What better way to pass a bright, sunny afternoon than to beat the heat by loafing atop a bridge spanning a small coldwater stream? We just lingered in the shade cast by an overarching tree and watched to see what might come by…
The Eastern Blacknose Dace is the most widespread and usually the most numerous minnow in coldwater streams throughout the Lower Susquehanna River Watershed. Sightings from our lookout at a crossing on the East Branch Standing Stone Creek, a tributary of the Juniata River, were in accordance with this generalization.The presence of these Eastern Blacknose Dace in close proximity to a male Tessellated Darter’s nest has him unfurling his flag-like dorsal fins in an attempt to intimidate the much larger minnows.He won’t be fully satisfied until they leave the area, so he’ll keep displaying his banners.Satisfied the invaders are gone, at least for now, he secures his sails, but continues to stand watch over the eggs, which are probably concealed beneath the boulder on the right.As it searches for invertebrates and other sources of food along the bottom of East Branch Standing Stone Creek, a juvenile White Sucker stirs up organic material derived chiefly from fallen leaves and other plant matter. Draining exclusively from dense woodlands in Rothrock State Forest, this waterway collects minimal quantities of water-polluting nutrients and sediments. The substrate is mostly sand, gravel, and cobble among boulders of various sizes.Except for some stormwater runoff from forest roads in its headwaters, the first significant source of thermal pollution on East Branch Standing Stone Creek as it tumbles toward the Juniata is a recreation impoundment at Greenwood Furnace State Park. This Rainbow Trout, which was probably stocked there for angling earlier this spring, is already showing the effects of warming water. As lake temperatures rise into and above the mid-seventies, trout become stressed and are especially susceptible to other factors that can prove fatal. These include parasites, poor nutrition, bacterial and fungal infections, and predation. Because they require well-oxygenated water to survive, trout are especially vulnerable to diminishing oxygen levels in warming and/or polluted waters, so hypoxia is a real concern. From our lookout just upstream from the lake, we watched as this struggling Rainbow Trout, apparently seeking refuge from the mid-day conditions in the sun-drenched impoundment, ascended the cold stream and took cover in some shade.In waters up the creek from the lake, trout with smaller proportions than those typically stocked for angling have been able to not only survive year-round, they are reproducing there. From our perch over East Branch Standing Stone Creek, we quietly observed this juvenile Brown Trout, a descendant of non-native individuals introduced in an attempt to establish a population of “wild trout” in the waterway.Brown Trout spawn in East Branch Standing Stone Creek in November. The eggs hatch within a month or two and the fry hide among the gravel, cobble, and rock of the stream bed. Still in its first year of life, this juvenile already resembles an adult, only traces of the vertical bars called “parr marks” remain along its flanks,……but this is still a petite little fish. Compare it to the walnuts on the stream bottom to the right. In a small stream, Brown Trout reach sexual maturity at a very small size, but could be in their third or fourth year of life when it happens.A population of the Susquehanna watershed’s native salmonid, the Brook Trout, lives and reproduces in East Branch Standing Stone Creek as well. This juvenile began life in much the same way and at about the same time of year as the non-native Brown Trout with which it will have to compete for survival. However, we noticed that this fingerling’s change in physical appearance is not as expedient as that of its introduced competitor. While telltale signs of an adult “brookie” are starting to show, the vertical “parr marks” of a young trout are still quite apparent, and will likely remain visible throughout its first year and beyond. Later in the summer, the dorsal surface of this fish will darken and the vermiculations of an adult Brook Trout should become evident. Most Brook Trout reach sexual maturity during their second year of life, so if all goes well, this could very well be one of next year’s breeders.
Greenwood Furnace State Park and East Branch Standing Stone Creek are located within Rothrock State Forest in northeastern Huntingdon County, Pennsylvania—just over Stone Mountain north of Belleville and the Kishacoquillas Valley on PA Route 305. To identify fish and other aquatic life in clear waters, you’ll need only a pair of close-focus binoculars or a camera with a telephoto lens. Polarized sunglasses really help penetrate the surface glare and shimmer, particularly on breezy days, making them a great fishwatching accessory for spotting your subjects of study.
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.
