302

EXPERIMENTAL FISHING

TO DETERMINE DISTRIBUTION OF SALMON

IN NORTH PACIFIC OCEAN

AND BERING SEA, 1956

Marine Biological Laboratory

LIBRARY

SFf^ '^41959
WOODS HOLE, MASS.

SPECIAL SCIENTIFIC REPORT-FISHERIES No. 302

UNITED STATES DEPARTMENT OF THE INTERIOR
FISH AND WILDLIFE SERVICE

SPECIAL NOTE

The International North Pacific Fisheries Commission,
established in 1953 by the International Convention for the
High Seas Fisheries of the North Pacific Ocean, coordinates
the research of the member nations: Japan, Canada, and the
United States. The resulting investigations provide data to
the Commission for use in carrying out its duties in connec-
tion with fishery conservation problems in the North Pacific
Occam. Publication of this scientific report has been
approved by the United States Section of the Commission.

United States Department of the Interior, Fred A. Seaton, Secretary
Fish and Wildlife Service, Arnie J. Suomela, Commissioner

EXPERIMENTAL FISHING TO DETERMINE DISTRIBUTION OF SALMON
IN THE NORTH PACIFIC OCEAN AND BERING SEA, 1956

by

Mitchell G. Hanavan and George K. Tanonaka
Fishery Research Biologists
Bureau of Commercial Fisheries

Contribution No. 10 to research conducted with
the approval of the United States Section of the
International North Pacific Fisheries Commission.

United States Fish and Wildlife Service
Special Scientific Report--Fisheries No. 302

Washington, D. C.
May 1959

The Library of Congress has cataloged this publication
as follows:

U. S. Bureau of Commercial Fisheries.

Experimental fishing to determine distribution of salmon
in the North Pacific Ocean and Bering Sea. 1956-
Washington, U. S. Dept. of the Interior, Fish and Wildlife
Service.

V. illus., fold, maps, diagrs., tables. 27 cm. (U. S. Fish and
Wildlife Service. Special scientific report — fisheries)

Vols, for 1956- issued as Contribution of the United States'

Section, International North Pacific Fisheries Commission.

1. Salmon. 2. Salmon-fishing — Pacific Ocean. 3. Salmon-fishing —
Bering Sea. i. Title. ( Series. Series : International North

Pacific Fisheries Commission. United States Section. Contribution)

Int 59-104

U. S. Dept. of the Interior. Library

for Library of Congress

The Fish and Wildlife Service series, Special Scientific
Report — Fisheries, is cataloged as follows:

U. S. Fish and Wildlife Service.

Special scientific report : fisheries, no. 1-
iWashingtonj 1949-

no. illus., maps, dlagn^. 27 cm.

Supersedes In part the Service's Special sclentiflc report

1. Fisheries — Research.
SH11.A335 639.2072 59-60217

Library of Congress [2]

ii

TABLE OF CONTENTS

Page

Introduction 1

Description of vessels 2

Gill net construction 3

Operations

Setting 3

Hauling 5

San^ling and preservation of salmon 5

Catch data 5

Length frequencies

Catch by mesh size 15

Catch by species 16

Red salmon 16

Chum salmon 17

Pink salmon 18

Silver and king salmon 18

Vertical distribution of salmon catch 18

Surface water temperatures and salmon catch 18

Species other than salmon 19

Literature cited 19

Appendix 21

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EXPERIMENTAL FISHING TO DETERMINE DISTRIBUTION OF SALMON
IN THE NORTH PACIFIC OCEAN AND BERING SEA, 1956

by

Mitchell G. Hanavan and George K. Tanonaka

U. S. Fish and Wildlife Service

Seattle, Washington

ABSTRACT

Five vessels were employed from May to October 1956 to study the
distribution of Pacific salmons in the North Pacific Ocean and Bering
Sea. The operation was designed to (1) provide samples of fish for
racial identification, (2) provide evidence of seasonal movements and
changes in the distribution of salmon and (3) study the ocean habitat
and conditions that control the distribution, movement and survival
of salmon.

