THE IMPACT OF DRIFTNET FISHING
ON SUSTAINABLE FISHERIES
"Roughly a quarter of the animal protein food intake of the peoples
of the world comes from ocean and fresh waters of the world" (Bardach
pers. comm. 1991). However, there is a limit to the ocean's ability to produce
biomass. With ever growing demand to feed an ever increasing world population
it is imperative to fish all fisheries at sustainable levels and to reduce
waste to zero. As the driftnet catch figures indicate, driftnet fisheries
have caused an overall decrease, not an increase in the total amount of
protein harvested. The total tonnage of salmon harvested in both the Atlantic
and Pacific Oceans decreased substantially, with decreasing population numbers
and decreasing body weight both attributable to the high seas harvesting
of juvenile, low weight individuals. The North Pacific albacore stocks were
decimated, the albacore stocks in the South Pacific were severely overfished,
and the Indian Ocean and Atlantic Ocean stocks may suffer a similar fate.
Other stocks, such as pelagic armorhead and Pacific pomfret, were heavily
exploited by driftnets without anyone reaping the benefits.
In his report to the United Nations General Assembly in 1990, the U.N. Secretary-General
announced that: "[Y]ields of the stocks of the most preferred fish
have already reached or are approaching levels of full exploitation."
New players on the fishing scene or players that seek to increase their
portion of the take of marine resources now do so to the detriment of those
fishermen already exploiting the resources. Nowhere is this more true than
the driftnet fisheries. With the possible exception of the North Pacific
neon flying squid fishery, all target species taken by driftnet fisheries
were already being exploited by fishermen using other, more sustainable
and more manageable methods of fishing. Even the neon squid fishery cannot
be defended because its by-catch, which is lost or mostly discarded, includes
enormous quantities of pelagic armorhead, Pacific pomfret, and blue shark,
species that must also be harvested in a sustainable way to meet the ever
growing demand for marine protein.
Sustainable fisheries are sustainable because they are very focused fisheries,
catching the target species and little else. They are generally active,
not passive fisheries. Waste and by-catch is minimal. The catch is usually
fresh. Sustainable fishery methods include (1) encircling seine nets, (2)
long lines, (3) pole and line or live bait and (4) jigging and trolling.
(Figures 12a, 12b, 13a, 13b)
Sustainable fisheries can be managed so that they remain maximally productive.
Management requires that fishing effort be controlled so that no more and
preferable less than the maximum sustainable yield (MSY) of the target population
is caught during the year by all fishermen fishing on that population. This
means that the amount of the population that is caught each year should
not exceed the amount of growth and recruitment into the population each
year. Most importantly, this means that fishermen can fish the target population
year after year without depleting it and threatening their own livelihood.
Since maximum sustainable yield is difficult to pinpoint and must also take
other sources of mortality into consideration, it generally is safer to
take the optimum sustainable yield (OSY) of a population, which is less
that MSY. Scientists that met in Sydney, B.C. to evaluate the results of
driftnet fishing qualified the definition of "management" even
more, in recognizing that removing a percentage of the target species could
also affect other species and even the entire ecosystem of which the target
species is only a part. This new qualification is even more important when
a fishery removes large numbers of other animals as by-catch.
"The use of marine resources should promote efficient harvests in ways
that will (a) ensure as far as practicable that human activities do not
result in the decrease of any population of marine species below a level
close to that which ensures the greatest net annual increment or (b) will
not catch numbers of either target or non-target species that will result
in significant changes in the relationships among any of the components
of the marine ecosystem of which they are a part" (U.S. Summary Report
1991). Tuna fishermen often exploit these relationships, using birds, dolphins
and ocean sunfish as "bird dogs". Without these animals in the
ocean to guide them to schools of tuna, fishermen found that they spent
much more time and fuel searching for their prey. However, fish are not
harvested with the primary purpose of feeding mankind on a sustainable basis.
In market-oriented economies fishing is regarded as a business, not a method
of feeding the hungry. Investors in fishing vessels and gear want to recoup
their investment in the shortest period of time. On a business balance sheet
the need for short-term profits usually prevail over the desire for long-term
The North Pacific Albacore Fishery - A Case
Five States fished for albacore in the North Pacific in the 1980s: Canada,
Japan, the Republic of Korea, Taiwan, and the United States. The Canadian
albacore fishery peaked in 1972 and declined to landings generally below
100 metric tons after 1984. The Japanese albacore fleet fished with pole
and line (bait boat), long-line, and driftnet. Its pole and line fleet fished
primarily in the western North Pacific west of 170 deg E. The Japanese large-mesh
albacore driftnet fleet fished east of 170 deg E and has been described
above. The Japanese long-line fleet fished all over the Pacific Ocean. The
South Korean albacore fishery used long-lines primarily. The Taiwanese used
large mesh drift nets to fish for albacore in the North Pacific; there was
a small long-line catch. The U.S. albacore fleet was predominantly trolling
vessels (jig vessels) between 25-100 feet, although there were still some
baitboats operating in the late 1980s. The U.S. trolling fleet fished north
of the Hawaiian archipelago, moving east to fish off the west coast of the
United States mainland as the season progressed.
