2014 MARINE DEBRIS ENTANGLEMENT REPORT 

Entanglement

Entanglement of Marine Species in 

Marine Debris with an Emphasis on 

Species in the United States

2014 NOAA Marine Debris Program Report 

© HIHWNMS (NOAA MMHSRP, permit #932-1489 2/7/2007
April 2014

National Oceanic and Atmospheric Administration

National Ocean Service

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NOAA Marine Debris Program

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For citation purposes, please use: 

National Oceanic and Atmospheric Administration Marine Debris Program. 2014 Report on the Entanglement of Marine Species in Marine Debris with an Emphasis 

on Species in the United States. Silver Spring, MD. 28 pp

For more information, please contact: 

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Acknowledgements

The National Oceanic and Atmospheric Administration (NOAA) Marine Debris Program would like to acknowledge Wayne McFee for conducting this research, 

and Jason Paul Landrum and Courtney Arthur for providing guidance and support throughout this process. Special thanks go to Jeff Hyland (National Centers for 

Coastal Ocean Science – Center for Coastal Environmental Health and Biomolecular Research) and David Laist (Marine Mammal Commission) for reviewing this 

paper and providing helpful comments. An additional thank you goes to John Hayes (NOAA National Ocean Service, National Centers for Coastal Ocean Science) 

for a copy/edit review of this report and Asma Mahdi for design and layout. Funding for this project was provided by the NOAA Marine Debris Program.

This publication does not constitute an endorsement of any commercial product or intend to be an opinion beyond scientific or other results obtained by the 

National Oceanic and Atmospheric Administration. No reference shall be made to NOAA, or this publication furnished by NOAA, to any advertising or sales 

promotion which would indicate or imply that NOAA recommends or endorses any proprietary product mentioned herein, or which has as its purpose an interest 

to cause the advertised product to be used or purchased because of this publication.
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

Executive Summary 1

Background 2

Synthesis of Literature 

Pinnipeds 3

Northern Fur Seal 5

Hawaiian Monk Seal 6

Cetaceans 8

Humpback Whale 9

North Atlantic Right Whale 10

Bottlenose Dolphin 11

Other Marine Mammals 12

Sea Birds 13

Sea Turtles 14

Other Marine Species 15

Conclusions 16

Cited References 19

Appendix 25

TABLE OF CONTENTS
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

Entanglement of marine species in marine debris is a global 

problem affecting at least 200 species. Based on the literature 

reviewed in the United States alone, at least 115 species of 

marine mammals, sea turtles, sea birds, fish, and invertebrates are 

affected. This review of the literature focused primarily on marine 

debris entanglement specific to the U.S., incorporating over 170 

reports dating as far back as 1928. Most reports of entanglement 

in marine debris involved pinnipeds, particularly northern fur 

seals (Callorhinus ursinus) and Hawaiian monk seals (Monachus 

schauinslandi), as well as sea turtles. Inconsistencies in defining 

and distinguishing marine debris from actively fished gear 

significantly limits assessments of marine debris entanglement 

rates. Further, marine species databases rarely list marine debris 

data as a separate field, they are not easily searchable and 

would be more effective if centralized into one database. While 

entanglement in marine debris is a source of morbidity and 

mortality for individuals of many species, the impacts of greatest 

concern are those that affect whole populations of organisms, 

particularly small populations that are threatened or endangered. 

For at least some endangered species, such as Hawaiian monk 

seals, available data suggest that entanglement in marine debris 

can produce significant adverse effects at the population level, 

and can contribute to declines in the total numbers of these 

already endangered animals. For other species, with seemingly 

large populations or those populations that are difficult to count, 

population-level effects are more uncertain. However, despite the 

difficulties in detecting population-level effects, marine debris 

clearly poses a threat to animal welfare for those individuals that 

become entangled. Future work should: 1) collect information 

on the various sources (e.g., ocean-based v. land-based debris) 

and types (e.g., fishing gear (active v. derelict) v. boating gear) 

of marine debris that negatively affect organisms, especially 

those animals that are critically endangered, 2) assess the relative 

impacts of marine debris amid other potential factors stressing 

these organisms/populations, such as changing weather patterns 

linked to climate change, climatological events (e.g., El Niño/La 

Niña Southern Oscillation), losses in food availability, and disease, 

and 3) accurately assess the proximate mechanisms driving the 

observed spatial and temporal patterns of entanglement of 

organisms in marine debris, such as existing overlap in animal 

active habitat with areas of higher debris concentrations (i.e., 

oceanic convergence zones), and increases in the relative 

contribution of land-based and ocean-based debris with growing 

human population and activity along coastlines. These patterns are 

not well established and require further attention. Understanding 

the sources and types of marine debris that affects organisms as 

well as the patterns of impact in a natural setting will be crucial to 

guide appropriate mitigation policies and practices. 

Some of the major findings from this review of the literature 

include:

44 sea bird species, 9 cetacean species, 11 pinniped species, 

31 invertebrate species/taxa, 6 sea turtle species reported 

entangled in marine debris in the United States.

Entanglement rates varied across different species/taxa, but 

rates seemed to be greater in areas of overlap between high 

population densities and either human fishing intensity or 

areas of high debris accumulation (e.g., convergence zones). 

Often, the source of fishing gear remnants or other marine 

debris is unknown.

Some of the highest known marine debris entanglement 

rates occur with Hawaiian monk seals (0.7% as of 2004) 

where population numbers are taken into consideration.

For several species of marine mammals, juveniles and 

sub-adults have been found to be more susceptible to 

becoming entangled in debris when compared to more 

agile, developed adults.

Overall, the reported entanglement rates of certain species 

should be used with caution since these rates can be 

biased based on the sampling method and the difficulty 

in distinguishing between actively fished gear and marine 

debris.

Thus, there is a real need for records of wildlife 

entanglement to distinguish between entanglements in 

marine debris as opposed to entanglements in actively 

fished gear.

In certain regions in the U.S. and likely elsewhere in 

the world, numerous species are underrepresented in 

the literature, implying that reported marine debris 

entanglement rates are inherently conservative.

EXECUTIVE SUMMARY

Please report stranded or entangled marine mammals and sea turtles by calling the stranding network member for 

your area (U.S. only). Hotline numbers are listed online at http://www.nmfs.noaa.gov/pr/health/stranding.htm.
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

Marine debris entanglement is a global 

problem that affects a large number of marine 

species. Most research articles documenting 

the entanglement of marine species in the 

United States are limited to certain geographic 

areas and species. Prior to the 1950s much of 

the fishing gear and land-based disposables 

were made of biodegradeable products such 

as hemp rope or paper bags (Laist et al. 1999; 

Gregory 2009). These products broke down 

quickly in the marine environment. As plastic 

and synthetic materials became more popular 

for fishing activities and land-based use, lost 

or abandoned fishing gear and non-disposable 

items made of synthetic material became 

entanglement threats for many marine species, 

including marine mammals, sea birds, sea 

turtles, fish, crustaceans, and even corals.

Entanglement can cause decreased 

swimming ability, disruption in feeding, 

life-threatening injuries, and death. Laist 

(1997) provided a global review of marine 

debris entanglements and found entanglement 

records for 136 marine species worldwide, 

including 86% (6 of 7) of all sea turtle species, 

16% (51 of 312) of all seabird species, and 28% 

(32 of 115) of all marine mammal species. 

Additional species have been identified 

since that review. For example, Baulch and 

Perry (2012) identified 15 cetacean species 

with entanglement records compared to 

11 identified by Laist (1997). This review 

documents 111 species in U.S. waters alone. 

From the literature reviewed, Alaska and 

northwest Pacific region, California, Hawaii, 

Florida, and the northeast Atlantic region all 

contained common reports on entanglement 

of marine species in debris. Species such as 

the northern fur seal (Callorhinus ursinus) 

inhabit waters where marine debris may be 

more concentrated and thus increase the 

potential entanglement rate of these animals 

in marine debris. Examples are the Subtropical 

Convergence Zone north of Hawaii in the 

North Pacific Subtropical Gyre (Howell et 

al. 2012), which is crossed twice each year 

by migrating humpback whales (Megaptera 

novaengliae) and includes the pelagic range of 

juvenile fur seals, and the Northwest Hawaiian 

Islands, where drifting debris accumulates on 

coral reefs inhabited by Hawaiian monk seals 

(Monachus schauinslandi). 

While land-based pollution is considered 

to be a significant source of marine debris, 

the discard and loss of synthetic material 

and plastics by the maritime industry is also 

a significant concern. To address the latter 

concern, the International Convention for the 

Prevention of Pollution from Ships (formally 

adopted in 1973 and updated in 1978 as 

MARPOL 73/78), Annex V to MARPOL 

was adopted in 1985 and entered into force 

in 1988 to reduce waste disposal from ships 

and prohibit the dumping of plastics into 

the ocean (Henderson 2001). The overall 

effectiveness of Annex V is debatable, as 

marine species continue to become entangled 

in marine debris. Initially, potential impacts 

on northern fur seal populations brought 

the problem to the forefront of international 

discourse. During the early 1980s, the 

scientific community was concerned over 

the precipitous decline in the northern fur 

seal population in the Pacific. Entanglement 

in derelict fishing gear was considered a 

major factor in their decline (Fowler 1985) 

and numerous papers were presented at the 

Workshop on the Fate and Impact of Marine 

Debris (Shomura and Yoshida 1985). After 

Annex V, entanglement of fur seals declined 

and remained relatively consistent through 

2005 (Williams et al. 2004), though it is 

unclear if Annex V implementation was the 

cause of this decline. However, as the human 

population and the numbers of ships continue 

to increase along the U.S. coast, the threat of 

increased marine debris from both marine and 

land-based operations appears to be getting 

worse.

Other significant actions were taken 

during the 1980s to address the problem 

of marine debris and its effects on marine 

species, including: the creation of the Marine 

Entanglement Research Program (now the 

Marine Debris Program at the National 

Oceanic and Atmospheric Administration 

(NOAA)), the Marine Plastics Pollution 

Research and Control Act of 1987, a U.S. 

Navy waste disposal program, marine debris 

workshops and meetings, and beach sweeps 

(Laist et al. 1999; Laist and Liffman 2000). 

More recently, the Keep America Beautiful 

Initiative in the United States, the resolutions 

by the U.N. General Assembly, the outcomes 

of the Rio+20 Conference (SCBD 2012), the 

development of the Honolulu Strategy (UNEP 

2011), and the Global Partnership on Marine 

Litter (UNEP 2013) have highlighted the 

seriousness of the problem both in the U.S. 

and abroad.

