International Journal of Aquaculture, 2024, Vol.14, No.4, 195-210 http://www.aquapublisher.com/index.php/ija 198 2.2 Drivers of climate change According to the definition provided by the World Meteorological Organisation, climate is the average variability of significant amounts of different atmospheric variables over a period ranging from months to thousands of years. Long-term weather patterns are described by a place's climate. Though it is challenging to connect specific weather events to climate change, the increase in global temperature has been projected to induce more general effects, such as glacial retreat, shrinkage of the Arctic, and global sea level rise. Glaciers are rapidly changing all over the world, which undoubtedly affects how ocean currents flow and move plankton, which is the primary food source for aquatic life. Ninawe et al. (2018) expressed the fact that global warming is jeopardizing the seasonal plankton blooms, causing a decrease in fish consuming these organic materials, thereby increasing the water sulfide content. Likewise, a surge in carbon dioxide level due to climate change would reduce the sea water’s pH level, acidifying the seawater, and consequently adversely impacting crustaceans. According to Koenigstein et al. (2016), many fish stocks will be affected by the effects of climate change, which include ocean acidification, oxygen depletion, and other long-term and regional environmental changes like salinity, nutrient redistribution or eutrophication, as well as pollution. Feeding, breathing, osmoregulation, growth, and reproduction are all significant physiological processes that are controlled by temperature (Ninawe et al., 2018). The foundation of an optimal living environment and fish species reproduction criteria depend largely on water temperature. It is assumed that a fish population can strive to live under certain conditions within temperature variations in a specific area for a determined time otherwise there is a migration that would occur. According to the study conducted by Ninawe et al. (2018), for a region experiencing climatic temperature changes, a fish population would pursue the following characteristic behaviours: moving from the southern area to the northern area of an ovulation region, changes in ovulation areas, likelihood migration for northern latitudes and elongation of fish growth period throughout the year. Ninawe et al. (2018) described the impacts of fisheries observed in India in their study. It was noted that the variety of fish, its distribution, its abundance, and its phenology of fish may be impacted by water warming. Fisheries will suffer greatly from storms, floods, and drought. Due to their fundamental living metabolism and the availability of food organisms, many fish species have a restricted range of optimum temperatures. Therefore, the distribution of these organisms and life processes could be impacted by just a minimal 10 ℃ shift in seawater. The changing distribution of fish species, recruitment, and their abundance during shorter periods, such as a few years, may be brought on by rising temperatures (Koenigstein et al., 2016). 2.3 Climate change in the aquaculture sector Troell et al. (2017) redefined aquaculture as a counterpart of traditional agriculture producing food from aquatic environments as a main growing medium. Similarly, aquaculture includes farming of aquatic organisms including fish, crustaceans, plants and molluscs, with the intended purpose of the rearing process to improve the traditional stock and feeds and give protection from predators. Holmyard (2021) announced that though it is expected that aquaculture is going to increase production by 2050 reaching its target of 74 million metric tons, the actual trending estimated global warming scenarios would drop production by 16%, posing an unprecedented threat. The focus in the world is that aquaculture is currently able to substantiate access to good protein, minerals and healthy omega-3 fatty acids, allowing a healthier and wealthier food supply (Galappaththi et al., 2020). Scenarios described by Holmyard (2021) still showcase alarming impacts of climate change such as a reduction of forage-fish supplies to be used as fishmeal or oils in aquafeeds, shifting of ocean currents regimes and warming of waters altering the ecosystem altogether. It is no longer viable to replace fish forages with wild-caught fish thus alternative plant-based sources need to be adopted such as soy or corn, nevertheless. These plants are themselves being severely affected by climate change and extensive usage.
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