This week we deployed two rotary screw traps (RST) into the upper Tamar catchment to catch sea trout kelts on their post spawning migration back to sea. The traps are currently anchored in the middle of pools ready to be positioned for trapping once spawning commences later this month. The RST work when they are positioned in a narrow channel of fast running water, with enough flow to rotate the drum, the fish swims into the drum, usually in coloured water or at night and gets slowly rotated back into a collection chamber at the rear of the trap. It will mean long cold nights of work for GWCT staff – brrrrrrrrrrr.
The trapped kelts will have two tags inserted into their body cavity, an acoustic tag and a data storage tag (DST). The acoustic tag will tell us when the fish reaches the lower river and goes out to sea and upon recovery the DST will tell us how deep the fish swims and its location at sea. We trialled the recovery of the tags last winter, where we tagged 16 sea trout kelts, and recovered tags from 4 sea trout which are revealing some fascinating data on the depths these fish swim at sea.