The effects of coastal defence structures (tetrapods) on the benthic fish community off Helgoland

lisa.spotowitz [ at ]


Northern Europe’s coastlines are often characterised as high-energy environments exposed to severe wind and storm impacts over the year. Many of these densely populated areas are therefore protected by different kinds of coastal artificial protection measures. Helgoland island, located in the southern North Sea, is protected by over 10 000 tetrapods (4 footed concrete breakwaters) to avoid erosion and land loss over time. Artificial structures like tetrapods are used world wide for coastal protection measures, but there is only limited knowledge available on their influence on the coastal ecosystem and the associated biota. In 2009 the Centre for Scientific Diving of the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Sciences, established a sublittoral experimental tetrapod field (MarGate) to study the effects of artificial constructions on the coastal environment. As in previous investigations SCUBA supported underwater visual census was used to identify fish species, their abundance and to distinguish between young-of-the-year (YOY) and older fish. Fish data have been collected from June to August 2015 on a monthly basis along predefined transect lines with a total of 60 stations. In sum, 785 individuals were assessed and 9 species identified, with Pomatoschistus minutus being the most abundant species. An accumulation of fish, especially of YOY fish near the tetrapods could be shown. This indicates that the submerged tetrapods off Helgoland have been established as enhanced nursery ground and habitat for local fish species. The presented data are part of an ongoing long term assessment project to finally get a better understanding of the role of artificial reefs on coastal ecosystems.

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Spotowitz, L. (2015): The effects of coastal defence structures (tetrapods) on the benthic fish community off Helgoland , Master thesis, University of Rostock.

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