One of the earliest non-native fish species to be widely released into North American waterways was the Common Carp. Stocks brought to the United States were likely sourced from populations already naturalized throughout much of western Europe after introductions originating from the fish’s native range in Eurasia, probably including the Danube and other watersheds east through the Volga. In western Europe, the species promised to be an abundant and easily cultivated food source. Under the same premise, carp were transported to the United States during the early 1800s and widely introduced into streams, lakes, and rivers throughout the country.
Common Carp thrive in nutrient-rich waters, particularly those subjected to sewage discharge and agricultural runoff, conditions which were already prevalent during the Common Carp’s initial introduction and have remained widespread ever since. Within these polluted streams, lakes, and ponds, introduced carp feed aggressively on benthic organisms and plants, stirring up decaying organic matter (mulm) from the substrate. This process raises turbidity in the water column and releases excessive amounts of the nutrient phosphorus resulting in unusually large algal blooms. Algal blooms can block sunlight from the longer-lived oxygen-producing vascular plants that grow in submerged environs. Growing beneath a dense cloud or blanket of algae can compromise the vigor of oxygen-producing vascular plants and disable their biochemical functions within the aquatic ecosystem. As the short-lived algae die, the bacteria that decay them begin to place increased oxygen demands on the water. With less oxygen being produced by both the vascular plants and the algae, and with oxygen consumption increased by the activity of decomposers, conditions can become fatal for fish and other organisms. This process is known as eutrophication. Because Common Carp are among the species most tolerant of eutrophic conditions, they tend to thrive in the conditions they create while the native fishes perish.
Common Carp spawn in the spring, usually from late April through June, when the water temperature is as low as 58 degrees and as high as 83 degrees Fahrenheit. This activity is often triggered by a rapid increase in water temperature. In a small lake, this may be brought on by a string of sunny days in late April or May. On larger streams and rivers, the temperature spike that initiates the spawn may not occur until warm rains and runoff enter the stream during June.
Seeing the exposed backs of Common Carp as they stir up mulm and other sediments while feeding along the edges of a body of water is not at all unusual.But carp pursuing other carp into the shallows is a sign that spawning has commenced.In water that is often less than a foot in depth, male carp follow the breeding females into egg-laying areas among debris and emergent vegetation.A fountain of splashes can ensue as males try to outdo one another for a chance to fertilize the female’s eggs.The males’ aggressive pursuit can even forced a large female to temporarily ground herself on the beach.
Common Carp are one of the most widely farmed and eaten fish in all the world. Here in the United States, they were introduced beginning two hundred years ago because they were favorable to the palate, grew to large size quickly, and were a source of much needed food. Today, the Common Carp is seldom found on the American dinner plate. Yet, pound for pound, it is one of the most abundant fish in many of our waters, particularly in man-made lakes. Like some of our other most invasive species—including Blue Catfish, Flathead Catfish, and Northern Snakehead—Common Carp are perhaps the most edible of our freshwater fishes. For many cultures, they are an important staple. For others, they are a delicacy or holiday treat. In America, they do horrendous damage to aquatic ecosystems following establishment as a food crop that almost never gets harvested. Did you realize that on the internet, there are literally hundreds of recipes and culinary videos available to show you how to prepare delicious dishes made with Common Carp? It’s true. And for the cost of a fishing license, you can catch all you want, usually several pounds at a time. So why not give the marine fisheries a break? Take the big leap and learn to eat invasive freshwater species instead.
As the Flowering Dogwoods remind us, it’s time for adult sea-run shad and other fishes to ascend the Susquehanna to spawn. So yep, we’re off to Fisherman’s Park on the river’s west shoreline below Conowingo Dam in Harford County, Maryland, to check it out.
