State of the Nation’s River
RIVER HEALTH INDICATOR
FISH
Fish are good indicator species for the overall health of the Potomac River. Healthy fisheries require cool water temperatures, oxygen-rich waters, and healthy habitats such as underwater grasses. Abundance and variety of fish species in a river can be signs of good water quality and also support recreation opportunities and subsistence fishing needs.
Conservation and habitat restoration efforts continue reversing decades of declining fish populations in the Potomac, which now supports healthy communities of American shad, striped bass (rockfish), white perch, and smallmouth bass. In fact, the Potomac is one of the few places along the East Coast where shad populations are exceeding restoration goals.
The Potomac’s fisheries are generally recovering, but, a very wet spring (like the Potomac experienced in 2016) can reduce juvenile numbers and impact future populations.
Pollution from excess nutrients and sediment can alter and destroy 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 toxins, like PCBs, also threaten fisheries in the Potomac. Local fish populations face similar threats from localized polluted runoff, particularly in urban areas of the Potomac region.
Invasive and non-native fish species present additional threats to the river’s ecosystem. Blue and flathead catfish and northern snakehead populations are growing rapidly in some areas, yet stabilizing in other locations. The long-term ecosystem impacts are not well understood yet, but experts continue to be concerned by the presence of these invasive species, which can harm native and naturalized fish populations through competition and predation. Invasive species are nearly impossible to eradicate once they begin expanding throughout an ecosystem.
Healthy fish populations support recreational and commercial fishing industries, too; however, increased levels of toxic contaminants such as PCBs make many fish unsafe for human consumption in and around Washington, DC. The DC Department of Energy and Environment issues consumption advisories for most fish caught in DC and recommends against eating American eel, carp, and striped bass.
Long-term trends for the fish indicator continue to show improvement while short-term trends are variable by species.
American Shad
Previous Grade: A
American shad was once the largest commercial and recreational fishery along the Atlantic Coast, but a dangerous combination of dam construction, pollution, habitat degradation, and overfishing threatened the entire shad population.
A strict commercial harvest ban, initiated in the 1980s in both Maryland and Virginia began a long-term recovery effort. Shad are once again thriving in the Potomac and, since 2011, their populations continue surpassing restoration goals. Anglers are allowed to catch and release, though commercial harvesting remains prohibited. In 2016, Mayor Muriel Bowser named the American shad the official fish of DC.
The shad recovery effort in the Potomac continues to show consistent positive trends, but other nearby rivers are not seeing the same success. The James, York, and Susquehanna rivers continue to post negligible recovery numbers. In fact, juvenile shad stocking in other Chesapeake Bay tributary rivers appears to have reached an all-time low in 2016, and officials are suspending restocking efforts in the James River.
The exact causes of shad’s return to the Potomac 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. A fish ladder constructed in 2000 at Little Falls re-opened several miles of river to shad spawning and is considered key to shad recovery in the Potomac.
Abundance of shad, as measured by catch per unit effort (CPUE), increased more than 12 percent since the last Potomac River report card.* In the five-year period from 2012 to 2016, the CPUE for shad averaged 40.2, exceeding the 31.1 goal for the Potomac River as reported by the Chesapeake Bay Program. With these numbers, American shad are meeting 129 percent (A) of the established goal.
The Potomac received an “A” for shad in the previous Potomac River report card.
Learn more about American shad
*In order to maximize available data, five years of data working back from 2016 are averaged together to provide the 2018 score. Including these data points results in overlapping data for the years 2012, 2013, and 2014, but reduces yearly statistical noise associated with individual annual recordings.
Striped Bass
Previous Grade: B
As a popular recreational sportfish and the official state fish of Maryland, striped bass (also known as rockfish) support a multi-million dollar fishing industry in the Potomac and the Chesapeake Bay. Overfishing caused a sharp decline in striped bass population in the 1980s and 90s, but a five-year moratorium brought the population back to sustainable numbers.
Despite a drop in Potomac juvenile striped bass in 2016, strong juvenile populations in 2009, 2011, 2013, and 2015 continue to maintain a healthy adult population. State and federal fishery regulators have not reported overfishing of striped bass in the Potomac, and the Maryland DNR is reporting one of the healthiest adult populations observed in the Potomac in recent years. The long-term population trend (since 1957) continues to increase for striped bass, despite recent short-term declines.
