Adaptation: Field of Action Fishery

Sustainable fisheries management: A sustainable orientation of sea fishing and the implementation of conservation measures can relieve marine ecosystems affected by climate change and increase their resilience. Future climate changes should therefore already be taken into account today in fishing quotas and target fish species. Measures such as the introduction of closed fishing seasons (e. g. in years when fish stocks suffer from extreme water temperatures), the establishment of additional marine protected areas, smaller fishing fleets and more selective fishing methods are necessary to allow fish stocks to recover. Pre-set mesh sizes for fishing nets help to protect juveniles and species that are not intended to be caught from being accidentally taken out of the water. Rules in EU fisheries policy on bycatch or fisheries control support this development. By-catches of commercially exploited fish species may no longer be thrown back into the sea as of 2019, although exemptions are possible for certain species. By promoting the modernisation of smaller fishing vessels, disturbances in the marine habitat are to be reduced. More effective monitoring of fisheries and the creation of deterrent penalties for infringements are envisaged.

Protection and maintenance of habitats: The protection of habitats in the North Sea and Baltic Sea is an important goal in order to maintain the reproductive capacity of all species naturally occurring there. This can go hand in hand with improving the reproductive capacity of commercially exploited fish populations and increasing the buffer capacity against possible climate change. Genetically diverse populations and species-rich ecosystems have a greater potential to adapt to climate change. Healthy stocks with large populations can also respond better to population shifts and changes in ecosystem structures. With the implementation of the European Marine Strategy Framework Directive (MSFD) and the National Strategy for the Sustainable Use and Protection of the Seas (National Marine Strategy), the German government has set itself the goal of maintaining or achieving a good state of the marine environment in the North Sea and Baltic Sea.

Monitoring and research: The change in marine fishing potential in higher latitudes initially also creates new opportunities for fishing. In order to participate, fishery management would need to incorporate such opportunities into fish stock management in a timely manner and address fleet capacity adaptation. The impacts of climate change on fisheries cannot yet be quantitatively predicted. A significant research effort is still needed, also to derive concrete options for action. Part of this is precise observation (monitoring) of spatial and temporal shifts in fish stocks and changes in species communities. Regular processing of the fish species relevant for national catch statistics (e. g. cod, herring, sprat, plaice, salmon, sea trout) allows stock parameters such as abundance, biomass and age structure as well as the distribution patterns of the fish to be determined. Within the framework of the "German Small-scale Bottom Trawl Survey" (GSBTS), standardised catches are carried out annually in defined areas of the North Sea. The aim is to estimate the natural variability of catch rates of various fish species and to record medium- to long-term changes in fish communities. Real-time monitoring of catches could support the establishment of closed areas and seasons. Seasonal and area-based restrictions on fishing could thus be well justified. Fisheries research faces the challenge that climate change adds another complex component to its stock forecasts. Research must therefore be intensified and focus more on the adaptation needs of fisheries.

Establishing sustainable management plans and monitoring: Based on a good data basis, it is possible to develop sustainable management and recovery plans for fish stocks that adequately take into account their climate-induced change processes and vulnerabilities. For this purpose, management plans should include adapted catch quotas and closed seasons and also take non-target species into account. In addition, it is important to include climate-related failures and to specify in the management plans when to intervene in case of stock declines. The plans must be continuously reviewed and updated if necessary. Regulatory controls at the national and European level are necessary to ensure compliance with fisheries regulations, both at sea and in port. In addition, it is important to further develop international monitoring of fishing and the allocation of quotas for fishing.

Adapting sea fisheries to new fish species: If new fish species, such as the anchovy, continue to establish themselves in German sea waters as water temperatures continue to rise, it would make sense to adapt the German fishing fleet to these and other immigrating species. The cost of converting or upgrading the German fleet for anchovy fishing varies depending on the type of vessel and the fishing method. For vessels that already fish pelagic species such as herring or mackerel, conversion to anchovy would not require much effort. It may be necessary to adapt the nets to the smaller species. For the use of vessels that previously fished demersal species or shrimp, the conversion would involve more effort and higher costs. The usual flexibility of fishermen in seeking new fishing grounds and other species can also be considered an adaptation strategy.

