Spatial and Temporal Occurrence of Blue Whales off the U.S. West Coast, with Implications for Management

Mortality and injuries caused by ship strikes in U.S. waters are a cause of concern for the endangered population of blue whales (Balaenoptera musculus) occupying the eastern North Pacific. We sought to determine which areas along the U.S. West Coast are most important to blue whales and whether those areas change inter-annually. Argos-monitored satellite tags were attached to 171 blue whales off California during summer/early fall from 1993 to 2008. We analyzed portions of the tracks that occurred within U.S. Exclusive Economic Zone waters and defined the ‘home range’ (HR) and ‘core areas’ (CAU) as the 90% and 50% fixed kernel density distributions, respectively, for each whale. We used the number of overlapping individual HRs and CAUs to identify areas of highest use. Individual HR and CAU sizes varied dramatically, but without significant inter-annual variation despite covering years with El Niño and La Niña conditions. Observed within-year differences in HR size may represent different foraging strategies for individuals. The main areas of HR and CAU overlap among whales were near highly productive, strong upwelling centers that were crossed by commercial shipping lanes. Tagged whales generally departed U.S. Exclusive Economic Zone waters from mid-October to mid-November, with high variability among individuals. One 504-d track allowed HR and CAU comparisons for the same individual across two years, showing similar seasonal timing, and strong site fidelity. Our analysis showed how satellite-tagged blue whales seasonally used waters off the U.S. West Coast, including high-risk areas. We suggest possible modifications to existing shipping lanes to reduce the likelihood of collisions with vessels