Striped bass in waters around Washington, DC contain dangerous levels of PCBs and should not be consumed.
Abundance of striped bass, as measured by catch per haul, decreased 6 percent since the last Potomac River report card.* In the five-year period from 2012 to 2016, the catch per haul for juvenile striped bass averaged 2.7, falling short of the 30-year historic mean of 4.2. With these numbers, striped bass are meeting 65 percent (B-) of the established goal.
The Potomac received a “B” for striped bass in the previous Potomac River report card.
*In order to maximize available data, five years of data working back from 2016 are averaged together to provide the 2018 score. Including these data points results in overlapping data for the years 2012, 2013, and 2014, but reduces yearly statistical noise associated with individual annual recordings.
White Perch
Previous Grade: A
Another abundant and popular recreational fishing species, white perch continues to thrive in the Potomac.
A close relative of the striped bass, white perch are found along most of the Atlantic coast and tend to remain in local waters throughout their lifespans; this makes them strong indicators of an area’s toxic contaminant level.
Despite a drop in juvenile white perch in 2016, the larger trend of juvenile white perch abundance continues to increase in the Potomac; this trend may give a boost to adult populations in future years. According to the Maryland DNR, white perch are reproducing at sustainable levels and are not currently overfished; these variations in juvenile populations are normal.
Abundance of white perch, as measured by catch per haul, increased less than one percent (0.13) since the last Potomac River report card.* In the five-year period from 2012 to 2016, the catch per haul for juvenile white perch averaged 7.54, exceeding the 30-year historic mean of 6.41. With these numbers, white perch are meeting 118 percent (A) of the established goal.
The Potomac received an “A” for white perch in the previous Potomac River report card.
*In order to maximize available data, five years of data working back from 2016 are averaged together to provide the 2018 score. Including these data points results in overlapping data for the years 2012, 2013, and 2014, but reduces yearly statistical noise associated with individual annual recordings.
Smallmouth Bass
Previous Grade: B-
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. Smallmouth bass contribute millions of dollars annually to local economies across the watershed. Good water quality is required to support reproduction and recruitment of smallmouth bass.
An unusually wet month of May in 2016 is thought to be a primary driver of the observed sharp decline in juvenile smallmouth bass. Juvenile smallmouth bass measured 25 percent of the historic mean in 2016, which could result in decreased adult populations during future years. However, the adult population observed in 2016 was one of the healthiest in many years.
Smallmouth bass continue to face threats from nutrient pollution, disease, climate change, and endocrine disrupting chemicals, which can produce intersex fish, who share both male and female cells.
Abundance of smallmouth bass, as measured by catch per haul, decreased by 11 percent since the last Potomac River report card.* In the five-year period from 2012 to 2016, the catch per haul for juvenile smallmouth bass averaged 1.2, falling short of the 30-year historic mean of 2.3. With these numbers, smallmouth bass are meeting 50 percent (C) of the established goal.
The Potomac received a “B-” for smallmouth bass in the previous Potomac River report card.
Learn more about smallmouth bass
*In order to maximize available data, five years of data working back from 2016 are averaged together to provide the 2018 score. Including these data points results in overlapping data for the years 2012, 2013, and 2014, but reduces yearly statistical noise associated with individual annual recordings.
Blue and Flathead Catfish
(Invasive Threat)
Previous Grade: N/A
Non-native blue and flathead catfish were first introduced to tributaries of the Chesapeake Bay in the 1960s and 1970s and have become popular with recreational fishers. Unfortunately, the growing presence of catfish in local waters likely spells trouble for other fish species and ecosystems.
Blue catfish can live up to 30 years and grow in excess of 100 pounds, and are opportunistic eaters that devour mussels, vegetation, and other fish. Their rapid expansion has raised concern about their impact on native species and prompted the EPA’s Chesapeake Bay Program to adopt a much-needed management strategy. Commercial harvesting is considered a key management strategy for blue catfish in the Chesapeake Bay and tidal Potomac River.
