Papahānaumokuākea Associated Cetacean Ecology Survey (PACES) Week 3 Field Report

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Overview

by Amanda Bradford, Chief Scientist

The third week of the Papahānaumokuākea Associated Cetacean Ecology Survey (PACES) was a banner one.  While Week 1 brought 15 sightings and 27 acoustic detections of cetaceans, and Week 2 led to 20 sightings and 35 acoustic detections, Week 3 has resulted in 29 sightings and 29 acoustic detections.  To date, we have seen and heard 64 and 91 cetacean groups, respectively, within the Papahāhaumokuākea Marine National Monument (PMNM)!  However, instead of continuing to extol the eyes and ears of our visual and acoustic observation teams, I would like to acknowledge some of the personnel of the NOAA ship Oscar Elton Sette, who have made some rather unique mammal “sightings” of their own.

The PACES tracklines (see below) crisscross through the PMNM such that each night, depending on the amount of trackline covered during the day, we spend some amount of time waiting at the PMNM boundary to begin the following day’s trackline.  One morning, we were surprised to learn that during this waiting period the night watchstanders had “observed” a whale while the rest of us were sleeping.  Our incredulity grew when these observations extended to a unicorn, manatee, and a sea lion balancing a ball!  How, you ask, are such sightings possible in the middle of night in the waters of the Hawaiian Archipelago?  You draw them…with a ship!  Our kudos to LCDR Haner; LT Keesee; ENSs Hoock, Langis, and McVay; and GVAs Asyn, Potts, and Storms for this additional mammal monitoring that kept us (and presumably themselves) very much entertained!

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Nighttime (off-effort) tracks of the NOAA ship Oscar Elton Sette reveal some of the more unusual species encountered during PACES. Photos courtesy of Dawn Breese.

One change to PACES that was implemented this week was the removal of the two westernmost tracklines from the survey grid.  Some unanticipated mechanical difficulties during the previous week slowed our transect progress.  Additionally, the high cetacean sighting rates mean that it has not always been possible to finish each of our daily tracklines.  To ensure that our sampling effort is representative and that we have sufficient time to work with encountered animals, we are focusing our survey efforts on the PMNM waters east of Pearl and Hermes Atoll (see below).

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Planned (left panel) and revised (right panel) PACES tracklines (green zig-zags) within the PMNM (yellow boundary). The two tracklines removed from the transect grid are circled in white.

Visual observations

by Suzanne Yin and Dawn Breese in collaboration with Andrea Bendlin, Justin Garver, Allan Ligon, and Adam Ü

After two weeks of patiently waiting for the weather to turn, the visual observers were rewarded with several days of calm seas.  Each day this week brought multiple sightings of cetaceans with a high of seven sightings on 26 May.  The week started off with multiple sightings of sperm whales and an exciting sighting of killer whales, a species not frequently seen in the tropics.  The killer whales were feeding on some unknown prey species as evidenced by the oily slick and the presence of numerous albatross diving and circling the area.  As the week progressed, sightings were dominated by groups of spotted and striped dolphins.  As the weather continued to improve, several sightings of the ‘cryptic’ species were made: beaked whales and Kogia spp (dwarf and pygmy sperm whales).  One of the Cuvier’s beaked whale groups was seen in close proximity to the ship and was tracked for several hours as the small boat attempted to approach the group for directed sampling.

The calm sea conditions meant that cetaceans were seen at greater distances, occasionally outside of the 3 nmi closing distance (i.e., the distance within which we will approach sightings for species identification and group size estimation).  All of the unidentified cetacean sightings shown below were more than 3 nmi from the trackline with one exception.  The easternmost unidentified small dolphin sighting was made just before sunset, and the dark lighting conditions prevented species identification.  Finally, Week 3 brought two sightings of our priority species, false killer whales.  To date, we have made four sightings of this species.

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Ship-based sightings of cetaceans made on completed tracklines (red lines) during the third week of PACES. Map covers the PMNM (yellow boundary) from Pearl and Hermes Atoll in the west to Gardner Pinnacles in the east.

killerwhale

A group of feeding killer whales was encountered on 21 May approximately 60 km SE of Pearl and Hermes Atoll. Photo by Justin Garver under NMFS permit 15240.

Acoustic monitoring

by Yvonne Barkley in collaboration with Shannon Coates, Patrick Rex, and Jenny Trickey

The passive acoustic team heard a few new species during Week 3, along with some of our favorite regulars.  The table below displays the acoustic detections during Weeks 1-3.  Every week so far, we’ve encountered sperm whales and false killer whales, two very vocal species that have kept us very busy during this survey.

