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LIFE IN THE LOWER SUSQUEHANNA RIVER WATERSHED
A Natural History of Conewago Falls—The Waters of Three Mile Island
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.
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.
With temperatures finally climbing to seasonable levels and with stormy sun filtering through the yellow-brown smoke coming our way courtesy of wildfires in Alberta and other parts of central Canada, we ventured out to see what might be basking in our local star’s refracted rays…
The deluge of rain that soaked the lower Susquehanna watershed during last week is now just a memory. Streams to the west of the river, where the flooding courtesy of the remnants of Hurricane Debby was most severe, have reached their crest and receded. Sliding away toward the Chesapeake and Atlantic is all that runoff, laden with a brew of pollutants including but not limited to: agricultural nutrients, sediment, petroleum products, sewage, lawn chemicals, tires, dog poop, and all that litter—paper, plastics, glass, Styrofoam, and more. For aquatic organisms including our freshwater fish, these floods, particularly when they occur in summer, can compound the effects of the numerous stressors that already limit their ability to live, thrive, and reproduce.
One of those preexisting stressors, high water temperature, can be either intensified or relieved by summertime precipitation. Runoff from forested or other densely vegetated ground normally has little impact on stream temperature. But segments of waterways receiving significant volumes of runoff from areas of sun-exposed impervious ground will usually see increases during at least the early stages of a rain event. Fortunately, projects implemented to address the negative impacts of stormwater flow and stream impairment can often have the additional benefit of helping to attenuate sudden rises in stream temperature.
Of the fishes inhabiting the Lower Susquehanna River Watershed’s temperate streams, the least tolerant of summer warming are the trouts and sculpins—species often described as “coldwater fishes”. Coldwater fishes require water temperatures below 70° Fahrenheit to thrive and reproduce. The optimal temperature range is 50° to 65° F. In the lower Susquehanna valley, few streams are able to sustain trouts and sculpins through the summer months—largely due to the effects of warm stormwater runoff and other forms of impairment.
Coldwater fishes are generally found in small spring-fed creeks and headwaters runs. Where stream gradient, substrate, dissolved oxygen, and other parameters are favorable, some species may be tolerant of water warmer than the optimal values. In other words, these temperature classifications are not set in stone and nobody ever explained ichthyology to a fish, so there are exceptions. The Brown Trout for example is sometimes listed as a “coldwater transition fish”, able to survive and reproduce in waters where stream quality is exceptionally good but the temperature may periodically reach the mid-seventies.
More tolerant of summer heat than the trouts, sculpins, and daces are the “coolwater fishes”—species able to feed, grow, and reproduce in streams with a temperature of less than 80° F, but higher than 60° F. Coolwater fishes thrive in creeks and rivers that hover in the 65° to 70° F range during summer.
What are the causes of modern-day reductions in coldwater and coolwater fish habitats in the lower Susquehanna River and its hundreds of miles of tributaries? To answer that, let’s take a look at the atmospheric, cosmic, and hydrologic processes that impact water temperature. Technically, these processes could be measured as heat flux—the rate of heat energy transfer per unit area per unit time, frequently expressed as watts per meter squared (W/m²). Without getting too technical, we’ll just take a look at the practical impact these processes have on stream temperatures.
HEAT FLUX PROCESSES IN A SEGMENT OF STREAM
Now that we have a basic understanding of the heat flux processes responsible for determining the water temperatures of our creeks and rivers, let’s venture a look at a few graphics from gauge stations on some of the lower Susquehanna’s tributaries equipped with appropriate United States Geological Survey monitoring devices. While the data from each of these stations is clearly noted to be provisional, it can still be used to generate comparative graphics showing basic trends in easy-to-monitor parameters like temperature and stream flow.
Each image is self-labeled and plots stream temperature in degrees Fahrenheit (bold blue) and stream discharge in cubic feet per second (thin blue).
