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Climate change could benefit some Pacific fisheries, but tracking the success of adaptation needs effective monitoring, says Johann Bell.
Bottom-dwelling coastal fish are expected to be hardest hit. Under continued high emissions of greenhouse gases, stocks of these fish are estimated to decrease by 20 per cent by 2050 due to global warming and ocean acidification, which affect the fish themselves as well as the coral reefs that support them.
But much uncertainty remains about the impacts of climate change. And contrary to assessments for some other parts of the world, the projections for fisheries and aquaculture in the Pacific are not all negative.
In particular, tuna stocks are expected to rise in the eastern Pacific, and increased rainfall is likely to improve the production of freshwater fisheries and pond aquaculture in the western Pacific.
Indeed, many communities could switch their fishing efforts to tuna that frequent coastal waters. By installing anchored fish aggregating devices (FADs) to temporarily hold tuna, small-scale fishers could access these valuable resources more easily.
Building networks of inshore FADs to increase coastal communities’ access to tuna is an example of a ‘win-win adaptation’: it will help supply the additional fish needed by growing populations in ways that are likely to be favoured by climate change.
Governments should strengthen investments in monitoring the success of such ‘win-win adaptations’. Effective monitoring will be key to ensuring that the most appropriate adaptations are applied at the right times and in the right places.
There are technologies available to help managers monitor the effects of fishing and climate change on coastal fish stocks. For example, digital photography and image analysis can simplify sampling to determine species composition and the size of catches landed at fish markets, providing a baseline against which change can be measured.
In addition, governments routinely conduct household and income expenditure surveys which could be modified to assess the success of efforts to increase the proportion of tuna in the catch of coastal communities.
Simple methods for collecting remotely-sensed data, and ground-truthing this information, also have a role to play in separating the effects of climate change from other stressors on the coral reef habitats that support fish stocks.
Regular mapping of vegetation cover in water catchment areas will also be needed to monitor the success of revegetation programmes designed to prevent sediments and nutrients from degrading coral reefs fringing the coast.
But existing monitoring tools are not in place for coastal fisheries in many PICTs. Even the basic information required for fisheries management, such as the relative abundance and sizes of fish landed at main markets, is often missing.
And although the technology underpinning some of the priority adaptations to climate change is mature, interventions will not work in all PICTs, or in all locations within a country. Additional surveys and planning will be needed to identify sites with the appropriate conditions.
For example, in the case of FADs, information is needed from local communities to identify areas frequented by tuna, and which parts of these areas are suitable for installing the devices.
Alongside these efforts, training programmes are needed to improve the technical skills of coastal communities that are adapting to climate change by increasing their tuna catches and engaging in pond aquaculture. The training should extend to improving post-harvest methods to increase the shelf life of fish caught and produced in remote areas.
PICTs will need to invest in a variety of monitoring programmes to improve their understanding of industrial tuna fisheries. The returns could be significant, if not vital — industrial fisheries contribute 10–40 per cent of government revenue in four PICTs, and 10–20 per cent of gross domestic product in two PICTs. Tuna canneries also provide 12,000 jobs across the region.
There are key improvements that governments should make as a matter of priority. Observer programmes that currently monitor fishing practices on industrial tuna fleets need to be expanded to help provide the basic biological data needed to better understand the function of ecosystems that support tuna, and to determine whether these ecosystems are being affected by fishing and the changing climate.
Investing in more comprehensive observer programmes that improve the quantity and quality of data will also help to build and validate the biophysical models needed to assess the potential production of tuna across the Pacific.
And new technology is needed onboard purse-seine fishing vessels (boats that surround schools of tuna with large nets). For example, digital images would help record changes in the species composition and size of the tuna caught by different fleets, and from different areas of the Pacific Ocean.
Such data should preferably be processed by computers on board, and transmitted to the Pacific Islands Forum Fisheries Agency and Secretariat of the Pacific Community via the vessel monitoring system.
The necessary tools and capabilities for long-term monitoring programmes must be developed as soon as possible — the longer the data are available, the greater the power to detect change and provide the information needed for adaptive management.
Johann Bell is Principal Fisheries Scientist at the Secretariat of the Pacific Community, based in New Caledonia. He is lead editor of the book Vulnerability of Tropical Pacific Fisheries and Aquaculture to Climate Change.