Scottish Animal Welfare Commission: welfare of cleaner fish used in the Scottish salmon industry - report

6. Conclusions and recommendations

Recommendations for further research

Further research is required to determine the causes of the unexplained losses of cleaner fish. The losses may be very high and the missing animals are likely to have died and likely experienced poor welfare before death due to disease or predation. Likewise, causes of mortality should be investigated, including the impact of disease, and an investigation of the likelihood of predation or undernutrition contributing to mortality. The variation in mortality rates shown in the literature and through the discussion with industry indicates that lower rates are possible.

-As part of the endeavour to decrease losses, better records of numbers of cleaner fish put into salmon sea pens and how many are recovered from them at the end of the salmon production cycle are needed. This would aid in understanding the extent of losses and, in conjunction with other data capture, would likely help to understand factors leading to losses.

We recommend the implementation of welfare assessment protocols for cleaner fish that cover all phases of rearing and deployment, from the capture of wild wrasses, transport of all cleaner fish from point of capture or rearing facilities to the salmon farm, during any on-farm conditioning/acclimation period and during the period when they live in the salmon pen. OWIs for cleaner fish have been created by some in the industry, but they should be reviewed independently and used across the industry to allow welfare to be monitored at all life stages. The RSPCA guidelines could be strengthened to include OWIs. There should also be action plans in place for when welfare compromises are identified.

-Further research should be carried out into management including acclimation conditions, rearing conditions and the best methods to encourage foraging on sea lice to improve effectiveness and therefore reduce the number of cleaner fish required.

-Further research is needed to develop methods for effectively removing cleaner fish before salmon treatment to reduce stress and mortality in the cleaner fish during these procedures.

-Research into effective health treatments specifically for diseases affecting cleaner fish is needed. Likewise, the development of species-specific slaughter methods for all cleaner fish and handling methods for lumpfish are needed.

-The environmental and social needs of cleaner fish during captive breeding and rearing and how these affect their efficacy in sea louse removal are still not fully understood. There is much more that could be done to understand the environmental enrichment needs of the cleaner fish during their lifetimes, from the captive breeding and rearing phases and through into their use in the salmon sea pens.

Overall recommendations and conclusions

In recognition of the impact of cleaner fish on salmon welfare and potential benefits for wild fish stocks of a reduction in sea louse numbers, we do not currently recommend any changes to the practice of using cleaner fish in salmon farming in Scotland.

However, we do recommend that further research is conducted into the welfare of cleaner fish, including, in particular better record keeping around the losses of animals in sea pens, and action to improve survival.

Further, we would recommend that alternatives to the use of cleaner fish for sea louse control are explored, with the aim of phasing out the use of cleaner fish once sustainable alternatives are in place, and preferably within the next ten years.