Denise Risch, Ursula Siebert and Sofie M. Van Parijs
Information on individual calling behaviour and source levels are important for understanding acoustically mediated social interactions of marine mammals, for which visual observations are difficult to obtain. Our study, conducted in the Stellwagen Bank National Marine Sanctuary (SBNMS), located in the Gulf of Maine, USA, used passive acoustic arrays to track North Atlantic minke whales and assess the sound production behaviour of individuals. A total of 18 minke whales were acoustically tracked in this study. Individual calling rates were variable, with a median intercall interval (ICI) of 60.3 s. Average source levels (SLrms) for minke whales pulse trains ranged between 164 and 168 dB re 1 μPa, resulting in a minimum detection range of 0.4–10.2 km for these calls in this urban, coastal environment. All tracked animals were actively swimming at a speed of 5.0 ± 1.2 km/h, which matches swimming speeds of migrating minke whales from other areas and confirms SBNMS as part of the migration route of this species in the Western North Atlantic. Tracked minke whales produced 7 discrete call types belonging to 3 main categories, yet no individual produced all call types. Instead, minke whales produced 2 multisyllabic call sequences (A and B) by combining 3–4 different call types in a non-random order. While 7 of the tracked individuals produced calling pattern A, 10 whales used calling pattern B, and only 1 animal combined call types differently. Animals producing different call sequences were in acoustic range of one another on several occasions, suggesting they may use these sequences for mediating social interactions. The fact that the same calling patterns were shared by several individuals suggests that these patterns may contain information related to sex, age or behavioural context.
Monika Krivickaite, Ursula Siebert, Helena Herr, Alexander Proelss and Anita Gilles
This article explores the legal regime of the protection of marine species and habitats within European waters by taking the protection of harbour porpoises in the German territorial sea and exclusive economic zone as an example. The analysis is based on a scientific assessment of the occurrence of and the anthropogenic impacts on harbour porpoises in the North Sea. The relationship between the protection of marine species within the European Union (EU) on the one hand and the Common Fisheries Policy of the EU on the other constitutes a classic example of a user-environment conflict. The article explores how such conflicts ought to be solved under the pertinent legal rules.