Few words evoke more negative connotations in the angling world than carp, though I suspect in these parts that cormorant might come in a close second.
It seems we're an angling community that has come to hold certain species as desirable, and any threat to those ... well, let's just say anglers ... prefer not to deal with them.
Understanding how anglers relate to preferred fish helps explain the calculated response to an ongoing concern over the potential movement of carp into the Devils Lake region the past year.
Up to this point, carp have not been found in Devils Lake by fisheries biologists through test netting and other studies - an important fact when dealing with any potential transfer. If carp were already in a body of water, especially one of the magnitude of Devils Lake, it would be a moot point.
This particular carp transfer can be categorized as one in which nature is getting a helping hand, rather than a direct transfer of undesirable fish species by humans, such as the dumping of bait buckets by anglers or ad hoc stocking like transporting fish to other bodies of water.
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In the case of the upper Devils Lake basin, there is a hole in the continental divide. The Pembina River drainage is connected to the Devils Lake basin by a wetland in which water can flow to the north or south, depending on local water levels.
If carp find their way into Devils Lake, the end result and concern is still the same. Without knowing the exact time frame, biologists predict that if carp did get into Devils Lake, within a decade the walleye, perch and pike fishery would face severe and unwanted changes.
But why are carp so undesirable? In short, carp eat both small aquatic animals such as scud or freshwater shrimp and the vegetation that those small aquatic animals need. It's a double whammy competition that makes carp come out on top.
Their method of bottom feeding roots up vegetation and stirs up bottom sediments that prevent sunlight from reaching aquatic vegetation - sunlight plants need for growth and game fish need to see their quarry.
Think of it in terms of smaller game fish forming the building block for a thriving food chain in your favorite lake. With carp, the foundation is taken away and the preferred matrix of fish and forage is replaced by carp, followed by the crash of a once-thriving fishery.
The reproductive capability of carp can, within a short time after introduction, result in carp replacing the preferred fish, a phenomenon most evident in smaller water bodies.
If carp were to make their way into Devils Lake, the sheer size of the lake and inter-connected bodies of water would make chemical eradication virtually impossible even if enough money was available. That's why all the agencies and organizations involved realize that stopping the carp is a must.
A permanent dike to block transfer appears to be the most effective alternative in the long term. However, addressing the impact of backing up water and other tertiary issues will take some time. All involved understand the need for a short-term fix while work toward a long-term solution continues.
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For the interim, a rotenone drip, the same chemical used to eradicate fish from lakes without unintended consequences, will be put in place at the upper end of Snowflake Creek. It's a tributary to the Pembina River and the source of the carp that last summer threatened to cross into the Devils Lake watershed.
The treatment will take place from mid-May to July, after which a culvert connecting the two watersheds would be covered with a mesh screen, preventing fish movement throughout summer.
Historically, carp were introduced into North Dakota and other states as a possible new fishery and market, but the perceived benefits never realized. Modern day opponents to any introduction of non-native species point to the carp as a huge reminder of good intentions with bad consequences.
Stopping carp from migrating, being transferred or finding their way into new bodies of water is a high priority in North Dakota. Anglers can help by not dumping bait buckets in fishing waters. All it takes is a couple of undesirable fish hidden in with legal bait to adversely affect fish and the good angling you've come to expect.
Leier, a biologist for the North Dakota Game and Fish Department in West Fargo, can be reached at dleier@state.nd.us