The area of operation was approximately 2,000,000 square miles
extending from the coast of Washington and Oregon to longitude 175°
E. and from latitude 43° N. to 60° N. Within this area 195 gill net
sets resulted in the capture of 7,963 salmon.

Salmon were measured aboard the vessels before freezing. Length
frequencies are shown graphically by species and area and in relation
to the mesh size in which the fish were capture.

INTRODUCTION

The United States Fish and Wildlife
Service as a research agency of the Inter-
national North Pacific Fisheries Commission,
is engaged in a study to determine the ex-
tent of intermingling in the North Pacific
Ocean and Bering Sea of Asian and North
American salmons. In part this program re-
quires (1) the collection of large samples
of salmon from an extensive oceanic axea
and the preservation of these saunples for
racial analysis, (2) detection and measure-
ment of seasonal movements and changes in
the distribution of salmon and (3) the study
of the ocean habitat and the conditions
that control the distribution, movement and
survival of salmon.

The report which follows describes the
cruises and operations of five vessels
engaged in this program during the 1956 sea-
son. They include four schooner-type ves-
sels, the Tordenskjold, Mitkof , Paragon, and
Celtic^ chartered by the Branch of Fishery

Biology- , Fish and Wildlife Service, and
the John N. Cobb, operated by the Explora-

2/

tory Fishing and Gear Development Section -'
of the Service.

Figure 1 shows the pattern of this
extensive fishing and oceanogr aphic opera-
tion, the stations fished by the five ves-
sels, and the distribution of salmon,
steelhead and albacore during the period
of the study, which extended from mid-May
until the first week in October.

During this 4 1/2-month period there
was 195 gill net sets in a sampling area of
approximately 2,000,000 square miles. The
total salmon catch was 7,963 or an average

1/ Now Division of Biological Research,
Bureau of Commercial Fisheries.

2/ Now Branch of Exploratory Fishing and
~ Gear Research.

of 59 salmon per set for the 135 sets which
captured salmon. Albacore were taken on 15
sets and 45 sets produced neither salmon
nor albacore.

Oceanographic data were collected at
each set and at intervals between fishing
stations. A summary of these data was
reported by Love (1957) and the data will
appear in detail elsewhere.

Individual cruise reports describing
these operations in detail were prepared by
Richard Hajny, George Tanonaka, Douglas
Weber, Richard Johnsen, Eugene Hill and
Robert Ting, all of whom served as biolo-
gists aboard the vessel. The present report
summarizes data presented to the Commission
in these more detailed cruise reports.

DESCRIPTION OF VESSELS

Specifications for the four chartered
schooner-type vessels were as follows:

Vessel TORDEJJSKJOLD MITKQF PARAGON CELTIC

Total length 70 feet 72 feet 90 feet 70 feet

Gross tonnage 57 tons 62 tons 88 tons 57 tODB

Bfeadth 18 feet 18" 4" 19" 5" 17' I"

Draft 9' 1" 9 feet 9 feet 8* 2"

Cruising speed 8.7 knots 9 knots 8.5 knots 8.5 knots

Maximum speed 9.0 knots 9.5 knots 9.0 knots 9.0 knots

Horse power 150 200 165 135

Number of bunks .... 8 12 13 12

Freezer capacity (O'F) . 925 cu. ft. 440 cu. ft. 500 cu. ft. 450 cu. ft.

ma

Figure 2 — Salmon charter vessel m/V Mitkof.

The U. S. Fish and Wildlife Service
Exploratory Vessel John N. Cobb is described
by Powell and Peterson (1957).

Navigational equipment of the four
charter vessels included the following:
loran, radio direction finder, fathometer,
radio telephone, automatic pilot, and radar
(except for the MA Celtic).

