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EcoFish : Summary of preliminary results
Posted by oddvar on 2010/4/15 3:22:23 (1839 reads) News by the same author



The problems with sealice in the farming of salmon in the partner countries, as well as in other countries such as Chile and Canada have increased.  The industry, environmental organizations and the governments are deeply concerned. There has been a large public and industry interest in our preliminary results as it is now recognised that the use of ballan wrasse will be an important tool to control sea lice. This interest has greatly increased during the last year as new reports are coming from the salmon industry, as well as critical questions from mass media and the public, related to the increased sea lice problems on both wild and farmed fish. This is related to the fact that the most important chemicals used for treatment of sea lice are not so effective due to resistance of the parasite to these drugs. The present results represent important steps towards the end products and services in this project. The project activities, although delayed, follow the implementation and activity plans. Many of the most fundamental and important tasks have been successfully conducted. The facilities used for the broodfish in Scotland were changed from small rearing tanks, as fish in these had not produced eggs, to larger tanks with capacity for larger numbers of broodstock. Conditions for establishing ballan wrasse broodstock were developed and it was concluded that the feeding regimes for broodstock have to be improved to encourage good condition of the fish and to ensure maturation. Larger broodstock will be obtained and suitable diets for ballan will be examined further with one or two commercial feed companies. The use of photoperiod with the broodstock of wrasse to alter spawning season was attempted but no eggs were spawned on this delayed regime, and eggs had therefore to be collected from wild fish. Eggs were hatched and wrasse larvae were stocked in small rearing units, and green water (i.e. rearing with algae) larval rearing techniques were compared with clear water techniques. Larvae were reared to weaning size and work continues on attempting to wean the juvenile ballan completely to dry feed. This appears to be a main bottleneck in production of ballan wrasse and this will make management and culture of juvenile wrasse more practical. Following this the juvenile fish will be used for a series of feed, temperature and stocking density trials. In Ireland, at MRI, the broodstock holding facilities are being altered for the forthcoming season as project partners have experienced greater success with larger tanks and larger aggregations of broodstock. Only eggs, hand-stripped from freshly caught wild fish, were obtained in this breeding season and these have been used to test egg holding and larval rearing systems and in a series of experiments to examine development of ballan wrasse eggs at different temperatures, and of larval development.  Similarly, it was necessary to use wild caught juveniles in studies on the feeding and growth rate of juvenile wrasse.  In Norway, Bioforsk published a short review on the potential of microalgae to reduce the bacterial pressure on ballan wrasse in captivity. Ballan wrasse females used in the 2009 season were maintained in captivity for 1 year prior to the spawning. There was no egg fertilization in the first spawning observed in June. After resupplying with males in all tanks at the end of June fertilization was obtained in most groups. However, fertilization rate varied from 5 to 85 %, showing a large potential for improvement. Disinfection of eggs using different chemicals and treatment time were not 100% effective, probably due to the stickiness of eggs. Microbial testing of the epiflora of eggs showed 2 pathogenic bacteria. Survival of ballan wrasse juveniles was around 10 % after 3 months. During weaning from live feed to dry feed most of the fish died. Through this first stage of the project it has been possible to assess all stages of the rearing process for ballan wrasse, and this is a good start in leading to large scale production. In the next season, 2010, high priority will be given to weaning diets and strategies to improve the overall survival. The innovative nature of this project is fully demonstrated by the fact that during the last year (2009) several private companies are now asking for information about EcoFish. During the last 2-3 months of 2009, 4-5 companies have indicated that they will establish hatcheries for production of the cleaner fish, Ballan wrasse, in Norway and Scotland. These private companies will mainly use the same methods and principles on broodstock husbandry and hatchery production of Ballan wrasse as have been developed in EcoFish. The partners of EcoFish are from three of the largest salmon producing nations in Europe – Norway, the UK and Ireland and there has been full cooperation and transfer of technology between the partners. The project has developed new knowledge and strategies that may help to solve a common but very serious problem for the European salmon industry. Further information and recommendations for the use of Ballan wrasse in salmon sea cages have been conveyed to several large private and salmon farming companies who made enquiry to the project partners. The preliminary results from Ecofish will contribute a practical solution to control lice in an environmentally friendly way to the European marine finfish aquaculture industry by developing methods for juvenile production and maximising the efficiency of ballan wrasse to control lice in sea cages. This project is concerned with a widely dispersed and diverse problem that has considerable influence on a major Northern European industry that provides substantial employment, thus services and product under development have an impact on a transnational level.

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