DTIC ADA570875: Open-Ocean Movements of a Satellite-Tagged Blainville's Beaked Whale (Mesoplodon densirostris): Evidence for an Offshore Population in Hawaii?

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Aquatic Mammals 2011, 37(4), 506-511, DOI 10.1578/AM.37.4.2011.506
Short Note

Open-Ocean Movements of a Satellite-Tagged Blainville’s Beaked Whale
(Mesoplodon densirostris): Evidence for an Offshore Population in Hawai‘i?
Robin W. Baird,1 Gregory S. Schorr,1 Daniel L. Webster,1 Sabre D. Mahaffy,1
Daniel J. McSweeney,2 M. Bradley Hanson,3 and Russel D. Andrews4
1Cascadia Research Collective, 218½ W. 4th Avenue, Olympia, WA 98501, USA
E-mail: [email protected]
2Wild Whale Research Foundation, Box 139, Holualoa, HI 96725, USA
3NOAA Northwest Fisheries Science Center,
2725 Montlake Boulevard E, Seattle, WA 98112, USA
4School of Fisheries and Ocean Sciences, University of Alaska Fairbanks,
and Alaska SeaLife Center, 301 Railway Avenue, Seward, AK 99664, USA
In Hawaiian waters, a single stock of Blainville’s (Schorr et al., 2009). Combined with long-term
beaked whale (Mesoplodon densirostris) is recog- resightings of distinctive individuals off the island
nized, extending throughout the U.S. Exclusive (McSweeney et al., 2007), such results suggest the
Economic Zone (EEZ) surrounding the archi- existence of an island-resident population. Mark-
pelago and into adjacent international waters recapture population estimates based on photo-
(Carretta et al., 2011). Abundance within the identification data suggest this island-resident
entire EEZ around Hawai‘i was estimated at population is quite small, with approximately 140
2,872 individuals based on a large vessel sight- individual Blainville’s beaked whales (CV = 0.30)
ing survey (Barlow, 2006), with a single on-effort using the area off the island of Hawai‘i over a 4-y
sighting near the western boundary of the EEZ period (Baird et al., 2009b).
(Hamilton et al., 2009). There is, however, con- While Blainville’s beaked whales are gener-
siderable uncertainty associated with this estimate ally thought to be distributed throughout tropical
(CV = 1.17; Barlow, 2006), and there is recent oceanic waters (Jefferson et al., 2008), research
evidence that individuals documented around efforts to examine movements and spatial use
the main Hawaiian Islands may not be part of an have focused on studies of animals around oceanic
open-ocean population (McSweeney et al., 2007; islands (Claridge, 2004; Schorr et al., 2009; Tyack
Schorr et al., 2009). Individual Blainville’s beaked et al., 2011). Nothing is known of the movements
whales instrumented with satellite tags off the or habitat use of individual Blainville’s beaked
island of Hawai‘i have remained strongly associ- whales in the open ocean, away from island habitats.
ated with the island, primarily using slope habi- In Hawaiian waters, there have been few sightings
tats for the entire duration of satellite tag trans- of Blainville’s beaked whales in the open ocean
missions (up to 71 d; Schorr et al., 2009). Schorr (Carretta et al., 2011), and thus limited opportuni-
et al. (2009) noted a mean distance from shore of ties to study this species in such habitats. Here, we
16.9 km (range 4.4 to 27.7 km) and a mean depth report on the movements of a Blainville’s beaked
of 1,156 m (range 880 to 1,455 m) for six satel- whale satellite tagged off the island of Hawai‘i
lite tagged individuals, over periods ranging from but thought to be from an open-ocean population,
15 to 71 d (median = 43 d), with from 26 to 405 rather than the resident island-associated popula-
locations per individual (median = 195 locations/ tion. Using photo-identification data on this spe-
individual). Although these individuals moved cies in the area since 1986 (McSweeney et al.,
a cumulative distance of at least 8,000 km over 2007) and sighting information from our study of
the duration of their tag attachments, median odontocetes off the island since 2002 (Baird et al.,
distances of locations from the tagging location 2008, 2009a), we compare sighting characteristics
for the different individuals ranged from 19.9 to and photo-identification results from the tagged
91.8 km, and the maximum distance any individual group with other sightings of Blainville’s beaked
moved from where it was tagged was only 139 km
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Open-Ocean Movements of a Satellite-Tagged Blainville’s Beaked Whale
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(Mesoplodon densirostris): Evidence for an Offshore Population in
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Beaked Whale Open -Ocean Movements 507
whales and discuss the management implications side of the island of Hawai‘i (19.24° N,
of our results. 156.18° W). This was the second deepest group
The tag used was a location-only LIMPET sat- and fourth farthest from shore of the 29 groups
ellite tag (see Andrews et al., 2008; Schorr et al., documented. A LIMPET tag was attached to
2009). Details of the tag configuration and deploy- the dorsal fin of one individual, identified as an
ment system, as well as data processing, can be adult male based on the presence of erupted teeth.