Each charter vessel had a complement
of seven men: a master, four crewman, an
oceanographer from the University of Wash-
ington, and a Fish and Wildlife Service
biologist .

Figure 2 shows the charter vessel M/V
Mitkof , which is similar in appearance to
the other schooners described above.

GILL NET CONSTRUCTION

The standard gill net set consisted of
18 shackles (fig. 3). Each shackle of net
was approximately 50 fathoms in length (300
feet) and 20 feet deep. Four mesh sizes
were used in each set including 6 shackles
of 5 1/4 inch, 6 shackles of 4 1/2 inch,
3 shackles of 3 1/4 inch, and 3 shackles of
2 1/2 inch stretched measure. Gill nets
were of nylon constructed in the manner
described by Powell and Peterson (1957)
with the exception that "Spongex" floats
were used in place of cedar in nets con-
structed for the 1956 season. Two to six
fabricated seine floats (18" diameter) were
placed along the string to supplement the
wood and "Spongex" floats.

The 18 shackles were generally arranged
in the following order: 5 1/4 inch, 4 1/2
inch, 3 1/4 inch, 5 1/4 inch, 4 1/2 inch,
juid 2 1/2 inch; the same sequence repeated
three times for a total length of approxi-
mately 1.05 statute miles.

A 1/2- inch nylon drift cable was
attached along the corkline at every 10 feet
on the "shock" net and on the first six
shackles to help reduce the strain on the
corkline. This cable was attached to 200
fathoms of 3/4- inch nylon line, which in
turn was secured to the bow of the vessel by
a heavy sisail rope which served as a mooring
line. The sisal rope and nylon drift line
were submerged, acting as a spring line to
take up the surge of the vessel.

The Tordenskjold used a 40-foot trian-
gular section of 4-inch cotton trawl net
attached at the head of the first shackle
to take up the shock of wave action on the
gill nets while the Mitkof, Paragon and
Celtic used a 180-foot "shark" net for this
purpose. Two flagpoles with lights were
placed near each end of the string to mark
the position of the net during hours of
dctrkness. Figure 3 shows a typical gill
net set.

OPERATIONS

Setting

The gill nets were set from the stern
while the vessel traveled downwind at a
speed of about 4 knots. As the last shackle

4 SHACKLES OMITTED

- 250 FATHOUS

Figure 3. — Typical station set.

Figure h. — Initial phase of hauling operations on the
Mitkof . The nylon drift cable is brought in over
the roller, around the gurdy and coiled on the deck.

Figure 5 ---Gill net with salmon coming around the gurdy
on the Mitkof.

Figure 6. — Two crevmen in background repiling the gill
nets beside the pilot house on the Mitkof .

passed over the stern, the boat executed a
180-degree turn, and the mooring line was
attached to a cleat on the bow. The setting
operation required 15 to 20 minutes.

With few exceptions the nets were
fished at night from about five in the even-
ing to six in the morning, a total period
of approximately 13 hours.

Hauling

Nets were hauled in over a roller on
the starboard side of the well deck. As
the nets cleared the powered gurdy, or net-
puller (figs. 4 and 5), two crewmen picked
the salmon out of the net cind cleared the
web. The net was then passed to the stern
and re-piled in readiness for the next set
(fig. 6). Hauling required two to three
hours, depending on the size of the catch
and sea conditions.

Sampling and Preservation of Salmon

Salmon taken out of the nets during
hauling were placed in deck bins in accord-
ance with the mesh size from which they were

removed. They were recorded as to species
apparent direction of movement, and depth
in the net. Upon completion of hauling,
the salmon were tagged with a numbered,
colored strap tag which was attached to the
left gill cover to provide future identi-
fication. Fork length measurements were
recorded from a measuring board and the fish
were then placed in the freezer for shipment
to the Seattle laboratory for detailed mor-
phometric examination.

When possible, blood from live fish
was frozen for serological studies. Blood
samples were obtained by cutting through
the caudal penduncle and allowing the blood
to drop into a sterile jar.

