One of my favorite techniques for fish collection is using our fish weir. Iâ€™d like to say it was a new idea, but Roger AuClair, the first regional fisheries biologist in the Moosehead Lake area, built a wooden weir on Socatean Stream in 1957-58. It was our desire to duplicate his work some 50 years later that led to the design and fabrication of our new steel picket weir.
One of my favorite techniques for fish collection is using our fish weir. Iâ€™d like to say it was a new idea, but Roger AuClair, the first regional fisheries biologist in the Moosehead Lake area, built a wooden weir on Socatean Stream in 1957-58. It was our desire to duplicate his work some 50 years later that led to the design and fabrication of our new steel picket weir. My assistant, Jeff Bagley, designed the weir and coordinated the construction. In 2009, we used the weir on Socatean Stream. We moved over to the Roach River in 2010 and again in 2011.
The weir is very portable. We can set it up anywhere that has a solid stream bottom and where we can get an ATV to the shore. Itâ€™s like a giant erector set. We essentially build a steel fence across the stream/river that fish cannot pass through. The fish bump along the fence until they find the collection box. This box has a fyke or funnel at the mouth that looks very much like the entrance to a minnow trap. Once the fish swim in, they usually canâ€™t find their way back out.
Weâ€™ve had a few complaints from anglers over the years that we are stopping the fish from going up the Roach River. Not true! Some felt there would be no fish in the river until we pulled the weir out. Not true again! Hereâ€™s what really happens. We know from radio telemetry and other tagging studies that nearly all of the fish move upstream after sunset and before dawn. They move at night. We tend the weir each morning when there are a lot of fishing moving. When we tend the weir, we put the fish upstream and they are free to go on their way. So, we are holding them for a few hours, at night, then they continue with their migration. There have been times when only a few fish are moving or over a weekend when we tend every other day. But for the most part, these fish have a brief encounter at our aquatic toll booth.
We set the weir in the Roach River in 2018 primarily to get a comparison with data collected in 2010 and 2011. We also wanted to see if some of those monster brook trout that we saw on the lake in 2018 were using the Roach River for spawning. We did not see any fish this big the first two times we set the weir in the river.
We set up the weir in late August but left it open until after Labor Day. The weather turned off hot that week and we only put up six fish. Early the next week, the weather turned cooler with some rain, and we bumped up the flow at the dam. The catch improved but that weekend the temperatures were pushing 80 degrees, so we opened up the weir and let the fish pass through. Holding brook trout or salmon in a confined space in hot weather would probably be lethal. We donâ€™t know how many fish passed upstream during this period, but any effort to get a total count of the run of fish was over for the year. We would just have to compare catch rates during the periods when the weir was operational. So, we focused on getting a good sample of both salmon and brook trout. By Sept 28, we had our sample and we removed large sections of the weir to allow free passage for the fish again.
What did we learn? Even though 2018 was a record year for big brook trout in Moosehead Lake, we did not see any of those fish in the weir. Those 4- to 7-pound brookies are spawning somewhere else or coming in much later than normal. We did see a lot of nice trout, however. In 2010 and 2011, around 20 percent of the trout in the weir exceeded 16 inches. This year that figure was 56 percent. We saw a similar trend for salmon. We documented 20-25 percent of the salmon over 18 inches the first two years of operation and this year it was over 50 percent. The fish were also much fatter in 2018 than the earlier studies. So, there was a substantial improvement in overall size quality for both species.
Even though we didnâ€™t get â€˜em all, we did find the average catch of brook trout per hour was higher than the previous studies and the catch rate for salmon was unchanged.
To wrap it all up, our wild brook trout and salmon have improved in growth since 2010-11. We are also seeing a resurgence in brook trout abundance in the lake and river. We handled a lot of trout between 16-18 inches in the weir this year. These improvements are the result of the removal of the over-abundant lake trout from the lake starting in 2008. After the lake trout were thinned down, the smelt population rebounded nicely providing more food for the gamefish. This created bigger, fatter fish and actually improved survival, so there are more fish as well. The fish in the Roach River were impressive this fall and all signs point toward a good year for anglers in 2019.