After decades of decline, the Potomac is now healthy enough to support growing populations of common game fish including shad and white perch.
Some fish species continue to struggle, but long-term trends signal that we’re beginning to reap the benefits of pollution-reduction and restoration efforts.
Fish are good indicator species for the overall health of the river because they are impacted by a host of environmental factors. An abundance and variety of fish species in a river is often a sign of good water quality. Fish and other aquatic animals depend on oxygen-rich waters that support healthy habitats and food sources.
Pollution from excessive nutrients and sediment can alter and destroy aquatic habitat, decrease dissolved oxygen, and reduce the abundance of macroinvertebrates, an important food source for fish. Disease, spring flooding, warming waters, endocrine disrupting chemicals, and PCBs also threaten the Potomac’s fisheries.
Populations of non-native northern snakehead fish and blue catfish are rapidly growing and expanding into new areas of the Potomac. Their impact on the river’s ecosystem is not fully known at this time, but there is concern they could harm other fish populations through competition and predation.
Rebounding fish populations are great for recreational fishing, but contaminants in the Potomac’s waters make many fish unsafe for human consumption. Washington, DC recently advised against eating locally-caught striped bass, one of the most popular catches for local anglers and Maryland’s state fish.
The Potomac is home to a diverse range of fish species. To assess overall fish health, we included historical data on common game fish including shad, striped bass (rockfish), white perch, and smallmouth bass. At this time, the report does not feature long-term trends for other common fish like largemouth bass, trout, sunfish, or crappies.
Experts use annual juvenile fish surveys to assess the number of young fish populations and predict the health of adult population sizes in the out years. Young fish populations are naturally variable from year to year as weather and other environmental conditions can impact fish spawning and mortality rates. Long-term trends can provide important insights into the overall health of a fish species.
Shad data is graded against an established Potomac River population target as reported by the Chesapeake Bay Program. Restoration goals do not currently exist for the other species in the report; in these cases, Potomac Conservancy formed a restoration target based on the average catch per hauls over a 30-year period of time (1985 onward). Fish data has been provided by the EPA’s Chesapeake Bay Program, Maryland Department of Natural Resources, and Virginia Department of Game and Inland Fisheries.
Government agencies in the area work to maintain healthy fish populations both through regulations aimed at improving the health of the river and rules involving fishing. For instance, fishermen are encouraged to catch and kill certain invasive species, while other regulations prohibit catching at-risk species.
Previous Grade: A
American shad are a well-known herring in the Chesapeake Bay region. Pollution, dams, and overfishing threatened their population in our region.
Shad are now thriving in the Potomac and their populations have surpassed restoration goals. Fishermen have reported the river “running silver with shad” near Fletcher’s Cove after years when populations were severely diminished. Anglers are allowed to catch and release, though harvesting has been banned since 1980.
Shad’s comeback in the Potomac is uniquely successful as the Susquehanna, James, and other Bay rivers have seen minimal gains.
While the exact causes of shad’s return to the river aren’t entirely clear, a cleaner river, harvest moratoriums, stocking programs, new fishways, and the restoration of tidal grasses seem to have played a part, according to the Interstate Commission on the Potomac River Basin.
In the five-year period from 2010 to 2014, the catch per unit effort (CPUE) for shad averaged 35.7, or 14.8 percent above the 31.1 CPUE target population goal for the Potomac River as reported by the Chesapeake Bay Program. The last river report in 2013 graded shad at an A.
Previous Grade: B-
Striped bass (rockfish) is Maryland’s state fish and the top recreational sportfish in the Chesapeake Bay. This popular catch supports a multi-million dollar recreational and commercial fishing industry.
The abundance of young striped bass in the Potomac has increased significantly over the decades, though we have seen a decline in their numbers over the last ten years; this trend may result in lower adult populations in the out-years. According to the Maryland Department of Natural Resources, striped bass are reproducing at sustainable levels and are not currently overfished, and variations in juvenile populations are normal. Striped bass in waters around Washington, DC have dangerous levels of PCBs and should not be consumed.
In the five-year period from 2010 to 2014, the catch per haul for juvenile striped bass averaged 2.9, or 69 percent of the 30-year average of 4.2. The last river report in 2013 graded striped bass at a B-.
Previous Grade: C
White perch, a close relative of the striped bass, is one of the most abundant and popular recreational fish in the Potomac and Chesapeake Bay. While they are found along most of the Atlantic coast, they tend to remain in local waters throughout their lifespans, which makes them strong indicators of an area’s toxic contaminant level.
