Essential fish habitats (EFH)
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Essential fish habitats (EFH)

Conclusions from a workshop on the importance, mapping, monitoring, threats and conservation of coastal EFH in the Baltic Sea

Many fish species in the Baltic Sea are dependent on shallow and sheltered near-shore habitats for their spawning, nursery, feeding and migration. Still, the role of these essential fish habitats, EFH, for the development and support for fish production has received little attention. As coastal EFH often are found in areas heavily impacted by humans, they are subject to many threats and therefore management needs are urgent. EFH also provide and support important ecosystem services and are included in national/international agreements and legislative acts. Despite this, the conservation status of EFH is generally poor in the region. Due to these shortcomings and needs, a workshop was set up to review the importance and protection of as well as threats to coastal EFH in the Baltic Sea. This report describes the outcome of the workshop and future directions for work in this research area.

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Author(s):
Nordic Council of Ministers

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The Baltic Sea is relatively shallow in relation to its size, and the coastal zone constitutes a large and ecologically important part of the system. The environmental status of many coastal areas of the Baltic Sea has declined during recent decades, partly as a result of increased eutrophication, but also due to climate change, coastal development and the introduction of non-indigenous species. Many studies report that evident changes in species composition of coastal fish and benthic communities have taken place during the past 30–40 years (e.g. Olsson et al. 2012, 2013a, Rousi et al. 2013, Snickars et al. 2015, Weigel et al. 2015). The habitat quality of shallow coastal ecosystems is also affected by non-indigenous species especially in inner coastal areas, since most of these species are originally spread by vessels (Katsenevakis et al. 2014, Ojaveer and Kotta 2014). In addition, evidence is accumulating for the occurrence of trophic cascades in the coastal system. In areas where populations of coastal predatory fish such as perch (Perca fluviatilis) and pike (Esox lucius) are weak, mesopredatory fish, such as the three-spined stickleback (Gasterosteus aculeatus), are present in high numbers (Eriksson et al. 2009, 2011, Bergström et al. 2015, Byström et al. 2015). These mesopredators can have substantial impacts on the community of invertebrate grazers, reducing their numbers and hence the grazing pressure on algae, ultimately leading to eutrophication symptoms and habitat changes with blooms of ephemeral filamentous algae (Korpinen and Jormalainen 2007, Baden et al. 2010, Sieben et al. 2011, Östman et al. 2016). Sticklebacks may also affect the egg and larval stages of many species of predatory fish negatively, further emphasizing this problem (Bergström et al. 2015; Byström et al. 2015).