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A Tweed Fisheries Biologist’s Week – Monday 9th August

Monday 9th August: At a general meeting of the FASMOP programme in Perth, where most of the fisheries trusts taking part in this national salmon genetics mapping work were assembled to hear the latest progress report. The first part, however, was a workshop to explain some of the statistical and genetics analyses, which involved different groups picking coloured beads (“genetic variants”) out of plastic mugs (“genetic markers”) in order to work through an example of how the frequencies of genetic variants found in a fish can be related back to the frequencies found in possible source populations. Then we got the very first, preliminary results from the new SNPs (Single Nucleotide Polymorphism) results, which were fascinating. Using 200 of these SNPs, samples taken from juveniles on the Ettrick and the Gala could be blind tested with 100% accuracy i.e. all the Gala fish could be identified as coming from the Gala and all the Ettrick fish from the Ettrick, even though the Gala population is only 50 years old and had previously resisted all attempts to find genetic differences that could distinguish it. Even when samples from all of the five Tweed sites so far analysed were combined,  blind testing still identified more than 90% as coming from their correct sites – even though one of these sites was on the lower Ettrick and another on the Douglas Burn, a tributary of the Yarrow and therefore also within the Ettrick catchment. These are the very first results from this new technique, but it looks very promising.

Tuesday 10th August: Out electric-fishing again, firstly to a site in the middle of Gala. This is an unusually deep water site, inherited from the first electric-fishing survey of the Tweed carried out by the Faskally laboratory in 1988. It is therefore a site where we actually get takeable sized trout, the biggest today being 280mm (11″ – and very fat). There were 3 others over the 8″, so four in all, which is not bad for the centre of a town. It is also more suitable habitat for Eels than our normal type of sites and there were 34 here. Today's other site was in the main channel at Elibank, where an island splits the main stream so we can sample where otherwise the river would be too large. A lot of Salmon fry and parr but, unusually, no clear size difference between them. The largest fry seemed to be in the70-74mm class while the smallest parr seemed to be in the 75-79mm class but scales had to be taken to check on this (as per the SFCC national protocol which we follow). Usually there is a good, clear, size difference between the two ages of fish. Either the fry here are very fast growers (not the case actually, their overall size was not large) or the parr are slow. Certainly the contrast with the Gala site was extreme – there the parr ranged from 90 to 130mm with most being around 110mm, while the Elibank parr ranged from 75 to 110mm with most being around 90mm.

The reduced amount of Water Crowfoot in the river this summer has been commented on, so Kenny has been going round comparing this year's growth with that shown in the baseline photographic survey made by the clubs as part of the TTGI four or five years ago. Some of the contrasts are extreme, with very little weed showing this year compared to the baseline. Annoying though the weed is to anglers, it is really great habitat for juvenile salmon and trout (and for insect nymphs and larvae) so there must be less good habitat for juveniles this year. It has been suggested that the extreme cold of last winter could be responsible for this, or that in some places the ice got in to the gravel. Whatever the reason, it shows the value of having this baseline survey, as the impact can be clearly shown and proven.

Wednesday 11th August: Out electric-fishing again, to do quantitative sites on the lower Ettrick and Yarrow, so these sites are in what I call the “shadow zone” of the fish pass at Philiphaugh. Since we started annual, timed, electric-fishing of the Ettrick and Yarrow in 1997, salmon fry numbers have been consistently low on the lower Ettrick from Ettrickbridge (the Prison Linns) down to the cauld and from Lewenshope downstream on the Yarrow. Both upstream and downstream of this zone, fry numbers are normal. There's obviously plenty of spawning fish go through this area to the upstream zones, so why this depression ? The habitat is perfectly OK. What it appears to be is that the lower Ettrick and Yarrow are spawned in by late running fish as opposed to the Spring and Summer fish that spawn in their upper zones, and by November, the pass is starting to become difficult for fish to use. Water temperatures are low and daylight hours are short and we can see from the fish counter data that numbers getting up the pass then are very low in the mornings and pick up during the day as water temperatures rise – but when the sun sets, the fish stop. This is very different from how fish pass through earlier in the year, when there's almost no difference in the numbers passing at any time of day and the nights are short. Effectively then, the fish pass is a filter that restricts the late spawning fish that spawn in the zone just above the cauld and there's actually a significant relationship between the number of fish counted through in November and December and the fry abundance in this lower zone the following September. This may be the answer to the key question – Why have Springers continued in numbers on the Ettrick but have dwindled to very few on the Teviot and Upper Tweed which had major runs in the past ? If the pass is restricting the entry of late running and spawning fish, then that would protect the Spring population from their competition.

Thursday 12th August: The “Glorious Twelfth”, the start of the Fry Index electric-fishing season. Three teams of two out today, so a maximum possible of 45 sites. My area was the Wooler Water, from the town up to its top where there was a particular question to answer as well as to carry out the general survey. The ford at Haughhead, just outside Wooler is a barrier to salmon which the RTC had sorted out, but the recent massive spates have shattered the whole area and washed out the artificial rapids that had been built up below the ford to bring the fish to the fish pass, which also got gravelled up as the bed of the river was gouged out. As nothing could be done at the time, it was possible that salmon had failed to get past in any numbers – if the Till hadn't been due for its regular survey this year, we would have been sampling here anyway to find out about this. In the event, the answer was very clear – plenty of salmon fry below the ford, none above. A few salmon parr upstream from the previous year, but not many of those. Lots of trout parr above the ford as well as reasonable (but not huge) numbers of trout fry, so some Sea-trout must have got past. The changes made by the spates are enormous, practically the whole course of the stream has been gouged out, with bare boulders lining most of it now, and some wide areas of bare gravel where more than just the banks have washed out. The uppermost sites also showed a reduced number of trout parr – and the highest up one was all fry and no parr so it looks as if there's been a loss fish from the top of the stream which is now being recolonised by a new generation.

Friday 13th August: A short weekly staff meeting in the morning, then out to do more electric-fishing in the Bowmont area. One hill burn turned out to be lacking trout fry this sampling, though there were parr and older fish present, a situation which triggers further investigations.  The most likely cause of this sort of thing is an obstacle to spawning fish of some sort or other and there is probably a new culvert or water intake / pond on this burn. We also found lamprey larvae on this burn, at a site well up in the hills, well away from the main channel, an example of just how remote some lamprey populations can be, separated off from any others by long distances. We also did a couple of sites on the main Bowmont, where there are signs everywhere of the massive gravel movements caused by last year's exceptional floods – but they didn't affect the spawning as we found very good numbers of salmon fry. I'll have to check previous results from this area, but I did get the impression that they were “under Parr”, to coin a phrase, and there may have been losses of older fish leader to lower numbers of Parr this year.