found in Andrews et al. (2008) and Schorr et al. Reaction to tagging consisted of a fast dive, while
(2009), so they are only briefly mentioned here. none of the other individuals in the group reacted.
The tag was set up to transmit 10 h/d during peri- Both left and right sides of all three individuals in
ods that corresponded to the highest density of sat- the group encountered 29 April 2009 were well-
ellite overpasses, with a limit of 300 transmissions photographed, and all three were distinctive, with
per day. These 10 h of on-time were in four blocks numerous scars to allow for long-term individual
ranging from 2 to 3 h in duration, with intervals of identification. Photos of all three were compared to
2 to 5 h in between transmission periods. Satellite a catalog of 115 distinctive individual Blainville’s
locations were assessed for plausibility with the beaked whales that had been documented around
Douglas Argos-filter, Version 7.06 (available at the main Hawaiian Islands (see McSweeney
Alaska.usgs.gov/science/biology/spatial/douglas. et al., 2007). Neither the tagged individual, des-
html). Horizontal rate of movement calculations ignated HIMd153 in our catalog, nor the other
were restricted to pairs of locations from 4 to two individuals present (HIMd152 and HIMd154
24 h apart for comparison with analyses of Schorr in our catalog), had been previously documented
et al. (2009). Depths and distances from shore photographically.
of sightings and filtered satellite locations were Five of the 27 sightings with photo-identified
determined using ArcGIS, Version 9.2 (ESRI, individuals (including the 29 April 2009 group)
Redlands, CA, USA). Filtered locations were were either in depths > 2,100 m or at distances
plotted in conjunction with offshore eddy sys- > 35 km from shore, and none of the photo-iden-
tems using output from the Archiving, Validation, tified individuals from these groups were docu-
and Interpretation of Satellite Oceanographic mented on more than one occasion (i.e., they had
(AVISO) data (see www.aviso.oceanobs.com/en/ not been seen prior to or since these encounters).
data/products/sea-surface-height-products/global/ Only one of the 22 sightings in less than 2,100 m
index.html). AVISO data were available as weekly depth and within 35 km of shore was entirely com-
means of sea surface height (SSH) at 0.25° × 0.25° posed of photo-identified individuals that had not
resolution and geostrophic currents at 0.5° × 0.5° been seen on more than one occasion (i.e., did not
resolution. link by association to the known resident island-
Blainville’s beaked whales were encountered associated population). The high proportion of
on 29 occasions during directed research sur- groups (21 of 22) documented in < 2,100 m and
veys off the island of Hawai‘i from 2002 through within 35 km of shore that match the resident
2010 (see Baird et al., 2008, 2009a for methods). social network, and the lack of such matches for
Sighting water depths ranged from 360 to 3,903 m the five groups documented in deeper water or
(mean = 1,438 m, SD = 911 m), while distance farther from shore, suggests that individuals docu-
from shore ranged from 2.1 to 48.9 km (mean = mented in very deep water or very far offshore are
11.3 km, SD = 11.9 km). Identification photos more likely to be from an open-ocean population.
