Líffræðifélag Íslands - biologia.is
Líffræðiráðstefnan 2019

Erindi/veggspjald / Talk/poster V40

Long term data on R. salmoninarum screening of wild Atlantic salmon broodfish in Icelandic rivers

Höfundar / Authors: Edda Björk Hafstað Ármannsdóttir, Árni Kristmundsson, Sigríður Guðmundsdóttir

Starfsvettvangur / Affiliations: Tilraunastöð Háskóla Íslands í meinafræði að Keldum

Kynnir / Presenter: Edda Björk Hafstað Ármannsdóttir

Introduction: In enhancement programs wild salmon broodfish are collected, stripped, their offspring cultured in aquaculture facilities and smolts subsequently released into their river of origin. Renibacterium salmoninarum (Rs), the causative agent of bacterial kidney disease (BKD), is common and widespread in wild Icelandic salmonids. As Rs can be transmitted both horizontally and vertically, all wild female broodfish are screened and eggs from all Rs positive fish are discarded to avoid the release of infected fish.
Methodology: For 28 years (1991-2018), around 18,000 female broodfish, from numerous rivers, were screened for the presence of Rs using pELISA.
Results: The prevalence of Rs-positive fish was low in the first 15 years. In 2006, a significant prevalence increase was observed when 12% of the broodfish tested positive for Rs-antigens. The subsequent years, a further increase was observed, reaching a peak of 25-28% in 2008-2009. Associated with this increase, a considerable portion of fish from several rivers showed clinical signs of BKD in captivity. The following two years the prevalence dropped to around 10% and since 2012, it has been relatively low.
Conclusion: Increase in Rs-prevalence during 2006-2009 is not fully understood but research have shown that of Rs- prevalence increase the longer the fish stay in freshwater system. Thus, most broodfish used for enhancement are now caught soon after their freshwater entry and transferred to Rs-free facilities.