Anglers were in the water and seeing action as we arrived below Conowingo Dam’s powerhouse at Fisherman’s Park. The east lift, which was constructed during the 1990s to raise American Shad and other migratory fish over the dam during their spring spawning runs, sits idle at the impoundment end of the wing wall in the distance.The entrance to the idle east fish lift at Conowingo Dam.Within minutes, we watched one of the culprits responsible for the lift’s shutdown being reeled in. The invasive population of introduced Northern Snakeheads continues to thrive in the waters of the Susquehanna and its tributaries below the dam. To prevent it from expanding its range to upriver sections of the watershed, all American Shad are being manually separated from among the snakeheads and other fish species deposited into sorting tanks using the west lift near the powerhouse.One of several specialized transport vehicles returns from a “shad run” to the waters of the Susquehanna above York Haven Dam at Conewago Falls after delivering and releasing American Shad sorted from among the fish collected at Conowingo’s west lift earlier in the day.American Shad began their run up the Susquehanna as water temperatures reached 60 degrees Fahrenheit…just about the time the Flowering Dogwoods started to bloom within the river’s riparian woodlands. Later this month, spawning activity peaks when the water warms to about 65 degrees. Earlier in the season, when the water reached about 55 degrees, another anadromous species, the Hickory Shad (seen here), began their spring spawning run from sea to freshwater rivers and streams.While American Shad are seldom caught on hook and line, Hickory Shad are a popular catch-and-release target. Though they will energetically strike baits like the small shad dart seen here, Hickory Shad are very cautious while ascending the river; they very rarely enter the fish lifts to join the dozens of other species that readily accept their use. With water temperatures now in the sixties, an angler is seen here bringing in what may be among the last of this season’s Hickory Shad. Their spawning run is presently drawing to a close for the year.The most commonly caught herring at Fisherman’s Park is the Gizzard Shad. This plankton feeder seldom takes bait; it is instead foul-hooked. Though not a sea-run species, Gizzard Shad by the tens of thousands leave open waters to seek shallower flowing riffles and pools to spawn.Unlike the other herring occurring in the Susquehanna, the Gizzard Shad has a blunt, snub-nosed appearance to the snout. The mouth is small and often unnoticeable.The Gizzard Shad is the only species of Susquehanna herring that can legally be harvested. All others are sea-run migrants in varying degrees of population peril and must be returned to the water without delay.Note the elongated last ray on the dorsal fin of this foul-hooked Gizzard Shad. It’s a not-often-visible but nevertheless tell-tale field mark.Humans aren’t the only creatures attracted by the fish migration on the lower Susquehanna. This is just one of hundreds of Double-crested Cormorants we watched during our visit.Hungry cormorants gather along the base of the dam where ascending fish congregate and become further disoriented by water turbulence.Fishing efforts here can bring great success to these accomplished piscivores.Latching onto an oversize Gizzard Shad can make you very popular with your peers.So popular that you may never have the opportunity to eat your lunch.Take it from this old bird: you’ve gotta swallow ’em fast, head first, tail and all.A Bald Eagle hauls off a Gizzard Shad.An Osprey saw this Gizzard Shad swimming close enough to the water’s surface to dive in and snag it with its talons.And yet another successful Bald Eagle calls out to its mate as it approaches its nest and hungry young.An angler releases a small Striped Bass caught on a shad dart while fishing for Hickory Shad. To reduce pressure on their populations during the spring spawning run, the “Striper” harvest is presently closed. The fishing season resumes later this month in some areas, in June within others. On the Susquehanna Flats and other Chesapeake Bay waters, Striped Bass are also known as “Rockfish”.This angler is reeling in a big one.A nice Channel Catfish weighed in at about six pounds and was released.This angler brought in yet another interesting catch.The White Perch (Morone americana) is a bay species that ascends the Chesapeake’s tributaries to spawn during the spring. On the lower Susquehanna, numbers of this relative of the Striped Bass are falling, very possibly due to depredation by invasive snakeheads, Blue Catfish, and Flathead Catfish.A Double-crested Cormorant does its duty and snatches up an invasive Blue Catfish. Very large Blue Catfish exceeding 24 inches in length are becoming increasingly plentiful on the upper Chesapeake and its tributaries resulting in a significant negative impact on the aquatic ecosystems there. Like the Northern Snakehead and Flathead Catfish, these invasive species are very palatable and anglers are encouraged to catch and keep as many as they like.Maryland DNR sign at Fisherman’s Park.What can we do about the plague of Northern Snakeheads (Channa argus) in the Susquehanna? Well, let’s start by answering a question with a question…Why deplete ocean stocks when you can follow this angler’s example and harvest excellent fillets while helping to control an invasive species at the same time? And no, you don’t have to call them “Chesapeake Channa” if you don’t want to. Though you will make us laugh if you start calling them “Susquehanna Channa” or just “Susquechanna” from time to time.
