Illinois Natural History Survey - University of Illinois

Database Management and Analysis of Fisheries in Illinois

One of the goals of fisheries management is to maintain healthy fish populations while providing recreational fishing opportunities for the public. To accomplish a variety of fisheries management goals requires continuous feedback on habitat, fish population structure and abundance, and the fisheries they support. The Illinois Natural History Survey (INHS) Center for Aquatic Ecology has been working with the Illinois Department of Natural Resources (IDNR) Division of Fisheries to collect, manage, and analyze a wealth of fisheries information. This project, entitled Database Management and Analysis of Fisheries in Illinois, is supported through funding by the Federal Aid in Sportfish Restoration Program, the IDNR Division of Fisheries, the University of Illinois, and the Illinois Natural History Survey.

A primary component of the project is to collect information on the fisheries of lakes and streams in Illinois. This information is collected through angler surveys, often referred to as creel surveys. The INHS conducts creel surveys on approximately 15 lakes and streams statewide each year. These surveys typically run from mid-March through October for most lakes, but can extend into the winter months on lakes with ice fishing or on power plant cooling lakes, which are typically open to fishing all year. Surveys are conducted by interviewing anglers and periodically counting the number of anglers fishing the body of water at any given time. INHS scientists use these data to make estimates of the fishing pressure and harvest of sport fish in each lake or stream surveyed. These estimates are used by managers to estimate fishing mortality, angler catch rates, and size distribution of caught fish, thereby providing data necessary for evaluating harvest regulations and determining other management objectives. Information collected from these creel surveys is vital to understanding the quality of each fishery.

Jerry Tamborine (right) of INHS collecting creel survey information from an angler at Clinton Lake (DeWitt Co., Illinois).

Another important component of the project has been the development of a custom database software and analysis package, the Fishery Analysis System (FAS). This software is distributed to IDNR biologists statewide, who use it to enter and analyze the data collected from habitat and population surveys on Illinois streams and lakes. Estimation of stream index of biotic integrity and calculation of fish population size structure indices such as proportional stock density (PSD) are just a few of the important analytical tools contained in FAS. Additionally, FAS is used by INHS scientists to enter and analyze data collected from creel surveys. By combining many kinds of fisheries data into one common software package, FAS provides researchers and managers with the information necessary to manage, sustain, and improve the health of fisheries resources in Illinois lakes and streams.

Information contained in FAS is currently being used by project scientists to evaluate the effects of experimental harvest regulations on bluegill (Lepomis macrochirus). In 1999, IDNR imposed bag limit and length limit regulations for bluegill on several lakes in Illinois in an attempt to understand and correct for stunted growth. INHS conducted creel surveys on each of these study lakes prior to the experimental regulations, and researchers plan to return to survey these lakes in a few years to evaluate the effectiveness of the harvest regulations.

Recently, INHS scientists examined the relationship of population size structure and abundance indices with angler catch rates of largemouth bass (Micropterus salmoides). Preliminary results suggest that angler catch rates of catchable-sized largemouth bass in the spring can be estimated from PSD and catch-per-unit-effort (CPUE) estimates collected via electrofishing surveys in the previous fall. Using this information, IDNR fishery managers will be able to predict trends in any fishery and will be able to adjust stocking levels and harvest limits accordingly.

Darren M. Benjamin and David P. Philipp, Center for Aquatic Ecology

Charlie Warwick, editor

Illinois Natural History Survey

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