SPLASH: Structure of Populations, Levels of Abundance, and Status of Humpbacks Proposal

Splash Structure Populations Levels Abundance and Status Humpback Whales North Pacific >> SPLASH: Structure of Populations, Levels of Abundance, and Status of Humpbacks Proposal


North Pacific humpback whale populations were thought to have been reduced from about 15,000 prior to commercial exploitation to just over 1,000 after whaling (Rice 1978, Gambel 1976, Johnson and Wolman 1984) and remain listed as endangered today. Data from photo-identification and genetics studies have provided some information on North Pacific stock structure, verifying a high degree of site fidelity to feeding areas and some intermixing in the wintering areas. However, only limited data exist on the numbers, sizes, and potential boundaries of most feeding areas in the North Pacific (Calambokidis et al., 2001).

While estimates of abundance of North Pacific humpback whales were conducted in the 1990s (Calambokidis et al., 1997, 2001) its use today is limited by several factors: 1) these estimates are more than 10 years old; 2) they did not provide population trend information; 3) they had potential biases because sampling was not designed for abundance estimation, 4) most of the feeding areas in the North Pacific were not sampled, coverage of the Mexico wintering areas was limited and Central America was not covered at all, 5) genetic data to examine population structure were not part of the study, and 6) no assessment of health effects or incidence of human impacts were conducted as part of the study.

A number of potential threats to humpback whales remain in the North Pacific. Climate change and global warming may be having an effect. Long-term declines in plankton have been documented off California from the 1970s to the mid-1990s (Roemmich and McGowan 1995) and this appears to have caused dramatic declines in some krill-feeding marine seabirds off California (Veit et al. 1997). Incidental fishing entanglement remains a major concern since humpback whales in many part of the North Pacific remain subject to such mortality and the level of incidental take in some areas has exceeded the allowed Potential Biological Removals (PBR) calculated by NMFS. Although increases in humpback whale abundance in the North Pacific have been documented in some areas there have also been some troubling indications: 1) populations off the U.S. West Coast which had been increase at 8-9%/year during the early and mid 1990s, declined sharply by about 30% sometime between 1998 and 1999 most likely as a result of El Nino conditions in late 1998 (Calambokidis et al. 2002), 2) abundances of humpback whales in the western North Pacific were estimated even in the most recent studies at surprisingly low levels (under 1,000)(Calambokidis et al. 1998).

Determination of the structure of humpback whale feeding areas and the abundance of animals in specific feeding and wintering areas is critical for management and for an assessment of how fisheries and other interactions affect this population. While humpback whales have been well studied in a few areas of the North Pacific, they have not been studied in many areas. While the existence of some discrete feeding areas have been identified (Baker et al., 1990, 1998; Calambokidis et al., 1996, 2001) the number and boundaries of other feeding areas in the North Pacific are unknown. Assessing impacts of incidental serious injury and mortality from commercial fisheries has not been possible due to the lack of information on the boundaries and abundance of animals in these feeding areas.


SPLASH proposes to conduct a dedicated sampling program and subsequent analysis of humpback whales in the entire North Pacific to address the following goals and objectives:

· Obtain a current estimate of overall abundance for the North Pacific including estimates for specific wintering and feeding areas and whether they are increasing or decreasing.

· Identify the population structure of humpback whales and how these influence genetic diversity and exchange.

· Determine key population parameters including reproductive and mortality rates as well as age/sex structure and pregnancy rates.

· Identify habitat and characterize use especially for areas used by humpback whales that have been well studied.

· Examine human impacts including the incidence of entanglement and ship strikes as well as obtain tissues for health assessment including toxicology.



Photographs of pigmentation patterns and scarring on the ventral surface of the flukes, together with serration patterns along the trailing edge (Figure 1), will be used to individually identify whales (Katona et al., 1979). To obtain photographs, whales will be followed in small or large survey vessels and photographed with 35-mm SLR or digital cameras equipped with telephoto lenses.