Tracking North Pacific Humpback Whales To Unravel Their Basin-Wide Movements

In 2014, Oregon State University (OSU) initiated a multi-year project to study humpback whale (Megaptera novaeangliae) migrations in the North Pacific Ocean using satellite tracking technology in combination with genetic and photo-identification (photo-ID) analyses. The study is highly relevant to management, given the need for new information arising from the recent separation of humpback whales into Distinct Population Segments (DPS) for listing under the US Endangered Species Act, including four DPSs in the North Pacific (“Western North Pacific”, “Hawaii”, “Mexico”, and “Central America”) with different conservation statuses. The project’s objective was to conduct a comprehensive characterization of humpback whale movements during breeding, migration, and feeding periods by tagging animals in both a feeding area (southeastern Alaska) and a breeding area (Hawaii). In order to obtain representative results, the sampling plan called for two field efforts at each site, with Pacific Life Foundation funding the southeastern Alaska portion of the project (2014 and 2015 seasons), and the Hawaii portion being cost-shared through a combination of sources including the Makana Aloha Foundation (2015 season) and the US Department of the Navy (2018 season). This final report provides the combined results and accomplishments from these efforts. Argos-based, fully implantable tags were deployed on 37 humpback whales in Seymour Canal and Frederick Sound, southeastern Alaska, in 2014 and 2015. Tracking periods ranged from 3.3 to 78.3 d (mean = 28.2 d, sd = 16.2 d), with distances traveled ranging from 73 to 6,503 km (mean = 2,010 km, sd = 1,649 km). The tracked locations for these animals ranged over 40 degrees of latitude, from Lynn Canal and Icy Strait (59°N) in southeastern Alaska to the southern tip of Hawaii Island (19°N) in the Hawaiian Archipelago. Genetic and photo-ID analyses revealed that two of the whales tagged in 2014 were re-tagged in 2015, providing a unique opportunity to compare movements between years for the same individuals. For one of these animals the movements and their timing were similar between years, as it moved from Seymour Canal into Frederick Sound with a difference of 4 d between years. However, early failure of the tag in 2014 (after 6.2 d) prevented a longer comparison. In contrast, the movements of the second animal within southeastern Alaska were similar but the timing was very different between the two years, despite a similar tracking period (21.9 d in 2014 versus 19.1 d in 2015). In 2014 this animal spent a substantial amount of time in Seymour Canal (17 d) before moving into Stephens Passage for the remainder of its tracking period, while in 2015 the animal moved into Stephens Passage soon after tagging and only for a brief period before it moved into Frederick Sound, from where it initiated the migration toward Hawaii. Differences in timing notwithstanding, the similarities in the tracks between years for both animals provided some evidence of route fidelity, as has been recently shown for several species of migratory marine animals. Twenty of the whales tagged in southeastern Alaska began their winter migration to a low-latitude breeding area, with start dates ranging from 19 November to 6 January. Three of these whales were tracked to breeding areas, two to Hawaii and one to the Mexican mainland. Another 16 whales were headed in the direction of Hawaii and one in the direction of Mexico when their tags quit. The duration and distance spent on migration for the three animals that reached a breeding area ranged from 29 to 46 d and from 4,200 to 4,700 km, respectively. The two animals that arrived in Hawaii entered the archipelago at Hawaii Island. Forty-five tags were deployed on humpback whales off Maui, Hawaii, in 2015 and 2018. Two of these tags provided no locations. Tracking periods for the remaining 43 whales ranged from 0.1 to 147.2 d (mean = 20.8 d, sd = 29.0 d), with distances ranging from 13 to 11,302 km (mean = 1,217 km, sd = 2,348 km). The tracked locations for these animals ranged over 43 degrees of latitude, from the south coast of Maui (21°N) to the Bering Sea (64°N). While in Hawaiian waters, the majority of locations were in the Maui Nui region (the waters between the islands of Maui, Lanai, Molokai and Kahoolawe), during both in 2015 and 2018. Penguin Bank was another area heavily frequented by the tagged whales. Most tagged whales moved in a predominant northwesterly direction after tagging, with animals leaving Maui headed for Lanai, Molokai, and/or Penguin Bank. Several whales were also tracked to Oahu, and one whale was further tracked to both Kauai and Niihau. Only one whale was tracked southeast to Hawaii Island in 2015, but other tagging studies have documented eastward movements to Oahu, Penguin Bank, and Maui Nui, so it is apparent that whales may move extensively between islands, both in westerly and easterly directions. Nine of the whales tagged in Hawaii began their migration to a high-latitude feeding area, with departure dates ranging from 29 January to 11 April. Four of these whales were tracked to feeding areas, three to northern British Columbia and one to the eastern Aleutian Islands. Another four whales were headed on a northeasterly trajectory toward northern British Columbia and three more on a northerly or northwesterly trajectory toward destinations in the Aleutian Island chain when their tags quit. The three whales that were tracked to northern British Columbia arrived in the Haida Gwaii Archipelago after having spent 30-44 d and 4,300-5,000 km on migration. The animal that migrated north to the eastern Aleutians arrived at an area approximately 200 km south of Unimak Pass, 28 d and 3,775 km after departing Hawaii. These results, together with those obtained from animals tagged in southeastern Alaska that migrated to a breeding area (Hawaii or Mexico), provide evidence that the travel time and distance covered by humpback whales while on migration across the North Pacific Basin can vary widely, with overall ranges of 28-46 d and 3,775-5,000 km, respectively. A 50-km buffer zone around southeastern Alaska and Hawaii was used for purposes of characterizing whale movement speeds and residence times in the feeding and breeding areas (inside the buffer zones), as well as during migration (outside the buffer zones). Residence time was computed as the time period from tag deployment to when a whale crossed the buffer zone boundary as it departed on migration. Residence time in southeastern Alaska in late fall was estimated for 20 whales, ranging from 4.4 to 49.1 d (mean = 17.3 d), although additional information from earlier tagging studies indicated that individual humpback whales may use this feeding area for periods of up to four to five months. In contrast, residence time in Hawaii was estimated for nine whales, ranging from 3.3 to 23.2 d (mean = 14.8 d), consistent with earlier photo-ID and telemetry studies and lending support to the notion that that there is a rapid turnover of individuals in this breeding area during the winter season. In any case, overall true residence time in these areas is likely longer than the minimum values we