U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2004-3131

November 2004

Inventory of Freshwater Fish Species within 

Big Cypress National Preserve: 

The Basis for a Long-Term Sampling Program

Printed on recycled paper

Introduction

The Big Cypress ecosystem forms a largely undeveloped 

landscape in southwestern Florida. The ecosystem includes 

three major habitats: seasonally flooded marshes, forested 

wetlands and upland pine habitats, all of which are intersected 

by manmade canals. Much of the landscape lies within the 

Federally protected Big Cypress National Preserve (BCNP), 

which is managed by the National Park Service (fig. 1). To 

understand this ecosystem, knowledge about the ecology of its 

fishes is especially important, because they are the most numerous vertebrates within the Preserve, and provide food for predators such as wading birds and alligators. The hydrologic change 

resulting from surface-water drainage and impoundment within 

the system has probably decreased fish biomass and numbers, 

and altered the timing and the areas of fish availability to predators (Duever and others, 1986). In addition, non-native fish 

species have colonized natural and disturbed habitats of the Big 

Cypress ecosystem during the past three decades, because the 

local climate and habitats are favorable for their colonization and 

survival (Loftus and Kushlan, 1987). 

Only recent baseline data exist for fish communities in the 

Big Cypress system, and these data are relatively scarce. The 

first collections were made in the 1960s and 1970s during 

studies of the prey populations for wading birds (Kahl, 1964; 

Browder, 1976; Kushlan, 1974). The composition and distribution of native and introduced fishes from the southern areas of 

the Preserve were reported on by Loftus and Kushlan (1987). 

Limited collections were made by W.F. Loftus (National Park 

Service, written commun., 1987), and by Dalrymple (1995). 

Small quantitative datasets on fish communities exist only for 

Corkscrew Swamp (Carlson and Duever, 1977), and coastal 

habitats in the southern Big Cypress Swamp (Carter and others, 

1973). The present study, funded by the USGS Greater Everglades Priority Ecosystems Science Program, in cooperation 

with BCNP, was conducted to produce a complete inventory of 

fishes for the Preserve, and to test methods for quantitatively 

sampling those habitats. 

Methods of Investigation

Big Cypress fishes were inventoried throughout the period 

from October 2002 through June 2004 (Ellis and others, 2003). 

We collected multiple samples in all major aquatic habitats in 

the Preserve. We also took samples during several seasons at 

many locations (table 1). Most data, however, were collected 

during the winter/spring dry season in canals and other deepwater habitats. The transition between the wet and dry seasons 

coincided with the time of highest species richness in many 

habitats because fishes were concentrating, but had not yet 

experienced high mortality. We emphasized sampling during 

this period to record the maximum number of species living 

within each habitat. In addition, shallow wetlands were 

sampled during the summer and fall high-water period. 

Because much of BCNP is inaccessible by road, helicopter, 

swamp buggy, and all-terrain vehicles were used to reach 

interior sites within the Preserve. 

The diversity of habitats in BCNP presented challenges to 

the development of a comprehensive sampling regime. The 

effectiveness of any method varies by habitat, and each has 

inherent biases. To compensate, we used several techniques 

when taking a sample. Traps and nets provided a means of 

Figure 1. Map showing Big Cypress National Preserve.

