By Alex Breitler, Record Staff Writer

April 04, 2010

STOCKTON – The murky Calaveras River doesn’t easily give up its secrets.

But with the help of new high-frequency sonar equipment, biologists are getting their best look yet at the many fish species that swim unseen in the channel that slices right through north Stockton.

This isn’t like the sonar on any old fishing boat. The new machine peers right through dense silt and sediment, spotting a fish as small as 11 inches from 40 feet away and producing a fairly clear videolike image.

That’s impressive when you consider visibility in the Calaveras River on Saturday was about 2 feet.

“I’ve snorkeled this (river) and you can’t see much. To get some eyes underwater is great,” said Kari Burr, a biologist with the Fisheries Foundation of California, which monitors fish populations on the Calaveras and other streams.

University of the Pacific biology Professor Stacy Luthy got the equipment late last year and has been testing it out with Pacific senior Phillip Poirier, a Lincoln High School graduate and aspiring marine biologist…

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