From 2014 to 2015, commercial landings of blue catfish weight in Maryland’s waters more than doubled (108 percent increase). An increase in consumer demand likely contributed to some of the growth in numbers. Maryland DNR continues to conduct monitoring efforts, including a new tagging study to determine growth rate, population size, and angler harvest.
Flathead catfish were first caught in the Potomac in 2012. These fish are also expanding their geography throughout the region, including in the Potomac. Similar to blue catfish, flatheads are top predators, reproducing and developing quickly. Maryland DNR is studying impacts from flathead catfish on Potomac ecosystems. From 2014 to 2015, flathead catfish weight trapped in sampling surveys almost tripled (273 percent increase).
Learn more about flathead catfish
It is illegal throughout the Potomac region to transport live blue or flathead catfish for the purpose of introduction into another body of water. The State of Maryland currently classifies blue and flathead catfish as high priority species in their 2016 Maryland Aquatic Nuisance Species Management Plan, meaning there is a high probability of negative economic or ecological impact.
There is no reduction target established for the Potomac River blue or flathead catfish populations.
The Potomac received no grade for blue or flathead catfish in the previous Potomac River report card.
Northern Snakehead
(Invasive Threat)
Previous Grade: N/A
Native to Asia, northern snakeheads were first discovered in the Potomac basin in 2002 and were initially confined to the tidal portion of the river. Since 2002, the population of snakeheads has increased, expanding to multiple tributaries in Maryland and Virginia, including upstream of Great Falls.
An incredibly resilient species, snakeheads can survive in extreme temperature and precipitation conditions. They can breathe air, tolerate low-oxygen waters, and survive in mud or puddles.
The relative abundance of snakeheads is declining in some others, but not others, according to the Maryland DNR. In Virginia, snakehead populations in sampled creeks are beginning to stabilize, or even slow, according to the Virginia Department of Game and Inland Fisheries (DGIF).
It is illegal to transport snakeheads across state lines without a federal permit. Maryland DNR and Virginia DGIF strongly advise fishers to kill snakeheads, if caught, and remove them from the river. Eradication measures have demonstrated mixed results. Tributaries with good public access and awareness by anglers have seen a decline in overall abundance. The opposite is true in tributaries with poor public access or where fishing for snakeheads is less popular.
Scientists with Maryland DNR and Virginia DGIF report variable population trends suggesting the invasive threat continues to exist and should be closely monitored. The State of Maryland currently classifies northern snakehead as a high priority species in their 2016 Maryland Aquatic Nuisance Species Management Plan, meaning there is a high probability of negative economic or ecological impact.
There is no reduction target established for the Potomac River snakehead population.
The Potomac received no grade for northern snakehead in the previous Potomac River report card.
Learn more about northern snakehead
Resources and Methodology
The Potomac is home to a diverse range of fish species. To assess overall fish health, we include historical data on common game fish including American shad, striped bass (rockfish), white perch, and smallmouth bass. At this time, the report does not feature trends for other common fish like largemouth bass, trout, sunfish, or crappies. Brook trout may serve as a future indicator species, as they are sensitive to water temperatures and habitat conditions in upstream portions of the Potomac watershed.
Experts use annual juvenile fish surveys to predict the health of adult population sizes in future years. Juvenile fish populations are naturally variable from year to year as weather and other environmental conditions can impact spawning and mortality rates. Studying long-term trends provides important insights into the overall health of a fish species.
American shad data is reported as average catch per unit effort, and is graded against an established Potomac River population target set by the Chesapeake Bay Program. Restoration goals do not currently exist for the other species in this report; in these cases, Potomac Conservancy formed a restoration target based on the average catch per haul over a 30-year period of time (beginning in 1985 or 1987, depending on the fish species). There are no established reduction goals for invasive species.
Data for the Fish indicator are provided by the EPA Chesapeake Bay Program, the Potomac River Fisheries Commission, the MD DNR, and the VDGIF.
Government agencies work to maintain healthy fish populations both through regulations aimed at improving the health of the river and commercial and recreational fishing rules. For instance, fishers are encouraged to catch and kill certain invasive species, while other regulations prohibit catching at-risk species. The long-term impacts of these regulations vary by species and location.
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