They are small – so small, in fact, that the water in the creek where they live in most places isn’t ankle-high. Most people couldn’t spot a fathead minnow in Mint Springs Creek, trickling through Vicksburg National Military Park, if they were looking.

But as far as the rest of life in the creek is concerned, said aquatic ecologist Eric Dibble, the tiny bait fish are something of an unstoppable menace.

&#8220It’s highly probable” the fathead minnow is responsible for the elimination of every other fish species above the larger of the creek’s two waterfalls, said Dibble, a Mississippi State University professor who has spent 11 years studying aquatic life in the park for the National Park Service.

&#8220I started the study in 1995, and there hadn’t been any surveys prior to that,” Dibble said. &#8220We don’t have any historical records, but it’s likely that fish were there prior to my research just because it’s good habitat. It’s highly plausible.”

All this month, the environmental assessment of the park’s plan to eradicate the fish is available for review at the park’s visitor center desk and online. The purpose of the assessment, mandated by the National Environmental Policy Act, is to &#8220examine different alternatives for achieving the park’s goal of eradication this non-native and invasive fish species from the upper portion of the stream.”

Mint Springs Creek runs through the northwest corner of the park, near the Vicksburg National Cemetery, and crosses beneath a short bridge on Fort Hill Drive, where – to those willing to brave the foliage and steep descent, it is open to the public, said Kurt Foote, natural resource program manager at the park.

The creek’s first, smaller set of falls is just north of the bridge. About a half mile to the south, a larger set of falls serves as the cutoff for the fathead; south of the larger falls is a variety of fish species, some of them much larger, but no fathead minnows.

About 28 to 30 species are there regularly, including stone trout, darters, sunfish, largemouth bass, Mississippi silvery minnows and other types of minnows, all of them native to Mint Springs Creek, Dibble said.

&#8220It has served as sort of a nursery periodically for fish coming up from the (Mississippi) river,” he said.

The fathead minnow, typically used for bait, was most likely introduced upstream by fishermen, Dibble said, though there’s no way to know for certain. The fathead’s range extends south from Illinois, and although they are native to a few places in Mississippi, he said, they are not native to Vicksburg.

&#8220Mint Springs has some tributaries that come from outside of the park, but it’s feasible it could have been introduced inside or outside of the park,” Dibble said.

If the fathead is killing other species, it’s unclear exactly how, said Jim Long, a Park Service biologist in Atlanta who helped put together the Vicksburg park’s eradication plans and secured $2,000 in grant money for the $9,000 project. It could be by predation – actually eating other species, especially of the young – or, more likely, it’s simply won the battle for limited resources over native fish.

&#8220When a non-native species comes in, the native species tends not to have any idea how to deal with it, so the community has no evolutionary mechanism to keep it in check,” Long said. &#8220Which is why we get concerned with people dumping things where they don’t belong.”

Dibble compared the situation to similar problems nationwide caused by the introduction of rainbow trout to streams where native trout species can’t compete, and eventually dwindle and die out.

To combat the fathead, Long said the plan called for a fish-specific poison, Antimycin, to be dumped into the river above the larger falls, where it would kill the minnows. Although that will dissipate on its own, he said, another chemical will be added to the stream near the falls to neutralize the poison and prevent it from flowing into the ranges of the downcreek species.

&#8220It’s kind of killing two birds with one stone,” Foote said. &#8220On the nature side, we’re getting rid of a non-native species. On the culture side, we’re restoring the battlefield to its condition during the Civil War, because there were definitely no fathead minnows here then.”

TO VIEW PLAN.

Anyone interested in viewing the environmental assessment of National Park Service’s proposal for eradication of the fathead minnow from the upper part of Mint Springs Creek in Vicksburg National Military Park may do so through Oct. 1. A 30-day review period, which began Friday, is mandated by the National Environmental Policy Act.

Copies of the assessment are available online at http://parkplan-ning.nps.gov, where visitors can read and comment on the plan. Copies may also be obtained by calling 601-619-0583 during regular business hours, sending an e-mail to Vick_Interpretation@nps.gov or writing to Vicksburg National Military Park, Attn: Invasive Fish Species Eradication-EA, 3201 Clay St., Vicksburg, MS 39183-39495.