Study looks at fish recovery after forest fires

Study looks at fish recovery after forest fires

17 January 2012

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USA — Destruction seems to dominate in the wake of forest fires, but with time the restorative power of fire in the Intermountain West is revealed.

On Thursday, fisheries biologist Michael Jakober will present yet one more scientific study showing that not only does nature bounce back after a wildfire but it can return to a better state. In this case, the animals doing the bouncing are trout.

Jakober’s talk, “Fish and fires: You can burn us but we’ll be back,” uses more than a decade’s worth of data to show that some trout have come back stronger than ever in streams of areas that were blackened by the fires of 2000.

The streams in Jakober’s study are all on Forest Service land so he doesn’t have to consider the added stream degradation that can accompany civilization. So the main detrimental effect on the fish in his 20 streams was due to fire.

Not surprisingly, fish did suffer immediately following the fires. But in the subsequent decade, a number of habitat changes emerged that resulted in the growth of healthy trout populations.

“The stream areas became a lot more complex in the moderate- and severely-burned areas,” Jakober said. “Now there’s tons of large woody material in the streams that cause the scouring of pools. You really notice it if you go out and try to walk it.”

Jakober said the new shrubs and small trees along the stream banks add high-quality cover and nutrients for fish. Fingerlings and small fish are dependant on such hiding places for survival.

The severely-burned areas showed the only slight drawback of fire: The complete loss of large trees allows streams to heat up a little more than those with better shade.

“The shade from streamside vegetation is not as effective,” Jakober said. “We see greater water temperature increases than in other streams but not that much.”

Higher water temperature may be enough to affect bull trout, a species specialized for cold mountain streams, but Jakober said he didn’t find enough bull trout to know. Bull trout populations have always been low to nonexistent in his study streams, even before the fires, so he can’t draw any conclusion about their resilience. Non-native brook trout are also fortunately rare.

But westslope cutthroat populations are thriving, Jakober said. Part of that is because they’re native – they evolved ways to survive locally as a species.

“They’re adapted to fire,” he said.

The 1988 fires in Yellowstone National Park prompted several studies that reached the same conclusions: fires clear out areas choked by half a century of fire suppression and allow for recovery to a healthy natural system.

The Forest Service got a good start on the post-fire research when Montana State University graduate student Clint Sestrich conducted a three-year study of the Bitterroot streams and their inhabitants starting in 2001. Sestrich’s results were published last year in the scientific journal, “Transactions of the American Fisheries Society.”

“He left us a good strong dataset,” Jakober said. “Since then, we’ve been monitoring a subset of those streams. We try to hit each one at least every five years.”

Jakober plans to continue monitoring for at least another 50 years, if not 100, because that’s how long it could take for the severely-burned areas to fully recover.

“They may never return completely because there’s so many variables,” Jakober said. “And now with climate change, it’s hard to say.”

Michael Jakober will speak Thursday at 7 p.m. at the Hamilton Elks Lodge, 203 State St., sponsored by Bitterroot Trout Unlimited.

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