This petite Eastern Cottontail somehow found a path through weekend traffic to discover an abundant supply of lush green Indian Strawberry (Potentilla indica) leaves in the garden at susquehannawildlife.net headquarters. The widely naturalized Indian Strawberry, also known as Mock Strawberry, is native to Asia. It is most easily recognized by its bright yellow flowers which soon yield edible, but not very tasty, little red fruits. I wonder, might the berries be more palatable if dipped in a melted-down chocolate bunny? Food for thought, unless of course you have an aversion to hare in your romantic confections.
Have you noticed a purple haze across the fields right now? If so, you may have wondered, “What kind of flowers are they?”
A purple haze of color stretches across fields not already green with cold-season crops like winter wheat.
Say hello to Purple Dead Nettle (Lamium purpureum), a non-native invasive species that has increased its prevalence in recent years by finding an improved niche in no-till cropland. Purple Dead Nettle, also known as Red Dead Nettle, is native to Asia and Europe. It has been a familiar early spring “weed” in gardens, along roadsides, and in other disturbed ground for decades.
Purple Dead Nettle owes its new-found success to the timing of its compressed growing season. Its tiny seeds germinate during the fall and winter, after crops have been harvested and herbicide application has ended for the season. The plants flower early in the spring and are thus particularly attractive to Honey Bees and other pollinators looking for a source of energy-rich nectar as they ramp up activity after winter lock down. In many cases, Purple Dead Nettle has already completed its flowering cycle and produced seeds before there is any activity in the field to prepare for planting the summer crop. The seeds spend the warmer months in dormancy, avoiding the hazards of modern cultivation that expel most other species of native and non-native plants from the agricultural landscape.
Flowering Purple Dead Nettle as a volunteer cover crop among last year’s corn stubble in a no-till field.Like the flowers of orchids, Purple Hedge Nettle blossoms are described as yoke shaped or bilateral (zygomorphic). Psychedelic experiences are produced only through observation, not by ingestion. A member of the mint family, its edible young leaves and tops have nutritional value, making a unique addition to salads and soups.We call them “weeds”, but what do we know? Purple Dead Nettle, Common Dandelion, and Shepherd’s Purse (Capsella bursa-pastoris), three edible non-native invasive species with similar life cycles seen here flowering along a rural road among fields where intensive farming is practiced. Shepard’s Purse, like many members of the mustard family, is already producing seeds at the bottom of the flower cluster by the time the uppermost buds open for business.In preparation for seeding of a warm-season crop, herbicide is applied on a no-till field to kill Shepherd’s Purse and other cool-season plants. To help prevent sediment and nutrient discharge from lands where high-intensity agriculture is practiced, no-till methods are used to reduce runoff from the areas of bare soil that would otherwise be created by traditional plowing.
While modern farming has eliminated a majority of native plant and animal species from agricultural lands of the lower Susquehanna valley, its crop management practices have simultaneously invited vigorous invasion by a select few non-native species. High-intensity farming devotes its acreage to providing food for a growing population of people—not to providing wildlife habitat. That’s why it’s so important to minimize our impact on non-farm lands throughout the remainder of the watershed. If we continue subdividing, paving, and mowing more and more space, we’ll eventually be living in a polluted semi-arid landscape populated by little else but non-native invasive plants and animals. We can certainly do better than that.
Rising prices, an exhausted workforce, political polarization, and pandemic fatigue—times are tough. Product shortages have the consumer culture in a near panic. Some say the future just isn’t what it used to be.
Well, Uncle Tyler Dyer reminds us that things could be worse. He shares with us this observation, “Man, as long as people are spending money poisoning the weeds on their lawns instead of eating them, things aren’t that bad.”
Uncle Ty is particularly fond of the Common Dandelion (Taraxacum officinale), “Check it out. Roasted dandelion roots can make a coffee substitute, the blossoms a wine, and the leaves used to create my favorites, nutrient-dense salads or green vegetable dishes.”
The Common Dandelion is despised by many as a “weed”. To others it is a beautiful flowering plant that happens to be quite edible. Native to Europe and Asia, North American varieties of Common Dandelion are an escape from cultivation, originally imported as a food crop. Uncle Ty’s great-grandparents never would have dreamed of killing them with herbicides instead of harvesting them.Uncle Ty Dyer’s lunch, fresh dandelion greens and hot bacon dressing.
So have a homegrown salad and remember, maybe things aren’t that bad after all.
Meet the Double-crested Cormorant, a strangely handsome bird with a special talent for catching fish. You see, cormorants are superb swimmers when under water—using their webbed feet to propel and maneuver themselves with exceptional speed in pursuit of prey.
