Pol 195 & Pol 192
17 March 2016
Sink the Nets: A Look at the Negative Impacts of Drift Gillnet Fishing off the West Coast
The health of the marine ecosystem has substantially deteriorated as a result of extensive
human activity in the ocean. While it is impossible to precisely measure the extent of human
impact on the ocean, research has shown that marine wildlife and habitat is being depleted at an
alarming rate. The biodiversity of marine wildlife is vital in sustaining a healthy marine
ecosystem. The United Nations Convention on Biological Diversity defines biodiversity as, “The
variability among living organisms from all sources… and the ecological complexes of which
they are part: this includes diversity within species, between species and of ecosystems” (UNEP
2015). All marine species are interconnected and perform unique duties that are essential to the
basic function of the ocean’s complex ecosystem. Moreover, the overall health of the marine
ecosystem is directly linked to the health of human beings.
The ocean is fundamental to life on earth, underpinning economies and businesses, and
sustaining the livelihoods and wellbeing of billions of people worldwide. Furthermore,
the ocean provides countless resources that humans heavily rely on, including food, raw
materials, energy, medicines and other products (WWF et al 2015).
In addition to the tangible resources the ocean provides, healthy oceans are necessary to
sustain all life on earth. The ocean regulates the global climate, produces half of the oxygen on
the planet, and mitigates the effects of climate change by absorbing one third of anthropogenic
carbon dioxide emissions (IPCC 2013). However, despite the critical importance of maintaining
a healthy marine ecosystem, humans continue to take actions that are harming the ocean.
Unsustainable human activity that is causing the degradation of the marine ecosystem includes,
but is not limited to: extractive industries, coastal development, pollution, GHG emissions, and
overfishing (WWF et al 2015).
Overfishing is one of the primary causes in the drastic loss of marine biodiversity in the
ocean. As the human population has grown exponentially, the demand for seafood has led to a
massive commercial fishing industry that operates all over the world. The commercial fishing
industry, including processing, packing, transport, and retail, employs approximately 10-12% of
the global population (FAO 2014). Along with the many millions of people who rely on
commercial fishing for their livelihood, even greater amounts rely on it to provide an essential
source of food. It is estimated that fisheries supply approximately 15% of the world’s protein
(UNEP 2015). As commercial fishing has expanded and innovated to meet this growing need,
fish and other marine species have been drastically depleted. Today 29% of the world’s fish
stocks have been overfished, and 61% of the stocks have been fully exploited, with no ability to
produce more fish (WWF et al 2015). Predictably, along with diminishing the fish stocks,
overfishing is also responsible for the reduction of other marine wildlife populations. According
to the Living Planet Index (LPI), a report released every two years that measures trends in
wildlife populations, marine populations have declined 49% between 1970 and 2012 (WWF et al
2015). Furthermore, with the global population projected to increase beyond 9 billion people by
2050, the demand for ocean resources will persist and intensify, placing continued pressure on
marine ecosystems (WWF et al 2015).
One of the principal reasons marine biodiversity is being threatened by commercial
fishing is due to high rates bycatch. The National Oceanic and Atmospheric Organization
(NOAA), the agency tasked with regulating the fishing industry in the United States, defines
bycatch as: “animals caught by fishing that were not the intended target of the fishing activity”
(NOAA 2015). In order to meet the growing demand for seafood in an increasingly depleted
ocean, the commercial fishery has had to innovate. Many types of modern fishing technologies
make it easier to target the desired fish stock with less work involved. However, many of these
non-selective methods also lead to the catch of many other marine species, which are referred to
as bycatch. Some of the most common fishing methods that yield a large amount of bycatch
include: longlines, trawling and gillnets (WWF et al 2015). As the use of these methods has
increased, marine biodiversity has decreased. Today, global bycatch levels are estimated at 7.3
million tons (WWF et al 2015). That is, seafood is being provided at the cost of 7.3 million tons
of marine wildlife being harmed or killed in the process. Despite regulations that have been
imposed by several countries, as well as the creation hundreds of Marine Protected Areas
(MPA), unsustainable fishing continues to persist.
