The ocean is affected by more or less regular natural variations. The primary source of food from the oceans is from capture fisheries and aquaculture. The biological productivity which fisheries exploit varies from place to place and over time in relation to oceanographic conditions which change naturally, from year to year and seasonally. Some natural fluctuations are less frequent, changing only after decades.
In addition, the oceanic environment is affected by longterm global climate change caused by a combination of natural processes and human impacts, such as the emission of greenhouse gasses. Any effects of such climate change on fisheries will occur in a sector already characterized on a global scale by full utilization, overcapacity of usage and sharp conflicts between fleets and among competing uses of marine ecosystems.
Environmental variability is a key feature of exploited or pristine ecosystems and has very significant implications for production, development and management of fisheries. The frequency of observed changes and the amplitude of these changes vary widely. Reciprocal influences between natural variation and climate change are not well understood, although it is clear that they both affect fisheries development and management outcomes. Only in the last few years has it become clear that there are climate patterns of a decadal scale that affect production on an ocean basin scale, perhaps even globally for some species. The El Niño phenomenon of 1997-98 provided a primer on oceanography to millions of people around the world. More than 60 countries suffered heavy floods or severe drought as a result of weather anomalies caused, at least in part, by the phenomenon's cyclical warming of surface waters off the coast of Peru. In fact, as information on variability in fish populations accumulates over long periods, it seems that many of the world's largest fish stocks are growing and declining in relative synchrony. The simultaneous rise and fall of sardine (pilchard) populations in widely separate areas of the Pacific Ocean was first pointed out in 1983. Since then, the pattern reported has continued to hold, including an additional episode of a simultaneous pattern change from population growth to abrupt decline. Clearly, no one is yet sure that these ostensible patterns are anything more than fortuitous happenstance, nor has a comprehensive objective analysis been produced. However, there is no doubt that if there does exist a truly effective climatic linkage mechanism which acts to synchronize variability in many of the largest and most important fish populations of the world, it has very interesting and important implications for management of the global fish supply, food security, and for understanding – even predicting – fishery resource variability.
Climate change impacts are likely to amplify natural variations and to exacerbate existing stresses and on marine fish stocks, notably fishing pressure, diminishing wetlands and nursery areas, pollution, and UV-B radiation. In the oceans, climate change is expected to result in increases in sea surface temperature, global sea level rise, decreases in sea-ice cover and changes in salinity, wave conditions, and ocean circulation. On land, climate change, climate change will affect the availability of water, river flow regimes (particularly in floof plains), size of lakes, etc. and the needs of water for other activities competing with fisheries. These changes in turn will have an impact on the biological productivity of aquatic ecosystems and on fisheries. An expected impact of global climate change is an increase in the variability of environmental conditions. Experience already gained in dealing with longer term fluctuations in marine environments, such as those induced by El Niño events, emphasize the need for adaptability. The consequences of El Niño type of phenomena on land are also very significant for inland aquatic resources. As well, ensuring sustainable economic levels of fishing capacity should be determined with the variability in mind. Thus, climate change adds a further argument for developing effective and flexible fisheries management system in an ecosystem context and adopting the Precautionary approach.
Differential effects of climate change
The impact on fisheries of changes in the structure and biological productivity of ecosystems will vary between fisheries and will depend of the specific environmental changes that occur and the particular biological characteristics of each species. Changes in a particular aquatic environment may become conducive to a rapid growth of a high-priced species found in that environment, while the reverse may be true in other instances. In the oceans, where species can easily move, climate change will also result in modifications of the area of distribution of resources which will most likely move towards the North or South pole, whichever is closest. Consequences for the fishing industry could be significant.
Scenarios developed by the Intergovernmental Panel on Climate Change (IPCC) forecast – with indications of "confidence" levels – the following effects:
- Medium Confidence – Globally, saltwater fisheries production is hypothesized to be about the same, or significantly higher, if resource management deficiencies are corrected. Also, globally, freshwater fisheries and aquaculture at mid-to-higher latitudes could benefit from climate change.
- High Confidence – Local shifts in production centres and mixes of species in marine and fresh waters are expected as ecosystems are displaced geographically and changed internally.
- High Confidence – Positive effects such as longer growing seasons, lower natural winter mortality and faster growth rates in higher latitudes may be offset by negative factors such as a changing climate that alters established reproductive patterns, migration routes, and ecosystem relationships.
- High Confidence – Changes in abundance are likely to be more pronounced near major ecosystem boundaries. The rate of climate change may prove a major determinant of the abundance and distribution of new populations. Rapid change due to physical forcing will usually favour production of smaller, low-priced, opportunistic species that discharge large numbers of eggs over long periods.
- There are no compelling data to suggest a confluence of climate-change impacts that would affect global production in either direction.
- High Confidence – Marine stocks that reproduce in freshwater (e.g. salmon) or require reduced estuarine salinity will be affected by changes in temperatures and the amount and timing of precipitation and on species tolerances.
- Medium Confidence – Where ecosystem dominances are changing, economic values can be expected to fall until long-term stability (i.e. at about present amounts of variability) is reached.
- Medium Confidence – Subsistence and other small-scale fishers who lack mobility and alternatives, and are often the most dependent on specific fisheries, will suffer disproportionately from changes.
- Medium Confidence – Because natural variability is so greatly relative to global change, and the time horizon on capital replacement (e.g. ships and plants) is so short, impacts on fisheries can be easily overstated, and there will likely be relatively small economic and food supply consequences so long as no major fish stocks collapse.
