Mouthline Injuries as an Indicator of Fisheries Interactions in Hawaiian Odontocetes

Item

Title

Eng Mouthline Injuries as an Indicator of Fisheries Interactions in Hawaiian Odontocetes

Date

2016

Creator

Eng Beach, Kelly

Subject

Eng Environmental Studies

extracted text

MOUTHLINE INJURIES AS AN INDICATOR OF FISHERIES INTERACTIONS
IN HAWAIIAN ODONTOCETES

by
Kelly Ashlyn Beach

A Thesis
Submitted in partial fulfillment
of the requirements for the degree
Master of Environmental Studies
The Evergreen State College
June 2015

© 2015 by Kelly A Beach. All rights reserved.

This Thesis for the Master of Environmental Studies Degree
by
Kelly Ashlyn Beach

has been approved for
The Evergreen State College
by

________________________
Dina L. Roberts, Ph.D.
Member of the Faculty

________________________
Robin W. Baird, Ph.D.
Research Biologist, Cascadia Research Collective

________________________
Date

ABSTRACT
Mouthline Injuries as an Indicator of Fisheries Interactions in Hawaiian Odontocetes
Kelly A. Beach
Evidence from strandings and anecdotal reports indicate that a number of
odontocete species interact with near-shore fisheries in Hawai‘i. In the absence of
observer programs in these fisheries, I evaluated mouthline injuries from known resident
populations of false killer whales and pygmy killer whales, to assess the viability of this
method to document injuries associated with hook and line fishery interactions. All
individuals with mouthlines visible were selected from photo-ID catalogs and scored for
presence of mouthline injuries consistent with fisheries interactions. Ninety-nine false
killer whales and 45 pygmy killer whales had ≥50% of the mouthline visible using fair to
excellent quality photos, with a mean of 58% and 71% mouthline visible, respectively.
Analysis suggests that main Hawaiian Islands insular false killer whales have high rates
of mouthline injuries- 22% of adult and sub-adult individuals with ≥50% mouthline
visible have injuries consistent with fisheries interactions, supporting studies using dorsal
fin injuries that indicate individuals from this population regularly interact with fisheries.
Pygmy killer whales also appear to interact with fisheries at high rates. Of adult and subadult individuals off Hawaiʻi and Oʻahu with ≥50% of the mouthline visible, 31% have
mouthline injuries consistent with fisheries interactions. Since pygmy killer whales feed
primarily at night, and there are few reports of them depredating lines, mouthline injury
analysis provides new insight into fisheries interactions for this species. Scars on pygmy
killer whales heal white and are easier to detect than healed injuries on false killer
whales, thus a greater proportion of individuals with such injuries may be detected for
pygmy killer whales. With both species, the proportion of mouthline visible increased the
likelihood of mouthline injuries being detected (p<0.036). Injury rates are negatively
biased, since those individuals scored as having no mouthline injury may not have had
their entire mouthline visible. Further efforts will aim to identify injury rates in shortfinned pilot whales and rough-toothed dolphins. An examination of differences in injury
rates in a multi-species comparison will also be undertaken to better understand fisheries
interactions in Hawaiian odontocetes.

Table of Contents
ACKNOWLEDGEMENTS…………………………………………………...………..vi
LIST OF FIGURES……………………………………………………………..……..vii
LIST OF TABLES………………………………………………………………..……viii
CHAPTER ONE: LITERATURE REVIEW…………………………………………..1
Introduction…………………………………………………………………………..1
Background and History……………………………………………………………..1
Current Policy………………………………………………………………………..3
Hawaiian Fishing Industry…………………………………………………………...4
Types of Fisheries Interactions………………………………………………………5
Species Background………………………………………………………………….7
False killer whales………………………………………………………………...7
Pygmy killer whales……………………………………………………………….9
Mouthline Injury Assessment………………………………………………………11
CHAPTER TWO: MOUTHLINE INJURIES AS AN INDICATOR OF FISHERIES
INTERACTIONS IN HAWAIIAN ODONTOCETES………………………………12
Introduction…………………………………………………………………………12
Methods……………………………………………………………………………..16
Study Area………………………………………………………………………..16
Volunteer Data: Opportunistic Effort……………………………………………17
Photographic Effort……………………………………………………………...17
Photo-identification………………………………………………………………..18
Mouthline Assessment Protocol………………………………………………….18
Mouthline Scoring………………………………………………………………..19
Mouthline Injury Assessment…………………………………………………….20

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Analysis…………………………………………………………………………..21
Results………………………………………………………………………………..23
False killer whales……………………………………………………………….23
Pygmy Killer whales….………………………………………………………….24
Mouthline assessment evaluation………………………………………………..25
Discussion……………………………………………………………………………..25
False killer whales……………………………………………………………….27
Pygmy Killer whales….………………………………………………………….29
Mouthline assessment analysis….………………………………………………..31
Conclusion…………….…………………………………………………………………32
Mouthline Assessment Research…………………………………………………33
Future Research………………………………………………………………….33
Figures……………………………………………………………………………………35
Tables……………………………………………………………………………….……39
Bibliography………………………………...……………………………….…………..42
Appednix…………………………………………………………………….…………..48

v

Acknowledgements
This project would not have been possible without the collaboration of Cascadia
Research Collective for allowing me to use their data and resources to accomplish this
project. I would especially like to express my immense appreciation for the expertise of
Dr. Robin Baird, who was the catalyst for this study and who patiently provided
guidance, counseling, and opportunity to me throughout this process. I would also like to
thank Sabre Mahaffy for her help with editing and refining, and for teaching me the ropes
as an intern in 2013. I would also like to thank Annie Douglas, Brenda Rone, and Elana
Dobson for advice, support, and encouragement. I would also like to thank all of the
photographers who contributed photos to the CRC catalogs especially the primary
contributors Robin W. Baird, Daniel L. Webster, Brenda K. Rone, Jessica M. Aschettino,
Dan J. McSweeney, Tori Cullins, Deron Verbeck, Chuck Babbitt, Mark Deakos, Dan
Salden, and Jim Ward.
From The Evergreen State College I would like to thank my reader Dr. Dina Roberts for
her advice, enthusiasm, and unwavering support throughout this project and my entire
MES career. I would also like to extend my appreciation to the MES director Kevin
Francis, in addition to all MES faculty, especially Dr. Erin Martin, Dr. Carri LeRoy, and
Gail Wootan who always provided motivation and resources to keep digging deep.
Thank you to the 2015 MES cohort, especially Chelsea Waddell and Sean Greene for
patiently helping me with statistics for this project.
Finally, I am eternally grateful for my grandparents for making this education possible
and supporting me in every way, and to my parents for always encouraging me
throughout this process with enthusiasm and love- this thesis is dedicated to you. Thank
you to Sam Wilson, Fiona Edwards, Katie Wolt, and my roommates Hannah Faulkner
and Kara Karboski for always being there for me with encouragement, motivation,
coffee, and good spirits. Finally, thank you to the whales!

