Optimisation of captive breeding of the lumpfish Cyclopterus lumpus for sea lice control in salmon farming.
Conference Paper: Aquaculture Europe 2015, Rotterdam.
With an annual value of £588 M, the Atlantic salmon farming sector is the UK's largest single food exporter, directly employing 1,086 people in 257 farms, located in rural communities in Scotland. Scottish salmon is exported to 60 countries and has built a reputation for quality, sustainability and welfare, with Protected Geographical Indication status and 65% of fish being accredited under RSPCA Freedom Food Standards. However, plans for growth are being hampered by the challenge from sea lice which is estimated to cost the economy in excess of £30 M annually. In addition to direct costs associated with sea lice control, there is the potential for production losses associated with reduced growth, immunosuppression, and impaired welfare, all of which would have a negative effect on sustainability and potential for industry growth. The UK is restricted in the number of anti-sea lice medicines that can be used and current therapeutants are becoming less effective. Cleaner fish are a greener alternative to the use of these medicines, and ballan wrasse (Labrus bergylta) are being successfully farmed. Wrasse are very efficient at delousing salmon but they perform less well in winter. Lumpfish (Cyclopterus lumpus) prefer colder water and the two species will work well together in a complementary delousing strategy. To meet industry demands, ~10M cleaner fish of both species will be needed by 2020. We began in late 2014 a joint project aimed at developing and optimizing the sustainable farming of lumpfish, and its commercial deployment. To date + 1 million alevins have been produced from 120 females, of which 38 females were released back to the wild while a similar number are being reconditioned in captivity. Delousing of wild broodstock has been achieved by freshwater baths on entry followed by quarantine. Caligus sp., Gyrodactylus sp., and opportunistic ciliates have been observed and these were treated with Flukesolve, Licesolve and formalin baths, respectively. Lesions on adults have been treated with Topical Orabase. Egg husbandry has consisted of flattening and shaping egg masses to avoid 'dead areas' and, in the absence of natural male care, this appears to increase hatch rates, which is also enhanced by upwelling hopper incubators. Pilot results also indicate that keeping egg masses from single females in separate incubators facilitates husbandry and assists with traceability, while regular Pyceze treatment are also beneficial. Degumming trials involving alcalase, trypsin and milk have yielded inconclusive or mixed results and require further research. Larva are reared at densities ranging from 20 to 100 larvae/L starting with a small flow (c. 1L/min) rising to 15L/min after larvae become more active. Initial weaning rations were 10% biomass, and these were then reduced to 5% biomass after three weeks consisting of Artemia and dry feeds 250-350µm in size. The farming of lumpfish represents a unique opportunity to develop a new aquaculture species, create jobs in remote areas, and achieve greater sustainability in salmon farming. There are several challenges. For example, it is proving difficult to obtain quality gametes consistently, as broodstock become easily stressed during transport and handling, fry survival is variable, and no broodstock has been reconditioned to spawn over more than one breeding season. We have identified several production bottlenecks where innovative research is needed to farm lumpfish sustainably, namely (1) Optimization of reproduction and juvenile production, (2) Traceability and genetic characterization, and (3) Disease screening, biosecurity and monitoring during deployment.