Gillnet surveys used to monitor fish populations
Galen Jons, Fisheries Biologist

The Texas Parks and Wildlife (TPW) Inland Fisheries division (our Abilene office is one of fifteen Inland Fisheries districts located around the state) uses gillnets to capture and survey populations of open-water fish, such as catfish and striped, white and hybrid striped bass (temperate basses). Black basses, e.g. - largemouth bass, are rarely caught in gillnets.

We set gillnets in random locations around the lake, with some nets set in open water and some nets set near the shoreline. We collect target species from the nets and count, weigh and measure them to get population data. While we release some of these fish alive, some are also sacrificed to collect age and growth information. This requires removal of ear bones (otoliths) from the fish's skull. The otoliths contain markings that allow us to age the fish (like growth rings on a tree trunk). By analyzing population abundance, structure and age and growth data, we can determine if the fish populations are remaining healthy or if there are impending problems.

We recently did our spring gillnet survey at Lake Graham, and the results indicate good populations of white bass, hybrid striped bass and channel catfish. We captured these fish all over the lake, and all of the fish looked fat and healthy. We will analyze the age and growth data in a few weeks and expect that those results will back up what looks like very healthy populations. We also captured blue catfish for the first time in that lake. We expect a blue catfish fishery to develop there quickly, as the habitat seems to favor these fish. Many anglers prefer blue catfish over channel catfish as they tend to grow larger and have a firmer, whiter flesh.

 

We will gillnet Lake Ft. Phantom Hill this week. We've been using gillnets to monitor the blue catfish population at Lake Ft. Phantom Hill over the years. As many local anglers can attest, we've had an abundance of small blue catfish in that lake for the last five years or so. We're thinking that these fish are starting to get big enough for anglers to harvest, so this year's survey results should be interesting.

Next week we plan to conduct gillnet surveys at Hords Creek Lake, west of Coleman. Our main target in that lake is channel catfish. We've been tracking some marked catfish that we stocked back in 1998 to follow their growth and mortality. Unfortunately, the drought has put a damper on their growth, but it is still interesting to see how they're doing. This type of research may help to improve catfish fisheries all over the Big Country.

Gillnet surveys are a lot of work and are not very pleasant to do. However, they provide a wealth of information that fisheries managers can use to better manage and improve the fisheries. Our job is to make fishing better for the anglers of Texas, and this is an effective tool for helping us to do our job.

Funding for fisheries surveys and fish stocking is provided by the Federal Aid in Sport Fish Restoration Program, Project F-30-R of the TPWD Inland Fisheries Division.

 


 

 

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