Fisheries are affected by climate change in many ways: marineaquatic ecosystems are being affected byrising ocean temperatures,[2]ocean acidification[3] andocean deoxygenation, whilefreshwater ecosystems are being impacted by changes in water temperature, water flow, and fish habitat loss.[4] These effects vary in the context of eachfishery.[5]Climate change is modifying fish distributions[6] and the productivity of marine and freshwater species. Climate change is expected to lead to significant changes in the availability and trade offish products.[7] The geopolitical and economic consequences will be significant, especially for the countries most dependent on the sector. The biggest decreases in maximum catch potential can be expected in the tropics, mostly in the South Pacific regions.[7]: iv
Theimpacts of climate change on ocean systems has impacts on thesustainability offisheries andaquaculture, on the livelihoods of the communities that depend on fisheries, and on the ability of the oceans to capture and store carbon (biological pump). The effect ofsea level rise means that coastalfishing communities are significantly impacted by climate change, while changing rainfall patterns and water use impact on inland freshwater fisheries and aquaculture.[8] Increased risks of floods, diseases, parasites andharmful algal blooms are climate change impacts onaquaculture which can lead to losses of production and infrastructure.[7]
It is projected that "climate change decreases the modelled global fish community biomass by as much as 30% by 2100".[9]
However, for projections to be more reliable, many more factors should be taken into account in 2025. An extensive current review recommends: "For projections at a multidecadal scale, it is essential to consider, along with the anthropogenic effects, the demonstrated influence of solar activity and volcanic aerosol forcing in climatic changes in the 20th century and to apply mathematical models based on historical reconstructions of at least 100 years, including the oceanographic variables available in the water column and multiple human activities"[10]
Oceans andcoastal ecosystems play an important role in theglobal carbon cycle and inCarbon sequestration. Risingocean temperatures andocean acidification are the results of higher levels of greenhouse gases in the atmosphere. Healthy ocean ecosystems are essential for the mitigation of climate change.[12] Coral reefs provide habitat for millions of fish species and with no change it can provoke these reefs to die.[13]Furthermore, the rise in sea levels also affects other ecosystems such as mangroves and marshes, making them experience a lack of both land and hinterland for the purpose to migrate.[14]
There are manyeffects of climate change on oceans. One of the most important is an increase inocean temperatures. More frequentmarine heatwaves are linked to this. The rising temperature contributes to arise in sea levels due to the expansion of water as it warms and the melting ofice sheets on land. Other effects onoceans includesea ice decline, reducingpH values andoxygen levels, as well as increasedocean stratification. All this can lead to changes ofocean currents, for example a weakening of theAtlantic meridional overturning circulation (AMOC).[15] The main cause of these changes are theemissions of greenhouse gases from human activities, mainly burning offossil fuels anddeforestation.Carbon dioxide andmethane are examples of greenhouse gases. The additionalgreenhouse effect leads toocean warming because the ocean takes up most of the additional heat in theclimate system.[16] The ocean also absorbs some of the extracarbon dioxide that is in the atmosphere. This causes thepH value of the seawater to drop.[17] Scientists estimate that the ocean absorbs about 25% of all human-caused CO2 emissions.[17]
The various layers of the oceans have different temperatures. For example, the water is colder towards the bottom of the ocean. This temperature stratification will increase as the ocean surface warms due to rising air temperatures.[18]: 471 Connected to this is a decline in mixing of the ocean layers, so that warm water stabilises near the surface. A reduction of cold, deepwater circulation follows. The reduced vertical mixing makes it harder for the ocean to absorb heat. So a larger share of future warming goes into the atmosphere and land. One result is an increase in the amount of energy available fortropical cyclones and other storms. Another result is a decrease innutrients for fish in the upper ocean layers. These changes also reduce the ocean's capacity tostore carbon.[19] At the same time, contrasts insalinity are increasing. Salty areas are becoming saltier and fresher areas less salty.[20]The fishing industry sector is a small contributor togreenhouse gas emissions overall but nevertheless there are options for reducing fuel use and greenhouse gas emissions.[7]: v For example, about 0.5 percent of total global CO2 emissions in 2012 were caused byfishing vessels (including inland vessels): 172.3 million tonnes of CO2.[7] When looking at theaquaculture industry, it was estimated that 385 million tonnes of CO2 equivalent (CO2 e) were emitted in 2010. This equates to around 7 percent of the emissions from agriculture.[7]: v
