Herring (Clupeidae) – LIFE IN THE LOWER SUSQUEHANNA RIVER WATERSHED

March 28, 2024March 28, 2024

Chesapeake Bay Maritime Accidents and Their Impact on Susquehanna Wildlife

Tuesday’s collision of the container ship Dali into Baltimore’s Francis Scott Key Bridge and the nearly immediate collapse of the span into the chilly waters below reminds us just how unforgiving and deadly maritime accidents can be. Upon termination of rescue and recovery operations, salvage and cleanup will be prioritized as the next steps in the long-term process of reopening the navigable waters to ship traffic and construction of a new bridge. Part of the effort will include monitoring for leaks of fuels and other hazardous materials from the ship, its damaged cargo containers, and vehicles and equipment that were on the bridge when it failed.

Dali vs. Francis Scott Key Bridge — Damage to the hull of the Dali and to the cargo containers on her deck could lead to leaks of hazardous liquids or other materials into Chesapeake Bay. (United States Army Corps of Engineers Baltimore image)

On the waters and shores of today’s Chesapeake, numerous county, state, and federal agencies, including the United States Coast Guard, monitor and inspect looking for conditions and situations that could lead to point-source or accidental discharges of petroleum products and other hazardous materials into the bay. Many are trained, equipped, and organized for emergency response to contain and mitigate spills upon detection. But this was not always the case.

Through much of the twentieth century, maritime spills of oil and other chemicals magnified the effects of routine discharges of hazardous materials and sanitary sewer effluent into the Chesapeake and its tributaries. The cumulative effect of these pollutants progressively impaired fisheries and bay ecosystems leading to noticeable declines in numbers of many aquatic species. Rather frequently, spills or discharges resulted in conspicuous fish and/or bird kills.

One of the worst spills occurred near the mouth of the Potomac River on February 2, 1976, when a barge carrying 250,000 gallons of number 6 oil sank in a storm and lost its cargo into the bay. During a month-long cleanup, the United States Coast Guard recovered approximately 167,000 gallons of the spilled oil, the remainder dispersed into the environment. A survey counted 8,469 “sea ducks” killed. Of the total number, the great majority were Horned Grebes (4,347 or 51.3%) and Long-tailed Ducks (2,959 or 34.9%). Other species included Surf Scoter (Melanitta perspicillata) (405 or 4.8%), Common Loon (195 or 2.3%), Bufflehead (166 or 2.0%), Ruddy Duck (107 or 1.3%), Common Goldeneye (78 or 0.9%), Tundra Swan (46 or 0.5%), Greater Scaup (19 or 0.2%), American Black Duck (12 or 0.2%), Common Merganser (11 or 0.1%), Canvasback (10 or 0.1%), Double-crested Cormorant (10 or 0.1%), Canada Goose (8 or 0.1%), White-winged Scoter (Melanitta deglandi) (7 or 0.1%), Redhead (5 or 0.1%), gull species (10 or 0.1%), miscellaneous ducks and herons (13 or 0.2%) and unidentified (61 or 0.7%). During the spring migration, a majority of these birds would have made their way north and passed through the lower Susquehanna valley. The accident certainly impacted the occurrence of the listed species during that spring in 1976, and possibly for a number of years after.

Horned Grebe during migration on the Susquehanna near Haldeman Riffles. — Of the 8,469 birds killed by the February 2, 1976, oil spill on the Chesapeake, 51.3% (4,347) were Horned Grebes. Many of them would have migrated north through the Lower Susquehanna River Watershed during the coming spring.

The Federal Water Pollution Control Act Amendments of 1972, commonly known as the Clean Water Act, put teeth into the original FWCPCA of 1948 and began reversing the accumulation of pollutants in the bay and other bodies of water around the nation. Additional amendments in 1977 and 1987 have strengthened protections and changed the culture of “dump-and-run” disposal and “dilution-is-the-solution” treatment of hazardous wastes. During the late nineteen-seventies and early nineteen-eighties, emergency response teams and agencies began organizing to control and mitigate spill events. The result has been a greater awareness and competency for handling accidental discharges of fuels and other chemicals into Chesapeake Bay and other waterways. These improvements can help minimize the environmental impact of the Dali’s collision with the Francis Scott Key Bridge in Baltimore.

Oil spills and other pollution in the Chesapeake can impact populations of migratory fish including the anadromous Hickory Shad which are presently transiting the bay on their way to the waters of the Susquehanna below Conowingo Dam.

SOURCES

Roland, John V., Moore, Glenn E., and Bellanca, Michael A. 1977. “The Chesapeake Bay Oil Spill—February 2, 1976: A Case History”. International Oil Spill Conference Proceedings (1977). 1977 (1): 523-527.

December 19, 2022

Photo of the Day

A juvenile Ring-billed Gull with a freshly caught Gizzard Shad is pursued by a hungry adult Great Black-backed Gull on the Susquehanna at Conowingo Dam.