This report presents a synthesis of the 

literature of entanglement of marine species 

in debris in the United States. A bibliography 

is attached for reference. Every attempt was 

made to distinguish between entanglement 

in active gear and entanglement in marine 

debris, though for some species, reports do 

not distinguish between the two types of gear 

and will eventually require further attention in 

future assessments. 

BACKGROUND

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2014 MARINE DEBRIS ENTANGLEMENT REPORT 

Literature on 11 species of pinnipeds 

in U.S. waters were reviewed, including: 

the northern fur seal (Callorhinus 

ursinus), Hawaiian monk seal (Monachus 

schauinslandi), California sea lion (Zalophus 

californianus), northern elephant seal 

(Mirounga angustirostris), Pacific harbor seal 

(Phoca vitulina richardsi), Atlantic harbor 

seal (Phoca v. vitulina), Steller sea lion 

(Eumetopias jubatus), Guadalupe fur seal 

(Arctocephalus townsendi), harp seal (Phoca 

groenlandica), gray seal (Halichoerus grypus), 

and hooded seal (Cystophora cristata). The 

pinniped with the most references to marine 

debris entanglement was the northern fur 

seal (n=26), followed by the Hawaiian monk 

seal (n=11), and the California sea lion and 

northern elephant seal (n=7 each). All of 

the literature pertaining to entanglement of 

pinnipeds in marine debris occurred from 

research conducted in Alaska, Hawaii, or 

California, with the exception of two studies 

from Cape Cod, MA on the east coast of the 

U.S. Pinnipeds were generally observed to be 

entangled around the head and appendages 

in net fragments, monofilament line, packing 

straps, rope, and rubber products. While 

entanglement can affect all age classes, 

juveniles and subadults appeared to be the 

most susceptible (Goldstein et al. 1999; Hanni 

and Pyle 2000). In a study from the southeast 

Farallon Islands from 1976–1998, Hanni 

and Pyle (2000) noted that of 914 entangled 

pinnipeds across five different species, 

sea lions (otariids) were most commonly 

entangled in fishing debris, but seals (phocids) 

were more commonly entangled in land-based 

debris. California sea lions appear to have the 

highest incidence of entanglement (Goldstein 

et al. 1999; Hanni and Pyle 2000; Dau et al. 

2009; Stevenson 2011), although Guadalupe 

fur seals, which are relatively rare in U.S. 

waters, had a much higher entanglement rate 

than California sea lions (15.4% and 3.8%, 

respectively) (Goldstein et al. 1999). This 

may be explained by better record keeping, 

along with an increase in the California sea 

lion population (Goldstein et al. 1999). Neck 

constrictions were prevalent in all species 

but most common in California sea lions 

and Steller sea lions. Hanni and Pyle (2000) 

reported neck constrictions of California 

sea lions in 70% of the entanglements with 

monofilament fishing nets and line being the 

most common source (13%). 

At least six studies reveal that entanglement 

from marine debris was less frequent than 

entanglements from active fishing gear 

(Stewart and Yochem 1985, 1987, 1990; Hanni 

and Pyle 2000; Swails 2005; Raum-Suryan et 

al. 2009). Marine debris entanglements ranged 

from 27% to 50% of the total entanglements 

in those studies. Nevertheless, the overall 

entanglement rates described in those reports 

are provided to indicate the general scale 

and trend of occurrence. California sea lion 

entanglement rates observed on beaches in 

the California Channel Islands increased 

from 0.08% in 1983–84 to 0.12% in 1988–89 

with a high of 0.16% from 1985–88 (Stewart 

and Yochem 1987, 1990). These observations 

were based on beach counts and may not 

reflect all entanglements, and may indicate 

a significant number of entanglements with 

active gear. Another source of information 

on entanglement rates comes from rescue 

centers. Goldstein et al. (1999) reported that 

from 1986–1998, 2.7% of California sea lions 

brought into a California marine mammal 

rescue center for rehabilitation showed signs 

of entanglement in marine debris. Over 90% 

of these were either yearlings or subadults, 

with the highest number recorded. While this 

may seem like an increase in entanglements 

over the 15-year period, this number is likely 

due to sampling methods. The Stewart and 

Yochem studies were confined to islands in 

the Southern California Bight, while Goldstein 

et al. reported on live stranded animals from 

coastal central California. Coastal central 

California entanglements peaked in 1992, 

potentially due to an El Niño (Goldstein et al. 

1999). Monofilament line and packing straps 

were the most prevalent debris type.

Entanglement rates for Steller sea lions may 

be increasing in Alaska. In 1986, Loughlin et 

al. (1986) reported an entanglement rate of 

0.07%, but between 2000–2007 Raum-Suryan 

et al. (2009), reported a rate of 0.26%. The 

latter study also found that of 386 entangled 

animals, 49% were entangled around the neck 

and 54% of these involved packing straps, 30% 

rubber bands, 7% each of net and rope, and 

2% in monofilament line (Jensen et al. 2009). 

Calkins (1985) noted that most individuals 

affected were 2–3 yr-old juveniles entangled in 

packing straps and net fragments.

Prior to 1983, northern elephant seal 

entanglement rates were estimated at 

approximately 0.08% (Stewart and Yochem 

1985), but increased somewhat to 0.15% in 

PINNIPEDS

“U.S. Pinnipeds were generally 

observed to be entangled around 

the head and appendages in net 

fragments, monofilament line, 

packing straps, rope, and rubber 

products. While entanglement 

can affect all age classes, juveniles 

and subadults appeared to be the 

most susceptible.”

3
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

1983–84 and 0.16% between 1984 and 1986 

in the Southern California Bight (Stewart and 

Yochem 1987). Goldstein et al. (1999) reported 

an entanglement rate of 0.4% among rescued 

elephant seals from 1986–1998, all of which 

were pups. However, Hanni and Pyle (2000) 

reported a negative trend in entanglements 

on the Southeast Farallon Island, CA from 

1976–1998. Of the 68 animals entangled 

there, 59% were entangled in marine debris 

other than nets and monofilament line. Most 

of these entanglements were packing straps 

(22%). Stevenson (2011) reported 22 northern 

elephant seals entangled in packing straps 

from 2001–2005 in central California and the 

U.S. Pacific Northwest coast.

Prior to 1983, Pacific harbor seal 

entanglement rates were estimated to be 

approximately 0.08% (Stewart and Yochem 

1985). This rate varied from 1983–1989 

between a low of 0% in 1983 to 0.06% from 

1984–-1986. Packing straps and other debris 

accounted for most of the entanglements 

(Stewart and Yochem 1987). Goldstein et 

al. (1999) reported an entanglement rate 

among rescued harbor seals of 0.28%, most 

of which (66.7%) were pups. The incidence 

of entanglement was considerably lower on 

the Southeast Farallon Island, with only three 

entangled harbor seals documented from 

1976–1998 (Hanni and Pyle 2000).

Guadalupe fur seals were the least 

reported of the pinniped species by number, 

apparently because of their lower numbers 

in U.S. waters and secluded habitat. Hanni 

et al. (1997) reported three of the 14 (21.4%) 

animals observed in California between 1988 

and 1995 with evidence of entanglement; one 

with polyfilament line around the neck, one 

with net markings, and one with hook and 

line. Entanglement in debris was evident with 

15.4% of the Guadalupe fur seals taken for 

rehabilitation from 1986–1998 (Goldstein et 

al. 1999). All of the interactions involved pups.

Only two studies were found that 

document entanglements among eastern 

U.S. pinnipeds. Swails (2005) conducted a 

study in Cape Cod, MA from 1999–2004 

and Bogomolni et al. (2010) conducted one 

on Cape Cod from 2000–2006. Both studies 

found a high incidence of debris entanglement 

for gray seals (33.3% in Swails and 37.9% in 

Bogomolni et al.), and significantly lower 

rates among harbor seals (7.4%), harp seals 

(1.9%), and hooded seals (0.0%) (Swails 

2005). Most of those entanglements, however, 

were believed to be from active fishing gear, 

and not necessarily caused by marine debris; 

an important distinguishing factor when 

determining management decisions. 

Credit: © AK Dept. Fish & Game, taken under federal permit #14325

Figure 1. Packing band debris entangled 

around the neck of a sub-adult Steller sea lion 

in Alaska. 
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

The first reported entanglement of a 

northern fur seal was reported in 1923 (Jensen 

et al. 2009). In the late 1800s and early 1900s 

their numbers declined significantly due to 

uncontrolled at-sea harvests of an estimated 

300,000 individuals. To prevent the decline, 

the harvesting nations (Canada, Japan, the 

Soviet Union, and the United States) signed a 

treaty in 1911 agreeing to ban at-sea harvests, 

which were non-selective for sex, in lieu of 

annual on-land harvest of juvenile males at the 

species rookeries to be managed cooperatively 

by the four harvesting nations. The new 

system stopped the decline, and the northern 

fur seal population subsequently increased 

to approximately 2 million seals by the 1940s 

(French and Reed 1990). Beginning in 1956, 

the harvest was expanded to include juvenile 

females based on a theory that the action 

would increase the fitness of surviving females, 

and after a brief decline in abundance, the 

population would stabilize and pup production 

would increase, thereby increasing the harvest 

potential. The population subsequently began 

declining as expected, but the decline did not 

stabilize, which then ended this practice in 

1968 (French and Reed 1990).

