Study

Re-established stony reef attracts harbour porpoises Phocoena phocoena

  • Published source details Mikkelsen L., Mouritsen K.N., Dahl K., Teilmann J. & Tougaard J. (2013) Re-established stony reef attracts harbour porpoises Phocoena phocoena. Marine Ecology Progress Series, 481, 239-248.

Actions

This study is summarised as evidence for the following.

Action Category

Cease or prohibit activities that cause disturbance in sensitive areas for marine and freshwater mammals

Action Link
Marine and Freshwater Mammal Conservation

Restore habitat for marine and freshwater mammals

Action Link
Marine and Freshwater Mammal Conservation
  1. Cease or prohibit activities that cause disturbance in sensitive areas for marine and freshwater mammals

    A before-and-after study in 2006–2012 of a stony reef in the Kattegat sea, Denmark (Mikkelsen et al. 2013) found that prohibiting fishing, along with restoring the reef, resulted in harbour porpoise Phocoena phocoena echolocation clicks being recorded more often and for longer periods than before protection and restoration. The average number of minutes with porpoise recordings and the average duration of porpoise encounters were higher at the reef in each of four years after fishing was prohibited and the reef restored (13–15 minutes/day; 4–5 minutes) than during two years before (6–10 minutes/day; 3 minutes). Porpoise activity at an intact reef 10 km away decreased over the same period (‘before’: 11–15 minutes/day; ‘after’: 3–7 minutes/day). In June–September 2008, a total of 100,000 t of norite boulders were dumped over 19 days to restore a 45,000 m2 cavernous stony reef. Fishing was prohibited around the restored reef in 2009–2012. Porpoise activity was recorded with acoustic data loggers (two at the restored reef; two at an intact reef) for 33–75 days in June–August in each of two years before protection and restoration (2006 and 2007) and each of four years after (2009–2012).

    (Summarised by: Anna Berthinussen)

  2. Restore habitat for marine and freshwater mammals

    A before-and-after study in 2006–2012 of a stony reef in the Kattegat sea, Denmark (Mikkelsen et al. 2013) found that restoring the reef, along with prohibiting fishing, resulted in harbour porpoise Phocoena phocoena echolocation clicks being recorded more often and for longer periods than before restoration and protection. The average number of minutes with porpoise recordings and the average duration of porpoise encounters were higher at the reef in each of four years after the reef was restored and fishing prohibited (13–15 minutes/day; 4–5 minutes) than during two years before (6–10 minutes/day; 3 minutes). Porpoise activity at an intact reef 10 km away decreased over the same period (‘before’: 11–15 minutes/day; ‘after’: 3–7 minutes/day). In June–September 2008, a total of 100,000 t of norite boulders were dumped over 19 days to restore a 45,000 m2 cavernous stony reef. Fishing was prohibited around the restored reef in 2009–2012. Porpoise activity was recorded with acoustic data loggers (two at the restored reef; two at an intact reef) for 33–75 days in June–August in each of two years before restoration and protection (2006 and 2007) and each of four years after (2009–2012).

    (Summarised by: Anna Berthinussen)

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