A review of false killer whales in Hawaiian waters: 

biology, status, and risk factors 

Robin W. Baird 

Cascadia Research Collective 

218 1⁄2 West Fourth Avenue 

Olympia, WA 98501 

rwbaird@cascadiaresearch.org 

Report prepared for the U.S. Marine Mammal Commission 

under Order No. E40475499 

December 23, 2009
False killer whales in Hawai‘i 

1 

1. Executive Summary.................................................................................................................. 2 

2. Introduction............................................................................................................................... 3 

3. Biology of false killer whales.................................................................................................... 3 

4. False killer whales in Hawaiian waters................................................................................... 5 

4.A. Population structure ........................................................................................................... 7 

4.B. Population ranges, individual movements, and potential boundaries/overlap............... 10 

4.C. Estimates of abundance/population size .......................................................................... 12 

4.D. Population trends.............................................................................................................. 15 

4.E. Social organization and group structure ......................................................................... 17 

4.F. Diet and foraging ecology................................................................................................. 17 

5. Potential conservation threats ............................................................................................... 19 

5.A. Persistent organic pollutants............................................................................................ 20 

5.B. Changes in prey base ........................................................................................................ 20 

5.C. Ship strikes........................................................................................................................ 21 

5.D. Anthropogenic sounds...................................................................................................... 21 

5.E. Fishery interactions.......................................................................................................... 23 

6. Research Recommendations.................................................................................................. 33 

6.A. Analyses of existing data .................................................................................................. 34 

6.B. Analyses of existing data which would benefit from additional samples or data........... 34 

6.C. Analyses requiring additional field studies or data collection ........................................ 35 

7. Acknowledgments................................................................................................................... 36 

8. Literature Cited ...................................................................................................................... 36 

 

Cover photo: False killer whale in Hawai‘i. Photo © Deron Verbeck/iamaquatic.com 
False killer whales in Hawai‘i 

2

1. Executive Summary 

Recent management and conservation issues have arisen concerning false killer whales in 

Hawaiian waters. Two demographically isolated populations have been identified, a small 

(estimated 123 individuals) island-associated population around the main Hawaiian Islands 

(hereafter Hawai‘i insular stock) and a larger (estimated 484 individuals) offshore population 

(hereafter Hawai‘i pelagic stock). Individuals within the Hawai‘i insular stock regularly move 

among islands and have been documented at distances of 110 km offshore. Less is known of 

movements/range of individuals from the Hawai‘i pelagic stock; one group has been documented 

42 km offshore and individuals likely move beyond the Hawaiian Exclusive Economic Zone. No 

information is available to assess trends in the Hawai‘i pelagic stock. For the Hawai‘i insular 

stock, a significant decline in sighting rates from aerial surveys conducted between 1993 and 

2003 suggests a large decline in population size. Other available evidence also supports a decline 

in population size for the insular stock: a reduction in sighting rates from boat-based surveys 

since the mid-1980s, lower than expected survival based on photo-identification data, and much 

higher sighting rates and larger group sizes in a 1989 aerial survey compared to boat-based 

surveys since 2000. False killer whales in Hawai‘i feed primarily on large game fish that are also 

the target of commercial and recreational fisheries. A number of potential conservation threats 

have been identified. Individuals from the Hawai‘i insular stock have elevated levels of 

persistent organic pollutants. Three of nine individuals sampled had levels high enough to 

potentially influence health. Because of the overlap between false killer whale diet and 

commercially harvested fish, reduced prey size or abundance could influence false killer whale 

foraging success or nutritional levels. Significant declines in body size and/or catch per unit 

effort have been documented for several false killer whale prey species in Hawaiian waters. 

False killer whales have been documented taking fish off lines in both nearshore and offshore 

fisheries. Depredation of caught fish may lead to retaliatory shooting by fishermen although, 

given potential fines and penalties, such shooting is not likely to occur where it may be 

witnessed; thus there is no information available to assess the potential for this to influence 

population dynamics. With the overlap in diet with commercially and recreationally harvested 

fish, the potential for hook ingestion, either from depredation or from free-swimming hooked 

fish, is relatively high. Based on studies elsewhere, hook ingestion would have a high likelihood 

of leading to mortality. Bycatch may occur in nearshore kaka line or shortline fisheries that use 

similar, but shorter gear to offshore longline fisheries, but there is no observer coverage of 

nearshore fisheries. False killer whales are the most frequently recorded bycaught cetacean in the 

Hawai‘i-based offshore longline fishery. Rates of serious injury and mortality have exceeded the 

potential biological removal (PBR) levels since bycatch rates and population levels were first 

available in 2000. Bycatch rates are underestimated as they do not take into account individuals 

that are not positively classified as to species or individuals that may break free with gear 

attached before being documented by observers. A number of research recommendations are 

presented to help reduce uncertainty and to clarify factors that may be influencing the population 

trajectories of both the Hawai‘i insular and Hawai‘i pelagic stocks, as well as to provide 

information that could be used to reduce bycatch rates or otherwise mitigate anthropogenic 

impacts on these populations. 
False killer whales in Hawai‘i 

3

2. Introduction 

 Both residents and visitors to Hawai‘i have long been familiar with false killer whales 

(Pseudorca crassidens). The species was kept in captivity from the mid-1960s through the 1990s 

at Sea Life Park, one of Hawai‘i’s best known marine attractions, and a hybrid cross between a 

false killer whale and a common bottlenose dolphin (Tursiops truncatus) is still kept there today. 

In addition, because false killer whales are found near shore, often ride the bow of transiting 

vessels, and can be quite acrobatic (Figure 1), many frequent ocean users in Hawai‘i have had 

opportunities to see or interact with false killer whales. Despite such opportunities, false killer 

whales are far less common in Hawai‘i than humpback whales (Megaptera novaeangliae) and 

spinner dolphins (Stenella longirostris), which attract most of the attention of whale researchers 

and members of the marine mammal watching public. 

In recent years, however, a number of important management and conservation issues 

have arisen concerning false killer whales in Hawaiian waters. Bycatch in U.S. longline fisheries 

has exceeded the potential biological removal (PBR) level since population and bycatch 

estimates first became available in 2000 (Forney et al. 2000). Environmental organizations have 

filed lawsuits against the National Marine Fisheries Service (NMFS) over this issue, including a 

recent suit (Hui Mālama i Kohalā et al. v. National Marine Fisheries Service et al.1

) seeking the 

formation of a take reduction team (TRT) to reduce false killer whale bycatch. In addition, a 

petition was recently submitted to the NMFS seeking action to list the insular population of false 

killer whales as endangered under the Endangered Species Act (NRDC 2009). Response to these 

actions will require consideration of the best available information on the species’ population 

ecology in Hawai‘i and factors influencing the populations. To help meet this need, this 

document reviews available published and unpublished information on the status of false killer 

whales in Hawaiian waters and threats to their conservation, including fishery interactions, 

potential prey limitations, and persistent organic pollutants, among others. This report is not a 

comprehensive review of false killer whales worldwide. For general reviews of the biology of 

false killer whales, see Odell and McClune (1999), Stacey et al. (1994), and Stacey and Baird 

(1991). 

3. Biology of false killer whales 

 The false killer whale is the fourth-largest member of the family Delphinidae. The 

maximum recorded length is 5.06 m for females and 5.96 m for males. Individuals stop growing 

between 25 and 30 years of age, at which point the average body length (i.e., asymptotic length) 

of adult males is about 75–85 cm larger than adult females (Ferreira 2008). Despite sexual 

differences in length, distinguishing adult females from adult males is difficult in the field. The 

only other sexually dimorphic feature that has been described is the projection of the melon over 

the lower jaw, although this feature is not particularly useful in the field to distinguish sex. In 

adult males, the melon extends farther forward than in adult females. Males may have accessory 

mammary grooves, making it difficult to confirm sex of individuals by external appearance 

alone. Average body length varies among populations: the average asymptotic length of females 

 

1 Civ. No. 09-00113 DAE BMK (D. Haw filed Mar. 17, 2009)
False killer whales in Hawai‘i 

4

off Japan is 46 cm longer than those off South Africa; for males off Japan, the average 

asymptotic length is 58 cm longer than for males off South Africa (Ferreira 2008). 

Figure 1. A false killer whale leaping while chasing prey. Photo by R.W. Baird. 

 Although the false killer whale is generally characterized as a tropical and sub-tropical 

species, it is found primarily in the tropics; densities in sub-tropical waters are much lower. In 

the eastern North Pacific, density is high between the equator and approximately 15°N, and 

drops precipitously to the north of 15°N (Ferguson and Barlow 2003). Extralimital records of 

individuals have been reported from as far north as Alaska (Leatherwood et al. 1982) and British 

Columbia (Baird et al. 1989; Stacey and Baird 1991). In the 1950s and 1960s large groups were 

seen in southern California (Brown et al. 1966), but there currently are no recognized 

populations of this species north of Mexico. False killer whales are typically oceanic, coming 

closest to shore around oceanic islands. 

 False killer whales are relatively uncommon throughout their range. In surveys of 

cetaceans in the eastern tropical Pacific, they were the 11th most abundant delphinid of the 13 

species documented (Wade and Gerrodette 1993). Wade and Gerrodette (1993) estimated a mean 

group size of 11.4 whales (CV = 0.12) documented in ship-based surveys between 1986 and 

1990 in the eastern tropical Pacific. Leatherwood et al. (1982) note that they are highly social 

and sometimes occur in schools of more than 500 individuals. Reeves et al. (2002) note that they 

are typically observed in groups of 10 to 20 but that these groups “belong to larger schools 

consisting of hundreds of individuals.” Two schools estimated to number 300 individuals were 

documented in two different years off southern California (Brown et al. 1966). Six schools 
False killer whales in Hawai‘i 

5

observed from research cruises off Japan ranged in size from 2 to 200 individuals, with a mean 

size of 55 individuals (Kasuya 1971). Comparisons of group sizes among areas and using 

different survey techniques, however, are problematic for several reasons. A study comparing 

odontocete group size estimates by experienced observers to counts of the same groups using 

photographs obtained from a helicopter revealed that group size estimates are typically 

negatively biased by about 26 percent (Gerrodette et al. 2002). In the case of false killer whales, 

groups are often spread over very wide areas, which also negatively biases estimates of overall 

group size (Baird et al. 2008a, in press). In drive fisheries off Japan, groups ranged from 10 to 

201 individuals with a mean size of 99 individuals (Kasuya 1986). Ross (1984) reviewed group 

sizes from 14 mass strandings worldwide, which ranged from 50 to 835 animals (mean = 180 

individuals). The largest known mass stranding of the species was on 10 October 1946 when an 

estimated 835 false killer whales stranded near Mar del Plata, Argentina (Marelli 1953). An 

analysis comparing group sizes of stranded false killer whales with sightings data found that 

group sizes from strandings were significantly larger (Ferreira 2008). 

 Most of what is known about the life history of false killer whales comes from animals 

killed in a drive fishery in Japan (Kasuya 1986) and from stranded animals (e.g., Ferreira 2008). 

Although sample sizes are small, and life history traits vary among populations (Ferreira 2008), 

generally their life history is similar to that of killer whales (Orcinus orca); individuals mature 

slowly, reproduce infrequently, and are long-lived. Onset of sexual maturity for false killer 

whales (i.e., age of first ovulation) occurs between 8.25 and 10.5 years of age, and gestation is 

estimated to last between 15.1 and 15.7 months. Thus, age at first reproduction would range from 

9.5 to 11.75 years (Kasuya 1986, Ferreira 2008). The only reported birth interval, 6.9 years 

between calves, is from Japan (Kasuya 1986). Ovulation rates decrease with age, and females 

older than 44 years are thought to be post-reproductive (Kasuya 1986, Ferreira 2008). Maximum 

longevity is at least 57.5 years for males and 62.5 years for females (Kasuya 1986). 

 In captivity, false killer whales adapt more quickly to new circumstances and objects in 

their tanks than do most other species of delphinids, and they rapidly learn through observation 

(Brown et al. 1966). Prey-sharing in the wild has been observed frequently (Connor and Norris 

1982, Baird et al. 2008a) and false killer whales have even been observed passing caught fish to 

humans in boats or in the water. 

4. False killer whales in Hawaiian waters 

 Information on false killer whales in Hawai‘i comes from a variety of sources, including 

(1) large-vessel surveys by NMFS (HICEAS, PICEAS, MHICS), (2) small-vessel surveys, (3) 

aerial surveys,(4) the longline fishery observer program, (5) anecdotal reports and observations, 

(6) genetic analyses using remote biopsy samples, (7) photo-identification, (8) tagging studies 

using both satellite-linked and archival depth-of-dive tags, and (9) studies of persistent organic 

pollutants using biopsy samples. Although a number of recent publications and reports on false 

killer whales are available (e.g., Barlow and Rankin 2007, Chivers et al. 2007, Baird et al. 2008a, 

2008b), much information remains unpublished. For example, photo-identification data have 

increased substantially in the last two years but have not yet been fully analyzed (Figure 2). 

There is limited information available from stranded false killer whales in Hawai‘i as strandings 

are infrequent: Maldini et al. (2005) note only five single strandings in the period from 1937 to 

2002 (in 1974, 1980, 1986, 1990, and 1997), and no false killer whale strandings have been 
False killer whales in Hawai‘i 

6

recorded since (K. West, pers. comm.). Although much has been learned about population 

structure, movements, habitat use, social organization, and foraging behavior, significant gaps in 

knowledge on Hawaiian populations remain (e.g., life history parameters (e.g., age at first birth, 

calving intervals). Recommendations for research to address data gaps follow the review of 

biology and risk factors. 

Figure 2. Top. Number of identifications of distinctive and very distinctive false killer 

whales with good or excellent photo qualities (see Baird et al. 2008a) from Hawaiian waters by 

year, not including within-year re-sightings, but including photos from both insular and pelagic 

stocks. Identifications used in mark-recapture analyses for insular stock (Baird et al. 2005) 

identified with horizontal lines, identifications used in Baird et al. (2008a) analyses include those 

shown in solid gray and horizontal lines. Additional identifications available since Baird et al. 

