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ENVIRONMENT Invasive species tui chub discovered at Diamond Lake Comment By Mark Freeman Mail Tribune MailTribune.com By Mark Freeman Mail Tribune Posted Nov. 4, 2015 at 2:45 PM Updated Nov 4, 2015 at 4:39 PM By Mark Freeman Mail Tribune Posted Nov. 4, 2015 at 2:45 PM Updated Nov 4, 2015 at 4:39 PM » Social News Tui chub have returned to Diamond Lake and threaten its popular trout fishery nine years after a $5.6 million eradication program cleansed it of the non-native invader after its numbers approached 100 million. Gill nets set last month as part of a trout-monitoring program at the eastern Douglas County lake captured a single chub, according to the Oregon Department of Fish and Wildlife. The 7 1/2-inch fish was positively identified at an Oregon State University lab, which estimated that the fish likely was 6 years old. Biologists suspect it was illegally introduced into the lake either as a "minnow" bait fish or was intentionally placed there, shocking and saddening agency biologists and lake lovers who worked so hard to reclaim the lake by poisoning the chub in 2006. "I think everybody's shocked and surprised," ODFW spokeswoman Meghan Dugan said. "It was just nine years ago that we treated the lake." But other data seems to indicate that whatever chub are present in the lake have not done any environmental damage as they have in past infestations. Monitoring shows that Diamond Lake’s bustling insect population and zooplankton composition have remained healthy. Trout monitoring shows the stocked fish are healthy and indicate an abundant food supply, records show. "I think it's fair to say we're in the early phase here of identifying what the effects will be," said Jason Wilcox, a fish biologist for the Umpqua National Forest. In the early '90s it took tui chub only a few years from initial discovery to altering the lake's ecosystem. "I think it's possible we'll see a similar roll out" of impacts again, Wilcox said. "But it's still in the wait-and-see-and-monitor stage right now," he said. ODFW and the Umpqua Forest will be joined by Douglas County and Oregon Department of Environmental Quality to develop an action plan for next year and beyond, Wilcox said. That likely will include stepped-up monitoring and tracking for additional chub. If more chub are located, biologists could intentionally disrupt chub spawning and alter the lake's trout-stocking regimen — all repeats of past attempts to rid the lake of chub without having to poison out all of the lake's fish. "We're definitely not starting from a clean slate," Wilcox said. "I think we learned a lot over the years, recognizing it's a complex ecosystem." The chub, which are native to the nearby Klamath River Basin, were discovered in similar fall gillnetting in 1992, records show. Within two years their population exploded enough to start out-competing stocked trout for food and space. The following decade, the chub population was estimated at more than 90 million, altering the lake's ecosystem to create toxic algae blooms that damaged water quality. Since the 2006 rotenone treatment that killed off all the fish in the lake, the ODFW has aggressively stocked strains of fish-eating rainbow trout in case the non-native fish returned. In 2008, non-native shiners were captured in the lake. Each year since, the ODFW has conducted some of the same anti-chub measures that have kept shiner populations from damaging the lake or its trout fishery. The lake's first taste of tui chub came when they were discovered there in 1946, and state biologists tried several eradication methods before relying on rotenone to sweep the lake clean of all fish in 1954. Diamond Lake is a naturally fishless lake that has been stocked with trout for anglers since the early 20th century. Reach reporter Mark Freeman at 541-776-4470 or [email protected] . Follow him at www.twitter.com/MTwriterFreeman . By Mark Freeman Mail Tribune MailTribune.com By Mark Freeman Mail Tribune Posted Nov. 4, 2015 at 2:45 PM Updated Nov 4, 2015 at 4:39 PM » Comment or view comments Reader Reaction » STAY INFORMED Email NewsLetter Sign Up Today Sign up for our newsletter and have the top headlines from your community delivered right to your inbox. Southern Oregon Directory Featured Businesses Loading... 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