The population continued its decline 

through the 1970s prompting numerous 

investigations that implicated entanglement 

in marine debris as a significant contributing 

factor (Fowler 1985; Swartzman et al. 1990; 

Laist 1997; Fowler 2000). However, hypotheses 

suggesting that marine debris has a large 

impact on the size of the fur seal population of 

the Pribilof Islands (in the Bering Sea, off the 

coast of Alaska) have been challenged because 

of either low sample size or insufficient 

observations; more specifically due to few 

observations of entangled seals on land and 

unverified large numbers of entangled seals at 

sea (Trites et al. 1992). By 1976, an estimated 

40,000–50,000 fur seals per year were 

estimated to be killed by strapping bands from 

bait boxes and netting, and the population was 

declining at a rate of 4–6% per year (Fowler 

1982; Laist 1997; Derraik 2002) and continued 

declining into the 1980s (Fowler 2000). When 

French and Reed (1990) used a model to 

include subadult male entanglement rates and 

mortality combined with adult female harvest 

and entanglement mortality, the decline 

due to entanglement in marine debris was 

estimated to be 1% per year, slower than in the 

1970s. They proposed that a 20% reduction 

in entanglement mortality rates would 

sufficiently stop this decline. During the 1990s, 

the Pribilof Islands population remained stable 

(Laist 1997) and was estimated to be 1,002,516 

in 1996 (NMFS 1998). These estimates are 

based on the estimated number of pups born 

in the rookeries multiplied by expansion 

factors from life table analyses (Lander 

1981; NMFS 1998). However, the population 

declined to an estimated 721,935 by 2006 

(NMFS 2007) and to 611,617 by 2011 (Allen 

and Angliss 2012). With entanglement rates 

staying constant (see below) from the 1990s, it 

is likely that factors other than marine debris, 

such as climate change, prey availability, El 

Niño events, and migration of adult females 

to a rapidly expanding rookery on Bogoslof 

Island along the Aleutian Island chain may 

have caused a recent decline in the Pribilof 

Islands population (NMFS 2007). However, 

entanglement rates may be considered 

conservative since monitoring of at-sea 

entanglements are not figured into the data.

The majority of entanglements appear 

to involve strapping bands from bait boxes 

used by fishermen and trawl net debris 

<150g (Fowler et al. 1990); trawl nets were 

estimated to make up between 49–72% of 

all entanglements (Scordino 1985; Fowler 

1987; Baba 1995; Kiyota and Baba 2001). In 

a one-year study of fur seal entanglement, 

70% of entangled animals (primarily subadult 

males) were able to shed the debris (Scordino 

1985), though larger fragments of net may 

prevent seals from returning to land or result 

in their death (Fowler et al. 1990). In 1988, 

a 50% reduction in trawl net entanglements 

occurred, possibly due to mariner education 

and less discarded or lost gear (Fowler et 

al. 1990), or the institution of MARPOL 

Annex V (Ribic et al. 1994). It is difficult to 

ascertain which measure had a greater effect 

on the reduction, but both may have played 

a significant role. Entanglements in packing 

straps decreased from 48–55% in the 1970s 

to 16–26% in the early 1980s (Scordino 1985) 

and remained around 14% until 1993 (Baba 

1995). 

Juvenile fur seals are the most affected by 

entanglement in debris, possibly because their 

playful nature and curiosity attracts them to 

floating nets (Yoshida and Baba 1985; Laist 

1997; Fowler 2000). Fowler (1985, 1987) 

estimated that juvenile entanglement mortality 

during their first two years at sea could be 

as high as 15%. Entanglement rates with 

juveniles were similar or lower in the 1990s 

Northern Fur Seal

Figure 2. The graph shows the percentage of entangled northern fur seals observed in surveys conducted on the Pribilof Islands during the commercial fur seal harvest (1967–84), during research “roundups” (1985–92), and during the subsistence harvest (1995–2005). Source: Zavadil, P.A., A.D. 

Lestenkof,K. Holser, A. Malavansky and B.W. Robson. 2007. Northern Fur Seal Entanglement Studies on the Pribilof Islands in 2005.

5
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

(Jensen et al. 1998). Females were entangled 

less often, at about half the entanglement rate 

of males (Delong et al. 1990). Although, there 

is evidence to suggest that entanglement of 

females affects reproductive success (Scordino 

1985; Fowler 1987). Entanglement rates for 

females ranged from 0.06% in 1985 to 0.23% 

in 1986 (Delong et al. 1990) and 0.013% from 

1991–1999 (Kiyota and Baba 2001), much 

lower than the average 0.4% for juvenile males 

(Delong et al. 1990; NMFS 2007). Behavioral 

traits between sex and age may account for 

differences in entanglement rates, as juveniles 

tend to be more curious with objects in their 

environment (Kiyota and Baba 2001).

Entanglement rates of northern fur seals 

(as measured by the proportion of animals 

seen entangled on rookeries) have been 

recorded since the late 1960s and are some of 

the highest of any pinniped species (Antonelis 

et al. 2006). Entanglement rates on the Pribilof 

Islands steadily increased from the late 1960s 

(low of 0.15%) through 1975 (high of 0.71%), 

when the popularity of synthetics in fishing 

gear expanded (Fowler 1985). Entanglement 

rates since 1975 have hovered around 0.4% 

with the exception of 2002–2003, when the 

rates increased to about 0.5% (see Figure 2; 

Fowler 1985; Scordino 1985; Baba et al. 1990; 

Delong et al. 1990; Fowler et al. 1990; French 

and Reed 1990; Baba 1995; NMFS 2007; 

Williams et al. 2004). 

The decline of fur seal entanglement 

The endangered Hawaiian monk seal 

is a tropical seal found only the Hawaiian 

Archipelago; most monk seals now occur in 

the remote Northwestern Hawaiian Islands 

(NWHI). The seal population is estimated to 

be 1,212 (Carretta et al. 2013) and has been 

declining since the 1950s (Lowry et al. 2011). 

Among the major threats to the species is 

entanglement in marine debris (Henderson 

2001; Boland et al. 2003). The monk seal 

was hunted to near extinction in the 1800s 

and early 1900s. Although the species likely 

recovered to some extent during the first half 

of the 1900s, between the mid-1950s—when 

the first seal counts were made—and the 

mid-1990s, the population had declined to 

one-third of its size due at least in part to 

entanglement in trawl nets and other debris 

that drift into the NWHI from other areas 

(e.g., Alaska, Russia, Japan) and accumulates 

along the beaches and in lagoon reefs of atolls 

(Donohue et al., 2001). In 2000, President 

Clinton imposed an order to designate a 

reserve within 50 nautical miles of the NWHI 

Hawaiian Monk Seal

rates could be due to many factors, including 

changes in fishing practices in seal habitat 

(Laist 1997; Kiyota and Baba 2001). This raises 

concern that the data presented may include 

entanglements that occurred in actively-fished 

gear. Although, many of the papers do specify 

net fragments, which can be considered 

marine debris along with packing straps and 

other debris. Nevertheless, other debris besides 

netting is described and probably constitutes 

a smaller but still significant amount of 

entanglement debris.

Credit: NOAA Fisheries, Pacific Islands Fisheries Science Center, taken under Marine Mammal Permit #10137 (Ilana Nimz photographer)

Figure 3. A Hawaiian monk seal lays along the shoreline with 

a fishing net entangled around its neck. 

6
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

to restrict fishing. Therefore, nearly none 

of the entanglements in this area involve 

gear that is fished in the NWHI. Since then, 

substantial efforts have been made to remove 

net debris from NWHI lagoons and Islands. 

In 2002, this habitat was designated as a 

National Marine Sanctuary (Marine Mammal 

Commission 2003) and was designated as 

the Papahanaumokuakea Marine National 

Monument in 2006 by President Bush. In the 

1990s, entanglements averaged 15 individuals 

per year and 25 were recorded entangled in 

1999. These entanglements declined from 

2000–2002 (5, 8, 10, respectively) (MMC 

2003), possibly due to clean up efforts. From 

2003 to 2011, the number of entangled monk 

seals has fluctuated between 5 and 16 per year 

(MMC 2012). 

Marine debris entanglements of monk 

seals were first described in 1969, with other 

reports occurring in Balazs (1979) and Andre 

and Ittner (1980). Monk seals are commonly 

entangled in trawl net fragments, packing 

straps, and monofilament line. For example, 

of 35 monk seals documented as entangled 

(n=27 seals) or having entanglement scars 

(n=8 seals) between 1974 and 1984, 49% 

(n=17 seals) were able to free themselves 

(Henderson 1985). From 1985–1988, 34 

entanglements were recorded mainly in 

monofilament lines, nets, and packing straps. 

Figure 4. Number of entangled Hawaiian monk seals observed from 1992 through 2011. Data provided 

by the National Marine Fisheries Service, Pacific Islands Fisheries Science Center (MMC 2012).

Most entanglements, like most monk seals, 

are found in the NWHI at the six major monk 

seal breeding colonies. Entanglement rates 

can vary significantly between years and at 

different breeding colonies. Based on estimates 

of monk seal abundance and observed 

entanglements at different breeding colonies, 

among those that have experienced some of 

the highest entanglement rates are colonies at 

Kure Atoll in 1988 (71.5%; 5 of 7 seals), Laysan 

Island in 1988 (2.1%; 7 of 331 seals), and 

Lisianski Island in 1992 (3.7%; 8 of 217 seals) 

(MMC 1994). Most of those seals were either 

disentangled by field crews, or were able to free 

themselves. Between 1982 and 2011, 311 monk 

seals were documented as being entangled in 

marine debris (Figure 4; MMC 2012). 

Overall marine debris entanglement 

rates for the entire population from 1982 to 

2005 have been summarized by Donohue 

and Foley (2007) (Figure 4). However, these 

entanglement rates are based on the number 

of entanglements divided by the product of the 

number of annual observation days and the 

mean of the annual beach counts, a method of 

calculation that is different than reported by 

the MMC (2012), where the total population 

estimate is considered based on the NMFS 

Stock Assessment Reports. The entanglement 

rate increased from 0.06% to 0.48% from 

1985 to 1988 (Henderson 1990) and did not 

decrease after MARPOL Annex V, except 

for a decrease in 1990 to 0.10% (Henderson 

2001). In fact, the entanglement rate climbed 

to 0.70% by 2004 (Donohue and Foley 2007; 

USEPA 2011). This elevated rate was attributed 

to an El Niño event that concentrated marine 

debris in monk seal habitat (Donohue 

and Foley 2007). Entanglement rates for 

Hawaiian monk seals are variable and cyclical, 

corresponding to El Niño effects when the 

Southern Tropical Convergence Zone (STCZ) 

moves southward toward the range of the 

Hawaiian monk seal (Donohue and Foley 

2007). The southward movement of the STCZ 

also generally results in higher observed 

entanglement rates.

7
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

Cetaceans (whales and dolphins) are 

affected by marine debris entanglement all 

over the world. Recorded entanglement events 

have been documented for at least 60% (6 of 

10 species) of the baleen whales (mysticetes) 

and 8% (5 of 65 species) of the toothed whales 

(odontocetes) (Laist 1997, 1999). While 

fishing gear, likely including at least some 

abandoned, lost or otherwise discarded fishing 

gear (ALDFG), constitutes the vast majority of 

baleen whale entanglements, a broader array 

of ALDFG appears to pose entanglement risks 

for bottlenose dolphins and perhaps other 

odontocetes. Thus, most entanglement records 

pertain to incidental or by-catch in actively 

fished gear, instead of entanglement in marine 

debris (Laist 1997; Baulch and Perry 2012; 

Butterworth 2012). 

