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Tweed BioBlog: week beginning Monday 25th July 2016

Monday: on leave in the morning, then admin for the afternoon. Tuesday: most of the day entering the data from the Bullhead monitoring sites electric-fished last Friday, numbers of them up, but no sign of any diminution in salmon or trout fry. Beardies have disappeared, not been found the last couple of monitorings, but there were never many to begin with. I don’t think we’ve any other  sites from which Beardies have disappeared though, need to check on this, so it could be an impact of predation. Down to the nets at Paxton in the evening, but only a single Sea-trout. Wednesday: Back out to the Bullhead sites to take the photographs and measurements, back to Paxton in the evening, but only a couple of Sea-trout. Again, the fish lacking Sea-lice. Thursday: got down to analysing the data we have on Sea-lice on the fish netted at Paxton and sure enough the absence of lice I’ve been noticing is real. Last year, the average numbers of lice on Sea-trout (bigger sample than Salmon) were 1.92, 1.3 and 1.96 for May, June and July compared to 0.2, 0.2 and 0.24 for this year. Maximum lice numbers on a fish for last year were 7, 6 and 8 compared to 1, 3 and 2 for this year. Most lice drop off within 48 hours of the entry in to fresh water, but some at least can persist for 5 or 6 days. It’s not as if the North Sea has suddenly become a lice-free zone, I can see where the lice have been on the fish, they must just be taking longer to come in to the river, spending more time in the estuary before deciding to make their final transition (or deciding to go back out to sea). Why they are doing that this year,  I do not know. Some netsmen say that small spates like we have been having do not clean the river, they only just stir up the muck and that cleaning only comes with big spates. Friday: Electric-fishing with James on the Oxnam as part of our regular survey work. Though small, and with a steep zone in the middle, salmon do get almost right to the top of this stream. Lamprey, too, can be found even at the topmost sites.  From the Oxnam went on to the lower Jed but it was up and coloured -and Kenny reported the same for the upper Jed where he’d gone after finishing the sites on the Rule, so we had to give up for the day.