Radio Script
2000

 

 
Sheefish Lend an Ear to Science
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INTRO: If you want to know where a fish has been, a good place to start is with a look inside the fish's ear. As strange as it sounds, fish do have ears, or more precisely, ear bones. They're called otoliths (oat-oh-liths). They help fish sense vibrations and movement in the water, and now they're helping scientists understand fish migrations. Arctic Science Journeys Radio producer Doug Schneider has more.

STORY: You might say Randy Brown has an ear for fish. As a fisheries biologist with the U.S. Fish and Wildlife Service in Fairbanks, Alaska, Brown studies otoliths--those are the ear bones of fish--to learn the migration habits of sheefish. Sheefish are a large predatory fish that live in the waters of northern Canada, Alaska and Russia.

BROWN: "An otolith is the ear bone within the fish. They sit near the fish's brain and over time they get bigger and bigger through crystallization of calcium carbonate. The calcium leaves rings, similar to rings on a tree. So you actually have time lines left within the otolith. When this otolith is cut in a particular way--with a technique called thin sectioning--you can actually examine it with a microscope and count the rings and determine how old the fish is. And then with the microchemistry you can examine material within rings and determine whether or not the fish has been to salt water."

Besides calcium carbonate, otoliths pick up traces of other substances found in the water. One in particular is strontium, an element commonly found in salt water. By measuring the location and concentration of strontium within the otolith, Brown can tell when the sheefish left fresh water for salt water. Knowing how long the fish stayed in salt water helps Brown understand the life history of sheefish.

BROWN: "The beauty of this technique is you don't need to follow the fish anywhere. You catch the fish at a location and take the otolith and examine it and you essentially can describe its life history. Year one, did it go to sea or not. Year two, did it go to sea or not. Did it move back and forth between marine waters and fresh waters. And so you can do this throughout the fish's life."

From his studies, Brown learned that adult sheefish migrate up Alaska's Yukon River each spring, a distance of some 1,200 miles. Brown also learned that young sheefish tend to live erratic lives, moving often between salt water and fresh water to find food.

BROWN: "Initially when I went in to study sheefish I was looking to see whether or not they were anadromous, in other words whether they had gone to the ocean and back. And what I was actually able to discover with this technique is their pattern of movement on a year-to-year basis. They make distinct moves back and forth between salt water and fresh water. There's a lot of individual variation."

Sheefish are members of the salmonid family, to which belong salmon. But unlike salmon, which swim upstream as adults to spawn and die, sheefish spawn and return to the sea many times during their life span.

OUTRO: This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program and the University of Alaska Fairbanks. I'm Doug Schneider.

Thanks to the following individual for help in preparing this script:

Randy Brown
U.S. Fish and Wildlife Service
12th Ave. Federal Building
Fairbanks, Alaska 99701
907-456-0295
Randy_J_Brown@fws.gov

For more information about whitefish check out these web sites:

http://www.state.ak.us/adfg/notebook/fish/sheefish.htm

http://www.alaskaoutdoorjournal.com/Departments/Halloffame/fame.html