Albacore
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R. Michael Laurs and Ronald C. Dotson. 1992. Albacore. In California�s Living Marine
Resources and Their Utilization. W. S. Leet, C. M. Dewees, and C. W. Haugen
(Eds.), 136-138. Sea Grant Extension Program, Department of Wildlife and
Fisheries Biology, University of California, Davis, CA 95616.
History of the Fishery
The albacore (Thunnus alalunga)
is a highly migratory species valuable to commercial and sport fisheries in
California. Commercial albacore fishing began off southern California near the
turn of this century. In 1903, an experimental pack of 700 cases of albacore
led to the development of the U.S. tuna canning industry. The fishery expanded
quickly in response to the almost instantaneous high demand for canned tuna,
which quickly outpaced the supply of albacore. By the 1920's, bluefin,
yellowfin, and skipjack tuna were also being canned. However, albacore is the
only tuna species, which may be marketed as "white meat tuna," and it
brings a premium price at the dock and in the can.
The geographic range of the U.S.
north Pacific albacore fishery has expanded during the past eight decades.
Early commercial fishermen made one-day trips within coastal waters off
southern California. The fishery extended northward and seaward, and by the
late 1930's it reached to waters off the Pacific Northwest and several hundred
miles offshore. There was a major offshore extension in the mid-1970's across
the central Pacific to about the Dateline. However, beginning in the
mid-1980's, there has been a general shrinking of the breadth of the fishery to
within about 500-600 miles of the Pacific west coast
Since the early 1980's, about 90
percent of the annual albacore catch has been made by trolling jigs and 10
percent by live-bait pole-and-line fishing. In earlier years, live-bait fishing
sometimes accounted for up to 40 percent of the annual catch. In some years, up
to a few hundred tons of albacore maybe caught by purse seine vessels, usually
incidental to bluefin tuna fishing. California-based drift gillnet vessels also
catch small quantities of albacore incidental to shark and swordfish fishing.
Generally, two fishermen conduct fishing operations from troll vessels and
three to five fishermen from live-bait vessels. Many vessels, which fish for
albacore, also take part in other fisheries. Their participation in the
albacore fishery depends on the price and availability of albacore, the success
of other fisheries, and weather conditions during the albacore season. In the
1940's, there were about 500 vessels in the albacore fleet. A high of 3,000
boats was reached in 1950; the number dropped to about 1,000 vessels by 1960,
climbed to 2,100 vessels during the 1970's, and dropped to fewer than 500 boats
in the late 1980's. The average size of albacore jig boats is about 45-50 feet,
with a sea-keeping capability of about one to two weeks. In recent years, there
has been a steady increase in vessels of 60-80 feet, which are capable of
fishing at sea for six to eight weeks. The larger vessels may participate in a
virtual year-round albacore fishery by fishing in mid-North Pacific waters, the
North American coastal fishery, and in the recently established South Pacific
albacore fishery.
The North Pacific albacore stock is
also harvested by Asian fisheries, including a Japanese pole-and-line fishery
in the spring, which targets two to five year old fish off the Japanese coast
eastward to near the Emperor Seamount chain. There are also Japanese, Taiwanese
and South Korean longline fisheries, which target five to seven plus year old
albacore in subtropical and temperate waters across much of the Pacific during
winter. Beginning in the early 1980's, Asian high-seas drift gillnet fisheries
have targeted two to four year old albacore across much of the Pacific. In addition,
there is a relatively small Canadian troll fishery for albacore during years
when they are distributed in waters off British Columbia.
In the late 1890's and early 1900's, sport fishermen on Private
boats would fish for large bluefin tuna inside the Channel Islands. The 10-20
pound albacore, which would strike the bait intended for a 100-pound bluefin,
were considered a nuisance and were usually tossed over the side after landing.
