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Tweed BioBlog : Trout traps

Monday 2nd – Friday 6th November 2015: On trout trap duty this week.

Monday – Seven females trapped coming downstream in the Tweedsmuir trap today. It’s clear now that my joinery failure with the trap door, which broke during the one rather small rise of water there’s been on the burn so far this season, let fish get up as we have now had a number of fish coming down that we didn’t measure  going up. The picture below shows one of these kelts – they were all about 550mm, good-sized Brown-trout. Females go upstream a bit later than males and come down quite a bit earlier, they just “spawn and go” while the males hang around on the gravels, hoping for more females to turn up.2015-11-02 Tweedsmuir female kelt 03

Tuesday – Four more kelts, three females and a male coming down. We’ve started taking photos of the spot patterns on the gill covers to see if these can be used for individual identification without having to tag the fish. Certainly, there’s great variation in the patterns (see below) – and there’s software for equalising the photos to help match fish up:

Operculum Stanhope 2015-11-02 Female 480mm a CroppedOperculum Stanhope 2015-11-02 Female 495mm a Cropped

Wednesday – James on traps today while I went out with a student from the MSS Faskally laboratory to download some of the National network of water temperature dataloggers that are in the Tweed catchment. Up the Leithen and down the Gala was the collection route today, interesting to see that even in this cold summer, temperatures at the upland sites could reach 23C, when salmonids will suffer reduced growth. Thursday – Back on traps, but no fish at Tweedsmuir today – James got another one going down yesterday, which means we have now had more females going down than we recorded going up. There have also been twice as many females recorded as males yet this population is pretty strictly 50:50 male and female, so we’ve obviously missed a good number of males going up. Another small, mature male, Brown-trout at the Peebles trap today, so signs of the little males turning up there now, ready for the female Sea-trout to turn up. Friday – Budget day, with a joint meeting of the RTC committee and the Foundation trustees, then a check of the Peebles trap – two small immature Brown-trout.