The risingocean acidity makes it more difficult for marine organisms such as shrimp, oysters, or corals to form their shells – a process known ascalcification. Many important animals, such aszooplankton, that forms the base of the marine food chain have calcium shells. Thus the entire marine food web is being altered – there are "cracks in the food chain".[21] As a result, the distribution,[22] productivity, and species composition of globalfish production is changing,[23] generating complex and inter-related impacts[24] on oceans,estuaries,coral reefs,mangroves and sea grass beds that provide habitats and nursery areas for fish. Changing rainfall patterns andwater scarcity is impacting on river and lake fisheries andaquaculture production.[25][26] After the Last Glacial Maximum of about 21,000 years ago, the global average air temperature has risen approximately 3 degrees, leading to an increase in sea temperatures.[27]
Fish catch of the global ocean is expected to decline by 6 percent by 2100 and by 11 percent in tropical zones. Diverse models predict that by 2050, the total global fish catch potential may vary by less than 10 percent depending on the trajectory of greenhouse gas emissions, but with very significant geographical variability. Decreases in both marine and terrestrial production in almost 85 percent of coastal countries analysed are predicted, varying widely in their national capacity to adapt.[28]
Fish populations ofskipjack tuna andbigeye tuna are expected to be displaced further to the east due to the effects of climate change on ocean temperatures and currents.[29] This will shift the fishing grounds toward thePacific islands and away from its primary owner ofMelanesia, disrupting western Pacific canneries, shifting tuna production elsewhere, and having an uncertain effect on food security.[30]
Species that are over-fished, such as the variants ofAtlantic cod, are more susceptible to the effects of climate change. Over-fished populations have less size, genetic diversity, and age than other populations of fish.[31] This makes them more susceptible to environment related stress, including those resulting from climate change. In the case ofAtlantic cod located in theBaltic Sea, which are stressed close to their upper limits, this could lead to consequences related to the population's average size and growth.[32]
Due to climate change, the distribution of zooplankton has changed. Cool water copepod assemblages have moved north because the waters get warmer, they have been replaced by warm water copepods assemblages however it has a lower biomass and certain small species. This movement of copepods could have large impacts on many systems, especially high trophic level fish.[33] For example, Atlantic cod require a diet of large copepods but because they have moved pole-wards morality rates are high and as a result the recruitment of this cod has plummeted.[34]
Increase in water temperature as a result of climate change will alter the productivity of aquatic ecosystems. flourish may be undesirable or even harmful. For example, the large fish predators that require cool water may be lost from smaller lakes as surface water temperature warms, and this may indirectly cause more blooms of nuisance algae, which can reduce water quality and pose potential health problems.[35]
Coastal and fishing populations[37] and countries dependent on fisheries[38] are particularlyvulnerable to climate change. Low-lying countries such as theMaldives[39] andTuvalu are particularly vulnerable and entire communities may become the first climate refugees. Fishing communities inBangladesh are subject not only to sea-level rise, but also flooding and increasedtyphoons. Fishing communities along theMekong river produce over 1 million tons ofbasa fish annually and livelihoods and fish production will suffer fromsaltwater intrusion resulting from rising sea level and dams.[40] In rural Alaska, residents of the Noatak and Selawik villages struggle with unpredictable weather, changes in fish abundance and movement, and boat access changes due to climate change.[41] These impacts significantly impact sustainability and subsistence practices.[41]
Fisheries andaquaculture contribute significantly tofood security and livelihoods. Fish provides essential nutrition for 3 billion people and at least 50% of animal protein and minerals to 400 million people from the poorest countries.[42] This food security is threatened by climate change and the increasing world population. Climate change changes several parameters of the fishing population: availability, stability, access, and utilization.[43] The specific effects of climate change on these parameters will vary widely depending on the characteristics of the area, with some areas benefiting from the shift in trends and some areas being harmed based on the factors of exposure, sensitivity, and ability to respond to said changes. The lack of oxygen in warmer waters will possibly lead to the extinction of aquatic animals[44]
