Plains Topminnow

I want to repeat a story here that I saw in the July 2012 edition of the Central Loess Hills Newsletter, Vol4 Issue1 (2) .  It is a story by a University of Nebraska-Kearney student, David Schumann.  No, it is not a story about some glamorous game fish that we like to catch, but it is a story about an interesting and colorful native species.  I am betting most Nebraskans do not know the first thing about plains topminnows, so hopefully you will learn something from this and develop a even greater appreciation for Nebraska fish and the habitats in which they are found.

Wildlife Spotlight—Plains Topminnow
David Schumann, University of Nebraska—Kearney

Sometimes things disappear so quietly that you don’t even notice.  Well right here in our backyard we have been slowly losing locations that support plains topminnow.  The plains topminnow is a small fish that lives in the small moving areas of our Nebraska streams and rivers.  In response, the Nebraska Game and Parks Commission along with the University of Nebraska at Kearney have been working hard to reestablish this species at the locations it was once known to exist.

A small stream in Nebraska colonized by plains topminnow.

The plains topminnow has a disjunct distribution with a small area centered in Missouri and a much larger population centered in Nebraska.  The geographic range of plains topminnow appears to be declining and it is recognized as a Tier one species of concern in Nebraska.  Recent sampling of 427 of the 618 known historic plains topminnow populations in Nebraska found the plains topminnow to be absent from more than 65% of sites.  Current plains topminnow locations in Nebraska are primarily found in the Loup, Elkhorn, and Dismal drainages, while the largest declines in plains topminnow populations are observed in the Platte and Republican drainages.  In total 9 states have recorded the presence of plains topminnow and over half of the historic sites have been found in Nebraska many of which were in the Central Loess region.

Plains topminnow are a fairly pretty fish designed to eat small invertebrates from the top of the water, which includes mosquitos.  A distinguishing characteristic is a golden strip along the back that can be observed as they swim.  Their maximum size is approximately 3 inches and they only live for 2-3 years.  If you want to look for them, look at backwater areas that connect to a larger body of water and have lots of vegetation, which they use to deposit their eggs on in the summer months.

Adult male (top) and female (bottom) plains topminnow captured in Nebraska.

Declining water quality, habitat degradation, and introduction of nonnative fishes have caused other stream fishes of the Great Plains to decline in distribution and abundance and are likely factors affecting plains topminnow.  The introduction and spread of western mosquitofish has been implicated in the reduction of plains topminnow populations as both fish commonly inhabit similar locations.  In the United States, mosquitofish have been introduced in 36 states beyond their native range. Western mosquitofish have caused declines to similar species through predation, competition, and stress.

Due to the observed declines of plains topminnow, a production pond for just this species has been established and seventeen Nebraska locations have been selected for reintroduction.  The principle goal of reintroductions is to establish viable, self-sustaining populations that require minimal long-term management at locations that have been locally extirpated.  Currently, some success has been observed.  If you have questions about this fish or this project you can contact Keith Koupal at the Kearney NGPC office.

I really do not have much to add, but this is my blog, you know I have to say a thing or two.

First of all, the story mentioned the golden strip along the backs of plains topminnows.  That really is an obvious characteristic; plains topminnows are usually hard to spot, they often are in and around vegetation or some other type of cover, but once you recognize that golden strip along their backs, you will suddenly start seeing them a lot better.

Secondly, the story mentions that western mosquitofish, Gambusia affinis, have been responsible for displacing plains topminnows from some of their native habitats.  Western mosquitofish are a species native to North America, but they are not native to Nebraska.  Unfortunately, because someone named them “mosquitofish” they have been widely transplanted around the world because, well, they are called “mosquitofish”, so they must eat mosquitoes!  The truth is there are a bunch of small fish, including young game fish, that will eat mosquito larvae.  Waters that have fish do NOT produce mosquitoes because fish eat mosquito larvae.  Stagnant waters where no fish are present are mosquito factories.  Mosquitofish have been introduced throughout Nebraska because folks believed they needed that species to help control mosquitoes.  Instead of introducing a nonnative species that has had detrimental impacts on our native species, the same thing could have been accomplished by transplanting some fathead minnows, bluegill fingerlings or even plains topminnows!  And folks likely would not have had to spend as much money to use those native fish for mosquito control as they did by purchasing mosquitofish.

And that is why I hope a blog post like this teaches you something you did not know before!