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Killer Whale Action In False Bay


Fishery interactions are one of the main threats facing this species. False killer whales are known to depredate (take fish and bait off of fishing lines), which can lead to hooking and/or entanglement. This is especially a concern for false killer whales that interact with the Hawaiʻi longline fishery.




Killer whale action in False Bay



Due to its very small population size (less than 200 individuals) and population decline until at least the early 2000s, the main Hawaiian Islands insular false killer whale distinct population segment (DPS) is listed as endangered under the Endangered Species Act. It is the only false killer whale population protected under the ESA. This stock is also listed as depleted under the Marine Mammal Protection Act (MMPA).


The endangered main Hawaiian Islands insular false killer whale distinct population segment (DPS) is estimated to number less than 200. The historical population size is unknown, though spotter planes in the late 1980s observed large aggregations of 350 to 400 whales in a single area. Aerial survey sightings since then suggest that the main Hawaiian Islands insular false killer whale population declined at an average rate of 9 percent per year through at least the early 2000s. The current population trend is unknown.


Sighting data collected from ship-based, line-transect surveys conducted by NOAA Fisheries within the central Pacific Ocean between 1986 to 2017 uses a model-based approach to estimate the Hawaiʻi pelagic population of false killer whales to be roughly 2,115 individuals. Their historical population size is also unknown, though interactions with longline fisheries are known to have killed or seriously injured animals in this population since at least the late 1990s. There have been only three large-scale surveys in Hawaiian waters, and changes in survey design (intended to provide more precise estimates given the social structure and behavior of false killer whales) make it difficult to determine trends in abundance for this pelagic population.


The Northwestern Hawaiian Islands, northern Gulf of Mexico, and western North Atlantic stocks (populations) of false killer whales are not as well-studied. Current population abundance estimates for all stocks (Northwestern Hawaiian Islands, the northern Gulf of Mexico, and the western North Atlantic) can be found in the latest marine mammal stock assessment reports.


False killer whales are large members of the dolphin family. They are dark gray, often appearing black on all but a small part of their ventral (underside) surface, which is lighter between the pectoral fins running from the throat down to the belly.


False killer whales are gregarious and form strong social bonds. They are often found in relatively small subgroups of a single to a few individuals that are associated with a larger aggregation that may spread over tens of kilometers. These strong social bonds between groups and dispersion into small subgroups likely help them find prey.


When they capture prey, many individuals tend to converge, and their prey items may be shared among several animals in the group. In Hawaiʻi, these larger aggregations may include 40 to 50 animals, whereas larger groups have been observed in other regions. They are known to strand in groups as well. In some regions, false killer whales are also found with other cetaceans (whales and dolphins), most notably bottlenose dolphins.


Although the range of the main Hawaiian Islands insular false killer whale partially overlaps with the ranges of the Hawaiʻi pelagic and Northwestern Hawaiian Islands populations, genetic analyses, photo-identification, and social network analyses indicate that the main Hawaiian Islands insular false killer whale population consists of a tight social network that is socially unconnected with the other two Hawaiʻi-based populations.


In addition to the social structure found among all three Hawaiian false killer whale populations, there is significant social structure within the main Hawaiian Islands insular population. A social network analysis indicates that this population can be broadly divided into five primary social clusters.


False killer whales are top predators that primarily hunt fish and squid. They feed both during the day and at night, hunt in dispersed subgroups, and converge when prey is captured. Prey sharing has also been observed among individuals in the group.


False killer whales can dive for up to 18 minutes and swim at high speeds to capture prey at depths of 300 to 500 meters. They often leap completely out of the water, particularly when attacking certain prey species. In Hawaiʻi, they are also known to throw fish high into the air before consuming them.


False killer whales occur in tropical, subtropical, and temperate waters of all ocean basins. In the United States, they are found around Hawaiʻi, in all Pacific Remote Island Areas, the Mariana Archipelago, and in American Samoa, as well in the Gulf of Mexico and in the warm Gulf Stream waters off the East Coast. False killer whales have been observed off the U.S. West Coast as far north as British Columbia, Canada, typically during warmer oceanographic regimes.


