The Ecology of a Spring Creek

by

Eugene Macri Jr.

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© 2010 E. P. Macri Jr.

Spring creeks are different than other streams.  Limestone spring creeks are more different than most.  The state of Pennsylvania is blessed with a number of limestone spring creeks but you would never know it by the lack of care and protection both the DEP and Pennsylvania Fish and Boat Commission have given them.  Unfortunately, too many fly anglers and even some biologists don't quite understand them.  They wish to modify them to some model that exists in a photo or whatever they have in their head because many spring creeks don't resemble the prototypical trout stream they understand.  In England and some other places the greatest limestone spring creeks often called English Chalkstreams are manicured and mostly private.  In the US we treat them like we do most of our waters by dumping just about anything imaginable into the streams and aquifers and urbanizing them to meet our needs.  Limestone spring creeks are magic places something out of Excalibur where trout will often grow large and rise to minute flies to test the skill of the greatest fly anglers. (photo shows the Letort at Bonny Brook; ©2007 E. Macri)

The Pennsylvania limestone spring creeks of Cumberland and Franklin Counties have a number of similarities:

• They are low gradient streams at the bottom of valleys
• They all have a similar biogeochemistry
• They have a very narrow cold temperature range of around 46 to 52 f.
• They are small to medium size streams
• They have similar types of substrates
• They have similar types of water plants
• They have nearly identical macroinvertebrate communities
• They had at one time wild native strains of trout
• The fish in the streams all were fairly difficult to catch and sophisticated compared to their freestone cousins
• Most of the time these streams have very stable flows and volume of water
• Most do not have a genuine flood plain as compared to freestone streams
• The fish grow all year long
• They had an abundance of macroinvertebrates
• They all suffer from similar environmental problems including sedimentation, pesticides, development and aquifer withdrawal.
• Many of the insect populations in the stream had long emergence periods as compared to the same insects in nearby freestone streams.
• Because of the narrow temperature range, narrow substrate parameters, and current velocities this limits the diversity of these ecosystems but allows for the increasing of few populations to very large sizes that can exploit these niches. 
• Spring creeks are controlled by sunlight.  These stream need a lot of light and addition of too many trees and additional cover will actually limit productivity on these streams
• The trout in these streams become especially difficult because many of the things they feed upon have long emergence periods which allow the fish to get a very good light pattern of what they are eating.

So there you have it in a nutshell some of the most important characteristics of spring creeks in terms of ecology.  The environment shapes the trout and as Charlie Fox put it,   "these streams forced the fly fisherman to evolve or he wouldn't catch any fish. These streams made the fly fisherman. These streams made fly fishing what it is today!"