Print Shortlink

Tweed BioBlog: week beginning Monday 18th July 2016

Monday: We’re beginning a programme to look at smolt survival during their downriver migration in more detail, part of which will be to look at trout predation, particularly around the caulds. We got a set of stomach contents for this, back in May, but only just looked at it today. A 550mm trout, so not enormous, but it had six salmonids in its bulging stomach (and yet still took a spinner). The largest, going by size, was a Sea-trout smolt but the others look more like salmon (photo below). The larger of these must have been smolt sized but we also have a lot of small smolts on the Tweed, 90-110mm, so the smaller could well have been smolts too. The fact that the trout had got this number could also suggest smolts – we’ll need to look at stomachs outside of tRD.16.01b Stomach contents cropped  comphe smolt season to see what the pattern of predation is then. Tuesday: In the office, started on a paper on stock-by-stock management for the MSS / Local Biologists liaison group, which is largely an update and adaptation of Section 6 of the Tweed Fisheries Management plan (which is being updated this year anyway). Wednesday: had planned to go electric-fishing to do the triennial check-up on the alien invasive Bullheads on a tributary of the Ale, but the thunder and very alarming sky caused an early cancellation. Thursday: finalised an EIA for the proposed Hawick Flood Defence works, then had the weekly staff meeting, to free up tomorrow. Friday; out to do the Bullhead monitoring, where we are looking at both numbers of Bullheads and numbers of salmon and trout fry. There’s no consensus in the scientific literature – in some places, Bullhead have clearly depressed salmonid numbers (e.g. in the Braid Hills Burn, Edinburgh, they have completely replaced trout) but in others there doesn’t seem to be an effect. One factor may be the level of predation on Bullheads and it was interesting to find more Eel than I would have expected at the sites today.