Matt Kofroth, Watershed Specialist with the Lancaster County Conservation District, operates the electrofishing wand in Conewago Creek while his team members prepare to net and collect momentarily-stunned fish. Three other electrofishing units operated by staff from the Susquehanna River Basin Commission and aided by teams of netters were in action at other sample locations along the Conewago on this day.Really big fish, such as this Common Carp (Cyprinus carpio), were identified, counted, and immediately returned to the water downstream of the advancing electrofishing team. Other fish, such as the Swallowtail Shiner, Redbreast Sunfish (Lepomis auritus), Fallfish, and suckers seen here, were placed in a sorting tank.Fallfish (Semotilus corporalis) are very active and require plenty of dissolved oxygen in the water to survive. Fallfish, Rainbow Trout (Oncorhynchus mykiss), and Smallmouth Bass (Micropterus dolomieu) were quickly identified and removed from the sorting tank for release back into the stream. Other larger, but less active fish, including suckers, quickly followed.Small fish like minnows were removed from the sorting tank for a closer look in a hand-held viewing tank. This Fathead Minnow (Pimephales promelas) was identified, added to the tally sheet, and released back into the Conewago. The Fathead Minnow is not native to the Susquehanna drainage. It is the minnow most frequently sold as bait by vendors.A breeding condition male Bluntnose Minnow (Pimephales notatus).The Cutlips Minnow (Exoglossum maxillingua) is a resident of clear rocky streams. Of the more than 30 species collected during the day, two native species which are classified as intolerant of persisting stream impairment were found: Cutlips Minnow and Swallowtail Shiner.The Central Stoneroller (Campostoma anomalum) is a benthic feeder in creeks over gravel and sand.The Eastern Blacknose Dace (Rhinichthys atratulus) is found in clear water over pebble and stone substrate.The Longnose Dace (Rhinichthys cataractae) is another species of pebbly rocky streams.A juvenile Golden Shiner (Notemigonus crysoleucas). Adults lack the side stripe and grow to the size of a sunfish.A Swallowtail Shiner (Notropis procne) and a very young White Sucker (Catostomus commersonii) in the upper left of the tank.A probable Spotfin Shiner (Cyprinella spiloptera).A breeding male Cyprinella shiner, probably a Spotfin Shiner. Show-off!The Margined Madtom (Noturus insignis) is a small native catfish of pebbly streams.The Banded Killifish (Fundulus diaphanus) is adept at feeding upon insects, including mosquitos.A young Rock Bass (Ambloplites rupestris). This species was introduced to the Susquehanna and its tributaries.The Greenside Darter (Etheostoma blennioides) is not native to the Susquehanna basin. The species colonized the Conewago Creek (east) from introduced local populations within the last five years.The Tessellated Darter (Etheostoma olmstedi) is a native inhabitant of the Susquehanna and its tributaries.The stars of the day were the American Eels (Anguilla rostrata).After collection, each eel was measured and weighed using a scale and dry bucket. This specimen checked in at 20 inches and one pound before being released.Prior to the construction of large dams, American Eels were plentiful in the Susquehanna and its tributaries, including the Conewago. They’ve since been rarities for more than half a century. Now they’re getting a lift.American Eels serve as an intermediate host for the microscopic parasitic glochidia (larvae) of the Eastern Elliptio (Elliptio complanata), a declining native freshwater mussel of the Lower Susquehanna River Watershed. While feeding on their host (usually in its gills), the glochidia cause little injury and soon drop off to continue growth, often having assured distribution of their species by accepting the free ride. Freshwater mussels are filter feeders and improve water quality. They grow slowly and can live for decades.American Eels are a catadromous species, starting life as tiny glass eels in the saltwater of the Atlantic Ocean, then migrating to tidal brackish marshes and streams (males) or freshwater streams (females) to mature. This 20-incher probably attempted to ascend the Susquehanna as an elver in 2016 or 2017. After hitching a ride with some friendly folks, she bypassed the three largest dams on the lower Susquehanna (Conowingo, Holtwood, and Safe Harbor) and arrived in the Conewago where she may remain and grow for ten years or more. To spawn, a perilous and terminally fatal journey to the Sargasso Sea awaits her. (You may better know the area of the Sargasso Sea as The Bermuda Triangle…a perilous place to travel indeed!)
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.
