False killer whale (Pseudorca crassidens) echolocation and acoustic disruption: implications for longline bycatch and depredation

False killer whales ( Pseudorca crassidens (Owen, 1846)) depredate fish caught by the North Pacific pelagic longline fishery, resulting in loss of target species catch and the whales themselves becoming bycaught. This incidental take of false killer whales exceeds sustainable levels. In an effort to address a potential solution to reducing this depredation and bycatch, we tested an acoustic device designed to deter false killer whales from approaching longlines by reducing the whales’ echolocation performance capabilities. The device produced a series of complex, broadband signals (1–250 kHz) at high intensity levels (up to 182 dB). In the experiment, a trained false killer whale was asked to detect a target in the presence or absence of the acoustic device. Baseline performance capabilities were 95% correct responses. Initially, the device reduced the whale’s echolocation performance to chance levels. However, subsequent sessions demonstrated improvement in echolocation performance up to 85%. This improvement was likely a result of behaviorally adapting to the task and a decrease in the source level of the echolocation “disruptor”. The results underscore the challenges in using acoustic devices to reduce depredation and bycatch, and demonstrate the need for concern regarding anthropogenic noise levels and effects on odontocete echolocation capabilities.

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Preliminary findings of restriction fragment differences in mitochondrial DNA among killer whales (Orcinus orca)

Canadian Journal of Zoology ◽

10.1139/z89-365 ◽

1989 ◽

Vol 67 (10) ◽

pp. 2592-2595 ◽

Cited By ~ 21

Author(s):

Tracy A. Stevens ◽

Deborah A. Duffield ◽

Edward D. Asper ◽

K. Gilbey Hewlett ◽

Al Bolz ◽

...

Keyword(s):

Mitochondrial Dna ◽

North Atlantic ◽

North Pacific ◽

Killer Whale ◽

Vancouver Island ◽

Restriction Pattern ◽

Orcinus Orca ◽

Killer Whales ◽

The North ◽

The North Pacific

A preliminary assessment of mitochondrial DNA restriction patterns in the killer whale (Orcinus orca) was conducted using 10 captive North Atlantic killer whales from the southeastern coast of Iceland, a captive-born offspring of one of these whales, and 9 North Pacific killer whales. No restriction pattern variation was seen among these whales, using the enzymes BamH I, Bgl II, Hinf I, Kpn I, or Pvu II. Restriction pattern variation was found using the enzyme Hae III. This restriction endonuclease distinguished the North Atlantic killer whales (type 1) from the North Pacific killer whales. The North Pacific killer whales were further differentiated into two groups: those originating from the "resident" communities of the Vancouver Island region (type 2), and those from the "transient" community of Vancouver Island, as well as those stranded along the Oregon coast (type 3). The observed Hae III restriction pattern differences suggest that mitochondrial DNA analysis will be a valuable technique for investigating regional and local distributions of maternal lineages among killer whale pods, especially in the North Pacific.

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The abundance of false killer whale, Pseudorca crassidens (Artiodactyla: Delphinidae) in coastal waters of Golfo Dulce and Osa Peninsula, Costa Rica

Revista de Biología Tropical ◽

10.15517/rbt.v68i2.37196 ◽

2020 ◽

Vol 68 (2) ◽

Author(s):

Erika Sánchez Robledo ◽

Lenin Enrique Oviedo Correa ◽

David Herra-Miranda ◽

Juan Diego Pacheco-Polanco ◽

Sierra Goodman ◽

...

Keyword(s):

Costa Rica ◽

Population Size ◽

Killer Whale ◽

Small Population ◽

Killer Whales ◽

Apparent Survival ◽

Osa Peninsula ◽

Small Population Size ◽

False Killer Whale ◽

Pseudorca Crassidens

Introduction: False killer whale (Pseudorca crassidens) is a tropical and subtropical social species that live in groups with individuals of mixed ages and sex classes. False killer whales have been documented since the late 1990s in Southwestern Costa Rica. Objective: To estimate the abundance of false killer whales in Osa Peninsula waters. Methods: Cetacean surveys off the Osa Peninsula Waters (OPW), Costa Rica, yielded opportunistic encounters with false killer whales in Drake Bay and Caño Island (2001-2015) and observations during formal surveys in Golfo Dulce (2005-2015). Photo-identification data was analyzed using capture-mark-recapture models in the study area, through an open population (POPAN) framework, considering the effect of time on the parameters apparent survival and capture probability, producing an abundance estimate for a superpopulation in the entire study area. Results: False killer whale abundance in OPW is characterized by a small population size of no more than 100 individuals, complemented by a very low probability of encounter and a contrasting high apparent survival. Conclusions: This population estimate should be taken as conservative, however, the small population size of less than 100 individuals should be considered vulnerable, in contrast to the increasing anthropogenic impacts in the coastal seascape. We argue the potential occurrence of population units along the coastal seascape of the Pacific littoral and oceanic island-associated units at Isla del Coco.

