FISH-LIFT: a device for sampling live fish with trawls

Abstract

A device for collection of viable samples of salmonids and other fish by trawl has been developed. The FISH-LIFT is in principle a closed aquarium connected to the trawl cod-end, designed to produce the lowest possible turbulence inside. The low turbulence allows the fish to swim unharmed in the aquarium once caught. A grid may be mounted at the front of the aquarium to retain certain size groups and to prevent unwanted items like jellyfish from entering. The aquarium may be either hoisted or hauled onboard the vessel through the trawl slip. Three models have been tested so far during full-scale surveys with a total of ≈200 hauls. The device has proven successful and viable samples of up to 300 Atlantic salmon post-smolts with negligible scale losses have been caught. Successful laboratory experiments have been carried out with these fish. The FISH-LIFT is commended as a suitable tool for investigations requiring trawl caught live fish, as for the study of external parasites, for loosely scaled fish, for deep water fishes, for tagging experiments and for the collection of fish for other experiments and aquariums.