Worldwide, Baulch and Perry (2012) list 15 

species of cetaceans involved in entanglement 

in marine debris, which is 4 more species than 

listed by Laist (1997). In the United States, the 

literature presented 8 species of mysticetes 

and one odontocete species as entangled in 

fishing operations or marine debris. Most 

individuals are entangled in actively fished 

gear, either through chance encounters with 

lines or nets, or from attempting depredation. 

Some, however, also become entangled in 

lost or otherwise abandoned gear they may 

encounter while swimming or feeding. The 

nine cetacean species documented in this 

review to be impacted by debris appears to be 

a conservative estimate of the total number 

of cetaceans that are potentially entangled 

in marine debris in the U.S. As Simmonds 

(2012) acknowledges in a similar review, many 

institutions that record cetacean strandings 

and sightings rarely publish reports on single 

animals that may be affected. For example, 

Sadove and Morreale (1990) reported on 

4 species of mysticetes and 13 species of 

odontocetes entangled in netting, trap line, or 

longline in the New York Bight, but the report 

does not specify which species were entangled 

in active fishing operations and which were 

indeed marine debris.

Baleen whales with entanglement reports, 

include: the humpback whale (Megaptera 

novaeangliae), the North Atlantic right 

whale (Eubalaena glacialis), the minke whale 

(Balaenoptera acutorostrata), the gray whale 

(Eschrichtius robustus), and the bowhead 

whale (Balaena mysticetus). However, the 

only baleen whales for which entanglement 

records have clearly been attributed to marine 

debris as opposed to active gear are humpback, 

right, minke, gray, and bowheads (Laist 1997, 

Baulch and Perry 2012). The only odontocete 

species where marine debris entanglement 

was evident were the sperm whale (Physeter 

macrocephalus), the bottlenose dolphin 

(Tursiops truncatus), the harbor porpoise 

(Phocoena phocoena), and the Dalls porpoise 

(Phocoenoides dalli). 

Common sources of entanglements for 

baleen whales included line and net fragments 

attached through the mouth or around the tail 

and flippers. Most reports of entanglements 

of baleen whales did not specify marine 

CETACEANS

debris as the source, but Baulch and Perry 

(2012) and Macfadyen et al. (2009) tried to 

exclude reports that contained entanglement 

in active fishing gear and concentrated on 

ALDFG. Bottlenose dolphins were the most 

commonly entangled odontocete, with most 

entanglements involving monofilament line, 

net fragments, and rope attached commonly 

to the appendages. Anecdotal reports 

from stranding networks also mention 

entanglements in packing straps and rubber 

gaskets.

Entanglement rates in marine debris 

were nearly impossible to decipher because 

of the high incidence of reports that did not 

distinguish between ALDFG, active fishing 

gear, and marine debris in their analyses. 

However, Baulch and Perry (2012) reported 

that entanglement of cetaceans in marine 

debris has increased dramatically in recent 

decades, but data to document the extent of 

increase are generally insufficient to accurately 

quantify recent trends. 

“Common sources of 

entanglements for baleen 

whales included line and net 

fragments attached through 

the mouth or around the tail 

and flippers.” 

8
Reports of entangled humpback whales in 

the U.S. (n=18) constituted the vast majority 

of papers on baleen whale entanglement. 

However, most of these reports did not 

distinguish between entanglements in marine 

debris and active fishing gear, and most 

were from annual Stock Assessment Reports 

on mortality of baleen whales from the 

National Marine Fisheries Service (NMFS). 

All but three reports (Jensen et al. 2009; 

Neilson et al. 2009; Lyman 2012) described 

humpback whales from the eastern U.S. and 

Gulf of Maine. Four of the reports described 

entanglements based solely on scarring 

with no indication of what type of material 

inflicted these wounds, which would provide 

information on the source of the debris 

(Robbins and Mattila 2001, 2004; Neilson et al. 

2009; Robbins 2012). A vast majority of these 

reports, however, likely involve interactions 

with active gear rather than debris.

Nearly all (98%) of the marine debris 

entanglements of cetaceans were with ALDFG 

as opposed to land-based marine debris, 

mostly pot trap lines and nets worldwide 

(Baulch and Perry 2012), and this seemed to 

be the case with humpback whales. Wiley et 

al. (1995) reported that as much as 25% of the 

stranded humpback whales observed between 

1985 and 1992 from Virginia to North 

Carolina could be attributed to entanglement, 

and that annual mortality rate may be 4.8% 

when added to natural mortality of Gulf of 

Maine humpbacks (Volgenau et al. 1995).

The difficulty in describing annual 

mortality rates caused by marine debris for 

baleen whales is evident as gleaned from 

reports such as Johnson et al. (2005) and 

Jensen et al. (2009), where 73% and 76%, 

respectively, of fishing gear attached to 

humpbacks was from a known fishery and 

likely being actively fished. The remaining 

entanglement proportions (i.e., 27% and 24%) 

were from unknown sources that could have 

included marine debris. Either way, the case 

can be made that humpbacks are vulnerable to 

entanglement in debris, though entanglement 

in marine debris appears to be considerably 

less than entanglement in fishery operations. 

Keeping this bias in mind, the following 

entanglement rates include both presumed 

actively fished entanglements and sources that 

are unknown (presumably including at least 

some marine debris). 

The data extrapolated from Johnson et al. 

(2005) from 1993–2002 provide an annual 

entanglement-caused mortality rate of three 

Humpback Whales

Figure 5. (Right). NOAA’s Marine Mammal 

Health and Stranding Response Program 

from the Hawaiian Islands Humpback Whale 

National Marine Sanctuary respond to and 

aid an entangled humpback whale.

Figure 6. (Left) A humpback whale entangled 

in fishing gear swims near the ocean’s surface.

Credit: Courtesy of HIHWNMS (NOAA MMHSRP Permit #932-1489) - 2/28/05

Credit: Courtesy of HIHWNMS (NOAA MMHSRP Permit #932-1489) - 2/28/05
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

humpback whales per year along the U.S. 

East Coast. Most of these entanglements were 

around the tail and mouth, with pot gear and 

net representing the most common gear types. 

Entanglement data for the U.S. East Coast 

and Canadian Provinces were described in 

NMFS reports from 2000 to 2010 (Cole et 

al. 2006; Nelson et al. 2007; Glass et al. 2008, 

2009, 2010; Henry et al. 2011, 2012), with each 

publication covering five years, although these 

years overlapped (e.g., 2000–2004; 2001–2005, 

etc.). Data from 2000–2004 (Cole et al. 2006) 

and 2005–2009 (Henry et al. 2011) were used 

to extrapolate entanglement rates for those 

periods. The entanglement rate appears to be 

increasing, since rates increased from 14.4 

animals per year (2000–2004) to 18.8 animals 

per year (2005–2009). 

In Alaska, extrapolating data from Jensen 

et al. (2009), an entanglement rate of 8.8% per 

year was found between 1997 and 2007. Only 

24% of the entanglements were from unknown 

sources, possibly including marine debris, 

and the rest clearly were from active fishing 

operations mainly involving pot gear and 

nets. Similarly, Neilson et al. (2009) describe 

most of the entanglements (77%) from pot 

gear and nets, and the remaining unknown. 

Entanglements were suggested to be increasing 

over time (Neilson et al. 2009).

The lone report from Hawaii described 

entanglements found in the Hawaiian Islands 

Humpback Whale National Marine Sanctuary 

but included some animals that likely became 

entangled in their northern feeding grounds 

and carried those lines to their winter calving 

grounds in Hawaii. For example, 10 animals 

with gear observed in Hawaii have also been 

sighted with gear in Alaska, with one animal 

traveling over 2,450 nautical miles with gear 

attached (Lyman 2012). This report also noted 

that humpbacks are frequently entangled in 

fishing pot gear, monofilament (net or line 

is not described), moorings, longline, and 

marine debris (Figure 5 & 6; Lyman 2012). 

Only 8% of the affected animals were 

found entangled in marine debris as opposed 

to entangled in actively fished gear, and 

these incidents have increased over time. 

Additionally, as mentioned previously, four 

studies described reports of observed whales 

with scars on their tails, indicating past 

entanglement events (Robbins and Mattila 

2001, 2004; Neilson et al. 2009; Robbins 2012). 

Yearlings and juveniles appear to have the 

highest incidence of entanglement (Robbins 

and Mattila 2001; Robbins 2012), although 

adults have more scars (Neilson et al. 2009). 

From 1997–2010, the acquisition of new 

entanglement scars varied from year-to-year 

between 6% and 26% (Robbins 2012). Robbins 

and Mattila (2001) noted that between 48–68% 

of animals have had a past entanglement and 

17% showed new entanglement scars after 

one year of observation (Robbins 2012). It is 

evident, therefore, that a significant number 

of animals are becoming entangled, but are 

able to shed their burden of lines and netting. 

The disentanglement rate of fishing gear from 

whales is low and likely not a strong mitigating 

measure to eliminate the impacts of marine 

debris and ALDFG.

Numerous studies have been completed on 

mortality of this critically endangered baleen 

whale. With approximately 450 individuals 

in the population (Waring et al. 2013), 

analysis of mortality is critically important. 

As with humpback whales, the problem with 

entanglement records for this species is they 

are largely assumed to involve active fishing 

gear and entanglements in marine debris 

appear to be relatively infrequent. Most of the 

literature reviewed (n=15) documents whales 

that have become entangled in pot lines, nonmobile gear, lines, and nets. 

