Cetacean distribution in relation to oceanographic features at the Kerguelen Plateau

Abstract

The Kerguelen Plateau in the south-eastern Indian Ocean is one of the most isolated and understudied regions on earth. As part of the Kerguelen Plateau Drifts project, Marine Mammal Observer (MMO) data were collected during a seismic survey in the austral summer (January-February 2020). Relationships between observation effort, cetacean sightings, seismic operations, and oceanographic variables-including bathymetry (depth and slope), nutrient concentrations, and indices of primary productivity-were investigated using Generalized Additive Models (GAMs). In total, 354 h and 45 min of observation effort resulted in 191 cetaceans (178 adults and at least 13 juveniles) of nine species observed on 48 occasions, over 14 days along the transect line. Marine mammal sightings occurred in water depths of 624-4699 m, with a hotspot of sightings recorded along the northern flank of the Kerguelen Plateau, in proximity to shelf edges. There was one sighting of a mixed pod of Kerguelen Commerson's dolphins (Cephalorhynchus commersonii kerguelenensis) and dusky dolphins (Lagenorhynchus obscurus), which to the best of our knowledge, is the first confirmed sighting of dusky dolphins in the Kerguelen Islands. Of the nine cetacean species observed, no niche separation was apparent, and all species were observed throughout the survey area. Dissolved oxygen and chlorophyll-a were the most significant predictors of cetacean occurrence. Systematic MMO data combined with synoptic satellite-derived/empirical oceanographic metadata have great potential to facilitate understanding of behaviour, geographical range, and population-status monitoring of cetaceans. This is especially important for cetacean stock assessment and minimising potential acoustic disturbance in Antarctic ecosystems.

Estimating the impacts of climate change on the habitat suitability of common minke whales integrating local adaptation

“…Correspondingly, ice thickness was selected as a predictive factor. Additionally, Todd and Williamson (2022) found that dissolved oxygen and chlorophyll-a concentrations significantly influenced cetacean occurrence; thus, these two factors were included. Hydrographic conditions such as mixing, upwelling, and frontogenesis normally promote high primary productivity, which leads to higher concentrations of prey, attracting more common minke whales to forage in a given area.…”

A High-quality Oxford Nanopore Assembly of the Hourglass Dolphin (Lagenorhynchus cruciger) Genome

“…Although its northernmost range includes Aotearoa New Zealand, where it is considered a taonga (treasured) species by iwi Māori (Māori tribes), the hourglass dolphin is strongly associated with the Antarctic Convergence, and rarely found in close proximity to land masses (Acevedo, Garthe, and González 2017;Dellabianca et al 2012;Santora 2012). Although not an uncommon species (Goodall et al 1997), due to the remoteness and difficulty of surveying Antarctic waters, it is one of the least studied species of dolphin (Dellabianca et al 2012;Goodall et al 1997), with information largely limited to observations from living animals: group size, locality, acoustics, and presence of calves (Goodall 1997;Acevedo, Garthe, and González 2017;Dellabianca et al 2012;Tougaard and Kyhn 2009;Kyhn et al 2009;Thiele, Chester, and Gill 2000;Todd and Williamson 2022).…”