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Unusually wet May and early June improves health of sea trout at sea

Posted: Tuesday 14 June, 2011 @ 17:36:06

Roger McLachlan, Ben Rushbrooke and David Mullaney at Boor Bay on 16th May 2011

The WRFT sea trout sweep netting programme is underway. Samples of over 30 fish have already been taken in Loch Ewe and Loch Gairloch. So far in 2011 we have recorded fewer lice on the fish than in some previous years. This may be partly due to heavy rain through much of May which meant that by the time of our first sample in mid May, there was much more freshwater around the coast than usual for the time of year.

Our first sample from Loch Ewe on 16th May 2011 included a sea trout of 487mm, the largest we have taken using a sweep net at Boor Bay to date. The fish had a tatty dorsal fin, suggesting that during the very dry, warm period which lasted through April until early May, the burden of parasitic lice may have been higher than recorded on the day of sampling. Subsequent samples in Loch Ewe and Loch Gairloch included many smaller post-smolt sea trout, mostly with relatively low levels of lice.

Another large sea trout of 510mm was taken on 14th June in Loch Gairloch. The fish carried 41 salmon lice, mostly pre-adults and adults. Another fish of 392mm was recognised as one that had been caught earlier in the year, on 18th March. In 3 months, the fish had put on over 200g in weight.

Sweep netting in 2011 is supported by The Scottish Government via the RAFTS Aquaculture Project.