were available from 27 of the 29 encounters. Locations from HIMd153 were received over
From these there were 92 identifications of 52 a 40-d span. After filtering, there were 109 loca-
distinctive individuals, 19 of which were seen on tions on 37 different days. The distribution of
more than one occasion. Of these 27 encounters, location classes (LC, an indicator of the loca-
individuals from 21 of these link by association tion accuracy and number of messages received
in a single social network (not shown), including by the satellite during the overpass) was similar
the previously satellite tagged individuals studied (LC3 – 2.75%; LC2 – 9.17%; LC1 – 22.02%;
by Schorr et al. (2009). Some of these individu- LC0 – 44.04%; LCA – 11.01%; LCB – 10.09%;
als have been resighted in the area over periods of LCZ – 0.92%) to Schorr et al. (2009). The inter-
up to 17 y (McSweeney et al., 2007), suggesting val between consecutive locations ranged from
they are long-term residents and strongly associ- 0.38 to 36.43 h (median = 6.55 h). Over the 40 d,
ated with the island. All 21 of these encounters HIMd153 moved a cumulative minimum distance
that were linked by association were in depths of of 1,801 km and traveled 1,008 km from the site
< 2,100 m and within 32 km of shore. of tagging (Figures 1 & 2). While covering similar
On 29 April 2009, a group of three Blainville’s or greater cumulative distances, satellite-tagged
beaked whales was encountered in 3,812 m water individuals from the island-associated population
depth 32.3 km from shore, off the southwestern (Schorr et al., 2009) remained relatively close to
5 08 Baird et al.
Figure 1. Map showing movements of HIMd153 over the 40 d of signals from the tag
1200(cid:1)
m) HIMd153(cid:1)
n (k 1000(cid:1) HIMd148(cid:1)
o
ocati 800(cid:1) HIMd025(cid:1)
g l
n
ggi 600(cid:1)
a
m t
e fro 400(cid:1)
c
n
sta 200(cid:1)
Di
0(cid:1)
0(cid:1) 5(cid:1) 10(cid:1) 15(cid:1) 20(cid:1) 25(cid:1) 30(cid:1) 35(cid:1) 40(cid:1)
Days since tagging(cid:1)
Figure 2. Distance from tagging location over time for HIMd153 and the two individuals from the island-associated
population (HIMd148 and HIMd025) that had the greatest average distance from tagging locations (see Schorr et al., 2009)
the sites of tagging (Figure 2). The horizontal rate 2 wks were associated with the northern edges of
of movement calculated using all pairs of consecu- two cyclonic eddies, possibly moving with the
tive locations obtained from 4 to 24 h apart ranged currents, although movements in the latter half
from 0.17 to 8.51 km h-1 (median = 1.575 km h-1); of the track were not associated with any strong
however, there was a significant negative relation- oceanographic features visible in AVISO SSH and
ship between the rate of movement and the time current data (Figure 3).
since tagging (regression, r2 = 0.118, p = 0.005). HIMd153 utilized depths ranging from 3,150
During the first 20 d, while the whale generally to 4,946 m (median depth = 4,702 m), on aver-
travelled away from the island, the median hori- age using water four times deeper than individuals
zontal rate of movement was 2.41 km h-1; while from the island resident population (Schorr et al.,
during the last 20 d, when the whale used a broad 2009). After the 4th d post-tagging, there were
area located 900 to 1,000 km from the tagging loca- no depths associated with satellite-derived loca-
tion, it was 0.99 km h-1. By comparison, the grand tions shallower than 3,500 m. The distance from
mean of the median rates of horizontal movement the closest point of land in the main Hawaiian
from the six groups of Blainville’s beaked whales Islands ranged from 17.6 to 573.0 km (median
previously satellite tagged was 1.16 km h-1 (Schorr = 282.6 km). When the tag stopped transmitting,
et al., 2009). Many of the locations during the first HIMd153 was still inside the U.S. EEZ surrounding
Beaked Whale Open -Ocean Movements 509
the Hawaiian Islands, but only 60.9 km from the and reactions of beaked whales to naval sonar
EEZ boundary (Figure 1). exercises. Individuals of several species of beaked
Based on the depth and distance that HIMd153 whales, including Blainville’s beaked whales,
was encountered from shore and the lack of any have died in association with mid-frequency
link by association to the island-resident social active sonar use (Balcomb & Claridge, 2001;
network, we believe this individual was not part Jepson et al., 2003; Fernandez et al., 2005). Such
