Looking fish in the eye - cataract as a problem in fish farming
Nordic Council of Ministers, Nordic Council of Ministers Secretariat2009 (English)Other (Other (popular science, discussion, etc.))
Increasing frequencies of cataracts (i.e., opacities in eye lens) have been diagnosed in farmed salmonids during past years. Cataract has proven a pronounced problem in fish farming because it leads to reduced eyesight and even total blindness of the fish. Of the Nordic countries, Norway has been the leading quarter in research on cataracts owing to the need to solve this problem that has been noticed to prevail in the economically significant Atlantic salmon farming and to lead to monetary losses because of impaired growth and lowered survival of the fish with cataracts. However, salmonid fishes are nowadays also subject to culture in order to enhance the various endangered local populations by stocking of captive-propagated fish in nature. Stocking is also conducted merely for fisheries purposes. Therefore, in addition to the economic questions, concern has also arisen of the possible role of cataracts in stocking success, not to mention the question of animal welfare in general. Although information of factors underlying cataract development has started to accumulate during past years, there still are gaps in our knowledge on the causes of cataract as well as on its consequences. Furthermore, quantitative information on the severity of the problem is still largely lacking. The main objectives of this joint Nordic research project ",Looking fish in the eye - cataract as a problem in fish farming ", (LFITE) carried out by scientists from Finland, Sweden and Norway was to fill these gaps in our knowledge by updating information on the prevalence of cataracts in hatchery (and wild) populations of salmonid fishes in the participating Nordic countries, illuminating factors important in influencing cataract development in fish eyes and finally, investigating also consequences of cataract to fish in the hatchery and to stocked fish in the wild. The report presents results from a number of case studies that have been conducted by the project group and collaborators. The project has shown cataracts to be relatively common in all the six salmonid species included in our surveys in Finland and Sweden. The prevalence and severity (coverage of eye lens) were however variable often related to an exposure to Diplostomum spp. parasites that use fish as their intermediate hosts. The result contrasts with findings from Norway about the importance of nutritional imbalance and environmental (abiotic) factors in predisposing fish to cataract development. Progress has also been achieved in the course of the project in the understanding of the potentially significant role of proximate biotic factors, parasite and pathogen infestation, as well as genetic predisposition in cataract formation. The project has also shed new light on the relationship between fish performance (metabolism, foraging, predation risk, breeding, survival in nature) and the occurrence of cataract. At the end of the report, conclusions and recommendations regarding possible lines of future actions are also proposed.
Place, publisher, year, edition, pages
Copenhagen: Nordic Council of Ministers , 2009. , 58 p.
TemaNord, ISSN 0908-6692 ; 2009:515
kalastus, tutkimus, elintarvikkeet, ympäristö
Fiskeri, Forskning, Fødevarer, Miljø
Fiskveiðar, Rannsóknir, Matvæli, Umhverfi
Fiskeri, Forskning, Næringsmidler, Miljø
Research subject Fisheries; Research; Food; Environment
IdentifiersURN: urn:nbn:se:norden:org:diva-522ISBN: 978-92-893-1838-9OAI: oai:DiVA.org:norden-522DiVA: diva2:700809