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Tweed BioBlog: week beginning Monday 22nd August 2016

Monday: an office day, admin and more clearing out. Tuesday: I’ve long wanted to see some scales from Sea-trout caught out at sea, part way through their migration, to help read scales taken from fish back in the river and to see what sort of growth rate they have, and I have, at last, got some! This was organised by our colleagues at the Norfolk Rivers Trust who arranged for a licenced netsman to take scales from some of the Sea-trout he caught off North Norfolk and send them to me.  Nine of these were fish 450-500mm but one was 700mm / 4.2kg. What was immediately of interest was that the fish around the 450-480mm size had spawned last winter which puts them in the Till Whitling size category as they would have spawned at 400-450mm, the size that the Whitling do. The large fish looks as if it had spawned two winters ago, then missed a winter, which is a rather rare life-history but I’ll need to check that and get a second opinion. Wednesday: All day at a fish rescue on the Eddleston Water, where the Tweed Forum has organised some re-meandering of a straightened section for flood defence and we had to evacuate the fish from the old channel. This was well vegetated and so had good numbers of 150-180mm trout, all very fat, though only one over the 8″ (200mm). There were also half a dozen Salmon parr of 130-140mm (large for Tweed parr, as smolts here average 120mm) so fat that they could have been described as “clinically obese”. Good numbers of Salmon fry as well, for so far up a small channel. Thursday: Back looking at the Norfolk scales and checking them against readings from Whitling sampled in the College Burn. I’ve long thought that the Whitling might not migrate far, as they return so early and at such a small size – and the shallow, sandy seas around Lindisfarne are such a good feeding area, they could find everything they wanted there. However, seeing these scales from Norfolk , I’m changing my thinking on this – these Norfolk fish appear to fit what Whitling repeat-spawning scales would look like back at sea. For variety, also looked at scales from an unusually large salmon sent over by my counterpart at the Outer Hebrides Trust for a second opinion – such is the International World of Scale Reading -I’ll be getting some second opinions on some of the Norfolk Sea-trout scales from someone in Wales. Friday: Admin and more clearing out.