Biopsy Sampling

Skin and blubber tissue samples will be collected for genetic analysis and life history studies (e.g., pregnancy) using a small stainless steel biopsy dart fired from a crossbow or modified veterinary "capture" rifle (see summaries in Hoelzel 1991). Each dart is fitted with a flange or "stop" that regulates penetration of the bolt/dart and causes recoil after sampling. Flotation material secured to the shaft of the bolt/dart allows it to float on the surface and be retrieved after sampling. Crossbows, most commonly with a draw of 68 kg (150 lbs), and veterinary rifles using either compressed air or blank charges with adjustable pressure, have been successfully used to collect biopsy samples from thousands of humpback whales worldwide.

Sampling design

The SPLASH study is designed to provide broad geographic coverage of humpback whale summer and wintering areas in the North Pacific over multiple years. The proposed research program plans to collect data in the winter/breeding areas in three years and on the summer/feeding areas in two years (see Table 1). In all areas, effort will be allocated in a manner that is proportional to the density of animals.

Overall, the SPLASH study will provide a consistent sampling effort over a broad geographic area and across multiple years. This would be the first time that humpback whale photo-identification and biopsy sampling was done as part of an overall structure and study design throughout the North Pacific. All previous analyses have been done using retrospective analysis of existing data collected by many different research groups, often for different uses and purposes.

An overall target would be a CV on the overall estimate of 15%, and an initial target of 10% animals photo-identified in each region in each sampling period. Some areas, particularly those with fewer whales in them, may need higher sampling rates to achieve similar numbers of matches between years. These sampling rates are similar to what was achieved during the YONAH project, which achieved a CV of 0.13-0.15 for photograph-based estimates of abundance (Smith et al., 1999).

Biopsy samples will be the fundamental source of data for investigating population structure. They also can be used for mark-recapture abundance estimation. For investigating population structure, having representative samples from broad areas is the goal. Without knowing population structure in advance, it is difficult to specify required sample sizes. However, similar genetic studies during the YONAH project provide some guidance for SPLASH target sample size. The initial target is 500 total samples from all winter/breeding areas and 1000 total samples from all summer/feeding areas.

Study areas

Humpback whales in the North Pacific utilize a broad range of diverse habitats. Feeding areas range from California in the eastern North Pacific north into the Gulf of Alaska and Bering Sea and then south to Hokkaido in the western North Pacific. Breeding areas are also widely distributed and include Central America (Steiger et al., 1991), three areas of Mexico (Urban and Aquayo, 1987), the Hawaiian Islands, and several areas in the western North Pacific including the Ogasawara Islands, Ryukyu Islands (Darling and Mori, 1993), and the Philippines (Acebes, 2001; Yamaguchi et al., 2002). Humpback whales in different regions have been studied to varying degrees. Their accessibility also varies widely and requires varied sampling strategies depending on region. Here we review, by region, some of the background information and proposed sampling strategies for the SPLASH study (also see Table 2).



Humpback whales in this region primarily use waters on the continental shelf and near the shelf break within 50 nm of the coast. Existing sampling primarily from dedicated small boat survey effort, have been effective in obtaining identifications of 200-300 individuals from different locations. Continuation of this sampling is anticipated and should be more than adequate for meeting the goals of SPLASH.

British Columbia

Humpback whales can be found in many near shore areas of British Columbia, including both exposed coastal waters and protected inshore inlets and straits. A representative sampling of humpback whales in British Columbia could be obtained primarily from small (<10 m) vessels operating from coastal bases. Additional samples in remote or offshore locations (e.g. northwestern Vancouver Island, west coast Queen Charlotte Islands) would require a larger support vessel, from which a smaller vessel would be deployed to collect data. Survey effort needed is estimated to be 40 days of small vessel work, and 14 days of surveys based on a medium or large size vessel. Fisheries and Oceans Canada has supported recent humpback studies in British Columbia as part of its new Species-at-Risk mandate, and it is anticipated that this funding source will be available to help undertake the SPLASH surveys.

Southeastern Alaska/Eastern Gulf of Alaska

Southeastern Alaska extends from Dixon Entrance to Yakutat Bay. Since 1979, a few areas have been well studied in the northern part of southeastern Alaska; these include Glacier Bay, Frederick Sound and Sitka Sound. Sampling would consist of small boat surveys and 3 cruises of 10-14 days using a 40' to 60' vessel used as a living platform with skiff launch capability.