The daily oscillations in temperature reflect the influence of several heat flux processes. During the day, solar (shortwave) radiation and convection from summer air, especially those hot south winds, are largely responsible for the daily rises of about 5° F. Longwave radiation has a round-the-clock influence—adding heat to the stream during the day and mostly shedding it at night. Atmospheric exchange including evaporative cooling may help moderate the rise in stream temperatures during the day, and certainly plays a role in bringing them back down after sunset. Along its course this summer, the West Conewago Creek absorbed enough heat to render it a warmwater fishery in the area of the gauging station. The West Conewago is a shallow, low gradient stream over almost its entire course. Its waters move very slowly, thus extending their exposure time to radiated heat flux and reducing the benefit of cooling by atmospheric exchange. Fortunately for bass, catfish, and sunfish, these temperatures are in the ideal range for warmwater fishes to feed, grow, and reproduce—generally over 80° F, and ideally in the 70° to 85° F range. Coolwater fishes though, would not find this stream segment favorable. It was consistently above the 80° F maximum and the 60° to 70° F range preferred by these species. And coldwater fishes, well, they wouldn’t be caught dead in this stream segment. Wait, scratch that—the only way they would be caught in this segment is dead. No trouts or sculpins here.
Look closely and you’ll notice that although the temperature pattern on this chart closely resembles that of the West Conewago’s, the readings average about 5 degrees cooler. This may seem surprising when one realizes that the Codorus follows a channelized path through the heart of York City and its urbanized suburbs—a heat island of significance to a stream this size. Before that it passes through numerous impoundments where its waters are exposed to the full energy of the sun. The tempering factor for the Codorus is its baseflow. Despite draining a smaller watershed than its neighbor to the north, the Codorus’s baseflow (low flow between periods of rain) was 96 cubic feet per second on August 5th, nearly twice that of the West Conewago (51.1 cubic feet per second on August 5th). Thus, the incoming heat energy was distributed over a greater mass in the Codorus and had a reduced impact on its temperature. Though the Codorus is certainly a warmwater fishery in its lower reaches, coolwater and transitional fishes could probably inhabit its tributaries in segments located closer to groundwater sources without stress. Several streams in its upper reaches are in fact classified as trout-stocked fisheries.
The Kreutz Creek gauge shows temperature patterns similar to those in the West Conewago and Codorus data sets, but notice the lower overall temperature trend and the flow. Kreutz Creek is a much smaller stream than the other two, with a flow averaging less than one tenth that of the West Conewago and about one twentieth of that in the Codorus. And most of the watershed is cropland or urban/suburban space. Yet, the stream remains below 80° F through most of the summer. The saving graces in Kreutz Creek are reduced exposure time and gradient. The waters of Kreutz Creek tumble their way through a small watershed to enter the Susquehanna within twenty-four hours, barely time to go through a single daily heating and cooling cycle. As a result, their is no chance for water to accumulate radiant and convective heat over multiple summer days. The daily oscillations in temperature are less amplified than we find in the previous streams—a swing of about three degrees compared to five. This indicates a better balance between heat flux processes that raise temperature and those that reduce it. Atmospheric exchange in the stream’s riffles, forest cover, and good hyporheic exchange along its course could all be tempering factors in Kreutz Creek. From a temperature perspective, Kreutz Creek provides suitable waters for coolwater fishes.
Muddy Creek is a trout-stocked fishery, but it cannot sustain coldwater species through the summer heat. Though temperatures in Muddy Creek may be suitable for coolwater fishes, silt, nutrients, low dissolved oxygen, and other factors could easily render it strictly a warmwater fishery, inhabited by species tolerant of significant stream impairment.
A significant number of stream segments in the Chiques watershed have been rehabilitated to eliminate intrusion by grazing livestock, cropland runoff, and other sources of impairment. Through partnerships between a local group of watershed volunteers and landowners, one tributary, Donegal Creek, has seen riparian buffers, exclusion fencing, and other water quality and habitat improvements installed along nearly ever inch of its run from Donegal Springs through high-intensity farmland to its mouth on the main stem of the Chiques just above its confluence with the Susquehanna. The improved water quality parameters in the Donegal support native coldwater sculpins and an introduced population of reproducing Brown Trout. While coldwater habitat is limited to the Donegal, the main stem of the Chiques and its largest tributary, the Little Chiques Creek, both provide suitable temperatures for coolwater fishes.