Table 1. Number of 

samples per habitat type

MONROE COLLIER

PALM BEACH

HENDRY

MIAMI-DADE

BROWARD

MARTIN

ST. LUCIE

OKEECHOBEE

HIGHLANDS

GLADES

SARASOTA DE SOTO

CHARLOTTE

LEE

COLLIER COUNTY

HENDRY COUNTY

PALM BEACH COUNTY

BROWARD COUNTY

BROWARD CO

Miami

Lake

25°

26°

27°

83° 82° 81° 80°Atlantic Ocean

TAMIAMI CANAL

Naples

Gulf of Mexico

0

0

25

25 50 KILOMETERS

50 MILES

Okeechobee

Big Cypress National Preserve

Everglades National Park

Direction of surface-water flow

Road

Canal

Control Structure

EXPLANATION

S-190

HISTORIC

EVERGLADES

Loop

Road

11 Mile

Road

Turner River

Road

Birdon Road

S-190

S-140

S-344

L28

Levee

L28 North

Levee

S-343A

S-343B

S-12A

L28

Interceptor

Levee

0

0

10 MILES

10 KILOMETERS

41

75

29

 Habitat

Number of 

 samples

Canals 155

Cypress forest 49

Freshwater marsh 42

Herbaceous prairie 33

Sloughs/ponds/rivers 25

Cypress prairie 15

Mixed swamp forest 14

Coastal marshes 10
sampling with a standardized unit of effort (soak time), 

and were suitable for most habitats. We used Gee-type 

minnow traps, box traps, collapsible mesh traps, and 

Breder traps. Soak times were generally 24 hours, 

although 1-hour sets were also performed. Small-fish 

traps were fished unbaited and relied on encounter by 

the fish to generate captures. Hoop nets were normally 

fished unbaited, but were baited for 24-hour periods 

in deep-water areas to sample larger fishes. We used 

experimental gill nets to sample canal fishes by deploying two nets in tandem, each with four 2.4-meter deep 

x 1.8-meter wide panels. The first net had panels with 

bar-mesh sizes of 1.2, 2.5, 3.7, and 5 centimeters, and 

the second had meshes of 6.2, 7.6, 8.8, and 11 centimeters. Nets were typically set from 1 to 4 hours.

We employed two electrofishing rigs to sample 

fishes. The first was a boat-mounted Smith-Root type 

6A electrofisher with a maximum current output of 

1,008 volts dc at 120 pulses per second. It performed 

well in sampling canals, but was too large for use in 

vegetated habitats. In forested habitats and marshes, 

we sampled with a small barge carrying a Smith-Root 

model 2.5 Gas-powered Pulsator (GPP) electrofisher 

having a maximum current of 1,000 volts dc at 

120 pulses per second. Samples were standardized to 

300 seconds of total shock time. 

We also maintained sight records for species 

observed but not captured, which we were able to 

positively identify. Extensive collections of voucher 

specimens were saved to document the identities of 

BCNP fishes, and they are stored at the South Florida 

Collection Management Center repository at Everglades 

National Park.

Habitat Classification

Sampling was planned using a stratified design based 

on habitat category. The habitat-classification scheme 

was based on the seasonally inundated habitats identified by Duever and others (1986). Eight broad habitat 

categories were used, based on dominant vegetation 

and hydroperiod (National Park Service, 1991); six of 

these are subject to seasonal dry-down. The habitats are 

ranked by hydroperiod from longest to shortest: 

• Cypress forest — includes bald cypress — includes bald cypress Taxodium 

distichum and pond cypress Taxodium ascendens.

• Mixed swamp forest — forested wetlands dominated by hardwoods (Duever and others, 1986).

• Freshwater marshes — wetlands dominated by a 

variety of grasses and sedges.

• Coastal marshes — herbaceous wetlands that seasonally vary between fresh and brackish salinities

(National Park Service, 1991).

• Cypress prairie — wetland with an open canopy of 

sparse dwarf pond cypress (National Park Service, 

1991).

• Herbaceous prairie — short-hydroperiod wetlands 

characterized by a variety of grasses (Duever and 

others, 1986). 

Species

CanalsSloughs, ponds, riversMixed swamp forestFreshwater marshCypress forestCypress prairieHerbaceous prairieCoastal marshesAll wetlandsFreshwater wetlandsDeep-water habitats 