April 25, 2021April 22, 2022

Conowingo Dam: Cormorants, Eagles, Snakeheads and a Run of Hickory Shad

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…

…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.

November 17, 2020November 17, 2020

Bald Eagles Arriving at Conowingo Dam

You need to see this to believe it—dozens, sometimes hundreds, of Bald Eagles doing their thing and you can stand or sit in just one place to take it all in.

Conowingo Dam on the Susquehanna River near Darlington, Maryland, attracts piscivores galore. Young Gizzard Shad (Dorosoma cepedianum) and other small fishes are temporarily stunned as they pass through the turbines and gated discharges at the hydroelectric facility’s power house. Waiting for them in the rapids below are predatory fishes including Striped Bass (Morone saxatilis), White Perch (Morone americana), several species of catfishes, and more. From above, fish-eating birds are on the alert for a disoriented turbine-traveler they can easily seize for a quick meal.

U.S. Route 1 crosses the Susquehanna River atop the Conowingo Dam. Conowingo Fisherman’s Park, the observation site for the dam’s Bald Eagles and other birds, is located downstream of the turbine building along the river’s west (south) shore. As the name implies, the park is a superb location for angling.

Heed this warning. Close your windows and sunroof or the vultures will subject your vehicle’s contents to a thorough search for food. Then they’ll deposit a little consolation prize on your paint.

Scavenging Black Vultures congregate by the hundreds at Conowingo Dam to clean up the scraps left behind by people and predators. They’ll greet you right in the parking lot.

Photographers line up downstream of the turbine building for an opportunity to get the perfect shot of a Bald Eagle.

The operator of the Conowingo Hydroelectric Generating Station, Exelon Energy, provides clean comfortable facilities for fishing, sightseeing, and wildlife observation.

There’s almost always a Peregrine Falcon zooming around the dam to keep the pigeons on their toes.

Double-crested Cormorants on the boulders that line the channel below the dam. Hundreds are there right now.

Double-crested Cormorants dive for fish near the power house discharge, which, while just one small generator is operating, seems nearly placid. The feeding frenzy really gets going when Conowingo begins generating with multiple large turbines and these gently flowing waters become torrential rapids filled with disoriented fishes.

Ring-billed Gulls seek to snag a small fish from the water’s surface.

After successfully nabbing shad or perch, these Double-crested Cormorants need to swallow their catch fast or risk losing it. Stealing food is a common means of survival for the gulls, eagles, and other birds found here.

Where do migrating eagles go? There are, right now, at least 50 Bald Eagles at Conowingo Dam, with more arriving daily. Numbers are likely to peak during the coming weeks.

Eagles can be seen perched in the woods along both river shorelines, even in the trees adjacent to the Conowingo Fisherman’s Park car lot. Others take stand-by positions on the boulders below the dam.

To remind visiting eagles that they are merely guests at Conowingo, a resident Bald Eagle maintains a presence at its nest on the wooded slope above Fisherman’s Park. Along the lower Susquehanna, female Bald Eagles lay eggs and begin incubation in January.

When an eagle decides to venture out and attempt a dive at a fish, that’s when the photographers rush to their cameras for a chance at a perfect shot.

The extraordinary concentrations of Bald Eagles at Conowingo make it an excellent place to study the plumage differences between birds of various ages.

Here’s a first-year Bald Eagle, also known as a hatch-year or juvenile bird.

A second-year or Basic I immature Bald Eagle. Note the long juvenile secondaries giving the wings a ragged-looking trailing edge.

A third-year or Basic II immature Bald Eagle.

A second-year/Basic I immature Bald Eagle (top) and a third-year/Basic II immature Bald Eagle (bottom).

A second-year/Basic I immature Bald Eagle (bottom) and a third-year/Basic II immature Bald Eagle (top). Note the white feathers on the backs of eagles in these age classes.

A third-year/Basic II immature Bald Eagle perched in a tree alongside the parking area. Note the Osprey-like head plumage.

A sixth-year or older adult Bald Eagle in definitive plumage (left) and a fourth-year or Basic III immature Bald Eagle (right).

If you want to see the Bald Eagles at Conowingo Dam, don’t wait. While many birds are usually present throughout the winter, the large concentrations may start dispersing as early as December when eagles begin wandering in search of other food sources, particularly if the river freezes.

A pair of Bald Eagles is already working on a nest atop this powerline trestle downstream of Conowingo Dam. By late December, most adult eagles will depart Conowingo to begin spending their days establishing and defending breeding territories elsewhere. Any non-adult eagles still loitering around the dam will certainly begin receiving encouragement from the local nesting pair(s) to move along as well.

As Bald Eagle numbers continue to increase, expect the parking lot to become full during weekends and over the Thanksgiving holiday. To avoid the crowds, plan to visit during a weekday.

You can get the generating schedule for the Conowingo Dam by calling the Conowingo Generation Hotline at 888-457-4076. The recording is updated daily at 5 P.M. to provide information for the following day.