Invasives

Pennsylvania Wild Brown Trout

Pennsylvania has had brown trout stocked since 1886. In historic literature, it’s well documented that several of the limestone streams in the Cumberland valley of Pennsylvania has massive stocks of brook trout. The early sport anglers of the day longed for the Loch Leven and German brown trout of their homelands, and so, many streams were “converted” from brook trout streams to brown trout streams.

The imported brown trout took well to the limestone streams of the area and grew large. The success led to stocking by the state in many additional freestone streams throughout the commonwealth. At the time, the state was wrestling with the effects of large scale logging and pollution. The focus was providing trout as a source of food and for sport angling to replace the stocks of native brook trout that had been displaced due to habitat loss.

Numerous studies have proven that brown trout are prolific breeders, and very effective in taking over waterways. This study for example, is a very good explanation of the entire brown trout situation in the United States. There has also been research into the effects of brown trout specifically as it relates to native brook trout. This article outlines how continued stocking and the presence of brown trout negatively impacts brook trout populations.

It has been an eye opener for me personally watching a stream near me transition from a “mostly brook trout” waterway, to a “mostly brown trout” waterway. About 25 years ago a friend of mine introduced me to this stream. His description of the stream was; “it’s mostly wild brookies, but there are some wild browns too”. I recall at the time thinking this was great! Wild browns were something we ran into occasionally at the time, and it was interesting to think of a stream that was mostly wild brook trout with occasional wild browns mixed in.

This stream is stocked in it’s lower section and has been for a long time. Over the years it has been the focus of stream improvement projects by both the local Trout Unlimited chapter and the state fish and boat commission. Numerous jack dams were constructed along it’s upper reaches to improve the stream channel depth and to narrow the bed.

The stream can get low in the summer when we have dry conditions, and I’ve seen situations where the jack dams become barriers to fish movement. A lot of the jack dams have a section of planking across the stream that creates a waterfall during higher flows. During low flows, water trickles over these plank platforms and the pool level below them is too far for trout to jump with no flow to assist.

Below these jack dams, the water temperatures often reach levels that are not conducive to brook trout survival. I strongly believe that the jack dams actually contributed to the decline in brook trout in the stream. Brook trout move long distances regularly. Often a large percentage of the entire population of a waterway will migrate during different times of the year. I’ve witnessed this personally and know for certain that it’s occurs.

Without a way to reach the upper headwaters, the brook trout that are trapped below the jack dams likely die due to the water temperatures and larger predatory brown trout that live in the area.

The upper part of the stream is listed as Class A (our highest rating for wild trout density), but the state stocks right up to the line of where the Class A section starts. The state regularly stocks up to 5lb brown trout in this lower section, and I’ve encountered them far up into the Class A water. In addition to the large stocked brown trout, there are also some fairly large wild browns in the very upper headwater section as well.

Wild Brown trout from the upper headwaters area

In a recent trip to the area, I fished the headwaters to see if I could turn up some brook trout. It didn’t go well. There was still a fair amount of ice along the banks and the water temperature was in the mid to upper 30’s. For the beginning half of the trip, I didn’t move a single fish. At about noon I decided to take a break along the stream and wait for the water temperature to rise a bit.

Streamside Lunch

After my lunch, I almost immediately caught the first fish of the day. A brown trout. This was followed by several more brown trout. I ended up leaving that day without a single brook trout to the net.

My Field Notes from the day

I know there are a lot of fans of the brown trout out there. Especially the wild ones. For years I never really thought of them as anything other than a different species to fish for. Recently though, it’s become more and more apparent that they’re slowly taking over many of our native brook trout streams.

Now I view them as invasives.

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