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List of Figures
Figure 1. Tracklines showing total effort for CRC surveys in Hawaiʻi………………….35
Figure 2. Examples of false killer whales and pygmy killer whales with injuries………35
Figure 3. False killer whale mouthline injuries by sex………………………………….36
Figure 4. Contingency table of mouthline injury analysis……………………………….36
Figure 5. False killer whales with notches in mouthline…...............................................37
Figure 6. False killer whales with irregular pigmentation……………………………….37
Figure 7. Pygmy killer whales with irregular pigmentation……………………………..38
Figure 8. Pygmy killer whales with notches and growths….............................................38

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List of Tables
Table 1. Table 1. False killer whale mouthline visibility by population………………...39
Table 2. Count and percentage of false killer whales with mouthline injuries………..…40
Table 3. Mouthline injuries by MHI social cluster of false killer whale………………...40
Table 4. Count and percentage of pygmy killer whale mouthline injuries…...………….41
Table 5. Mouthline injuries in Hawaiʻi and Oʻahu pygmy killer whales ………….…...42

viii

CHAPTER 1 – LITERATURE REVIEW
Introduction
Of the many issues currently facing marine mammals, one of the most pressing in
terms of conservation and management is the interaction between marine fisheries and
marine mammals (Gilman et al., 2006; Forney & Kobayashi, 2007; Read, 2008).
Cetaceans exhibit a wide variety of behaviors and life history traits that cause them to be
especially vulnerable to fisheries interactions (Hall, 2000; Read, 2008). Odontocetes, or
toothed whales, are particularly prone to interaction with various types of fisheries, and
one United States hotspot of interactions is in Hawaiian waters (Forney & Kobayashi,
2007; Hamer et al., 2012). Interactions between commercial fisheries and federally
protected odontocetes have been documented in Hawaiʻi since 1948, and continue to
occur at increasing rates today (Nitta & Henderson, 1993). This is a cause for concern,
particularly for sensitive or threatened and endangered species (Baird et al. 2008). For the
purposes of this study, I focused on the interactions between two different species of
odontocetes and fisheries in Hawaiʻi, and used mouthline assessment as an indicator for
these interactions.

Background and History
Odontocetes are abundant in different areas of the world. Most species are
considered pack animals, socializing and hunting in family groups (Richardson et al.,
1995). Most toothed whales use echolocation to find and hunt prey (Wood & Evans,
1980), and use complex vocalizations to communicate with others in their social groups
0

(Richardson et al. 1995). Odontocete populations around the world are negatively
impacted by a variety of anthropogenic activities, including unsustainable hunting
practices, habitat degradation, military sonar testing, bioaccumulation of persistent
organic pollutants, ship strikes due to increasing shipping activities, and climate change
(Convention on Migratory Species, 2008). However, arguably the largest single threat to
odontocete populations worldwide is direct mortality and injury due to various fishing
operations, which includes accidental hooking and hook ingestion and/or entanglement in
fishing gear, as well as evidence that overfishing is having a negative impact on their
prey species populations (Twiss & Reeves 1999; Hall et al. 2000; Demaster et al. 2001;
Hamer et al. 2012).
Net entanglements and hook and line injuries have been reported in small
cetaceans interacting with various Hawaiian fisheries (Nitta & Henderson, 1993).
Eighteen different species of odontocetes live in Hawaiian waters (Barlow, 2006). These
species’ population statuses range from common and abundant, to cryptic and
endangered, and many of these species are known to interact with various fisheries in
Hawaiʻi.
Injuries and mortality from fisheries interactions are thought to be a major source
of population decline for at least one species of odontocete in Hawaiʻi. Currently, much
conservation attention is focused on the Main Hawaiian Islands insular population of
false killer whales (Pseudorca crassidens), which was listed under the Endangered
Species Act in 2012 due to low population numbers and documented high levels of
interactions with fisheries (NOAA Fisheries, 2012). Historically, the pantropical spotted
dolphin (Stenella attenuata) was a major focus of conservation groups due to their high
1

levels of bycatch mortality in the tuna purse-seine fishery in the 1980s and early 1990s,
and this issue became widely known as the tuna-dolphin problem (Hall, 1998). Spotted
dolphins live within 100 miles of shore, and although they are considered common, the
population in the eastern tropical Pacific is labeled as “depleted” by the National Marine
Fisheries Service (NOAA Fisheries, 2012). This tuna-dolphin problem was one of the
driving factors behind the enactment of the Marine Mammal Protection Act in 1972
(Hall, 1998).

Current Policy
A variety of policies and laws have been put in place to protect marine mammals
in Hawaiʻi. The Marine Mammal Protection Act (MMPA) was enacted in the United
States in 1972, which outlaws the ‘take’ of marine mammals, with take being defined as
to “harass, hunt, capture, kill or collect, or attempt to harass, hunt, capture, kill or collect”
(MMPA, 1972, p. 6). The Convention on International Trade of Endangered Species of
Wild Fauna and Flora (CITES) was an international agreement signed in 1973 by 172
countries that guarantees the international trade of species will not threaten their
existence in the wild (NOAA Fisheries, 2013). This is relevant because all of the species
mentioned in this paper are protected under Appendix II of CITES, which includes
species that are not currently endangered or threatened, but may become so in the near
future in the absence of trade controls (NOAA Fisheries, 2013).
Arguably, the strongest piece of legislation for the conservation of marine
mammals is the Endangered Species Act of 1973, which “protects and recovers imperiled
2

species and ecosystems on which they depend” (US Fish and Wildlife Service, 2013). An
“endangered” species is one that is classified as being “in danger of extinction in all or
significant parts of its range,” while a “threatened” species is one that is “likely to
become endangered in the foreseeable future” (US Fish and Wildlife, 2013). Of the
species I focused on for my research, only the Main Hawaiian Islands insular population
of false killer whales is protected under the Endangered Species Act. Understanding
which protections are already in place for Hawaiian odontocetes is important when
thinking about possible implications for future protections and policies that could be
implemented upon further review of threats to these species.

Hawaiian Fishing Industry
The Hawaiian Islands have a historic fishing industry that dates back before
European colonization of Hawaiʻi, where traditional methods were used by indigenous
Hawaiian people. The commercial and recreational fishing industries in Hawaiʻi are
significant contributors to the Hawaiian economy, as well as contributing to cultural and
historic benefits to Native Hawaiians, residents, and tourists alike. It is estimated that the
commercial fishing contributed $69.7 million dollars to Hawaiʻi’s economy in 2006
(Hawaiʻi Institute for Public Affairs, 2009).
All international ocean fisheries have Exclusive Economic Zones (EEZ), where
countries have the sole right to fish 200 nautical miles out from their shorelines (NOAA
Office of Coast Survey, 2013). In Hawaiʻi’s EEZ area, a variety of different commercial
fisheries exist. Various different fisheries in this zone, include a handline fishery for
bottomfish, a day and night handline fishery for tuna, a handline fishery for Mackeral
3

scad, trolling for tuna and billfish, inshore gillnet fisheries, lobster fishery, and the
longline fishery (Nitta & Henderson, 1993). One of the most lucrative fishing industries
in Hawaiʻi is the Hawaiian longline fishery, which consists of a shallow-set longline
swordfish fishery and a deep-set longline tuna fishery (NOAA Fisheries, 2013).