(2008a) analyses shown in open box (through May 2009, not including photos obtained in 

October or December 2009). Bottom. Number of individuals from the insular stock identified by 

year, including only distinctive and very distinctive individuals with good or excellent quality 

photos. 

0

20

40

60

80

100

120

140

160

180

198619871988198919901991199219931994199519961997199819992000200120022003200420052006200720082009

Year

# identifications 

Additional since Baird et al. 2008

Baird et al. 2008

Baird et al. 2005

0

20

40

60

80

100

120

140

160

180

198619871988198919901991199219931994199519961997199819992000200120022003200420052006200720082009

Year

# identifications 
False killer whales in Hawai‘i 

7

4.A. Population structure 

 Prior to 2008, NMFS recognized a single Hawaiian stock of false killer whales for the 

purposes of estimating bycatch rates and PBR levels. In 2008, for the first time the NMFS stock 

assessment reports recognized two false killer whale stocks in Hawai‘i: an insular stock and a 

pelagic stock. A separate Palmyra Atoll stock was also recognized for the first time in 2008 

(Carretta et al. 2009a). 

 Two lines of evidence indicate that there are at least two stocks of false killer whales in 

the Hawaiian Exclusive Economic Zone (EEZ): genetic data and association data among 

individual whales. Chivers et al. (2007) analyze genetic samples available through 2006 by 

comparing mitochondrial haplotypes of false killer whales sampled nearshore (<30 km) around 

the islands of O‘ahu, Maui and Hawai‘i (n=62) with samples from Mexico (n=6), Panama 

(n=16), Palmyra Atoll (n=6), and from offshore waters around Hawai‘i (>139 km from shore, 

n=6), as well as areas farther away (North Atlantic, Indian Ocean, Western Pacific). No samples 

were available at intermediate distances from the islands. They concluded that whales sampled 

near the main Hawaiian Islands are demographically isolated from those in offshore waters of the 

EEZ and elsewhere in the tropical Pacific. Fifteen mitochondrial haplotypes were documented 

from the central and eastern Pacific, six of which were found in animals around the main 

Hawaiian Islands (Table 1). Four of the six haplotypes (representing 60 of the 62 samples) were 

closely related, differing by only one or two base pairs. Three of the four haplotypes were 

documented only in animals around the main Hawaiian Islands. The dominant haplotype from 

around the main Hawaiian Islands (haplotype 1) occurred in 49 of the 62 samples and was not 

shared with other areas. One other closely related haplotype (haplotype 2, two base-pair 

differences from haplotype 1) found in 9 of the 62 samples from the main Hawaiian Islands was 

shared with 1 of 6 Palmyra samples. The remaining haplotypes were recorded only in single 

individuals from around the main Hawaiian Islands. One of these (haplotype 9, which differed by 

four base pairs) was the most common haplotype in false killer whales off Mexico and Palmyra 

(Chivers et al. 2007). Chivers et al. (2007) noted that samples collected more than 139 km from 

the main Hawaiian Islands were either unique haplotypes (haplotype 6, n =1) or the most 

common haplotype recorded off Mexico and Palmyra (haplotype 9, n = 4). Since this study was 

published, additional biopsy samples have been collected (Table 1) that support the conclusions 

of Chivers et al. (2007). All additional samples collected within 30 km of the main Hawaiian 

Islands (n=14 samples from four groups) and analyzed were either haplotypes 1 or 2. Three 

samples collected about 110 km offshore were either haplotype 9 (n=1) or a previously 

undocumented haplotype (haplotype 25, n =2), similar to a haplotype identified from the Indian 

Ocean (Baird et al. 2008b). The larger sample now includes 74 samples from within 30 km of the 

main Hawaiian Islands, of which 58 represent haplotypes not recorded elsewhere (haplotypes 1, 

3, 4, 5). Of the two shared haplotypes, 15 are haplotype 2 (which has only been recorded from 

one sample elsewhere), and one is haplotype 9 (which is the most common haplotype elsewhere 

in the central and eastern Pacific) (Table 1). 
False killer whales in Hawai‘i 

8

Table 1. Haplotype frequencies of false killer whale samples from the main Hawaiian Islands, 

surrounding areas in the central Pacific, and eastern Pacific. Updated from Chivers et al. (2007). 

Data from S. Chivers, Southwest Fisheries Science Center. Individuals from groups that were 

sampled around the main Hawaiian Islands all link by association in a single social network (see 

Figure 3). 

Sample Collection Region 

Haplotype Main Hawaiian Islands Central Pacific (other) Eastern Pacific ID number O‘ahu Maui Hawai‘i >50 km 

offshore 

Hawai‘i 

pelagic 

outside 

Hawaiian 

EEZ 

Palmyra Mexico Panama 

Total 

1 27 9 19 55 

2 4 11 1 16 

3 1 1 

4 1 1 

5 1 1 

6 1A 1 

7 1 1 

8 1 1 

9 1 2A 3B 3 16 25 

10 3 12 15 

11 5 5 

12 3 3 

13 1 1 

14 1 1 

15 1 1 

16 1 1 

25 2 2 

Total 27 14 33 5 4 6 26 16 131 

Notes to Table 1. AOne sample collected by NMFS observer on longline vessel. BAll three 

samples collected by NMFS observers on longline vessels. 

 Matches from photo-identification data also suggest the existence of two isolated 

populations in the Hawaiian EEZ (Baird et al. 2008a). An analysis of photos available through 

January 2007, including 313 identifications of distinctive and very distinctive individuals 

(including re-sightings), reveals that, with the exception of one group with 19 identified 

individuals between 42 to 70 km offshore, the largest group not linked to a large single social 

network was only two individuals (Baird et al. 2008a). All groups sampled by Chivers et al. 

(2007) around the main Hawaiian Islands link by association into this single large social 

network. No genetic samples were collected from the group of 19 individuals, but this group was 

suspected to be part of the offshore population based on its distance from shore and a lack of 

resightings. Since the analysis of Baird et al. (2008a), the sample size of identifications of 

distinctive and very distinctive individuals (with good or excellent quality photographs) has 
False killer whales in Hawai‘i 

9

increased by 76 percent, with 553 identifications available as of July 20092 (Figure 2). While the 

majority of the new identifications are from the island of Hawai‘i (n=136), there were substantial 

increases in the number of identified individuals available from Kaua‘i (an increase from 1 to 9), 

offshore areas (an increase from 16 to 29), and O‘ahu (an increase from 23 to 79). These 

additional identifications support the hypothesis of two populations that do not associate, an 

island-associated (or insular) population and an offshore (i.e., pelagic) population (Figure 3). 

None of the nine individuals documented off Kaua‘i has been linked to either offshore groups or 

to individuals around the rest of the main Hawaiian Islands (Figure 2), and no genetic samples 

are available from those animals. Satellite-tagged individuals from the insular stock have utilized 

waters around Kaua‘i (see below), but further research is needed to determine if the individuals 

that have been photo-identified off Kaua‘i that do not link by association to either stock are part 

of a third population or are members of one of the two known populations. 

Figure 3. Social network diagram of false killer whales photo-identified around the main 

Hawaiian Islands and offshore (40-130 km) from 1986 through May 2009. Updated from Baird 

et al. (2008a). Only distinctive and very distinctive individuals with good or excellent quality 

photographs are shown. Individuals encountered close to shore around O‘ahu, Maui, Lana‘i and 

Hawai‘i are shown in red circles. All except four individuals photo-identified close to shore 

around these islands are linked in a single social network. Individuals encountered close to shore 

 

2 Encounters off O‘ahu in October 2009 and Hawai‘i in December 2009 with groups from the insular stock by the 

Pacific Islands Fisheries Science Center and Cascadia Research Collective have not yet been fully analyzed.
False killer whales in Hawai‘i 

10

around Kaua‘i are shown in blue circles. Individuals encountered >40 km offshore are shown in 

red triangles. Note given the long time span many individuals in the network are likely to have 

died and others became distinctive during the time frame. 

4.B. Population ranges, individual movements, and potential boundaries/overlap 

 There are several sources of available information for assessing the range of each 

population and proposed boundaries between them. These include sightings from ship-based and 

aerial surveys, data from satellite tags, and observations by observers on fishing vessels. Shipbased sightings and observer data are sometimes accompanied by genetic samples or 

photographs that can be used to assess population identity. In terms of broad-scale distribution, 

sightings by observers on fishing vessels indicate that false killer whales are distributed 

throughout the central and eastern half of the Hawaiian EEZ as well as in international waters 

between Hawai‘i and Palmyra, within the Palmyra EEZ, and in international waters north of the 

Hawaiian EEZ (Chivers et al. 2007). 

 Sightings of photo-identified individuals from the insular population show that a large 

proportion of individuals documented off O‘ahu were also seen off the island of Hawai‘i, 

indicating that movements between those islands occur regularly (Baird et al. 2008a). Satellite 

data from three groups of insular individuals reveal that movements may occur rapidly, on the 

order of days (Baird et al. in press). Aerial survey data from around the main Hawaiian Islands 

show false killer whales occur on both the windward and leeward sides of the main Hawaiian 

Islands (Mobley et al. 2000; Figure 4). Individuals that were satellite-tagged on the leeward sides 

of Hawai‘i and O‘ahu used both leeward and windward sides of the islands, often moving from 

windward to leeward sides and back within a day (Baird et al. in press, Baird et al. unpublished; 

Figure 5). This suggests that it is unlikely there is a separate windward population of the species. 

Some of the false killer whales satellite-tagged off the island of Hawai‘i remained around the 

island for extended periods, but all three groups ranged widely among the main Hawaiian 

Islands, with one individual moving to the east coast of the island of Kaua‘i. On average, 

individuals used similar water depths and moved to similar distances offshore on the windward 

and leeward sides. The farthest movements offshore and into the deepest waters were 

documented off the leeward sides of the islands (Baird et al. in press). Individuals from all three 

groups satellite-tagged off Hawai‘i moved into waters greater than 80 km offshore (83, 87, and 

96 km). False killer whales from three groups satellite-tagged off O‘ahu in October 2009 moved 

to the west side of Kaua‘i and Ni‘ihau as well as ranging east among the main Hawaiian Islands, 

moving as far as 110 km from shore3

. 

 Although the location/movement data set from satellite-tagged individuals represents the 

largest and least biased data set for range of the insular population (more than 3,000 locations 

prior to tag deployments in October and December 2009), a number of considerations need to be 

borne in mind when making inferences (Baird et al. in press). Prior to the October 2009 taggings, 

movement/location data from satellite-tagged individuals were only available for five months of 

the year, individuals from only three groups were tagged, and there was considerable variation 

among individuals within groups as well as among groups (Baird et al. in press). Also, all 

individuals prior to October 2009 were tagged off the island of Hawai‘i, and individuals varied in 

 

3

 Data from these tags are still being obtained and have not yet been analyzed. 
False killer whales in Hawai‘i 

11

habitat use when around the island of Hawai‘i versus off other islands. In general, the tagged 

individuals spent more time off the island of Hawai‘i than off other islands, yet encounter rates 

for groups from the Hawai‘i insular stock from sighting surveys are approximately twice as high 

off the islands of O‘ahu and Maui than off the island of Hawai‘i (Baird et al. unpublished), 

emphasizing that movement patterns for some period after individuals are tagged are biased 

towards the area/island where they were tagged. Thus it may be premature to use the data set to 

estimate the proportion of time individuals spend off different islands or at different distances 

offshore. The movement data from tagged animals was obtained over an 18-month time span, 

and it is likely that movement patterns vary over time depending on short- and long-term 

changes in density and movement patterns of their prey species. In addition, if individuals learn 

that fishing gear provides a reliable source of food, changes in movement patterns or habitat use 

could occur (e.g., Chilvers and Corkeron 2001). There may be variation in movement patterns 

within a population depending on whether particular individuals or groups depredate fish from 

fishing gear (see Powell 2009). Some individuals within the insular population show clear signs 

of fishery interactions (Baird and Gorgone 2005), and tagging those individuals, or others closely 

associated with them, may be necessary to assess such variation. 

18

19

20

21

22

23

-162 -161 -160 -159 -158 -157 -156 -155 -154

Longitude (degrees W)

Latitude (degrees N)

Feb-Sep longline boundary

Oct-Jan longline boundary

Kaua'i

O'ahu

Hawai'i

Maui

Figure 4. Sightings of false killer whales in aerial surveys from 1993, 1995, and 1998 

(from Mobley et al. 2000). The seasonal longline exclusion boundaries are shown. The February 

through September longline boundary is currently considered by NMFS to be the boundary 

between the Hawai‘i insular and Hawai‘i pelagic stocks (Carretta et al. 2009a). 
False killer whales in Hawai‘i 

12

18

19

20

21

22

23

-162 -161 -160 -159 -158 -157 -156 -155 -154

Longitude (degrees W)

Latitude (degrees N)

Insular stock

Pelagic stock

Feb-Sep longline boundary

Oct-Jan longline boundary

Haw ai'i

Kaua'i

 Figure 5. Locations of satellite-tagged false killer whales (from Baird et al. in press). 

Little is known about the movements and range of individuals from the Hawai‘i pelagic 

stock. Based on a continuous distribution of sightings from longline observers across the EEZ 

boundary, it is likely that the animals found in international waters are part of the same 

population as the Hawai‘i pelagic stock. One individual from the pelagic stock that was satellitetagged approximately 124 km offshore of the island of Hawai‘i moved to within 62 km of shore 

and as far as 210 km from shore over a period of 15 days (Baird et al. in press). Individuals likely 

to be from the pelagic stock have been documented as near as 42 km to shore (Baird et al. 2008a; 

Figure 5). 

