Biologist: Tropical Storm Irene may be looked at as a 'rejuvenating event' for trout
WILMINGTON — Fishermen could be enjoying the fruits of Tropical Storm Irene.
"Floods, such as occurred during Tropical Storm Irene, may be looked at as a rejuvenating event to which populations respond. Not only is trout habitat disturbed, habitat is created, and often time of higher quality and complexity than existed before," said Ken Cox, fisheries biologist at the Vermont Fish & Wildlife Department. "Sediments are purged from gravel substrates, improving trout spawning habitat and egg and fry survival. Old and new pools are scoured out, large boulders are shuffled around, and large wood is recruited to the stream creating abundant fish cover. And nutrients are released to the water, increasing biological productivity and food availability. Trout and other biota are adapted to these changes and in the long run, benefit by them."
Fly fisherman Steve Petrik, of West Dover, can catch naturally occurring trout again. This population had been lacking in the Deerfield Valley due to Irene, he said. The storm had flooded and devastated parts of Vermont on Aug. 28, 2011.
"Right after Irene, most of the habitat in the area was stripped down. The rivers were blown open a lot wider than they originally were so they ran a lot more shallow," said Petrik. "There was essentially no fish in a lot of the smaller tributaries like the branch on the Deerfield River and the smaller ones running down along Route 9."
Petrik said he can now go into mountain streams and pull out 6 to 8 inch brook trout. He's also seen some brook trout in beaver ponds connected to rivers and streams.
Cox said he did not have data that could show a direct conclusion about the storm's effects on the Deerfield River but he could speculate on its impact.
"Given that trout have been on the planet for many millions of years, they have experienced a multitude of catastrophic environmental events ranging from several glacial periods to local floods that have set back populations temporarily. No doubt, some species may have been extirpated over the ages but brook trout have managed to endure," he said. "In large part, their persistence is determined because critical habitat continued to be available to them and allow populations to reproduce and survive."
Cox said fish mortality and displacement had been affected by the flooding, which also disturbed fish habitat. Post-flood recovery activities — channel dredging or straightening, mining of bed materials, widening and berming — led to loss of habitat.
According to a Fish & Wildlife survey of selected watersheds affected by Irene, a minimum of 77 miles of streams experienced major habitat degradation from channel alterations.
"Streams that experienced the wrath of the flood but were not subjected to post-recovery activities maintained suitable habitats to allow populations to rebound quickly from losses incurred during the flood," said Cox. "In contrast, streams that were channelized, eliminating habitat/structural diversity and complexity, did not recover nearly as well."
Data on several streams affected by the storm showed that juvenile trout numbers increased over pre-flood numbers a year after Irene, he said.
"Because Tropical Storm Irene occurred in late summer before brown and brook trout spawn in the fall, and spawning habitat was 'rejuvenated,' trout populations that survived the flood had excellent conditions for reproduction which in turn benefitted population rebuilding," said Cox. "Two years following the flood, yearling (catchable-size) trout numbers were also up. "
Call Chris Mays at 802-254-2311, ext. 273.
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