Types of Fisheries Interactions
Fisheries interactions with marine mammals raise a variety of ecological, social,
and economic concerns (Hall, 2000; Gilman et al., 2006; Read, 2008). There are a variety
of different types of fisheries interactions between marine mammals and fisheries, most
of which are negative for both parties involved. Operational interactions between marine
mammals and fisheries occur when animals directly interact with fishing operations
(Twiss & Reeves, 1999). One example of an operational interaction is depredation, where
marine mammals actually damage or remove fish from fishing gear (Gilman et al., 2006).
Odontocetes can become bycatch by getting caught on a hook while attempting to
depredate a line (Beverton, 1985; Read, 2005; Secchi et al., 2005). Sometimes
individuals depredating lines ingest hooks, which can cause internal injuries or mortality
(Secchi et al., 2005, Wells et al., 2008). Bycatch, also known as the taking of non-target
species due to entanglement or accidental hooking, is another operational interaction that
is detrimental to both odontocetes and fisheries (Hall, 1996). Operational interactions
often result in severe injury and mortality of marine mammals, as well as financial loss
due to gear damage and fish losses (Twiss & Reeves 1999). This information
demonstrates that fisheries interactions are undesirable for both odontocetes and the

4

fishing community in Hawaiʻi.
Read (2008) states that odontocete depredation seems to be increasing in scope,
frequency, and severity. This is particularly a problem for small populations of
odontocetes, because even low numbers of animals taken from these populations can
result in takes that exceed the Potential Biological Removal (PBR) level, which is the
maximum number of individuals, excluding natural mortalities, that can be eliminated
from a marine mammal stock while letting the population reach or sustain its “optimum
stable population” (Carretta et al. 2009; NOAA Fisheries, 2014).
Fisheries interactions can be determined in a variety of ways, each having its own
advantages and disadvantages, including: 1) placing trained observers on fishing vessels,
2) examining wounds and scars on stranded animals, 3) observing entangled animals in
the wild, 4) distributing questionnaire surveys to fisherman (Baird & Gorgone 2005), and
5) examining photographs of marine mammals for injuries. Photograph examination has
recently been used as a cost effective method to estimate fisheries interactions. Baird and
Gorgone (2005) have used photograph examination to assess fin injuries due to fisheries
interactions in Hawaiian false killer whales. For this study, I utilized this type of photoexamination approach to assess scarring and mouthline injury in false killer whales and
pygmy killer whales in Hawaiʻi.

5

Species Background

For my study, I conducted mouthline analysis using photographic data from two
resident Hawaiian odontocete species and their various subpopulations. These species
were false killer whales and pygmy killer whales. Included below are population stock
estimates around the Hawaiian Islands, information on general biology, any relevant
policy information, as well as known information about the levels of fisheries interactions
for each odontocete species.

False Killer Whales
False killer whales (Pseudorca crassidens) are odontocetes that inhabit tropical
and temperate oceans throughout the world (Sargeant, 1982). They acquired their name
because of their similarity in skull morphology to killer whales (Orcinus orca), although
they are not closely related. False killer whales are a highly social species (Sargeant,
1982) and are known to frequently engage in food sharing (Baird et al., 2008). Attributed
to their highly social behavior, they have also been documented mass stranding, the
largest which included 832 individuals (Ross, 1984). False killer whales are slow to
mature and reproduce, and can live 60 years or more (Ferreira et al., 2014). They
generally feed on a variety of oceanic fish and squid, including large gamefish such as
mahi-mahi, swordfish, and yellowfin tuna (Baird et al., 2008).
False killer whales are one of the odontocete species most negatively affected by
fisheries in Hawaiʻi, and are a species of conservation concern. There are known to be
three distinct populations of false killer whales living in Hawaiian waters; they include

6

the insular Main Hawaiian Island (MHI) population, the Northwestern Hawaiian Islands
(NWHI) insular population, and a pelagic population (Chivers et al., 2007; Baird et al.,
2008). Within these populations, there are estimated to be 151 main Hawaiian Island
individuals (Oleson et al., 2010), 552 NWHI individuals, and 1,552 pelagic individuals
(Bradford et al., 2012). In the longline fishery, individual whales have been documented
depredating, (i.e., taking hooked tuna off of these lines) which has resulted in individuals
becoming hooked during this practice, which can lead to serious injury or death (Forney
& Kobayashi, 2007).
It has been shown through biopsy samples that the MHI insular population is
genetically distinct from false killer whales in other areas (Chivers et. al., 2007; Baird et
al. 2008), and, therefore, their population is assessed as separate from global population
counts of this species. Because of this small population size, the risk of death for this
genetically distinct group of even a few individuals is detrimental to the persistence of
this population and puts the insular population at greater risk of extinction (Carretta et al.,
2014). The MHI population of false killer whales’ mortality and serious injury rates due
to interactions with fisheries exceed the population’s PBR level (Carretta et al, 2014).
The MHI population of false killer whales was listed as federally endangered in 2012,
and therefore continues to be the focus of much research attention due to their ESA
listing, the TRT, and other evidence of fisheries interactions (Baird et al., 2014).
There are three distinct social clusters in the MHI population of false killer whales
(Baird et al., 2012). Satellite tag data suggests that individuals from clusters 1 and 3 have
little overlap with the longline fisheries, but although their ranges overlap with each
other, they appear to have different high-density areas where individuals within a social
7

group frequent (Baird et al., 2010, 2012). While there is no satellite tag data for cluster 2,
according to photographic data they appear most frequently off of Hawaiʻi (Baird et al.,
2012).
The bycatch levels of the pelagic population of false killer whale in the longline
fishery also exceed their PBR level (Baird et al., 2014). In 2010 a Take Reduction Team
(TRT) was established to address take of pelagic false killer whales by the longline
fishery. The TRT is made up of fishery industry representatives, federal agencies,
environmental groups, fishery management councils, and academics (NOAA Fisheries,
2010). They developed a Take Reduction Plan (TRP) to decrease mortality and injury in
this species (75 FR 2853, 2010).

Pygmy Killer Whales
Pygmy killer whales (Feresa attenuata), one of the most poorly studied species of
odontocete, are considered a rare species (McSweeney et al. 2009). A rare species is
defined as one that is infrequently seen, inhabits a small range, or has small numbers of
individuals (Flather and Sieg, 2007). Because of their cryptic nature, little information is
known about their diet, foraging behavior, and preferred prey.
Pygmy killer whales are primarily found in tropical, subtropical, and temperate
waters in oceans around the world (Ross and Leatherwood, 1994). Information from
stranded pygmy killer whales show that they feed on cephalopods (Zerbini and Santos,
1997) and fish, as determined by otoliths found in a stranded animal’s stomach contents
(Leatherwood and Reeves, 1989). Pygmy killer whales are easily mistaken for false killer

8

whales and melon-headed whales, but have characteristic white lips that extend around
the whole mouth (Baird, 2010).
The Hawaiian pygmy killer whale population is found throughout the Hawaiʻi
Exclusive Economic Zone as documented by large vessel surveys, and is estimated to be
less than 1000 individuals (Barlow, 2006). Current population estimates say that there is
a single sock of individuals (Caretta et al., 2014), however recent studies using photo-ID
and satellite-tagging data suggest that there may be a more distinctive island-associated
population (Mcsweeney et al., 2009; Baird et al., 2011). These studies have shown that
pygmy killer whales in Hawaiʻi exhibit high site fidelity, or the extent to which an animal
returns to a certain area (McSweeney et. al., 2009). A study by Baird and authors (2011)
analyzed the satellite movements of two tagged pygmy killer whales off of the coast.
Although the sample size for this study was small, the movements of the whales
demonstrated strong associations with the island of Hawaiʻi, remaining an average of
4.07 and 4.66 km from shore, and stayed primarily on the West and South sides of the
island (Bard et al., 2011). Because of high site fidelity, it is suggested that pygmy killer
whales may be especially vulnerable to anthropogenic impacts such as fisheries
interactions (McSweeney et. al. 2009).
Pygmy killer whales are known to have been taken in several different fisheries
and mortalities have occurred due to bycatch in gillnet fisheries in Sri Lanka, Indonesia,
and the Philippines (Ross & Leatherwood 1994). Although no formal fisheries
interactions of pygmy killer whales have been documented in Hawaiʻi, one dead stranded
individual did have hook marks in its mouth, suggesting fisheries interactions may be
occurring (Schofield 2007). Despite this information, no policy has been put in place to
9

protect this species from the impacts of injury and mortality due to bycatch (McSweeney
et. al. 2009).