In order to counteract the effects of extreme weather conditions such as heat stress and low water phases and long-term effects of climate change, long-term measures must be developed that maintain the functionality of water bodies and sustainably protect the flora and fauna of the habitats. In particular, ecosystem and river engineering adaptation measures can contribute to maintaining, restoring and stabilising the natural habitats of many fish species in inland waters in the long term. These include the establishment of protected areas, the renaturation of natural water bodies and the creation of connectivity and ecological passability of water bodies. Monitoring and research are central, too.

Adaptation and establishment of protected areas: Climate change will alter and shift habitat conditions and thus suitable habitats for fish. In order to increase the resilience of fish stocks in inland waters to climate change, it is necessary in the medium term to adapt current protected areas and concepts, not only for fish, to the changes caused by climate change and, if necessary, to designate new protected areas and quiet zones for inland waters.

Renaturation: Another approach to dealing with climate change is the ecological improvement of inland waters. Measures to rehabilitate and renaturalise rivers, streams and lakes will enable fish to cope with climatic stresses in the future, at least to a certain extent. Thus, renaturation of natural water bodies, bank and bed structures at running waters creates habitats for native, watercourse-typical fish species, offers them thermal retreat opportunities and promotes good spawning conditions. In order to limit the heating up of small water bodies during the summer months, the natural emergence of riparian woody plants should be maintained and promoted through coordinated water body maintenance and the creation of sufficiently wide, unmanaged riparian strips. And where necessary and possible, new plantings should also be made to shade the water bodies. Crown cover provides shade for water bodies and direct heat radiation can be significantly reduced. The requirements of the Water Framework Directive (WFD) can be used to establish ecological areas such as riparian strips. The potential permanent loss of structures in the shore region of lakes can also be counteracted by renaturation measures. With appropriate habitat enhancement (e. g. through the creation of new shallow water zones), mortality among juvenile fish can be reduced, reproduction promoted and thus fish stocks stabilised overall.

Passability and connectivity: A further input of warmth into flowing waters can occur through anthropogenic dam areas (e. g. regulating structures, dams, piping). They increase the residence time of the water body by reducing the flow velocity. As a result, the water can warm up more and lead to thermal stress for fish in the backwater area and downstream. Therefore, it makes sense to dissolve non-natural dam areas - if possible - and to normalise the discharge of the water bodies again. On the one hand, this leads to a reduction in water temperature (especially during heat periods), and on the other hand, the flowing waters become passable again for aquatic life, especially for cold-loving fish species that are closely tied to free-flowing streams and rivers. The adaptation of fish species in running waters also depends on the spatial alternatives available in the event of rising water temperatures, low water quality and more frequent low water levels. The interconnection of migratable running waters can contribute to fish being able to migrate to the cooler running water sections in the upper reaches. At suitable running water sections where cold water enters (e. g. groundwater inflows, colder confluences), a short-term "cold water refuge" can be created by excavating deep sections.

For the most part, the listed adaptation measures have positive side effects, such as protection against flooding due to high water or heavy rainfall events, as well as contributions to achieving a "good ecological status" of water bodies. Functioning riparian strips with sufficient planting next to the direct riparian area of inland waters help to reduce the input of dissolved substances and material pollution into the water body (e. g. from agriculture) during heavy rainfall events. The better the ecological condition of a watercourse system and the higher its structural diversity, the higher its adaptability to climatic changes.

Monitoring and research: For all inland waters, long-term monitoring and research can help develop viable adaptation strategies. Key regions of inland fisheries should be monitored, e. g. for yields, invasive species as well as changing intensities of use (e.g. tourism). To better understand the impacts of climate change on fisheries, climate impact and adaptation research should also be intensified, including the identification of the vulnerability of fish stocks, studies on the adaptive capacity of fish and the suitability of measures to stabilise fish stocks.

