Tag: big fish

Weird Nature: Shrew-Eating Trout!

The story of rodent-eating trout at The Nature Conservancy’s Silver Creek Preserve has been one of our blog’s biggest hits. But those Silver Creek trout look like dainty eaters compared to this one. Meet the shrew-eating trout documented by researchers at Alaska’s Togiak National Wildlife Refuge. And how did this many small mammals end up in a trout’s stomach?

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Big Fish: Roadside Pike

Northern pike have always conjured images of wilderness: big, wild lakes, the scent of pine trees, a loon calling in the background.

Large, predatory fish, pike do indeed hunt lake shallows. They’re found in big places—from remote Alaskan and Canadian waters to the Great Lakes.

Come spring, they actually are on the move—traveling up rather small streams in order to spawn.

Researchers in Green Bay, Wisconsin have been tracking pike movements by doing chemical analyses of pike otoliths, also known as ear stones. Otoliths have annual growth rings, like trees, and accumulate trace chemicals from the surrounding water column as they form.

Many streams have a specific—and unique—combination of chemicals, and this chemical profile shows up in the otolith when fish move from one chemically distinct water body to another.

As such, researchers can determine where pike spent different years of their lives – and if they return to the streams where they were born, or if they use different streams.

This knowledge, in turn, helps conservationists focus on restoring streams that will actually be used by pike.

When I headed out with researchers, I imagined we’d search for pike in wild, lonely places. Instead, we immediately drove to an area across from a small, rural housing development, cars whizzing by as we checked pike traps.

Where could the pike possibly be?

It turns out: In a roadside ditch.

These little ditches— the kinds designed to keep water off the road—have been used for a very long time by pike as spawning sites.

With hundreds of lakes, streams and wetlands within miles of Green Bay, it may seem odd to focus on ditches. But those little channels may be vital in restoring pike populations.

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Big Fish: Return of the Alligator Gar

Once they were the river’s top predator: a fish that could reach ten feet or more, with thick armored plates as scales and imposing jagged teeth.

You would see their long, tooth snouts poking out from the river’s surface, gulping air—their adaptation for thriving in warm, deoxygenated water.

Alligator gar.

They thrived in a large swath of mid-western and southern waters, but by the early 1900s, they were already starting to disappear, a trend that continues to this day.

They were declared extinct in Illinois in 1994. But a new restoration and research effort aims to bring back these incredible fish, and help conservationists at other rivers and waters better protect them.

When fisheries biologists Rod Hilsabeck and Trent Thomas of the Illinois Department of Natural Resources decided to return the alligator gar to their state, they knew they needed a perfect location. The Nature Conservancy’s Spunky Bottoms Preserve fit everything they sought.

Formerly farmland, Spunky Bottoms is now 2000 acres of restored wetlands and uplands. It consisted of perfect gar habitat: backwaters and sluggish pools with lots of vegetation. It also was not connected to the adjacent Illinois River, making it easier for researchers to capture and study the fish.

Research is a key component to the reintroduction. Nathan Grider, a master’s student in biology at the University of Illinois-Springfield, is working with Dr. Michael Lemke and partners to study two key aspects of gar restoration.

They are studying how fast gar will grow when restocked into an area. They are also analyzing their diet, and in particular, if the gar will eat (and control) the non-native carp that swim Spunky Bottoms and so many other waters.

This information will help inform gar reintroduction and protection efforts throughout their range.

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Big Fish: Rodent-Eating Trout

As an avid fly fisher, I had heard the stories.

By day, the trout of Silver Creek—a clear, spring-fed stream in southern Idaho—fed on tiny mayflies and caddis flies. The water dimpled as trout sipped the profuse insect life from the surface. People like me used equally tiny artificial flies to try to  mimic said insects, often an exercise in extreme frustration.

By night, though, river monsters ruled: giant brown trout cruised the depths, occasionally surfacing to gulp down any hapless rodents that fell into the stream.

There’s something appealing, at least to an angler, about a trout that attacks mammals. Maybe it’s the thought of our favorite water transforming into a scene from Jaws.

Maybe it’s an antidote to the frustrations of tying delicate flies that practically require a microscope:  If I came back at night, I could just chuck a giant hairball!

But these mice-gulping trout always carried a strong whiff of, well, the classic fishing story. High on drama. Short on fact.

Silver Creek, after all, is one of the most-studied trout streams in the world. And there were no confirmed reports of trout dining on rodents.

Silver Creek also has one of the highest densities of aquatic invertebrates anywhere. The trout surely had easier prey than the occasional mouse.

Then biologists examined some brown trout stomachs.

What they found wasn’t pretty.

But it sure did validate some heretofore questionable fishing stories.

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Forest Dilemmas

Too many deer. Logging one tree to save another. Beavers versus old growth. Welcome to forest conservation in the 21st century. Join us for a provocative 5-part series exploring the full complexity facing forest conservation in the eastern United States.

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noun 1. Blog where Nature Conservancy scientists, science writers and external experts discuss and debate how conservation can meet the challenges of a 9 billion + planet.

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3. Home of Weird Nature, The Cooler, Quick Study, Traveling Naturalist and other amazing features.

Cool Green Science is managed by Matt Miller, the Conservancy's deputy director for science communications, and edited by Bob Lalasz, its director of science communications. Email us your feedback.

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