 In the 2008 and draft 2009 NMFS stock assessment reports, the boundary between the 

pelagic and insular stocks was provisionally set at the outer boundary of the longline exclusion 

zone around the main Hawaiian Islands (Figure 4; Carretta et al. 2009a, 2009b), but it was noted 

that the boundary may be revised as additional information becomes available. 

4.C. Estimates of abundance/population size 

 Abundance of false killer whales in Hawaiian waters has been estimated using linetransect methods from both aerial and shipboard surveys, and population size has also been 

estimated using mark-recapture methods from photo-identification data. Such estimates were 

produced prior to the split of false killer whales into insular and pelagic stocks, but recent reassessment allows for these estimates to be attributed to one or the other stocks. A summary of 

population estimates available by year and by stock is presented in Table 2. 
False killer whales in Hawai‘i 

13

Table 2. NMFS Hawai‘i false killer whale population and status of stock designations and best 

population estimates. The first stock assessment was undertaken in 1995. The 2009 assessments 

are draft assessments. 

Year NMFS stock 

designation 

NMFS best 

estimate of 

population size 

NMFS status of 

stock 

designation 

Source of population 

estimate 

1995 Hawaiian None available Unknown 

1996 Hawaiian None available Unknown 

1997 Hawaiian None available Not assessed 

1998 Hawaiian None available Not assessed 

1999 Hawaiian None available Not assessed 

2000 Hawaiian 121 (CV = 0.47)* Strategic Mobley et al. 2000 

2001 Hawaiian 121 (CV = 0.47)* Strategic Mobley et al. 2000

2002 Hawaiian 121 (CV = 0.47)* Strategic Mobley et al. 2000

2003 Hawaiian 121 (CV = 0.47)* Strategic Mobley et al. 2000

2004 Hawaiian 268 (CV = 1.08) Strategic Barlow 2003 

2005 Hawaiian 268 (CV = 1.08) Strategic Barlow 2003 

2006 Hawaiian 268 (CV = 1.08) Strategic Barlow 2006 

2007 Hawaiian 484 (CV = 0.93) Strategic Barlow and Rankin 2007

2008 Hawaiian Pelagic 484 (CV = 0.93) Strategic Barlow and Rankin 2007

2008 Hawaiian Insular 123 (CV = 0.72) Non-strategic Baird et al. 2005 

2009 Hawaiian Pelagic 484 (CV = 0.93) Strategic* Barlow and Rankin 2007

2009 Hawaiian Insular 123 (CV = 0.72) Non-strategic* Baird et al. 2005 

*Now known to be likely insular stock. **Draft report, status not finalized 

 Aerial surveys were undertaken in June and July 1989 to provide a minimum count of 

false killer whales in Hawai‘i (Reeves et al. 2009). Surveys were undertaken only in leeward 

areas off the island of Hawai‘i, Lana‘i and O‘ahu. When groups of false killer whales were 

found, they were circled for as long as necessary for two experienced observers to obtain 

minimum counts. False killer whales were sighted on 14 occasions, all off the island of Hawai‘i. 

Three large groups were documented on three different days, with counts of 380, 460 and 470 

individuals (Reeves et al. 2009). The authors noted that it was unlikely that the entire islandassociated population was concentrated in one area at the time, and thus the true population size 

was likely somewhat larger than 470. These large groups were all documented relatively close to 

shore in areas that were frequently used by satellite-tagged individuals from the insular stock 

(Baird et al. in press), and where individuals from the pelagic stock have not been documented. 

Thus, it seems likely that the large groups of animals seen close to shore were from the insular 

population. 

 The first systematic estimate of abundance for false killer whales in Hawaiian waters was 

based on a series of aerial surveys undertaken from February through April in 1993, 1995, and 

1998 (Mobley et al. 2000). Those surveys covered both windward and leeward sides of all of the 

main Hawaiian Islands, including channels between the islands out to a maximum distance of 

about 46 km from shore. The distances from shore that were surveyed varied but generally 

covered out to 7 nmi (13 km) past the 1,000-fathom (1,828-m) contour (Figure 6). From 14 to 18 

surveys were conducted between February and April in each of the three years. Sightings and 
False killer whales in Hawai‘i 

14

effort from all three years were pooled in the analyses. Using distance sampling, an abundance 

estimate of 121 individuals (CV = 0.47) was calculated (Mobley et al. 2000). The authors noted 

several sources of uncertainty and potential bias. For instance, the survey aircraft did not permit 

observers to detect cetaceans directly below the plane, and the estimates were not corrected for 

individuals that may have been below the surface; thus the estimate was likely negatively biased. 

Figure 6. Example of aerial survey tracklines from 1995 survey (from Mobley et al. 

2000). The 100 and 1000 fathom isobaths are shown. 

 A large-vessel line transect survey of the entire Hawaiian EEZ (HICEAS) was 

undertaken by two NOAA vessels from August through November 2002, covering 17,050 km of 

trackline (Barlow 2006) during approximately five months at sea. Only one on-effort sighting of 

false killer whales was documented, yielding an abundance estimate of 236 individuals (CV = 

1.13), the smallest abundance estimate for any of the 18 species of odontocetes documented 

during the survey (Barlow 2006). This estimate translated into a density estimate of 0.0001 

animals per km2

 for the entire Hawaiian EEZ. This density is more than an order of magnitude 

lower than density estimates for the eastern tropical Pacific (0.0021, Wade and Gerrodette 1993; 

0.0016, Ferguson and Barlow 2003). Such low density is not unexpected given that Hawaiian 

waters are oligotrophic, while other parts of the eastern tropical Pacific have high productivity. 

Although the density of false killer whales in Hawaiian waters was substantially lower than in 

the eastern tropical Pacific, density of other delphinids within Hawaiian waters showed the same 

Kaua‘i 
False killer whales in Hawai‘i 

15

pattern (Wade and Gerrodette 1993, Barlow 2006). Also, within the eastern tropical Pacific, 

density of false killer whales is relatively high only from approximately 5°S to approximately 

15°N, and is an order of magnitude lower north of 15°N (Ferguson and Barlow 2003). 

 In 2005 a large-vessel line transect survey (PICEAS) was undertaken in the Palmyra 

EEZ, the Johnston Atoll EEZ, and in international waters between the Hawai‘i and Palmyra and 

Johnston Atolls EEZs (Barlow and Rankin 2007). Data from this survey were used to produce 

abundance estimates for the Palmyra EEZ and for the remainder of the PICEAS study area 

(including both international waters and the Johnston Atoll EEZ). Data from the 2002 survey of 

the Hawaiian EEZ were also reanalyzed using more advanced analytical methods. The larger 

sightings sample from both surveys was used to reassess estimated survey strip widths. The 

reanalysis also included short-finned pilot whales (Globicephala macrorhynchus) and roughtoothed dolphins (Steno bredanensis) in a multiple covariate analysis to estimate effective strip 

width and determine what covariates to include in the line-transect model (Barlow and Rankin 

2007). The resulting abundance estimate for the outer Hawaiian EEZ (effectively encompassing 

the range of the Hawaiian pelagic stock of false killer whales) was 484 individuals (CV = 0.93). 

This is currently considered by NMFS to be the best estimate of abundance for the Hawai‘i 

pelagic stock of false killer whales (Carretta et al. 2009a). For the Palmyra EEZ, Barlow and 

Rankin (2007) estimated an abundance of 1,329 false killer whales (CV = 0.65) and for the 

remainder of their study area they estimated an abundance of 906 false killer whales (CV = 

0.68). Estimates of other species using the larger samples sizes and more advanced analytical 

methods were not produced. 

 A multi-site mark-recapture estimate of population size of false killer whales around the 

main Hawaiian Islands was generated from individual photo-identification data available for 

2000 through 2004 (Figure 2) from O‘ahu, Maui, and Hawai‘i (Baird et al. 2005). The modelaveraged estimate, taking into account the proportion of “marked” individuals in the population, 

was 123 individuals (CV = 0.72). This estimate, similar to the estimate of Mobley et al. (2000), 

is currently considered by NMFS to be the best available estimate for the Hawai‘i insular stock 

(Carretta et al. 2009a). 

 

4.D. Population trends 

 Because only one systematic survey has been done in offshore waters of the Hawaiian 

EEZ, no trends can be assessed using this method for the Hawai‘i pelagic stock. In theory, 

sighting data from the fishery observer program could be used to assess trends in sighting rates 

for individuals in the Hawai‘i pelagic stock; however, changes in observer protocols and possible 

changes in false killer whale distribution or reactions to vessels in responses to longline fishing 

effort (e.g., learning that longlines may provide a source of food) could obscure changes in 

population size. Thus, no information is available to assess trends for the Hawai‘i pelagic stock. 

 In addition to the three aerial surveys around the main Hawaiian Islands undertaken by 

Mobley et al. (2000) in the 1990s, two additional surveys in 2000 and 2003 (Mobley 2004, 

Mobley pers. comm.) provide a time-series that are used here to assess trends (Table 3). A 

regression of sighting rates over time reveals a significant decline (p = 0.028, r2

 = 0.8429). There 

were no false killer whale sightings in the 2000 or 2003 surveys. It is possible that variations in 

weather conditions or survey methods could have affected sighting rates. To test whether this 
False killer whales in Hawai‘i 

16

was the case, data from sightings of other species in the five years of the aerial surveys were also 

examined to assess trends in sighting rates. Data were used for the four species with the largest 

sample sizes: common bottlenose dolphins, pantropical spotted dolphins (Stenella attenuata), 

spinner dolphins, and short-finned pilot whales (Table 3). These include nearshore and offshore 

delphinids with a range of body sizes that bracket the size of false killer whales. Regressions of 

sighting rates over time for each species independently showed no consistent pattern. Two 

species had slightly increasing trends (common bottlenose dolphin, pantropical spotted dolphin) 

and two had slightly decreasing trends (spinner dolphin, short-finned pilot whale), but trends for 

all four species were not significant (p = 0.75, 0.40, 0.60, 0.82, respectively). To assess whether 

one underlying factor, such as weather, influenced sighting rates, each species’ sighting rate for a 

particular year was considered a replicate sample (i.e., n = 4 for each year). A regression of 

sighting rates for all four species showed no trend (p = 0.89, r2 = 0.001). Thus, it is unlikely that 

weather or change in survey methods was responsible for the declining trend in sighting rates of 

false killer whales. This analysis supports the findings of Reeves et al. (2009) that suggest the 

size of the insular stock of false killer whales has declined markedly. 

 

Table 3. Aerial survey effort and sighting data from J. Mobley, University of Hawai‘i (pers. 

comm.). 

Sighting rate (per 10 on-effort survey hours) 

Year Effort 

(km) 

Effort 

(hrs) 

Mean 

Beaufort 

sea state 

# false 

killer 

whale 

sightings

False 

killer 

whale

Bottlenose 

dolphin 

Pantropical 

spotted 

dolphin 

Spinner 

dolphin 

Shortfinned 

pilot 

whale 

1993 13,618 75.5 3.00 8 1.06 0.662 0.132 1.060 1.457 

1995 17,091 92.3 2.83 9 0.975 2.492 0.542 2.167 1.625 

1998 13,174 71.1 3.08 1 0.141 0.985 1.266 1.266 4.782 

2000 11,007 59.4 3.43 0 0 1.178 2.020 1.347 1.347 

2003 11,925 64.4 3.43 0 0 1.863 0.621 1.087 0.776 

 Reeves et al. (2009) note several additional lines of evidence suggesting that the Hawai‘i 

insular stock of false killer whales has undergone a significant decline in size in recent years. 

One researcher working off the island of Hawai‘i since the mid-1980s has noted that encounter 

rates have declined since he began his studies (D. J. McSweeney, pers. comm. in Reeves et al. 

2009). In addition, in 1989 aerial surveys by Reeves et al. (2009), false killer whales were the 

third most frequently encountered species, representing 16.7 percent of all odontocete groups 

observed, whereas boat-based surveys around the main Hawaiian Islands from 2000 through 

2006 found false killer whales the eleventh most frequently encountered species representing less 

than 2 percent of odontocete sightings (Baird et al. 2008a). 

A comparison of the largest group sizes documented in the 1989 survey with recent 

population estimates for the insular stock also suggests that the population has declined. The 

largest group documented in 1989 contained 470 individuals (Reeves et al. 2009), almost four 

times the estimated population size from more recent surveys (Mobley et al. 2000, Baird et al. 

2005). A preliminary analysis of photo-identification data since the mid-1980s (Figure 2) also 

indicated that the mean annual survival rate of distinctive and very distinctive individuals (i.e., 

adults) appeared lower (0.92) than would be expected for a cetacean with the life history 
False killer whales in Hawai‘i 

17

characteristics of false killer whales (Baird and Barlow unpublished). All available lines of 

evidence thus suggest a decline in the abundance of the insular false killer whale population. 

4.E. Social organization and group structure 

 Shallenberger (1981) reports that false killer whale groups encountered in Hawaiian 

waters are often spread over very wide areas. Baird et al. (2008a) note that estimates of group 

size increase as encounter duration increases because widely dispersed sub-groups, apparently 

acting in concert (e.g., all moving through the area in the same direction), are more likely to 

merge or come into close proximity with one another the longer they are followed. For 

individuals thought to be from the pelagic stock, Baird et al. (2008a) report one encounter with 

the most widely separated sub-groups 28 kilometers apart. Information from satellite tags 

deployed on multiple individuals within a group shows that individuals may separate by more 

than 100 kilometers over periods of hours or days before rejoining (Baird et al. in press4

). Such 

dispersal of individuals apparently acting in concert has implications for the likelihood of a 

group detecting and interacting with fishing gear. That is, the likelihood of depredation occurring 

and the potential for bycatch may be high because individuals within dispersed sub-groups may 

effectively search a large area and converge on captured prey when one sub-group locates a prey 

source (see later discussion). 

