Training of Trainers - Library - Network of Aquaculture Centres in ...

Climate change and aquaculture: potential impacts, adaptations and mitigationSena S De Silva & Doris SotoNetwork of Aquaculture Centres in Asia-Pacific, Suraswadi Building,Department of Fisheries, Kasetsart University CampusBangkok 10900, Thailand(Source : FAO Technical Paper 530, pp. 142-216; 2009 )AbstractThis is a summary of a synthesis to address issues relating to impacts of climate change on aquaculture, thefarming of aquatic species. In order to treat the subject matter comprehensively, the role of aquaculture in itscontribution to the human food fish basket, in relation to that from capture fisheries is discussed. The food fishsupplies is the only animal protein commodity that is still predominated through hunting, but its being graduallyovertaken by farmed products, and currently the proportionate contribution of the latter to food fish consumptionapproximates 45 percent. In the above context and that of envisaged population growth the food fish supplyrequirements are estimated and the increasing contribution from aquaculture assessed. This change is alsoreflected in the increasing contribution of aquaculture to the total fisheries of the GDP in some of the mainproducing countries.Aquaculture is not practised evenly across the globe. The current aquaculture practices in relation to three climaticregimes, viz. tropical, sub-tropical and temperate regions are assessed, and in turn in relation to environmentaltypes viz. marine, fresh- and brackish waters and geographic divisions by continents. It is seen that aquaculture ispredominant in tropical and sub-tropical climatic regions, and geographically in the Asian region. Furthermore, themost predominant cultured commodities are finfish, molluscs, crustaceans and sea weeds, and in turnpredominated by species that feed low in the food chain. This geographic and climatic concentration ofaquaculture entails the need to focus the development of adaptive changes to combat climatic change impacts tosuch regions, for the time being and primarily, if the predicted gap in supply and demand in food fish supplies is tobe realised through aquaculture. However, we cannot disregard the potential for aquaculture growth in otherregions.The main potential elements of climate change that could impact on aquaculture production, such as sea level andtemperature rise, change in monsoonal rain patterns and extreme climatic events, water stress, are highlighted,and the reasons for such impacts evaluated. All cultured aquatic species for human food purposes arepoikilothermic and consequently temperature increases and or decreases would have a profound influence onproductivity. By virtue of the fact the that the different elements of climate change are likely to be manifested/experienced in different climatic zones, to varying degrees the direct impacts on aquaculture in the differentclimatic zones are considered. For example, it is predicted that global warming and the consequent increase inwater temperature could impact significantly and negatively on aquaculture in temperate climatic zones, becausesuch increases could exceed the optimal temperature range of organisms currently cultured, as opposed topossible positive impacts through enhanced growth and production in tropical and sub-tropical zones, but notwithout some possible negative impacts arising from other climatic change elements (e.g. increasedeutrophication in inland waters). In both instances possible adaptive measures for reducing/ maximising theimpacts are considered. An attempt is also made to deal with the climatic change impacts on different culturesystems, such as for example, inland and marine and in turn different forms of culture practices such as cageculture. Furthermore, on the negative front is the possibility of an increase in the virulence of pathogens because71