On May 16 we released back into Beaver Brook four radiotagged brook trout we had captured by electrofishing 2 days earlier. The adventure was chronicled in a series of three posts (Day One of Operation Brook Trout, Day Two Operation Brook Trout, Day Three of Operation Brook Trout). The radiotags used should allow us to follow them for 160 or more days. Since these fish are adults we may actually be able to observe, for the first time in Shu Swamp, spawning in the fall.
Here is a map of their movements to date (different colored pins represent locations of different trout):
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So far things are going quite well. All four tags are still attached to their respective trout – a very unlikely outcome with the hatchery-reared fish we have released (over half of fish can’t be tracked beyond 2 weeks). Furthermore, they have moved very little if at all from their original release sites, anywhere from 100 meter maximum to as little as 1 meter. All three trout have stayed very close to the location at which they were captured. In fact three of the trout were originally PIT-tagged in our March electrofishing survey and have shown remarkable fidelty to the sites of capure back then.
As a basis of comparison here are the results of radiotracking of five hatchery-reared brook trout of similar size we released last spring and summer:
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Note the increase in scale in this map. Only one of the trout (101) managed to retain its tag (or possibly die) the life of the tag. You can easily see how these fish moved a lot more. 101 moved all the way to the Beaver Lake spillway before running way back upstream and settling down.
You can access all the radiotracking maps through the Radiotracking Trout Data page.