Skip to content

2017 sweep netting season starts with sample of louse-infested sea trout in Loch Gairloch

Posted: Monday 1 May, 2017 @ 04:52:24

The sweep netting team and one of the sea trout at Flowerdale on 27 April 2017

Thirty two sea trout were caught in the first SWRFT sweep netting session of 2017 in Loch Gairloch. These fish were assumed to be a mix of overwintered finnock and older sea trout (rather than this year’s sea trout smolts) of lengths between 218mm and 340mm. Scale samples have been taken to confirm fish and sea age.

Sea trout were generally thin with an average condition factor (for the thirteen fish which were weighed prior to scales failing) of 0.88.

The average estimated lice count on these fish was 98 lice per fish (range 16 to 340). Larger lice were Lepeophtheirus salmonis, smaller lice (too small to distinguish in the field) were also assumed to be L. salmonis. Most of the lice were very small copepodid or chalimus lice.

Most of these fish are assumed to have returned early to freshwater as a result of sea lice infestation (c. Taranger et al, 2014).

A summary report with data for individual fish can be found here or on the downloads page at Sea trout sample Flowerdale 27 April 2017.pdf .

For help with sweep netting, thank you to Bill and Fraser Anderson, Bill Whyte, Dave Barclay, Ian White, and Mark and Kirsty Williams.

Sweep netting has been supported by Wester Ross Area Salmon Fishery Board and The Scottish Government.