In order to gauge the effects of fishing on marine biodiversity, this paper will examine the
California drift gillnet fishery. While California is viewed as a leader in sustainability,
California’s drift gillnet fishery has prompted considerable amounts of criticism from individuals
and environmental organizations. In a report by Oceana released in 2014 California’s drift gillnet
fishery was named as one of the 9 “Dirtiest Fisheries” in the United States, based on data
collected by the National Marine Fisheries Service (Keledjian et al 2014). The California drift
gillnet fishery operates in the area between 3 and 200 miles off the coast, in the United States
EEZ, catching primarily swordfish and shark. This fishery uses a type of gear known as drift
gillnets, walls made up of monofilament or monofilament nylon, up to one mile long and one
hundred feet deep that are invisible to marine wildlife. The size of the mesh is dependent on the
species the fishery is targeting (NOAA 2015). Fish and other marine species are caught in the
drift gillnet by swimming into it and becoming entangled. These nets hang in the water for a
period of time, usually dawn until dusk, until they are drawn up. Currently the California drift
gillnet fishery consists of twenty vessels that operate with a limited entry permit between the
months of May and January (NOAA 2015). This fishery is co-managed by NOAA, the Pacific
Fishery Management Council (PFMC) and the state of California.
Figure 1. Drift Gillnet Vessel
The California drift gillnet fishery has been under scrutiny due to the high amount of
bycatch that is being produced. While the size of the mesh is supposed to target a specific
species, a broad range of marine wildlife is being caught along with the targeted species. Some
of the marine wildlife that is commonly caught by drift gillnets in California includes: whales,
dolphins, sharks, rays, sea lions, elephant seals, turtles, seabirds and several species of fish.
Depending on the gillnet mesh size, animals can become entangled around their necks,
mouths, and flippers. Entanglement can prevent proper feeding, constrict growth, or
cause infection after many months. Marine mammals… entangled in drift gillnets can
drag gear for miles as they migrate and forage, leading to extreme fatigue (NOAA 2015).
Despite the limited number of vessels, the California drift gillnet fishery kills more
whales and dolphins than any other observed fishery in California, Oregon, Washington and
Alaska combined according to a report released by Turtle Island Restoration Network (Karpa et
al 2015). Moreover, a portion of the marine species harmed by these nets are threatened or
Figure 2. The width of drift gillnets span the size of the Golden Gate Strait
The excessive bycatch rates of this fishery have led to regulations imposed by the PFMC
in an attempt to curb the loss of marine wildlife. This includes seasonal closure of areas within
the fishing area known as “time/area closures” (NOAA 2015). For instance, in 2001 the Pacific
Leatherback Conservation Area was established in which drift gillnet fishing is prohibited from
the months of August to November. Pacific leatherback turtles have experienced significant
decline in population and are globally listed on the Endangered Species Act (ESA) as
endangered (NOAA 2015). In addition to time/area closures, drift gillnets in California are
required to be equipped with an acoustic device known as a “pinger” to deter marine mammals
from swimming into the nets (NOAA 2015). Furthermore, in 2010 two sperm whales, which are
listed as endangered under the Endangered Species Act (ESA), were found entangled in drift
gillnets. One of the whales died and the other whale was released alive, but predicted to die due
to injuries incurred from the nets. This prompted the NMFS to enact a temporary emergency
regulation that would shut down the entire fishery for the remainder of the 2010 season if another
sperm whale was harmed or killed (Clarke 2014).