Recently, Knowlton et al. (2012) conducted 

a 30-year (1980–2009) comprehensive review 

of entanglement rates using photographs of 

right whales. In the report, 626 individuals 

were observed and 82.9% showed 

entanglement, and 80% of those observations 

involve entanglement in non-mobile pot 

gear and nets. The other 20% constituted 

entanglement from unknown sources, but 

mainly from rope. The overall entanglement 

rate was 25.9% for the 30-year period, with 

the highest rate coming in 1983 with 50%. A 

seven-year pattern of high entanglement rate 

exists but is not explained by the authors. If 

we consider that 20% of the entanglements 

that came from unknown sources are marine 

debris, the best estimate for a marine debris 

entanglement rate over the 30-year period 

would be 4.2%. Caution should be noted 

here in that this estimate likely contains cases 

where entanglements occurred in active gear, 

and future efforts should take care in trying 

to separate whale entanglement via actively 

fished gear and via marine debris. Despite 

the limited capacity to assess the difference in 

these entanglement rates, this study suggests 

that right whales are indeed likely being 

impacted by marine debris, suggesting that 

further action is required to assess the extent 

of entanglement of these whales in marine 

debris and to promote action to eliminate this 

impact on these animals.

North Atlantic 

Right Whale

10
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

The bottlenose dolphin is one of the most 

studied cetacean species because of its nearshore habitat of coastal oceans, bays, sounds, 

and rivers. However, few reports exist that 

document the entanglement of these animals 

in marine debris. This review provides one of 

the first compilation of reports documenting 

marine debris entanglement of this species. 

Many reports of individual animals entangled 

in fishing gear and marine debris are found 

in unpublished, “gray” literature from various 

research institutions and academia, as well 

as media reports. The reports described here 

(n=12) are all from the east coast of the U.S. 

and Gulf of Mexico, specifically Virginia, 

South Carolina, and Florida.

Anecdotal evidence has shown that 

bottlenose dolphins can become entangled in 

various forms of marine debris, including: net 

fragments, monofilament line, rubber gaskets, 

rope, clothing, and other forms of debris. 

Mann et al. (1995) described a dolphin calf 

entangled in monofilament line that eventually 

was shed after weeks of observation. Wells 

et al. (1998) observed two of 11 dolphins 

recovered dead in Sarasota, FL from 1993–

1996 entangled in monofilament line. Many 

individuals bare scars from past entanglements 

as evidenced by Wells and Scott (1994), where 

11% of dolphins handled during live capturerelease studies from 1975–1990 showed past 

entanglement from fishery gear or marine 

debris. The resident population in Sarasota 

and their interactions with fishing gear and 

humans have been studied for decades. In 

a study from 2000–2007, Powell and Wells 

(2011) determined that nearly 2% of this small 

population died in 2006 due to entanglement 

or ingestion of recreational fishing gear, a level 

that may not be sustainable. Depredation of 

caught fish or bait from recreational fishing 

lines was thought to be the major cause of 

these deaths and, while not directly marine 

debris, it could expose these animals to 

discarded fishing line. By 2007, 14% of the 

population was observed either entangled 

in recreational fishing gear or exhibiting 

depredation behaviors (Powell and Wells 

2011), a trend that has increased over time. 

Wells et al. (2008) concluded that eight of the 

12 entanglements recorded from 1988–2007 

involved debris, including seven that were 

caught in discarded monofilament line and 

one in a man’s bathing suit. Thirty-eight other 

dolphins showed evidence of scarring from 

past entanglements.

In part due to the entanglement in 

monofilament line described above, a Florida 

Entanglement Working Group was established 

in 2003 (Bassos-Hull and Powell 2012). This 

group reports on entanglements in dolphins, 

manatees, and sea turtles on an annual basis. 

From 1997–2009, 132 bottlenose dolphins 

were reported entangled or with ingested 

fishery-related gear and other types of debris 

statewide (Bassos-Hull and Powell 2012). 

Of these, 73.5% were from hook and line 

or monofilament line, while 6% from other 

types of material. While Bassos-Hull and 

Powell (2012) and Bassos-Hull (2013) do not 

specify marine debris as the source of those 

entanglements, they do report entanglement 

“hot spots,” including the Indian River Lagoon 

of the east coast of Florida, the central west 

coast (Sarasota–Tampa), the southwest coast, 

and the Florida Keys.

In the Indian River Lagoon, monofilament 

line appears to be the most common source of 

bottlenose dolphin entanglements (Lelis 2012; 

Stolen et al. 2013). From 1997–2009, 2.7% 

of all stranded dolphins were entangled in 

monofilament line caught largely on the dorsal 

Bottlenose Dolphin

fin and other appendages. If you exclude 

the number of animals observed where 

interactions with active gear could not be 

determined, then 6.1% of these animals were 

entangled in ALDFG monofilament line. 

In South Carolina , entanglements in 

marine debris include monofilament line, 

rope, and past net entanglement observed in 

the stranding record. Marine debris such as 

rope fragments and packing straps have been 

photographed on free-swimming dolphins (W. 

McFee, unpublished data, NOAA) (Fig. 4). 

McFee and Hopkins-Murphy (2002) observed 

an overall entanglement rate of 10.8% (or 

1.8/yr) in marine debris from 1992–1996, 

primarily from monofilament line and rope 

fragments, excluding those cases where the 

source could not be determined. That rate 

increased over the next seven years (1997-

2003) to 12.3% (or 2.1/ yr) (McFee et al. 

2006). This rate was greatly influenced by the 

high number of entanglements in 1997–1998. 

From 2004–2012, the entanglement rate has 

decreased, providing an overall entanglement 

rate since 1992 of 8.8% (1.7/ yr) (Fig. 5; W. 

McFee, unpublished data, NOAA). 

Figure 7. Percentages of bottlenose dolphins stranded in South Carolina that were found entangled in 

active fishing gear and marine debris. Source: McFee and Hopkins-Murphy 2002; McFee et al. 2006; 

McFee, unpublished data.

11
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

The Secretariat of the Convention on 

Biological Diversity (SCBD) (2012) reported 

52 marine mammal species with entanglement 

records worldwide. Many of these species 

occur in the United States. Other marine 

mammals that have been found in the 

literature with entanglement records in U.S. 

waters are the Florida manatee (Trichechus 

manatus latirostris) (O’Shea et al. 1985; Beck 

and Barros 1991; Nill 1998; Spellman 1999; 

Bassos-Hull and Powell 2012; Bassos-Hull 

2013) and sea otter (Enhydra lutris) (Degange 

and Newby 1980; Moore et al. 2009).

While human-related manatee deaths 

are generally associated with watercraft 

mortality, there are reports of this species 

being entangled and killed in debris from 

monofilament line and rope. The best source of 

information comes from the Florida Wildlife 

Commission website, though it is difficult to 

parse out marine debris entanglement from 

this dataset. From 2003 to 2007, 29 salvaged 

manatee carcasses were found entangled in 

marine debris consisting of monofilament 

line, nets, and rope, representing 0.6% of the 

total (1,805) dead manatees collected over 

this period (FWC Florida Manatee Stock 

Assessment Report, 2009). During the same 

period, ~25% of animals that were successfully 

OTHER MARINE MAMMALS

rescued were entangled in marine debris. 

This was far more than the 2.7% that were 

entangled and rescued from 2007 to 2011 

(FWC Florida Manatee Stock Assessment 

Report, 2013). Beck and Barros (1991) 

reported 2.5% mortality from entanglement 

between 1974 and 1985. From 1983 to 1999, 

29.5% of rescued manatees were entangled in 

monofilament lines, nets, and packing straps 

(Spellman 1999). Over 49% of these animals 

were adult females. Some of these animals 

required surgical amputation of forelimbs 

or had lost forelimbs due to entanglement. 

Furthermore, given that Florida manatee 

populations are quite low (~3,800) (FWC 

FWRI Manatee Synoptic Aerial Surveys 2009), 

future efforts should identify the types and 

sources of debris leading to manatee deaths 

and act to prevent these mortality events.

Isolate incidents over a wide area

Often difficult to detect entangled animals at sea when 

they surface; easier on stranded animals

Detection at sea difficult if floating below surface or 

concealed in matted debris

Some dead animals are held underwater by debris 

anchored on the sea floor

Entangled dead animals may disappear quickly through 

sinking or predation.

Limited at-sea sampling

Few long-term surveys

Inconsistent sampling methods

Strandings are an unknown portion of total mortality;

Shore counts of live entangled animals are biased 

toward survivors with minor amounts of debris and less 

serious injuries

Limited efforts and ability to distinguish entanglements 

caused by active gear vs. marine debris 

Detection and Discovery Sampling and Reporting Biases

Table 1. Factors complicating the analysis of marine entanglement (adapted from Laist 1997 and Gregory 2009).

As with other marine species, 

environmental factors and changing fishing 

practices and gear affect annual entanglement 

rates. Increased entanglement in monofilament 

line in Sarasota, FL was suggested to be caused 

by harmful algal blooms, with reductions in 

available prey species causing dolphins to 

change their foraging strategies in ways that 

increased their exposure to human activities 

and debris (Powell and Wells 2011). An 

increase in marine debris entanglements 

in South Carolina from 1996–1998 was 

unexplained, but also occurred in El Niño 

Southern Oscillation years. New fishing gear 

that ends up as debris also can be detrimental. 

Barco et al. (2010) identified Spectra® twine 

as a source of lines entangling a dolphin in 

Virginia and causing lacerations that were 

more severe than typical monofilament line of 

the same diameter. This line had encrusting 

algae on it, which suggests it may have been 

ALDFG; it apparently was causing more drag, 

facilitating deep cuts in the flukes.
Worldwide it is estimated that at least 

67 species of sea birds are entangled in or 

ingest plastic (SCBD 2012). Laist (1997) lists 

138 species worldwide with entanglement or 

ingestion records, with 19 species of sea birds 

specifically entangled in marine debris found 

in the United States. Moore et al. (2009) lists 

some of the same species but provides an 

additional 22 species, and Harris et al. (2006) 

lists three other species, bringing a minimum 

estimate of sea birds entangled to 44 species 

in the Continental U.S. and Hawaii. Moore 

et al. (2009) point out that inconsistencies 

in distinguishing between entanglement in 

actively fished gear and marine debris make 

it difficult to assess the effect of marine debris 

on sea birds. Nevertheless, from 2001–2005, 

entanglement rates ranged from 0.2% to 

1.2% for all sea birds observed by beach 

monitoring programs in California, Oregon, 

and Washington. A majority of entanglements 

involved fishing gear such as monofilament 

line and hooks, but 8.3% of the entanglements 

were from non-fishery-related items. Common 

murres and western gulls were the most 

common species found entangled. 