Western Gulf of Alaska

Humpbacks occur throughout the central and western Gulf of Alaska (GOA) from Prince William Sound (PWS) to Unimak Pass. Seasonal concentrations are found in coastal waters of PWS, Barren Islands, Kodiak Archipelago, Shumagin Islands and south of the Alaska Peninsula. Large numbers of humpbacks have also been reported in waters over the continental shelf, extending up to100 nm offshore in the western GOA. Complete sampling of western GOA humpbacks would require coverage of several near shore areas of concentration as well as humpbacks dispersed more broadly across shelf waters. Shore-based researchers using small vessels (80 days) and medium-sized vessels (14 days) would be used to sample GOA Near shore Waters. GOA Offshore Waters survey coverage would be complemented by large vessel survey of shelf waters greater than 20 nm offshore. Humpbacks are dispersed throughout offshore GOA waters with large concentrations found between Seward and southern Kodiak waters. It is anticipated that 75 sea days would be required to survey waters from Prince William Sound to Unimak Pass from 10-100 nm offshore.

Aleutian Islands

Near shore waters of the Aleutian Islands will be surveyed by large ship in a manner similar to that recently employed by National Marine Fisheries Service (NMFS) researchers (Wade, pers. comm.) and will cover the areas around Dutch Harbor, Unalaska and Unimak Pass. Offshore waters of the Aleutian Islands will also follow a similar survey approach and will cover the offshore areas from Unimak Pass to Russian territorial waters.

Bering Sea

Humpback whales have been observed throughout much of the shelf waters of the Bering Sea. The goal of SPLASH in this area would be to systematically cover the entire Bering Sea south of approximately St. Lawrence Island. As in the Gulf of Alaska, a relatively large ship would be required as a platform to survey these extensive offshore waters. Given past experience on the Miller Freeman surveys, it is anticipated that at least 45 days would be required to survey this region. Having representative samples from this entire region for the first time would represent a substantial new contribution to knowledge of humpback whales in the North Pacific.


Although little is known regarding the distribution and numbers of humpback whales summering off the coast of Far East Russia, past whaling records and recent field observations suggest that this region serves as one of the migratory destination for some portion of the North Pacific population (Doroshenko, 2000; Melnikov, 2000). In general, humpback whales are thought to occur in relatively coastal waters between the northern Chukotka Peninsula and the southern Kamchatka Peninsula. Recent records have noted small numbers of whales (< 30) off Chukotka, Olutorsky Cape, Karaginskiy Island and the Commander Islands. Since the distribution of humpbacks in this entire region is poorly understood, broad geographic survey coverage of the area by large vessel equipped with small inflatable over a 40-day period is suggested. This effort is considered sufficient to meet SPLASH objectives. Shore-based small boat operations, in combination with continued large vessel survey effort, is also possible in some regions during year two, if results from year one indicate areas of high whale numbers that correspond with regions of sufficient coastal access and logistical support. This work would be coordinated and primarily conducted by the Center for Endangered Large Whales at the Kamchatka Institute of Ecology and Nature Management, Russia.


Western North Pacific

The winter distribution of humpback whales in the western North Pacific is centered off the Ogasawara Islands, Ryukyu (Okinawa) Islands, Taiwan, the Philippines, and the Mariana Islands. Currently, the number of individually identified whales in this entire area is estimated to be 1,500 with 1,100 identified off Ogasawara, 350 off Okinawa, 40 off the Philippines, 2 off Taiwan and a few reported sightings the Mariana Islands. In addition to the continuation of the studies off Ogasawara and Okinawa, surveys in other surrounding regions, including waters of multiple countries, are required to understand the structure of the whole western North Pacific population. Humpback whales in this geographic region are distributed over a large area along the chain of islands and some areas will need to be surveyed by large vessel.


Approximately half of the humpback whales in the North Pacific use the waters surrounding the Hawaiian Islands each winter (5,000 in 1993, Calambokidis et al., 1997). In order to minimize the impact of these potential sources of bias, sampling in the Hawaiian wintering grounds will span both the geography and timing of the whales' occurrence, with sampling effort dependant upon whale density. A lower level of effort will occur at the beginning (December, January) and end (April, May) of the winter season, with increased effort in the middle of the season (February, March). Given the coastal nature of most whale habitat in this region, the bulk of the sampling will occur from smaller land-based vessels. In order to reach SPLASH objectives, a combination of contracted Hawaiian researchers and Sanctuary resources will conduct approximately 230 survey days (December through May), throughout the Islands, each winter for three years, beginning in the winter of 2004. Selection and sampling of individual whales encountered will follow standardized sampling methodologies, developed for winter habitats, based on updated YONAH sampling protocols.


