Every so often you see Texas Parks & Wildlife (TPWD) news release giving information on the fish population at a certain Texas lake. How does TPWD biologists figure out how many fish are in a lake, what species are doing well and what are the size range?
Inland Fisheries crews conduct one of several kinds of surveys.
Creel surveys:
Let's take Bridgewater as an example. TPWD biologists conduct a creel survey on Lake Bridgeport beginning in September and wrap up in May of 2014. Creel surveys are conducted by contacting anglers in person while they are on the lake fishing or when they are at a boat ramp. The creel survey will determine harvest of all fishes from the lake, especially largemouth bass and Palmetto bass, during the period. (As part of an every-other-year stocking plan, 59,756 Palmetto bass fingerlings were stocked in May 2013.) Other information such as monetary value of the fishery, sizes of fish harvested and caught and angler residence will also be determined. After all the data are compiled and analyzed, a management report will be written which summarizes the results and recommends strategies to improve or maintain the fishery. The report will be available late summer of 2014.
Electrofishing:
An electrofishing boat (also known as a shocking boat) is used to sample the fish in Lake Bridgeport. Electrofishing works best at night in six feet of water or less. Biologists expect to collect a wide range of sizes of largemouth bass, smallmouth bass, and spotted bass from the lake. The fish are collected using long dip nets on the bow of the lighted electrofishing boat during the sampling. All bass are weighed and measured. A small sample of largemouth bass will be checked for the presence of Florida largemouth bass genes. All forage species are measured and released. Records are kept of all fish collected. Comparing numbers and sizes of fish collected over a period of years shows population trends and growth rates.
Trap net:
Bridgeport's crappie population is sampled with a piece of gear called a trap net. It works like a minnow trap and funnels the crappie into the net, where they cannot escape. The net is set in the afternoon and taken out the next morning. The crappie are weighed, measured and released.
Gill netting:
Finally, channel catfish, Palmetto bass and white bass numbers are sampled with gill nets. Gill nets are 125 feet long by 8 feet deep and entangle fish with varying mesh sizes. Gill nets are set in the afternoon and taken out the next morning. Once again the target fish will be weighed, measured and released, if possible.
Not all lakes are surveyed every year, but chances are good that TPWD boat you see on the lake in the fall and winter will not carry a game warden but a fisheries biologist working to make fishing better. Information from these surveys is used to guide management decisions for the reservoir, such as what kind and how many fish to stock.
Photo: Caption/Information: TPWD Inland Fisheries biologists collect and measure fish from reservoirs using electrofishing at night, when fish tend to be in shallow water and close to shore.
Photo credit: Larry D. Hodge, © Texas Parks and Wildlife Department