CATCH DATA

Salmon catches by set, date, position
of set, species, and mesh size for the five
vessels are shown in tables 1 - 5. In-
cluded Eire numbers of hours nets were fished,
sea conditions, surface temperatures, inci-
dental fish catches, and observations of
sea mammals.

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40 45 50 55 60

Fork Length in Centimeters

Figure f. — Catch by Tordenskjold of all
species of salmon. Length frequency of
2,013 salmon in relation to mesh size.

35 40 45 50 55

Fork Length in Centimeters

Figure 8. --Catch by Mitkof of all species
of salmon. Length frequency of 1,665
salmon in relation to mesh size.

40 45 50 55 60

Fork Length in Centimeters

50 55

Fork Lengtti in Centimeters

Figure 9. --Catch by Paragon of all species
of salmon. Length frequency of 1,383
salmon in relation to mesh size.

Figure 10. --Catch by Celtic of all species
of salmon. Length frequency of 2,102
salmon in relation to mesh size.

14

Table 6 (page 11) is a summary by
vessels of the total salmon catch by species
and mesh size, total number and types of
gill net sets, the average number of hours
nets were fished, and the catch of salmon
per set.

The Tordenskjold operated in the east-
ern Bering Sea and Bristol Bay (fig. 1)
from May 24 to September 21 with two periods
(June 2 6 to July 23 and August 15 to Septem-
ber 10) spent in king crab studies in the
eastern Bering Sea. A total of 36 night and
1 day set weis made by the Tordenskjold with
salmon catches ranging from 1 to 987 fish.

The Mitkof operated in central Bering
Sea and in the North Pacific Ocean, south
of the western Aleutians (fig. 1). Fishing
extended from May 16 to September 16. A
total of 41 night sets were made with salmon
catches ranging from 2 to 323 fish.

The Paragon operated in the area south
of the Alaska Peninsula and the eastern
Aleutians (fig. 1) and fished from July 11
to September 24; a total of 41 night sets
and 4 day sets were made within this period.
Salmon catches ranged from 3 to 175 fish
per set.

The Celtic's area of operation was in
and south of the Gulf of Alaska on longitude
140°, 145°, 150°, and 155° W. (fig. 1).
Fishing extended from July 12 to September 19
and catches ranged from 4 to 150 salmon per
set.

The Fish and Wildlife Service's John
N. Cobb operated in the area off Washington
and Vancouver Island between latitude 45° and
50° N. westward to longitude 145° W. (fig.
1). The primary purpose of this cruise was
to locate areas of albacore abundance. Of
the 27 gill net sets made during the period
July 17 to August 29, four caught salmon.
Catches ranged from 1 to 3 fish.

Catch per-unit-effort data for the four
charter vessels are shown in tables 7-10
(pages 12 and 13). Effort data for the John
N. Cobb are not included because of the
small number (7) of salmon taken.

In eastern Bering Sea, where the Tor-
denskjold encountered mature reds migrating
to Bristol Bay, the 5 1/4-inch mesh proved
most efficient, accounting for more than
half the toted catch. The area occupied by

the Mitkof, central Bering Sea and south of
the Aleutians, produced smaller fish and a
greater proportion of juvenile reds and
chums. Significant numbers of juveniles
were taken in the 2 1/2-inch mesh, most of
them in central Bering Sea. The 3 1/4-inch
mesh proved most efficient for the Mitkof.
The Paragon, fishing south of the Aleutians
and the Alaska Peninsula, took few juveniles.
The 4 1/2-inch mesh proved most efficient in
this area. Further to the east, south of
Kodiak and the Gulf of Alaska, the Celtic's
catch was largely immature- adult chums.
Adjusting catch to number of shackles fished
shows that 4 1/2-inch and 3 1/4-inch meshes
were equally effective in this area.

