Monitoring of cetaceans in the North sea : the RIKZ aerial surveys and the Stena Line ferry surveys

This study involves the analysis of data sources of two structural monitoring programs for cetecean monitoring in the Dutch North Sea. First the RIKZ aerial surveys and second the Stena Line ferry surveys onboard of Stena Line ships.The main research question is what information can both programs supply about: trends in time, distribution, distribution over time, density and population size. This leads to another question: what are the advantages and disadvantages of both monitoring programs and which recommendations can be given. In part I of the report the RIKZ data is analysed for trends in time and distribution. It also explores the possibilities to estimate density and total numbers in Dutch waters. In part II the same analysis is done for the Stena Line data. However, the analysis of the Stena Line data is limited as the program just started and covers only a small part of the North Sea. In part III both programs are evaluated.