Wildlife Watch: Brook trout survey

Published: Aug. 6, 2019 at 4:37 PM EDT
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Brook trout are one of the many fish that fill local streams and creeks and are a nice catch for anglers. But for scientists, catching the fish can provides not only information on the health of the species, but important clues about the health of ecosystem.

In the middle of the woods near the Groton State Forest, Vermont Fish and Wildlife biologist Bret Ladago and his crew are gearing catch some trout, part of a five year annual survey in this spot.

"This is a stretch of stream that's in the Waits River -- it's in the headwaters of the Waits," Ladago said. "This was originally sampled by the department back in the '50s, so this is a historic station that we come to periodically to look at the health of the trout population to see how it's changed over the years.

To check the fish they will need to collect them. To make it easier, Ladago shocks the fish so he can scoop them up. "We create sort of an electric circuit within the stream where we have the generator that's attached to a negative and we hold on to a wand which is the positive part of where the energy comes out. So, when those fish come in contact with the positive energy they are stung briefly so we can catch them in a net and then a bucket. as soon as they are removed from that electrical field they come out -- they are fine, and it's a really good way for us to sample fish without having to kill them," Ladago said.

He says after being shocked the fish are fine. "They respond really quickly. Studies show they may only skip a meal or something once they get electrocuted, but they pretty much go back to normal behavior not too long after we put them back," Ladago said.

Surveying up the stream, more and more fish find their way into the bucket. After a few hundred feet, the crew gets back to the truck to measure and weigh the trout.

"That will give us a little more information so we can compare them to other populations, and it will tell us if this is a healthy population or maybe there is something wrong here that we need to look at," Ladago said. "Not only does it provide that sort of historic context, where we are looking at populations through time, but it is also a really good environmental indicator. If we have good healthy brook trout populations, that tells us a lot about the surrounding ecosystem. And if we find this for years, then it's likely we are doing things to keep the surrounding ecosystem going healthy, so it really can tell us a lot not just about the brook trout but about all the surrounding animals."

Reporter Ike Bendavid: I know you had a quick look but healthy population?

Bret Ladago: Yeah, definitely. Multiple year classes, so you're getting ones that are not only born this past year but ones that have been here. A brook trout life expectancy is about five years. It's a tough place to make your living, especially in the wintertime or during floods, so they get to be about five years-old, and a five-year old brook trout may only be six inches or so. We probably caught about 30 to 40 fish that were six inches, so it's a good sign things look good up here.

The trout get put back into the water as the crews go to collect more fish. Ladago says a healthy population of wild trout means good fishing in the future. "These fish are going to grow a little too big for this several inches of water," he said.

Reporter Ike Bendavid: Where can I go fishing to find these in a few years?

Bret Ladago: Usually when fish get too big for the water that they are at they tend to move down stream, so we're at the head waters of the Waits River, so really all the way down till the water gets a little too warm for brook trout.