Mouthline Injury Assessment
There are no known studies of assessing mouthlines to indicate fisheries
interactions in cetaceans in Hawaiʻi. However, a recent study at the University of North
Carolina at Wilmington provided information that could to help determine whether
mouthline injuries seen in photos are fisheries-related or not (McLellan et al., 2014). The
authors tested the effects of five different hook types used in longline fisheries on three
odontocete species (false killer whale, rough-toothed dolphin, and short-finned pilot
whale) that are known to interact with this fishery. The purpose of this study was to
determine which types of hooks cause the least damage to odontocetes hooked in the
mouthline. McLellan and authors (2014) used fresh dead carcasses of these species,
hooked them in the mouth, and applied pressure consistent with a struggling whale. Their
study found that depending on the type of hook used, the hook either: 1) tore through the
tissue around the lip, creating scarring, 2) tore the lip and broke off, leaving part of the
hook remaining in the lip tissue, or 3) fractured the jaw/mandible. A study by Wells et al.
(2008) assessed survivorship of Florida resident common bottlenose dolphins after being
hooked in the mouth or ingesting fishing gear, and found that gear ingestion likely
eventually lead to mortality. These studies combined with existing extensive false killer
whale research, and available information on pygmy killer whales will provide the
framework for this study.

10

CHAPTER 2 - MOUTHLINE INJURIES AS AN INDICATOR OF FISHERIES
INTERACTIONS IN HAWAIIAN ODONTOCETES

Introduction

Marine mammals, in particular cetaceans, face a variety of anthropogenic threats
at varying scales of impact, including habitat degradation, military sonar testing,
bioaccumulation of persistent organic pollutants, unsustainable hunting practices, ship
strikes due to increased global trade, and climate change (Convention on Migratory
Species, 2008). At a global scale, mortality and injury due to interactions with various
fisheries is likely the most serious conservation concern for cetaceans worldwide (Read,
2006). Odontocetes (toothed whales) may be particularly at risk to fisheries interactions
due to certain life history traits, including feeding behaviors and slow growth and
reproductive rates. Direct interactions between odontocetes and fisheries are of particular
conservation concern for Hawaiian species of odontocetes. A number of odontocete
species have been documented interacting with fisheries in Hawaiʻi, which can result in
injuries due to accidental hookings and entanglement, as well as mortality (Nitta and
Henderson, 1993).
Direct, or operational, interactions with fisheries are described by Beverton
(1985) as instances where ‘marine mammals come into physical contact with fishing
gear’, usually with negative consequences for the animal, as well as damage to the
fishermen’s catch. Types of direct fisheries interactions include depredation, where
animals damage or remove fish from fishing gear (Gilman et al, 2006). Bycatch, or the
taking of non-target species due to entanglement or accidental hookings, is another
11

operational interaction that is detrimental to both odontocetes and fisheries (Hall, 1996).
Direct/operational interactions often result in severe injury and mortality of marine
mammals, as well as financial loss due to gear damage and fish losses (Twiss and
Reeves, 1999).
Although there is sufficient evidence from marine mammal observer programs
that odontocetes sometimes accidentally become hooked on longlines, no study has been
undertaken to assess mouthline injuries as an indicator for fisheries interactions around
the Hawaiian Islands. Baird and Gorgone (2005) looked at fin injuries in false killer
whales as indicators of fisheries interactions in Hawaiʻi, however these injuries were
likely a secondary injury acquired from struggling against a line after being hooked in the
mouth.
There are 18 species of odontocetes documented living in the waters surrounding
the main Hawaiian Islands, of which there are 11 small resident populations (Baird et al.,
2015). Evidence suggests that direct fisheries interactions are most detrimental for small
populations of cetaceans (Read, 2008). For this study, I chose to examine two of these
species, the false killer whale and pygmy killer whale.
False killer whales in Hawaiʻi are documented as having three distinct
populations: two insular populations (one around the main Hawaiian Islands and one
around the Northwestern Hawaiian Islands) and a pelagic or open-ocean population
(Carretta et al., 2014). There are estimated to be 151 main Hawaiian Island individuals
(Oleson et al., 2010), 552 NWHI individuals, and 1,552 pelagic individuals (Bradford et
al., 2012). False killer whales are known to be taken in the Hawaiian longline fishery, and

12

have been documented taking fish off of lines. In 2010 a Take Reduction Team (TRT)
was established to address the incidental take of pelagic false killer whales by the
longline fishery, and a Take Reduction Plan was developed to decrease mortality and
injury in this species (75 FR 2853, 2010). The MHI population of false killer whales’
mortality and serious injury rates due to interactions with fisheries exceed the
population’s Potential Biological Removal (PBR) level (Carretta et al, 2014). Listed as
federally endangered in 2012, the MHI population of false killer whales continues to be a
focus of research due to their ESA listing, the TRT, and other evidence of fisheries
interactions (Baird et al., 2014).
Within the MHI population, there are three distinct social clusters (Baird et al.,
2012). Satellite tag data suggests that individuals from clusters 1 and 3 have infrequent
overlap with the longline fisheries, and while their ranges overlap they appear to have
different high-density areas (Baird et al., 2010, 2012). While information on the
movements of cluster 2 is limited to photo-identification data, they appear most
frequently off of the island of Hawaiʻi (Baird et al., 2012).
Pygmy killer whales are one of the most poorly understood species of odontocete
and are considered rare throughout their range (Pryor, 1965). Because of their natural
rarity and low sighting rate, little is known about their diet, foraging behavior, and
preferred prey. Pygmy killer whales in Hawaii are currently recognized as a single stock
(Carretta et al., 2014), however high resighting rates of individuals off of Oʻahu and
Hawaiʻi suggest small island-associated populations (McSweeney et al., 2009). Because
of high rates of site fidelity, it is suggested that pygmy killer whales may be especially
vulnerable to fisheries interactions (McSweeney et. al. 2009). Although no formal
13

fisheries interactions with pygmy killer whales have been documented in Hawaiʻi, one
dead stranded individual did have hook and line marks around its mouth, suggesting
problematic interactions may be occurring (Schofield 2007).
In Hawaiʻi the commercial longline fishery consists of a shallow-set fishery,
which targets swordfish, and a deep-set fishery targeting tuna. In 2004, 100% observer
coverage on the shallow-set fishery and ~20% coverage on the deep-set fishery was
implemented due to concern over sea turtle bycatch (Forney and Kobayashi, 2007).
However, there are a large number of small-scale commercial fisheries operating around
the main Hawaiian Islands that have no observer coverage, including the troll, handline,
shortline, kaka-line fisheries, as well as the numerous recreational fishermen. These
fisheries account for 3,000 to 3,200 (over 80%) of the Commercial Marine Licenses
(CML) issued in Hawaiʻi from 2010 to 2013 (Baird et al., 2014).
There are no known studies that use mouthline injuries to assess fisheries
interactions in false killer whales, pygmy killer whales, or any cetaceans in the main
Hawaiian Islands. However there are a number of studies from other areas that assess
other aspects of mouthline injuries. A study by Wells et al. (2008) assessed survivorship
of Florida resident common bottlenose dolphins after being hooked in the mouthline or
ingesting fishing gear, and found that ingestion of gear had a high probability of
eventually lead to mortality. Another study by McLellan et al. (2014) tested how
commercial longline hooks behave when hooked in the mouths of dead odontocete
specimens.