report based on satellite telemetry, as we cannot know the time a whale had spent in an area prior to tagging. Movement speeds during the different phases of the migration (feeding, breeding, migrating) were calculated based on the portions of the tracks that occurred inside or outside the 50-km buffer zones. Whales tagged in southeastern Alaska moved at a mean speed of 1.01 km/h (median = 0.47 km/h, sd = 1.28 km/h) while in the southeastern Alaska feeding area; 5.51 km/h (median = 5.63 km/h, sd = 1.98 km/h) while migrating; and 1.49 km/h (median = 1.01 km/h, sd = 1.36 km/h) once they arrived in the Hawaii breeding area. Whales tagged in Hawaii moved at a mean speed of 1.36 km/h (median = 1.00 km/h, sd = 1.21 km/h) while in the Hawaii breeding area; 4.44 km/h (median = 4.32 km/h, sd = 2.18 km/h) while migrating; and 2.00 km/h (median = 1.53 km/h, sd = 1.53 km/h) once they arrived in the southeastern Alaska feeding area. These results showed that whales moved much slower while in the feeding and breeding areas than while migrating, and that travel speed from the feeding to the breeding areas was somewhat faster than from the breeding to the feeding areas. Biopsy samples were collected from 27 of the whales tagged in southeastern Alaska in 2014 and 2015, and from 39 of the whales tagged in Hawaii in 2015 and 2018. These 66 samples were identified by a unique multi-locus genotype of at least 14 microsatellite loci, which indicated they represented 64 unique individuals (after accounting for the two animals that were re-tagged). The 25 individuals tagged in southeastern Alaska represented 14 females and 11 males. The 39 individuals tagged in Hawaii represented four females and 35 males. The DNA profiles of the 64 individuals were compared to a reference database of 1,805 individuals sampled from 2004 to 2006 in the North Pacific by the program SPLASH, which revealed nine matches (i.e., genotype recaptures). Of these, six matches were recaptures within an area (four within southeastern Alaska and two within Hawaii) and three were recaptures between whales tagged in Hawaii and sampled previously on feeding areas in either northern British Columbia (n = 2) or southeastern Alaska (n = 1). Mitochondrial deoxyribonucleic acid (mtDNA) sequences of the 64 individuals resolved seven haplotypes for the consensus region of 500 base-pairs. All seven haplotypes had been previously described for North Pacific humpback whales by SPLASH, but only two occurred in the southeastern Alaska samples while all seven occurred in the Hawaii samples, supporting earlier results indicating a greater haplotypic diversity in the Hawaii breeding area than in the southeastern Alaska feeding area. Further, pairwise tests of differentiation between the tagging areas and the 18 SPLASH regional strata were consistent with those reported in that study, supporting our current understanding of humpback whale population structure, migratory destinations, and site fidelity in the North Pacific. Photo-IDs (fluke photographs) were obtained from 30 whales tagged in southeastern Alaska and from 24 whales tagged in Hawaii. Comparisons with the online Happywhale photo-ID database as well as with OSU’s own ID catalog revealed matches for 25 of the tagged whales (18 from southeastern Alaska and seven from Hawaii). Thirty-five percent of the tagged whales with an ID were found in Happywhale and 13 percent in OSU’s catalog. Most matches (19 of 25) were made within the same area in which the whale was tagged, with time spans between sightings of up to 14 years. Two whales tagged in southeastern Alaska in 2014 each had only one photo-ID match in a different area than the one in which they were tagged. Both had been previously photographed in Hawaii, one in 1997 (17 years apart) and in 2004 (10 years apart). The remaining four resighted tagged whales had both within- and between-area matches. Three of these latter whales were tagged in southeastern Alaska, with two of them matching sightings in Hawaii (1987 and 2019, respectively), and the third one being resighted in central California on two consecutive years (2017 and 2018). The fourth whale was tagged in Hawaii and matched sightings over six consecutive years (2013-2018) in southern British Columbia/northern Washington. An additional 26 matches were found in Happywhale from among 149 fluke photographs of untagged whales collected by OSU in Hawaii. Of these, 13 matches were made within Hawaii (with a maximum time span between sightings of 21 years); nine matches were made between Hawaii and different parts of Alaska, including southeastern Alaska, Kodiak Island, Cook Inlet, and the Shumagin Islands; four matches were made between Hawaii and Washington State and Vancouver Island, British Columbia; and one match was made between Hawaii and the Chukchi Sea, near Kolyuchin Island, northeastern Russia. Through the combined use of satellite tagging, genetics, and photo-ID, we characterized the patterns of humpback whale occupation in both a breeding and a feeding area in the North Pacific Ocean, as well as the long-distance migratory movements that these animals undertake seasonally between these areas. The results of this study revealed the complex migratory linkages between Hawaii and the high-latitude feeding areas with unprecedented detail. Genotype and photo-ID recaptures of multiple individuals between migratory destinations supported previously known strong connections between breeding and feeding areas (e.g., Hawaii and southeastern Alaska/northern British Columbia, and Hawaii and Washington/southern British Columbia). Satellite tracking also revealed the movements and migratory connections between Hawaii and feeding areas in the Aleutian Islands and the Bering Sea, while photo-ID recaptures demonstrated additional connections between Hawaii and feeding areas in the northern Gulf of Alaska (Shumagin Islands, Kodiak Island, Cook Inlet) and the Chukchi Sea. Additional years of sampling during different parts of the reproductive season and in other parts of the main Hawaiian islands (e.g., Kauai and Hawaii), as well as in the northwestern Hawaiian Islands, would provide valuable information to address outstanding questions about the humpback whale DPS using this extensive breeding area, as well as its broader connections to remote feeding areas throughout the North Pacific Basin, most of which are poorly known. Also, while the majority of whales tracked from southeastern Alaska showed a strong connection to the Hawaii breeding area, a small proportion of these animals demonstrated a connection to the Mexican mainland breeding area, indicating some mixing of the Hawaii and Mexico DPSs in the southeastern Alaska feeding area. These animals are of particular interest, as in their transit along the western coast of North America they overlap with animals from the Central America DPS, which forages off California and Oregon. Further tagging work to better understand the patterns of habitat use and the extent of the overlap between the Mexico and Central America DPSs in this region would greatly help current needs to improve how animals are assigned to DPS for management purposes in the context of relative exposure to anthropogenic activities, given their different conservation statuses

