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Biologists research, monitor and record the long-term history and trends of Florida’s freshwater fish populations.

The Fish and Wildlife Research Institute (FWRI) Freshwater Fisheries Research section began a Long-Term Monitoring Project for Florida’s lakes in 2006, adding river systems in 2010. Researchers’ primary objective is to track freshwater fisheries trends over time, using standardized methods that insure the integrity of the data collected across the state. This information can then be used to assess the overall health of Florida freshwater fisheries, direct research efforts and make management decisions.

Each year, FWRI biologists collect data on the fish community, sport fisheries and aquatic habitat of more than 60 lakes and rivers statewide. They add the information to a large database where it is available for use in future studies or evaluations conducted by researchers and fisheries managers. As of 2014, the database contained nearly 1 million fish data observations, and the number will continue to grow as the project expands.

Fish Collection Methods

Biologists with FWRI, as well as other FWC divisions, use a variety of methods to sample freshwater fish communities. The type of equipment used depends on the target species, sampling location and habitat. Researchers commonly use the following types of equipment to collect fish in Florida’s lakes and rivers:

  • Electrofishing is used to collect fish in shallow water, 2-6 feet, during the fall. Since monitoring began, the most common species collected by electrofishing have been largemouth bass (Micropterus salmoides) and bluegill sunfish (Lepomis macrochirus), which were found each year in every lake sampled.
  • Fyke nets – small mesh nets comprised of a series of chambers designed to corral fish – are used to sample shallow areas that are difficult to reach by boat. Since incorporating their use into the project in 2008, researchers have collected more than 50 species of fish with fyke nets. These nets tend to target smaller fish like mosquitofish (Gambusia holbrooki) and juvenile warmouth (Lepomis gulosus).
  • Gill nets are tall stationary nets used to sample in deeper water where pelagic (open-water) species such as shads (Dorosoma spp.) and black crappie (Pomoxis nigromaculatus) are found. The nets are comprised of 25-foot panels of varying mesh sizes designed to collect fish of various sizes and body shapes. Gill nets were officially added to the project in 2009 and have been used in 24 lakes throughout the state. Although gizzard (D. cepedianum) and threadfin shad (D. petenense) tend to dominate gill-net catches from December to March, bluegill and black crappie have been collected in the most water bodies.

Importance of Monitoring Data

Using the above methods, biologists monitor and measure the following:

  • species diversity – an index of the number of species and abundance of each that make up a community
  • species richness – a component of species diversity that represents the number of different species present in the community
  • catch rate – an index used to estimate the relative abundance or density of fish, and can include values for all fish (total catch rate) or groups of fishes (e.g., catch rates of sport fishes or nonnative fishes)

Although researchers have recorded variations from one year to the next, especially within individual lakes, most have remained relatively stable on a statewide level. For example, biologists sampling lakes with electrofishing from 2007 to 2010 found the average number of species for all water bodies consistently ranged from 18 to 21.

The long-term monitoring project is another opportunity for scientists to research, monitor and record the history of the freshwater fish communities that are valuable resources to the state of Florida. State, federal and academic personnel will use the data collected to develop management strategies and conduct related research as scientists produce a more complete picture of long-term trends.