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A Tweed Fisheries Biologist’s Week – Monday 16th November

Monday 16th November: Almost the whole day out at the traps. James on duty over the weekend, but the water had been too high to do anything on Saturday. He got things going again on the Sunday, but the real clean up only possible today. Three Sea-trout and a Brown-trout female at the Peebles trap, the run beginning to start there and one going up at Tweedsmuir, which is a bit late as we’ve just been getting kelts coming down for the last two weeks. News from the new trap on a tributary of the Ale, a second salmon caught, this one a female, to match the little male caught there some time ago. So there’s a pair up this little burn, if they can find each other. I still can’t see how anything this small can be a proper salmon spawning burn, so we’ll have to do some electric-fishing next summer to see if anything actually did happen.

Tuesday 17th November: Out with Kenny to the traps, as some repairs needing done and still working on the improvements. Just a kelt in the Tweedsmuir trap and small immatures in the others. News from the trap at Coldstream, being run by the Angling Association there. They have been seeing the odd dead Grayling fry below the trap, with what appeared to be small bill / grab marks on them and have now seen the culprit – a Kingfisher. The bird is just not big enough to carry off something the size of a Grayling fry, but obviously tries. All but the Tweedsmuir trap get small immatures running up stream at spawning time, though only the Coldstream trap gets Grayling fry as well as Salmon and trout.

Wednesday 18th November: Out at the traps again, but today with a group of students from Napier University’s Aquatic Management M. Sc. course. A little rise in water overnight, so four takeable sized Brown-trout in the Cardrona trap and three immatures. Unusually, one of the larger trout was a female. Explained to the students that one of the reasons for running these traps is to see what actually spawns the juvenile trout we find in these burns when electric-fishing as it’s not possible to tell whether small  trout are going to be Sea or Brown trout till they actually smolt. At six out of the seven burns we’ve got traps on, it has turned  out that the vast majority of eggs come from Sea-trout females, fertilised largely by smaller, male  Brown-trout, so the spawning runs are made up of a lot of smaller Brown-trout and a few larger Sea-trout. We do get male Sea-trout, but they are much less common. We also get female Brown-trout, but these are also relatively rare. The exception to this is the population we trap at Tweedsmuir, which is a Brown-trout population with 50:50 males and females from 1 to 6lbs in size – but nothing in the trap  there to show the students today, as its probably finished here (the first snow on the hills around today). As a result of what we have been finding in the traps, one of the things we are working on is to establish the sex ratio of Brown-trout in the Tweed generally, so we can see if there is really such a thing as a Brown-trout population here or whether they are simply the freshwater-resident part of the Sea-trout population.

Thursday 19th November: Out to check the traps with Kenny, but not expecting even to be able to get to them in this water. Took the Cardrona trap out as low banks nearby and a flooding risk. Just took photos of the high flows at the others – had to go to Tweedsmuir via Broughton as the lower road closed due to flooding. News from the Coldstream trap is that they have started to catch Sea-trout there, showing it to be like the other populations, where the eggs come mainly from Sea-trout females and are fertilised by Brown-trout males.

Friday 20th November:  Weekly meeting in the morning and various bits of admin, including looking at more applications for the acoustic tracking Ph D.  Out with Kenny to the traps, but road closures due to the flooding making for detours. Too high to get the Cardrona trap back in or get near the Peebles one, but able to start the clean up at Tweedsmuir. Great chunks of turf and heather and a mass of gravel to be cleaned up – will take a few days. The “mini-grilse” are in the freezer now, and I’ll get the dissection done on Wednesday. Will be very interested to see what sex they are are whether they are maturing.