison in the
adjacent deeper water commercial fishing zone. At present 54 randomly selected
sampling sites, distributed on an areal basis among three salinity strata and an
Elliot Key western shoreline control site, are being sampled bi-monthly. The
three salinity strata are each subdivided into zones north and south of Black Point,
while a subset of these sampling sites in deeper water are associated with the gear
comparison.
A 1m2 throw-trap suitable for sampling across the full range of water depths
observed in Biscayne Bay is being used to collect quantitative samples of fish and
macroinvertebrates. A commercial shrimper, using a 4.4 m roller trawl, is
sampling in water deeper than 1 m. Throw-trap and roller trawl sampling is
coordinated to affect the gear comparison. All fishes, caridean and penaeid
shrimp collected are identified, counted and sized as appropriate in the laboratory.
Each throw-trap sample is associated with habitat quantitatively using a variety of
techniques: visual, quadrat harvest and Braun Blanquet. An emphasis in this study
on coupling habitat (seagrass, algae, hardbottom) with fish and invertebrate
community structure recognizes the importance of habitat, particularly seagrass
habitat, in organizing benthic communities and to the nursery function of the bay.
Sampling was initiated in the fall of 2002. Preliminary fish results are available
characterizing the fish community in southern Biscayne Bay. Similar results are
available for caridean shrimp and the pink shrimp. Figure 1 compares fish caught
in the roller trawl net enclosed in a smaller mesh net referred to here as a sock.
The sock captures fish and shrimp that might otherwise pass through the roller
trawl net.
Fish abundance in the collections was relatively low with
averages/trawl of less than 8 for the most abundant species, Lagodon rhomboides,
the pinfish, and the yellowfin mojarra, Gerres cinereus. Figure 2 compares fish
Figure 1. Comparison of the fish caught with the roller trawl versus the sock.
caught with the throw-trap. The Elliot Key area serves as a potential control for
the western shoreline of Biscayne Bay where changes in salinity patterns due to
restoration of freshwater flow are expected. The fish fauna observed in Biscayne
Bay is similar to that observed in western Florida Bay with the exception that
parrotfish are present but absent in Florida Bay. With the exception that densities
are lower the fish community along the western shore of Biscayne Bay,
dominated by the rainwater killifish, Lucania parva, is typical of the seagrass
associated fish community in Florida Bay.
Figure 2. Comparison of the fish caught with the throw-trap north and south of
Black Point and along the western shore of Elliot Key.
These results are preliminary. More detailed analyses focusing on evaluating the
relationship of fish and invertebrates to salinity and habitat and comparing the
throw-trap and roller trawl gears will be presented.
Kieckbusch, David, USGS, Water and Restoration Studies Center, Miami, FL,
33178, Phone: 305-348-6997, Fax: 305-348-4096, david_kieckbusch@usgs.gov
Question 5