Survey for small cetaceans over the Dogger Bank and adjacent areas in summer 2011

Review of New Information on Population Size, Distribution, Structure and Causes of Any Changes. The distribution of small cetaceans in the offshore areas of the North Sea has been in the interest of researchers for many years. Information on abundance and distribution is essential to assess the impact of bycatch and other anthropogenic threats, and as basis for management plans to ensure the favourable conservation status of these species. In 2011 we conducted a dedicated aerial line transect survey of the Dogger Bank and adjacent areas (UK, NL, DK, GE waters) in order to investigate the importance of this marine feature as summer habitat for marine mammals

Survey for small cetaceans over the Dogger Bank and adjacent areas in summer 2011

Review of New Information on Population Size, Distribution, Structure and Causes of Any Changes. The distribution of small cetaceans in the offshore areas of the North Sea has been in the interest of researchers for many years. Information on abundance and distribution is essential to assess the impact of bycatch and other anthropogenic threats, and as basis for management plans to ensure the favourable conservation status of these species. In 2011 we conducted a dedicated aerial line transect survey of the Dogger Bank and adjacent areas (UK, NL, DK, GE waters) in order to investigate the importance of this marine feature as summer habitat for marine mammals

Seabirds as samplers of the marine environment – a case study of northern gannets

Understanding distribution patterns, activities, and foraging behaviours of seabirds requires interdisciplinary approaches. In this paper, we provide examples of the data and analytical procedures from a new study in the German Bight (North Sea) tracking northern gannets (Morus bassanus) at their breeding colony on the island of Heligoland. Individual adult northern gannets were equipped with different types of data loggers for several weeks, measuring geographic positions and other parameters mostly at 3–5 min intervals. Birds flew in all directions from the island to search for food, but most flights targeted areas to the (N)NW (north–northwest) of Heligoland. Foraging trips were remarkably variable in duration and distance; most trips lasted 1–15 h and extended from 3 to 80 km from the breeding colony on Heligoland. Dives of gannets were generally shallow, with more than half of the dives only reaching depths of 1–3 m. The maximum dive depth was 11.4 m. Gannets showed a clear diurnal rhythm in their diving activity, with dives being almost completely restricted to the daylight period. Most flight activity at sea occurred at an altitude between the sea surface and 40 m. Gannets mostly stayed away from the wind farms and passed around them much more frequently than flying through them. Detailed information on individual animals may provide important insights into processes that are not detectable at a community level

Effects of pile-driving on harbour porpoises (Phocoena phocoena) at the first offshore wind farm in Germany

The first offshore wind farm ‘alpha ventus’ in the German North Sea was constructed north east of Borkum ReefGround approximately 45 km north off the German coast in 2008 and 2009 using percussive piling for the foundationsof 12 wind turbines. Visual monitoring of harbour porpoises was conducted prior to as well as during construction andoperation by means of 15 aerial line transect distance sampling surveys, from 2008 to 2010. Static acoustic monitoring(SAM) with echolocation click loggers at 12 positions was performed additionally from 2008 to 2011. SAM deviceswere deployed between 1 and 50 km from the centre of the wind farm. During aerial surveys, 18 600 km of transectlines were covered in two survey areas (10 934 and 11 824 km2) and 1392 harbour porpoise sightings were recorded.Lowest densities were documented during the construction period in 2009. The spatial distribution pattern recorded ontwo aerial surveys three weeks before and exactly during pile-driving points towards a strong avoidance response within20 km distance of the noise source. Generalized additive modelling of SAM data showed a negative impact ofpile-driving on relative porpoise detection rates at eight positions at distances less than 10.8 km. Increased detectionrates were found at two positions at 25 and 50 km distance suggesting that porpoises were displaced towards thesepositions. A pile-driving related behavioural reaction could thus be detected using SAM at a much larger distance than apure avoidance radius would suggest. The first waiting time (interval between porpoise detections of at least 10 min),after piling started, increased with longer piling durations. A gradient in avoidance, a gradual fading of the avoidancereaction with increasing distance from the piling site, is hence most probably a product of an incomplete displacementduring shorter piling events