The answer to that question is that I’m not entirely sure (see the previous research section for why there is confusion). But, this summer I started an eight month study of brook trout movement patterns in the Loyalsock Creek watershed in Pennsylvania to help determine the answer. I’ll be providing regular updates on this project through this blog, but, before I begin, let’s talk a little about the methods I’m using.
I’m studying movement patterns using radio telemetry. This process involves surgically implanting a small tag (0.0005 pounds) inside the abdominal cavity of a fish. Attached to the tag is a thin antenna wire that is passed through the abdominal wall and remains outside of the fish. Radio telemetry is a fairly common method for studying movement in a variety of fish species. So, if you ever catch a fish with a wire hanging out from its side, there’s a good chance its part of a radio telemetry study (and the researchers would be very grateful if you put it back!).
Every five seconds the tag transmits a signal that can be picked up by a receiver. Researchers either mount stationary receivers in locations of high movement or, in my case, walk around with the receiver and an antenna in search for signals coming from tags. When a signal is picked up, the receiver reads out two important pieces of information:
This summer we tagged 103 brook trout with radio telemetry tags. These fish are spread out across four streams, and we track each individual about twice a week to see how changes in stream flow or temperature may trigger fish to move.
The battery life of the tags is about 150 days, so I am planning to track summer movement into August, and then tag an additional 60 fish in late summer to monitor fall spawning movement. The prediction is that low stream flows and high temperatures in summer with limit movement. But, come late September, fish will begin moving to access spawning habitat. Previous studies have shown that some trout can move over 3 miles to spawn, so needless to say I didn’t renew my gym membership for the fall.
The telemetry tagging was just one part of the data that I am collecting this summer. Stay tuned to hear about why (and how) we draw blood from fish, why I know some fish are shy, and how I build a trout's family tree.