The Target Species
North Pacific albacore (Thunnus alalunga) spawn west of the Hawaiian Archipelago
between 10 deg and 20 deg N. Sub-adults are found further north between
30 deg and 50 deg N. Seasonal transpacific migrations also occur, and as
a result, "there is a potential for significant interactions between
the Japanese fisheries in the western Pacific and North American fisheries
in the eastern Pacific" (Wetherall 1989). The surface albacore fisheries,
which utilize trolling gear, baitboats, and large-mesh driftnets, fish for
sub-adult albacore in waters between 15 and 19 deg C, although albacore
have also been taken 10 - 11 deg C water by squid driftnets (Wetherall 1989).
In 1989, the albacore taken by the trolling fleet averaged 65 cm in length
and were three to four years of age. Albacore begin to reproduce at about
five years of age.
The Fishing Season
The Japanese large-mesh albacore driftnet fleets fished north of the Hawaiian
archipelago between January and May to avoid competing with the squid driftnet
fleets that begin fishing in approximately the same area in May. The U.S.
trolling fleet with its smaller vessels fish in the summer and early fall
to avoid the heavy winter seas. The trolling season is generally between
June and October. The trolling fleet's normal fishing grounds are 80-100
miles south of the squid grounds and the fleet moves east as the season
progresses. In the summer of 1991, radio messages from the trolling fleet
reported that hundreds of driftnet vessels were fishing in the middle of
the albacore grounds and that trolling vessels were picking up chunks of
small mesh driftnet with their hooks.
Albacore Trolling Operations
A trolling vessel trails 1014 hooks from two lowered outriggers and normally
cruises around 56 knots. The fleet operates during the daylight hours only.
The fishery is closely targeted to catch albacore and nothing else; there
is no unintentional by-catch. Albacore are brought on board alive and are
immediately chilled down, vacuum packed and/or frozen, producing a top quality
product. However, after high-seas driftnet operations began, trollers began
catching a lot of net-marked albacore; estimates varied between 18% (Rensink
and Miller 1991) and 50% (Hornidge pers. comm.). The percentage increased
the nearer the trollers fished to the driftnet fleet (Murray et al 1990).
Some of the troll catch were still bleeding and bruised from the nets; others
had old scars. Encounters with nets removed much of the mucous that protects
the fish and most fish that were net-marked had external parasites. Some
tuna were missing a fin. Trollers also noticed that in addition to a lot
less fish, the albacore schools had broken up and the fish appeared skittish
and stopped biting after 10 minutes or so; previously they bit for up to
two hours. Trollers also look for seabirds and ocean sunfish to find tuna.
The huge ocean sunfish act like fish aggregation devices (FADs). With the
advent of driftnet fishing and the large numbers of ocean sunfish taken
as by-catch, there were few left to use as fish finders. Fishermen also
reported that they weren't seeing as many birds as they used to. In 1990,
albacore trollers spent approximately 75% of their time looking for the
fish that birds used to find for them.
Albacore trolling is a very economic way to fish. A crew of two or three
people working a 1821 meter vessel could land one and one half tons of albacore
a day in the late 1970s. A 350 GRT large-mesh driftnet vessel with a crew
of 20 also could land 1/2 tons a day, but with much higher fuel, gear and
labor costs and a huge amount of wasted by-catch.
During the 1989 season, approximately 450 U.S. vessels trolled for albacore
in the North Pacific for a total of 8,100 days of effort. They brought in
a record low of 1,918 metric tons. Except for the large-mesh driftnet fishery
(Table 2), catch/effort statistics from the albacore trollers fishing east
of 170 deg E steadily declined in the 1970s and 1980s. (Figure 14) In May
of 1981, the Japanese government relegated its driftnet fleets to a zone
east of 170 deg E to avoid competition with the Japanese pole and line and
squid-jigging fleets. In that year the albacore catch of its large-mesh
driftnet fleet more than tripled (10,348 metric tons). The incidental catch
of albacore by the Japanese squid driftnet fleets for that year is not known.