American eel x x - - - - - - - - x

Atlantic needlefish x - - - - - - - - - x

black acara x x x x x x x x x x -

black crappie x - - - - - - - - - x

blue tilapia x x - x x x - x x x -

bluefin killifish x x x x x x x x x x -

bluegill x x x x x - - x x x -

bluespotted sunfish x x x x x - x x x x -

bowfin x x - - x - - - x x -

brook silverside x x - x x x x - x x -

brown bullhead x - - - - - - - - - x

brown hoplo x - - - - - - - - - x

clown goby x - - - - - - x x - -

coastal shiner x - - - - - - - - - x

crested goby x - - - - - - - - - x

crevalle jack x - - - - - - - - - x

dollar sunfish x x x x x x x x x x -

Everglades pygmy 

sunfish x x x x x - x - x x -

flagfish x x x x x x x x x x -

Florida gar x x x x x x x - x x -

frillfin goby x - - - - - - - - - x

gizzard shad x - - - - - - - - - x

golden shiner x x x x - - - - x x -

golden topminnow x x x x x x x x x x -

gray snapper x - - - - - - - - - x

gulf killifish x - - - - - - x x - -

hardhead catfish x - - - - - - - - - x

hogchoker x x - - - - - x x - -

inland silverside x - - - - - - x x - -

jewel cichlid x - - x - - x - x x -

ladyfish x - - - - - - - - - x

lake chubsucker x x - - x - - - x x -

largemouth bass x x x x x x x x x x -

least killifish x x x x x x x - x x -

marsh killifish x x x x x x x x x x -

Mayan cichlid x x x x x x x x x x -

mosquitofish, eastern x x x x x x x x x x -

oscar x x - - - - x - x x -

pike killifish x x x x x x x x x x -

pinfish x - - - - - - - - - x

rainwater killifish x x - - - - - x x - -

red drum x - - - - - - - - - x

redear x x x x x x - x x x -

redfin needlefish x - - - - - - - - - x

redfin pickerel - - - - x - - - x x -

sailfin molly x x x x x x x x x x -

Seminole killifish x x - x - - - - x x -

sharksucker x - - - - - - - - - x

sheepshead x - - - - - - - - - x

sheepshead minnow x - - x - - x x x x -

snook x x - - - - - - - - x

spotted sunfish x x x x x x x - x x -

spotted tilapia x x x x x x x x x x -

striped mojarra x x - - - - - - - - x

striped mullet x x - - - - - x x - -

swamp darter x - - - - - - - - - x

Table 2. Distribution of fish species by habitat
littorale), and the clariid walking catfish (Clarias 

batrachus). This study is the first to document 

Hemichromis and Hoplosternum from the Preserve, 

both of which are expanding their ranges southeastward (fig. 2). The number of non-indigenous species 

in BCNP has grown from three in the late 1970s 

(Loftus and Kushlan, 1987) to nine in 2004. Additional 

non-native species are present in the canal system near 

BCNP boundaries, which supports the hypothesis that 

this trend will continue. The Mayan cichlid is an example of a successful non-indigenous fish that has spread 

throughout much of the Preserve, where its population 

is especially large in canals. The potential ecological 

consequences of these invasions are uncertain.

The freshwater marshes and forested wetlands 

shared similar fish assemblages. Of the 33 species 

found in these habitats, 16 were common to all. Small 

fishes utilized shallow-water areas such as herbaceous 

prairies and cypress prairies when those habitats were 

inundated. As the shallow habitats dried, the relative 

abundance of those fishes in nearby swamp forests and 

cypress strands appeared to increase. This pattern was 

reported by Carlson and Duever (1977) for flagfish 

(Jordanella floridae) and least killifish (Heterandria 

formosa) populations during the annual dry-down of 

Corkscrew Swamp, and also occurs in the Everglades 

wetlands (Loftus and Kushlan, 1987). Small-bodied 

species, such as the eastern mosquitofish (Gambusia 

holbrooki), were often the most ubiquitous and 

numerous fishes in the samples (fig. 3).

Canals held the most diverse assemblage of fishes; 

62 of the 64 species documented in the Preserve 

occurred within this habitat. Although this relatively 

high species richness reflects a greater sampling effort 

in this habitat compared to other habitats (table 1), it 

also is related to the presence of fish species that 

Figure 2. Newly established, introduced fishes in Big Cypress National 

Preserve include the Brown Hoplo catfish (Hoplosternum littorale) and 

Jewel Cichlid (Hemichromis letourneauxi). Copyrighted image used 

with permission.

Species

CanalsSloughs, ponds, riversMixed swamp forestFreshwater marshCypress forestCypress prairieHerbaceous prairieCoastal marshesAll wetlandsFreshwater wetlandsDeep-water habitats 

tadpole madtom - - x - - - - - x x -

taillight shiner x - - - - - - - - - x

tarpon x x - - - - - - - - x

tidewater mojarra x - - - - - - - - - x

timucu x - - - - - - - - - x

walking catfish x x x - - - - x x x -

warmouth x x x x x x x x x x -

yellow bullhead x x - x x - x - x x -

Table 2. Distribution of fish species by habitat—Continued

Two additional habitats hold water year-round:

• Canals — deep-water refuges for fishes during the dry 

season, from which they disperse in the wet season.

