Field of Action Fishery

Fishes under waterClick to enlarge
Climate change is an additional stressor for the fish stocks in the North and Baltic Sea.
Source: Susanne Kambor

Impacts of Climate Change

Table of Contents


Impacts of climate change on the sea

By the mid-21st century, the average annual temperature in northern Germany is expected to rise by 1.1 to 2.2 degrees. Along the German Baltic coast, warming of 0.5 to 1.1 degrees within the next 30 years is already. As a result of these changes, seawater temperatures in the North and Baltic seas are also set to rise.

Increasing levels of CO2 in the atmosphere means a greater amount of CO2 in the water, as carbon dioxide is absorbed by the water from the air. This alters the water’s pH-value and makes it more acidic. Extreme weather events causing permanent flooding or increased erosion of coastal areas present a long-term threat to existing habitats. This is somewhat relieved through increasing sea levels, also expected as a result of climate change. The decline in sea ice will also alter temporary habitats.

Due to the changing environmental conditions, fish stocks and populations of other marine species in the North Sea and Baltic Sea are changing. Temporal synchronisation of certain stages of development can be triggered by climate change. As a result, fish larvae for example fail to attain sufficient nourishment. Overall, it is to be expected that known food webs and competitive situations will change. Stress factors such as overfishing, ship traffic or pollutants in the water have a proven negative impact on marine fauna. Therefore, climate impacts cannot always be accurately estimated or distinguished from other factors. However, some trends can be observed:

North Sea
In the North Sea, increased warming leads to a shift in the habitats of many native, cold-water fish species. Cod and plaice, for example, move further to the North where sea temperatures are lower. The Barents Sea has become an increasingly important habitat for cod. Other marine animals have a lower adaptive capacitiy to climate change. Their stocks are expected to decline significantly as a result of warmer winters because these disrupt reproduction cycles or predator-prey relations.

In turn, new species, which were previously located in southern marine areas migrate to the North benefitting from warming water. Examples are the striped mullet, gurnard, or nephrops. In particular the temperature rise during mild winters allows permanent survival of these species in the North Sea.

Baltic Sea
As a brackish water sea, the Baltic Sea particularly depends on the amount of inflowing freshwater from rivers and saltwater from the North Sea. The brackish water environment of the Baltic Sea, which has a mix of both fresh and saltwater, presents particular challenges for the local flora and fauna. These conditions have resulted in fragile ecological balances that are highly sensitive to disruption. This makes the species composition particularly vulnerable - even minor fluctuations in temperature, salt or oxygen conditions can cause significant changes.


Impacts of climate change

Climate change and the changing living conditions of many fish species create new challenges for the fisheries sector, which is of particular importance in structurally weak coastal regions. It is expected that stock fluctuations of individual fish species will continue to rise. The fact that habitats of many fish populations are shifting further north entails considerable economic losses for fisheries. In particular, small, coastal fisheries that are typically financially weak will be affected since northern distribution territories are not as easy to reach. At this stage it cannot yet be fully assessed whether these losses can be compensated by the migration of new species. However, since the beginning of this century, the red mullet has become one of the North Sea’s commercially viable species.

In addition, offshore production sites face the risk of being flooded and damaged due to rising sea levels and more frequent storm surges. Furthermore, higher waves and extreme weather can worsen the fishing conditions at sea.

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Adaptation to Climate Change

Technical measures

A variety of technical options exist to organise the fishery sector in a more sustainable way. Selective fishing techniques, such as stipulated mesh sizes for nets, mean that young animals and species that shouldn’t be caught (non-target species) are protected from unintended removal from the water. New EU fishing policy regulations support a positive development:

  • As of 2019, bycatch of commercially viable species may not be thrown back into the sea. Starting in 2015 this practice will be introduced progressively. Exceptions may still be made in the case of certain species.
  • More effective monitoring of fisheries (for example using automatic locating and identification of ships), as well as the introduction of dissuasive penalties for violations are in planning.
  • Aside from this, modernisation of smaller fishing vessels will, in the near future, be given priority funding.

This means a decrease in disruption to marine habitats and that endangered species will not be further decimated as a result of bycatch. Bycatch of marine mammals or seabirds should also be reduced in the long-term, however there is still no EU-wide regulation for this.

Real-time monitoring of fishing catches can facilitate the establishment of sanctuaries and closed periods. Seasonal and area-related restrictions for fisheries can thus be easily justified.

Ecosystem measures

Ecosystem measures are necessary in order to maintain, restore and stabilise the natural habitats of many fish species in the long-term. Establishing nature reserves and sanctuaries enhances stock resilience to climate change.

Linking migration watercourses such as streams and rivers not only improves habitat, it also helps preserve the biological diversity of fish and microbes. As part of this effort, watercourses shall be restored to their natural state, as restoring natural waters, shores and riverbeds promotes good spawning conditions and creates habitats for indigenous, riverine-typical fish. Via recolonisation, endangered fish species can be maintained and riverine-typical fish stocks can be preserved.

Legal, policy and management measures

An adapted, sustainable fishing industry requires intensive research efforts. Reliable information on fish stocks and their susceptibility, as well as new, more careful fishing techniques are needed. Generating credible prognoses for fisheries is becoming increasingly difficult due to additional uncertainties in terms of climate change. Only with reliable data an understanding of the necessity of adaptation measures can be fostered and planning security of fishing industry can be enhanced. Until this data is available, current, established prognoses for fish stocks and the corresponding restrictive catch quotas should be accepted and implemented according to the precautionary principle.
Based on a sufficient data basis, it would be possible to develop sustainable management and recovery plans for fish stocks that take adequate consideration of their climate-related change processes and susceptibilities. Management plans should consist of adapted catch quotas and closed periods and take non-target species into consideration. Furthermore, climate-related losses should be incorporated and economic plans should define when interventions have to be made to avoid stock declines. The plans should be monitored continually and consistently take actual research results into account.

Targeted regulatory controls at national and European level are necessary to ensure adherence to existing and planned fishery directives, at sea as well as after docking at port. Additionally, it is important for this integrative policy approach to further develop the international monitoring of fish catches and scientifically consolidated quotas for fisheries.

If you are interested in obtaining information about concrete impacts of climate change in the field of action fishery, please click here.