Given the current predictions, climate change is unlikely to have a significant effect on Scottish mariculture over the next decade. However, within the next 50 years or more, the forecast changes are likely to result in noticeable effects. Rising average water temperatures will result in faster growth rates for some species (e.g. Atlantic salmon, mussels and oysters) but prolonged periods of warmer summer temperatures may cause thermal stress, particularly for cold water species (e.g. cod and Atlantic halibut) and intertidal shellfish (oysters). However, warmer waters may provide opportunities to culture new species, or species that are currently economically marginal in UK waters.
Diseases of cultured fish and shellfish including bacterial, viral, parasitic and fungal diseases, will be affected by a changing thermal regime, but in a largely unpredictable manner. However, under conditions of thermal stress, cultured species are likely to be more susceptible to disease and warmer conditions may allow the establishment of exotic diseases, while diseases such as cold water vibriosisA bacterial disease of migratory and salt-water fish., may become much rarer. Sea lice are likely to remain a problem in salmon culture and rising temperatures will extend their season and may increase infective pressure, requiring more treatments. Increased storminess (higher frequency of strong wind speeds) predicted for certain seasons in some regions will increase the risk of escapes through equipment failure and may necessitate site relocation or changes to equipment design.
The forecast warmer waters with calmer, drier summer months will have an effect on planktonic communities, although this will be difficult to predict in detail. There may be an increase in the frequency of harmful algal and jellyfish blooms, potentially causing more fish kills and closures of shellfish harvesting areas, but the forecast reduction in summer precipitation may benefit classification of shellfish growing areas. Increased temperatures and more abundant plankton could also enhance early spawning success and spat fall of cultured shellfish species, to the benefit of the shellfish industry.
What is happening now - Low
What could happen in the future - Low
We have reviewed the levels of confidence given in the 2006 report and do not feel that these warrant changing, so overall they remain 'low'. Where confidence levels are provided in the individual sections of the full review (e.g. for direct effects of temperature increase) they are for 'what could happen in the future', not 'what is happening now'.
Impacts of climate change on the environmental impacts of aquaculture - e.g. assimilative capacity of receiving water bodies.
Given the uncertainties associated with the predictions it is not possible to predict the economic impacts on the aquaculture industry at present.
Matt J. Gubbins and Ian Bricknell
Fisheries Research Services, Marine Laboratory, 375 Victoria Road, Aberdeen AB11 9DB
Executive summary