HICEAS 2017: Two Ships, Rare Beaked Whales and a Mystery Click in Hawaiian Waters

By early September 2017, the Hawaiian Islands Cetacean and Ecosystem Assessment Survey (HICEAS) had two NOAA ships at work: the Oscar Elton Sette on its second leg, and the Reuben Lasker, which had sailed nearly 9 days and about 2,000 nautical miles from San Diego to join it.

The Sette's second leg

From 8 August to 5 September, 29 days, the Sette surveyed the north of the study area, from above the main islands to beyond Midway and across the International Date Line. The weather was unusually kind: most of its 2,315 nmi of daytime effort was in Beaufort sea state 4 or less, rare under the steady trade winds, and calmer water made whales and dolphins easier to see, 70 groups in all. There were also calm days with nothing seen or heard, far from land between the seamounts: much of this ocean is a "tropical desert," too poor in nutrients to support many cetaceans.

The Sette’s Leg 2 track (white) and sightings in the Hawaiian EEZ (blue line); the main-islands focus area in red, the monument in green, darker where it was expanded in 2016. NOAA Fisheries.

Sightings. At least 13 species, from the small spinner dolphin to the large Bryde's whale. Striped dolphins were seen most, 14 times; short-finned pilot whales 10; most others once or twice. The highlights were beaked whales, elusive and hard to detect: two sightings of the rare, little-known Longman's beaked whale, one group of almost 100, and a small group of Blainville's beaked whales that approached the ship again and again during a long spell at the surface.

Samples. Almost 10,000 photos from the ship and seven small-boat launches; 33 biopsy samples from spotted, rough-toothed and bottlenose dolphins and pilot whales; satellite tags on three pilot whales; and 6 hexacopter flights over pilot whales.

Listening and the sea. The acoustics team detected 127 vocal groups, released seven drifting recorders and recovered three full ones from Leg 1, and deployed 43 sonobuoys for baleen whales. The ship made 35 CTD casts.

Seabirds. Thousands of sightings of at least 35 species, with five new for the survey: Herald/Henderson's petrel, flesh-footed and sooty shearwaters, parasitic jaeger and Pacific golden plover. The plovers, kōlea in Hawaiian, were returning from summer in Alaska to wintering grounds in Hawaiʻi, where they come back to the same spot, even the same yard, each year.

Striped dolphins. NOAA Fisheries (Permit #20311).

Short-finned pilot whales. NOAA Fisheries (Permit #20311).

Pilot whales photographed from a hexacopter. NOAA Fisheries (Permit #20311).

A Pacific golden plover. NOAA Fisheries (Permit #MB033305-0).

The Lasker's first leg

The Lasker left San Diego on 17 August. To reach Hawaiʻi quickly, observers worked in passing mode, not leaving the trackline for sightings, as the air and water warmed, tropical seabirds appeared and the trade winds set in. It reached the study area before dawn on 26 August and switched to closing mode, turning toward sightings for better identification and counts, surveying south and east of the main islands until 5 September. In 20 days it covered 1,844 nmi of daytime effort, 696 of them in Hawaiian waters, and saw 53 cetacean groups, 34 in the study area.

The Lasker’s transit and Leg 1 effort and sightings. NOAA Fisheries.

Those 34 sightings were of 10 identified species, all also seen by the Sette except the pygmy killer whale. The team took two biopsies, from a spotted and a rough-toothed dolphin, and saw Longman's beaked whales three times. Other highlights came by ear:

• Killer whales at night. About 10 pm one night, with the towed hydrophones recording but nobody listening, faint calls appeared on a monitor. Through headphones, the team heard killer whales calling for over an hour, too dark to see.
• The Cross Seamount beaked whale. Known only from recordings first made at Cross Seamount, its long, upswept clicks sound unlike any beaked whale whose calls are known. The team tracked it by sound for over an hour before dusk; just before dark, the lead observer glimpsed a cetacean that might have been it: not a confirmation, but a step closer.

In all, acoustics logged 106 detections and picked up 2 drifting recorders. Seabird observers counted 4,916 birds of at least 15 species in 28 feeding flocks, and 1,830 birds of at least 42 species on their transects.

False killer whales. NOAA Fisheries (Permit #20311).

Two Duke University graduate students joined as visiting scientists, one on each ship. Both ships sailed again on 11 September.

Sources

• NOAA Fisheries, "The HICEAS Adventures Continue: Two Ships Join Forces to Search for Whales and Dolphins in Hawaiian Waters"; rewritten in hubnx's own words. Photographs and maps: NOAA Fisheries. Team photographs naming individuals are not reproduced here.