However, the number of Japanese squid driftnet vessels that year rose to
534 and the squid fishing grounds overlap the albacore grounds. Current
data indicates that sub-adult albacore two to three years old make up a
large portion of the by-catch of the squid driftnet fleet. The U.S. trolling
fleet caught 12,694 metric tons of albacore in 1981. In 1982, the catch
of albacore by the Japanese large-mesh fleet fishing between January and
May increased to 12,511 metric tons. By the time the U.S. trolling fleet
arrived on the albacore grounds in June, the albacore stocks had been decimated.
Their catch after several months of effort amounted to half of what it had
been the previous year.
Since 1982 the North Pacific albacore stocks have not recovered. The trolling
fleet doubled and tripled its time at sea trying to find albacore; its catch
diminished to 1/4 to 1/6 of what is was. Data presented at the Pacific Albacore
Workshop in May 1989, indicated that whole year classes were either missing
or much decreased (Bartoo and Watanabe 1989). In 1989, the abundance of
albacore three, four and five years old may have been at all time lows.
By 1990, stocks of albacore off the west coast of the U.S. mainland were
disappearing (Figure 15) The long-line catch of adult albacore also declined.
Official estimates of the total catch of albacore by all Japanese driftnet
fisheries was 10,569 metric tons in 1984 and 13,132 metric tons in 1985
(Japan Ministry of Agriculture, Forestry and Fishery Yearbooks). Unofficial
estimates for those years were 14,352 and 20,199 metric tons, respectively
(JFA Internal Report 1989). (Table 4) None of these figures take into consideration
the amount of albacore lost as dropouts. The total catch of North Pacific
albacore from all sources was 75,326 metric tons in 1984 and 68,614 metric
tons in 1985. In 1972, the year before driftnets began to impact the central
North Pacific, the total catch of albacore from all sources was 108,790
metric tons. (Table 2) Estimates of maximum sustainable yield (MSY) for
the North Pacific albacore stocks had been estimated at between 85,000-135,000
metric tons per year (Wetherall 1989), but are currently being revised downward
as a result of taking into consideration the patchy distribution of the
resource and the increasing ability of fishermen to locate high density
patches due to modern technology (Bartoo and Watanabe 1989; Kleiber and
Perrin 1989). (Figure 14) Scientists meeting at Sidney, B.C. in June 1991,
estimated that "approximately one-half of the fisheries mortality for
albacore in the North Pacific is attributable to the driftnet fisheries"
(U.S. Summary Report 1991).
The North Atlantic Salmon Fisheries
At the beginning of the twentieth century, driftnets made of hemp, tar-coated
cotton, and other natural fibers were widely employed at the mouths of estuaries
to catch mature Atlantic salmon as they returned to their native streams
to spawn. In the 1960s, however, these natural fiber nets were replaced
with nets made of multifilament and monofilament nylon. This new material
greatly increased the effectiveness of the technique, permitting much longer
nets to be set 24 hours a day in rough weather far out in the Atlantic.
These driftnets took vast numbers of underweight, immature salmon. They
also wasted much of the resource. Left unattended for hours, often in rough
seas, the driftnet-caught salmon putrefied, dropped out of the nets, or
fell prey to scavengers. Salmon that escaped were later found ulcerated
due to net damage and unable to spawn. Salmon that were brought to shore
had to be sold at a much lower price than that caught fresh in local rivers.
As the popularity of the off-shore driftnet increased, the salmon stocks
declined, threatening the livelihood of the traditional salmon fishing communities.
One by one the Atlantic salmon states of Scotland, England, Wales, Ireland,
Norway, and Canada banned the use of nylon driftnets within their 12-mile
territorial seas (Mills 1989). However, most still permitted their fishermen
to use the technique on the high seas.
The decline of the Atlantic salmon stocks was greatly accelerated with the
discovery that salmon from all over the North Atlantic congregated west
of Greenland and in the Davis strait to feed and put on weight. Almost immediately
this region was inundated with driftnetters. The Greenland catch jumped
from sixty metric tons in 1960 to 1539 tons in 1964, to 2260 tons in 1969-1971--about
17% of the world catch. In 1969, an international conference organized by
the Atlantic Salmon Research Trust in London and attended by representatives
of eleven major fishing countries agreed unanimously that all driftnetting
of salmon in the North Atlantic should be forbidden for a period of ten
years. That same year, the International Convention for the Northwest Atlantic
Fisheries (ICNAF) Commission adopted a ban on high seas fishing for Atlantic
salmon. Denmark, the Federal Republic of Germany and Norway objected
to the ban. The failure of Denmark to recognize the ban effectively nullified
the measure. Although Denmark agreed to freeze its catch at its 1969 level
and a quota of 1200 tons was set by ICNAF for the 1971 season, the interim
measure permitted fishing to continue at a dangerously high level from the
standpoint of long range conservation. In response, in 1971 the United States
Congress passed the Fishermen's Protective Act ("Pelly Amendment"),
which authorizes the President to prohibit the importation of fish and fishery
products from any nation that does not practice fishery conservation on
the high seas.
