Tiny ear bones inside golden shiners are poised to break open the investigation into how the bait fish were illegally introduced into Diamond Lake just two years after these waters were purged of another, more sinister invader.

Tiny ear bones inside golden shiners are poised to break open the investigation into how the bait fish were illegally introduced into Diamond Lake just two years after these waters were purged of another, more sinister invader.

Microscopic evidence in those bones could detail how old — to the day — those shiners were when they were killed by biologists worried the shiners' presence could erode the lake's renewed trout fishery.

The bones, called otoliths, can pinpoint exactly when they were released into the lake and how well they grew there. They can even finger the water-body they were swimming in before their release into this eastern Douglas County lake, which was poisoned in 2006 to cleanse it of millions of non-native tui chubs.

Comparing this evidence to other shiners captured in Southern Oregon, as well as others sold in Northern California bait shops as "minnows," could very easily and succinctly turn this shiner whodunit into the latest version of CSI-Outdoors.

"From the otolith, you can tell unequivocally where that fish came from," says Steven Campana, an otolith expert who heads a fisheries research lab in Nova Scotia, Canada. "There are all sorts of possibilities here, and it's an easy test to do."

Oregon State Police Trooper Jim Collom hopes otolith testing can jump-start his case, which is now stalled on unproven theories of how the shiners made it to Diamond Lake.

"It's unbelievable they can do all that from ear bones," Collom says.

All it takes is $4,000. But it's money Collom currently doesn't have.

He hopes someone can come up with the cash to do the sophisticated tests on enough samples to make those judgments.

The tests alone won't put Collom on the doorstep of whoever accidentally, or intentionally, threatened the lake's ecological future.

But it would at least suggest a scenario for how another non-native invader got in position to potentially undo the $5.6-million effort to restore the lake's legendary trout fishery.

"It might not necessarily give us a suspect, but we'll get a location, a source," Collom says. "And it will give us peace of mind that it happened one specific way and not other ways."

Peace of mind has been fleeting at the lake since July, when nets set to sample rainbow trout captured a dozen golden shiners.

Weeks of electro-shocking the lake turned up 640 shiners, all about 3 inches long.

Golden shiners are a small fish native to eastern North America. Widely popular as a bait fish, they are one of the most common fish farmed in the United States. But they are illegal to use or transport in Oregon.

Shiners were documented in the lake as early as 1981 and never overwhelmed the lake like the hundreds of millions of chubs did before the September 2006 treatment. So the environmental threat is not considered as great as that of the chub.

But it puts fisheries biologists on notice that their investment in Diamond Lake is as safe as a bank stock.

"It shows that people are not following the rules," says Laura Jackson, an Oregon Department of Fish and Wildlife biologist in Roseburg. "We hope history repeats itself and shiners never (overwhelm) the lake."

Still, it's a crime that Collom's charged with solving.

One running theory is that one or more people used them as bait, and dumped buckets full of them overboard after a day's angling, Collom says.

A second theory voiced by some lake users is that the shiners were introduced intentionally as an act of sabotage.

A third and least-likely alternative, Jackson says, is that a few shiners survived the rotenone treatment, then spawned to create the age-class of shiners captured this summer.

The answers lie within the otoliths, says Campana, at the Bedford Institute of Oceanography in Dartmouth, Nova Scotia.

The little bones, which are in most fishes, are important for balance, much like humans' inner ears. But these bones contain tree-like growth rings that speak volumes about their lives.

Otoliths grow constantly and are repositories for chemicals drawn from the water bodies where they live. Using laser beams and powerful microscopes, Campana and other experts can track such minutiae as daily changes in water temperatures and even the exact day they changed ecosystems.

"You could even tell if they were all introduced on the same day, and what that day was," Campana says. "If they get the right samples, they can do a suite of tests and get what they want."

Collom certainly wants to.

He's collected shiners from two known potential local sources — Howard Prairie Reservoir and Emigrant Lake. He's also collected samples from some of the roughly 60 Northern California bait shops that sell shiners legally as minnows there.

Luckily for Collom, all the shops get their shiners from the same Arkansas minnow farm.

Collom believes 40 tests at $100 apiece will put him on the right path for recreating his crime scene.

"We won't get a suspect from it," he says, "but we'll get a location and that piece of mind."

Otolith studies are rarely used in crime cases, Campana says, but he thinks otoliths are the way to go for Collom's investigation.

"Boy, they must really want to catch this guy," Campana says.

Reach reporter Mark Freeman at 776-4470, or e-mail mfreeman@mailtribune.com.