• Sloughs/ponds/rivers — natural, persistent water bodies. Ponds and rivers comprise a small geographic area 

of BCNP, but include important features as such as Deep 

Lake, Mud Lake, and Turner River. 

Results and Discussion

From our sampling efforts, we identified 64 fish species 

(table 2). Fifty-five species are native to North America, and 

include species-rich groups such as sunfishes (Centrarchidae), 

killifishes (Cyprinodontidae and Fundulidae), livebearers 

(Poeciliidae), and catfishes (Ictaluridae). We also recorded nine 

nonindigenous species, most of which are in the cichlid family: 

Oscar (Astronotus ocellatus Astronotus ocellatus), black acara (Cichlasoma bimaculatum), Mayan Cichlid (Cichlasoma urophthalmus), blue tilapia 

(Oreochromis aureus), spotted tilapia (Tilapia mariae), and 

Jewel Cichlid (Hemichromis letourneauxi). Three non-cichlids 

were recorded: the poeciliid pike killifish (Belonesox belizanus), 

the callichthyid brown hoplo catfish (Hoplosternum 

Loop

Road

11 Mile

Road

Turner River

Road

Birdon Road

S-190

S-140

S-344

L28

Levee

L28 North

Levee

S-343A

S-343B

S-12A

L28

Interceptor

Levee

41

75

29

EXPLANATION

Fish Sample

Location

Brown hoplo

Jewel cichlid

Big Cypress

National Preserve

0

0

10 MILES

10 KILOMETERS

EXPLANATION

Fish Sample

Location

Mosquitofish

Loop

Road

11 Mile

Road

S-190

S-140

S-344

L28

Levee

L28 North

Levee

S-343A

S-343B

S-12A

75 Big Cypress

National Preserve

0

0

10 MILES

10 KILOMETERS

29

Figure 3. Distribution of the eastern mosquitofish, Gambusia holbrooki, 

was ubiquitous in Big Cypress National Preserve fish samples.
typically inhabit deep, open-water habitats, and to marine fishes 

that tolerate a wide range of salinities (“euryhaline” species). 

Open-water species included the brown bullhead (Ameiurus 

nebulosus), gizzard shad (Dorosoma cepedianum), redear 

(Lepomis microlophus), and black crappie (Pomoxis nigromaculatus), which are rarely found in BCNP wetlands. The marine 

invaders penetrate inland from the Gulf of Mexico through 

coastal canals. They do not seem to enter wetland habitats 

other than by way of channels in coastal marshes. Species in 

this category include the various needlefishes (Strongylura 

spp.), mojarras (Eugerres and Eucinostomus), and gobies 

(Bathygobius, Lophogobius and Microgobius), as well as snook 

(Centropomus undecimalis), gray snapper (Lutjanus griseus) 

and tarpon (Megalops atlanticus). The diversity and numbers 

of non-indigenous fishes are high in canals, especially during 

the dry season. Coastal marshes are also used by euryhaline 

species, and during the wet season, support most of the freshwater species found in the Preserve. Euryhaline species present 

in this habitat include clown goby (Microgobius gulosus), gulf 

killifish (Fundulus grandis), rainwater killifish (Lucania parva), 

and striped mullet (Mugil cephalus).

Sloughs, ponds, and rivers are the only natural habitats 

that retain water year-round. Few rivers exist within BCNP, 

although Turner River drains its southwestern portion. Lakes 

are also uncommon within BCNP; however, constructed borrow 

pits function as lakes. Both habitats, particularly those with 

hydrologic connections to the canal system, are home to large 

euryhaline and freshwater species. An example is the population of tarpon and Florida gar inhabiting Deep Lake—a flooded 

sinkhole adjacent to the Barron Collier Canal. 

Loftus and Kushlan (1987) reported 34 native and 3 nonindigenous species from their collection efforts, compared to 

56 native and 9 non-native species in the present study. However, a similar number of species were collected from the freshwater wetlands in both studies (29 in the earlier study and 33 in 

this study). The increase in species in the present study 

is the result of much greater sampling effort, particularly in 

coastal canals and rivers, and a larger sampling area. Loftus and 

Kushlan (1987) sampled only the southern area of BCNP, which 

lies south of U.S. Highway 41. Loftus and Kushlan (1987) 

found that species composition within the Big Cypress Everglades ecosystems were nearly identical; our data support this 

finding. 

