Pelorus Sound / Te Hoiere (HS66) Hydrographic Survey Marine Mammal Observations

Discovery Marine Ltd (DML) and iXBlue were contracted in 2019 by Land Information New Zealand (LINZ) to undertake hydrographic surveying services for the Pelorus Sound / Te Hoiere Hydrographic Survey (HS66).
Marine mammals, in particular dolphins are a regular occurrence in the Marlborough Sounds. The species are important both nationally and internationally. There are eight marine mammal species known to frequent the Sounds (Davidson et al., 2011). Two of these are classified as nationally endangered (Hectors and Bottlenose) and one is considered nationally critical (Killer whale or Orca).
DML and iXBlue were contracted to map the seabed in the Marlborough Sounds (Pelorus Sound / Te Hoiere, Admiralty Bay and Te Aumiti (French Pass)) using multibeam sounders. The frequency of the sound emitted by a multibeam echo sounder is outside the hearing range of marine mammals in the Sounds, however as a precaution, best practice for minimising survey activities in the immediate proximity of marine mammals was used, including logging all sightings while on multibeam effort.
Mulitbeam operators and surveyors logged marine mammal sightings. Blue Planet Marine (BPM) was contracted prior to the Queen Charlotte Sound / Tōtaranui and Tory Channel / Kura Te Au Hydrographic Survey (HS51) in 2016/7 to provide a review of the potential efforts of a multibeam survey and make suggestions as to best practice to minimise disturbance. Overall they concluded the survey was in the category of ‘minimal disturbance’ hence not requiring a dedicated MMO onboard (Blue Planet Marine, 2016). This report also gave some recommendations, including survey teams to log sightings, that NIWA adopted in the survey plan used by DML and iXBlue.