CV17041 A multidisciplinary approach to studying deep diving whales and their habitat

A multidisciplinary approach to studying deep diving whales and their habitat. Operations will be 24 hours therefore acoustic tows will be taking place day and night. Visual operations will only take place during daylight hours. Due to the daily vertical migration cycle of these deep species where fish and cephalopods migrate into shallower waters during night time and back to depths during daylight combined with the Voyagers limitation of trawling to 400m we will be carrying out all our fishing activities on deck between dusk and dawn. We will use a mid-water trawl to a depth of 400m although we can also consider using a nueston net to slightly deeper depths. In addition, CTDs and plankton tows will be carried out at regular intervals along transects. If these stations fall during night time hours then these will be carried out then also. The three main aims of this survey are: i) To investigate the fine scale distribution and habitat use of deep diving whales, particularly beaked and sperm whales. ii) To improve species identification of beaked whales and to update current species description of beaked whales within Irish waters. iii) To investigate the food chain of deep diving whales in Ireland and their link to oceanographic and topographic features of interest. Scientific Objectives The proposed survey has 8 objectives 1) To employ sightings-based survey design to model the distribution of deep diving whales in the study area 2) to calculate abundance and distribution of beaked and sperm whales in this region using towed acoustic hydrophones, and to characterise their acoustic behaviour 3) To investigate the abundance and biomass of mesopelagic fish species and squid, the main prey sources for beaked and sperm whales 4) To take high quality images of beaked whales that can be used for species identification and to update our knowledge of species occurrence in Irish waters for future surveys 5) to characterise the oceanography data of the study area and better understand water movements 6) to understand the role of zooplankton in this deep-water ecosystem.