PRODUCTION OF ATLANTIC SALMON POST-SMOLTS (Salmo Salar) IN FLEXIBAG SEMI-CLOSED CONTAINMENT SYSTEM

J. Kolarevic1*, R. Iversen2, S. Martinsen2#, P.G. Kvenseth3 and B.F. Terjesen1

1Nofima AS, Sjølsengvegen 22, NO-6600, Sunndalsøra, Norway;*E-mail: jelena.kolarevic@nofima.no
2Nekton Havbruk, Aunvågen, 6570 Smøla, Norway; #current adress, Morefish, 7464 Trondheim
3Smøla Klekkeri og Settefisk, Gnr 53 Bnr 23, 6570 Smøla,Norway
Introduction

The use of floating semi-closed containment systems in the sea can provide solution to a number of challenges facing the salmon industry today, such as escapees, lice infestation, and other environmental issues. Up to date there is still little information available about performance and welfare of Atlantic salmon post-smolts under commercial production conditions in semi-closed systems in sea. Currently, a number of different semi-closed containment system proto-types are being tested in Norway. A floating semi-closed containment system with flexible walls made of tarpaulin was tested during summer 2014 (1^st generation) and 2015 (2^nd generation), at Smøla (location Gullklakken), at the West-coast of Norway, and the data about water quality and post-smolt performance and welfare will be presented.

Materials and Methods

The 1^st generation of the flexibag (1720m³) was tested during summer 2014 when a total of 60 000 smolts with an average individual weight of 130g were stocked in the system. Intake water was pumped from 12m deep. Horizontal and vertical profiling of water quality within the bag and in the surrounding water was done. In addition individual weights were noted and scoring of the external welfare indicators was done on three occasions during the experiment. The 2^nd generation of the flexibag (2500m³) was tested in the summer of 2015 with focus on the water quality profiling within the bag. On this occasion 100 000 fish with the average individual weight of 95 g were transferred to the flexibag. The following water quality parameters were measured during both experiments: dissolved carbon dioxide, oxygen, temperature, pH, salinity, turbidity, total suspended solids, total ammonia nitrogen and nitrite nitrogen.

Results

The fish showed a relatively high survival rate and sea lice were not observed during the course of the trials. However, although a deterioration in welfare score of several external welfare indicators were observed after transfer into the flexibag during the 1^st study, essentially no further change in scores were observed with time in the semi-closed system. Differences in water quality between the flexibag and surrounding sea water and within the bag were observed, but none of the measured water quality parameters reached known toxic or damaging concentrations for Atlantic salmon.

Acknowledgements

This study was funded by The Research Council of Norway (project 217502/E40 Optimized Postsmolt Production "OPP" and 237856/O30 CtrlAQUA SFI, Centre for Closed-Containment Aquaculture) and partners and the Regional Research Fond Mid-Norway (project 217434 HDN - helduk og not i lukket anlegg).