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Entries in Rotenone (2)


A Carp Is Not Just a Carp; Here's the Difference

Many people, including anglers, don't understand that we have several kinds of carp now swimming in our waters, all of them fish from other countries. And all of them problematic in one way or another.

The fish in the top photo is a common carp. It was introduced more than a century ago, with the help of the federal government. It's now in lakes and rivers all over this country, and has degraded water quality in many of them, mostly because it roots on the bottom and stirs up sediment.  State agencies sometimes use a rotenone treatment to wipe out a lake's fishery, primarily because of overpopulation by common carp. When someone says "carp," this is the fish that most people think of.

Grass carp (that's me with an illegally stocked grass carp) were first introduced during the 1960s, to help control aquatic vegetation, mostly exotic milfoil and hydrilla. The problem is that they eat ALL plants, including beneficial native vegetation. Some have escaped and are reproducing in our rivers. More recently, there's concern that they might establish a breeding population in the Great Lakes. They're far too easy to purchase and stock illegally by people who have no idea of the problems that they cause.

Finally, Asian carp. That description applies to both silver (top) and bighead carp. The silver carp is the one that you see so many photos of as it flies through the air. Both are growing larger here than in their native habitat, with bigheads now exceeding 100 pounds. These are the most recent introductions, brought in by fish farmers in the South. They escaped and now are outcompeting native fish for food and habitat in many of our major rivers, most notably, the Missouri, Mississippi, Illinois, and Ohio. In some places, they account for more than 95 percent of the biomass. There's concern that they, too, will establish breeding populations in the Great Lakes.


'Bio Bullets' Could Help Control Asian Carp

Dumped into a lake, Rotenone will kill all fish indiscriminately.

Properly packaged and selectively presented, though, it could be the key ingredient in an “oral delivery mechanism” that will help control bighead and silver carp.

In other words, within a couple of years, a “poison pill” might be available to knock back populations of these Asian invaders.

But Jon Amberg, a biologist with the U.S. Geological Survey (USGS) here, prefers not to use such terms when talking about research to develop bio bullets for invasive species.

“It’s not really a pill at all,” he said. “It’s a micro particle, about the size of a grain of flour, with a lot of different components. And it’s not a ‘poison’ either. Anything can be toxic at the right dosage, even water.”

Rotenone, however, is a piscicide, a substance toxic to fish, as is Antimycin. Amberg and his colleagues are looking at both as the possible lethal component in bio bullets for silver and bighead carp.

“We could use pathogens specific to carp or we could do something to affect reproduction,” he explained. “We’re exploring a lot of things. But right now, for the initial phase, we want something like Rotenone that will produce a measurable effect.”

This summer, USGS scientists are testing the “next generation” of micro particles in the laboratory to determine their toxicity for both Asian carp and non-target species. “Maybe in a couple of years, we can have control trials in the fields,” Amberg said.

By using micro particles, researchers hope that they can exploit how the carp feed --- by filtering the water. “Some native fish filter feed also, especially in their larval stages,” Amberg said. “So we wouldn’t want to use it when larval fish are present.”

Theoretically, carp would ingest the particles, which would encounter “a certain enzyme” in their digestive systems. Triggered by the enzyme, the particles would break apart and deliver the payload.

Fish that don’t eat a sufficient number of particles would not be harmed, meaning most species, including predatory sport fish, would not be affected.

The biologist readily admits, however, that this work must “walk a fine line” in coming up with a control agent that will kill only Asian carp. Gizzard shad, buffalo, and paddlefish also filter feed.

“This research is very much in its infancy,” he said. “We’re not going to just start putting toxic soup into the environment. We want to minimize the impact and target the delivery.”

(This article appeared originally in B.A.S.S. Times.)

Here's another article about Asian carp and bio bullets.