There are three main winter aggregations in the Mexican Pacific: the southern end of Baja California Peninsula (Baja); Bahia Banderas area including the Islas Tres Marias and Isla Isabel (Mainland); and the Revillagigedo Archipelago (Urban and Aguayo, 1987). Field effort to achieve SPLASH objectives would be conducted between January and April. To obtain whale identifications and genetic samples off the Mainland region, 45 days of small boat survey effort and 7 days of intermediate-size boat survey effort would be needed off both the Baja California Peninsula and Bahia de Banderas areas. To obtain similar data in the Revillagigedo Archipelago region, 45 days of small boat survey effort are needed off Isla Socorro and 15 days of small boat surveys off Isla Clarion.

Central America

The waters from southern Mexico south along the Central America coast are used as a wintering area for humpback whales coming almost exclusively from feeding areas off California (Steiger et al. 1991; Calambokidis et al., 2000; Rasmussen et al., 2001). Shore-based small boat surveys have been conducted for short periods annually off Costa Rica and more recently Panama and typically obtain a few dozen identifications over several weeks effort. Other portions of coastal Central America waters have only been identified from a single 2-week survey conducted from southern Mexico to northern Costa Rica that obtained about 20 identifications. Coverage of some areas is possible from shore-based small boats but more complete coverage of this region would require use of an intermediate-size boat in some areas or low-cost intermediate boat to annually survey the entire region from southern Mexico to Panama and obtain more identifications and biopsy samples.


Total abundance in the North Pacific

Photographic and genetic mark-recapture data generated by SPLASH would be subjected to a variety of capture-recapture methods ranging from the simpler models (Peterson and Jolly-Seber estimators) to the more complex multi-strata models to estimate the abundance of humpback whales in feeding areas, wintering areas and the North Pacific population as a whole. A geographically stratified mark-recapture model similar to that used in the past analyses of the 1990-93 data (Calambokidis et al., 1997) is considered the most promising for the proposed study (Darroch, 1961; Hilborn, 1990).

Population structure in the North Pacific

Population structure will be examined through both the movement patterns of photographically identified whales and genetic markers. Genetic markers may include, but will not be limited to, mitochondrial control region sequences, microsatellite loci, and sex identification. Photographic identifications will also be used to examine several aspects of population structure. Based on interchange within and between seasons on the feeding grounds we will identify potential boundaries and interchange between feeding aggregations. Interchange rates between feeding and wintering areas will help identify primary migratory destinations. The geographically stratified mark-recapture model will also provide estimates of migration rates between and among feeding and wintering areas.

Trends in abundance

Several past estimates of humpback whale abundance are available and could allow estimates of population trends. The primary past estimate of humpback whales for the entire North Pacific was for 1991 to 1993 (Calambokidis et al., 1997). While the proposed SPLASH study would involve some of the same approaches as used in this previous study, SPLASH will involve dramatically improved geographic sampling. To avoid bias in trying to estimate trends in abundance, we will estimate changes in abundance generated for both time periods using similar sets of samples (SPLASH constrained to match the same sampling locations and sizes as the 1991-93 study).

Data collection methods for other objectives

In addition to collecting photographic identifications and genetic samples to examine abundance and stock structure, the SPLASH project would include collection of other data that could be used to examine important questions related to humpback whale biology.

Population parameters

The data gathered under SPLASH will further the understanding of population parameters essential for assessing recovery of humpback whales in the North Pacific. These parameters include:

· Reproductive rates, from observations of females with calves, and mortality rates will help evaluate whether the population trend is increasing, decreasing or stable.

· Pregnancy rates obtained from tissue samples will produce a true pregnancy rate from the wintering areas, give insight into the success of annual reproduction, and determine if there is variation in pregnancy rates among feeding and possibly wintering areas.

· Age and sex structure, also obtained from tissue samples and behavioral data, will give insights into preferential habitat use and potential vulnerability of specific age classes to human interactions and predation.

· Changes in regional genetic diversity due to recent population interchange or expansion will be described by comparison of contemporary samples to samples collected in some regions more than 14 years ago (e.g., Baker et al. 1990).

