Got Grass? How Grass Growth Is Influencing The Upper Potomac Smallmouth Population
Most anglers are familiar with the flood that crested some three and half feet above flood stage in many sections of the Upper Potomac River in 2018. The impact of this flood has been seen for years especially on the quality of the smallmouth bass density in the river system but the biggest issue impacting the quality has ultimately been grass development.
The 2018 flood directly impacted the grass in the river for years and in some sections grass has still not returned some five years later yet there are sections that this year have produced big swaths of grass beds. Many of these areas are downriver and some believe that this has happened because of the grass that was displaced and moved down river during high level events that have finally begun to develop even in areas that previously where not known for alot of grass.
The Pennyfield Section below Old Dam #2 (Seneca Landing/Riley’s Lock/Violette’s Lock) is one such section that has experienced massive amounts of grass development especially on the Virginia side of the river and between the island sets.
We know based on this season in many sections of the Upper Potomac we have seen increase in smallmouth bass density based on the number catches but also catch rates coupled with citation smallmouth being reported again from the river. This dynamic is happening in the sections now that have seen tremendous grass growth over the last two years.
The Eastern United States is home to a variety of grass types that can be found in our river systems, and these grasses can significantly influence the habitat of black bass, especially smallmouth bass. The types of grasses can vary depending on the specific region and environmental conditions, but here are some of the most common grasses that you may find in many Eastern U.S. river systems and their influence on black bass habitat:
Emergent Grasses:
Bulrushes (Schoenoplectus spp.): These tall, stiff, and dense emergent grasses often grow in shallow water near the shoreline. They provide shelter and ambush points for black bass, especially largemouth bass. Bass use bulrushes for cover when hunting prey or avoiding predators.
Cattails (Typha spp.): Cattails are another common emergent grass found along the edges of rivers and ponds. They offer protection to young bass and attract prey species like insects and small fish and bait fish.
Submerged Aquatic Vegetation (SAV):
Hydrilla (Hydrilla verticillata): Hydrilla is a submerged aquatic plant that can form dense underwater mats. These mats provide cover for juvenile bass and attract bait fish, making it a prime spot for bass to hunt. First recognized in the Potomac River in 1982 and within ten years covered some 3,000 acres. Often confused with common Waterweed in some areas as they have similar appearance only waterweed has whorls of three.
Eelgrass (Vallisneria spp.): Eelgrass is a type of SAV that provides habitat for invertebrates and small fish, which in turn attract bass. It can be found in slower-moving sections of rivers. Stargrass is also one growing in some areas of the Potomac watershed.
Floating Aquatic Plants:
Water lilies (Nymphaea spp.): Floating aquatic plants like water lilies provide shade and cover for bass. They also attract insects, which are a food source for bass.
Algae and Moss:
Algae and mosses: While not true grasses, various types of algae and mosses can grow in river systems and provide a substrate for insects and other aquatic organisms. These, in turn, attract black bass as they seek prey.
Grassy Shorelines:
Grass-lined shorelines: In some river systems, grassy vegetation can grow along the shoreline, providing an ideal spawning habitat for black bass. largemouth bass, in particular, may build nests in these areas where smallmouth tend to prefer rock or shell bottoms for spawn.
Turbidity and Water Clarity:
The presence of grasses and vegetation can influence water clarity and turbidity in river systems. Black bass, especially smallmouth bass, may prefer clearer water, while largemouth bass can adapt to a wider range of water conditions.
https://dnr.maryland.gov/waters/bay/Documents/SAV/complete_sav_key.pdf
https://cast-content.chesapeakebay.net/documents/SAV_FactSheets/UpperPotomacRiverMD(MATTF,PISTF,ANATF-MD,POTTF-MD)_TT_11.14.19.pdf
It's important to note that the specific types of grasses and their impact on smallmouth habitat can vary from one river system to another within the Eastern United States. Smallies are highly adaptable and will utilize the available vegetation and structure for cover, ambush points, and as a source of food. Conservation efforts often focus on maintaining or restoring healthy aquatic vegetation to support the bass population and the overall health of river ecosystems.
This summer’s low water levels and weather that has seen weeks on end above 90 degrees may take a toll on the grass of the river as the sun ultimately will turn green grass atop the water line brown sooner than later from August into September unless the grass becomes submerged again. The “browning” effect of the grass will force smallies to locate other areas of green grass or rock adjacent to river seams or current flows as smallies will seek out more oxygen as they transition to feeding up in the Fall for the colder months ahead.
The cycle for the smallmouth bass and grass in the river is as follows:
Smallmouth bass (Micropterus dolomieu) exhibit various behaviors and preferences regarding different grass types and submerged vegetation in river systems throughout the year, as their habits are influenced by seasonal changes and the availability of prey. Here's how their relationship with these aquatic plants can differ across the seasons:
Spring:
Pre-Spawn: In early spring, before the spawn, smallmouth bass are often found in deeper water near the edges of submerged vegetation and structure. They are preparing for the spawning season and may use these areas for staging and feeding.
Spawn: During the spawn, smallmouth bass may seek out rocky substrates and gravelly riverbeds, typically away from dense vegetation. They prefer cleaner areas to create their nests, which are often located near rock formations.
Summer:
Post-Spawn: After the spawn, smallmouth bass tend to become more aggressive predators and may move away from dense submerged vegetation. They often inhabit rocky areas, drop-offs, and structure, where they can ambush prey more effectively.
Aquatic Vegetation: Smallmouth bass are less likely to be found within dense submerged vegetation during the summer. They prefer open water or areas with rocky bottoms and clear water conditions. They feed primarily on small fish, crayfish, and aquatic insects.
Fall:
Transition Period: In the fall, as water temperatures start to drop, smallmouth bass may become more active near submerged vegetation again. They use these areas to hunt for prey, such as baitfish and crayfish, which become more active in the cooler water.
Feeding Frenzy: As the bass prepare for the winter months, they may use the edges of aquatic vegetation as hunting grounds. The dying vegetation can attract prey, making it a prime location for smallmouth bass to feed.
Winter:
Inactive Period: In the colder winter months, smallmouth bass become less active and tend to seek deeper, slower-moving pools and areas with stable water temperatures. They are less likely to be associated with submerged vegetation during this time.
Overall, smallmouth bass in river systems often may show a preference for rocky structures, clear water, and open areas, especially during the summer. While they may utilize submerged vegetation during certain times of the year, their behavior is primarily dictated by water temperature, prey availability, and the seasonal life cycle, rather than a strong association with specific grass types or dense aquatic vegetation like largemouth bass often do. Much of this is influenced by a lack of grass historically in many rivers but with grass coming back we are seeing some behaviors change with regard to smallies especially in the Potomac River.
Understanding these seasonal patterns is crucial for successful smallmouth bass fishing and conservation efforts in river systems.
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