The following themes can be listed under this category:
- Ocean acidification (chapter Issues of importance for ecosystem based management - Pollution)
- Mixed fisheries, undersized fish, discard, bycatches and IUU fishing (chapter Issues of importance for ecosystem based management - Fisheries)
- Impact of bottom trawling on benthos (chapter Issues of importance for ecosystem based management - Fisheries)
- Implementing the ecosystem approach to fisheries (chapter Issues of importance for ecosystem based management - Fisheries)
Ocean acidification caused by increasing atmospheric C02 concentrations is an emerging problem, and is discussed in detail in chapter Current and expected state of the ecosystem - Some aspects of possible long-term future changes in the ecosystem. The most important direct effects of acidification will be on organisms that calcify. This includes important groups of phytoplankton, zooplankton and benthos. Other groups, such as fish, marine mammals and seabirds may be affected indirectly through changes in their food base and other changes in the ecosystem. As discussed in chapter Current and expected state of the ecosystem - Some aspects of possible long-term future changes in the ecosystem, the overall impact from ocean acidification may become considerable.
The second theme addresses several effects of fisheries on the ecosystem. For example, mixed fisheries may lead to overfishing of quotas because if the quota of one target species is taken, catch of this species may be discarded when fishing for other target species continues. This is in particular a problem in mixed cod and haddock fisheries. Species that need protection, in particular redfish and coastal cod, may be overfished because they are taken as bycatch in other fisheries. There are also some reports of bycatches of sea mammals and seabirds in fish nets. IUU fishing on the cod stock was a serious problem some years ago, but is now considered to be less serious.
Impact from bottom trawling on benthos has been clearly documented, but the extent of the problem has not been revealed. Thus, it is not clear whether or how biodiversity and ecosystems processes are affected. Effect on benthos from trawling is described and discussed in chapter General background description of the ecosystem - Ecosystem interactions - Human impact.
Implementing the ecosystem approach to fisheries is listed as a theme here because changes in the ecosystem may influence the impact of fisheries management on fish stocks. For example, the capelin quota considered sustainable depends on the size of the cod stock, because cod consumes considerable amounts of capelin (see chapter General background description of the ecosystem - Ecosystem interactions - Biotic impact). In a similar fashion, variation in climatic factors may affect productivity in the ecosystem (see chapter General background description of the ecosystem - Ecosystem interactions - Abiotic impact) and hence ultimately fish stocks.
