Texas Parks & Wildlife Magazine   



We’ve been trying to outsmart fish forever, but those clever largemouth bass always find a new way to pose a daunting challenge. Even when we utilize the latest gear and expert tips, we still have fishing trips that leave us empty-handed and dreaming about the one that got away.

More people are heading out to the water these days, but anglers report they haven’t been catching bass as often, despite healthy fish populations in lakes. A new Texas Parks and Wildlife Department study is tracking the movements and behaviors of largemouth bass at Toledo Bend Reservoir and Lake Fork to figure out what’s going on.

Have largemouth bass found new ways to outsmart us, or is there always more to learn about how they adapt to us?

“Our goal is to provide the best fishing opportunities possible for our anglers,” says TPWD fisheries biologist Jake Norman, who is co-leading the study. “Studying the actual behavior of bass and passing this information on to the anglers is a great way to do that.”

There probably hasn’t been another freshwater game fish more intensively researched over the past 40-plus years than largemouth bass, Norman says, but that doesn’t mean biologists have learned everything. They’ve found a few new ways to examine cause and effect, launching a new study in 2020.

Radio transmitters surgically implanted in the fish can track their movement to see if increased traffic and angling have influenced their behavior. The 50-fish study began in May on two lakes — 20 fish on Toledo Bend and 30 on Lake Fork. The expected life span of the transmitters is 1.5 to two years, so researchers anticipate it may take up to 2.5 years to complete the study and generate the results.

“Most studies are designed with the intent of gaining knowledge to better manage a fish population,” says Todd Driscoll, the other TPWD fisheries biologist co-leading the study with Norman. “This specific telemetry study is focused on fish behavior and how that information can directly help anglers and potentially guide them in how they approach fishing the lake.”

That distinction is not lost on avid, but sometimes frustrated, anglers. Help is on the way.


TPWD biologists use a receiver to check for tagged bass at Toledo Bend.

Where did the fish go?

Lake Fork went through its worst drought on record from 2010-15, resulting in thousands of acres of lost shallow-water habitat. The reservoir filled in 2015, leading to thousands of acres of newly flooded shallow habitat and strong year classes of fish. Anglers were optimistic; conditions were good. The term “new lake effect” was the buzz throughout much of the Fork community.

However, the high catch rates of smaller fish from 2015-18 didn’t seem to translate into more fish in the 16- to 24-inch range in 2019.

That was puzzling. Where were the fish at Lake Fork?

Complaints from bass anglers were frequent regarding declines in catch rates and lack of bass observed while idling and searching with sonar on historically productive offshore structure.

Although anglers reported a reduced number of those slot fish (bass 16 to 24 inches at Lake Fork), the electrofishing data gathered by biologists reflected the opposite. There were plenty of fish, just not where they used to be.

“This is where the project started to come together,” Norman says. “What better way to answer this question than to track fish movements over the course of a year?”

At Toledo Bend, bass fishing quality was exceptional from 2011-16, so good that the Bassmaster organization proclaimed it the best black bass fishery in the world for both 2015 and 2016. Like modern-day prospectors searching for a promising vein of gold, anglers flocked to the lake between 2016 and 2018.

By 2018, the dream was fading as anglers began reporting a decline in catch rates. Many anglers blamed a supposedly waning population. TPWD electrofishing surveys did show some decline in the bass population, but biologists wondered if there was more at play here. Did increased fishing activity on the lake alter the behavior of the fish, not just the quantity of fish? Was that adaptation contributing to the decrease in angler catch?

School of Study

The TPWD study at Toledo Bend and Lake Fork focuses on habitat use, movement and home range of largemouth bass and how those factors correlate with angling activity.

Research will also incorporate other aspects: the effects of boat motor noise and angling activity on fish behavior as well as seasonal movements of largemouth bass for one year or more on reservoirs with more than 20,000 surface acres.

After all, Toledo Bend has 181,600 surface acres. That’s a lot of room to hide.

“Are these fish avoiding areas of high angling effort, possibly suspending in deeper, open water areas?” Driscoll asks. “That much space allows for fish to potentially travel considerable distances and possibly evade angling efforts.”

Driscoll says that technological advancements — global positioning system (GPS) chart plotters with real-time, 1-foot contour mapping and side/down/forward imaging sonar units — have altered search patterns and increased how often fish are exposed to boat motor noise. Anglers utilizing these GPS/sonar units, which can display individual fish throughout the water column, now frequently idle their boats over potentially productive structure (i.e., points, steep drops, creek channels), fishing only when they see fish.

“There has been very little work done investigating how routine noises (such as a trolling motor or outboard motor idling by, the clicking sound of sonar or even the noises and actions of various lures) can potentially reposition or scatter fish,” Driscoll says. “Knowledgeable anglers will likely tell you they often see these behaviors, but very little research has been able to physically track fish and document these behaviors.”


Sonar is used to locate fish for capturing.

Every Move You Make

On both lakes, biologists will monitor the movement patterns of a particular size of largemouth bass, 16 to 24 inches long. Using that data, they can document the habitat and structure each fish is using and potentially identify broader behavioral trends throughout the year. The biologists can also monitor the immediate behavior resulting from overhead motor and sonar noise.

The bass will be monitored at least every two weeks by boat using a handheld radio receiver and antenna. Each fish has a small radio transmitter surgically implanted in its abdomen.

“Learning and practicing the surgery was a fun and nerve-wracking component of this project,” Driscoll says.

The tracking system will pinpoint the location of the fish, and researchers will create a GPS waypoint. The next step is to get eyeballs on the fish and its habitat, either directly or by using sonar. Biologists will record whether the fish is alone or part of a group and if it’s suspended in the water column or more bottom-oriented.

Is there structure attracting the fish? How is the fish reacting to the boat noise or direct fishing pressure? As the answers build a body of data, patterns and trends will emerge.


Biologists deploy an antenna to find tagged fish at Toledo Bend.


Besides electroshock, traditional angling is sometimes employed to collect fish.

Oops, I Caught One!

Norman and Driscoll put their cellphone numbers on the pink tags near the dorsal fin of the bass. Call them if you catch a tagged fish. They ask that you take a few photos, record the tag number and release the fish where you caught it, if possible.

Of course, that’s entirely optional if the fish is legal to harvest, but biologists urge you to consider releasing. They’d like to get the transmitter back, at least.

Why’s This a Big Deal?

“The results and future outcomes are more focused on informing our anglers than addressing management concerns or actions,” Norman says. “All you hear in the natural resource community is that we’ve researched everything that can be done with largemouth bass; we know it all. In some sense, everyone’s correct. Traditional studies have made managing bass almost like following a recipe in a cookbook.”

Norman says that he feels this study, funded by the Sport Fish Restoration Program, proves that TPWD never stops digging deeper, even with a species as heavily studied as largemouth. 

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