Figure 3. Hammerhead shark in drift gillnet (http://www.worldwildlife.org/species/shark)
The most recent attempt to reduce bycatch rates took place in 2015 when the PFMC
voted to adopt new regulations. These regulations included implementing two-year rolling hard
caps on the number “high priority protected species” killed or injured by drift gillnets. These
“high priority protected species include: fin whales, humpback whales, short-fin pilot whales,
sperm whales, leatherback sea turtles, loggerhead sea turtles, olive ridley sea turtles, green turtles
and bottlenose dolphins. When the hard caps established by the PFMC are reached, the fishery
will be mandated to close for the season (PMFC 2015). However, these hard caps are based on
“observed mortality/injury”, and only 30% of the vessels are actually observed. This low level of
observance makes it almost impossible to accurately monitor bycatch rates. Moreover, these hard
caps do not include the take of marine mammals that are not considered “high priority protected
The negative impacts of drift gillnets have caused several countries and states to ban
them entirely. In 1991 the United Nations banned drift gillnet fishing on the high seas
(Associated Press 1991). Furthermore, in 2009 the Oregon Fish and Wildlife Commission made
the decision to discontinue issuing permits for drift gillnet gear in Oregon (Amman 2009). Drift
gillnet fishing was also banned in Washington, making California the only west coast state to
issue permits for this type of fishing gear (Karpa et al 2016).
In an attempt to follow suit, lawmakers in California also attempted to ban drift gillnet
fishing. In 2014 California State Assembly member Paul Fong (D-San Jose) introduced
Assembly Bill 2019, legislation to ban drift gillnet fishing off of the California Coast. Fong
stated that, “California has been a national leader in environmental and conservation efforts. The
fact that California still permits the use of these deadly drift gillnets while other states on the
western coast have banned the use is shameful” (CA State Assembly Press Release 2014).
Despite public support for this bill, it was killed in the Assembly Committee on Water, Parks and
Wildlife with a 7-6 vote (California Legislative Information). This bill was defeated with the
help of lobbyists who were advocating on behalf of the drift gillnet fishery. The fisheries argued
that bycatch rates had gone down, and shutting them down would lead people to import
swordfish from other, less sustainable fisheries (Mazza 2014). Since this legislation was defeated
conflict between the drift gillnet fisheries and environmental advocates has persisted.
The objective of this research is to determine the impact of drift gillnet fishing on marine
wildlife and use these findings to shape policy options that protect the marine ecosystem, while
keeping in mind the fishermen who depend on this fishery for their livelihood. Due to the past
research done on this subject and the nature of drift gillnets it is likely that the California drift
gillnet fishery has a negative impact on marine wildlife. In order to test this hypothesis it is
necessary to assess how much and what type of bycatch the fleet yields. However, due to the
nature of fishing and limited resources, it is exceptionally difficult to accurately monitor what the
vessels are catching.
In an attempt to regulate and monitor the fishery NOAA established the National
Observer Program (NOP) in 1990. This program was established to “document the incidental
take of marine mammals, sea turtles, seabirds, target and non-target fish species” (NOAA 2015).
In accordance with the program, independent contracted observers are placed onboard select drift
gillnet fishing vessels to record the amount of bycatch yielded by that vessel. Since 1991, NOAA
has released yearly reports that document the observed catch for that fishing season. However,
currently, only 30% of the total vessels in the California drift gillnet fishery are being observed.
Despite the flaws with the NOP, it is the only source that provides detailed data on the total catch
and bycatch produced by the fishery.
NOP reports for the last ten years, beginning with the 2005-2006 fishing season and
ending with the 2014-2015 fishing season will be used. By gathering ten years of information the
changes and trends over time can be analyzed. This information will highlight if the fishery is
getting worse or better overtime and in what ways. Moreover, by looking at the most recent data,
the current state of the fishery can be analyzed in order to shape relevant and informed policy
The NOP yearly reports list the total of every species that was caught, number kept,
number returned alive, number returned dead, number returned unknown, number damaged and
catch per 100 sets. The unit of analysis provided in the NOP reports is “number of animals”,
therefore this unit of analysis will be used throughout the paper. Because not all vessels were
observed, NOAA estimates the totals based on the 30% of vessels that were occupied by an
observer. Because of this discrepancy, the totals provided by NOAA may be either over
estimated or underestimated. The totals provided on these sheets will be converted into a
working excel spreadsheet that is categorized by year and type of species.