In 1972, the Danish and U.S. governments signed an agreement implementing
the ICNAF resolution, in which the Danes agreed to reduce driftnetting for
salmon on the high seas off the coast of Greenland. In 1973, the Northeast
Atlantic Fisheries Commission adopted a recommendation banning driftnet
fishing for salmon on the high seas of the Northeast Atlantic. The ban was
introduced gradually, becoming total in 1976.
The North Pacific Salmon Fisheries
The high seas salmon driftnet fisheries have been condemned by many as an
economically inefficient, non sustainable method of fishing. They catch
salmon before they can reach full size and bring the maximum market price,
up to fifty percent of the catch drops out of the nets before they can be
brought on board resulting in additional waste, and the various North American
and Asian stocks intermingle on the high seas, making it impossible to protect
specific stocks known to be in trouble. After the 1980 chinook harvest,
one study estimated that the inshore yield to U.S. fishermen would have
been 6.5 times greater than the high seas yield, if the stocks had been
allowed to mature and return to their native streams (Note 1982).
Furthermore, the high seas squid driftnet fisheries of Japan, the Republic
of Korea, and Taiwan had high "incidental" catches of salmon,
which may not have been so incidental (the Japanese squid fishery used driftnets
similar to those used by the salmon fishery) (Anderson 1989; Matsen 1989).
Begun in 1978, the Japanese squid fishery quickly expanded across much of
the North Pacific. By agreement, the fishery was supposed to stay in waters
too warm for salmon. However, Canadian research data indicates a large overlap
in stocks of neon flying squid and stocks of all six species of North American
salmon (LeBrasseur et al 1988; LeBrasseur 1987). Neon squid are commonly
found in waters between 15 and 24 deg C in July and August and in waters
between 10 and 22 deg C in September through December. Pink, coho, and chum
salmon have all been caught in 14-15 deg C water in July and August, and
in September, all six salmon species share part of the same temperature
range with neon flying squid (Burgner and Meyer 1983). (Tables 22a and 22b)
Over the years the Coast Guard sighted numerous Japanese driftnet vessels
fishing north of the boundaries established by Japanese regulations (Gordon
1985). Furthermore, neither the Republic of Korea nor Taiwan are bound by
the 1978 Protocol's salmon fishing boundary restrictions, although Taiwan
agreed to respect a squid fishing boundary similar to Japan (Gordon 1985)
and the ROK established some squid boundaries for its fleet. In 1983, Taiwanese
driftnet vessels were reported harvesting significant numbers of North Pacific
salmon. In September 1983, following pressure from the INPFC member States,
and again in January and June 1984, Taiwan issued a series of directives
banning the harvest of salmon on the high seas and restricting the export
of salmon from Taiwan (Herrfurth 1988). The Japanese Ministry of International
Trade and Industry began restricting salmon imports from Taiwan in June
Despite these restrictions, squid fleets from Japan, the ROK, and Taiwan
continued to fish illegally for salmon, taking large quantities before they
could reach optimum size or could reproduce. Many of these fish came from
coastal hatcheries and represented years of work and investment by their
State of origin. Others came from natural stocks being driven to extinction
by the combined effects of high seas driftnet fishing and the numerous hydroelectric
dams along their spawning routes
Between 1985 and 1988, the numbers of salmon returning to spawn in Alaska
were at all time lows. In 1987, only four million of a 10 year average annual
run of 18.5 million fish appeared in the rivers of Southeast Alaska. In
1988 the return of coho salmon to Southeast Alaska hatcheries was only five
percent of what was expected. By 1990, the Alaska stocks rebounded somewhat,
possibly as a result of the reduction in driftnet fishing in the Bering
Sea and the EEZ south of the Aleutian Islands. However, in 1989 and 1990,
there were record lows in stocks of salmon returning to spawn in the rivers
of Western Canada and the northwest United States, possibly as a result
of heavy salmon poaching by the squid fleets beginning in the early 1980s.
In April 1994, the Columbia River spring chinook runs collapsed (The Oregonian
April 1994). U.S. fisheries biologists estimated that only 19,000 fish would
head up river past the Bonneville Dam. Chinook, the largest of the salmon
species, spend three to eight years at sea gaining weight. The decimation
of these stocks can be attributed not only to the effects of multiple dams
along the Columbia River system, but to large-scale driftnet fishing that
took place in the North Pacific during 1986 -1991, years of maximum effort
by the high seas driftnet fleets. (See also the North Pacific Salmon Driftnet
Fisheries and The Enforcement Problem).
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