Combined catches from all areas show
that the 4 1/2-inch mesh was most effective,
with a catch of 4.87 fish per shackle;
5 1/4-inch mesh was second with 3.85 fish
per shackle; followed by 3 1/4-inch mesh
with 3.49 fish per shackle; and 2 1/2-inch
mesh with 0.85 fish per shackle.

LENGTH FREQUENCIES

Catch by Mesh Size

Figures 7-10 and Appendix table 1
show the fork lengths of salmon caught in
the 5 1/4- , 4 1/2- , 3 1/4- , and 2 1/2-inch
mesh nets. These are listed by vessel or
area since the vessels fished separate
areas.—' The mean fork length of salmon
taken in the 5 1/4-inch mesh nets by the
Tordenskjold (fig. 7) was 57.4 centimeters,
in the 4 1/2-inch mesh the mean length was
54.2 centimeters, in the 3 1/4- inch mesh -
55.2 centimeters, and in the 3 1/4- inch mesh
- 55.8 centimeters. The 5 1/4-inch and
4 1/2-inch meshes, which took over 95 per-
cent of the total catch, showed selectivity
for size of fish. Apparently very few small
fish were available for capture in eastern
Bering Sea as few were taken in the smaller
mesh nets. Predominantly the fish taken in
this area were mature red salmon.

The fork lengths of salmon caught by
the Mitkof (fig. 8) show a more pronounced
mesh-size selectivity, indicating that the
stocks fished in the Mitkof 's area of

3/ John N. Cobb's length frequency data
omitted in figures.

15

operation were composed of individuals with
a wide range in size. The mean fork length
of salmon caught in the 5 1/4- inch mesh was
55.6 centimeters; 4 1/2-inch mesh - 50.1
centimeters; 3 1/4-inch mesh - 40.1 centi-
meters; and 2 1/2-inch mesh - 31.8 centi-
meters. The bulk of the catch in the 2 1/2-
inch mesh were juvenile chum salmon taken
in the central Bering Sea.

Mesh-size selectivity is also evident
in catches of the Paragon and Celtic (figs.
9 and 10). This again indicates that the
stocks fished by these two vessels in their
respective areas of operation were composed
of individuals with a wide range in size.
The mean fork length of salmon caught in the
5 1/4-inch mesh by the Paragon was 57.2 cen-
timeters; 4 1/2-inch mesh - 51.5 centimeters;
3 1/4-inch mesh - 43.2 centimeters; and
2 1/2-inch mesh - 33.8 centimeters. For the
Celtic, the mean fork length for the 5 1/4-
inch mesh was 56.1 centimeters; 4 1/2-inch
mesh - 49.7 centimeters; 3 1/4-inch mesh -
40.9 centimeters; and 2 1/2-inch mesh - 38.3
centimeters.

show the fork length frequencies of red,
chum, pink, silver and king salmon captured
by the four vessels.

Red salmon. — The red salmon length dis-
tributions (fig. 12) show two or more modes
indicating the presence of different age
groups within the areas fished by the Celtic,
Paragon and Mitkof . In the Celtic's catch
the mode falling between 29 and 42 centime-
ters is composed of 1-year-in-ocean reds and
the mode in the 43- to 60-centimeter inter-
val of 2-year-in-ocean reds. Red salmon of
61 centimeters and above are largely 3-year-
in-ocean fish with an increasing degree of
overlapping lengths in the older age groups.

The Paragon's catch shows a similar pat-
tern; the 27- to 43-centimeter interval is
composed of 1-year-in-ocean reds and the 44-
to 60-centimeter interval mode of 2-year-in-
ocean reds. Fish 61 centimeters and above
are largely 3-year-in-ocean reds.

The Mitkof 's 1-year-in-ocean reds fall
in the 26- to 40-centimeter interval and the

Figure 11 shows the two extreme sizes
of red szilmon taken in one set by the Mitkof.