Worldwide food security may not change significantly, however rural and poor populations would be disproportionately and negatively affected based on these criteria, as they lack the resources and manpower to rapidly change their infrastructure and adapt. In Bangladesh, Cambodia, Gambia, Ghana, Sierra Leone or Sri Lanka, the dependency on fish for protein intake is over 50%.[45] Over 500 million people in developing countries depend, directly or indirectly, on fisheries and aquaculture for their livelihoods – aquaculture is the world's fastest growing food production system, growing at 7% annually and fish products are among the most widely traded foods, with more than 37% (by volume) of world production traded internationally.[46]
Human activities also increase the impact of climate change. Human activity has been linked to lake nutrition levels, which high levels are correlated to increasing vulnerability to climate change. Excess nutrients in water bodies, or eutrophication, can result in more algae and plant growth which can be harmful to humans, aquatic communities, and even birds.[47]
Climate change will also have an impact on recreational fisheries and commercial fisheries, as shifts in distribution could lead to changes in popular fishing locations, economic changes in fishing communities, and increased accessibility of fisheries in the North.[48]
The change in temperature and decrease in oxygen is expected to occur too quickly for effectiveadaptation of affected species.[49] Fishes can migrate to cooler places, but there are not always appropriatespawning sites.[49]
A 2025 systematic review of small-scale marine fisheries reported that 67.7% of documented responses to climate- and resource-related shocks were short-term coping strategies, while 32.3% were longer-term adaptive strategies.[50]
Several international agencies, including theWorld Bank and theFood and Agriculture Organization[51] have programs to help countries and communities adapt toglobal warming, for example by developing policies to improve the resilience[52] of natural resources, through assessments of risk and vulnerability, by increasing awareness[53] of climate change impacts and strengthening key institutions, such as for weather forecasting and early warning systems.[54] TheWorld Development Report 2010 – Development and Climate Change, Chapter 3[55] shows that reducing overcapacity infishing fleets and rebuildingfish stocks can both improveresilience to climate change and increase economic returns from marine capture fisheries by US$50 billion per year, while also reducingGHG emissions by fishing fleets. Consequently, removal of subsidies on fuel for fishing can have a double benefit by reducing emissions andoverfishing.[citation needed]
Investment in sustainable aquaculture[56] can buffer water use in agriculture while producing food and diversifying economic activities. Algalbiofuels also show potential asalgae can produce 15-300 times more oil per acre than conventional crops, such as rapeseed, soybeans, or jatropha and marine algae do not require scarce freshwater. Programs such as theGEF-funded Coral Reef Targeted Research provide advice on building resilience and conservingcoral reef ecosystems,[57] while six Pacific countries recently gave a formal undertaking to protect the reefs in abiodiversity hotspot – theCoral Triangle.[58]
The costs and benefits of adaptation are essentially local or national, while the costs of mitigation are essentially national whereas the benefits are global. Some activities generate both mitigation and adaptation benefits, for example, the restoration ofmangrove forests can protect shorelines from erosion and provide breeding grounds for fish while also sequestering carbon[59].[citation needed]
.jpg)
Although there is a decline of fisheries due to climate change, a related cause for this decrease is due to over-fishing.[60] Over-fishing exacerbates the effects of climate change by creating conditions that make a fishing population more sensitive to environmental changes. Studies show that the state of the ocean is causing fisheries to collapse, and in areas where fisheries have not yet collapsed, the amount of over-fishing that is done is having a significant impact on the industry. Fishing that is destructive and unsustainable affects biodiversity.[61] Minimizing over-fishing and destructive fishing will increase Ocean resilience to climate change hence mitigating climate change.
This article incorporates text from afree content work. Licensed under CC BY-SA 3.0 IGO (license statement/permission). Text taken fromIn brief, The State of World Fisheries and Aquaculture, 2018, FAO, FAO.
Text was copied from this source, which is available under aCreative Commons Attribution 4.0 International LicenseArchived 2017-10-16 at theWayback Machine
| |||||||||||||
| |||||||||||||
| |||||||||||||
| |||||||||||||
| |||||||||||||
| |||||||||||||
| |||||||||||||
