The use of cleaner fish such as lumpfish (Cyclopterus lumpus) to control sea lice in aquaculture is rapidly emerging as an effective alternative to medicinal treatments. However lumpfish are a relatively new species to aquaculture and as a result, there still exists a number of knowledge gaps that need to be filled to develop sustainable lumpfish production. At the Aquaculture Canada and Coldwater Harvest 2016 Conference held in St John’s Newfoundland, Mr. Paul Howes, aquaculture technical manager at Swansea University’s Centre for Sustainable Aquatic Research (CSAR) explained some of the research being done to bring lumpfish as a sea lice control into reality.
In terms of reproduction, sperm quality and female fecundity, as well as fertilization and egg survival feature high on the list of research interests. One of the successes in this area related to lumpfish milt (seminal fluid). Research from the group has demonstrated how milt extenders can be used to increase the optimal viability of milt, from 2 – 3 days up to 9 days. The benefit of this is that the number of males needed for the fertilization rates can be reduced by up to 80%. Other measures include the development of a sperm bank, reducing the research group’s dependence on wild lumpfish populations.
Credit Happy Come/Flickr (CC BY 2.0)
Other issues surround the eggs, which have an adhesive coating to allow them to clump together in the wild. In an aquaculture setting clumped eggs present challenges for incubation, reducing survival. Eggs of this nature typically undergo egg degumming treatments that remove the adhesive layer from the eggs. Preliminary result from the group indicate that the use of 2% alcalase®, a liquid enzyme preparation, can degum 75% of the eggs, with no impact on the survival of hatched larvae.
Once lumpfish hatch, the next challenge for aquaculture is keeping them alive. A critical time for survival is around the 4 weeks post-hatch. By increasing the Otphime feeding to between 6 and 7 weeks, hatched larvae to 10g survival rates are currently in the region of 85%. Additional work looking at the benefits of adding Vitamin C to Otohime feed indicated little additional survival improvements over the use of Otohime alone.
Lumpfish welfare is also being explored at CSAR. One study, for example, demonstrated how captive juvenile lumpfish prefer dark, fine grained substrates. Another study looked at the use of structures inside the net pens. Here, lumpfish showed a preference for areas that offered protective factors, such as dark colours, those that were lower in the tank, and typically preferred to stay on the back side of any structures. By taking into account lumpfish preferences, lumpfish health can be improved.
Other work is looking at how lumpfish will behave in duo-culture systems. Preliminary work with sea bass and lumpfish has indicated that lumpfish behaviour does change when in the presence of sea bass – including becoming aggressive to sea bass. Research on behavioural changes is ongoing. Veterinary care techniques area also on CSARs agenda. Work to date includes operating on lumpfish eyes, which have been damaged during their capture in the wild. Eyes have been successfully removed and ocular nerves and blood vessels ligated under anaesthesia. To prevent infection, the orbit packed with a waterproof compound to prevent infection, and after just 5 days, the orbit is filled with scar tissue.
CSAR is one of the largest lumpfish producers in the UK. For their research, CSAR utilize a Recirculating Aquaculture System with a capacity of 60 m³. Other facilities include a quarantine room for the reception of broodstock, upwelling incubators, and larvae weaning tanks. When they launched in 2014, they successful reared 5,000 juvenile lumpfish, and to date have produced over 3 million eggs, and 2 million juvenile fish.
This story appeared on The Fish Site