Gradually, some boats began to carry spoils anglers as paying passengers, who
quickly came to appreciate the fighting and eating qualities of the albacore,
or "longfin tuna," as they are often called. The fishing for hire
party boats gained in popularity in southern California, and by the 1950's,
about 100-150 fished for albacore in near shore waters.
In the 1960's, the albacore runs began to shift outside the
Channel Islands and to waters off upper Baja California, over 50 miles from
southern California ports. In response to this, larger commercial passenger
fishing vessels with a greater range were built. Today, there are about 40
large commercial passenger fishing vessels, mostly in southern California and
some in the Morro Bay and San Francisco area, that are capable of carrying 20
to 60 sport fishermen on one to three-day fishing trips. In addition to the
large vessels, there are about 50 to 60 smaller vessels that typically are
chartered to smaller fishing parties of around six.
As the result of increased numbers of private boats, the ready
availability of modem commercial passenger-carrying fishing vessels (CPFV), and
improvements in sport fishing gear, albacore sport fishing has become
increasingly attractive to California anglers. In fact the first albacore of
the season caught in southern California waters sets off "albacore
fever" among recreational fishermen. No other sport fish in southern
California elicits the excitement exhibited each year by the thousands of
fishermen pursuing albacore. Over 120,000 anglers go out on southern California
CPFVs in search of albacore during the course of a season. Albacore sport
fishing in southern California contributes about $23 million to the local
economy through the purchase of the boat ticket tackle, food, gas, licenses,
and lodging.
Status of Biological Knowledge
The albacore is a highly advanced teleost with many specialized
adaptations. It is capable of thermoregulation, has a high metabolic rate, an
advanced cardiovascular system, specializations in the circulatory system and
blood/gas exchange systems, distinctive enzyme and complement systems, and high
energetic costs for migration which maybe partly met by utilization of stored
fat
The distribution of albacore is cosmopolitan in subtropical and
temperate waters of all oceans. Off the coast of North America, the distribution
during summer and fall months may range from lower Baja California, northward
to the Queen Charlotte Islands, Canada, and occasionally into the Gulf of
Alaska.
There is a growing body of evidence that the North Pacific
albacore population is not as homogeneous as is usually assumed. Results from
albacore tagging studies suggest that at least two proposed subgroups offish
constitute the North Pacific albacore population and that these subgroups have
different migratory patterns, modal sizes in the U.S. fishery, growth rates,
and peak spawning periods. While the subgroups are geographically separated and
are differentiated by dissimilarities in biological or fishery statistic
criteria, they are not believed to be genetically distinct.
Albacore make extensive movements during their lifetime. The
degree of migration is geographically most extensive in the pre-adult ages
between about two and five years. Fish of these ages may conduct trans-oceanic
migrations in temperate and subtropical waters, following well-defined routes
between the eastern and western or central Pacific. However, the spawning
adults, above about six years, undertake relatively limited movements, mostly
within the subtropical and tropical regions of either the western, central or eastern
Pacific.
Results from extensive albacore tagging indicate that the northern
subgroup of albacore is fished by the U. S. fishery north of about 40� N, the
Japanese pole-and-line fishery in the western Pacific, and the Asian longline
fishery. The southern subgroup appears to be fished by the U.S. fishery south
of about 40�N, and the Asian longline fishery, but only to a limited extent by
the Japanese pole-and-line fishery.
Based on physiological research findings, the normal habitat of
albacore is within a temperature range of 50�-64�F, with dissolved oxygen
saturation greater than about 60 percent. While individuals may temporarily
move into waters outside of these values, thermoregulation and respiration
functions will be adversely affected and operate marginally. The acoustic
tracking of free-swimming albacore has demonstrated that albacore customarily
live within the depths of the thermocline, rather than the upper mixed layer as
has been generally presumed.