 Based on analyses of association data from photo-identified individuals, false killer 

whales in Hawaiian waters appear to have strong long-term bonds (Baird et al. 2008a). However, 

the groups encountered in the field are likely to be an aggregation of multiple smaller stable subgroups with sub-groups joining or leaving the larger aggregation regularly. Since these analyses 

of social organization were completed, the sample sizes of photo-identifications available have 

increased substantially (Figure 2), which will allow for more detailed assessments of association 

patterns. 

4.F. Diet and foraging ecology 

 Cetacean diets are typically assessed by examining the stomach contents of stranded 

animals or fisheries bycaught animals. As noted above, false killer whales strand infrequently in 

Hawaiian waters, and apparently stomach contents from the five stranded false killer whales 

were not saved. However, false killer whales feed during the day, capture large prey, and 

frequently share their prey, including prey caught at depth and brought to the surface (Baird et al. 

2008a); thus, there is information on diet from observational studies. Ten species of pelagic fish 

have been documented as prey of false killer whales from the insular stock around the main 

Hawaiian Island, including seven species caught commercially: yellowfin tuna (Thunnus 

albacares), albacore tuna (T. alalunga), skipjack tuna (Katsuwonus pelamis), broadbill swordfish 

(Xiphias gladius), dolphin fish (or mahimahi, Coryphaena hippurus), wahoo (or ono, 

Acanthocybium solandri), and lustrous pomfret (or monchong, Eumegistus illustrus) (Table 4; 

Baird et al. 2008a). Mahimahi were the most commonly observed prey (Baird et al. 2008a) but 

are also easily recognizable even by relatively inexperienced observers. Thus opportunistic 

observational studies may over-represent the occurrence of mahimahi in the diet. False killer 

 

4 An animation showing movements of five satellite-tagged individuals from the insular population over a 10-day 

period can be viewed at www.cascadiaresearch.org/hawaii/falsekillerwhale.htm
False killer whales in Hawai‘i 

18

whales that are known or thought to be from the pelagic stock have been observed feeding on 

mahimahi and ono (Baird et al. unpublished data). 

Table 4. Prey species documented for false killer whales in Hawaiian waters1. 

English name Hawaiian name Scientific name Source 

Yellowfin tuna Ahi Thunnus albacares Baird et al. 2008a 

Albacore tuna Ahi palaha Thunnus alalunga Baird et al. 2008a 

Skipjack tuna Aku Katsuwonus pelamis Baird et al. 2008a 

Scrawled File fish Loulu or Oilepa Aluterus scriptus Baird et al. 2008a 

Broadbill swordfish A‘u ku Xiphias gladius C. Babbit pers. comm. 

Dolphin fish Mahimahi Coryphaena hippurus Baird et al. 2008a 

Wahoo Ono Acanthocybium solandri Baird et al. 2008a 

Lustrous pomfret Monchong Eumegistus illustrus Baird et al. 2008a 

Threadfin jack Kagami ulua Alectis ciliaris D. Perrine pers. comm. 

1

Aluterus scriptus and Eumegistus illustrus probable identifications. 

The sample size of observations of predation by individuals from the pelagic stock is 

small, and for the insular stock, observations of predation are limited to leeward areas off the 

islands of Hawai‘i, Maui, and O‘ahu. The small sample sizes are not adequate for reliable 

assessments of whether their diets varies seasonally, geographically, or between the insular and 

pelagic stocks. Although observations of predation have been documented incidentally during 

other studies, no directed studies of predation have been undertaken. It is possible that species 

caught at depth are less likely to be documented through observational methods. In addition, the 

likelihood of detecting prey captures or prey sharing may vary with the size of prey and the 

amount of time necessary to capture and subdue the prey. Assessment of prey preferences and 

contributions to overall dietary intake could be undertaken using genetic analyses of fecal 

samples, a method currently being used to assess diets of killer whales (Hanson et al. in press). 

There is limited information available on diel foraging patterns. Data on diving behavior by one 

individual instrumented with a time-depth recorder for more than 28 hours indicated that all deep 

dives (>100 m) occurred during daylight hours, with a maximum dive depth exceeding 2345

 m 

(Baird et al. unpublished). Dive patterns were more regular at night, and swim speed was lower 

and less variable at night, suggesting less foraging at night (Baird et al. unpublished). 

 Information on food intake rates is not available from wild false killer whales but is 

available from captive individuals. Average monthly nutrition data is available from the Hawai‘i 

Institute of Marine Biology for an adult female captive false killer whale (Kina) from January 

2006 through September 2009. Body weight during this period ranged from 476 to 533 kg (mean 

= 476 kg, SD = 16.5), with daily food intake ranging from 14.4 to 21.2 kg (mean = 17.4 kg, SD = 

 

5 The time-depth recorder used recorded only to 234 m, although the tagged whale spent more than eight minutes 

below that depth, thus likely could have been foraging to as deep as 700 m given the rate of ascent and descent 

documented.
False killer whales in Hawai‘i 

19

1.4 kg). Daily food intake in relation to body weight varied from 3.0 to 4.2 percent (mean = 3.4 

percent, SD = 0.3 percent), while daily energy intake varied from 27 to 44 kcal/kg body weight 

(mean = 35.7, SD = 3.6). There was no relationship between daily energy intake rates (kcal/kg 

body weight) and body weight or month, although in the case of the body weight, the range in 

body weight over the 45-month period was small and the whale was an adult during the entire 

time period. 

5. Potential conservation threats

 Although 10 false killer whales were captured alive in Hawai‘i for the captive display 

industry prior to 1980 (Shallenberger 1981), there have been no capture permits requested in 

recent years. Potentially limiting factors are discussed here, focusing on the anthropogenic 

impacts for which there is the most information available or that are thought to have a significant 

potential to affect false killer whale populations in Hawaiian waters in the short term. Some 

longer-term issues, such as the impact of ocean acidification on prey species through food web 

effects (e.g., Fabry et al. 2008, Brewer and Peltzer 2009), are important management concerns, 

but their assessment is beyond the scope of this review. Little is known about diseases in false 

killer whales. However, infectious disease threats also may be an issue for the long-term viability 

of false killer whale populations (Gaydos et al. 2004). Given the nature of false killer whale 

grouping patterns and food sharing (Baird et al. 2008a), infectious diseases may be transmitted to 

a large proportion of a population relatively quickly (Guimaraes et al. 2007). 

 It should be noted that an absence of evidence of an impact by such factors as ship 

strikes, anthropogenic noise sources, ingestion of fishing gear, shooting, or other human 

interactions is not evidence of an absence of impacts. Given the estimated population size of the 

insular stock (123 individuals, Baird et al. 2005), and expected survival rates for long-lived 

odontocetes (e.g., 96 percent annual adult survival), one would expect the death of five adult 

individuals in the insular stock each year due to natural causes. Thus, over the last 20 years 

approximately 100 individual adult false killer whales in the insular stock might be expected to 

have died of natural causes. Over the last 20 years only two dead false killer whales have been 

documented in Hawaiian waters (Maldini et al. 2005, K. West, pers. comm.), which comprises 

only 2 percent of the number of individuals expected to have died of natural causes. There are a 

variety of factors that reduce the likelihood that dead or moribund animals strand or wash ashore 

in Hawai‘i (e.g., strong currents, large numbers of scavenging sharks, fringing reefs) or that dead 

animals will be detected if on a beach (e.g., inaccessibility of many coastlines due to sea cliffs, 

low human population density, particularly on some islands [e.g., Ni‘ihau, Kaho‘olawe]; Faerber 

and Baird in press). All of these factors suggest that the likelihood of detecting dead or moribund 

false killer whales in Hawaiian waters is extremely low. Even much larger and very abundant 

species such as humpback whales are rarely detected stranded in Hawai‘i. Analyses by Antonelis 

et al. (2007) suggest that several hundred die in Hawaiian waters each year, yet typically only 

one or two strandings are documented. 

 Purvis et al. (2000) note that extinction risks in declining species are positively correlated 

with four primary factors: high trophic level, low population density, delayed maturity and low 

reproductive rate, and small geographical range. All of these factors apply to the insular stock of 

false killer whales around the main Hawaiian Islands, and the first three also apply to the pelagic 

stock. The current estimate of PBR for the insular population is 0.8 individuals per year (Carretta 
False killer whales in Hawai‘i 

20

et al. 2009a). Thus, even a low level of anthropogenic mortality could result in a negative 

population trajectory for a species with these characteristics. 

5.A. Persistent organic pollutants 

 Given their high trophic level and life history characteristics such as low reproductive 

rate, delayed maturity, and extended longevity (Kasuya 1986), false killer whales are likely to 

accumulate higher levels of persistent organic pollutants than other cetaceans in Hawaiian 

waters. Persistent organic pollutant levels assessed in blubber biopsy samples from nine 

individuals from the insular stock have been found to be high in PCBs and DDTs (Ylitalo et al. 

2009). As expected, levels were highest in adult males and subadults. Three individuals had 

levels of PCBs that were high enough to potentially influence the health of those individuals 

(Ylitalo et al. 2009). 

5.B. Changes in prey base 

 Reduced prey abundance or reduced size of individual fish (e.g., Sibert et al. 2006) could 

affect false killer whale foraging success and increase the amount of time or energy they must 

expend to meet nutritional requirements. Changes in the relative abundance of mid-trophic and 

upper-tropic level fish could result in increased variability in fish abundance (Polovina et al. 

2009), potentially increasing the variability in rates of false killer whale food intake. Reduced 

food intake combined with increased variability in food availability could result in mobilization 

of persistent organic pollutants sequestered in blubber or reduce nutritional state, potentially 

affecting the immune system response (Jepson et al. 2005, Krahn et al. 2009). Information on the 

population status of fish species known to be prey of false killer whales in Hawai‘i is limited. 

Trends in false killer whale prey abundance are primarily limited to analyses of data on catch per 

unit effort in the longline fishery and nearshore fisheries that catch known false killer whale 

prey, such as the troll fisheries. However, variations in fishing practices over time complicate 

analyses of both catch per unit effort and apparent changes in the size and body weight of caught 

fish over time. 

 Data on average body weight for target fish species and catch per unit effort are available 

from 1987 through 2007 from both offshore longline fisheries and nearshore troll and handline 

fisheries, but quantitative analyses are limited (WPRFMC 2009, see Polovina et al. 2009). 

Utilizing these data, several analyses (presented below) suggest potential declines in either body 

weight or catch per unit effort for some of the prey species eaten by false killer whales. These 

analyses are for a 21-year time period, but it is possible that some fish populations were reduced 

to levels that could have affected false killer whale prey availability prior to 1987 (Sibert et al. 

2006). 

 Data on average body weight of three false killer whale prey species taken by the 

longline fishery from 1987 through 2007 (WPRFMC 2009) show a significant decline in body 

weight over time (yellowfin tuna, regression, p < 0.001, r2

 = 0.66; mahimahi, regression p = 

0.01, r2 = 0.29; skipjack tuna, regression p = 0.003, r2 = 0.38). For yellowfin tuna, mean body 

weight declined from an average of 48 kg from 1987 to 1991 to 30 kg from 2003 to 2007. 

WPRFMC (2009) suggests that this decline likely reflects increasing effort in the EEZ of 

Palmyra Atoll in recent years, although no information is presented to assess this. Catch-per-
False killer whales in Hawai‘i 

21

unit-effort data from WPRFMC (2009, measured in weight of fish per day of fishing effort) for 

yellowfin tuna over the same period in the main Hawaiian Islands handline (regression p < 

0.001, r2 = 0.49) and troll (regression p = 0.023, r2 = 0.24) fisheries also show significant 

declines. These analyses do not take into account potential changes in fishing methods over the 

21-year period but suggest cause for concern that reduction in prey availability or prey size could 

be affecting false killer whale foraging success. Polovina et al. (2009) note more recent (1996–

2007) reductions in catch per unit effort in the tuna longline fishery for albacore tuna and bigeye 

tuna (Thunnus obesus) among other species, and Sibert et al. (2006) note large reductions of the 

biomass of both yellowfin and bigeye tuna stocks in the western-central Pacific Ocean over the 

last 25 years. 

5.C. Ship strikes 

 Accidental ship strikes have the potential to kill or seriously injure both large and small 

cetaceans. Non-fatal ship strikes as evidenced by propeller wounds have been documented for 

most large and medium-sized cetaceans, although it is likely that most propeller wounds on small 

cetaceans would be fatal, thus less likely to be documented. Species that are slow-moving, large, 

or spend a substantial amounts of time at the surface are probably most susceptible to ship 

strikes; however, species that bow ride or show curiosity toward vessels can also be injured or 

killed by propellers. Although infrequent, records document deaths of killer whales due to ship 

collisions; in at least one case this was of a juvenile showing interest in vessels (Laist et al. 2001, 

Gaydos and Raverty 2007). Individuals in both insular and pelagic stocks of false killer whales 

bow ride or wake ride on waves produced by transiting vessels and often come in close 

proximity of propellers on moving vessels (Baird pers. obs.). Thus, there may be at least a low 

risk of false killer whale injury or death from wounds by propeller strikes or collisions. Ship or 

propeller-related deaths of false killer whales have not been reported, but one individual from the 

insular population photographed off O‘ahu in September 2009 bears a fresh wound on the head 

that may be from a propeller strike (Figure 7). 

5.D. Anthropogenic sounds 

 High-intensity anthropogenic sounds have the potential to interfere with the echolocation 

that toothed whales use to detect prey, mask communication they need to maintain contact 

between widely dispersed sub-groups, and, in some circumstances, cause individuals or groups 

to strand. False killer whales off Japan were hunted in drive fisheries utilizing sound to herd 

individuals (Kishiro and Kasuya 1993, Brownell et al. 2008). The U.S. Navy’s Hawai‘i Range 

Complex, which encompasses all of the main Hawaiian Islands, is regularly used for training 

exercises that broadcast high-intensity mid-frequency sound from sonar6

. Although impacts on 

false killer whales have not been documented in Hawaiian waters, the power of methods used to 

detect acoustic impacts is low. In 2004 during a Navy Rim-of-the-Pacific exercise, a large 

number of melon-headed whales (Peponocephala electra) became temporarily trapped in a 

coastal embayment on Kaua‘i that may be have been related to the use of Navy sonar (Southall et 

al. 2006, Brownell et al. 2009). Similar impacts from high-intensity mid-frequency sonar might 

affect false killer whales. Information to assess areas of overlap between the locations where 

 

6 Hawai‘i Range Complex Final Environmental Impact Statement/Overseas Environmental Impact Statement (May 

2008). www.govsupport.us/navynepahawaii/FEIS.aspx
False killer whales in Hawai‘i 

22

mid-frequency sonar is used most frequently and the range of insular or pelagic false killer 

whales is not currently available. 

