IMPRINT, the Bell Museum's quarterly magazine for members, offers stories of scientific adventure and discovery, insight into today's rapid environmental changes, updates on museum programs and exhibits, and fun activities for kids. IMPRINT is published quarterly and is available as a benefit of Bell Museum membership.

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by Jay Hatch

On a cool, sunny day in October, my good friend Konrad Schmidt called to tell me, "Well, looks like the Feds may list the Topeka within the next year or two. Maybe we should find out how many of these guys live in Minnesota sooner rather than later." That was in 1996 and Kon was talking about the Topeka shiner (Notropis topeka), a beautiful, 2.5-inch minnow whose abundance in Minnesota was considered rare at best. While collaborating on a scientific paper earlier in the year, Kon and I had talked of the need to find out more about the abundance and natural history of this interesting little fish. The time had come to do more than talk.

After two hours of diligent seining with nary a Topeka for the effort, I entertained the notion that Mound Creek might be added to the list of lost historic sites. Covered with a generous layer of topsoil gone aquatic, Susan and I broke for lunch but Kon kept working with his little one-person seine. Before I could devour the last of my apple, I saw Kon briskly advancing to the car, wearing a great grin. He had found Topekas—several adults—at the edges of the pools just below the dam.

Although not yet actively spawning, many of these fish showed signs of reproductive readiness. The males were impressively handsome and easy to identify with their combination of brilliant red-orange fins, coppery anterior body and head, and black chevron at the base of the tail fin. Tiny blue reproductive tubercles (presumably used in tactile stimulation of females) dotted their heads and snouts. The females showed just a tinge of yellow-orange in their fins, while their backs remained olive-yellow, their sides silvery and their bellies silvery white. The slight but clear distention of their bellies indicated the rapid yolk-loading process that was taking place inside. As we would subsequently discover, these females soon would spawn their first clutch of 100-500 eggs. If all went well, some fish might spawn three of these clutches before breeding ended in mid- to late July. We considered ourselves very lucky. We had found the rare Topeka shiner on our first try and were confident we could find others by sampling over rock and gravel at the edges of pools. Our confidence in identifying habitat and finding these animals rose exponentially over the next three years as we verified their presence at 22 of 34 historic sites and at 70 new sites in 35 different Missouri River basin streams. It began to look like Topeka shiners might not be as rare as we had thought.

With the help of a very observant and astute 11-year old local boy, we made an even more startling discovery: Topeka shiners were living and reproducing in off-channel pools and old oxbows in far greater numbers than they were in main channel habitats. We eventually learned that their abundance could be as much as 10 to 100 times higher in these off-channel areas. Yet such habitats often contained so much mud, silt and manure that we could barely wade through them.

I, for one, was quite perplexed by this discovery. Kansas biologists who had studied this species reported it “almost exclusively in quiet, open pools of small, clear streams that drain upland prairies.” The streams invariably had bottoms of “predominantly gravel, with some rubble and sand.” And Topekas were “not found in streams that [were] muddy and highly intermittent.” Missouri biologists indicated their populations were restricted to streams “having sufficient gradient to prevent extensive deposition of silt.” Yet here we were, sometimes up to our knees in silt, catching Topekas hand over fist. What was going on?

When it comes to fish observations, it’s rare to make a discovery that is wholly new. As I scrutinized more and more literature, I discovered that, in Nebraska and South Dakota, Topekas had been found in areas of high silt deposition. An 1896 paper reported them from “pond-like, isolated portions of streams which dry up in parts of their course during dry weather.” I was beginning to think we might be working with an ecologically very different fish here in the northern portion of its range. Then it occurred to me that I might be thinking about the problem in the wrong time frame.

Since the glaciers receded from the northern Great Plains (and probably before), fishes of small prairie streams have been adapting to the extremes of prairie aquatic life. During thousands of years, there must have been numerous episodes of drought when only the deepest pools maintained water. Fish might survive such droughts either by retreating downstream to larger rivers or by congregating in pools. Although soil erosion rates presumably were lower, these pools, especially those cut off from the mainstem in old channels and oxbows, must have accumulated considerable silt. Those that were not in contact with ground water also must have warmed considerably and may have reached fairly low dissolved oxygen levels. Fish that were stranded in these pools either were preadapted to such conditions or they died. It may be that over time (and this is mere speculation) ancestral Topeka shiner populations adapted to life in these pools. We also know from our own observations and from quantitative studies conducted by Luther Aadlund and his co-workers in the Department of Natural Resources that main-channel Topekas select the slowest current they can find.

So, what does all this speculation have to do with the current plight of the Topeka shiner? Here are the facts. Throughout their southern range, Topeka shiners are declining precipitously. Similar declines do not appear to be taking place in Minnesota. Water quality in both parts of the range has been degraded by nutrient and pesticide runoff, heavy sediment loading, highway construction and urban development, lowering of the water table, and construction of impoundments.

What appears to be different is the amount of off-channel habitat that exists in the Minnesota watersheds. They are plentiful in southwestern Minnesota and virtually absent in Kansas and Missouri. Our tentative hypothesis is that off-channel habitat is somehow crucial to the long-term survival of this species, possibly by providing a low-predator refuge during times of drought. Iowa biologists recently have added support to our hypothesis by finding Topeka shiners in watersheds of northwestern Iowa, where they are abundant in off-channel habitats and nearly absent from main channels.

The use of off-channel habitat may be an evolutionary adaptation—or it may be a more recent reaction to the declining instream habitat quality. It may be that the lack of off-channel habitat has sped up the decline of Topeka populations in Kansas and Missouri, where fish that can no longer survive in the main streams have nowhere else to turn. The decline of the Topeka shiner may just take a little longer in Minnesota. We don’t know. We do know that prairies and the streams that drain them have been altered so rapidly and to such an extent that few, if any, native species will be able to adapt to the changes.

On January 14, 1999, the Topeka shiner became Minnesota’s first federally endangered fish species. Despite its apparent abundance in our state, I can’t help but think of this fish as another miner’s canary. Like the suffocating canary, Topeka shiners, deformed frogs, disappearing mussels, and a host of other creatures are warning us that disaster is close at hand. We need to carefully re-evaluate our place in nature, and we need to hear the truth in the words spoken by Chief Seattle 150 years ago when the white man negotiated to buy his people’s land. “This we know: All things are connected like the blood that unites us. We did not weave the web of life. We are merely a strand in it. Whatever we do to the web, we do to ourselves.” He admonished the white man to “preserve the land and the air and the rivers for your children’s children and love it as we have loved it.” If we grasp this truth and allow our actions to follow from it, the Topeka shiner will still be in Kansas to celebrate the 200 th anniversary of its discovery, and our children’s children will still be part of the web of life.