Report of the Working Group on Pathology and Diseases of Marine Organisms (WGPDMO)

The Working Group on Pathology and Diseases of Marine Organisms (WGPDMO) met on 13–17 February 2018 at the University of Agriculture, Riga, Latvia. The meeting was chaired by Ryan Carnegie, USA, and attended by eleven participants, representing eleven ICES member countries.The agenda included several topics related to diseases and pathology in wild and farmed fish and shellfish. The group produced a report on new disease trends in the ICES area based on national reports from fifteen member countries. Notable reports for wild fish included observations of salmonid alphavirus SAV6 and Photobacterium damsellae in bal-lan wrasse, underscoring the need for disease surveillance in wrasse used as cleaner fish in salmonid aquaculture; the first observations of parasites Ichthyobodo salmonis and Desmozoon lepeophtherii in Pacific salmon from western Canada; high prevalences of Loma branchialis and increasing prevalences of Contracaecum osculatum in Baltic cod from the eastern Baltic Sea; and increasing prevalence of M74/thiamine deficiency in salmon yolk sac fry in Sweden. The considerable number of new and emerging disease trends in wild fish, all relevant to important fisheries, highlight the urgent need to continue disease monitoring of wild fish populations in the ICES region.Reports for farmed fish included the first cases of heart and skeletal muscle inflammation (HSMI) caused by piscine orthoreovirus (PRV) in Atlantic salmon in western Canada; the first report of infectious haematopoietic necrosis virus (IHNV) in Finland, in rainbow trout; the first report of I. salmonis in Atlantic salmon in Canada, in aquaculture in British Columbia; widening geographic distribution and increased effects on younger salmon of cardiomyopathy syndrome (CMS) caused by piscine myocarditis virus (PMCV) in Scotland and Ireland; and increasing cases of complex gill disease (CGD) in Atlantic salmon in Scotland. Complex gill disease is an increasing concern among ICES member countries, and better understanding and developing strategies to mitigate CGD will be a new focus of WGPDMO effort.