Copied and pasted, with permission, from the River Tweed News site:
Tweed Brown Trout Angling Recaptures
Those who have been keeping up to date on our Tweed News site will know that The Tweed Foundation has been trialling pattern recognition software, which is being used to identify individual trout from the spot patterns on their gill covers. Amongst other things, it is hoped that this will give us an insight into how often individual Brown trout are caught by anglers.
We recently put out an appeal to anglers to send in photos of the trout they catch so that we can check them against, and log them into, our trout pattern database. If you are able to help over the remainder of the season, we’d love to hear from you.
Three volunteers from the Gala Angling Association, who fish quite often, have been sending in photos of their catches from the very start of the trout season and, although they vary their fishing locations by also fishing on the Melrose and District and Peeblesshire Trout Fishing Association waters, they often fish on beats they have fished previously. As such, as the season has progressed, the anglers are starting to recapture some fish they’ve caught previously.
The first thing that is obvious from the results so far is that when the anglers fish in locations they’ve fished previously most of the fish that are caught are fish they haven’t caught before, although that’s not to say that the fish haven’t been caught before by other anglers, and recaptures make up only a small percentage of their catches. However, that small percentage does make for interesting reading:
It is too early to draw any firm conclusions from these results as the amount of data collected is small and first impressions may be misleading but, it would appear that larger trout are more likely to be recaptured by anglers than smaller ones, although it is possible that this is because of anglers opting to target the larger trout when multiple trout are rising. Some trout also appear to be considerably more aggressive and take greater risks than others when feeding. For example, Brown trout 2 was caught twice in the same evening by the same angler showing that, after being caught and released, this trout immediately returned to feeding and took the exact same fly again. This trout was also caught a third time in the same location, by the same angler, the next time he fished the beat.
39cms Brown trout from Ashiestiel that was caught three times, including twice in one evening
The most interesting results so far have come in the apparent response of the two largest trout that were recaptured: Brown trout 1 and Brown trout 4. After being caught once (trout 1), or twice (trout 2), the response of these trout was not to change the way they fed and become more cautious but to move. Brown trout 1 moved about 1km upstream between its first capture and its recapture five days later, and Brown trout 4 moved around 1km downstream between its first recapture and second recapture. The same response to being caught was recorded in a 52cm Brown trout that was caught three times by the same angler from Coldstream during 2014 (at that time we didn’t have the pattern recognition software but had pictures of the fish sent in by the angler that we’ve since run through the software).
50cms Brown trout caught at Traquair, which then moved 1km upstream between its first capture and its recapture
Please do help us with this important study. All it takes is a couple of photos, and information on exactly what we need to clearly see from the photo is explained on the Tweed Foundation’s YouTube Channel.