Passive acoustic monitoring reveals spatiotemporal segregation of two fish-eating killer whale Orcinus orca populations in proposed critical habitat

Abstract

Competition for prey resources among ecologically similar populations that occur in sympatry can be reduced by spatiotemporal resource partitioning. Understanding patterns of habitat use of cetaceans can be difficult since they are highly mobile and can have large home ranges. We used passive acoustic monitoring at 15 sites along the coast of Washington State, USA, to assess habitat use patterns of 2 sympatric populations of fish-eating killer whales Orcinus orca: northern residents (NRKW) and southern residents (SRKW). This area is part of the ocean distributions of a number of important runs of Chinook salmon Oncorhyncus tshawytscha, the preferred prey of both populations, and is proposed critical habitat for SRKW. We compared monthly occurrence of both populations at recorder locations grouped by their proximity to the Strait of Juan de Fuca to the north and the Columbia River to the south in one analysis and by their distance from shore in a second analysis. NRKW and SRKW were detected throughout the year with spring and fall peaks in occurrence. The northernmost sites accounted for 93% of NRKW detections, while less than half of SRKW detections were at these sites. SRKW were most frequently detected at nearshore sites (83% of detections), while the majority of NRKW detections were at mid-shelf and deep sites (94% of detections). This study provides further information about the habitat use of these resident killer whale populations with implications for their management and conservation.

Study on feeding behavior and biological sound of Sebastes schlegelii

“…The PAM technology can be used to monitor the underwater soundscape and collect the vocalization of underwater organisms in indoor and outdoor environments, including fish, marine mammals, crustaceans, etc (Kikuchi et al, 2015;Putland et al, 2018;Emmons et al, 2021;Muñoz-Duque et al, 2021). Aalbers and Drawbridge (2008) proposed that this technology could be combined with behavioral surveillance to make up for its deficiency of non-visualization (Aalbers and Drawbridge, 2008).…”

Identifying drivers of demographic rates in an at‐risk population of marine mammals using integrated population models

“…Interestingly, despite similarities with SRKWs, NRKWs have been thriving over the last several decades in terms of population growth (Appendix S1: Figure S3). Because the range of these two communities overlaps considerably (Emmons et al 2021), it is conceivable that they compete for the same prey fields of adult Chinook salmon throughout the year. Because NRKW abundance data were not available prior to 1972, we (linearly) extrapolated abundance between 1960 and 1971 (Appendix S1: Figure S3) from the existing data (Towers et al 2020), and assumed abundance between 1940 and 1960 was unchanged.…”

“…Interestingly, despite similarities with SRKWs, NRKWs have been thriving over the last several decades in terms of population growth (Appendix S1: Figure S3). Because the range of these two communities overlaps considerably (Emmons et al 2021), it is conceivable that they compete for the same prey fields of adult Chinook salmon throughout the year.…”

Spatial connectivity of reef manta rays across the Raja Ampat archipelago, Indonesia

“…For example, identifying the degree of spatial use overlap between two populations of the same species can provide insights into their reproductive ecology, shared use of key habitats or food resources, or important migratory corridors (e.g. [2][3][4]), from which tailored management strategies can be drawn. An emerging concept transferred from terrestrial ecosystem research to the marine environment is that of a 'metapopulation' [5].…”