14

The current research attention on fisheries interactions in Hawaiʻi has prompted
research attempting to quantify fisheries-related injuries due to direct interactions. Baird
et al. (2014) evaluated Hawaiian false killer whale fin injury rates, and found differences
in injury rates between populations and social clusters. This analysis prompted a study of
mouthline injuries visible on the gape as a method of assessing direct injuries that occur
from being hooked in the mouth, rather than secondary fin injuries that occur when
whales struggle against a line while hooked. False killer whales are a species of
conservation concern due to high interaction rates with fisheries, and a small islandassociated resident population of Pygmy killer whales exhibits site fidelity and may be
more susceptible to interactions with fisheries. Therefore these species were prioritized
for mouthline injury assessment in this study.

Methods
Field Methods and Data Collection
Study Area
This research is based on data that was collected from 2000 to 2015 around the
main Hawaiian Islands (MHI) as part of a long-term, multi-species, odontocete study by
researchers from Cascadia Research Collective (CRC). The study area consists of the
main Hawaiian islands, with <45% of effort concentrated in depths under 1,000m (Figure
1). The majority of photos used for this study were taken on CRC surveys from January
2000 to January 2015, in addition to volunteer photo submissions from 1986 to 2015.

15

Field methods for CRC surveys are outlined in Baird et al (2013), where small-vessel
were primarily used for surveys.
Volunteer data: Opportunistic effort
A number of volunteers and partners submit photos of priority species to CRC to
be added to each odontocete species catalog. Tour boat operators spend large amounts of
time on the water and have many opportunistic odontocete sightings. Because of these
established partnerships, Cascadia has been able to increase its photo database to include
opportunistic odontocete encounters from throughout the year, in addition to CRC field
projects. Some of these opportunistic encounters have included underwater photos, which
often allow for the mouthline to be captured in an image, but tend to have lower photo
quality when zoomed in.
Photographic Effort
All Cascadia photos taken after 2002 during directed efforts were taken with
digital SLR cameras, using zoom lenses, while photos taken prior to 2003 were taken
using film cameras. Directed research trips had anywhere from two to four photographers
taking photos during each sighting. Effort was made to photograph the head/mouthline of
all individuals encountered. Photos available from National Marine Fisheries (NMFS)
from offshore surveys were also used. This is the same data set used in the Baird et al.
(2014) fin injury study.
In directed field efforts, attempts are made to photograph both the right and left
side of the dorsal, and subsequently both sides of each mouthline. Obtaining photos of
mouthlines depended on several factors, including how high animals lifted their heads out
16

of the water, reaction time by each photographer (as the head first emerges from the
water), and water obscuring portions of the mouthline.

Photo-identification
Mouthline Assessment Protocol
Photos from all encounters in the CRC catalog were reviewed for each species for
a mouthline assessment archive. I evaluated all photos from every CRC encounter from
2000 to 2015, and all volunteer photo submissions for each species. These photos were
selected from the historical species catalog, where photos are grouped by individual, and
then by each encounter where that individual was known to be present. I went through
each folder for every known individual, using the photo processing software ACDSee.
Each photo where a mouthline was visible was copied, labeled into a folder, and
eventually scored for injury.
Each photo was analyzed visually, and if any portion of the mouthline was visible
in the photo, it was added to the species’ mouthline archive under a folder with the date
and encounter that it was taken, using the specific file naming template
YEARMONTHDAY_ENC#_ID#_mouthline
(e.g.,2014JUL24_ENC1_HIPc144_mouthline). If the photo containing the mouthline
injury came from an opportunistic encounter, the naming template included the
contributor’s name (e.g., 2015SEPT03_DeronVerbeck_HIFa313_mouthline). Each
individual’s folder was then entered into a Microsoft excel sheet, where date,
encounter/source, area, island, and number of photos were entered, as well as which side
17

of the mouthline was visible for this individual (Left, Right, Both, Front, Upper or
Lower).

Mouthline scoring
After all photos from each species’ archive were processed, mouthlines were then
assessed and scored based off and adapted from a protocol developed by Baird and
Gorgone (2005) for assessing fin injuries. Scoring of the mouthlines of each individual
varied by species, but the same basic principles apply.
Each encounter where an individual was seen was scored separately by looking at
the folder originally created under each encounter where an odontocete’s mouthline was
seen. First, I visually assessed the portion of the mouthline which was visible. The
percentage of mouthline visible was also estimated and recorded in 5% increments.
Finally, photo quality was scored numerically on a scale of 1 to 4 (1=poor, 2=fair,
3=good, 4=excellent).
For all species, number of notches in each side of the mouthline was recorded.
Notches were identified visually as being a small cut or chunk taken out of the mouthline
(Figure 2). Also recorded for all species was the degree of scarring in the corner of each
mouthline (1=light, 2=moderate, 3=heavy) (Figure 2). When barnacles were growing on
the mouthline it was classified as an injury because barnacles must adhere to a hard
surface, therefore there must have been a breakage in the skin that exposed the tooth for
the barnacles to adhere (Figure 2). Any evidence of fisheries interactions, or anything
else unusual was noted and described qualitatively in an extra comments section. Injuries
18

recorded were then assessed on the likelihood of being the result of an interaction with
fisheries.
Certain species of odontocetes are known to re-pigment after injury or trauma.
However, pygmy killer whale lips become naturally whiter with age, therefore in this
species it cannot be assumed that if there is pigmentation, there is also injury. Because of
this, pygmy killer whales in this study were assessed for injury based on irregular
pigmentation and scarring around the mouthline. For pygmy killer whale mouthline
assessments, an extra section was added for degree of natural pigmentation (on right and
left sides of head), described numerically (0=no pigmentation, 1=slight pigmentation, 2=
some/moderate pigmentation, 3=heavy pigmentation), and if irregular pigmentation
occurred it was described in the comments. For false killer whales, any unusual
pigmentation around the mouthline or elsewhere was described in the “other” or
comments sections, and depending on the severity, was or was not determined an injury.