Catch by Species

Figures 12 - 14 and Appendix table 2

Figure 11. — Maximum and minimum sizes of red
salmon taken in one set by the Mitkof.
The smaller is a one-winter- in-ocean
fish while the larger may have spent
either two or three winters at sea.

RED SALMON

John N Cobb
N = 5

30 35 40 45 50 55

Fork Length in Cenlimeters

Figure 12. --Length frequency distributions
of red salmon taken by five vessels.

16

2-year-in-ocean reds in the 41- to 62-centi-
meter interval. The bulk of the Mitkof's
reds were taken in the North Pacific, south
of the western Aleutians.

The Tordenskjold's red salmon catch
exhibits a definite unimodal curve. Of the
1,390 red salmon measurements, approximately
76 percent were those caught on the two
stations south of the Pribilof Islands on
June 20 and 21. These were in the majority
2-year-in-ocean reds. The absence of small
reds during the period from May to September
and the capture of large numbers of migrat-
ing adult fish at two stations suggest that
the eastern Bering Sea and the Bristol Bay
area are a migratory path rather than a
major feeding ground for red salmon.

The John N. Cobb's red salmon catch
included five fish ranging from 60 to 65
centimeters in fork length.

Chum salmon. — There are several modes
in the length frequencies of chum salmon
captured by the Celtic, Paragon juid Mitkof ,

CHUM SALMON

Celtic
N-- 1234

indicating the presence of different age
groups within their cireas of operation.

Age analysis indicates that the Cel-
tic's pronounced bimodal curve is made up
of 2nd-year chums in the 33- to 45-centi-
meter interval and 3rd-year chums in the
46- to 61-centimeter interval, with a very
small number of 4th-yeax fish overlapping
the latter in length.

Chums caught by the Paragon operating
south of the Alaska Peninsula and eastern
Aleutians, during the same period as the
Celtic (mid-July to mid-Stptember ) , exhibit
a pronounced mode in the 43- to 70-centi-
meter length interval. This mode includes
63 percent 3rd-year chums and 37 percent
4th-year chums. The 2nd-year chums fall in
the 31- to 42-centimeter interval.

A distinct group of 2nd-year chums is
found in the 28- to 35-centimeter interval
of the Mitkof's catch. These fish, with the
exception of one, were caught in the central
Bering Sea from July 6 to 15. The remaining
group, in the 36- to 71-centimeter interval,
is composed of 2nd-, 3rd- and 4th-year chums
with a great degree of overlap in length.

The unimodal curve of the Tordenskjold's
catch is composed largely of mature 4th-year
chums. The absence of small chums from May

PINK SALMON

35 40 45 50 55

Fork Length in Centimeters

40 45 50 55 60

Fork Lengtti in Centimeters

65

Figure I3. --Length frequency distributions
of chum salmon taken by four vessels.

Figure l4. --Length frequency distributions
of pink salmon taken by four vessels.

17

to September in the eastern Bering Sea and

Bristol Bay is as marked as the absence of

small reds, lending further evidence that

eastern Bering Sea is not a feeding area
for immature salmon.

Pink salmon. — The greater part of a
small catch of pink salmon was taken in the
Gulf of Alaska and the general vicinity of
Kodiak Island in late July and early August;
more than half of the total by the Celtic
(fig. 14). Small numbers were taken in mid-
June by the Mitkof in the central Aleutians
cind by the Tordenskjold in eastern Bering
Sea.

Silver and king salmon. — As shown in
tables 1-6 (pages 6-11), silver and king
salmon were taken in small numbers and were
widely distributed. Six juvenile silvers,
26 to 34 centimeters in length, were taken
near Kodiak Island. Most of the silvers
captured were in the 50- to 70-centimeter
length range.

King salmon ranged from 27 to 90 centi-
meters in length with no clearly dominant
size evident in the small numbers captured.
The Mitkof operating in the westernmost
areas made the largest catch, 33. A few
small kings, 27 to 38 centimeters in length,
were taken by the Mitkof and the Torden-
skjold, all of them in Bering Sea.

