The potential impact of climate change on the infectious diseases of commercially important shellfish populations in the Irish Sea-a review

The Irish Sea and surrounding regions are a rich source of shellfish production as a result of captive fishing and aquaculture. Key species produced include lobsters (Homarus gammarus), edible crabs (Cancer pagurus), langoustines (Nephrops norvegicus), flat oysters (Ostrea edulis), cockles (Cerestoderma edule) and blue mussels (Mytilus edulis). The role played by infectious disease in limiting the sustainability of the production of these species is largely neglected. This review summarizes our knowledge of the key diseases of commercially important crustaceans and bivalve molluscs and attempts to determine their role in limiting the population of animals available for food production both at present and in the future. It shows that the key diseases threatening the sustainability of shellfish production are bitter crab disease in langoustines and edible crabs, and a wide range of diseases caused by micro- and macro-parasites in some bivalve molluscs including oysters and cockles. Oceanographic models are also employed to predict how changes in climate over the next half century may affect these key diseases and their hosts as found in the Irish Sea. It is concluded that the paucity of information on the potential transfer of some disease agents in pelagic larval stages of hosts and vectors is a major hurdle in predicting how some changes in environmental conditions may influence the prevalence and severity of shellfish diseases in coming years.