Figure 7. Top. False killer whale from the insular population documented off O‘ahu in 

September 2009 with linear cut through blowhole, possibly due to propeller strike or hooking. 

Middle/Bottom. Insular individual documented off O‘ahu from April 2008 with a recent dorsal 

fin disfigurement. Middle. Left side of fin showing linear cut on leading edge associated with 

white scar tissue. Bottom. Photograph taken through the water showing top and part of right side 

of fin. Note the linear horizontal scar below the white scar tissue. All photos by Tori Cullins. 
False killer whales in Hawai‘i 

23

5.E. Fishery interactions 

Information on fisheries interactions is available from fishery observer programs, reports 

by fishermen, and observations of free-ranging whales. False killer whales are known to take 

hooked fish off lines (Brown et al. 1966, Mizue et al. 1969). In Hawaiian waters, such 

depredation has been noted in both nearshore troll fisheries and offshore longline fisheries 

(Shallenberger 1981, Nitta and Henderson 1993). Information on how often such depredation 

occurs in the nearshore fisheries is not available. In offshore fisheries, longline fishermen have 

noted that depredation by whales (including both false killer whales and short-finned pilot 

whales) could range from 5 to 60 percent (median = 27 percent) of their annual catch (TEC Inc. 

2009). Depredation rates may change over time in response to reductions in prey availability, 

changes in fishing practices, and as individual whales learn that hooked fish may be a readily 

available prey source, something that has been documented for other cetacean species (Powell 

2009). TEC Inc. (2009) noted that some participants in the Hawai‘i-based longline fishery 

(owners and captains) believe that depredation interactions by false killer whales have increased 

over time. Depredation on hooked fish by false killer whales may result in the death of whales 

due to entanglement in fishing lines or ingestion of hooks. Entanglements may cause drowning, 

amputation of appendages due to wraps and constrictions of fishing gear, or interference with 

swimming and the whale’s ability to catch prey. Ingestion of hooks and associated fishing gear 

may puncture the lining of the digestive tract leading to lethal infections or blockage of food 

passage. 

 Depredation of caught fish also may lead to retaliatory measures by fishermen (Read 

2008). Nitta and Henderson (1993) note that reports of shooting bottlenose dolphins to deter 

them from taking catch in Hawaiian waters have been received since the early 1970s. Smallscale commercial fishermen in Hawai‘i often carry firearms to kill or deter sharks depredating 

catch or occasionally to kill large billfish they catch before pulling them aboard. Environment 

Hawai‘i (1997) notes that “about a dozen dolphins were killed near a fish aggregating device off 

the South Kona coast in August,” based on a witness report filed with the Hawai‘i Division of 

Conservation and Resource Enforcement. Given potential fines and other penalties for shooting 

cetaceans, retaliatory shooting of false killer whales, to the extent they may occur, are now likely 

to happen in areas and at times when no witnesses are present. Because injuries on false killer 

whales re-pigment relatively quickly, detecting non-fatal gunshot wounds more than a few 

months after an incident would be difficult. Because of the black coloration on the mouth-line, 

other types of scarring that are associated with fisheries interactions (e.g., linear mouth-line 

scars) would be much more difficult to detect than for other cetacean species with white mouthlines such as pygmy killer whales (Feresa attenuata). In addition, as noted above, strandings are 

infrequent and thus the carcasses of individual cetaceans that are shot are not likely to wash 

ashore and those that do are unlikely to be found (see Faerber and Baird in press). Thus, there is 

no quantitative information to assess whether or how often deliberate shooting of false killer 

whales or other cetacean species in Hawai‘i may occur. 

 Ingestion of fishing gear from recreational or commercial fisheries has the potential to 

result in death. Ingestion of fishing gear could occur either when hooked fish are taken off lines 

or when a free-swimming fish breaks free or is released from fishing gear with a hook and 

possibly other attached gear (e.g., leader and line) and is eaten by a whale. Wells et al. (2008) 

document 11 cases of fishing gear (all from recreational fisheries) ingested by common 
False killer whales in Hawai‘i 

24

bottlenose dolphins in Florida , and one additional case suggesting either ingested gear or gear 

wrapped around the gape. All 11 cases of ingested gear were documented from carcasses, and in 

at least seven of those cases, the cause of death was attributed to injuries from hooks embedded 

in the mouth, throat, and goosebeak (laryngeal spout) and line wrapped around the goosebeak 

(Wells et al. 2008). Some of those cases apparently involved consumption of free-swimming fish 

carrying attached hooks (Gorzelany 1998). In the other four cases, ingested gear was considered 

a contributing factor for one animal and may have played a role in mortality for two others 

although the cause of death varied (Wells et al. 2008). The magnitude of this issue can be 

significant; in Sarasota, Florida, an estimated 2 percent of the resident bottlenose dolphin 

community died from gear ingestion in 2006 (Powell and Wells 2009, R. Wells, pers. comm.). 

Given the combined level of fishing effort by all fisheries in Hawai‘i, the potential frequency of 

depredation (Nitta and Henderson 1993), and the overlap between false killer whale diets and 

fish species targeted by commercial, recreational, and subsistence fisheries in Hawai‘i, ingestion 

of fishing gear may be an important threat to false killer whales in Hawaiian waters. 

 For insular false killer whales in Hawai‘i, Baird and Gorgone (2005) noted that the rate of 

dorsal fin disfigurement, likely caused by line injuries, was approximately four times higher than 

for any of the other 13 populations of eight species of odontocetes for which dorsal fin 

disfigurement data were available. They suggest that this high rate of dorsal fin disfigurement in 

comparison to other odontocete populations is an indicator of relatively frequent interactions 

between individuals from the insular population and fishing gear (Baird and Gorgone 2005). 

Since this analysis, one additional individual from the insular population documented in April 

2008 was observed with a dorsal fin disfigurement possibly due to fishing line (Figure 7). As 

noted earlier, false killer whale wounds re-pigment quickly, limiting the detection of such 

wounds. Given the visible white scar tissue, this injury was likely less than six to 12 months old, 

suggesting that fisheries interactions with this population continue. 

 There are a variety of large-scale and small-scale commercial fisheries in Hawaiian 

waters, as well as a substantial number of recreational fishermen and some subsistence fisheries. 

Although there are clearly large numbers of recreational fishermen throughout the main 

Hawaiian Islands and subsistence fishing is an important activity for many Native Hawaiians, 

there is no license system is in place for recreational or subsistence fisheries. Thus reliable 

records of their numbers are not available. The Hawai‘i-based longline fishery is currently the 

largest fishery in Hawai‘i (WPRFMC 2009), although other fisheries predominated prior to the 

1970s (Pooley 1993). Recent observer data are available only for this fishery, which has been 

recognized as a primary source of false killer whale serious injury and mortality since 2000 

(Forney et al. 2000). Other fisheries that could cause death and injuries to false killer whales 

could include shortline and kaka line fisheries, troll fisheries, and other hook and line fisheries. 

Shortline and kaka line fisheries both use gear similar to longline fisheries, but lines are 

restricted to less than one nautical mile in length. Multiple lines may be set at one time, however. 

The kaka line fishery is regulated by the state of Hawai‘i and is generally prosecuted in relatively 

nearshore waters, while the shortline fishery was added to the federal List of Fisheries for 20107

and is generally prosecuted in offshore waters. There are anecdotal reports of the bycatch of 

“blackfish” (potentially including any of false killer whales, pygmy killer whales, melon-headed 

whales, or short-finned pilot whales) in nearshore shortline or kaka line gear (J. McDonald pers. 

 

7 50 CFR Part 229 (Federal Register 74(219):58859-58901.
False killer whales in Hawai‘i 

25

comm.), and it is likely that false killer whales are one of the species taken, given their tendency 

to depredate fish off lines. Because of data limitations for these fisheries, it is not possible to 

assess interaction probabilities, but observer programs are warranted given the similarities in 

gear types with longline fisheries and the anecdotal information on bycatch, as well as the 

overlap (particularly with kaka line gear) with individuals from the Hawai‘i insular stock of false 

killer whales. Information on exactly where these fisheries are prosecuted and what species are 

targeted are limited because of confidentiality issues as well as cases where fishermen use a 

variety of gear types simultaneously and thus underreporting the use of kaka line or shortline 

gear. 

The remainder of this section focuses on observed bycatch records and estimated bycatch 

for the Hawai‘i-based longline fishery (see Boggs and Ito 1993, Gilman 2007, WPRFMC 2009). 

Information on catches and area of fishing for this fishery are available from the Hawai‘i 

Longline Fishery Logbook program8

. Information on false killer whale bycatch and other 

observer data are from Forney and Kobayashi (2007), Forney and McCracken (2008), 

McCracken and Forney (2008), and unpublished data from the NMFS Pacific Islands Regional 

Office (PIRO). 

Longline fishing in Hawaiian waters began in 1917, and through the 1970s it was carried 

out from relatively small boats (12–19 m) typically fishing within 40 km of shore (Boggs and Ito 

1993). Over the last 30 years, Hawai‘i long-line fishing has undergone a number of changes in 

regulatory measures, fishing effort, and monitoring requirements. Relevant regulatory and 

monitoring changes are summarized in Table 5. Prior to 1992 longline fishing occurred around 

the main Hawaiian Islands (Boggs and Ito 1993, He et al. 1997); since 1992 a longline exclusion 

zone has existed around the main Hawaiian Islands (Figure 4). This has been characterized as a 

“25–75 nautical mile exclusion zone,” although the distance between the boundary and the main 

Hawaiian Islands varies depending on the area as well as seasonally. The boundaries of the two 

seasonal exclusion areas were set as amendments to the Pelagic Fisheries Management Plan 

based on coordinates of inflection points along its perimeter. To assess the actual distance 

between the boundaries and the main Hawaiian Islands, a GIS analysis was undertaken, using 

locations at 10-km intervals along the boundary line, determining the distance to the closest point 

of land at each 10-km node. From February through September, the closest that longline fishing 

is allowed to the main Hawaiian Islands is 78.6 km (42.4 nm), and less than 7 percent of the 

boundary is between 75 and 85 km from shore (Figures 4, 8). From October through January, the 

closest point is 45.1 km (24.3 nm) from land. More than 25 percent of the boundary during this 

period lies between 45 and 50 km from shore, but some parts of the boundary are no closer than 

194 km (104 nm). 

 The number of vessels in the longline fleet more than doubled between 1987 and 1989 

(37 in 1987, 88 in 1989), and by 1991 it had increased to 141 vessels (WPRFMC 2009). In 2007 

there were 129 active vessels (Figure 9). Although the number of vessels in the fleet has 

fluctuated between about 100 and 140 since 1990, the number of hooks in the water has 

increased steadily over that period (Figure 9). The increase in the number of hooks reflects, at 

least in part, an increase in the number of vessels fishing for tuna with deep-set gear compared to 

those targeting swordfish with shallow-set gear (Figure 10). Deep-set gear is set at sunrise at 

 

8 Available from www.pifsc.noaa.gov/fmsd.reports.php
False killer whales in Hawai‘i 

26

February 1 - September 30

0

5

10

15

20

25

30

45-50 85-90 125-130 165-170

Distance from shore (km)

Percentage of boundar

y

October 1 - January 31

0

5

10

15

20

25

30

45-50 85-90 125-130 165-170

Distance from shore (km)

Percentage of boundar

y

depths of 100 to 400 m (median depth of approximately 250 m; Bigelow et al. 2006). Because of 

the way the gear is suspended, the depth of hooks on any particular line may vary by several 

hundred meters. Retrieval begins at or after sunset and typically takes three to six hours to 

retrieve all the gear. Shallow-set gear is set at sunset at depths to approximately 50 m and is 

retrieved before or at sunrise. 

Figure 8. The distance from shore of the main Hawaiian Islands of the long-line 

exclusion boundary for October through January (top) and February through September 

(bottom). See Figure 4 for map of boundaries. 
False killer whales in Hawai‘i 

27 

Table 5. Selected regulatory and monitoring changes for longline fishing in Hawai‘i. Year/Month Regulatory or monitoring changes 1990 Nov Implementation of log-book program with 100% coverage for recording of catch and fishing effort 1991 Oct Three-year moratorium on new entry into fleet imposed 1991 Oct Exclusion zone implemented around Northwestern Hawaiian Islands (“50 nm”) to protect monk sea1991 Oct Requirement for implementation of NMFS-owned vessel monitoring system (VMS) transmitters, w

monitored by NMFS Office of Law Enforcement to ensure compliance with protected areas 

1992 Mar Exclusion zone around main Hawaiian Islands to reduce conflict with near-shore fisheries 1992 Nov Modification of main Hawaiian Island Exclusion zone with northern and eastern boundary contracti

islands from October 1 through January 31 each year 

1994 Jun Start of NMFS longline observer program 1994 Jun Limited entry program instituted (164 vessels maximum, maximum length 101’) 2000 Increase in observer coverage in swordfish component of longline fleet to 100% and 20% observer 

deep-set tuna fleet. 

