Our team is growing! At the end of the semester, Ben Kline, an undergraduate at Penn State, contacted the lab looking for volunteer opportunities. We're always happy to introduce prospective fish biologists to our field, but with limited field time I wouldn't blame any volunteer for losing interest in the work we're doing right now. Not only has Ben not lost interest, but he's taken it upon himself to collect some really great data looking at how individual fish compete for access to thermal refuge. Ben has volunteered to provide some guest posts over the summer, which will chronicle his experience in the lab and a little about what interests him in fisheries science. So, welcome Ben with his looks at Penns Creek, and learn more about him here.
Down along a stream called Penns Creek, there’s a place for me
For as long as I can remember, Penns Creek has always been a part of my life. To be fair, I might be somewhat biased considering that my family farm has sat nestled on the bank of the Penns for over a hundred years. I often think back to my childhood sitting alongside the streambed, gazing into the murky water and just enjoying the quiet. If you have had the pleasure of spending some time on Penns Creek, then there is no denying that this location is certainly a lesser known gem of central Pennsylvania.
Penns Creek is a tributary of the Susquehanna River, which ultimately empties into the Chesapeake Bay and has a long running history in the state of Pennsylvania. The original name “John Penn’s Creek” was named for William Penn’s younger brother, but was eventually adapted to simply “Penns Creek”.
Penns Creek is considered to be Pennsylvania’s most impressive limestone stream in terms of size and length at a formidable 67.1-mile run. A limestone stream is characterized as being sourced primarily from groundwater, meaning that underground aquifers or springs are the source of water for the stream. This means the origin of the water feeding the stream could be countless miles from where the stream actually begins. Limestone streams are known to be shallow and slow moving, and typically are more resistant to changes in temperature once a certain set point is reached. The stream bottom consists primarily of gravel, mud, and sand substrate. Portions of the stream are littered with large boulders that add significant structure and habitat to the waterway and provide host to a variety of aquatic species.
The recreational use of Penns Creek is something that is well known to locals. Spending a day floating down the creek with your best buds or a nice day trip in the canoe or kayak sounds like the perfect way to spend a sunny Saturday in June. Aside from a nice paddle down the creek, Penns Creek also hosts countless opportunities for wildlife watchers with a large population of birds of prey, particularly Kingfishers and Bald Eagles. If birds aren’t for you, this is still a great place to catch a glimpse of painted turtles, muskrats, or even a mink along the streambank.
While Penns Creek offers a great number of opportunities in recreation, perhaps the most noteworthy way to spend ones time on Penns Creek is fishing. Penns Creek is one of the most productive trout fisheries in all of Pennsylvania. However, the Penns is also host to a number of other desirable species such as smallmouth bass, various panfish, and even the occasional walleye. These legendary trout waters are known to host extremely high densities of trout in certain sections of the creek, of which some portions are even considered Class A Wild Trout streams. Anglers have even reported catches exceeding 20 inches in length in some of these locations.
There are a few contributing factors to this highly productive environment. The secluded nature of much of Penns Creek aids in the preservation of these natural populations, with some portions of the creek only accessible by foot, or in some cases, bicycle. These portions of the creek contain large rocks that make excellent trout habitat and help to form deep pools and riffles. The stands of old growth forest that hug the banks of Penns Creek provide an excellent source of refuge for hatching insects from heavy spring rains and predators, which allows for abundant food supply in these locations. The nature of a natural limestone stream is that which enables the water to support abundant natural life, which in this case, is a dense insect population. Droves of caddisfly, stonefly, and mayfly nymphs provide for these productive trout waters. Penns Creek is well known for its hatches, and perhaps the most famous of all is the green drake hatch, which is sought by anglers across the entire country.
Habitat structure and food availability are two factors that make trout abundance high in Penns Creek; however, there is one resource that is becoming increasingly difficult to come by: cold water. Trout require thermal refuge, especially in the summer months when stream temperatures are known to rise significantly. In Penns Creek, the natural springs and seeping of cold groundwater provides cold habitat in the uppermost reaches of Penns Creek all the way into late August, which provides the trout with this limiting resource on a year-round basis.
Despite the presence of consistent cold water in the upper reaches of the Penns Creek that make for excellent trout habitat, the middle and lower sections face significant thermal issues. As the water moves father from its source, the shallow and slow-moving nature of Penns Creek causes the water temperature to rise. As stated before, the nature of the stream makes Penns Creek highly resistant to temperature changes once a significant increase is reached. Since trout require cold water to thrive, many trout populations begin to seek cold water tributaries as refuge in these lower reaches of the Penns.
This fragmented habitat may be the answer to sustaining these trout populations in times of thermal distress from rising stream temperatures. The lower third of the Penns becomes so warm in the summer that it is practically devoid of trout before it empties into the Susquehanna, and is now home to limited panfish and smallmouth bass populations only.
With climate change on the rise and cold water to support natural trout populations on the decline, we are currently seeking answers that may help us to better understand these growing concerns. I am currently working on a study that seeks to understand how individuals respond to a number of thermal conditions. This experiment hopes to identify what characteristics a fish might display that would make that individual more able to seek out and utilize these cold water refuges than others in a population. To do this, we are looking at a variety of data including movement, individual behavior, and genetics. The bulk of the work I am completing right now focuses on analyzing individual behavior and the interaction that individuals have with other members of the population.
There is much more to share about this upcoming project, but I will save that for another post. A very exciting summer awaits, so stay tuned to find out about the gritty details of our new project in the weeks to come.