Like many species of birds that dive for their food, Double-crested Cormorants run across the surface of the water to gain speed for a takeoff. Smaller wings may make it more difficult to get airborne, but when folded, they provide improved streamlining for submerged swimming.
Double-crested Cormorants, hundreds of them, are presently gathered along with several other species of piscivorous (fish-eating) birds on the lower Susquehanna River below Conowingo Dam near Rising Sun, Maryland. Fish are coming up the river and these birds are taking advantage of their concentrations on the downstream side of the impoundment to provide food to fuel their migration or, in some cases, to feed their young.
Double-crested Cormorants, mostly adult birds migrating toward breeding grounds to the north, are gathered on the rocks on the east side of the river channel below Conowingo Dam. A Great Blue Heron from a nearby rookery can be seen at the center of the image.Bald Eagles normally gather in large numbers at Conowingo Dam in the late fall and early winter. Presently there are more than 50 there, and the majority of them are breeding age adults. Presumably they are still on their way north to nest. Meanwhile, local pairs are already feeding young, so it seems these transient birds are running a bit late. Many of them can be seen on the rocks along the east side of the river channel,……on the powerline trestles on the island below the dam……in the trees along the east shore,……and in the trees surrounding Fisherman’s Park on the west shore.
In addition to the birds, the movements of fish attract larger fish, and even larger fishermen.
Anglers gather to fish the placid waters below the dam’s hydroelectric powerhouse . Only a few of the generating turbines are operating, so the flow through the dam is minimal.Some water is being released along the west shoreline to attract migratory river herring to the west fish lift for sorting and retention as breeding stock for a propagation program. The east lift, the passage that hoists American Shad (Alosa sapidissima) to a trough that allows them to swim over the top of the dam to waters upriver, will begin operating as soon as these larger migratory fish begin arriving.
The excitement starts when the sirens start to wail and the red lights begin flashing. Yes friends, it’s showtime.
Red lights and sirens are a warning that additional flow is about to be released from the dam. Boaters should anticipate rough water and persons in and along the river need to seek higher ground immediately.Gates are opened at mid-river to release a surge of water through the dam.The wake from the release quickly reaches the shoreline, raising the water level in moments.Experienced anglers know that the flow through the dam gets fish moving and can improve the catch significantly, especially in spring when many species are ascending the river.
Within minutes of the renewed flow, birds are catching fish.
A Double-crested Cormorant with a young Channel Catfish (Ictalurus punctatus).A Double-crested Cormorant fleeing others trying to steal its Channel Catfish.Another Double-crested Cormorant eating a Channel Catfish. Did you realize that Channel Catfish were an introduced species in the Susquehanna River system?An Osprey with a stick, it’s too busy building a nest right now to fish.Great Blue Herons swallow their prey at the spot of capture, then fly back to the nest to regurgitate a sort of “minced congealed fish product” to their young.
Then the anglers along the wave-washed shoreline began catching fish too.
This young man led off a flurry of catches that would last for the remainder of the afternoon.Though Gizzard Shad are filter feeders that don’t readily take baits and lures, they are regularly foul-hooked and reeled in from the large schools that ascend the river in spring.Gizzard Shad are very abundant in the lower Susquehanna, providing year-round forage for many species of predatory animals including Bald Eagles.A Double-crested Cormorant swallowing a Gizzard Shad.This angler soon helped another fisherman by landing his large catch, a Northern Snakehead (Channa argus).The teeth of a Northern Snakehead are razor sharp. It is an aggressive non-native invasive species currently overtaking much of the Lower Susquehanna River Watershed. Anglers are encouraged to fish for them, catch them, keep them, and kill them at the site of capture. Never transport a live Northern Snakehead anywhere at any time. It is illegal in both Maryland and Pennsylvania to possess a live snakehead. Northern Snakehead advisory sign posted at Exelon Energy’s Conowingo Fishermen’s Park.A stringer of Northern Snakeheads. This species was imported from Asia as a food fish, so it has excellent culinary possibilities. It’s better suited for a broiler or frying pan than a river or stream.Another stringer of Northern Snakeheads. It’s pretty safe to say that they have quickly become one of the most abundant predatory fish