2002 Jun Ban on swordfish fishing north of the equator to Hawai‘i-based fleet for turtle protection 2004 Hawai‘i longline fishery reclassified as Category I fishery in 2004 List of Fisheries. Re-opening of 

with new turtle protection requirements, including use of circle hooks instead of J hooks 

2006 Jun Establishment of Papahānaumokuākea National Marine Monument around Northwestern Hawaiian 

exclusion of long-line fishing (boundaries similar to “50 nmi” exclusion zone) 

2008 Dec Hawai‘i longline fisheries officially split into a Hawai‘i deep-set (tuna target) longline and Hawai‘i 

(swordfish target) longline fishery in the List of Fisheries. 
False killer whales in Hawai‘i 

28 

0

200

400

600

800

1000

1200

1400

1600

1800

1990 1992 1994 1996 1998 2000 2002 2004 2006 2008

Year

Number of trips

# tuna trips

# swordfish and mixed trips

total trips

0

20

40

60

80

100

120

140

160

1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008

Year

# longline vessels 

0

5

10

15

20

25

# hooks (millions) 

# longline vessels

# hooks total

 Figure 9. Number of Hawai‘i-based longline vessels and number of hooks in the water by 

year from the longline fishery. Data from WPRFMC (2009). 

Figure 10. Number of trips per year for Hawai‘i-based longline vessels by primary 

fishing method (deep-set for tuna or shallow-set for swordfish). Data from WPRFMC (2009). 
False killer whales in Hawai‘i 

29

Observer effort in the fishery began in 1994. There is no quantitative information to 

assess bycatch prior to that date. Given that longline fishing occurred closer to shore prior to the 

implementation of the 1992 exclusion area, it is likely that interactions between false killer 

whales in the insular stock and the longline fishery were higher before 1992 than they have been 

more recently, unless movement patterns of individuals from the insular stock have changed in 

response to the boundary implementation. The percentage of observer coverage in the longline 

fleet has varied over time (Table 6). Prior to 2000 it averaged less than 4 percent (Forney and 

Kobayashi 2007). Between 1994 and 1999 a combined total of 874 tuna sets were observed 

(approximately 3.4 percent of all tuna sets). Based on data from 1994 through 2004, the average 

rate of take (i.e., deaths and serious injuries) of false killer whales in deep-set longline gear was 

0.88 per 1,000 sets (Forney and Kobayashi 2007). Given the low level of observer coverage 

compared to more recent years, the likelihood of any false killer whale takes being documented 

in the deep-set fishery was low prior to 2000. 

 Depredation of longline-caught fish by both sharks and cetaceans is widespread 

throughout the fishery. If fish remains are left on hooks, it is possible to assess whether sharks or 

cetaceans are responsible for depredation, but as most depredation is not witnessed by observers, 

there is no information available to assess what proportion of the cetacean depredation is by false 

killer whales rather than by other cetacean species. Overall false killer whales are the most 

frequently recorded species of cetacean taken in the fishery; the number of observed false killer 

whale takes accounted for more takes than the next three most frequently recorded species 

combined (i.e., Risso’s dolphin [Grampus griseus], short-finned pilot whale, common bottlenose 

dolphin: Forney and Kobayashi 2007). The first observed take of a false killer whale in the 

fishery was in 1997. Between 1997 and 2007 there were 11 observed takes inside the Hawaiian 

EEZ, 9 on deep-set (tuna) longlines and 2 on shallow-set (swordfish) longlines. In addition, 14 

observed takes have been recorded outside of the Hawaiian EEZ, including 4 inside the Palmyra 

Atoll EEZ (Figure 11). Overall take rates have been highest at Palmyra Atoll (Forney and 

Kobayashi 2007). Estimates of annual takes within the Hawaiian EEZ have varied by year from 

0 to 74 (Table 6; Forney and Kobayashi 2007). Over the 11-year period, the total estimated take 

(deaths and serious injuries) of false killer whales in the Hawaiian EEZ was approximately 124 

whales. 

 There are several reasons why estimates of false killer whale bycatch may be negatively 

biased. In addition to the 11 observed takes in the Hawaiian EEZ between 1997 and 2007, 7 

observed takes were not identified to species but could have been false killer whales (Table 6). 

The NMFS assesses observer notes for all bycaught animals that cannot be classified to species 

in the field to determine the possible or probable species. Five of those seven cases were 

ultimately classified as “either false killer whale or short-finned pilot whale,” one was classified 

as “one of either false killer whale, short-finned pilot whale or Risso’s dolphin,” and the last one 

was classified as one of any of seven species of delphinids (including false killer whales). A 

valid approach to incorporate these takes would be to prorate these takes to the respective species 

based on the ratios at which identified species have been taken in the fishery; this could also 

incorporate latitude in assessing species probabilities as there is latitudinal variation in species 

bycaught. This would reflect a more accurate bycatch level, but this has not yet been done. 
False killer whales in Hawai‘i 

30 

Table 6. Information on observer coverage, observed false killer whale serious injuries and mortalities, and estima(serious injuries and/or mortalities) within the Hawaiian EEZ. Information from Forney and Kobayashi (2007), Fo(2008) and McCracken and Forney (2008). 

Year Percent observer 

coverage (sets) 

combined deepand shallow-set 

Observed # 

false killer 

whale serious 

injuries or 

mortalities 

Fishery type 

bycatch 

documented 

PBR Point estimates of 

combined 

mortalities and 

serious injuries 

(CV) 

Five-year mean 

annual takes 

(CV) 

s

1994 4.4% 0 N/A ND 0 - 1995 4.3% 0 N/A ND 0 - 1996 4.6% 0 N/A ND 0 - 1997 2.2% 1 Shallow-set ND 74 (1.0) 4.8 1998 3.2% 1 Shallow-set ND 12 (1.0) 9.4 1999 4.2% 0 N/A ND 0 9.4 2000 10.6% 0 N/A 0.8 0 9.4 2001 25.0% 0 N/A 0.8 0 9.4 2002 23.1% 0 N/A 0.8 0 7 2003 23.9% 2 Deep-set 0.8 8 (0.71) 4.6 2004 24.0% 3 Deep-set 1.0 13 (0.58) 4.2 (0.43) 2005 33.0% 2 Deep-set 1.0 3 (1.0) 4.9 (0.41) 2006 20.1% 1 Deep-set 1.0 6 5.7 (0.64) 2007 25.4% 1 Deep-set 2.4 8 7.4 (0.19) 

Total 11 124 

Note: Methods used to estimate bycatch rates vary among sources, most recent sources (2008) used when informa

on analysis of observer descriptions by K. Forney, NMFS, five were false killer whales or short-finned pilot whale

whale, short-finned pilot whale or Risso’s dolphin, and one was any one of seven species of small delphinid (incluwhale).
False killer whales in Hawai‘i 

31 

Figure 11. Locations of hooked false killer whales in the Hawai‘i-based longline fishery 

from 1997 through July 2009 (n=41), including mortalities, serious injuries, non-serious injuries, 

and cases where outcome has not yet been classified (i.e., records from 2009). Location data 

from Pacific Islands Regional Office, National Marine Fisheries Service. Locations where 

hooked individuals were first detected not noted for seven records; in these cases the location 

where the set haul began is used. 

Another possible source of negative bias is that bycatch estimates do not account for 

hooked animals that break off fishing gear before it is retrieved. Evidence of such interactions 

may be reflected by lost fishing gear, including hooks lost from branch lines, the separation of 

branch lines from main lines, or loss of entire segments of main lines. When main lines break, 

observers record the number of main line segments that are retrieved, but because the number of 

branch lines varies along the main line’s length, observers have not recorded when branch lines 

are lost, and there is no current requirement for observers to record when hooks are lost from 

branch lines (E. Forney pers. comm.). As depredation from sharks and several species of 

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

32

34

-183 -181 -179 -177 -175 -173 -171 -169 -167 -165 -163 -161 -159 -157 -155 -153 -151 -149 -147

Longitude (degrees W)

Latitude (degrees N) 

Longline boundary Feb-Sep

Longline boundary Oct Jan

Monument boundary

Genetic samples

False killer whale takes

(serious and non-serious)

Johnston Atoll EEZ

Hawaiian Islands EEZ

Palmyra Atolll EEZ
False killer whales in Hawai‘i 

32

cetaceans is known to occur, assessing what proportion of lost gear is due to hookings of false 

killer whales would require an overall assessment of depredation/bycatch rates by sharks and 

other odontocetes as well as false killer whales. Such analyses may be useful but have not yet 

been done. 

 For purposes of comparing bycatch estimates to PBR levels, NMFS uses a five-year 

running average of bycatch estimates to account for inter-annual variability in various factors. 

Each stock assessment report (SAR) for marine mammals in Hawai‘i is reviewed by the NMFS 

Pacific Scientific Review Group before being circulated for public comment and additional 

review. Thus SARs generally use five years of bycatch data covering a period that ends two 

years before the published date of the SAR (e.g., the 2008 SARs use bycatch data from 2002 to 

2006). The five-year average take rates within the Hawaiian EEZ have exceeded PBR 

consistently each year since bycatch rates and PBR levels were first available in 2000 (Forney et 

al. 2000, Carretta et al. 2009a). In 2008, when two Hawai‘i stocks were recognized based on 

information on stock discreteness, all bycatch in the longline fishery was allocated to the pelagic 

stock. This was based on the locations were bycaught animals were observed and genetic 

analyses using samples collected by fishery observers since 2004. From 2004 through 2006 

genetic samples were obtained from five bycaught false killer whales, two inside the Hawaiian 

EEZ (229 km and 240 km from the main Hawaiian Islands) and three from international waters 

(one just outside the EEZ boundary and two farther offshore; Figure 11). Four of the five 

samples were of mitochondrial haplotype 9, while the fifth was haplotype 6 (Table 1). Although 

haplotype 9 is a shared haplotype (recorded once from the insular population), this haplotype is 

the most frequent haplotype recorded in the eastern Pacific and elsewhere in the central Pacific 

(Table 1; Chivers et al. 2007). Thus, based on frequency, individuals with this haplotype are 

considered to be from the pelagic stock. The location of bycaught animals (determined either by 

exact location or, when that is unavailable, the set’s end location) also indicated the bycaught 

false killer whales were from the pelagic stock (Carretta et al. 2009a). All locations were outside 

of the February-to-September longline exclusion boundary that is currently being used to 

approximate the geographic boundary between the insular and pelagic stocks. 

 There are several issues regarding the allocation of takes between the two Hawaiian 

stocks. From 2004 through 2006, 12 bycaught false killer whales were observed (10 serious 

injuries or deaths, 2 non-serious injuries; PIRO unpublished data) including animals both inside 

and outside of the U.S. EEZ. As noted previously, genetic samples were collected from five of 

these bycaught animals, but samples were not available to assess population identity for the 

remaining seven individuals. Given that an estimated 22 false killer whales were taken within the 

Hawaiian EEZ during this three-year period (Table 6), just 9 percent of the estimated animals 

taken within the EEZ could be attributed to stock on the basis of genetic methods. Two of the 

takes recorded from 2003 without precise locations noted had set end locations outside the 

February-September longline boundary (and thus were allocated to the pelagic stock); however, 

the set start locations were inside the February-September longline boundary (PIRO unpublished 

data). In addition, two takes in the tuna (deep-set) component of the fishery that were classified 

as either false killer whales or short-finned pilot whales (in November 2003 and October 2005) 

were recorded inside of the February-September longline boundary (Forney and Kobayashi 

2007). Within the tuna (deep-set) longline fishery, Forney and Kobayashi (2007) report five 

bycaught short-finned pilot whales and 18 bycaught false killer whales. Given the ratio of the 

two species among the bycatch for which species identification was conclusive, it is most likely 
False killer whales in Hawai‘i 

33

that at least one and possibly both of the individuals documented in November 2003 and October 

2005 were false killer whales. Considering these factors, it seems doubtful that all takes in the 

longline fishery have been from the Hawai‘i pelagic stock. In addition, the failure to account for 

known takes that have not been identified to species negatively biases the bycatch calculations. 

Logbook data from longline fishermen could be used to assess the amount of fishing effort 

within the February-September longline exclusion area. By combining that information with data 

on levels of observer coverage and overall bycatch estimates, it should be possible to estimate 

the probability of takes being documented inside the exclusion area. 

Because depredation is a learned behavior that is passed on maternally (Powell 2009), not 

all individuals within a population may depredate fish off lines. Given that longline gear is 

encountered, it is probable that the likelihood of false killer whales depredating fish off gear 

varies among populations. However, no information is currently available to assess whether this 

is the case with insular and pelagic stocks of false killer whales. Given the restricted home range 

of insular false killer whales and the broad overlap of fishing effort with this home range prior to 

1992 (Boggs and Ito 1993), individuals from the insular population likely interacted with 

longline gear regularly and depredation behavior may have been widespread throughout the 

population. 

 

 In 2008 there were four false killer whale hookings within the Hawaiian EEZ, three in the 

deep-set longline fishery and one in the shallow-set longline fishery. The three in the deep-set 

fishery were classified as serious injuries, and the one in the shallow-set fishery was classified as 

a non-serious injury (K. Forney pers. comm.). Thus, although the stock assessment report for 

2009 had not been finalized as this report was prepared, it is almost certain that false killer whale 

bycatch rates will again exceed the PBR for the Hawai‘i pelagic stock. For the first eight months 

of 2009, four false killer whales had been documented hooked in the Hawaiian EEZ, three in the 

deep-set fishery and one in the shallow-set fishery (PIRO observer program unpublished data). 

Serious injury determinations for those individuals, however, are not yet available. 

 This review has focused on false killer whales within Hawaiian waters and the potential 

impact of interactions with U.S. fisheries. There is, however, additional fishing effort by foreign 

fleets outside U.S. waters (Williams and Terawasi 2009) that likely takes false killer whales. In 

international waters between Hawai‘i and Johnston and Palmyra Atolls to the south, U.S. fishing 

effort is a small fraction of the total longline fishing effort (Williams and Terawasi 2009). Given 

that individuals from the Hawai‘i pelagic stock, as well as the Palmyra Atoll stock, likely move 

frequently across the U.S. EEZ international boundaries, and bycatch by the U.S. fleet alone 

exceeds estimated PBR levels based on the existing population estimates for the remainder of the 

PICEAS study area (Barlow and Rankin 2007, Carretta et al. 2009a), combined bycatch with 

international fleets may well far exceed PBR, further affecting populations within U.S. waters. 

