Profile of a Brook Trout Stream

I did a bit of fishing today at a stream within half a mile of my house. It is one that I fish often, and is a fascinating stretch of water. I didn't catch anything today, but I saw fish and even saw rises. I ended up fishing all the way up through the nursery water, where there are only a few brook trout over 5 inches. The last time I fished this section was 4 years ago, and it was just good to see that there are still fish in this absolutely tiny section of stream.

On my stroll home I began thinking about this stream and it's brook trout population. I realized it was a pretty interesting topic, so lets dive right in....

First I ought to describe the stream: It starts out in a deciduous forest as a very small spring. It increases in size and picks up more springs along a half mile long stretch before bassing under two very close bridges. It then wanders through some extremely thick thorn bushes for about 100 yard before flattening out and passing around the edge of a meadow. Here it is deep and undercut, but has sandy or muddy bottom. After exiting the meadow the stream becomes a freestone again and passes through about a mile of classic brook trout territory. There is a culvert and one old bridge along that stretch. After passing into residential property the stream drops under the highway, but the lowest stretch has about 50 yards of great habitat as a low gradient gravel bottom stream with deep bend pools. 

There appear to be three distinct fish populations in the stream: one group that spend the whole year in the uppermost stretch, a large population in the middle mile of water, and a separate population in the lowest 100 yards of the stream.  The uppermost group is the smallest. I have not yet caught an adult there, but I have seen them and saw a few today. What I have caught are the smaller ones. There are a lot of 1 to 3 inchers there! Going downstream, there are NO brook trout for 200 yard downstream of the bridges. The middle population spawns in the gravelly section right bellow the meadow.  The fish in the middle mile get to be about 7 inches. They are typical looking brookies, not much different from those in the adjacent watershed. The population in the lower river is truly isolated, a culvert prevents their movement upstream and the swampy water in the stream bellow is too warm for them to move down. The isolation of this population shows, they have a purplish or blueish cast totally different from the population upstream. It just goes to show the variety within populations and strains, even within one stream! 

A Typical Lower Creek Specimen

Normal Middle Section Brooky