Voluntary fish transport in land-based fish farms

Abstract

Experiments were conducted to study voluntary fish transport of Atlantic salmon (Salmo salar), out of tanks through gates in the tank walls, in land-based production farms. In the experiments the following variables were tested: gate size, gate location and water flow. The experiments were carried out in a special designed R- and D-plant where three fish tanks were connected to a transport canal by gates at the bottom level of the tanks. In this system a recycling circuit could create a water flow in the transport canal and through the gates into the fish tanks.The largest gate size tested (60 × 50 cm) gave the best voluntary fish transport with an average of 70·6% of the fish moving out of the tank within 7 hr. Of the gate locations tested, the best voluntary fish transport was obtained in the cases where the gate was located in the middle and at the far end of the wall in a semi-square tank in relation to the flow direction. Of the water flows tested, the highest flow (100 litres/s) resulted in the best voluntary fish transport with, on average, 67·7% of the fish moved out of tank over a period of 7 hr. Factor interactions were observed between gate size and water flow, and between gate size and gate location.