6. Research Recommendations 

 The following research recommendations are divided into three categories: (1) analyses 

that could be undertaken with existing data or samples; (2) analyses that could be undertaken 

with existing data or samples but where conclusions would benefit from additional data; and (3) 

analyses that require additional data or samples. No attempt has been made to set priorities for 

the recommendations or to identify potential funding sources. For some recommended actions, 
False killer whales in Hawai‘i 

34

the costs should be relatively low (e.g., those involving analyses of existing data sets), and for 

others data or samples could be collected to address multiple research goals from single 

platforms or field efforts (e.g., items 1–10 of analyses requiring additional field studies). Sources 

of information for those based on existing data are noted. 

6.A. Analyses of existing data 

1. Assessment of historical and current fishing effort within the insular stock boundary to 

provide a basis for evaluating past and currently undocumented interactions with that 

stock. This should include examining geographic and seasonal changes in fishing effort 

over time. Data are available from the Hawai‘i longline fishery logbook program, Pacific 

Islands Fisheries Science Center (PIFSC), and for nearshore fisheries from the Hawai‘i 

Division of Aquatic Resources, Commercial Fishing and Marine Dealer Report data. 

2. Assessment of the status and trends of primary prey species of false killer whales. This 

could be done by examining changes in catch per unit effort and body weight of known 

prey species, taking into account changes in fishing practices and areas. Data are 

available from the Hawai‘i longline fishery logbook program, Pacific Islands Fisheries 

Science Center, and for nearshore fisheries from the Hawai‘i Division of Aquatic 

Resources, Commercial Fishing and Marine Dealer Report data. 

3. Assessment of boundary violations to assess the extent to which illegal fishing may have 

affected bycatch rates in the insular population of false killer whales. Vessel tracking data 

are available through the NMFS Office of Law Enforcement, Hawai‘i. 

4. Comprehensive characterization of the nature of depredation and interactions between 

false killer whales and longline gear, and examination of correlates and trends. Data are 

available from the PIRO fishery observer program, and some preliminary analyses have 

been conducted by PIFSC and Southwest Fisheries Science Center staff. 

5. Assessment of the frequency of gear loss (loss of main line portions) in the longline 

fishery that could indicate undocumented takes. Data are available from the PIRO fishery 

observer program. 

6.B. Analyses of existing data which would benefit from additional samples or data 

1. Assessment of gene flow within and between populations using microsatellites obtained 

from biopsy samples. Sample size for the insular population is relatively large, but 

additional samples from the offshore population both within and outside the Hawaiian 

EEZ are needed. Additional analyses of mitochrondrial haplotypes with larger samples 

sizes and broader geographic representation will also help refine population structure. 

These analyses are currently ongoing through the Southwest Fisheries Science Center. 

2. Mark-recapture population estimation for the insular stock based on photo-identification 

data available since the analyses of Baird et al. (2005). Data have been compiled by 

Cascadia Research Collective. 

3. Determination of whether members of different false killer whales populations (e.g., 

Hawai‘i insular and pelagic stocks) can be distinguished acoustically, using recordings 

available from the Southwest Fisheries Science Center, Pacific Islands Fisheries Science 

Center, and others. 
False killer whales in Hawai‘i 

35

6.C. Analyses requiring additional field studies or data collection 

1. Examination of the movements of whales in the insular false killer whale population 

during the period when the longline exclusion zone contracts towards the islands (i.e., 

from October through January), using satellite tags. This approach is currently being used 

to assess movements of false killer whales by Baird et al. (in press). 

2. Assessment of year-round habitat use of both the insular and pelagic stocks to determine 

areas of critical habitat and potential overlap with naval training exercises, using satellite 

tags. 

3. Examination of movements of individuals from the pelagic stock using satellite tags to 

assess group movements in relation to stock boundaries and fishing activities. Fishing 

activity data could be obtained from the fishery logbook program or vessel tracking 

system data data to assess movements relative to fishing activities. 

4. Determination of diet using genetic analyses of fecal samples to assess relative 

proportions of different species in the diet and how this may vary seasonally and 

geographically. This approach is currently being used successfully to assess diet of killer 

whales (e.g., Hanson et al. in press). 

5. Assessment of trophic level and variations in diet in relation to population, season, sex, or 

age class through stable isotope and fatty acid analyses of biopsy samples. 

6. Assessment of reproductive status through hormone analyses of biopsy samples. These 

analyses are currently being undertaken for other species of cetaceans through the 

Southwest Fisheries Science Center. 

7. Assessment of population trends from mark-recapture analysis of photo-identification 

data. Given the low encounter rates but high re-sighting rates, variance associated with 

mark-recapture estimates is likely to be substantially lower than for line-transect 

estimates, thus facilitating trend analyses.

8. Assessment of persistent organic pollutant levels (POPs) as well as cytochrome P4501A1 

enzyme (CYP1A1) expression in individuals from both the pelagic and insular stocks, 

particularly males and juveniles, given the high levels of POPs documented in males and 

juveniles by Ylitalo et al. (2009). Understanding how much of the chemical burdens is 

being mobilized in various population members can be assessed with CYP1A1, an 

indicator of the mobilization of endocrine-disrupting compounds (Montie et al. 2008). 

9. Determination of pathogens to assess exposure to viral and bacterial disease agents. This 

could be done through viral screening of fecal samples and sampling of pathogens in 

breath samples. Both techniques are currently being used to assess pathogens in southern 

resident killer whales (e.g., Schroeder et al. 2009). 

10. Assessment of non-fatal fishing gear interactions by collection and examination of 

photographs of scarring on features visible above-water (dorsal fin) and below water 

(mouth-line, pectoral flippers and tail flukes) of false killer whales. The latter could be 

undertaken using a pole camera of bow-riding individuals or through in-water 

photography.

11. Assessment of seasonal use of areas through the deployment of acoustic recording 

packages. These efforts would be particularly valuable if the pelagic and insular stocks 

can be discriminated acoustically. If so, deployment of acoustic recording packages 

should be targeted particularly in areas that are difficult to survey (e.g., offshore 

seamounts, Ka‘ula Rock, windward sides of the islands).
False killer whales in Hawai‘i 

36

12. Population viability analysis of the insular population. Demographic data required to 

undertake a population viability analysis would include age of first reproduction, agespecific birth and death rates, inter-birth interval, and age and sex structure of the 

population, none of which is known for false killer whales in Hawai‘i. Assessment of 

demographic characteristics can be determined through long-term photo-identification 

combined with genetic studies. 

13. Determination of bycatch rates using fishery observers in shortline and kaka line fisheries 

or other fisheries that may take false killer whales. 

14. Assessment of the nature of false killer whale interactions with the longline fishery, 

including possible acoustic cues produced during the setting, soaking, or hauling process, 

and how false killer whales behave around longline gear. 

15. Assessment of reactions of insular false killer whales to playback of sounds associated 

with longline fishing (e.g., setting, hauling gear) to determine reactions and how reactions 

may vary with distance. 

16. Assessment of trends of pelagic stock. Given the high variance associated with the 

current abundance estimate of the pelagic stock, this will require substantial investment 

of resources. 

7. Acknowledgments 

 This was review was funded by the U.S. Marine Mammal Commission. This report 

would not be complete without the information provided by the National Marine Fisheries 

Service, including the Pacific Islands Regional Office (John Kelly, Eric Forney, Kevin Busscher 

for fishery information), the Pacific Islands Fisheries Science Center (Russel Ito and Kurt 

Kamamoto for confirming prey species), and the Southwest Fisheries Science Center (Susan 

Chivers for providing unpublished haplotype data, Karin Forney for providing information on 

bycatch, and Jay Barlow for survival analyses), as well as Joe Mobley of the University of 

Hawai‘i. Paul Dalzell of the Western Pacific Regional Fisheries Management Council provided 

information on fisheries and regulations and quickly answered a long series of questions 

regarding changes in regulations and practices over time. Marlee Breese and Paul Nachtigall, 

Hawai‘i Institute of Marine Biology, provided unpublished information on nutritional intake by 

Kina, their captive false killer whale. Unpublished information from photo-identification of false 

killer whales was provided by Tori Cullins, Dan McSweeney, Erin Oleson, and Dan Salden, as 

well as Daniel Webster and Greg Schorr from Cascadia Research Collective. Annie Gorgone 

provided photo-identification matches for assessing population structure, Sabre Mahaffy assisted 

with social network analyses, and Damon Holzer assisted with GIS analyses. Discussions with 

Jay Barlow, Brad Hanson, Karin Forney, Erin Oleson, Julie Oswald, Shannon Rankin, and Barb 

Taylor were all helpful in refining research recommendations. I thank Jay Barlow, Bob 

Brownell, Susan Chivers, Annie Douglas, Karin Forney, David Laist, Suzanne Montgomery, 

Erin Oleson, Randy Reeves, and Gretchen Steiger for reviewing all or part of the report. 

8. Literature Cited 

Antonelis, G.A., D.W. Johnston and D.K. Mattila. 2007. Enhancement of tropical marine productivity 

through large whale migrations: humpback whales on the Hawaiian wintering grounds. In 

Abstracts of the 17th Biennial Conference on the Biology of Marine Mammals, Cape Town, 

South Africa, December 2007. 
False killer whales in Hawai‘i 

37

Baird, R.W., K.M. Langelier and P.J. Stacey. 1989. First records of false killer whales, Pseudorca 

crassidens, in Canada. Canadian Field-Naturalist 103:368-371. 

Baird, R.W., and A.M. Gorgone. 2005. False killer whale dorsal fin disfigurements as a possible indicator 

of long-line fishery interactions in Hawaiian waters. Pacific Science 59:593-601 

Baird, R.W., A.M. Gorgone, D.L. Webster, D.J. McSweeney, J.W. Durban, A.D. Ligon, D.R. Salden and 

M.H. Deakos. 2005. False killer whales around the main Hawaiian Islands: an assessment of 

inter-island movements and population size using individual photo-identification. Report 

prepared under Order No. JJ133F04SE0120 from the Pacific Islands Fisheries Science Center, 

National Marine Fisheries Service. Available at www.cascadiaresearch.org/robin/hawaii.htm. 

Baird, R.W., A.M. Gorgone, D.J. McSweeney, D.L. Webster, D.R. Salden, M.H. Deakos, A.D. Ligon, 

G.S. Schorr, J. Barlow and S.D. Mahaffy. 2008a. False killer whales (Pseudorca crassidens) 

around the main Hawaiian Islands: long-term site fidelity, inter-island movements, and 

association patterns. Marine Mammal Science 24:591-612. 

Baird, R.W., G.S. Schorr, D.L. Webster, D.J. McSweeney, A.M. Gorgone and S.J. Chivers. 2008b. A 

survey to assess overlap of insular and offshore false killer whales (Pseudorca crassidens) off the 

island of Hawai‘i. Report prepared under Order No. AB133F07SE4484 for the Pacific Islands 

Fisheries Science Center, National Marine Fisheries Service, Honolulu, HI. Available at 

www.cascadiaresearch.org/robin/hawaii.htm. 

Baird, R.W., G.S. Schorr, D.L. Webster, D.J. McSweeney, M.B. Hanson and R.D. Andrews. In press. 

Movements and habitat use of satellite-tagged false killer whales around the main Hawaiian 

Islands. Endangered Species Research. 

Barlow, J. 2006. Cetacean abundance in Hawaiian waters estimated from a summer/fall survey in 2002. 

Marine Mammal Science 22:446-464. 

Barlow, J., and S. Rankin. 2007. False killer whale abundance and density: preliminary estimates for the 

PICEAS study area south of Hawaii and new estimates for the US EEZ around Hawaii. 

Southwest Fisheries Science Center Administrative Report LJ-07-02. 

Bigelow, K.A., M.K. Musyl, F. Poisson and P. Kleiber. 2006. Pelagic longline gear depth and shoaling. 

Fisheries Research 77:173-183. 

Boggs, C.H., and R.Y. Ito. 1993. Hawaii’s pelagic fisheries. Marine Fisheries Review 55:69-82. 

Brewer, P.G., and E.T. Peltzer. 2009. Limits to marine life. Science 324:347-348. 

Brown, D.H., D.K. Caldwell and M.C. Caldwell. 1966. Observations on the behavior of wild and captive 

false killer whales, with notes on associated behavior of other genera of captive delphinids. Los 

Angeles County Museum Contributions in Science 95:1– 32. 

Brownell, R.L., Jr., D.P. Nowacek and K. Ralls. 2008. Hunting cetaceans with sound: a worldwide 

review. Journal of Cetacean Research and Management 10:81-88. 

Brownell, R.L., K. Ralls, S. Baumann-Pickering and M.M. Poole. 2009. Behavior of melon-headed 

whales, Peponocephala electra, near oceanic islands. Marine Mammal Science 25:639-658. 

Carretta, J.V., K.A. Forney, M.S. Lowry, J. Barlow, J. Baker, D. Johnston, B. Hanson, M.M. Muto, D. 

Lynch and L. Carswell. 2009a. U.S. Pacific marine mammal stock assessments: 2008. NOAA 

Technical Memorandum NMFS NOAA-TM-NMFS-SWFSC-434. 

Carretta, J.V., K.A. Forney, M.S. Lowry, J. Barlow, J. Baker, D. Johnston, B. Hanson, R.L. Brownell, J. 

Robbins, D. Mattila, K. Ralls, M.M. Muto, D. Lynch and L. Carswell. 2009b. Draft U.S. Pacific 

marine mammal stock assessments: 2009. Available from SWFSC, 8604 La Jolla Shores Drive, 

La Jolla, CA 92037. 