In a review of bird and pinniped 

entanglements in five rehabilitation facilities 

throughout California from 2001–2006, Dau et 

al. (2009) found entanglements to be the cause 

of 31.1% of rescued brown pelicans (Pelecanus 

occidentalis) and 11.1% of rescued gulls (Larus 

spp.). The area of greatest entanglement for 

brown pelicans was Monterey Bay (59.6%; 

180/302), and for gulls was Los Angeles 

and Orange Counties (16.1%; 92/572). The 

majority of these entanglements were fishery 

related including monofilament line and hook. 

Sea birds have also been found dead in 

derelict fishing nets (Figure 8 – below). Diving 

birds appear to be susceptible to entanglement 

in nets while pursuing fish underwater (Good 

et al. 2007; Gilardi et al. 2010). Good et al. 

(2007) described seven species of sea birds, 

mainly cormorants, dead in derelict fishing 

nets in the Northwest Straits and Puget Sound. 

Brandt’s cormorant, the common loon, and 

western grebe were identified as species of 

special concern for derelict net entanglements 

in Washington (Good et al. 2007; Gilardi 

et al. 2010). Degange and Newby (1980) 

also documented 99 sea birds (five species) 

entangled in a single derelict high-seas salmon 

drift net in 1978. Harris et al. (2006) surveyed 

beaches in Cape Cod, MA and found 6.7% of 

dead beach-cast sea birds were entangled in 

hook, monofilament line, or nets. However, 

they go on to report that 2.2% were also 

entangled in marine debris in 2003–2004.

Besides the risk of entanglement from 

derelict nets and fishing gear, sea birds are 

also susceptible to entanglement from plastics 

and other synthetic materials that they may 

gather for making nests (Fig. 8) (Votier et al. 

2011; Butterworth 2012). Podolsky and Kress 

(1989) observed cormorants in Maine making 

nests from plastic marine debris including net 

fragments and fishing line. In their opinion 

the biggest threat of entanglement was to 

the chicks, though no entanglements were 

observed.

Many coastal states have undertaken 

certain efforts to reduce entanglement rates 

through marine debris clean-up measures 

and installed fishing line recycle centers at 

boat landings in part due to entanglement 

of sea birds and other marine species. One 

such program is the California Lost Fishing 

Gear Recycling Project administered by 

the University of California–Davis Wildlife 

Health Center that began in 2005. Research 

on alternative materials for non-consumables 

has also been done, including a study on a 

biodegradable material for six pack rings 

(Thompson and Cote 1997). This study in 

Maine used Triton cardboard six pack holders 

on ducks and determined that not only did the 

ducks easily shed them but also the material 

degraded within 30–60 days.

SEA BIRDS

Figure 8. A dead shearwater 

seabird entangled in a derelict 

fishing net.

Credit: NOAA Fisheries Pacific Islands Regional Office
SEA TURTLES

In an initial review of entanglement cases 

of sea turtles in marine debris worldwide, 

Balazs (1985) found no cases before 1950 

and 95% of the cases occurred after 1970.

The absence of entanglement records 

prior to 1950 could be from the low use of 

synthetic materials in fishing practices and 

land-based products, as mentioned with 

northern fur seals, and through lack of 

awareness of the problem. For the latter, the 

Sea Turtle Stranding and Salvage Network 

did not begin until 1980 and since then 

has been instrumental in exposing the 

problem. All seven species of sea turtle have 

been reported entangled in marine debris 

globally (SCBD 2012). Six of the seven 

species occur in U.S. waters where reports 

have documented entanglements: green 

(Chelonia mydas), loggerhead (Caretta 

caretta), hawksbill (Eretmochelys imbricata), 

Kemp’s Ridley (Lepidochelys kempi), Olive 

Ridley (Lepidochelys olivacea), and leatherback 

(Dermochelys coriacea). The behavior of sea 

turtles makes them particularly vulnerable to 

entanglement. For example, young sea turtles 

tend to seek shelter under floating objects 

to avoid predation (Carr 1987; Stevenson 

2011). These areas are also a source of food, 

as small marine animals also congregate 

here. Unfortunately, sea turtles tend to align 

themselves with oceanic fronts, convergences, 

rip, and driftlines where marine debris often 

occurs (Balazs 1985; Carr 1987). As such, 

sea turtles are susceptible to entanglement 

in all forms of marine debris that can form 

loops and openings that could catch on and 

appendages (Fig. 7). 

Balazs (1985) lists 52 cases in U.S. waters 

between 1973 and 1984. Most of the reports 

were of green turtles from Hawaii (46%), with 

other species, including green, from Florida 

and Texas, and single reports from New York, 

Rhode Island, and California. From 1980–

1992, Teas and Witzell (1995) reported 52 sea 

turtle entanglements per year from stranding 

network beach observations combining data 

from the Gulf of Mexico, southeast U.S., 

northeast U.S., and U.S. Caribbean. Of these, 

54.7% were entangled in fishing gear including 

monofilament line, rope, and net while 

6.8% were entangled in other marine debris 

including burlap bags, six pack rings, onion 

bags, packing straps, steel cables, plastic bags, 

rubber gloves, beach bottles, and other debris; 

much of which likely originated from the 

shrimping fishery (Miller et al., 1995). Most of 

the entangled sea turtles were loggerheads. In 

Texas and the northern Gulf of Mexico, 3.5% 

to 7.5% of the sea turtles observed stranded 

in the late 1980s were entangled in marine 

debris (Plotkin and Amos 1990; Duronslet et 

al. 1991). Most of these were Kemp’s Ridley 

turtles, with hawksbill turtles showing a 

propensity for entanglement in plastic bags 

(Plotkin and Amos 1990). Leatherbacks have 

been commonly entangled in monofilament 

line (Innis et al. 2010), presumably from 

active fishing gear as suggested from studies 

in the New York Bight (Sadove and Morreale 

1990; Gerle and DiGiovanni 1998). A similar 

rate of 6% entanglement in marine debris 

of stranded turtles was observed in Florida 

from 1989–1994 (Bjorndal and Bolten 1995). 

A study involving observations of more than 

1,500 free-swimming sea turtles worldwide 

(Bjorndal and Bolton 1995) reported the 

percentage of entanglements of all sea turtles 

as 5%, similar to the above rates during the 

same time period.

More recently, the Florida Entanglement 

Working Group reported 1,217 sea turtles that 

were entangled or had ingested marine debris 

from 1997–2009 (Bassos-Hull and Powell 

2012). This number does not parse out the 

percentage of sea turtles just entangled and 

includes entanglements in active fishing gear, 

such as crab pot lines. However, 13.4% of those 

entangled or that had ingested marine debris 

were categorized as “other” types of debris.

Figure 9. Biologists work 

to free a green sea turtle 

entangled in a discarded 

fishing net in the Tumon Bay 

Preserve in Guam.

Credit: David Burdick/Marine Photobank
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

OTHER MARINE SPECIES

There is reference to numerous reports 

worldwide of other marine species becoming 

“entangled” in marine debris, including: fish, 

invertebrates, and corals. It appears that most 

of the reports on fish species (66 from SCBD 

2012) and most of the crustaceans may be 

victims of “ghost fishing,” where nets continue 

to “fish” if lost at sea. In the case of corals, nets 

or lines that snag on the colony can eventually 

cause destruction when wave action pulls 

the debris back and forth (Donohue et al. 

2001; Yoshikawa and Asoh 2004). Benthic 

invertebrates such as crabs and starfish may 

become entangled after walking through 

netting, lost traps, or debris that has settled 

to the sea floor, possibly scavenging those 

animals that have already become entangled 

(Good et al. 2007). 

The earliest report of any fish found 

entangled in marine debris was from Gudger 

(1928) of a mackerel (Scomber scombrus) 

caught off Block Island near Connecticut, 

which was wrapped with a rubber band. 

Gudger and Hoffman (1931) also reported 

a shortfin mako (Isurus oxyrhincus) found 

dead with a rubber car tire around its neck in 

Cuba. Another shortfin mako in California 

was reported by Wegner and Cartamil (2012) 

entangled in a natural fiber rope resulting in 

scoliosis, abrasions, and undernourishment. 

Bird (1978) reported entanglement of three 

species of sharks by packing straps and a 

salmon shark (Lamna ditropis) was found in 

gillnet fragments in the North Pacific (Jones 

and Ferrero 1985). In a study from 1998–2005, 

smalltooth sawfish (Pristis pectinata) were 

found entangled in PVC pipe, monofilament 

line, elastic bands, and netting in Florida 

(Seitz and Poulakis 2006). The long snout 

with exposed teeth of this species could make 

it vulnerable to any debris that could easily 

attach to the teeth. Wallace (1985) notes 

manta rays (Manta spp.) being entangled in 

monofilament line, potentially because of the 

wing-like body and trailing spine that could 

easily catch on floating debris. Monofilament 

line was also observed encircling a blacknose 

shark in North Carolina causing a deformation 

of the spine (Schwartz 1984). Laist (1997) also 

lists an unidentified skate and dogfish (Squalus 

acanthius) as entangled in gillnet in Cape 

Cod Bay. Undoubtedly, sharks are entangled 

in marine debris more often than is reported 

in the literature. However, given the huge 

numbers of unentangled fish that are caught, 

entanglement of fish in debris other than 

ALDFG is likely insignificant. 

Invertebrates are not well represented in 

the literature as entangled in marine debris, 

and often there is only a slight mention 

of the impact to these species (Stevenson 

2011; SCBD 2012). However, the problem 

of entanglement in debris appears to be far 

greater than what is reported based on a 

few studies. Laist (1997) lists four species of 

crustaceans (three crab, one lobster) entangled 

in lost gillnets mostly from the North Pacific. 

Chiappone et al. (2002) detailed the effect of 

marine debris on sessile invertebrates in the 

Florida Keys. Taxa included were gorgonians, 

fire coral, sponges, and zoanthids. Nearly 68% 

of the entanglements of these species were due 

to monofilament line and hooks. In Hawaii, 

14 species of invertebrates were affected by 

net entanglement (Donohue et al. 2001). 

These taxa include sipunculids, arthropods, 

echinoderm, and platyhelminths. Good et al. 

(2007) recorded 27 species of invertebrates 

entangled in netting in Puget Sound. Likewise 

in Puget Sound, Gilardi et al. (2010) recorded 

10 species of invertebrates entangled in 

experimental nets. Both sources expressed 

concern over the number of Dungeness crabs 

(Cancer magister) entangled, as this species is 

of commercial interest.

Figure 10. A dead tiger shark (and other fish) entangled in derelict nets in Florida. 

