Abstract
SEAMARCO and Van Oord Dredging and Marine Contractors have developed the FaunaGuard-PM (FGPM) to deter harbour porpoises from localised offshore anthropogenic activities in order to minimize potential negative effects of these activities on porpoise hearing. The efficiency of the FG-PM was tested in a pool and the distance up to which it would deter porpoises in the field has been modelled, but was not tested at sea. The aim of this study was to test and evaluate the efficiency of the FG-PM to deter porpoises under field conditions. Porpoise behaviour was studied by simultaneous visual observations and passive acoustic monitoring in the vicinity of a periodically active FG-PM in the Marsdiep, Western Dutch Wadden Sea, in February-April 2016.
Visual observations and passive acoustic monitoring took place during a series of pre-exposure (at least 1 h FG-PM off), exposure (15 min FG-PM on) and post-exposure experiments (up to 2 hrs FG-PM off). Visual observations and continuous video recordings were made from a vantage point on the southern tip of Texel. CPODs were stationed at different distances from the FG-PM to record unseen underwater activity of harbour porpoises acoustically.
The visual observations showed that the FG-PM deterred harbour porpoises up to distances of at least 1000 meters. Most of the acoustic monitoring data during FG-PM exposure experiments corroborated the expected results, but due to equipment failure most of these data were of limited value. During post-exposure, shortly after the FG-PM was turned off, harbour porpoises were detected again in the vicinity of the FG-PM.
This study confirms that the FG-PM is successful in deterring harbour porpoises up to at least 1000 m in the field conditions studied, and that porpoises were seen in the exposed area shortly after the FGPM was deactivated.