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Depredation by killer whale (Orcinus orca) and false killer whale (Pseudorca crassidens) on the catch of the Uruguayan pelagic longline fishery in Southwestern Atlantic Ocean

ICES Journal of Marine Science ◽

10.1093/icesjms/fsu251 ◽

2015 ◽

Vol 72 (5) ◽

pp. 1653-1666 ◽

Cited By ~ 11

Author(s):

Cecilia Passadore ◽

Andrés Domingo ◽

Eduardo R. Secchi

Keyword(s):

Atlantic Ocean ◽

Killer Whale ◽

Orcinus Orca ◽

Longline Fishery ◽

Southwestern Atlantic ◽

Killer Whales ◽

Southwestern Atlantic Ocean ◽

Pelagic Longline Fishery ◽

Pseudorca Crassidens ◽

Pelagic Longline

Abstract This study analyses depredation by killer whales (Orcinus orca) and false killer whales (Pseudorca crassidens) on catches of the Uruguayan pelagic longline fishery in the Southwestern Atlantic Ocean between 1998 and 2007. Data were collected by scientific observers from the National Observer Program of the Tuna Fleet operating in the area between 19°–40.5°S and 20°–54°W. Depredation occurred in 67 of the 1029 sets and was restricted to the area from 25°–40.5°S to 27°–53°W, though larger proportions of depredation (DP: percentage of total fish caught damaged by cetaceans) were observed in the Brazil–Malvinas (Falkland) Confluence area (34°–37°S and 51°–53°W) where most of the fishing effort was concentrated. Depredation occurred year-round though intra-annual variability in its intensity was recorded. The overall DP was 0.37% and was slightly higher in autumn. The spatial analysis showed that DP within grids of 1 × 1° was homogeneous and generally <2.5%. Ten out of 57 fish species caught by the fishery were depredated by cetaceans. Swordfish (Xiphias gladius) showed the highest DP per species (1.17%). Using the frequency of resources selectivity index of Ivlev, it was determined that swordfish was selected as a preferred prey in 43.9% of the sets with depredation. Generalized linear models indicated that distance to coast, year, and vessel were significant variables in explaining the number of fish depredated per fishing event. The presence of killer whales in the fishing ground seems not to affect the catch per unit effort by the longline fishery. The losses caused by depredation of cetaceans on the catch are low with probably minor economic effects to the Uruguayan longline fishing industry.

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A Case of Chronic Purulent Pneumonia in False Killer Whale (Pseudorca crassidens)

Japanese Journal of Zoo and Wildlife Medicine ◽

10.5686/jjzwm.10.117 ◽

2005 ◽

Vol 10 (2) ◽

pp. 117-122 ◽

Cited By ~ 1

Author(s):

Fumio TERASAWA ◽

Kimimasa TAKAHASHI ◽

Isao OHSHITA ◽

Masakazu KITAMURA

Keyword(s):

Killer Whale ◽

False Killer Whale ◽

Pseudorca Crassidens

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Prey switching by killer whales in the north-east Atlantic: observational evidence and experimental insights

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315413001707 ◽

2013 ◽

Vol 94 (6) ◽

pp. 1357-1365 ◽

Cited By ~ 18

Author(s):

Dag Vongraven ◽

Anna Bisther

Keyword(s):

Killer Whale ◽

Large Population ◽

Tooth Wear ◽

Killer Whales ◽

Prey Switching ◽

Photo Identification ◽

North East ◽

The North ◽

Spawning Stock

Studies in the Pacific have identified distinct killer whale ecotypes that are either specialized mammal- or fish-eaters. The different types have developed hunting strategies that would suggest specialization could be more advantageous than generalism. However, it has been suggested, based on long-term dietary markers of tooth wear and stable isotope values, that lineages in the North Atlantic are generalist, but with individual variation in the proportion of prey types consumed. Here, we present the results of ten years of observational and photo-identification data of a population of killer whales that follows the Norwegian spring-spawning stock of Atlantic herring. Although the whales were predominantly observed while feeding upon herring, one pod of herring-eating whales was also observed interacting with seals. This supports the hypothesis based on the long-term markers, of a degree of specialization, with a small number of groups persistently feeding upon mammals, but switching between herring and seals. We further investigated this prey switching by conducting playbacks of herring-eating killer whale sounds to harbour seals at haul-out sites on the herring spawning grounds. We recorded changes in behaviour consistent with an anti-predator response, suggesting the seals perceived the herring-eating killer whales as a potential predatory threat and had not habituated to their calls. This could be due to the risk of herring-eating killer whales switching to mammalian prey, or the difficulty of discriminating between killer whale pods due to the large population size and number of killer whale call dialects in this population, or a combination of both.

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