Funding for this research was provided by:
fisheries tax of Schleswig-Holstein, Germany
Article History
Received: 29 September 2017
Revised: 26 January 2018
Accepted: 29 January 2018
First Online: 9 February 2018
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.
: All applicable international, national and/or institutional guidelines for the care and use of animals were followed by the authors.
: All necessary permits for sampling and observational field studies have been obtained by the authors from the competent authorities and are mentioned in the acknowledgements, if applicable.