 Several previously reported species within the Preserve were 

not collected in the present study. W.F. Loftus (National Park 

Service, written commun., 1987) found diamond killifish (Adinia 

xenica) and naked goby (Gobiosoma bosc). The survey by 

Dalrymple (1995) of the northern BCNP area included reports 

of chain pickerel (Esox niger) and channel catfish (Ictalurus 

punctatus) in the L-28 Canal. None of these species appear to 

be widespread in BCNP. 

Continuing Research

This inventory is the initial step in a fish research program 

for BCNP. Although we identified effective methods for 

sampling various habitats during the inventory, the sampling 

did not include quantitative measurements of population 

densities. Quantitative data describing fish-community 

dynamics in the Big Cypress Swamp are lacking, except for 

short-term studies in the Corkscrew Swamp (Carlson and 

Duever, 1977) and southern Big Cypress region (Carter and 

others, 1973). We have begun a long-term program to study 

community composition and dynamics before and after restoration actions change hydrologic patterns in the region. Our 

current work includes repetitive sampling five times per year to 

compare baseline community data at sites within areas likely to 

be affected by hydrologic changes with those that will experience little effect. We are using equipment that provides density 

estimates for fishes in forested wetlands, especially quadrat 

drop traps. Sites are also sampled with drift-fence/minnowtrap arrays, with electrofishing, or other nets. Results from 

these quantitative collection efforts will help us better understand the functioning of the fish community in this large, 

complex ecosystem. 

References Cited

Browder, J.A., 1976, Water, wetlands, and wood storks in southwest 

Florida: Gainesville, University of Florida, Ph.D. dissertation, 406 p.

Carlson, J.E., and Duever, M.J., 1977, Seasonal fish population fluctuations in a South Florida swamp, in Proceedings of the Southeastern 

Association of Fish and Wildlife Agencies, v. 31, p. 603-611.

Carter, M.R., Burns, L.A, Cavender, T.E., and others, 1973, Ecosystems analysis of the Big Cypress Swamp and estuaries: U.S. Environmental Protection Agency, Region IV: Atlanta, Georgia, U.S. 

Environmental Protection Agency Report 904/9-74-002. 

Dalrymple, G.H., 1995, Wildlife Inventory for Baseline Studies of 

the Addition Lands of the Big Cypress National Preserve: Miami, 

Report prepared for Florida International University. 

Duever, M.R., Carlson, J.E., Meeder, J.F., and others, 1986, The Big 

Cypress National Preserve: New York, National Audubon Society, 

455 p.

Ellis, G., Zokan, M., Lorenz, J., and Loftus, W.F., 2003, Inventory of 

the freshwater fishes of the Big Cypress National Preserve, with a 

proposed plan for a long-term aquatic sampling program: Annual 

Project Report to the USGS Priority Ecosystems Science Program, 

Davie, Florida, 104 p.

Kahl, M.P., 1964, Food ecology of the wood stork (Mycteria americana) in Florida: Ecological Monographs, v. 34, p. 97-117.

Kushlan, J.A., 1974, Effects of a natural fish kill on the water quality, 

plankton, and fish population of a pond in the Big Cypress Swamp, 

Florida: Transactions of the American Fisheries Society, v. 103, 

p. 348-352.

Loftus, W.F., and Kushlan, J.A., 1987, Freshwater fishes of southern 

Florida: Bulletin of the Florida State Museum, Biological Sciences, 

v. 31, p. 147-344.

National Park Service, 1991, Big Cypress National Preserve General 

Management Plan and Final Environmental Impact Statement: 

Ochopee, Florida.

 For further information contact: 

William F. Loftus

U.S. Geological Survey 

Florida Integrated Science Center 

40001 State Road 9336 

Homestead, FL 33034 

305-242-7835; 305-242-7836 (fax) E-mail: bill_loftus@usgs.gov

Greg Ellis, Marcus Zokan, and Jerome Lorenz

National Audubon Society

Tavernier Science Center