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Research provides insight into lake trout

ALPENA — New research published in the Fisheries Research journal has shed light into lake trout and its spawning habitat preferences in Thunder Bay. The new data could have a larger implications for other aquatic life.

In 2010 and 2011 Dr. Ellen Marsden from the University of Vermont, with the collaboration of state and federal conservation agencies, constructed 29 reefs in Thunder Bay to monitor the spawning habits of lake trout over a five year period.

According to the research, the lake trout did not frequent or spawn on the reefs initially. Over the course of the next five years, however, the trout began showing up more often.

“The objective of the study was ‘could we put some reefs in the lake for the lake trout,'” Marsden said. “The answer was absolutely yes. It took the course of two, three years to discover them and put eggs on them.”

Marsden paid tribute to the state and federal agencies that contributed to the project, including the DNR, Thunder Bay National Marine Sanctuary, U.S. Fish and Wildlife Service and other institutions and universities such as Michigan State University.

“It was a delight working on the project,” she said. “You always get to work with colleagues and groups but what a truly compatible group it was. It would not have been possible otherwise.”

Researchers constructed 29 reefs from donated quarry rocks from Lafarge that ranged in size from a clinched fist to a small soccer ball, she said. The size was predicated on the getting rock which could make crevices for eggs to get into to be protected from outside factors.

The reefs were placed next to the natural east reef in the bay allowing researchers to use acoustic telemetry technology to track the tagged fish’s movements.

One of the unexpected parts of the research was the discovery of Volkswagen-sized boulders in the bay that were previously unknown, Marsden said. She said while agencies such as the National Oceanic Atmospheric Administration and the sanctuary have scanned large swaths of the bay these large rock formations were unknown.

“We blundered across these rocks when we were diving, massive piles of rock,” she said. “The historians said they were from dredging and breaking up the harbor.”

Marsden said the rocks also could have come from the logging era when rocks were used as anchors for logs when the Thunder Bay River was backed up. She said when the river got choked up loggers would use the bay as a staging area. But she was hesitant to make any definitive conclusions due to the extreme size of the rocks.

After the reefs was constructed researchers monitored the tagged fish’s movements for a five year duration to observe their movements and spawning habits. Over the course of the study the number of fish that visited the constructed reeds increased every year.

Marsden said how the study was done could allow other similar studies to replicate it, as well as expanded it to other aquatic life such as bass, walleye and whitefish.

She also said this could be beneficial to areas where there have been reductions in the number or quality of essential habitats.

The study concluded lake trout preferred larger reefs over smaller ones, lake trout were more likely to frequent reefs adjacent to natural spawning sites and clustered reefs attract more fish than isolated ones.

“It worked,” she said referring to the reefs. “They were reproducing there and they were living there.”

Tyler Winowiecki can be reached via email at twinowiecki@thealpenanews.com or by phone at 358-5688. Follow Tyler on Twitter tw_alpenanews. Read his blog, Just a Thought … at www.thealpenanews.com.

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