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Summary of ship-based acoustic and visual cetacean detections made during the first three weeks of PACES; sightings with a * were made on 8-9 May before acoustic monitoring began.

We also detected beaked whales galore during Week 3, including a sighting of Cuvier’s beaked whale and an unidentified Mesoplodon.  There were also four “unidentified cetacean” acoustic detections that we presume to be one or more species of beaked whale.  We also heard 13 more sperm whale groups, one of our constant species throughout this survey.  The real highlight of Week 3 was our killer whale sighting and acoustic detection, which possibly represents the first passive acoustic data collected from killer whales sighted in the Hawaiian Archipelago.  The whales produced a 25 kHz downsweep.  We were excited that the killer whales were vocalizing at all because the group seen during our 2010 Hawaiian EEZ survey (sighted on the boundary of the PMNM) was quiet.  We hope to encounter even more new species in our last week of PACES 2013, perhaps rough-toothed dolphins or spinner dolphins. Overall, the passive acoustics team has done a great job monitoring from sunrise to sunset, localizing and tracking vocalizing cetaceans.

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Spectrogram of Cuvier’s beaked whale clicks (A) and unidentified cetacean,
presumably beaked whale, clicks (B) encountered during the third week of PACES.

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Pseudorca vs ‘True’orca: spectrogram of false killer whale whistles
and clicks compared to killer whale downsweeps.

Photo-identification, biopsy sampling, satellite tagging, & small boat surveys

by Erik Norris in collaboration with Andrea Bendlin, Justin Garver, Louise Guiseffi, Allan Ligon, Jenny Trickey, Adam Ü, and Suzanne Yin

Almost 500 photos were taken in Week 3 during nine ship-based sightings of eight cetacean species.  The small boat was launched in association with three of these sightings, including killer whales, Cuvier’s beaked whales, and false killer whales.  The killer whales (21 May, 60 km SE of Pearl and Hermes Atoll) and Cuvier’s beaked whales (24 May, 65 km SW of Laysan Island) were difficult to approach, although photos were taken.  The false killer whale launch on 26 May (75 km SE of Maro Reef) was the most successful.  When this group of about 15 individuals was approached, 175 photo-identification images were taken, one biopsy sample was collected, and a satellite tag (the second for PACES) was deployed.  In total, small boat operations during the third week of PACES spanned just over seven hours and 70 km of effort.  Two additional sperm whale biopsy samples were collected from the ship on 22 May.  These samples are noteworthy because we had tried numerous times over many of the previous 11 sperm whale sightings to obtain biopsy samples, but were not successful.  Finally, though, our patience and teamwork paid off!

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Movements through 27 May of two false killer whales satellite tagged during PACES. The first individual (turquoise track) was tagged off Laysan Island on 15 May. The second individual (orange track) was tagged 75 km SE of Maro Reef on 26 May. These movement tracks are based on raw data, such that some positions may change or be eliminated following appropriate quality checking and data processing.

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After numerous unfruitful attempts to carefully approach the many sperm whales sighted for biopsy sampling, the PACES team celebrates the important results of persistence and teamwork.

Oceanography

by Louise Giuseffi in collaboration with Robert Spina, Erik Norris, and Amanda Bradford

The Oceanography team had a successful third week of sampling.  CTDs were performed 1-2 times per day before sunrise and just after sunset, with daily water samples collected from 12 consecutive depths ranging from the surface to 1,000 m.  XBTs and Surface samples have been collected 3-4 times daily, sometimes overlapping with cetaceans sightings.  The sightings for which we have accompanying oceanography data for this week include: #36 of a sei/Bryde’s whale; #37, #39, #41, and #63 of sperm whales; #40 of killer whales; #42, #46, and #55 of spotted dolphins; #47 of Cuvier’s beaked whales; #56 of Mesoplodon beaked whales; and #61 of an unidentified large whale.

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Summary of oceanography stations during the first three weeks of PACES.

BioTech Louise Giuseffi was performing quality control and entering CTD, XBT, and surface sample data daily.  Survey Tech Robert Spina plotted the CTD sensor data in Ocean Data View 4 (ODV), with a subset of the data pictured below.  ST Spina also graphically compared the Seapoint fluorometer sensor (which records data on the CTD itself) with the water samples we have been manually running through the Turner bench fluorometer for chlorophyll readings.  Comparative chlorophyll readings through Week 3 are plotted on the graph below.

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PACES CTD stations through Week 3, with panels showing chlorophyll content (upper right), temperature (lower left), and dissolved oxygen (lower right) from the surface to 1,000 m.

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Chlorophyll-a values obtained from the Turner bench fluorometer as a function of those obtained from the Seapoint fluorometer sensor on the CTD, with the regression equation and coefficient of determination displayed.

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