To analyze how much total bycatch is being produced, the total number of animals kept is
subtracted from the number of animals caught each year. This will produce the number of
animals that were not kept (bycatch) every year. The amount of bycatch will then be converted
into a percentage based on the total amount caught that year. After totaling the percentage of
bycatch for every year, all the yearly percentages will be calculated into an average over ten
years. This information will represent how much bycatch is being produced in comparison to
how much is being kept both on a yearly level and a long-term level.
Lastly, in order to look at the specific species that are being caught, the number of
individual species being caught, killed, or damaged every year will be calculated. This
information will be used to see what species are most likely and least likely to be caught. The
ten-year totals of all of these categories will be calculated in order to see any trends over time in
the type of animals that are being caught and whether or not they were discarded. In addition all
of the animals that were killed, returned injured or returned alive will be categorized as
endangered or not, in order to gauge how many protected species are being caught. Using this
information I will gauge how much of an impact the California drift gillnet fishery has on these
After calculating the total amount of every animal that was kept and every animal that
was discarded by the fishery over the past ten years, I found that more animals were discarded
than were kept. From 2005 to 2015 the fishery caught a total of 28,447 various species of marine
wildlife. Of these 11,115 were kept and a total of 17,362 animals were discarded either dead,
alive, damaged or unknown.
Figure 4. Averages of the total kept and discarded animals (2005-2015)
When looking at trends in the fishery over the past ten years, I found that the size of the
fishery as a whole has decreased substantially. In 2005 the fishery caught a total of 4,650
animals, and in 2015 the fishery only yielded a total of 778 animals. Along with the decrease in
overall catch, I found that bycatch has also gone down significantly. In the 2005 fishing season,
the fishery discarded 67% of their entire catch, while in 2015 they discarded 30% of their total
catch. However, it is important to note that 30% is still a high bycatch rate, especially for such a
small scale fishing operation.
Figure 5. Total animals kept and discarded (2005-2015)
After calculating the total kept and discarded rates of this fishery over ten years, I looked
at what type of animals were being caught. The animal that was by far caught the most is a
species of fish known called the common mola, otherwise known as the ocean sunfish. Over ten
years a total of 13,169 ocean sunfish were caught and discarded. Ocean sunfish are the heaviest
of all the bony fish, with large specimens reaching 14 feet vertically and 10 feet horizontally and
weighing nearly 5,000 pounds (National Geographic 2015). Because these fish are not sold for
human consumption, all 13,169 ocean sunfish that were caught were discarded.
Figure 6. Ocean sunfish photographed near a diver for scale
Photo Credit: https://adlayasanimals.files.wordpress.com/2013/10/ocean-sunfish.jpg
Sharks were the second most common animals to be caught by this fishery. A total of
4,551 various shark species were caught over the last ten years. However, unlike ocean sunfish,
some sharks are sold for human consumption, so not all of the sharks were bycatch. Of the 4,551
sharks that were caught, 1,555 were discarded. Moreover, of the sharks that were caught, four of
them were a species known as the megamouth shark. This rare species of shark has only been
sighted by humans a total of 63 times, making it one of the least understood and rarest shark
species known to man (Martins et al 2013). Therefore, while four may seem like small number,
when compared to how rare this shark is, it is a significant number.
Figure 7. Megamouth shark caught in California drift gillnet
Photo Credit: NOAA/National Marine Fisheries Service
The third most caught species of animal was swordfish, which is also one of the primary
targets of this fishery. In the past ten years they caught a total of 3,709 swordfish, and kept a total
of 3,641 of them.
Despite swordfish and shark being the primary target of this fishery, they caught far more
ocean sunfish (a non-target species) than both shark and swordfish combined. Furthermore,
many shark species that were caught, such as, hammerhead sharks and blue sharks, are not sold
for human consumption. Therefore, of the total sharks caught in the last ten years, 34% were
Figure 8. Total caught and discarded of the three most common species caught by the
California drift gillnet fishery 2005-2015.
Some other species that were caught and discarded by this fishery in the last ten years
include: dolphins, sea lions, elephant seals, sea turtles, sperm whales, gray whales, pilot whales
and mink whales. Although these animals were caught frequently, these species were caught far
less than often than ocean sunfish, sharks and swordfish.
