SARF068: Use of wrasse as a means of managing sea lice in pen farming of Atlantic salmon

Start Date: 01/03/2010
End Date: 01/03/2012
Main Contractor(s): Viking Fish Farms Ltd
Other Sponsor(s):  

Objectives

The specific objectives of the project are:

Field testing of the effects of ballan wrasse, a suggested more effective cleaner fish than smaller species, on controlling sea lice abundance on salmon at a range of sites.

Assessment of the use of wrasse in different years of the salmon production cycle.

Examining the conditions of wrasse use on farms, for example the ratio of wrasse to salmon and length of wrasse.

To identify husbandry systems to maintain good welfare of wrasse in cages and to assess measures of welfare.

To provide recommendations of good practice to industry.

Summary

The main objectives of this research are to (i) utilise an integrated approach to sea lice management by using ballan wrasse collected from the wild and to field test their effectiveness in a combined strategy with restricted use of medicines. This is being suggested as farmed ballan wrasse will not be available for 2 to 3 years. (ii) Lice control strategies utilising wrasse would be compared with medicine only intervention and (iii) evaluate measures to ensure the welfare of wrasse in cages. These measures would be coordinated with other projects in this area in Scotland, including work at the NAFC.

The project expects to achieve these objectives by (i) field testing the effects of cleaner fish on sea lice abundance at a range of sea farm sites; sea lice numbers would be measured through the production cycle and would be compared with those in cages with no wrasse, (ii) by comparing the use of wrasse in the first and second years of production, (iii) assessment of measures to ensure the welfare of wrasse such as transfer between cages, provision of refuges  and protection against diseases.

Results from these field trials with ballan wrasse will validate the effectiveness of alternative lice control strategies using an integrated approach. The project is expected to advise fish farmers on the optimum use of ballan wrasse for sea control and to recommend measures to maintain the condition of the cleaner fish.