Credit: Elaine Blum

15
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

CONCLUSIONS

The impacts from entanglement of marine 

species in marine debris are clearly profound, 

and in many cases entanglements appear to 

be increasing despite efforts over four decades 

to reduce the threat. This review reported 

entanglement in marine debris in the U.S. of 

44 species of sea birds, 13 species of cetaceans, 

11 species of pinnipeds, 31 species/taxa of 

invertebrates, 6 species of sea turtles, and a 

few fish species. Many of the fish species were 

excluded due to reports of “ghost fishing,” and 

a more comprehensive review of this work is 

available in another topic paper (Ghost fishing 

Topic Paper). The majority of cases revolve 

around entanglement in fishing gear and 

ALDFG and to a lesser degree other plastic 

debris. 

Available entanglement rates are at best 

minimum estimates, and the methods to 

derive these estimates are at times quite 

different depending on the source of the data 

(e.g., rates based on strandings vs. rescue/

rehabilitation records vs. observations of 

live animals seen carrying debris). For 

instance, entanglement-related mortality 

rates of Hawaiian monk seals have partially 

accounted for at-sea entanglement deaths 

(Henderson 2001; Boland and Donohue 

2003), but entanglement rates for northern 

fur seals have not considered this source 

of mortality. Further, the extent to which 

entanglements actually hinder a population 

is still not understood for most species. As 

stated previously, there is some evidence to 

suggest that a decline in the northern fur seal 

population was due in part to entanglement 

in marine debris (Fowler 2000). For other 

pinniped species such as the Hawaiian 

monk seal, entanglement in marine debris 

is a clear contributor to its ongoing decline 

and appears to be more important for some 

breeding groups than others. Entanglement 

rates in marine debris for pinnipeds and sea 

turtles appear to be more accurate than for 

cetaceans; for sea birds, data and rates appear 

to more intermediate. Impact estimates may 

be inferred by observing seals at known 

rookeries (Henderson 2001; Donohue and 

Foley 2007; NMFS 2007) or well-known 

resident populations, such as the bottlenose 

dolphin population in Sarasota Bay, Florida. 

As mentioned previously, without an accurate 

assessment of at-sea mortality caused by 

entanglement in debris, it is difficult to 

generate overall entanglement-related 

mortality rates. For other marine species, such 

as cetaceans, entanglement rates in marine 

debris are lacking mainly because of the 

limited efforts to distinguish entanglement 

in active fishing gear vs. marine debris 

and because most data are from stranding 

records represent an unknown proportion of 

entangled animals or total annual mortality. 

Minimum estimates of population size are 

given in NMFS Stock Assessment Reports 

based on aerial and ship-board surveys, 

but some of these surveys are outdated. 

Entanglement rates for other cetaceans, 

such as the bottlenose dolphin, also rely on 

stranded animals and observations of live 

free-swimming entangled animals to obtain 

an incidence of entanglement. Strandings 

provide a minimum estimate of entanglement 

incidents, as not all dead animals at-sea make 

it to shore, and not all live entangled animals 

are observed. Further, assigning individual 

entangled cetaceans to a discrete population 

is often difficult since many species have 

complex population structures. 

We may never know the true extent to 

which marine debris entanglements affect 

most populations of marine species. For 

some species with low population levels such 

as the Hawaiian monk seal, development 

of minimum entanglement estimates are 

possible; however, for all marine species, the 

principal difficulty lies in the limited ability 

to detect entangled animals at sea, especially 

pelagic deep diving species of cetaceans that 

spend little time at the surface. Therefore, the 

best available data for most species are from 

strandings of dead animals for cetaceans 

and sea turtles, counts and sightings of live 

entangled pinnipeds and sea birds at rookeries, 

and counts of dead animals in ghost gillnets 

and traps for fish and crustacean species. In 

the same context, the number of animals that 

survive entanglements in marine debris is 

largely unknown, but may have significant 

effects even for survivors. That is, some 

animals sustain debilitating injuries, such as 

lost limbs or deep cuts that can reduce their 

ability to swim, feed, and reproduce. The 

extent to which such injuries might affect 

populations as a whole is not known. There 

is evidence to suggest that many individuals 

shed their entangling debris, but even then, 

the lingering effects of entanglement can incur 

life-long physical problems that may shorten 

life spans. For endangered species this could 

be as harmful as mortality itself. This makes 

understanding the real effects of entanglement 

at a population level more difficult. In other 

words, just because we see individuals freeswimming with entanglement scars, doesn’t 

mean that the individuals are returning to 

normalcy without a negative effect on the 

population as a whole. Both mortality and 

morbidity should be included in the data when 

describing the effects of entanglement rates on 

populations.

The type of marine debris causing 

entanglement varied at times among species. 

Fur seals were generally entangled in net 

fragments, but Steller sea lions showed a 

propensity of entanglement in packing 

straps. Dolphins, sea turtles, and sea birds 

were commonly entangled in monofilament 

line. Large baleen whales were entangled 

in nondescript lines, making it difficult to 

ascertain if the entangling fishing gear was 

active or derelict fishing gear. Regardless, 

fishing gear composed of rope or netting is 

assumed to be the most common source. 

A few species are susceptible to marine 

debris in areas where their habitat overlaps 

with high concentrations of marine debris, 

such as the North Pacific Gyre and the 

northern fur seal and the NWHI and 

Hawaiian monk seals. Macfadyen et al. (2009) 

From reports in the 

United States, at least 

115 marine species 

are impacted by 

entanglement, including 

mammals, turtles, birds, 

fish and crabs. World wide, 

the number tops 200.

16
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

and others provide good detail of these 

convergence zones in the Pacific and Atlantic 

Oceans. These zones also may affect humpback 

whales and sea turtles.

While in some regions of the world it may 

appear that land-based and surface water 

debris is declining (Gregory 2009), natural 

disasters such as hurricanes and tsunamis 

have potentially added to the amount of 

entangling debris in the marine environment 

(SCBD 2012). Further, as the coastal 

population continues to grow, particularly 

in the southeastern U.S., the potential for 

increased levels of land-based marine debris 

could occur. Numerous local, state, regional, 

and national programs for the removal of 

marine debris have occurred and continue to 

be implemented, yet entanglement of marine 

species in marine debris is still a significant 

threat to many species. For some endangered 

species, like the Hawaiian monk seal and 

northern fur seal, this threat could tip the 

balance of survival of the species. 

Laist (1997) and Laist et al. (1999) 

suggested numerous ways to address the 

problem of entanglement in marine debris. 

These suggestions included: documenting and 

monitoring entanglement rates; disentangle 

individuals entangled; recover gear that is 

lost or abandoned, encourage fishermen to 

report lost or abandoned gear; keep marine 

debris on board if brought up during fishing 

operations; incentives for fishermen to report 

and return marine debris; provide reception 

facilities at port; and develop new technology 

for fishing gear, such as float releases to aid 

in its retrieval if gear is lost, and degradable 

fishing gear when applicable. Since this report 

over 15 years ago, the suggestions by other 

authors have changed very little. Macfadyen et 

al. (2009) detail numerous ways of preventing 

ALDFG, including: gear marking; on-board 

technology to detect ALDFG, such as GPS or 

sea bed mapping technology; inspection of 

gear by port authorities; onshore collection/

reception; payment incentives for old/retrieved 

gear; reduction in fishing effort; spatial 

management; biodegradable nets and pots and 

other technology, like adding barium sulfate 

to nets to reflect sound, better reporting of lost 

gear such as modeled by the California Lost 

Fishing Gear Recovery Project and the SeaDoc 

Society; gear recovery; awareness programs; 

and dedicated efforts to remove derelict fishing 

gear from areas of accumulation . While 

these mitigation efforts address fishing gear, 

they do not necessarily address all sources of 

marine debris, such as land-based plastics. A 

workshop to address the ability to distinguish 

between active fishing gear and ALDFG on 

entangled animals is highly recommended, 

and has been discussed recently as a research 

priority, especially for cetaceans (IWC 2013).

The SCBD (2012) addressed strategies to 

mitigate the impacts of marine debris, not 

only for ALDFG, but also for marine debris in 

general. They outline numerous institutional 

strategies at global, regional, and national 

levels. While they emphasize that many 

waste management and recycling efforts have 

been unsuccessful, there have been cases 

of successful implementation of mitigation 

measures. One of these, “reuse and reduce,” 

includes: reducing the amount of plastics in 

packaging, eco-labels for consumers to make 

better decisions on use and disposal practices, 

green procurement, biodegradable products, 

and voluntary actions at the corporate and 

local level to develop such programs. As with 

Laist (1997) and Macfadyen et al. (2009), 

the SCBD (2012) recognized the value of 

incentives for collection and recycling, as 

numerous countries, including the U.S., are 

very successful of this reduction in waste. 

Building awareness within the community 

and among businesses has also been shown to 

create a positive initiative (Laist et al. 1999).

It was obvious from the reviewed literature 

that there are many gaps and difficulties in 

assessing entanglement in marine debris. 

Laist (1997) outlined factors that complicate 

this process (Table 1). For the current review, 

the most striking difficulty came from the 

inconsistency of determining what is marine 

debris and what is not. The SCBD (2012) 

defines marine debris as “any persistent, 

manufactured or processed solid material 

discarded, disposed of, or abandoned in 

the marine and coastal environment.” This 

includes ALDFG. Some studies specifically 

list ALDFG as marine debris, while others do 

not distinguish between ALDFG and active 

gear, especially with North Atlantic right 

whale and other baleen whale studies. Thus, 

entanglement rates in marine debris may be 

inflated if one considers all entanglements, 

including those in active fishing gear, to be 

caused by marine debris. Similarly, the term 

“ghost fishing” is used to describe gear that 

is lost or discarded that continues to catch 

target and non-target species. There is a need 

to clearly define the terms above to adequately 

describe the rate of entanglement for many 

species.

It also became apparent that the reporting 

of marine debris in the literature is not as 

Most entanglement 

reports in the United States 

involve northern fur seals, 

Hawaiian monk seals, and 

sea turtles.

17
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

extensive as it could be and, thus, estimates 

of entanglement in marine debris are likely 

underestimated. Many institutions fail to 

publish these accounts because, many times, 

they are only of single individuals (Simmonds 

2012).

