The cage environment is the key to salmon production

Researchers are proposing four possible measures to improve the lives of farmed salmon and simultaneously increase production. By releasing feed below the surface and using underwater lights, you can lure the fish away from the sea lice larvae on the surface, and greater monitoring will make it possible to optimise the environment. If simple procedures are also developed to spot abnormal behaviour, fish farmers will be able to discover signs of disease at an earlier stage.

These proposals for possible measures are based on the results of many years’ work. The scientists have described in detail how salmon behave and respond to the cage environment, and how fish farmers can best use that knowledge to increase production.

- With more than 20 years of data and observations, we now have a better overall understanding of how cage environments vary and how salmon react to them. If fish farmers make use of this knowledge, it will allow them to break new ground in terms of cage environments, feeding regimes, the use of light, production efficiency, delousing and salmon welfare, says researcher and project manager Frode Oppedal of The Institute of Marine Research.

Salmon choose their environment
It is normal for the environment inside a cage to vary considerably over time and depending on the water depth. The depth at which salmon swim and the fish density depend on a number of factors: temperature, oxygen levels, salinity, currents, light, feeding regimes, appetite, chemicals, perceived fear, etc. These behavioural choices mean that the full volume of the cage is not used, and that fish density is greater at some depths than at others.

- It is typical to observe fish densities that are 1.5-5 times higher than what you would have if the fish were evenly distributed, and in extreme cases up to 20 times higher, explains Oppedal.

The scientists’ most important recommendations are:
1. Expand monitoring from the current low levels to include continuous measurement of the environment at several depths (temperature, oxygen and salinity) and in several cages (oxygen), to allow farmers to actively respond to unfavourable conditions. In the short term, feeding regimes can be adjusted, while in the longer term it may be relevant to reassess biomass, cage size, cage location and the general location of farms.

2. Adjust the depth at which feed is released in relation to where the salmon want to swim. The current practice is generally to release the feed on the surface, which forces the fish to swim up to the often unfavourable surface environment in order to eat. This measure would probably both improve fish welfare and increase production.

3. Guide the salmon away from the surface using underwater light and/or feeding during periods when there are high levels of sea lice near the sea surface, in order to reduce infection intensity. Reducing the number of lice on farmed fish will reduce the production of sea lice larvae, which have the potential to infect both wild and farmed fish. This will in turn reduce the stress caused by having to delouse the farmed fish, increasing fish welfare.

4. Abnormal behaviour is often an early warning of disease. An operational welfare index should therefore be developed, based on salmon behaviour in cages, which is easy for workers at fish farms to use.

Next steps
Based on this work, two new projects have been granted funding by The Research Council of Norway this year. They will focus on areas such as how individual fish experience the cage environment and the consequences of this, as well as tolerance levels of salmon of different sizes to variations in oxygen concentration and water currents.

Contact:
Frode Oppedal
56 36 75 31
971 66 781

Beate Hoddevik Sunnset
55 23 85 16
908 21 630 



Associated companies:


Related news

Latest news

New contract: Windcat 41 - no 17 in the Servogear series

Servogear announces the signing of a new contract with Windcat Workboats BV for the delivery of Servogear Controllable Pitch Propellers (CPP)  for their new vessel Windcat 41. 

Seacat Enterprise to be launched January 12th

Seacat Services, is preparing to launch its first High Speed Utility Vessel (HSUV), Seacat Enterprise at January 12th.

Norsafe Signs Contract with the Swedish Coast Guard (KBV)

On Wednesday 21st December, Norsafe signed yet another new contract with the Swedish Coast Guard (KBV) to deliver nine new Magnum 750 MKII boats.

A Unique Second-generation Tomograph is Developed

A new gamma-ray tomograph designed to image up to 4” diameter pipes, is developed by CMR Prototech for the Saskatchewan Research Council (SRC) in Canada.

Sohome launches a new website

Sohome has launched a new website that makes it easier to find key information. 

Sohome AS receives orders for Johan Sverdrup Project

Sohome AS is proud to be a sub-contractor to Intelecom AS for the Johan Sverdrup Project. 

New 55'' Ultra High Definition Chart and Planning table passes Type Approval testing

Most advanced maritime display system ever produced, the 55'' Ultra High Definition Chart & Planning table, enables Integrated Bridge System manufacturers to develop new multi-data solutions.

Norsafe's experience in the Polar Code Pays Off

In readiness for the introduction of the Polar code, Norsafe has become the first LSA supplier to have executed full scale tests and trials 

Øglænd System Group winner of Business of the Year Award

Øglænd System Group won the Business of the Year Award in the Stavanger-region 2016.