Mouthline injury assessment
After combining all mouthline photos for each individual, each individual’s
mouthline was scored. The individuals with any possibility of an injury (e.g., score > 0 in
any category) were further assessed for an injury consistent with fisheries interactions.
Photos were reassessed and divided into one of four categories- not consistent (with
fisheries interaction), possibly consistent, consistent, and undeterminable. To be
considered an injury consistent with fisheries interactions an individual must have a notch
with broken skin or irregularity in the mouthline, any breakage in the lip where teeth

19

were visible, any type of growth on the mouthline (which indicates a skin breakage),
severe scarring in the corners of the mouthline, and/or irregular pigmentation (Figure 2).
Pigmentation injury qualification differed by species- where moderate to heavy
pigmentation on the lip was considered an injury consistent with fisheries interaction for
false killer whales, but only irregular pigmentation was considered an injury in pygmy
killer whales.
Individuals that received the classification of “no injury” included light scraping
or scarring which could not confirmed as being consistent with fisheries interactions.
Also in the “no injury” classification was anything that could be consistent with injuries
from a prey species such as spines on a fish. The “possible injury” category was given to
photos of individuals with that injuries that might be consistent with fisheries
interactions, but either the injury was not large enough, the photo was not clear enough to
determine, or part of the injury was obscured by water around the mouthline.
Undeterminable injuries were qualified by poor photo quality or mouthlines that were
obscured by water.

Analysis
For consistency and accuracy, minimum standards for photo quality and
mouthline visibility were used in the final analysis. Individuals who only had photos of
their mouthline rated as a quality of 1 (poor) were eliminated from the analysis because
an accurate determination of injury could not be verified due to the photos being too dark,
too blurry, or too grainy when zoomed in (this was the case for many underwater photos).
20

I also only used individuals who had ≥50% of their mouthline visible in all of their
photos combined, to decrease the amount of negative injury bias in the results. Calves
and juveniles were also eliminated from the analysis, since they would be less likely to
have sustained fisheries related injuries both due to their diet consisting mostly of milk
for the first year or more of their life, and due to a limited time period for potentially
interacting with fisheries (Oftedal, 1997).
After the mouthline scoring, some individuals were labeled as having “possible
injuries”, due to the injury being too small to determine, part of the possible injury being
obscured by water, or photo quality being too low. I did not include these animals in the
analysis because of the ambiguity of whether or not they have an injury. Therefore, all
animals used in the analysis were adults and subadults, with photo quality rated 2 to 4,
who either were scored to have an injury or not have an injury, based on looking at ≥50%
of their mouthline.
To evaluate the differences in fisheries-related mouthline scarring between
species, populations, and social clusters, a Fisher’s exact test was used. Data was
available on the sex for 15 of the false killer whales with injuries, either through genetic
analysis of biopsy samples (Chivers et al., 2010) or observational data on the presence of
calves and neonates, and so I assessed sex bias in individuals with injuries. To determine
if injury detection increases as the percentage of mouthline visible increases, I used
Fisher’s exact test. For this test, individuals with mouthlines visible were binned into two
categories- those having 50%-75% of their mouthline visible, and those having 76%100% of their mouthline visible.

21

Results
After sorting through over 167,000 photos, 290 individuals were found to have at
least some portion of the mouthline visible. The remaining individuals were not included
for the remainder of the study. After sorting these minimum photo quality, mouthline
visibility, and age classs parameters, 99 individual false killer whales and 47 individual
pygmy killer whales were used for analysis, making a total of 146 individuals.

False Killer Whales
For false killer whales, a total of 195 individuals had at least some portion of the
mouthline visible, 144 had ≥50% of their mouthline visible and 45 had a full 100% of
their mouthline visible. When constraining the data to the photo quality and % mouthline
visibility determined in the methods, there were a total of 142 individuals with at least
some portion of the mouthline visible, and 99 individuals with ≥50% of their mouthline
visible (mean proportion of mouthline visible=58%). The MHI population of false killer
whales had the greatest amount of individuals with mouthlines visible, accounting for 91
of the 142 individuals with mouthlines visible, which is more individuals than the pelagic
and NWHI populations combined (Table 1).
No significant difference in injury rates for false killer whales between
populations was detected (Fisher’s exact test, p=0.47). The highest percentage of injuries
occurred in the Main Hawaiian Islands population, with 22.2% of all individuals with
≥50% mouthline visibility having injuries (Table 2). When assessing only individuals
who have 100% of the mouthline visible, injury rate increases to 30%. Although sample
22

sizes for the pelagic and NWHI populations were notably small, 7% and 15% of the
pelagic and NWHI, respectively, had injuries. Of all false killer whales with mouthlines
visible, 19% had injuries (Table 2).
There was no significant difference in fisheries related mouthline injuries between
the three MHI false killer whale social clusters (Fisher’s exact test, p=0.39). The number
of total mouthline photos was highest for cluster 1, with cluster 2 and 3 being relatively
similar in number. Rates of injury were highest in cluster 2, with 31.8% of the population
with ≥50% mouthlines visible having injuries. Injury rates were second-highest in cluster
1, where 20% of the individuals having injuries. Injury rates for cluster 3 were lower than
cluster 1 and 2 (Table 3).
Of the animals that have injuries consistent with fisheries interactions, more
females have injuries than males, although this difference was not statistically significant
(Sign test p = 0.1185). Of the 19 individuals meeting the mouthline quality and visibility
standards for this study, 11 were females and four were males (Figure 3). Four animals
of unknown sex have either not been biopsied, or have no defining characteristics that
would deem them either sex.

Pygmy Killer Whales
For pygmy killer whales, a total of 95 individuals had at least some portion of
their mouthline visible, 66 had ≥50% of their mouthlines visible, and 15 had 100% of
their mouthline visible. As percentage of mouthine visible increases, rate of injury also
23

increases in both the “positive” and “possible” injury categories. Forty-seven individuals
had ≥50% of their mouthline visibility and met the photo quality criteria. Of these, 34%
had injuries consistent with fisheries interactions (Table 4).
When removing the individuals from Maui, individuals from Oʻahu and Hawaiʻi,
31% had injuries consistent with fisheries interactions (Table 5). Although mouthline
injury rates differed between Hawaiʻi and Oʻahu associated individuals, there was not a
significant difference between the two groups (Fisher’s exact test, p=0.11).

Mouthline assessment evaluation
When both species are combined, the probability of individuals having injuries
consistent with fisheries interactions was significantly higher when a higher proportion of
the mouthline is visible (Fisher’s exact test, p<0.0361; Figure 4).

Discussion
Although there are relatively few studies addressing mouthline injuries in
odontocetes, this research demonstrates that mouthline injury analysis is an effective way
to assess fisheries interactions in false killer whales and pygmy killer whales. By
assessing the various factors that could contribute to a mouthline injury, we can better
understand how injuries could be acquired. Other than fisheries interactions, a possible
cause of injury to an odontocete mouthline could be injuries from prey species, for
example the spines of a fish raking across the mouthline during a struggle. However, I
24

assume that if negative prey interactions were the cause of these injuries, they would
leave scars similar to the morphological features of that prey species (e.g. spine rake
marks, circular suction cup wounds, etc.).
Another way that an individual could acquire an injury would be through an
attack from a predator, such as a shark, however it would be highly unusual for these
wounds to appear in a single specific location such as the mouthline, as scarring would be
seen on the dorsal fin and body. Although there is no way to be completely certain that
injuries are acquired through fisheries interactions (unless observed occurring), all
injuries in this study are considered to be consistent with fisheries interactions based on
the information available.
Scarring patterns for mouthline injuries in this study do not seem to be consistent
with injuries from prey. The deep notches in the lip, large chunks taken out of lip tissue,
jagged scarring in the corners of mouthlines, irregular pigmentation patterns, and growths
adhering to teeth due to lip tissue breakages are all consistent with an animal being
hooked in the mouth and struggling against a line, with the line causing the injuries on
the gape. This is supported by a study by McLellan et al., (2014), where a variety of
hooks were tested on the mouthlines of dead odontocetes to simulate that animal
struggling against a line after being hooked. The hooks either tore or sliced through the
lip tissue, and published photos are consistent with injuries we came across in this study.
Therefore, we consider the scarring patterns and injuries seen in this study as being
consistent with fisheries interactions.