Stranding programs also do not have 

clear protocols for distinguishing marine 

debris from active fishing gear and recording 

incidents of entanglement in debris vs active 

fishing gear separately. Numerous reports 

of marine debris entanglement involving 

odd items or particularly well-documented 

cases can be found in local media reports or 

newspaper articles. For instance, a bottlenose 

dolphin was disentangled from a rubber 

gasket that was around its neck in 2008 (http://

savannahnow.com/mary-landers/2008-07-02/

dolphin-freed-trashy-noose#.Uop_xfmsi-0) 

and another was found entangled in a pair of 

swimming trunks (http://www.brookfieldzoo.

org/pgpages/pagegen.273.aspx). Further, many 

institutions hold large, underused data sets 

that include information on anthropogenic 

sources of entanglement and mortality, but 

these data sets may not classify or report 

entanglement events linked directly to marine 

debris. For instance, the U.S. National Marine 

Mammal Stranding Database administered 

by NOAA/NMFS contains basic information 

regarding every marine mammal that strands 

in the U.S. This database has a place to specify 

whether the animal was involved with human 

interaction or not, but only allows the person 

entering data to choose from boat strike, 

fishery interaction, shot, or other form of 

human interaction. If fishery interaction is 

checked, the data entry person can choose 

whether gear was present or not. However, 

there is no category for marine debris and thus 

trying to determine if the entanglement was 

truly from marine debris is difficult and not 

easily searchable. It is likely that many other 

federal wildlife databases are similar and do 

not specify marine debris in their outputs. 

There is a need across all government agencies 

that input wildlife data to include marine 

debris as an entanglement source. It may be 

helpful to create a centralized database where 

marine debris entanglement reports could 

be sent, even if the report involved a single 

animal, and be easily searched.

Finally, there are likely other species from 

other regions of the U.S. that suffer injury or 

death from being entangled in marine debris, 

but are not widely recognized or reported. 

Most of the literature describes entanglement 

of marine species from Alaska, California, 

Puget Sound, Florida, and in the case of baleen 

whales, the New England region, though this 

may simply reflect an absence of occurrence. 

The Mid-Atlantic and Gulf of Mexico regions 

of the U.S. are lacking in reports of marine 

debris entanglement. Similarly, reports of 

marine debris entanglement on sea birds and 

sea turtles are limited to a few papers, and 

reports on polar bears and walruses are nonexistent, possibly due to an arctic habitat that 

is virtually devoid of commercial fishing and 

is an area of low sources of marine debris.

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Common Name Reference

American Lobster Laist 1997

Brown box crab Good et al. 2007

Butter clam Good et al. 2007

Dungeness crab Good et al. 2007, Gilardi et al. 2010

Fire coral Chiappone et al. 2002

Giant barnacle Laist 1997, Good et al. 2007

Giant Pacfic chiton Good et al. 2007

Golfball crab Good et al. 2007, Gilardi et al. 2010

Gorgonians Chiappone et al. 2002

Granular claw crab Good et al. 2007

Green sea urchin Good et al. 2007, Gilardi et al. 2010

Heart crab Good et al. 2007

Helmet crab Good et al. 2007

Hermit crab Gilardi et al. 2010

Kelp crab Laist 1997, Good et al. 2007

Leafy hornmouth Good et al. 2007

Longhorn decorator crab Good et al. 2007, Gilardi et al. 2010

Lyre crab Good et al. 2007

Northern cancer crab Laist 1997

Northern kelp crab Good et al. 2007, Gilardi et al. 2010

Nuttall’s cockle Good et al. 2007

Oregon triton Good et al. 2007

Pacific littleneck clam Good et al. 2007

Pacific octopus Good et al. 2007

Puget sound king crab Good et al. 2007, Gilardi et al. 2010

Red fur crab Good et al. 2007

Red rock crab Laist 1997, Good et al. 2007, Gilardi et al. 2010

Red sea urchin Gilardi et al. 2010

Smooth pink scallop Good et al. 2007

Spiny pink star Good et al. 2007

Sponges Chiappone et al. 2002

Sunflower star Good et al. 2007

Tanner crab Good et al. 2007

Zoanthids Chiappone et al. 2002

Table 1. Entanglements of invertebrates in marine debris in the U.S. 

APPENDIX

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2014 MARINE DEBRIS ENTANGLEMENT REPORT 

Common Name Reference

American coot Moore et al. 2009

Auklet Jones and Ferrero 1985, Laist 1997

Black skimmer Laist 1997

Black-crowned night heron Moore et al. 2009

Black-footed albatross Laist 1997, Moore et al. 2009

Brandt’s cormorant Good et al. 2007, Moore et al. 2009

Brown pelican Laist 1997, Moore et al. 2009

California gull Moore et al. 2009

Caspian tern Moore et al. 2009

Clark’s grebe Moore et al. 2009

Common eider Moore et al. 2009

Common loon Good et al. 2007, Moore et al. 2009

Common merganser Good et al. 2007, Moore et al. 2009

Common murre Jones and Ferrero 1985, Laist 1997

Double crested cormorant Good et al. 2007, Moore et al. 2009

Glaucus winged gull Moore et al. 2009

Great black-backed winged gull Laist 1997

Great blue heron Moore et al. 2009

Great egret Moore et al. 2009

Herman’s gull Moore et al. 2009

Herring gull Harris et al. 2006

Horned puffin Jones and Ferrero 1985, Laist 1997

Larus spp. Gulls Good et al. 2007, Moore et al. 2009

Laughing gull Laist 1997

Laysan albatross Degange and Newby 1980, Laist 1997

Lesser scaup Moore et al. 2009

Masked booby Conant 1984, Laist 1997

Nothern fulmar Degange and Newby 1980, Laist 1997, Moore et al. 2009

Pacific loon Moore et al. 2009

Pelagic cormorant Good et al. 2007, Moore et al. 2009

Pied bill grebe Moore et al. 2009

Ringed billed gull Moore et al. 2009

Rock dove Moore et al. 2009

Ruddy turnstone Laist 1997

Scoty tern Laist 1997

Short-tailed shearwater Degange and Newby 1980, Laist 1997, Moore et al. 2009

Snowy egert Moore et al. 2009

Sooty sherwater Laist 1997, Moore et al. 2009

Surf scoter Moore et al. 2009

Tufted puffin Degange and Newby 1980, Jones and Ferrero 1985, Laist 1997

West x Glaucus winged gull hybrid Moore et al. 2009

Western grebe Laist 1997, Good et al. 2007, Moore et al. 2009

Western gull Laist 1997, Moore et al. 2009

White pelican Laist 1997, Moore et al. 2009

White winged scoter Harris et al. 2006

Table 2. Entanglements of sea birds in marine debris in the U.S.

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2014 MARINE DEBRIS ENTANGLEMENT REPORT 

Common Name Reference

Atlantic harbor seal Good et al. 2007

Bottlenose dolphin Wells and Scott 1994, Mann et al. 1995, Wells et al. 1998, McFee and 

Hopkins-Murphy 2002, McFee et al. 2007, Barco et al. 2010, Powell and 

Wells 2011, Bassos-Hull and Powell 2012, Lelis, 2012, Bassos-Hull 2013, 

Stolen et al. 2013

Bowhead whale Philo et al. 1992

California sea lion Laist 1997, Good et al. 2007, Gilardi et al. 2010

Dall’s porpoise Degange and Newby 1980

Eastern gray whale Laist 1997

Florida manatee O’Shea et al. 1985, Beck and Barros 1991, Nill 1998, Spellman 1999, 

Bassos-Hull and Powell 2012, Butterworth 2012, Bassos-Hull 2013

Gray seal Good et al. 2007

Guadalupe fur seal Good et al. 2007

Harbor porpoise Laist 1997

Harp seal Laist 1997, Good et al. 2007

Hawaiian monk seal Good et al. 2007

Hooded seal Good et al. 2007, Gilardi et al. 2010

Humpback whale Good et al. 2007

Minke whale Good et al. 2007, Gilardi et al. 2010

North Atlantic right whale Good et al. 2007

Northern elephant seal Good et al. 2007, Gilardi et al. 2010

Northern fur seal Fowler 1982, 1985, 1987, Laist 1997, Good et al. 2007

Pacific harbor seal Good et al. 2007

Sea otter Degange and Newby 1980, Moore et al. 2009

Sperm whale Moore et al. 2009

Steller sea lion Good et al. 2007, Gilardi et al. 2010

Table 3. Entanglements of marine mammals in marine debris in the U.S.

27
2014 MARINE DEBRIS ENTANGLEMENT REPORT 

Common Name Reference

Blacknose shark Schwartz 1984

Dogfish Laist 1997

Green sea turtle Balazs 1980, 1982b, 1985, Hildebrand 1980, Anon 1981, Mooney and 

Knaughton 1981, Henderson 1984, Plotkin and Amos 1990, Sadove and 

Morreale 1990, Teas and Witzell 1995, Gerle and DiGiovanni 1998

Hawkbill sea turtle Balazs 1978,1985, Hildebrand 1980, Broadrick 1982, Fletcher 1982, 

Wolf 1982, Plotkin and Amos 1990, Teas and Witzell 1995

Kemp’s ridley sea turtle Plotkin and Amos 1990, Sadove and Morreale 1990, Duronslet et al. 

1991, Teas and Witzell 1995, Gerle and DiGiovanni 1998

Leatherback sea turtle Sadove and Smith 1981, Plotkin and Amos 1990, Sadove and Morreale 

1990, Teas and Witzell 1995, Gerle and DiGiovanni 1998

Loggerhead sea turtle Balazs 1985, Plotkin and Amos 1990, Sadove and Morreale 1990, 

Bjorndal and Bolten 1995, Teas and Witzell 1995, Gerle and DiGiovanni 

1998

Mackerel Gudger 1928

Manta ray Wallace 1985

Olive ridley sea turtle Balazs 1982a,b, Afelin and Puleloa 1992, Teas and Witzell 1995

Salmon shark Jones and Ferrero 1985

Shortfin mako shark Gudger and Hoffman 1931, Wegner and Cartamil 2012

Skate, unidentified Laist 1997

Smalltooth sawfish Seitz and Poulakis 2006

Table 4. Entanglements of sea turtles and other species in marine debris in the U.S.

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2014 MARINE DEBRIS ENTANGLEMENT REPORT 

Penny Pritzker

United States Secretary of Commerce 

Dr. Kathryn D. Sullivan

Under Secretary of Commerce for Oceans and Atmosphere

Dr. Holly A. Bamford

Assistant Administrator, National Ocean Service