The sensitivity to global change will vary between fisheries. The most affected will be fisheries in small rivers and lakes, in regions with larger temperature and precipitation change and on anadromous species. They will be followed by fisheries within Exclusive Economic Zones, particularly where rigid access regulations reduce the mobility of fishers and their capacity to adjust to fluctuations in stock distribution and abundance, fisheries in large rivers and lakes, fisheries in estuaries (particularly where there are species without migration or spawn dispersal) and in the high seas.
More specifically for fisheries, climate change-related warming may result in:
- longer growing seasons and increased rates of biological processes - and often of production;
- greater risk of oxygen depletion;
- species shift to more tolerant of warmer and perhaps less-oxygenated waters;
- redeployment or re-design and relocation of coastal facilities;
- coastal cultures may need to consider the impacts of sea-level rise on facilities and the freeing of contaminants from nearby waste sites;
- changes in precipitation, freshwater flows, and lake levels;
- introduction of new disease organisms or exotic or undesired species;
- establishment of compensating mechanisms or intervention strategies;
- a longer season for production and maintenance; and,
- modification of aquaculture systems, e.g. keeping them indoors under controlled light, may be needed more often to protect larvae from solar UV-B.
In addition, several of the above and other factors, such as competing demand for coastal areas, may argue for technological intensification in ponds and non-coastal facilities.
While the fisheries sector cannot do much to impede or seriously affect global climate change, it could contribute to its stabilization or reduction, and to mitigating its effects. Climate changes notwithstanding, there are several actions to consider. The most important strategies are those needed to promote sustainability and which are useful and practical, even in the absence of climate change. Further, when developing strategies, we need to consider both the problems and the opportunities that are being presented, in the following way:
- active participation at global and regional level, to ongoing debate and collaboration, to obtain the best possible information of fisheries-related impacts;
- allocating research funds to analyze local and regional potential changes in resource magnitude and composition and likely socio-economic impacts;
- sharing information obtained with the sector on potential changes, their scale and possible effects on resources and fisheries;
- establishing institutional mechanisms to enable or enhance the capacity of fishing interests (fleets and other infrastructures) to move within and across national boundaries as a consequence of changes in resources distribution. This implies developing bilateral agreements;
- preparing contingency plans for segments of the sector that might not be able to move, particularly for disadvantaged areas and small-scale fishers lacking mobility and alternatives;
- developing effective national and international scale resource management regimes and associated monitoring systems to facilitate adaptation of exploitation regimes in a shifting environment;
- strengthening regional fisheries management organisation and other mechanisms to deal with cross-border stocks;
- integrating fisheries management into coastal areas management to ensure that fisheries needs are taken up when dealing with protection of coastal areas from sea level rise, etc. For instance, to ensure that public works to protect coastal areas do not unnecessarily obliterate nursery areas important to fisheries;
- analyzing aquaculture sustainability in an ecoregional context, forecasting changes in productivity or resistance and in required related changes in culture systems, cultured species or delocalization of productive systems. Particular attention should be given to coastal investments;
- fostering interdisciplinary research, with scientists meeting periodically to exchange information on observations and research results, and meeting with managers to ensure the proper interpretation of results and the relevance of research; and,
- foreseeing and planning infrastructure adaptations. It could be expected that, in response to shifting populations and species, the industry will respond with faster, longer-range fishing craft, install on-board processing equipment to replace endangered coastal ones or use floating processors when feasible, and find alternative means of transport when coastal roads are flooded and relocation is not possible. Governments should also consider constructing and maintaining appropriate infrastructure for storm forecasting, signalling systems and safe refuges for dealing with possible rising sea level and increased storminess. There may be opportunities to take advantage of reduced need for ice strengthening of vessels and infrastructures in a warmer climate, except perhaps for areas with increased icebergs.
The international activity already related to climate change is very intense as can be seen looking at the various Web sites dealing with it. Most of the action refers, however to research and international agreements. Research focuses on tracking indicators of change, studying cause-effect relationships, modelling, assessing and forecasting impacts. International agreement such as the UN Framework Convention on Climate Change aim at mobilising attention and commitments of governments to reduce greenhouse gases. Little or no action has been taken by governments to mitigate the possible effects, and information on contingency plans is lacking.
In fisheries, while climate change has been addressed occasionally in scientific literature, the subject has not yet been formally addressed by most industry or fishery management administrations. However, the fishery sector and fisheries research are fairly advanced in this matter, through their dealing with the El Niño, decadal changes in ocean environments and other longer terms fluctuations in fisheries environments and resources. The observation programmes, scientific analyses, computer models, the experience gained and strategies developed by fishers, processors, fishfarmers, and management authorities confronted with the problem of medium-to-long-term natural fluctuations, is extremely useful for dealing with climate change. Many of the principles and strategies developed to deal with "unstable" stocks will be of use when having to deal with climate change.
The Global Ocean Observing System (GOOS) has been established under the aegis of IOC-UNESCO.
Changes remain uncertain and competing theories are still developing as to the reality of the change, its magnitude and its mechanisms. Progress in implementing the UN Framework Convention on Climate Change is slow and resistance from some of the major players to pledge reduction of gas emissions remains a stumbling block. It is not possible to forecast how the question will evolve.
Fisheries will be able to move faster towards specific assessments and contingency plans when more precise and reliable predictions are available on projected climate change with at least a regional resolution. In the meantime, dealing effectively with medium-term natural changes offers a good "training field".