Chilvers, B.L., and P.J. Corkeron. 2002. Trawling and bottlenose dolphins’ social structure. Proceedings 

of the Royal Society B 268:1901-1905. 

Chivers, S. J., R. W. Baird, D. J. Mcsweeney, D. L. Webster, N. M. Hedrick and J. C. Salinas. 2007. 

Genetic variation and evidence for population structure in eastern North Pacific false killer 

whales (Pseudorca crassidens). Canadian Journal of Zoology 85:783-794. 

Connor, R.C., and K.S. Norris. 1982. Are dolphins reciprocal altruists? American Naturalist 119:358-374. 

Environment Hawai‘i. 1997. Fishery council hears of dolphin deaths, sea turtle slaughter, bird bycatch. 
False killer whales in Hawai‘i 

38

Environment Hawai‘i 8(6):8. 

Fabry, V.J., B.A. Seibel, R.A. Feely and J.C. Orr. 2008. Impacts of ocean acidification on marine fauna 

and ecosystem processes. ICES Journal of Marine Science 65:414-432. 

Faerber, M.M., and R.W. Baird. In press. Does a lack of beaked whale strandings in relation to military 

exercises mean no impacts have occurred? A comparison of stranding and detection probabilities 

in the Canary and Hawaiian Islands. Marine Mammal Science. 

Ferreira, I.M. 2008. Growth and reproduction in false killer whales (Pseudorca crassidens Owens, 1846). 

M.Sc. Thesis, University of Pretoria, South Africa. 

Ferguson, M.C., and J. Barlow. 2003. Addendum: spatial distribution and density of cetaceans in the 

eastern tropical Pacific ocean based on summer/fall research vessel surveys in 1986 – 96. 

Southwest Fisheries Science Center Administrative Report LJ-01-04 (Addendum). 

Forney, K.A., J. Barlow, M.M. Muto, M. Lowry, J. Baker, G. Cameron, J. Mobley, C. Stinchcomb and 

J.V. Carretta. 2000. U.S. Pacific marine mammal stock assessments: 2000. NOAA Technical 

Memorandum NOAA-TM-NMFS-SWFSC-300. 246p. 

Forney, K. A. and D. Kobayashi. 2007. Updated estimates of mortality and injury of cetaceans in the 

Hawaii-based longline fishery, 1994-2005. NOAA Technical Memorandum NMFS-SWFSC-412. 

Forney, K. A. and M. McCracken. 2008. Preliminary estimates of cetacean injury and mortality in 

Hawaii-based longline fisheries during 2006. Unpublished draft document PSRG-2008-16, 

presented to the Pacific Scientific Review Group, January 8-10, 2008, Monterey, CA. 

Gaydos, J.K., and S. Raverty. 2007. Killer whale stranding response. Final report to National Marine 

Fisheries Service Northwest Regional Office, Seattle, WA. 

Gaydos, J.K., K.C. Balcomb, III, R.W. Osborne and L. Dierauf. 2004. Evaluating potential infectious 

disease threats for southern resident killer whales (Orcinus orca): a model for endangered 

species. Biological Conservation 117:253-262. 

Gerrodette, T., W. Perryman and J. Barlow. 2002. Calibrating group size estimates of dolphins in the 

eastern tropical Pacific Ocean. Southwest Fisheries Science Center Administrative Report LJ-02-

08. 

Gilman, E. 2007. USA Hawaii-based pelagic longline swordfish and tuna fisheries: industry practices and 

attitudes towards shark depredation and unwanted bycatch. Appendix 8 in Shark depredation and 

unwanted bycatch in pelagic longline fisheries, industry practices and attitudes and shark 

avoidance strategies. Western Pacific Regional Fishery Management Council, Honolulu, HI. 

Gorzelany, J.F. 1998. Unusual deaths of two free-ranging Atlantic bottlenose dolphins (Tursiops 

truncatus) related to ingestion of recreational fishing gear. Marine Mammal Science 14:614-617. 

Guimaraes, P.R., Jr., M.A. de Menezes, R.W. Baird, D. Lusseau, P. Guimaraes and S.F. dos Reis. 2007. 

Vulnerability of a killer whale social network to disease outbreaks. Physical Review E 76: 

042901. 

Hanson, M.B., R.W. Baird, J.K.B. Ford, J. Hempelmann-Halos, D. Van Doornik, J.R. Candy, C. K. 

Emmons, G. S. Schorr, B. Gisborne, K. L. Ayres, S. K. Wasser, K. C. Balcomb, K. BalcombBartok, J. G. Sneva, and M. J. Ford. In press. Species and stock identification of prey selected by 

endangered “southern resident” killer whales in their summer range. Endangered Species 

Research. 

He, X., K.A. Bigelow and C.H. Boggs. 1997. Cluster analysis of longline sets and fishing strategies 

within the Hawaii-based fishery. Fisheries Research 31:147-158. 

Jepson, P.D., P.M. Bennett, R. Deaville, C.R. Allchin, J.R. Baker, and R.J. Law. 2005. Relationships 

between polychlorinated biphenyls and health status in harbor porpoises (Phocoena phocoena) 

stranded in the United Kingdom. Environmental Toxicology and Chemistry 24:238-248. 

Kasuya, T. 1971. Consideration of distribution and migration of toothed whales off the Pacific coast of 

Japan based on aerial sighting record. Scientific Reports of the Whales Research Institute, Tokyo 

23:37-60. 
False killer whales in Hawai‘i 

39

Kasuya, T. 1986. False killer whales. Pages 178-187 in T. Tamura, S. Ohsumi and S. Arai (editors). 

Report of investigation in search of solution for dolphin-fishery conflict in the Iki Island area. 

Japan Fisheries Agency. 285pp. 

Kishiro, T., and T. Kasuya. 1993. Review of Japanese dolphin drive fisheries and their status. Reports of 

the International Whaling Commission 43:439-452. 

Krahn, M.M., M.B. Hanson, G.S. Schorr, C.K. Emmons, D.G. Burrows, J.L. Bolton, R.W. Baird, and 

G.M. Ylitalo. 2009. Effects of age, sex and reproductive status on persistent organic pollutant 

concentrations in “Southern Resident” killer whales. Marine Pollution Bulletin 58:1522-1529. 

Laist, D.W., A.R. Knowlton, J.G. Mead, A.S. Collet, and M. Podesta. 2001. Collisions between ships and 

whales. Marine Mammal Science 17:35-75. 

Leatherwood, S., R.R. Reeves, W.F. Perrin and W.E. Evans. 1982. Whales, dolphins and porpoises of the 

eastern North Pacific and adjacent Arctic waters: a guide to their identification. National Oceanic 

and Atmospheric Administration Technical Report National Marine Fisheries Service Circular 

444. 

Maldini, D., L. Mazzuca and S. Atkinson. 2005. Odontocete stranding patterns in the main Hawaiian 

Islands (1937-2002): how do they compare with live animal surveys? Pacific Science 59:55-67. 

Marelli, C.A. 1953. Documentos iconograficos sobre cetaceos de las costa Argentina. Ann. Museo 

Nahuel Huapi 3:133-143. 

McCracken, M., and K.A. Forney. 2008. Preliminary estimates of cetacean injury and mortality in 

Hawaii-based longline fisheries during 2007. Unpublished draft document PSRG-2008-11, 

presented to the Pacific Scientific Review Group, November 19-21, 2008, Kihei, Maui, Hawaii. 

Mizue, K., A. Takemura and K. Nakasai. 1969. Studies on the little toothed whales in the west sea area of 

Kyushu- XVI, underwater sound of the false killer whale. Bulletin of the Faculty of Fisheries, 

Nagasaki University 28:19-29. 

Mobley, J. R., S. S. Spitz, K. A. Forney, R. A. Grotefendt and P. H. Forestell. 2000. Distribution and 

abundance of odontocete species in Hawaiian waters: preliminary results of 1993-98 aerial 

surveys. National Marine Fisheries Service Southwest Fisheries Science Center Administrative 

Report LJ-00-14C. 

Mobley, J. R. 2004. Results of marine mammal surveys on U.S. Navy underwater ranges in Hawaii and 

Bahamas. Final report submitted to Office of Naval Research, Marine Mammal Program. Award 

# N000140210841. 

Montie, E.W., P.W. Fair, G.D. Bossart, G.B. Mitchum, M. Houde, D.C.G. Muir, R.J. Letcher, W.E. 

McFee, V.R. Starczak, J.J. Stegeman, and M.E. Hahn. 2008. Cytochrome P4501A1 expression, 

polychlorinated biphenyls and hydroxylated metabolites, and adipocyte size of bottlenose 

dolphins from the southeastern United States. Aquatic Toxicology 86:397-412. 

NRDC. 2009. A petition to list the insular population of Hawaiian false killer whale (Pseudorca 

crassidens) as endangered under the Endangered Species Act. Natural Resources Defense 

Council, New York. 

Nitta, E.T., and J.R. Henderson. 1993. A review of interactions between Hawaii’s fisheries and protected 

species. Marine Fisheries Review 55:83-92. 

Odell, D. K., and K.M. McClune. 1999. False killer whale Pseudorca crassidens (Owen, 1846). In 

Handbook of Marine Mammals (S. Ridgway, ed.). Vol 6, pp. 213–243. Academic Press, New 

York. 

Polovina, J.J., M. Abecassis, E.A. Howell and P. Woodworth. 2009. Increases in the relative abundance 

of mid-trophic level fishes concurrent with declines in apex predators in the subtropical North 

Pacific, 1996-2006. Fishery Bulletin 107:523-531. 

Pooley, S.G. 1993. Hawaii’s marine fisheries: some history, long-term trends, and recent developments. 

Marine Fisheries Review 55:7-19. 

Powell, J.R. 2009. Depredation and angler interactions involving bottlenose dolphins (Tursiops truncatus)

in Sarasota Bay, Florida. M.Sc. Thesis, University of South Florida. 
False killer whales in Hawai‘i 

40

Powell, J.R.. and R.S. Wells. 2009. Depredation and angler interactions involving bottlenose dolphins 

(Tursiops truncatus) in Sarasota Bay, Florida. In Abstracts of the 18th Biennial Conference on the 

Biology of Marine Mammals, Quebec, October 2009. 

Purvis, A., J.L. Gittleman, G. Cowlishaw and G.M. Mace. 2000. Predicting extinction risk in declining 

species. Proceedings of the Royal Society of London B 267:1947-1952. 

Read, A.J. 2008. The looming crisis: interactions between marine mammals and fisheries. Journal of 

Mammalogy 89:541-548. 

Reeves, R.R., S. Leatherwood and R.W. Baird. 2009. Evidence of a possible decline since 1989 in false 

killer whales (Pseudorca crassidens) around the main Hawaiian Islands. Pacific Science 63:253-

261. 

Ross, G.J.B. 1984. The smaller cetaceans of the south east coast of southern Africa. Annals of the Cape 

Provincial Museums (Natural History) 15:173-410. 

Shallenberger, E.W. 1981. The status of Hawaiian cetaceans. Report No. MMC-77/23 of the U.S. Marine 

Mammal Commission. 

Schroeder, J.P., S. Raverty, E. Zabek, C.E. Cameron, A. Eshgihi, D. Bain, R. Wood, L. Rhodes and B. 

Hanson. 2009. Investigation into the microbial culture and molecular screening of exhaled breaths 

of Endangered Southern Resident killer whales (SRKW) and pathogen screening of the sea 

surface microlayer (SML) in Puget Sound. Report prepared for the Northwest Fisheries Science 

Center, Seattle, WA, under Order No. NFFP7100-8-40556. 

Sibert, J., J. Hampton, P. Kleiber and M. Maunder. 2006. Biomass, size, and trophic status of top 

predators in the Pacific Ocean. Science 314:1773-1776. 

Southall, B.L., R. Braun, F.M.D. Gulland, A.D. Heard, R.W. Baird, S.M. Wilkin and T.K. Rowles. 2006. 

Hawaiian melon-headed whale (Peponocephala electra) mass stranding event of July 3-4, 2004. 

NOAA Technical Memorandum NMFS-OPR-31. 

Stacey, P. J., and R.W. Baird. 1991. Status of the false killer whale, Pseudorca crassidens, in Canada. 

Canadian Field-Naturalist 105:189–197. 

Stacey, P. J., S. Leatherwood and R.W. Baird. 1994. Pseudorca crassidens. Mammalian Species 456:1–6. 

TEC Inc. 2009. Cetacean depredation in the Hawaii longline fishery: interviews of longline vessel owners 

and captains. Report prepared for the Pacific Islands Regional Office, National Marine Fisheries 

Service, Honolulu, HI. 

Wade, P.R., and T. Gerrodette. 1993. Estimates of cetacean abundance and distribution in the eastern 

tropical Pacific. Reports of the International Whaling Commission 43:477-493. 

Wells, R.S., J.B. Allen, S. Hofmann, K. Bassos-Hull, D.A. Fauquier, N.B. Barros, R.E. DeLynn, G. 

Sutton, V. Socha and M.D. Scott. 2008. Consequences of injuries on survival and reproduction of 

common bottlenose dolphins (Tursiops truncatus) along the west coast of Florida. Marine 

Mammal Science 24:774-794. 

WPRFMC. 2009. Pelagic fisheries of the western Pacific Region. 2007 Annual Report. Western Pacific 

Regional Fisheries Management Council, Honolulu, HI. 

Williams, P., and P. Terawasi. 2009. Overview of tuna fisheries in the western and central Pacific Ocean, 

including economic conditions – 2008. Western and Central Pacific Fisheries Commission-SC5-

2009/GN WP-1. 

Ylitalo, G.M., R.W. Baird, G.K. Yanagida, D.L. Webster, S.J. Chivers, J.L. Bolton, G.S. Schorr and D.J. 

McSweeney. 2009. High levels of persistent organic pollutants measured in blubber of islandassociated false killer whales (Pseudorca crassidens) around the main Hawaiian Islands. Marine 

Pollution Bulletin doi:10.1016/j.marpolbul.2009.08.029.