25

False killer whales
Consistent with previous research (Baird et al., 2014) results show that of all
Hawaiʻi populations, the MHI insular population of false killer whales have the highest
rates of mouthline injury (22% of individuals assessed having injuries), supporting that
individuals from this population regularly interact with fisheries. These results are
congruent with fin injury analysis (Baird et al., 2014), where the MHI population showed
injury rates five times higher than the pelagic and NWHI populations. Despite small
sample sizes from the pelagic and NWHI populations of false killer whales, mouthline
injuries were still seen in individuals.
Mouthline injuries seen in false killer whales in this study varied widely in
severity and frequency, with the most commonly seen injury being large notches in the
lip tissue (Figure 5). Two individuals had lip injuries so extensive that lip tissue was
completely missing and teeth were visible (Individual B, Figure 5). Other injuries
included irregular pigmentation around the head and lip (Figure 6).
Since only large injuries were considered for this study, it is unlikely that they
could be the result of interaction with prey or normal ‘wear and tear’ on the mouthline.
Although false killer whale prey include large pelagic fish and could conceivably cause
damage on the mouthline, most injuries are more consistent with a localized severe
wound rather than a struggling fish which would presumably cause injury all along the
mouthline or head, rather than precise clefts of missing lip tissue more consistent with a
pulling hook or line.

26

Although not significant, cluster 2 individuals had the highest rate of injury, with
31% having injuries consistent with fisheries interactions. This information is not
consistent with previous research on cluster and fin injury analysis, where cluster 3
showed the highest rates of interaction (Baird et al., 2014). However that study differed
in methodology since all members of cluster 3 were assessed, rather than a subset. Since
there are differences in injury rates for these clusters, it does suggest that different social
clusters may have different habits when it comes to depredation and fisheries
interactions. This information validates further research in this area, as certain behaviors
could be culturally taught and passed down within a social cluster, which could impact
population growth within that cluster (Sargeant and Mann, 2009).
False killer whales are the most frequently recorded cetacean hooked in the
Hawaiian longline fishery. The majority of false killer whales (83% of 24 individuals
reported hooked in the tuna longline fishery between 2007 and 2011) had injuries that
were either fatal or serious enough to cause death (Bradford and Forney, 2014). Since the
overwhelming majority of false killer whales hooked in the longline fishery likely die, it
is conceivable that we would never see most of these injuries. This information coupled
with our research of high mouthline injury rates suggests that it is possible that false
killer whales are interacting at high rates with other nearshore fisheries. Further
substantiating this suggestion is the false killer whale that stranded in 2013 with 5 hooks
in its stomach, 3 of which were not from the longline fishery (Baird et al., 2014). Since
nearshore fisheries in Hawaiʻi lack observer coverage, which fishery they may be coming
into contact with most often is unknown.

27

Consistent with recent fin injury analysis (Baird et al., 2014), results showed a sex
bias toward females having the most injuries consistent with fisheries interactions, with
11 out of 15 individuals of known sex with injuries being female (73.3%). Of the
remaining 8 individuals, 4 were males and for 4 the sex was unknown. Although these
results were not significant (likely due to a small sample size), a disproportionate rate of
females interacting with fisheries could have implications for population growth in this
species.

Pygmy killer whales
The limited information known about pygmy killer whales prey species makes it
difficult to determine if mouthline injuries could be occurring in pygmy killer whales due
to prey interactions. However, based on the descriptions of the mouhtline injuries
evaluated in this study and what is known about pygmy killer whale diets in other parts of
the world, we can assess this question. Pygmy killer whales in other areas have been
documented feeding on fish and cephalopods (Leatherwood and Reeves, 1994; Zerbini
and Santos, 1997). Injuries assessed in this study were unlikely to be from cephalopods,
because those injuries would mimic the roundness of a suction cup. While it is possible
that injuries could be occurring during feeding events with other prey items, the unusual
nature of the injuries seen in this study suggests that they are more likely to be consistent
with fisheries interactions.
The most common injuries seen in pygmy killer whales were large notches taken
out of the mouthline, irregular pigmentation, and corner of the mouth scarring. One
28

individual had large barnacle growths resulting from a breakage in the lip tissue.
Pigmentation often occurred irregularly in corners of the mouthline and in jagged,
vertical cuts going up, down, or through the lip (Figure 7). Notches (Figure 8) were
commonly seen either by themselves or in conjunction with additional pigmentation
surrounding the trauma sight. This is not surprising considering that pygmy killer whale
scars heal white.
The results which demonstrate a high injury rate of 43% for Hawaiʻi associated
individuals compared to 20% of Oʻahu individuals (Table 5), combined with the
knowledge of a Hawaiʻi island associated population of this species (McSweeney et al.,
2009) suggest that this population is interacting with nearshore fisheries.
Pygmy killer whales are considered data deficient under the International Union
for the Conservation of Nature (IUCN) and are naturally rare throughout their range,
therefore the high rates of injuries consistent with fisheries interactions shown in this
study could have implications for this species. Island associated populations of pygmy
killer whales have a high degree of site fidelity, and the west coast of Hawaiʻi has been
identified as a Biologically Important Area for this population (McSweeney et al., 2009;
Baird et al. 2015). Having a high degree of site fidelity can increase a populations’
susceptibility to anthropogenic impacts since they have evolved to live and feed in
relatively small specific areas. This information coupled with an injury rate of 31% for
Hawaiʻi and Oʻahu individuals from this study suggests that individuals in these
populations are coming in contact with fisheries. The only observer-covered fishery in
Hawaiʻi is the deep-set and shallow-set longline fishery, and there have been no
confirmed reports of pygmy killer whales interacting with these fisheries prior to 2014
29

(Carretta et al., 2014). This suggests that pygmy killer whales are mistakenly reported as
a species similar in appearance or the mouthline injuries in pygmy killer whales could be
coming from unregulated nearshore fisheries.
Since pygmy killer whales primarily feed at night and there are few anecdotal
reports of them depredating lines, this mouthline injury assessment could provide new
insights into fisheries interactions for this species. Although sample sizes were relatively
low, this research suggests that pygmy killer whales could be interacting with the
fisheries at higher rates than previously thought.
This could have potential policy implications since there are no strong
management directives in place for pygmy killer whales in Hawaiʻi. Information about
fisheries interactions could be an indication that more research should be directed at these
species, especially because of their cryptic nature and how little is known about them in
general. Since we have limited information on their feeding behaviors and prey species,
we have little idea about with what fisheries they could potentially be interacting. Further
research in this area could lead to information about the diet and feeding behavior of
pygmy killer whales in Hawaiʻi in addition to their degree of interaction with fisheries.

Mouthline assessment analysis
When considering these results, it is important to mention that interaction rates
are negatively biased, because individuals scored as having “no” mouthline injury may
have less than 100% of the mouthline visible, for example, individuals who have the left
50% of their mouthline visible may have an injury on the right side. The significant p30

value in the Fisher’s exact test demonstrates that with increased mouthline visibility,
more injuries are detected. All of this information suggests that all of the results found in
this study are most likely a conservative estimate of actual injury rates.