Despite its meander through and receipt of water from high-intensity farmland, the temperature of the lower Conewago (East) maxes out at about 85° F, making it ideal for warmwater fishes and even those species that are often considered coolwater transition fishes like introduced Smallmouth Bass, Rock Bass, Walleye, and native Margined Madtom. This survivable temperature is a testament to the naturally occurring and planted forest buffers along much of the stream’s course, particularly on its main stem. But the Conewago suffers serious baseflow problems compared to other streams we’ve looked at so far. Just prior to the early August storms, flow was well below 10 cubic feet per second for a drainage area of more than fifty square miles. While some of this reduced flow is the result of evaporation, much of it is anthropogenic in origin as the rate of groundwater removal continues to increase and a recent surge in stream withdraws for irrigation reaches its peak during the hottest days of summer.
A little side note—the flow rate on the Conewago at the Falmouth gauge climbed to about 160 cubic feet per second as a result of the remnants of Hurricane Debby while the gauge on the West Conewago at Manchester skyrocketed to about 20,000 cubic feet per second. Although the West Conewago’s watershed (drainage area) is larger than that of the Conewago on the east shore, it’s larger only by a multiple of two or three, not 125. That’s a dramatic difference in rainfall!
The temperatures at the Bellaire monitoring station, which is located upstream of the Conewago’s halfway point between its headwaters in Mount Gretna and its mouth, are quite comparable to those at the Falmouth gauge. Although a comparison between these two sets of data indicate a low net increase in heat absorption along the stream’s course between the two points, it also suggests sources of significant warming upstream in the areas between the Bellaire gauge and the headwaters.
The waters of the Little Conewago are protected within planted riparian buffers and mature woodland along much of their course to the confluence with the Conewago’s main stem just upstream of Bellaire. This tributary certainly isn’t responsible for raising the temperature of the creek, but is instead probably helping to cool it with what little flow it has.
Though mostly passing through natural and planted forest buffers above its confluence with the Little Conewago, the main stem’s critically low baseflow makes it particularly susceptible to heat flux processes that raise stream temperatures in segments within the two or three large agricultural properties where owners have opted not to participate in partnerships to rehabilitate the waterway. The headwaters area, while largely within Pennsylvania State Game Lands, is interspersed with growing residential communities where potable water is sourced from hundreds of private and community wells—every one of them removing groundwater and contributing to the diminishing baseflow of the creek. Some of that water is discharged into the stream after treatment at the two municipal sewer plants in the upper Conewago. This effluent can become quite warm during processing and may have significant thermal impact when the stream is at a reduced rate of flow. A sizeable headwaters lake is seasonally flooded for recreation in Mount Gretna. Such lakes can function as effective mid-day collectors of solar (shortwave) radiation that both warms the water and expedites atmospheric exchange.
Though Conewago Creek (East) is classified as a trout-stocked fishery in its upper reaches in Lebanon County, its low baseflow and susceptibility to warming render it inhospitable to these coldwater fishes by late-spring/early summer.
The removal of two water supply dams on the headwaters of Hammer Creek at Rexmont eliminated a large source of temperature fluctuation on the waterway, but did little to address the stream’s exposure to radiant and convective heat flux processes as it meanders largely unprotected out of the forest cover of Pennsylvania State Game Lands and through high-intensity farmlands in the Lebanon Valley. Moderating the temperature to a large degree is the influx of karst water from Buffalo Springs, located about two miles upstream from this gauging station, and other limestone springs that feed tributaries which enter the Hammer from the east and north. Despite the cold water, the impact of the stream’s nearly total exposure to radiative and other warming heat flux processes can readily be seen in the graphic. Though still a coldwater fishery by temperature standards, it is rather obvious that rapid heating and other forms of impairment await these waters as they continue flowing through segments with few best management practices in place for mitigating pollutants. By the time Hammer Creek passes back through the Furnace Hills and Pennsylvania State Game Lands, it is leaning toward classification as a coolwater fishery with significant accumulations of sediment and nutrients. But this creek has a lot going for it—mainly, sources of cold water. A core group of enthusiastic landowners could begin implementing the best management practices and undertaking the necessary water quality improvement projects that could turn this stream around and make it a coldwater treasure. An organized effort is currently underway to do just that. Visit Trout Unlimited’s Don Fritchey Chapter and Donegal Chapter to learn more. Better yet, join them as a volunteer or cooperating landowner!