Spatial and Temporal Occurrence of Blue Whales off the U.S. West Coast, with Implications for Management

Mortality and injuries caused by ship strikes in U.S. waters are a cause of concern for the endangered population of blue whales (Balaenoptera musculus) occupying the eastern North Pacific. We sought to determine which areas along the U.S. West Coast are most important to blue whales and whether those areas change inter-annually. Argos-monitored satellite tags were attached to 171 blue whales off California during summer/early fall from 1993 to 2008. We analyzed portions of the tracks that occurred within U.S. Exclusive Economic Zone waters and defined the ‘home range’ (HR) and ‘core areas’ (CAU) as the 90% and 50% fixed kernel density distributions, respectively, for each whale. We used the number of overlapping individual HRs and CAUs to identify areas of highest use. Individual HR and CAU sizes varied dramatically, but without significant inter-annual variation despite covering years with El Niño and La Niña conditions. Observed within-year differences in HR size may represent different foraging strategies for individuals. The main areas of HR and CAU overlap among whales were near highly productive, strong upwelling centers that were crossed by commercial shipping lanes. Tagged whales generally departed U.S. Exclusive Economic Zone waters from mid-October to mid-November, with high variability among individuals. One 504-d track allowed HR and CAU comparisons for the same individual across two years, showing similar seasonal timing, and strong site fidelity. Our analysis showed how satellite-tagged blue whales seasonally used waters off the U.S. West Coast, including high-risk areas. We suggest possible modifications to existing shipping lanes to reduce the likelihood of collisions with vess

Blue whale 90% Home Range area (A) and 50% Core Area of Use (B).

<p>Kernel derived Home Ranges and Core Areas of Use were created from blue whale satellite tracks with > = 30 daily locations inside the U.S. Exclusive Economic Zone. Tags were deployed off California from 1998–2008. Data are presented by year on a log scale and the circles inside the boxes are median values.</p

Julian day of U.S. Exclusive Economic Zone departure by satellite tagged blue whales.

<p>Circles in the boxes are median values.</p

Number of overlapping blue whale Core Areas of Use near commercial shipping lanes.

<p>The Core Areas of Use were created from blue whale satellite tracks with > = 30 daily locations inside the U.S. Exclusive Economic Zone. The regions shown are the Channel Islands (A) and the Gulf of the Farallones (B). Tags were deployed off California from 1998–2008. Hashed polygons represent the commercial shipping lanes transiting the area. Inset histograms show the overall number of blue whale locations recorded in the U.S. Exclusive Economic Zone (gray), and the number of locations recorded in the area shown (black).</p

Summary of satellite tagged blue whale tracks.

<p>Number of tracks with > = 30 locations in the U.S. Exclusive Economic Zone waters and the number of tracks that departed U.S. Exclusive Economic Zone waters listed by year. Deployment method and duration summary for all tags deployed is listed to the right.</p

Spatial and Temporal Occurrence of Blue Whales off the U.S. West Coast, with Implications for Management

<div><p>Mortality and injuries caused by ship strikes in U.S. waters are a cause of concern for the endangered population of blue whales (<i>Balaenoptera musculus</i>) occupying the eastern North Pacific. We sought to determine which areas along the U.S. West Coast are most important to blue whales and whether those areas change inter-annually. Argos-monitored satellite tags were attached to 171 blue whales off California during summer/early fall from 1993 to 2008. We analyzed portions of the tracks that occurred within U.S. Exclusive Economic Zone waters and defined the ‘home range’ (HR) and ‘core areas’ (CAU) as the 90% and 50% fixed kernel density distributions, respectively, for each whale. We used the number of overlapping individual HRs and CAUs to identify areas of highest use. Individual HR and CAU sizes varied dramatically, but without significant inter-annual variation despite covering years with El Niño and La Niña conditions. Observed within-year differences in HR size may represent different foraging strategies for individuals. The main areas of HR and CAU overlap among whales were near highly productive, strong upwelling centers that were crossed by commercial shipping lanes. Tagged whales generally departed U.S. Exclusive Economic Zone waters from mid-October to mid-November, with high variability among individuals. One 504-d track allowed HR and CAU comparisons for the same individual across two years, showing similar seasonal timing, and strong site fidelity. Our analysis showed how satellite-tagged blue whales seasonally used waters off the U.S. West Coast, including high-risk areas. We suggest possible modifications to existing shipping lanes to reduce the likelihood of collisions with vessels.</p></div