The average amount of salmon lice found in the stomach of a Ballan wrasse is 70. (Photo: Havforskningsinstituttet)

Lice-eating wrasse to be put alongside salmon in aquaculture cages

NORWAY
Thursday, January 27, 2011, 15:00 (GMT + 9)

An environmentally-friendly way of reducing the amount of salmon lice in Norwegian aquaculture is putting lice-eating wrasse together with the salmon. A new large-scale research project will prepare for commercial aquaculture, in order to ensure an adequate supply of the lice eaters.

When it comes to eating salmon lice from large salmon, the Ballan wrasse (Labrus bergylta) is the most efficient wrasse, and it also gathers lice at lower temperatures than other species.

A total of 2 to 5 per cent of wrasse is needed in the sea cages in order to delouse the salmon, or in other words a cage containing 100,000 salmon requires 2000 to 5000 wrasse. The largest number of salmon lice found in the stomach of a single Ballan wrasse is 300, while the average is 70.

The Fishery and Aquaculture Industry Research Fund (FHF) is behind this heavy investment, which stretches over a three-year period and has a budget of around NOK 26 million (USD 4.5 million).

The objective is to develop the knowledge and experience that is necessary to attain a stable and predictable commercial production of the Ballan wrasse.

The wrasse are transferred to the sea cages and eat the sea lice on the farmed salmon, avoiding the need to use chemicals to delouse the salmon.

"The effort which is now commencing is unique in both a Norwegian and global context. Norway is the only salmon-producing country that is using wrasse on a large scale to combat salmon lice," says the Managing Director of the research fund, Arne E. Karlsen.

Until now mainly wild-captured wrasse has been used. However, there is a limited supply of wrasse in the wild, and an increase in the catch can pose a threat to the wild fish stocks.

The goal of the project is to cover at least 25 per cent of the requirements with farmed wrasse by 2013.

This project involves the leading industry actors and research institutions in Norway. Nofima is participating along with SINTEF Fisheries and Aquaculture, the Institute of Marine Research and the Norwegian University of Science and Technology (NTNU).

Roe that has been naturally spawned in the tanks was used during the first phase of wrasse farming. As wrasse roe is surrounded by an adhesive layer, attaining good disinfection is difficult, which is a necessity in order to attain a good survival rate and hatching.

In order to gain better control of the reproduction of wrasse, Nofima will work on methods to strip roe and sperm from the broodstock, methods for fertilisation of roe, and methods to prevent the roe from becoming surrounded by an adhesive layer. Finding good ways of disinfecting the roe will also be important.

In addition, Nofima will work to find out which environments are best for wrasse at various stages of development. This involves, among other factors, which temperatures provide the best roe quality and the best development of wrasse larvae.

Nofima will also work to develop feed and feeding regimes for the earliest stages of life.

The behaviour of young wrasse is also different than for instance young cod and halibut, and scientists will study whether different tank environments can have a positive effect on behaviour.

"Nofima’s interdisciplinary research team will contribute with many years of knowledge and experience in the production of various fish species, as well as experience with optimising environments and feeding in order to attain good fish welfare,” says Nofima Scientist, Synnøve Helland.

“The scientists have considerable experience working to ensure fish farmers attain a predictable production of high quality fish with low rates of deformities. We look forward to working with the industry and the other research environments to contribute to effective and sustainable farming of Ballan wrasse," continues Helland.

Other research on wrasse is also underway, including an existing research project on Ballan wrasse farming that started last year with funding totalling NOK 12 million (USD 2.1 million) from the Research Council of Norway, FHF and industry partners. The new project will be coordinated with the other ongoing research.

"It is estimated that the total Norwegian effort on Ballan wrasse farming, including research and industrial investments, is in the vicinity of NOK 100 million (USD 17.4 million)," says R & D Director at FHF, Kjell Maroni.

Four commercial fish farms for Ballan wrasse are currently under development. The owners include Marine Harvest, Salmar, Nova Sea, Midt-Norsk Havbruk, Sinkaberg Hansen, Lerøy Seafood Group, Bremnes Seashore and Grieg Seafood.

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