For coldwater fishes, the thousands of years since the most recent glacial maximum have seen their range slowly contract from nearly the entirety of the once much larger Susquehanna watershed to the headwaters of only our most pristine streams. Through no fault of their own, they had the misfortune of bad timing—humans arrived and found coldwater streams and the groundwater that feeds them to their liking. Some of the later arrivals even built their houses right on top of the best-flowing springs. Today, populations of these fishes in the region we presently call the Lower Susquehanna River Watershed are seriously disconnected and the prospect for survival of these species here is not good. Stream rehabilitation, groundwater management, and better civil planning and land/water stewardship are the only way coldwater fishes, and very possibly coolwater fishes as well, will survive. For some streams like Hammer Creek, it’s not too late to make spectacular things happen. It mostly requires a cadre of citizens, local government, project specialists, and especially stakeholders to step up and be willing to remain focused upon project goals so that the many years of work required to turn a failing stream around can lead to success.
You’re probably glad this look at heat flux processes in streams has at last come to an end. That’s good, because we’ve got a lot of work to do.
Resilient to the pressures of flooding, ice scour, drought, and oft times really poor water quality, Water Willow (Dianthera americana, formerly Justicia americana) is the most common herbaceous plant on the Susquehanna’s non-forested alluvial islands. Yet, few know this native wildflower by name or reputation.
The spring of 2024 has been very kind to our beds of Water Willow. Rainfall in the Susquehanna watershed has been frequent enough to maintain river levels just high enough to keep the roots of the plants wet. During the interludes in storm activity, dry spells have rolled back any threat of flooding on the river’s main stem, thus eliminating chances of submerging the plants in muddy water and preventing the sun from keeping them warm, happy, and flowering early. Thundershowers throughout the basin earlier this week have now raised the river a few inches to inundate the base of the plants and make mats of Water Willow favorable places for newly hatched fry and other young fish to take refuge while they grow. Here’s a look…
By now you’ve come to appreciate the importance of Water Willow to the sustainability of our populations of fish and other aquatic life. Like similar habitat features that reduce sediment runoff and nutrient pollution, undisturbed stands of terrestrial, emergent, and submerged native plant species are essential to the viability of our freshwater food webs.
First there was the Nautilus. Then there was the Seaview. And who can forget the Yellow Submarine? Well, now there’s the S. S. Haldeman, and today we celebrated her shakedown cruise and maiden voyage. The Haldeman is powered by spent fuel that first saw light of day near Conewago Falls at a dismantled site that presently amounts to nothing more than an electrical substation. Though antique in appearance, the vessel discharges few emissions, provided there aren’t any burps or hiccups while underway. So, climb aboard as we take a cruise up the Susquehanna at periscope depth to have a quick look around!
Watertight and working fine. Let’s flood the tanks and have a peek at the benthos. Dive, all dive!
We’re finding that a sonar “pinger” isn’t very useful while running in shallow water. Instead, we should consider bringing along a set of Pings—for the more than a dozen golf balls seen on the river bottom. It appears they’ve been here for a while, having rolled in from the links upstream during the floods. Interestingly, several aquatic species were making use of them.
Well, it looks like the skipper’s tired and grumpy, so that’s all for now. Until next time, bon voyage!
You say you really don’t want to take a look back at 2020? Okay, we understand. But here’s something you may find interesting, and it has to do with the Susquehanna River in 2020.