Female false killer whales reach sexual maturity between the ages of 8 and 11, while males mature 8 to 10 years later. Gestation ranges from 11 to 16 months, and lactation occurs for 1.5 to 2 years. Time between births is unknown but is estimated to be around 7 years. Female false killer whales enter menopause and become less reproductively successful between 44 and 55 years old.


Prey items for false killer whales are similar to many of the same species that fisheries target. This is particularly true in Hawaiʻi, where preferred fish for both false killer whales and consumers are tuna, billfish, wahoo, and mahimahi.


We are committed to conserving and protecting all populations of false killer whales. We are especially committed to protecting populations in Hawaiʻi, including recovering the endangered main Hawaiian Islands insular false killer whale. Our work to protect and conserve this species includes:


We conduct various research activities on the biology, genetics, behavior, and ecology of false killer whales, with an emphasis on populations of the species in Hawaiʻi. The results of this research inform management decisions for all false killer whales and enhance recovery efforts for the endangered main Hawaiian Islands insular false killer whale DPS. Our work includes:


Three populations or stocks of false killer whales occur in Hawaiʻi: the Northwestern Hawaiian Islands population, the pelagic population, and the endangered main Hawaiian Islands insular population.


Population boundary descriptions are complex but can be summarized as follows. The waters from shore from Kauaʻi and Niʻihau to Hawaiʻi Island out to the main Hawaiian Islands insular population boundary are considered an overlap zone between the main Hawaiian Islands insular and pelagic populations. The entirety of the Northwestern Hawaiian Islands population range is an overlap zone between Northwestern Hawaiian Islands and pelagic false killer whales. All three populations overlap from shore around Kauaʻi and Niʻihau out to the main Hawaiian Islands insular population boundary.


All false killer whales are protected under the Marine Mammal Protection Act (MMPA). The main Hawaiian Islands insular false killer whale is protected under both the Endangered Species Act (ESA) and the MMPA. NOAA Fisheries has taken steps to reduce incidental serious injury and death of false killer whales in the Hawaiʻi-based deep-set and shallow-set longline commercial fisheries. NOAA Fisheries also designated critical habitat for the endangered main Hawaiian Islands insular false killer whale in 2018. A Final Recovery Plan and associated Recovery Implementation Strategy for the Main Hawaiian Islands Insular False Killer Whale were published on November 3, 2021.


All false killer whales that reside in the United States are protected under the MMPA. Although there are three populations or stocks of false killer whales in Hawaiian waters, only the main Hawaiian Islands insular false killer whale is listed as depleted (i.e., they have fallen below their optimum sustainable population level). Under the MMPA, the False Killer Whale Take Reduction Plan addresses the threat of incidental serious injury and death of false killer whales in the Hawai'i-based deep-set and shallow-set longline fisheries.


On November 17, 2010, NOAA Fisheries completed a status review of the main Hawaiian Islands insular false killer whale and proposed to list it as an endangered DPS under the ESA. Read the ESA status review report.


NOAA Fisheries conducts research on the biology, behavior, ecology, and genetics of false killer whales, with a special focus on Hawaiian false killer whales. We use the results of this research to inform management decisions, further direct scientific research, and enhance conservation and recovery efforts for the species.


In collaboration with fishermen of the Hawaiʻi longline deep-set fishery, we conduct research to investigate interactions between false killer whales and fishing gear. We deploy small, autonomous acoustic recorders on longline fishing gear to acoustically monitor fishing sets for the presence of false killer whales. We compare the acoustic presence of false killer whales to fishing activity and depredation rates to assess vessel and gear sounds and false killer whale occurrence and behavior around gear, as well as to identify potential acoustic cues.


Until recently, great whites and broadnose sevengill sharks occupied the top of the food chain in False Bay, South Africa. But there are two new sheriffs in town: killer whales named Port and Starboard, so named because their dorsal fins hang to the left and right respectively.


There are two different ecotypes of killer whales, one that eats mainly mammals and fish, and the other that preys mainly upon sharks in offshore waters. Scientists think that Port and Starboard may have belonged to a pod of killer whales specializing in hunting sharks and larger fish, such as tuna and swordfish, in offshore waters. It is unusual that they have come into coastal waters, and researchers suspect they are hunting here due to shark overfishing and environmental changes. 350c69d7ab


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