Sampling Freshwater Fish Communities with Electrofishing

Biologists use electrofishing to monitor near-shore fish communities in Florida’s lakes.

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Biologists weigh and measure each fish collected during a long-term monitoring electrofishing trip.

Biologists with the Fish and Wildlife Research Institute (FWRI), as well as other FWC divisions, use a variety of methods to sample freshwater fish communities, depending on the target species, sampling location and habitat.

Electrofishing is a widely used sampling method that stuns fish for a short period of time. This technique allows researchers to handle specimens for data collection and return them safely to the water. As part of FWC’s long-term monitoring program, biologists use electrofishing to sample 25 different locations within a lake each fall. Every fish is identified, counted and measured. The types and numbers of fish they collect can answer a lot of questions about the fish community, for example:

  • Is there enough prey for our big game fish to eat?
  • Are there too many small fish and not enough big fish for our anglers to catch?
  • Is the fish community evenly balanced, or is it made up of only a few species?
  • Are there are any invasive species present and are they influencing the fish community? 

Each year since 2006, FWC biologists have collected electrofishing samples from at least 30 lakes throughout the state. In that time, they logged 119 different fish species with an average of 21 species found in any given water body. Some of these species are observed every year. Biologists call these typical species. The most common of these species are two major sport fishes: bluegill and largemouth bass. They are collected in nearly every system, every year. Bluegill and largemouth bass, along with an important prey fish, threadfin shad, make up about 50 percent of the total fish collected. 

Looking at this list of common fish species reveals several interesting facts about Florida’s fish communities.

Saltwater Species

Species like the Atlantic needlefish, common snook, hogchoker, and ladyfish, can be found in freshwater bodies that have a connection to the ocean. Some species, like the American eel, actually enter freshwater systems as part of their lifecycle. This species will grow and mature in freshwater, then migrate to oceanic waters to spawn.

Exotic Species

Some fish species are not native to Florida and only live here because humans transported them. Brown hoplo and suckermouth catfishes, which are commonly sold in the aquarium trade, often become established in Florida systems when owners release their pet fish in a local waterway. The most common non-native fish that biologists encounter is the blue tilapia, which is found in nearly 40 percent of lakes each year.

Dinosaurs

Among the typical species are several very old species. Gars and bowfin are living remnants of a prehistoric group of fishes that inhabited our waters over 100 million years ago. Both species have the ability to gulp air at the surface and get oxygen from their swim bladder, allowing them to live in very low oxygen conditions.

Florida’s freshwaters are full of interesting fishes that fill specific roles in our aquatic ecosystems, but their interactions with each other and their environments can be difficult to describe. Biologists at FWC use long-term monitoring data to learn more about these interactions and predict how future changes may impact these fish communities.

 

This table lists all of the species that FWC biologists have collected in fall electrofishing samples since 2006.

 

Common Name

Scientific Name

Percentage of Lakes

Percentage of Catch

Bluegill

Lepomis macrochirus

100

29

Largemouth bass

Micropterus salmoides

100

7

Redear sunfish

Lepomis microlophus

94

3

Florida gar

Lepisosteus platyrhincus

88

3

Bowfin

Amia calva

88

2

Golden shiner

Notemigonus crysoleucas

86

4

Brook silverside

Labidesthes sicculus

80

5

Lake chubsucker

Erimyzon sucetta

79

1

Warmouth

Lepomis gulosus

79

<1

Mosquitofish

Gambusia holbrooki

74

6

Threadfin shad

Dorosoma petenense

71

13

Seminole killifish

Fundulus seminolis

69

3

Black crappie

Pomoxis nigromaculatus

69

<1

Gizzard shad

Dorosoma cepedianum

64

2

Brown bullhead

Ameiurus nebulosus

57

<1

Chain pickerel

Esox niger

53

<1

Spotted sunfish

Lepomis punctatus

49

<1

Blue tilapia

Oreochromis aureus

44

<1

Bluefin killifish

Lucania goodei

42

<1

Dollar sunfish

Lepomis marginatus

42

<1

Inland silverside

Menidia beryllina

37

2

Taillight shiner

Notropis maculatus

37

<1

Redbreast sunfish

Lepomis auritus

34

<1

Golden topminnow

Fundulus chrysotus

34

<1

Sailfin molly

Poecilia latipinna

33

<1

Longnose gar

Lepisosteus osseus

33

<1

Yellow bullhead

Ameiurus natalis

31

<1

Atlantic needlefish

Strongylura marina

29

<1

White catfish

Ictalurus catus

28

<1

Pugnose minnow

Opsopoeodus emiliae

26

<1

Swamp darter

Etheostoma fusiforme

26

<1

Least killifish

Heterandria formosa

21

<1

Channel catfish

Ictalurus punctatus

20

<1

Bluespotted sunfish

Enneacanthus gloriosus

20

<1

Striped mullet

Mugil cephalus

19

<1

Sailfin catfishes

Pterygoplichthysspp.

17

<1

American eel

Anguilla rostrata

16

<1

Lined topminnow

Fundulus lineolatus

13

<1

Brown hoplo

Hoplosternum littorale

10

<1

Flagfish

Jordanellafloridae

9

<1

Redfin pickerel

Esox americanus

9

<1

Spotted sucker

Minytrema melanops

6

<1

Coastal shiner

Notropis petersoni

5

<1

Spotted gar

Lepisosteus oculatus

5

<1

Hogchoker

Trinectes maculatus

5

<1

Common carp

Cyprinus carpio

5

<1

Grass carp

Ctenopharyngodon idella

5

<1

Weed shiner

Notropis texanus

4

<1

Ladyfish

Elops saurus

4

<1

Common snook

Centropomus undecimalis

4

<1

Pirate perch

Aphredoderus sayanus

4

<1

Blackbanded darter

Percina nigrofasciata

3

<1

Blacktail shiner

Cyprinella venusta

2

<1



FWC Facts:
Manatees feed for 6 to 8 hours daily, consuming about 4 to 9 percent of their body weight in wet vegetation, such as seagrass and other aquatic plants.

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