As you may know, the National Weather Service has calculated the mean temperature for the year 2020 as monitored just upriver from Conewago Falls at Harrisburg International Airport. The 56.7° Fahrenheit value was the highest in nearly 130 years of monitoring at the various stations used to register official climate statistics for the capital city. The previous high, 56.6°, was set in 1998.
Though not a prerequisite for its occurrence, record-breaking heat was accompanied by a drought in 2020. Most of the Susquehanna River drainage basin experienced drought conditions during the second half of the year, particularly areas of the watershed upstream of Conewago Falls. A lack of significant rainfall resulted in low river flows throughout late summer and much of the autumn. Lacking water from the northern reaches, we see mid-river rocks and experience minimal readings on flow gauges along the lower Susquehanna, even if our local precipitation happens to be about average.
Back in October, when the river was about as low as it was going to get, we took a walk across the Susquehanna at Columbia-Wrightsville atop the Route 462/Veteran’s Memorial Bridge to have a look at the benthos—the life on the river’s bottom.
These improvements in water quality and wildlife habitat can have a ripple effect. In 2020, the reduction in nutrient loads entering Chesapeake Bay from the low-flowing Susquehanna may have combined with better-than-average flows from some of the bay’s lesser-polluted smaller tributaries to yield a reduction in the size of the bay’s oxygen-deprived “dead zones”. These dead zones typically occur in late summer when water temperatures are at their warmest, dissolved oxygen levels are at their lowest, and nutrient-fed algal blooms have peaked and died. Algal blooms can self-enhance their severity by clouding water, which blocks sunlight from reaching submerged aquatic plants and stunts their growth—making quantities of unconsumed nutrients available to make more algae. When a huge biomass of algae dies in a susceptible part of the bay, its decay can consume enough of the remaining dissolved oxygen to kill aquatic organisms and create a “dead zone”. The Chesapeake Bay Program reports that the average size of this year’s dead zone was 1.0 cubic miles, just below the 35-year average of 1.2 cubic miles.
Back on a stormy day in mid-November, 2020, we took a look at the tidal freshwater section of Chesapeake Bay, the area known as Susquehanna Flats, located just to the southwest of the river’s mouth at Havre de Grace, Maryland. We wanted to see how the restored American Eelgrass beds there might have fared during a growing season with below average loads of nutrients and life-choking sediments spilling out of the nearby Susquehanna River. Here’s what we saw.
We noticed a few Canvasbacks (Aythya valisineria) on the Susquehanna Flats during our visit. Canvasbacks are renowned as benthic feeders, preferring the tubers and other parts of submerged aquatic plants (a.k.a. submersed aquatic vegetation or S.A.V.) including eelgrass, but also feeding on invertebrates including bivalves. The association between Canvasbacks and eelgrass is reflected in the former’s scientific species name valisineria, a derivitive of the genus name of the latter, Vallisneria.
The plight of the Canvasback and of American Eelgrass on the Susquehanna River was described by Herbert H. Beck in his account of the birds found in Lancaster County, Pennsylvania, published in 1924:
“Like all ducks, however, it stops to feed within the county less frequently than formerly, principally because the vast beds of wild celery which existed earlier on broads of the Susquehanna, as at Marietta and Washington Borough, have now been almost entirely wiped out by sedimentation of culm (anthracite coal waste). Prior to 1875 the four or five square miles of quiet water off Marietta were often as abundantly spread with wild fowl as the Susquehanna Flats are now.”
Beck quotes old Marietta resident and gunner Henry Zink:
“Sometimes there were as many as 500,000 ducks of various kinds on the Marietta broad at one time.”
The abundance of Canvasbacks and other ducks on the Susquehanna Flats would eventually plummet too. In the 1950s, there were an estimated 250, 000 Canvasbacks wintering on Chesapeake Bay, primarily in the area of the American Eelgrass, a.k.a. Wild Celery, beds on the Susquehanna Flats. When those eelgrass beds started disappearing during the second half of the twentieth century, the numbers of Canvasbacks wintering on the bay took a nosedive. As a population, the birds moved elsewhere to feed on different sources of food, often in saltier estuarine waters.