in the river. Their impact on native species won’t be good, so catch and eat as many as you can. Remember, snakeheads swim better in butter and garlic than in waters with native fish.This foul-hooked Shorthead Redhorse (Moxostoma macrolepidotum), a native species of sucker, was promptly released.Striped Bass are anadromous fish that leave the sea in spring to spawn in fresh water. They ascend the Susquehanna in small numbers, relying upon the operation of the fish passages at the Conowingo, Holtwood, Safe Harbor, and York Haven Dams to continue their journey upstream. During spring spawning, Striped Bass in the Susquehanna River and on the Susquehanna Flats portion of the upper Chesapeake Bay are not in season and may not be targeted, even for catch-and-release. This accidental catch was immediately turned loose.After removal from the hook, this hefty Smallmouth Bass was returned to the river. Many anglers are surprised to learn that Smallmouth Bass are not native to the Susquehanna basin.This angler’s creel contains a Northern Snakehead (left) and a Walleye (right). Did you know that the Walleye (Sander vitreus) is an introduced species in the Susquehanna watershed?By late afternoon, anglers using shad darts began hooking into migrating Hickory Shad (Alosa mediocris), a catch-and-release species in Maryland.Hickory Shad are recognized by their lengthy lower jaw. They are anadromous herring that leave the sea to spawn in freshwater streams. Hickory Shad ascend the Susquehanna as far as Conowingo Dam each year, but shy away from the fish lifts. Downriver from the dam, they do ascend Deer Creek along the river’s west shore and Octoraro Creek on the east side. In Pennsylvania, the Hickory Shad is an endangered species.A Hickory Shad angled on a dual shad dart rig. During the spring spawning run, they feed mostly on small fish, and are the most likely of the Susquehanna’s herring to take the hook.Simultaneous hook-ups became common after fours hours worth of release water from the dam worked its way toward the mouth of the river and got the schools moving. Water temperatures in the mid-to-upper-fifties trigger the ascent of Hickory Shad. On the Susquehanna, those temperatures were slow to materialize in the spring of 2021, so the Hickory Shad migration is a bit late.Catch-and-release fishing for Hickory Shad appears to be in full swing not only at the dam, but along the downstream shoreline to at least the mouth of Deer Creek at Susquehanna State Park too.Many Hickory Shad could be seen feeding on some of the millions of caddisflies (Trichoptera) swarming on the river. These insects, along with earlier hatches of Winter Stoneflies (Taeniopterygidae), not only provide forage for many species of fish, but are a vital source of natural food for birds that migrate up the river in March and April each year. Swallows, Ring-billed Gulls, and Bonaparte’s Gulls are particularly fond of snatching them from the surface of the water.A Winter Stonefly (Taeniopterygidae) from an early-season hatch on the Susquehanna River at the Veteran’s Memorial Bridge at Columbia/Wrightsville, Pennsylvania. (March 3, 2021)Just below Conowingo Dam, a lone fly fisherman was doing a good job mimicking the late-April caddisfly hatch, successfully reeling in numerous surface-feeding Hickory Shad.You may have noticed the extraordinary number of introduced fish species listed in this account of a visit to Conowingo Dam. Sorry to say that there are two more: the Flathead Catfish (Pylodictis olivaris) and the Blue Catfish (Ictalurus furcatus). Like the Northern Snakehead, each has become a plentiful invasive species during recent years. Unlike the Northern Snakehead, these catfish are “native transplants”, species introduced from populations in the Mississippi River and Gulf Slope drainages of the United States. So if you visit the area, consider getting a fishing license and catching a few. Like the snakeheads, they too are quite palatable.
The arrival of migrating Hickory Shad heralds the start of a movement that will soon include White Perch, anadromous American Shad, and dozens of other fish species that swim upstream during the springtime. Do visit Fisherman’s Park at Conowingo Dam to see this spectacle before it’s gone. The fish and birds have no time to waste, they’ll soon be moving on.
To reach Exelon’s Conowingo Fisherman’s Park from Rising Sun, Maryland, follow U.S. Route 1 south across the Conowingo Dam, then turn left onto Shuresville Road, then make a sharp left onto Shureslanding Road. Drive down the hill to the parking area along the river. The park’s address is 2569 Shureslanding Road, Darlington, Maryland.
A water release schedule for the Conowingo Dam can be obtained by calling Exelon Energy’s Conowingo Generation Hotline at 888-457-4076. The recording is updated daily at 5 P.M. to provide information for the following day.
And remember, the park can get crowded during the weekends, so consider a weekday visit.