Swordfish Shark Ocean
Number of Animals
Figure 9. Select animals that were caught and discarded 2005-2015
Based on the data I analyzed, the bycatch produced by this fishery consisted of a diverse
array of marine species of all shapes and sizes. Thus, it is evident that drift gillnets are not
selective, and will catch almost any marine animal that swims or flies into the path of one. Based
on the vast size of the nets, they are a real threat to California’s marine wildlife. While all marine
wildlife is essential to the health of the marine ecosystem, the taking of the most vulnerable
species is of greatest concern. Of the species that were discarded, several are listed are listed as
“endangered” under the Federal Endangered Species Act (ESA). Therefore, killing only a small
number of these animals can result in catastrophic consequences for the survival of the entire
Number of Animals
species. For instance, the leatherback sea turtle population has declined 90% since the 1980’s,
and could be totally extinct by 2030 if nothing changes. Moreover, studies suggest that killing
more than one leatherback sea turtle every six years will significantly hamper recovery efforts of
this species (Karpa et al 2015). In the past ten years the California drift gillnet fishery has caught
three leatherback sea turtles, making this fishery a danger to the survival of this species. Along
with sea turtles, this fishery is also threatening the survival of several other endangered species.
Figure 4. Species listed as endangered under the Federal ESA that were caught and
Lastly, along with being harmful to marine wildlife, the California drift gillnet industry
does not appear to benefit California’s economy. According to the most recent Stock Assessment
and Fisheries Evaluation (SAFE) report, the California drift gillnet fishery generated a total of
$553,000 in revenue (PFMC 2015). Regulating this fishery has cost taxpayers between $1.3
million and $2.7 million a year (Karpa et al 2015). Therefore, this fishery could actually be
costing California more money than it produces in revenue.
Number of vessels and real (inflation adjusted) ex-vessel revenue ($1,000s) in the West
Coast drift gillnet fishery, 2005-2014
(PFMC 2015, pccouncil.org)
The California drift gillnet fishery has harmed and killed thousands of animals,
threatening the unique marine biodiversity of the West Coast. Moreover, this fishery is
contributing to the global problem of overfishing and deterioration of the marine ecosystem. As a
leader in environmental conservation, California should be setting the precedent for a global
sustainable fishing movement. Furthermore, the California drift gillnet industry provides less
than one percent of the entire revenue of the California fishing industry, and may even be costing
more money than it produces (Karpa et al 2015). Therefore, my first policy suggestion is
enacting legislation that immediately bans the use of drift gillnets and discontinues the issuance
of permits for this gear. Banning drift gillnets will benefit marine wildlife and save taxpayers
money by eliminating the costs of regulating this fishery.
Although this fishery employs very few people, the livelihood of the drift gillnet
fishermen should be taken into account. My second policy suggestion is to incentivize the use of
more sustainable gear, including deep-set buoy gear. Deep-set buoy gear is an alternative to drift
gillnets, and produces a fraction of the bycatch. This gear was authorized on the East Coast, and
has produced positive results (PEW Charitable Trusts 2015). California should authorize deep-
set buoy gear and make it easily available at a reasonable cost to people who are currently
holding drift gillnet permits. This should help minimize the cost for fishermen who will no
longer be able to use drift gillnets.
Lastly, California should prioritize the creation of more Marine Protected Areas (MPA)
to mitigate the damage that has already been done by overfishing and other unsustainable
activities. MPA’s are designated spaces of the ocean where human activities, like fishing, are
more strictly regulated than the rest of the ocean. California currently is home to a total of 124
designated MPA’s. Research has shown that MPA’s improve marine biodiversity, boost fisheries
and support overall ocean health (Ocean Conservancy 2016). Moreover, California’s coast is
important to the economy due to the large amount of tourists it attracts. Creating more MPA’s
will ensure that the coast remains pristine and continues to attract visitors from all over the
world. Lastly, creating more MPA’ s will ensure that California’s priceless marine population
and habitats remain protected for years to come.
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