Canvasbacks were able to eat other foods and change their winter range to adapt to the loss of habitat on the Susquehanna River and Chesapeake Bay. But not all species are the omnivores that Canvasbacks happen to be, so they can’t just change their diet and/or fly away to a better place. And every time a habitat like the American Eelgrass plant community is eliminated from a region, it fragments the range for each species that relied upon it for all or part of its life cycle. Wildlife species get compacted into smaller and smaller suitable spaces and eventually their abundance and diversity are impacted. We sometimes marvel at large concentrations of birds and other wildlife without seeing the whole picture—that man has compressed them into ever-shrinking pieces of habitat that are but a fraction of the widespread environs they once utilized for survival. Then we sometimes harass and persecute them on the little pieces of refuge that remain. It’s not very nice, is it?
By the end of 2020, things on the Susquehanna were getting back to normal. Near normal rainfall over much of the watershed during the final three months of the year was supplemented by a mid-December snowstorm, then heavy downpours on Christmas Eve melted it all away. Several days later, the Susquehanna River was bank full and dishing out some minor flooding for the first time since early May. Isn’t it great to get back to normal?
SOURCES
Beck, Herbert H. 1924. A Chapter on the Ornithology of Lancaster County, Pennsylvania. The Lewis Historical Publishing Company. New York, NY.
White, Christopher P. 1989. Chesapeake Bay, Nature of the Estuary: A Field Guide. Tidewater Publishers. Centreville, MD.
Here it is—just as it happened, recently in the lower Susquehanna valley.
SOURCES
Sedaghat, Safoura, Seyed Abbas Hoseini, Mohammad Larijani, and Khadijeh Shamekhi Ranjbar. 2013. “Age and Growth of Common Carp (Cyprinus carpio Linnaeus, 1758) in Southern Caspian Sea, Iran”. World Journal of Fish and Marine Sciences. 5:1. pp.71-73.
There are two Conewago Creek systems in the Lower Susquehanna River Watershed. One drains the Gettysburg Basin west of the river, mostly in Adams and York Counties, then flows into the Susquehanna at the base of Conewago Falls. The other drains the Gettysburg Basin east of the river, flowing through Triassic redbeds of the Gettysburg Formation and York Haven Diabase before entering Conewago Falls near the south tip of Three Mile Island. Both Conewago Creeks flow through suburbia, farm, and forest. Both have their capacity to support aquatic life impaired and diminished by nutrient and sediment pollution.
This week, some of the many partners engaged in a long-term collaboration to restore the east shore’s Conewago Creek met to have a look at one of the prime indicators of overall stream habitat health—the fishes. Kristen Kyler of the Lower Susquehanna Initiative organized the effort. Portable backpack-mounted electrofishing units and nets were used by crews to capture, identify, and count the native and non-native fishes at sampling locations which have remained constant since prior to the numerous stream improvement projects which began more than ten years ago. Some of the present-day sample sites were first used following Hurricane Agnes in 1972 by Stambaugh and Denoncourt and pre-date any implementation of sediment and nutrient mitigation practices like cover crops, no-till farming, field terracing, stormwater control, nutrient management, wetland restoration, streambank fencing, renewed forested stream buffers, or modernized wastewater treatment plants. By comparing more recent surveys with this baseline data, it may be possible to discern trends in fish populations resulting not only from conservation practices, but from many other variables which may impact the Conewago Creek Warmwater Stream ecosystem in Dauphin, Lancaster, and Lebanon Counties.
So here they are. Enjoy these shocking fish photos.
SOURCES
Normandeau Associates, Inc. and Gomez and Sullivan. 2018. Muddy Run Pumped Storage Project Conowingo Eel Collection Facility FERC Project 2355. Prepared for Exelon.
Stambaugh, Jr., John W., and Robert P. Denoncourt. 1974. A Preliminary Report on the Conewago Creek Faunal Survey, Lancaster County, Pennsylvania. Proceedings of the Pennsylvania Academy of Sciences. 48: 55-60.