| Between 1970 and 2005 sightings data of cetaceans in the southern North Sea were collected as part of the Marine Mammal Database of the Dutch Seabird Group. The data include incidental sightings and reports as well as results from systematic surveys and seawatching data. They are therefore difficult to correct for fluctuations in observer effort. The material was evaluated firstly to see which species occur in Dutch waters and, secondly, to see if any spatial and temporal trends in abundance can be observed. In this study the harbour porpoise (Phocoena phocoena) is excluded from the analysis, except in the discussion, where the results are put into context with data about strandings and overall abundance. The status of the 17 different species that have... |