VERTICAL DISTRIBUTION OF
SALMON CATCH

It has been observed that most gill-
netted salmon are taken near the surface.
The Tordenskjold , with a predominance of
maturing red salmon in the catch, captured
1,366 or 55 percent in the upper 1/3, 699
or 28 percent in the middle 1/3, and 408 or
17 percent in the lower 1/3 of nets which
are approximately 20 feet in depth. This
vertical distribution is in conformity with
the observations of Barnaby in 1939 (Barna-
by, 1952) who reported that with a net some
90 feet in depth at least 95 percent of the
catch was taken within 30 feet of the sur-
face and "many of the fish were caught in
the top fathom". His catches were made at
the entrance to Bristol Bay on a line from
Cape Seniavin to Cape Newenham, and con-
sisted of maturing red and chum salmon.
Barnaby's sets were made during the day
while the Tordenskjold's were made at night.

Total season's catch of the Mitkof in
1956 shows 47 percent (523) in the top, 40
percent (447) in the middle, and 13 percent
(144) in the bottom third of the nets; the
Paragon, 42 percent (586), 44 percent (614),
and 14 percent (195); and the Celtic, 51
percent (1,045), 26 percent (523), and 23
percent (462). Cursory inspection of the
record sheets indicates that catches tend
to be greater near the surface in clam or
moderate seas, increase in the lower por-
tion of the nets during periods of rougher
we at he r .

An evaluation of vertical distribution
of salmon on the basis of this evidence
might, however, be misleading. While errors
of observation and record should be minor
and compensatory, there is little doubt that
a bias does exist in the nets themselves
resulting from the fact that fish can swim
under but not over them. This tends to in-
crease the efficiency of the upper portion
of the net in relation to the deeper por-
tion.

The evidence does suggest, however, a
surface tendency on the part of the salmon
which may be most pronounced in migrating
mature fish and may be influenced in some
degree by the condition of the sea. Fuku-
hara (1953) notes that it is the experience
of the extensive Japanese high seas gillnet
fishery that 85 to 90 percent of the salmon
are taken in the upper 10 feet of net, and
Powell and Peterson (1957) observe that 53
percent of the salmon taken by the John N.
Cobb in 1955 were gilled in the upper third
of the nets.

SURFACE WATER TEMPERATURES
AND SALMON CATCH

Surface water temperatures in the
region in which salmon were captured ranged
from 32.9° to 58.2° F. Variations relating
to both area and season contribute to this
temperature range of 25.3°. Lower tempera-
tures were encountered in eastern Bering
Sea and warmer temperatures near the south-
ern boundary of salmon distribution in the
North Pacific. No juvenile red or chum
salmon were captured in temperatures below
40° F. and, in Bering Sea, the largest
catches of mature red salmon were associated
with water temperatures of 42° and 44° F.
In warmer waters south of the Aleutian

18

Islands the largest salmon catches were made
in waters ranging from 49° to 55° F. with
the largest total catch associated with a
50° F. surface temperature.

SPECIES OTHER THAN SALMON

Catches of species other than salmon,
by vessels and by sets, are shown in tables
1-55 (pages 6 - 10). These data also are
summarized in table 11, below.

The range of steelhead (Salmo gairdneri
gairdneri) generally coincides with that of
the salmon. However, most steelhead were
taken in the Gulf of Alaska and none were
taken in Bering Sea. In contrast, a small
number of charrs (Salvelinus malma) were
caught in Bering Sea, but none were taken in
other areas.

Albacore (Thunnus alalunga) were taken
near the juncture of sub-Arctic and central
Pacific waters. The Mitkof recorded the
largest catch, 26 albacore on set number 27
at 47° N. , 175° W.