Conclusion
The high rates of mouthline injuries described in this study suggest that certain
changes should be considered for the management and conservation of these species.
Evidence that the MHI false killer whale population has high rates of mouthline injury
should be considered in future policy concerning this endangered species. Supported by
fin injury analysis (Baird et al., 2014) and the 2013 stranding of the false killer whale
from cluster 3 with three unidentified hooks in the stomach, this study furthers the need
to expand the Take Reduction Plan to include nearshore fisheries. Further effort is also
necessary to determine rates of fisheries interactions in the MHI social clusters.
Obtaining more mouthline photos for all clusters would allow for a more accurate
analysis of direct fisheries interactions. Further research of sex bias should be conducted
to help understand potential for population growth in this species, and could also help
understand more about behavioral feeding characteristics.
Pygmy killer whale injury results from this study indicate that there may also be a
cause for concern that this species, as mouthline injury rates suggest that individuals are
interacting with fisheries more than previously thought. Because pygmy killer whales are
naturally rare, a population decrease may not be easily detected. Although difficult to
study because of low encounter rates in the field, further research must be conducted to
31

learn more about how pygmy killer whales interact with fisheries. One way to bolster our
knowledge and obtain more photographic data on this species is to continue outreach
among the local fishing and boating community. Increasing the data set is one important
was to increase our understanding about this cryptic species. Having greater evidence of
fisheries interactions for this species, coupled with more satellite tag data could help
determine whether we should consider additional protections for this rare species.

Mouthline assessment research
Mouthline injury assessment is a relatively low-cost and affordable way to assess
fisheries interactions. Other than being time-consuming, there are few drawbacks to
consider. Mouthline injury assessment can be applied to an existing photo data set, and
can reveal new information without having to specifically collect more photos. The
effectiveness of mouthline assessment could be improved by intentional directed efforts
by field photographers to capture mouthline and head photos.

Future research
Mouthline injury assessment can be a useful tool in determining fisheries interaction
rates. In conjunction with analyzing strandings for evidence of hookings or hook
ingestion, mouthline injury assessment can be provide further insight into fisheries
interactions in populations within species as well as social clusters. Continuing mouthline
assessment in a multi-species comparison for short finned pilot whales, rough toothed

32

dolphins and melon headed whales, could yield valuable information about differences in
species interaction rates. In addition, adding in “unknown individuals” to the false killer
whale and pygmy killer whale mouthline assessment could increase the scope of the
analysis. In order to understand more about mouthline injuries and depredation behavior,
assessments of where injuries occur on the mouthline could be undertaken.

33

Figures

Figure 1. Tracklines showing total effort for CRC survey in Hawaiʻi from 2000-2012
from Baird et al. (2013).

A

B

C

D

B

Figure 2. Examples of injuries consistent with fisheries interactions. False killer whales
with notch (A) and breakage in lip tissue exposing teeth (B). Pygmy killer whale
individuals with irregular pigmentation and notch (C) and growth accompanied by corner
mouth scarring (D)
34

Unknown, 4

Male, 4

Female, 11

Figure 3. Sex of false killer whales with injuries consistent with fisheries interactions

Figure 4. Contingency table demonstrating that probability of injury is greater when
mouthline visibility is 76-100% than 50-75%

35

Figure 5. Examples of injuries on the mouthlines of false killer whales considered consistent with
fisheries interactions. (A) HIPc210, male from cluster 1, has one large notch on the left side. This
is the most commonly seen injury. (B) HIPc339, a female from cluster 2, has a large chunk taken
out of the lip where the teeth are visible, placed closer to the front of the rostrum. (C) Although
underwater photo quality can be low, it is still clear that this individual, HIPc222, a female from
cluster 2, has two large notches in the mouthline. (D) HIPc161, an adult male from cluster 3, has
a prominent notch placed mid-lip on the left side.

Figure 6. Examples of pigmentation in false killer whales, injuries considered to be consistent
with fisheries interactions: (A) HIPc 104, an individual from cluster, 1 has pigmentation
surrounding a notch in the lip; (B) HIPc230, a female from cluster 2, has pigmentation on the
lower lip, towards the front of the rostrum.

36

A

B

C

D

Figure 7. Examples of irregular pigmentation consistent with fisheries interactions. A, B, and C
have irregular pigmentation in the corner or the mouthline. D has irregular vertical scarring going
through the mouthline plus notable indentations, possibly consistent with being hooked one the
mouthline

Figure 8. Examples of mouthline notches consistent with fisheries interactions: A and B have
large notches in the lip. C has multiple large barnacles growing due to breakages in lip tissue. D
has small equidistant nicks on the tip of rostrum, possibly created by a line.

37

Tables

Table 1. False killer whale mouthline visibility by population

Population

MHI

Pelagic

NWHI

All

Mouthline Visibility
Total

91

≥50%

72

100%

23

Total

33

≥50%

14

100%

1

Total

18

≥50%

13

100%

1

Total

142

≥50%

99

100%

24

38

Table 2. Count and percentage of false killer whales with mouthline injuries consistent
with fisheries interactions by population, for photos taken 2000-2015

Population

Injuries consistent with fisheries
interactions

Mouthline
Visibility

Count

Percentage

≥50%

72

16

22.2%

100%

23

7

30.4%

≥50%

14

1

7.1%

100%

1

0

0.0%

≥50%

13

2

15.4%

100%

1

0

0.0%

≥50%

99

19

19.2%

100%

24

7

29.2%

MHI

Pelagic

NWHI

All

Table 3. Count and percentage of mouthline injuries consistent with fisheries interactions
by MHI social cluster of false killer whale

Cluster

Injuries consistent with fisheries
interactions

Mouthline
Visibility

Count

Percentage

1

≥50%

30

6

20.0%

2

≥50%

22

7

31.8%

3

≥50%

20

3

15.0%

39

Table 4. Count and percentage of mouthline injuries consistent with fisheries interactions
in pygmy killer whales by mouthline visibility

Injuries consistent with fisheries
interactions

Mouthline
Visibility

Count

Percentage

Pygmy Killer

Total

95

17

17.9%

Whales

>50%

68

16

23.5%

100%

15

8

53.3%

Table 5. Count and percentage of mouthline injuries consistent with fisheries interactions
in pygmy killer whales by mouthline visibility in Hawaiʻi and Oʻahu associated
individuals

Pygmy Killer
whales
Hawaiʻi
Oʻahu

Mouthline Visibility
≥50%
≥50%

23
20

Injuries consistent with
fisheries interactions
Count
10
4

Percentage
43.5%
20.0%

40

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Appendix
Photo credits
Figure 2- (A) Deron Verbeck, (B) Jessica Aschettino (C) Tori Cullins (D) Russ Andrews
Figure 5- (A) Elisa A Weiss (B) Elisa A Weiss (C) Deron Verbeck (D) Russ Andrews
Figure 6- (A) Cascadia Research Collective (B) Elisa A Weiss
Figure 7- (A) Jim Ward (B) Robin W Baird (C) Tom Elliot (D) Robin W Baird
Figure 8- (A) Cascadia Research Collective (B)/(C) Russ Andrews (D) Robin W. Baird

47

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