Spatial and seasonal patterns in acoustic detections of sperm whales Physeter macrocephalus along the continental slope in the western North Atlantic Ocean

Abstract

The distribution and seasonal movements of sperm whales Physeter macrocephalus are poorly understood in the western North Atlantic Ocean, despite a long history of human exploitation of the species. Cetacean surveys in this region are typically conducted during the summer, when weather conditions are amenable for visual observation, resulting in a seasonal bias in species occurrence data. In the present study, we conducted multi-year passive acoustic monitoring to assess year-round sperm whale occurrence along the continental slope between Florida and New England, USA. Between 2011 and 2015, we collected 2037 d of recordings using bottom-mounted recorders deployed at 5 sites. We analyzed these recordings for sperm whale echolocation clicks, which were detected commonly between New England and North Carolina, but infrequently off the coast of Florida. In the northern half of the study region, we observed distinct seasonal patterns in the daily prevalence of sperm whale clicks, with a winter peak in occurrence off Cape Hatteras, North Carolina, followed by an increase later in the spring at sites further north. South of Cape Hatteras, seasonal patterns were less apparent. We detected sperm whale clicks during all hours of the day throughout the study area, and did not observe strong diel patterns. Overall, our results provide a comprehensive year-round baseline on the occurrence of sperm whales across multiple recording sites, demonstrating the utility of passive acoustic monitoring to assess patterns in sperm whale occurrence across broad spatial and temporal scales.

Commercial fishing patterns influence odontocete whale-longline interactions in the Southern Ocean

“…Increased fishing effort by vessels in winter coincided with decreased sperm whale interaction levels. This decrease is likely explained by seasonal shifts in the local abundance of mature male sperm whales, possibly driven by ecological and/or reproduction factors, with smaller numbers of individuals found at high latitudes in winter months 41–45 . As a result, lower densities of sperm whales in winter months may contribute to interaction levels being the lowest with vessels at HIMI and South Georgia, which are both primarily winter fisheries.…”

“…However, the natural distribution of the depredating whales is likely to be influenced by a number of other habitat drivers that have characteristics which may differ between areas where fisheries operate. For instance, the distribution of mature male sperm whales at high latitudes was found to be highly correlated with oceanographic variables, such as frontal zones, bathymetric slope and primary productivity likely to drive the abundance and availability of their natural prey items 42,44,45 . These prey items may include Patagonian toothfish but also cephalopods, a resource with a distribution and abundance that is highly influenced by oceanographic processes.…”

Foraging activity of sperm whales (Physeter macrocephalus) off the east coast of New Zealand

“…However, on the island of Kauai, within the Hawaiian Island chain, foraging occured mostly at night at different locations around the island 23 , while in the Mediterranean Sea, sperm whale foraging behavior varied seasonally 24 . Along the east coast of the United States, there was no clear diel pattern present in sperm whale foraging activity at five different sites 25 . Differences in sperm whaleforaging activity at different location might have been driven by variation in the abundance and behavior of their local prey.…”

Clicking throughout the year: sperm whale clicks in relation to environmental conditions off the west coast of South Africa

“…5), which had the longest sampling protocol (single block of 30 min h −1 ). This result suggests that the sampling protocol of an AAR did not appreciatively reduce the probability of sperm whale click detection, as equally observed by Stanistreet et al (2018). Even though AARs 1 and 2 were closely positioned (4.8 km apart) and were recording concurrently for 3 months, they differed during the time of overlap (Fig.…”