Hawai‘i Tuna Longliners Near Limit on False Killer Whales

posted in: August 2021, Fisheries | 0

As the working group convened by the Scientific and Statistical Committee of the Western Pacific Fishery ManagementCouncil developed its criticisms of measures intended to reduce the bycatch of false killer whales by the Hawai‘i longline fleet, actual interactions between the longliners and false killer whales in waters around Hawai‘i have been increasing.

As of mid-July, nine interactions had been observed. Of the three that occurred inside the U.S. Exclusive Economic Zone (EEZ), two were determined to have resulted in serious injury to the animals involved, while one resulted in its death. Of the six that occurred beyond the 200-mile boundary of the EEZ, preliminary determinations are that five resulted in serious injury; one has been preliminarily determined to have been non-serious.

Under the Take Reduction Plan approved by the National Marine Fisheries Service, the take – representing the mortality or serious injury of an animal (M&SI) – of false killer whales caught inside the EEZ can be no more than 16 per year before restrictions on fishing grounds are put into place. That number is the so-called Potential Biological Removal (PBR) set under the Marine Mammal Protection Act – the level of harm that can be sustained by a population of marine mammals without its chances for recovery being jeopardized.

The PBR is calculated not by the number of animals that are taken in the presence of on-board observers, but by multiplying the number of observed takes that are judged to be serious or deadly by the fraction of the fleet on which observers are placed.

Until COVID-19 hit, that percentage was 20, or one-fifth of the deep-set longline fleet that targets bigeye tuna. The M&SI of three observed animals within the EEZ would extrapolate to 15 animals killed or seriously injured fleetwide, just one below the actual number taken so far this year.

Since the pandemic hit, the percentage of coverage has been closer to 15 percent, or between a sixth and a seventh of the fleet. With that level of coverage, three animals killed or seriously injured extrapolates to between 18 and 21 for the total fleet.

However, Mike Tosatto, administrator of the NMFS’ Pacific Islands Regional Office, said that in 2020, observer rates were increasing, so the extrapolation rate remains based on an observer rate of 20 percent.

In 2019, when the calculated rate of M&SI exceeded PBR, it led to the closure of the southern exclusion zone (SEZ), an area south of the Main Hawaiian Islands that represents about 17 percent of the total available fishing grounds for longliners within the EEZ.

The SEZ was reopened last August and has not been closed yet for 2021.

The Interactions

The SEZ had been opened just a few months when the first two false killer whale interactions of 2021 were observed on January 4, both outside the EEZ. The same vessel was involved in both interactions.

In the first case, at around 7:20 p.m., the animal surfaced and the crew grabbed the line, but, according to a NMFS summary, “the line broke while in the hands of the crew … before any action could be taken.” “The hook, weight, leader, and 1.9 m[eter] of line remained on the whale,” the observer noted.

The second interaction occurred about two hours later. “The crew took the line in hand and were struggling to pull in enough line to tie off,” the NMFS report states. “At that point, the captain arrived on deck and instructed the crew to tie off the line to the cleat. Once the line was tied off, it broke. The whale was hooked in the mouth and the observer could see the leader but not the hook. The observer noted the whale’s behavior as struggling and distressed throughout the interaction. After the line broke, the whale dove and was not seen again. The hook, weight, leader, and 1 m of line remained on the whale.”

Both of these interactions have been given a preliminary determination as serious injury.

The third interaction of the year occurred two weeks later, on January 18, inside the EEZ. In that case, 12 meters of line remained on the whale. This was given a final determination by NMFS as a serious injury.

In March, another interaction inside the EEZ was classified as serious. In this case, “the line was leading towards the mouth, but it was not clear if the hook was in the mouth or ingested. The crew attempted to tie off the line, when the line suddenly snapped and broke. The hook, weight, leader, and 8.9 m of branchline remained on the animal.”

The third interaction noted inside the EEZ occurred on April 17 and resulted in the animal’s death. “A false killer whale came up tail first and unresponsive, with the mainline and multiple branchlines (observer estimated 7 branchlines) entangled around the fluke,” the NMFS report states. “Several hooks were embedded in the animal.”

From May 6 to June 17, four more interactions were recorded by observers, all occurring outside the EEZ. No final determinations had been made for these interactions as of mid-July. However, three of these four were preliminarily classified as serious.

— Patricia Tummons

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