Avon salmon smolt run slowing down

Over the weekend the number of smolts captured in the Avon traps dropped significantly with only about 40 fish today. Having said that Saturday was one of the few problematic days encountered this trapping season. River levels had peaked at 60cm overnight, the highest recorded since the traps were deployed, and the water was dirty with a lot of debris. A branch had lodged in the 4ft trap at some point after 9pm stopping it rotating. Consequently the catch in the 4ft trap was only 6 fish. The 6ft trap was still functioning, although turning slowly, but there were only about 24 fish in it.

This is the downside to the rotary screw traps; they effectively filter a lot of water, including debris, some of which ends up in the fish box although smaller stuff can become enmeshed on the cone. These traps work by the river flow acting on the baffles to provide the rotational torque. However if the mesh on the cone becomes clogged the water flowing downstream can’t pass out through the mesh and the rotation slows or stops. Recently we have had to clean the trap daily as there has been a lot of fibrous algae washed downstream in the higher flows.

Tough fibrous algae that has been clogging the trap in increasing quantities recently. We have now changed the management of the trap by leaving it elevated during the day and dropping to operational height int he evening.

Tough fibrous algae like this has been clogging the trap in increasing quantities recently. We have now changed the management of the trap by leaving it in an elevated position during the day and dropping to operational height in the evening.

Saturday was a disappointing day but the catches yesterday and today were still a lot lower than last week. We had about 60 fish yesterday and about 30 today whereas 750 were caught last Thursday and Friday. It looks as if the salmon smolt run is coming to an end but we are still getting trout; a mixture of parr, presmolts and smolts.

A nice wee trout smolt of about 125mm

A nice wee trout smolt of about 125mm

A bigger trout of 230mm. Is was very silver when viewed from the the tail end, we classed it as a smolt.

A bigger trout of 255mm. Is looked very silver when viewed from the the tail end, we classed it as a smolt.

We have only caught about 700 trout so far including parr (compared to 14,000 salmon) but the trout run may continue for a while. Few trout have been marked so far with only one recaptured. Hopefully we wil be able to mark more trout in the next week or two.

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