Next to salmon, the pomfrets (Bra ma raii)
were the most numerous species taken. They
were caught in large numbers in both salmon
and albacore waters of the North Pacific

Ocean with the apparent center of abundance
near the southern limits of salmon distribu-
tion. None was taken in the Bering Sea.

Of the four species of sharks taken on
the high seas, blue shark (Prionace glauca)
were the most numerous, the greatest number
occurring in the southern waters. The Mit-
kof caught 92 blue sharks on set number 28
at 47° N., 180°. H.

The capture o£ five boarfish (Pseudo-
pentaceros richardsoni) by the Paragon and
Celtic is the first reported occurrence of
this species in the North Pacific Ocean,
and is an extension of its known range by
5,000 miles (Welander et al . , 1957).

One of the John Dories (Allocyttus
verrucosus) captured by the Celtic is the
first of this species recorded from the
northern hemisphere (Welander et al . , 1957).

LITERATURE CITED

BARNABY, JOSEPH T.

1952. Offshore fishing in Bristol Bay
and Bering Sea. U. S. Fish and
Wildlife Service, Special Scien-
tific Report — Fisheries No. 89,
30 pp. October.

Table 11. — Incidental catch.

Scientific name

V

E S

S E L

S

Common name

TORDENSKJOLD

MITKOF

PARAGON

CELTIC

COBB

Total

Steelhead

Salmo gairdneri gairdneri

9

32

64

1

106

Albacore

Thunnus alalunga

38

9

5

25

77

Porafret

Brama raii

426

644

542

667

2279

Jack mackerel

Trachurus symmetricus

40

85

497

622

Giant skilfish

Erilepis zonifer

19

20

2

41

Atka mackerel

Pleurogrammus monopterygius

3

8
25

11

Three-spined sticklebacks

Gastercsteus sp.

25

Handsaw fish

Alepidosaurus aesculapius

4

1
1
1

1

Boarfish

Pseudopentaceros richardsoni

S

John Dory

Allocyttus verrucosus

1

Snapper

Sebastodes sp.

1

1

Squaretail

Tetragonurus cuvieri

5

36

41

Sablefish

Anoplopoma fimbria

1

2

3

Brovm ragfish

Acrotus willoughbyi

1

1

Anotopterus pharao

4

2

1

7

Taractes princeps

1

1

Blue shark

Prionace £lauca

181

33

47

225

486

Mackerel shark

Isurus nasus

2

13

19

9

2

45

Dogfish shark

Squalus acanthias

2

1

2

5

Mud shark

Hexanchus priseus

1

1

Herring.

Clupea pallasi

24

1

25

Yellowfin sole

Limanda aspera

12
34

1

12

Dolly Varden trout

Salvelinus malma

35

Juvenile wolf-eels

Anarrhichas orientalis

2

2

Sea poacher

Agonus acipenserinus

6

6

19

FUKUHARA, FRANCIS M.

1953. Japanese 1952 North Pacific

salmon-fishing expedition. U. S.
Fish and Wildlife Service, Commer-
cial Fisheries Review, 15(2): 1-17.
February.

LOVE, CUTHBERT M.

1957. Oceanographic observations in the
North Pacific aboard vessels of
the U. S. Fish and Wildlife Ser-
vice, summer and fall, 1956.
University of Washington, Depart-
ment of Oceanography, Special
Report No. 27. 42 pp. January.

POWELL, DONALD E. , AND ALVIN E. PETERSON
1957. Experimental fishing to determine
distribution of salmon in the
North Pacific Ocean, 1955. U. S.
Fish and Wildlife Service, Special
Scientific Report — Fisheries No.
205. 30 pp. July.

WELANDER, ARTHUR D. , RICHARD C. JOHNSEN,
AND RICHARD A. HAJNY
1957. Occurrence of the boarfish,

Pseudopent aceros richardsoni, and
the zeid, Allocyttus verrucosus,
in the North Pacific. Copeia,
1957, no. 3: 244-246. August.

20

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