Habitat use

SPLASH offers a unique opportunity to further our understanding of humpback distribution and habitat use in both feeding and breeding grounds in the North Pacific. Platforms obtaining photo-identification samples may, often with limited additional effort and expense, collect associated location and oceanographic data such as depth, sea surface temperature, and salinity. Systematically collected and integrated, such data will provide a valuable basin-wide characterization of seasonal humpback distribution, habitat, and use.

Human impacts

The SPLASH study will provide useful data to evaluate a number of human impacts (including entanglement and contaminants) in a more comprehensive manner than has been possible before. Entanglement in fishing gear is known to impede the recovery of some large whale populations. Robbins and Mattila (2001) were able to gain insight into the relationship between rates of entanglement and the age, sex and geographic distribution of humpback whales, which inhabit the Gulf of Maine. The entanglement rates of North Pacific humpback whales are unknown. The broad geographic scope and large sample sizes of photographs obtained during the SPLASH project will allow the first comparison of the impact of this human activity for an entire ocean basin. Blubber samples collected with biopsies will provide tissues available to test for concentrations of chlorinated hydrocarbons and other lipophilic contaminants. Tissues can also be used to test for biochemical markers of contaminant exposure.


In addition to serving to meet the primary objectives of the study, the SPLASH photographic catalog and tissue archive will be preserved as a legacy for use in future research and conservation. Also, SPLASH data will continue to add to the photographic archive at NMML, which began in 1986, and to long term sighting records for individual humpback whales maintained by researchers, with some records dating as far back as 1968. Tissue collected for genetic and other analyses will add to archived samples collected initially with stranded animals and, since 1985, supplemented with tissue from biopsied animals. SPLASH will provide a large and comprehensive collection of identifications and tissue samples collected under a standard protocol. These data, combined with the commitment to make this open and accessible to future researchers and managers, will be an important long-term contribution of this effort.


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Table 1. Proposed schedule for the SPLASH project.



Dec. 2003 - May 2004

1st winter area sampling

June 2004 - Nov. 2004

1st feeding area sampling

Dec. 2004 - May 2005

2nd winter area sampling

June 2005 - Nov. 2005

2nd feeding area sampling

Dec. 2005 - May 2006

3rd winter area sampling

June 2006 - Jan. 2007

Matching, genetic laboratory analyses

Jan. 2007 - July 2007

Analysis and synthesis,

Aug. 15 2007

Final reports

Table 2. Summary of regions, proposed coordinators and notes on sampling


Regional coordinators

Comments about sampling

Western North Pacific wintering areas

Manami Yamaguchi

Includes sampling of Ogasawara and Okinawa regions, sampling of Philippines desirable


David Mattila

Need to obtain samples from Big Island, 4-Island area, Penguin Bank, Kauai, and possibly other areas


Jorge Urban

Requires samples from mainland, Baja, and Revillagigedos

Central America

John Calambokidis

Large low density area that may be used by larger than previously thought number of animals

California, Oregon, and Washington

John Calambokidis

Fairly representative sample already being obtained

British Columbia

John Ford

May represent two feeding areas with little interchange between north and south. May require combination of systematic surveys and shore-based small-boat surveys

SE Alaska including E Gulf of Alaska

Jan Straley

Requires more complete coverage of inside waters than present efforts as well as ship-based effort in offshore waters

Western Gulf of Alaska

Kate Wynne

A combination of shore-based effort around Kodiak, Shumigans, and other areas with large ship surveys in offshore areas by NMML/SWFSC

Aleutians and Bering Sea

Paul Wade/Jay Barlow/ Rick LeDuc

Large ship surveys by NMML/SWFSC, with some possible small/medium boat work in eastern Aleutians

Western North Pacific waters off Russia

David Weller/Alexander Burdin

We have little information on current humpback whale occurrence in this region. The initial effort would have to consist of ship surveys

Table 3. Agency representatives



Southwest Fisheries Science Center

Jay Barlow

National Marine Mammal Laboratory

Paul Wade

National Marine Sanctuary Program

David Mattila

National Park Service

Christine Gabriele

Canada Department of Fisheries and Oceans

John Ford

Instituto Nacional de Ecología

Lorenzo Rojas-Bracho