The abundance of juvenile white perch has increased significantly over the decades, and we have seen particularly healthy numbers over the last five years; this trend may give a boost to adult populations in the out-years. According to the Maryland Department of Natural Resources, white perch are reproducing at sustainable levels and are not currently overfished, and variations in juvenile populations are normal.
In the five-year period from 2010 to 2014, the catch per haul for juvenile white perch averaged 7.53, or 17.5 percent above the 30-year average of 6.41. The last river report in 2013 graded white perch at a C.
Previous Grade: N/A
Smallmouth bass is one of the most iconic and popular sport fish in the non-tidal waters of the upper Potomac. Originally introduced into the area in the mid-1800s, smallmouth bass are well-established in the Potomac and popular among anglers.
A Maryland Department of Natural Resources (DNR) annual study indicates young smallmouth bass in the middle Potomac are at their highest levels since 2007. As John Mullican from DNR explains, “That means in the coming years, fishermen may see a greater number of smallmouth bass.”
In 2015, stable water flows in May and June provided the ideal conditions for spawning. Young fish mortality rates can spike in the spring, as high flow and turbidity can limit good spawning areas, cause some adults to abandon their nests, and increase fry mortality.
Though last year’s strong year class is welcome news, smallmouth bass continue to face threats from nutrient pollution, disease, climate change, and endocrine disrupting chemicals, which cause egg cells in male fish.
The abundance of young smallmouth bass in the middle Potomac River (Dam 5 downstream to Dam 3) remains highly variable from year to year. In the five-year period from 2011 to 2015, the catch per haul for juvenile smallmouth bass at this location averaged approximately 1.44, or 63.7 percent of the 28-year mean.
Previous Grade: N/A
Since they were first spotted in the Potomac’s tidal waters over a decade ago, northern snakehead fish populations in the river have reached 20,000 — rivaling that of largemouth bass, confirmed Joseph W. Love, Tidal Bass Manager at Maryland Department of Natural Resources.
Dubbed “frankenfish” by some, northern snakeheads are predatory freshwater fish native to China. An incredibly resilient species, snakeheads can survive in extreme, dry conditions that may become more prevalent with climate change. They can breathe air, tolerate low-oxygen waters, and survive in mud or puddles.
Snakeheads have rapidly expanded in Maryland’s tidal waters and the main stem of the Potomac River, and have been recently confirmed upstream of Great Falls, a natural fish barrier. Preferring shallow waters, snakeheads are thought to have entered the upper Potomac by way of the C&O Canal where they have been regularly sighted. John Mullican and fellow experts at the Maryland Department of Natural Resources are watching their presence in non-tidal waters closely as they have the potential to outcompete and prey on largemouth bass, smallmouth bass, and sunfish.
Snakehead populations are generally larger in Virginia tributaries, where they were first established. According the Virginia Department of Game and Inland Fisheries, populations of snakehead in the commonwealth’s tidal creeks are leveling out and may be in slight decline. Their ecological impact in these tidal tributaries is not yet clear.
State and federal agencies continue to study the degree to which these predatory fish are or are not having an ecological impact on local fisheries. Once established in a waterway, it is unlikely they can be eradicated. Virginia and Maryland encourage anglers to catch and kill northern snakehead fish.
Previous Grade: N/A
The largest species of catfish in North America, the blue catfish is a non-native predator that appears to be growing quickly in size and population in the tidal Potomac. Experts from Virginia and Maryland agree their growing presence in local waters spells likely trouble for other fish species. Blue catfish can live up to 30 years, grow in excess of 100 pounds, and are opportunistic eaters that devour mussels, vegetation, and other fishes.
According to Mary Groves at the Maryland Department of Natural Resources (DNR), the Potomac and Maryland tributaries are “flooded with little blue catfish right now.” Populations can explode due to overcrowding of small fish. From 2013 to 2014, commercial landings of blue catfish in Maryland’s waters increased by 61.7 percent; greater demand contributed to some of the growth in numbers, but DNR confirms it is a good indication of their growth and expansion.
Blue catfish make for great table fare and can be commercially and recreationally fished in Virginia and Maryland. Anglers are encouraged to kill small, edible blue catfish (1-5 lbs) to help with mitigation efforts while maintaining a sufficient stock of large, trophy-size blue catfish.
State and federal agencies continue to study the ecological impact these predatory fish may have on local fisheries. Once established in a waterway, it is unlikely they can be eradicated.