Feasibility study for a pilot program: catching and tagging harbour porpoises in the Netherlands

• Main Authors: Vrooman, Jip, von Benda-Beckmann, Sander, Geelhoed, Steve, Lam, Frans-Peter
• Format: Report
• Language: English
• Published: Wageningen Marine Research 2024
• Subjects: Life Science; Greenland
• Online Access: https://research.wur.nl/en/publications/feasibility-study-for-a-pilot-program-catching-and-tagging-harbou; https://doi.org/10.18174/654100

In this study the feasibility of tagging harbour porpoises in Dutch waters is evaluated, with the long-term objective to study their large-scale habitat use in the North Sea. Based on a detailed review of available information of tag types and catch methods, and discussions with experts experienced with tagging and handling porpoises it is concluded that tagging of porpoises in Dutch waters is feasible. The study provides recommendations on the catch methods, tag types and methods, potential sites for carrying out tagging, type of additional biological data to collect, as well as a preliminary protocol on how to tag harbour porpoises in Dutch waters. Harbour porpoises are too small to attach tags from a distance (for example by use of a pole or cross-bow), so the animals need to be caught in order to attach the tag. Therefore, different catching approaches were considered: passive and active methods. The active catching strategy ‘surface gillnet herding’ is considered the most feasible in Dutch waters. This method has been applied with success in Denmark and Greenland, and experience is available. It provides the most flexibility in both tag location and timing, maximizing chances for animal presence under suitable environmental conditions. Passive methods were also considered, but they have several drawbacks. As passive methods rely on animals being caught in a net by chance, they require constant monitoring and a tagging team that is on permanent stand-by. Due to the required involvement of experienced Danish researchers and a veterinarian, the project team is not flexible enough to use this method as a starting approach in this pilot project. In the Netherlands, there is currently only one pound net used in the inner Eastern Scheldt, and the probability of catching a harbour porpoises is very small. Catching effort could be increased by constructing more nets, but construction is costly, and once constructed, nets cannot easily be re-located. Because there is no single tag type that will address all research ...