Spatial and temporal distribution of sperm whales (Physeter macrocephalus) within the Kaikoura submarine canyon in relation to oceanographic variables
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The Kaikoura area is a valuable feeding spot for sperm whales with the presence of a submarine canyon close to shore. Male sperm whales can be found there year around, close to the shore and exhibiting almost constant foraging activities. This thesis investigates the distribution and habitat use, both spatially and temporally, of sperm whales (Physeter macrocephalus) within the Kaikoura submarine canyon, New Zealand. The primary aim was to determine which oceanographic variables and bathymetric features influence the sperm whale distribution patterns off Kaikoura. A theodolite was used to track surfacing and movement of sperm whales from a shore-based station. The accuracy of positions recorded by the theodolite was investigated by comparing theodolite measurements of an object of known position. A calibration technique was then developed as the vertical angle was not accurately determined by the theodolite. In addition to investigating the distribution of sperm whales, the daily abundance of sperm whales within the Kaikoura submarine canyon was estimated. Distance sampling and mark-resight models showed an average of 4 (SEM = 0.13) individuals present in the study area at any given time. The mark-resight technique using photo-identification was not possible from a shore-based station so a spatio-temporal model was built in order to track the identity of individuals. The model was tested using photo-identification of sperm whales collected from a boat-based station. Results showed that 88% of the modeled identifications corresponded to the photo-identification database. Sperm whales off Kaikoura were strongly associated with depth, slope and distance from the nearest coast. They were found in waters between 500 m to 1250 m deep and preferred shallower waters in winter. In spring, sperm whales occurred further from the coast, mainly in the Hikurangi Trough, north-east of the shore-based station. Generalized Additive Models (GAM) were used to identify significant oceanographic variables predicting the presence of sperm whales off Kaikoura. Models indicated that sea surface temperature (SST), chlorophylla (Chla) and distance from sea surface temperature fronts were all important parameters in predicting sperm whales presence. Results showed that sperm whales aggregated in the section of the study area with the lowest SST and near SST fronts. This study provides a detailed insight into the use of the Kaikoura submarine canyon by male sperm whales.