Scientists with the Maryland Department of Natural Resources released two studies in recent months that examine habitat needs for largemouth bass and movement patterns of invasive blue catfish, providing data to guide management of popular sportfishing and ecosystem threats in the Chesapeake Bay watershed. The research, published in peer-reviewed journals, underscores the role of submerged aquatic vegetation in sustaining bass populations and highlights the feasibility of targeted removals for catfish in rivers like the Patuxent, which flows through Southern Maryland counties.
Led by DNR fisheries biologist Dr. Joseph W. Love, the first study appeared in Ecological Modelling in May 2024 and analyzed more than 20 years of monitoring data from the upper Chesapeake Bay watershed. Researchers used geographic information system mapping to compare bass population trends with habitat variables, including levels of submerged aquatic vegetation, or SAV, which serves as cover for young fish and feeding grounds for adults. Model simulations indicated that bass numbers held steady during high-SAV periods, even with elevated catch-and-release mortality from angling, due to ample space for spawning and growth. In contrast, low SAV correlated with fluctuating or declining catches, which only stabilized when both habitat improved and angling-related deaths dropped.
The second study, published in Estuaries and Coasts in May 2025, involved Dr. Love and coauthors Branson D. Williams, Tim Groves, Ross Williams and Mary Groves. It tracked 30 blue catfish in the Patuxent River using dual acoustic and radio tags from winter 2022 through spring 2023. The fish congregated in upstream freshwater sections during colder months but showed increased mobility in spring, with about two-thirds traveling less than one-tenth of a mile daily. Downstream shifts into brackish areas occurred mainly in June but were rare overall, suggesting limited long-distance migration that could aid localized control efforts.
“DNR’s fisheries management strategies are rooted in science,” said Tony Prochaska, associate director of DNR Fishing and Boating Services. “These two publications provide data that inform how we can manage two very different species, one we work to conserve and another we are trying to control.”
For largemouth bass, Maryland’s top recreational target, the findings reinforce habitat protection as a core tactic. Anglers in Southern Maryland, where tidal rivers like the Patuxent and Potomac host thriving bass fisheries, contribute to an estimated 1.2 million bass caught annually statewide, according to DNR electrofishing surveys. This year, DNR collaborates with the Black Bass Advisory Committee on a tournament survey to track angling pressures and reduce mortality factors, such as overcrowding at weigh-ins or delayed releases. Committee meetings, held quarterly, including sessions on April 7, July 7 and October 6, 2025, incorporate angler input to refine practices. DNR also conducts annual SAV aerial surveys, documenting a 1 percent decline to 91,684 acres baywide in 2024, short of the 114,000-acre restoration goal set under the Chesapeake Bay Program. In Maryland waters, freshwater river gains offset mid-Bay losses, with monitoring focused on stressors like nutrient runoff from agriculture in Charles and St. Mary’s counties. Environmental reviews for in-stream projects, such as stream restorations near La Plata or bridge repairs over the Patuxent, ensure minimal SAV disruption, while permits promote techniques like slot limits to shield spawning adults.
Blue catfish, introduced to Virginia waters in the 1970s and now dominant in all major Maryland tidal rivers, consume native species like menhaden and juvenile blue crabs, altering food webs in the Patuxent estuary. The Patuxent study supports river-specific interventions, as tagged fish rarely ventured beyond 20 miles, reducing repopulation risks from neighboring systems. DNR launched a 2025 pilot program in February to partner with commercial harvesters, authorizing charter captains to sell catches and expanding electrofishing operations to assess and remove biomass from the Patuxent, Potomac and Nanticoke rivers. Participants use low-voltage pulses from boats to stun and collect fish, targeting adults over 30 inches to disrupt reproduction. Collaborations with Salisbury University examine removal impacts on population age structures, while U.S. Geological Survey models predict that culling large females could cut biomass by 20 percent over five years in targeted segments. Public involvement remains key: No creel limit applies to blue catfish over 22 inches in tidal waters, encouraging harvest for markets or personal use, with Southern Maryland seafood outlets like those in Solomons stocking the mild-flavored fillets.
These efforts align with broader Chesapeake Bay restoration under the 2014 agreement, where Maryland coordinates with Virginia and federal partners to balance conservation and control. Largemouth bass, native to the region since colonial stocking, support a $100 million annual economic impact from recreational fishing, drawing 300,000 license holders. Blue catfish, however, have swelled to densities rivaling Virginia’s James River, where commercial landings topped 4 million pounds in 2024, prompting Maryland’s push for baywide coordination to curb spread into tributaries like the Little Patuxent.
DNR’s approach integrates monitoring with adaptive policies, such as the Maryland Fishing and Crabbing Guide’s emphasis on barbless hooks for bass and incentives for catfish reporting via the iNaturalist app.