of the island-associated population of Blainville’s mortalities are thought to occur due to changes in
beaked whales, but, rather, from an open-ocean diving behavior leading to decompression sick-
population. The spatial use patterns and depths ness (Jepson et al., 2003; Fernandez et al., 2005;
used by this individual differed dramatically from Cox et al., 2006; Hooker et al., 2009). The history
previous Blainville’s beaked whales tagged in of prior exposure of individuals may be important
Hawai‘i, moving over 900 km from where it was in understanding their responses to mid-frequency
tagged in just 20 d and traveling over depths of up sonar since naïve individuals would potentially
to almost 5,000 m. Although the tagged whale did show strong behavioral responses, while those
not leave the EEZ in the 40 d we received loca- exposed to mid-frequency sonar on a regular basis
tions from the tag, the broad ranging movements may habituate to some degree (Falcone et al.,
and proximity to the EEZ boundary suggest that 2009). Movement patterns of HIMd153 suggest
Blainville’s beaked whales in offshore waters sur- that individuals from an open-ocean population
rounding the Hawaiian Islands are likely part of a are much less likely to be regularly exposed to
larger oceanic population that uses both U.S. and mid-frequency sonar use from naval exercises that
international waters. Combined with the evidence typically occur in closer proximity to the islands
of an island-resident population (McSweeney (Anonymous, 2008). Since open-ocean animals
et al., 2007; Schorr et al., 2009), it appears that, may be naïve to sonar exposure, their reactions
like many other species of odontocetes in Hawaiian and potential impacts may differ from those that
waters (Chivers et al., 2007, 2010; Baird et al., have been exposed on multiple occasions through-
2008, 2009a; Andrews et al., 2010; Aschettino out their lives.
et al., 2011), there is more than one population of
Blainville’s beaked whale in Hawaiian waters.
As well as their relevance for population struc-
ture, our results have implications for exposure
Figure 3. Track of the Blainville’s beaked whale tagged 29 April 2009 with sea surface height (SSH) (color) and surface cur-
rents (vectors); locations during periods when SSH and current data are available are indicated by symbols: circles represent
locations following intervals of > 4 h with shading indicating speed over the track from the previous location, and squares
represent locations < 4 h from the prior location with no speed indicated (see text). SSH and current data are shown (in panels
of varying widths depending on the distance moved, labeled in upper left of each panel) for the weeks of (a) 1 June 2009,
(b) 18 May 2009, (c) 11 May 2009, (d) 4 May 2009, and (e) 27 April 2009 (from left to right). The trackline for the week of
25 May 2009 is shown, but no locations are indicated.
5 10 Baird et al.
Acknowledgments patterns. Marine Mammal Science, 24, 591-612. http://
dx.doi.10.1111/j.1748-7692.2008.00200.x
This research was funded primarily by the Baird, R. W., McSweeney, D. J., Schorr, G. S., Mahaffy,
U.S. Navy (N45) via a contract from the Southwest S. D., Webster, D. L., Barlow, J., . . . Andrews, R. D.
Fisheries Science Center; we thank Jay Barlow for (2009b). Studies of beaked whales in Hawai‘i:
administering the contract funds. Improvements Population size, movements, trophic ecology, social
to the tagging methods were funded by Office organization and behaviour. European Cetacean Society,
of Naval Research Grant N000140811203. Special Publication 51, 23-25.
Additional funds for fieldwork were provided Balcomb, K. C., & Claridge, D. E. (2001). A mass strand-
by the Scripps Institution of Oceanography and ing of cetaceans caused by naval sonar in the Bahamas.
the Alaska SeaLife Center. We thank Phoebe Bahamas Journal of Science, 5, 1-12.
Woodworth from the Pacific Islands Fisheries Barlow, J. (2006). Cetacean abundance in Hawaiian waters
Science Center for producing Figure 3, Damon estimated from a summer/fall survey in 2002. Marine
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for GIS analyses, and two anonymous review- j.1748-7692.2006.00032.x
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under NMFS Scientific Research Permit No. 731- M. M., Lowry, M. S., . . . Hill, M. C. (2011). U.S. Pacific
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