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Fly-Fishing: Irene seems to have had good effect on brown trout

Thursday, July 25, 2013
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Trout routinely survive floods, but the flooding from Tropical Storm Irene in 2011 was anything but routine.

Esopus Creek in the Catskills got the most rain, 11.5 inches, and swelled overnight from a fairly typical 450 cubic feet per second to 80,000 cfs, the largest volume ever recorded on the creek. The muddy torrent destroyed homes, roads and bridges. It was hard to imagine that trout and the insects they eat would escape being severely impacted.

Because the Esopus is a key part of the New York City water supply, it gets watched pretty closely, and multi-agency studies of its flows and erosion problems were already under way when Irene struck. The studies are ongoing and the results are not final, but researchers have made some interesting informal observations.

Far from wiping out the trout of the Esopus, Irene seems to have greatly improved reproduction of brown trout, said Scott George of Delmar, who’s studying ecology and evolutionary biology at the University at Albany. George was a member of a crew counting fish this week on Stony Clove Creek, a tributary of the Esopus.

The late August storm deepened channels and scoured gravel, creating ideal conditions for brown trout to lay eggs two months later.

“The adults that survived Irene and spawned that fall had a banner class,” George said, pausing from his job of netting fish temporarily stunned by U.S. Geological Survey biologist Barry Baldigo’s backpack electro-fisher. “We think it was potentially due to improved stream habitat.”

The brown trout benefited from lucky timing. Had a flood of the same magnitude happened in November, after the browns had spawned and deposited their eggs, the effect could have been catastrophic.

“Floods that occur when the eggs are in the gravel are the ones that can wipe out a year-class,” George said.

Of course, the Esopus is famed for its rainbow trout, not browns. The creek has had a thriving pop­ulation of rainbows since the Calif­ornia transplants were first stocked in 1884. These days, rainbows aren’t stocked in the Esopus at all.

But the timing that benefited the brown trout seems to have had the opposite effect on rainbows. Because brown trout hatch first, by the time the rainbows hatched out in spring 2012, the creek was already full of young browns, which won the inter-species competition for survival.

That came as no surprise to the scientists.

“It’s very well documented that when brown trout have a good spawning season, the rainbows will suffer,” George said.

Rainbows still outnumber browns on the Esopus, and one weak rainbow year-class isn’t likely to change that. But it’s nice to have more wild browns in the stream.

Along with the impact of Irene, agencies including U.S.G.S., the Department of Environmental Conservation and the New York City Department of Environmental Protection have been studying a longstanding problem on the Esopus, from the standpoint of drinking water supply as well as trout fishing: erosion and muddy water.

The Esopus’ tributaries often add turbid water to the creek. Stony Clove Creek, where George and the rest of the crew were counting fish this week, has always been one of the worst offenders. Last year, the DEP and other agencies reinforced one of the chronic erosion spots on Stony Clove. At the end of July, work will begin on a more ambitious project, a tall, eroding bank engineers have dubbed the “Bowl of Doom” on the creek in Chichester, a mile upstream of where the Stony Clove meets the Esopus in Phoenicia.

These efforts should make the Esopus clearer, more enjoyable to fish and presumably fewer headaches for New York City’s water supply managers. But the tributary that was polluting the Esopus with mud (again) this week was man-made: the city’s own Shandaken Tunnel, a pipeline that carries water from Schoharie Reservoir to the Esopus, which then serves as an aqueduct, carrying the water closer to its final destination.

The Schoharie water has always helped keep the Esopus full and cool in the summer, which benefits the creek’s trout. But it’s also chronically turbid — so much that a federal court found the city guilty of violating the Clean Water Act a decade ago. The city now has a permit, but the mud pollution continues.

The steep, temperamental Esopus watershed continues to pose challenges, for people and for trout.

 
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