The migration, distribution availability, and vulnerability of
albacore are strongly influenced by oceanographic conditions in the Pacific
Ocean, notably oceanic fronts. The seasonal migration of albacore into North
American coastal waters is associated with the North Pacific Transition Zone water
and its frontal boundaries. In addition, oceanographic conditions also play an
important role in the local concentrations and movements of albacore in coastal
waters off Worth America. Albacore tend to aggregate on the warm side of
upwelling fronts and move away from the fronts upon their disintegration in
response to wind shifts unfavorable for upwelling. Satellite images of ocean
color and sea surface temperature and concurrent albacore catch data clearly
show that the distribution and availability of albacore off California are
related to coastal upwelling fronts and that albacore are most abundant in
warm, clear, blue oceanic waters near temperature and color fronts at the
seaward edge of coastal water masses.
It is presumed that albacore aggregate in the vicinity of
upwelling fronts to feed on small fishes, squids, and crustaceans that are
plentiful in these areas. Yet it remains unclear what physical factors prevent
albacore from crossing to the cooler side of these fronts in order to reach the
highest potential forage biomass. Past beliefs have stressed confinement to a
physiological optimum temperature range; however, explanations for
environmental preferences of albacore are changing as new knowledge is
acquired. The finding that albacore can regulate their body temperatures
suggests that temperatures on the cool side of an upwelling front should not be
limiting. Studies of free-swimming albacore in relation to ocean thermal
structure, using acoustic telemetry and coincident oceanographic sampling, have
shown that, while albacore would not cross from the warm side to the cool side
of an upwelling front which had a horizontal sea surface temperature gradient
of about a 4�F over a few miles, the fish would routinely swim through vertical
temperature gradients up to about 180 F. The fish made extensive vertical
excursions up to several hundred yards and crossed the thermocline in waters
adjacent to the upwelling front Recent research involving acoustic telemetry of
free swimming albacore, satellite measurements of ocean color and temperature,
and oceanographic sampling of water optical and other characteristics, and
potential forage abundance, indicates that water clarity as it affects the
ability of albacore to detect prey is an important mechanism underlying the
aggregation of albacore on the worth clear sides of upwelling fronts.
Status of Population
Fishing effort and catch of albacore in the Japanese pole-and-line
and the U. S. surface fisheries have declined, beginning in the early 1980's.
In contrast recent landings in the Japanese longline fishery have been
relatively constant and there has been a rapid development of Asian gillnet
fisheries that harvest large numbers of albacore in the North Pacific.
Several
factors are associated with the decline in the traditional surface fisheries,
but their relative importance is unknown. It appears that no single factor is
responsible, but that the decline in catches is a result of complex
interactions among factors, including (1) a reduction in overall fishing effort
for albacore, (2) lack of fishing in areas of traditional high catch, (3)
indications of population decline and (4) major anomaly patterns in
oceanographic conditions across much of the North Pacific in the niid-1980's
and early 1990's.
References
Clemens, H.
B. 1961. The migration, age, and growth of Pacific albacore (Thunnus
alalunga), 1951-1958. Calif. Dept Fish and Game, Fish Bull., 11 5, 128p.
Dotson, R.
C. 1980. Fishing methods and equipment of the U.S. west coast albacore fleet. U.S.
Dep. Commer., NOAA Tech. Memo., NOAA-TM-NWS-SWFC-8, 126 p.
Laurs, R.
M., P. C. Fiedler, and D. R. Montgomery. 1984.Albacore tuna catch distribution
relative to environmental features observed from satellites. Deep-Sea Res.,
31(9):1085-1099.
Laurs, R. M.
and R. J. Lynn. 1977. Seasonal migration of north Pacific albacore, (Thunnus
alalunga) into North American coastal waters: Distribution, relative
abundance, and association with transition Zone waters. Fish. Bull., U.S.
75(4):795-822.
Laurs, R. M.
and J. A- Wetherall. 1981. Growth rates of North Pacific albacore, (Thunnus
alalmga), based on tag returns. Fish. Bull., U.S. 79(2):293-302.
Updated 6/14/01 - Sea Grant Extension Program, University of California, Davis