Emergency measures and regulations: During heat periods with increased water temperatures and low oxygen concentrations, acute measures with special equipment can be initiated to ensure aeration of the water body (e.g. by fire brigades and technical relief organisations). For stretches of water where the continued existence of fish stocks can no longer be guaranteed, emergency fishing and relocation measures by local fishing associations and volunteers can be considered. As a rule, the fish are placed in sections of the same waters that are less affected by heat, in the hope that they will migrate back to their original habitats when conditions ease. In extreme heat periods, when water levels and discharges of flowing waters are low, special ecologically derived rules should be developed in addition to the existing regulations for water use and abstraction, which take into account the acute risk situation of fish and other aquatic organisms. In the context of eutrophication of inland waters, it has become even more important to address the reduction of material loads, especially nutrient inputs from agriculture. Regulations on the maintenance and creation of riparian strips are important here. In anticipation of climate change-related changes in spawning and hatching times, adapted closed seasons are another promising approach. The same applies to removal regulations. If growth and the onset of sexual maturity change, adjustments to minimum sizes or supplementary withdrawal regulations could be effective in stabilising recruitment and increasing reproduction rates. Refuge areas for fish can be realised through the designation of closed areas.

Resettlement and fish stocking: With the help of resettlement measures, endangered fish species can be preserved and fish stocks typical of water bodies can be protected. In connection with the promotion of water retention in the landscape, the possibility should be examined to what extent, where new water landscapes are created; these could also be used for fish production.

The aquaculture sector will also have to adapt to the negative impacts of climate change and increase its resilience. Measures that aquaculture farms can take include shading of production sites, use of aeration equipment or oxygen input systems, multiple use of water, selection of suitable fish species, and temporal adaptation, among others.

Shading and enclosure of production sites: To avoid critical water temperatures during prolonged hot spells, shading by trees and/or enclosing or roofing over the fish-holding units is useful in open-air facilities. Another approach is aquaculture photovoltaics, whose solar modules, mounted above the breeding ponds, provide shading and enable energy generation for the operation of the water circulation technology.

Use of flow-through, aeration and water treatment systems: High water temperatures and oxygen shortages in the holding units of trout pond farms can be counteracted by technical flow-through and aeration systems (oxygen input systems). For carp pond farms, improved production conditions can be assumed in principle, as higher water temperatures and a longer growing season favour fish growth. It is possible, however, that due to increased evaporation from large pond areas and prolonged drought, challenges may also arise regionally with regard to sufficient water supply, especially if the pond systems are fed from small inflows. In the future, it will be crucial in aquaculture to ensure a sufficient water supply all year round. In terms of sustainable aquaculture, it is therefore necessary to further develop and use water-saving methods to reduce dependence on rainwater. Existing flow-through systems could be converted into (partial) recirculation systems that provide for multiple uses with integrated mechanical and biological treatment of the water.

Reduced water supply: Water temperatures in fish farms (e.g. trout farms) are kept low by feeding cooler, oxygen-rich water into the system during heat periods. This requires a permanent availability of cool water, especially if there is no recirculation and thus multiple use of the water. It becomes problematic for aquaculture farms if the acquisition of new water rights or the extension of existing ones is not possible. A relocation of fish farms to new locations on a larger scale is rather unlikely, as the approval of new locations is also handled restrictively in many regions of Germany. If temperatures continue to rise, fish farming in aquacultures could thus become uneconomical in parts of Germany, as the supply of cool, oxygen-rich water becomes increasingly costly. Decreasing water availability due to climate change would also have an unfavourable impact on carp farming.

Switching to other fish species: If the temperature is permanently too high, the production of certain fish species in aquacultures will be associated with high technical effort or failure. The fish species to be cultivated must be critically examined and, if necessary, re-evaluated. Switching to other, warmth-loving fish species is another way of adapting to climate change. To this end, the testing and introduction of adapted high-quality fish species for aquaculture should be supported through research and funding. However, it is essential to pay attention to the risk of spreading potentially invasive species.

Adjusting the timing of production: It is conceivable to shift fish production to the colder seasons in order to avoid hot temperatures in summer. Winters are now much milder, so sufficient growth in fish could be achieved.