Seamount Fishery Resources Within The Southern Emperor-Northern Hawaiian Ridge Area

Full text

Proc. Res. Inv. NWHI
UNIHI-SEAGRANT-MR-84-01
SEAIYOUNT
FISHERY RESOURCES WITHIN THE
SOUTHERN
EXPEROR-NORTHERN HAWAIIAN RIDGE
AREA
Robert
L.
Humphreys, Jr., Darryl
T.
Tagami, and Michael
P.
Seki
Southwest Fisheries Center Honolulu Laboratory, National Marine
Fisheries Service,
NOAA,
P.O.
Box 3830, Honolulu, Hawaii 96812
ABSTRACT
The summits of the seamounts comprising the southern
Emperor Seamount Chain and northern Hawaiian Ridge
(Koko-Hancock Seamounts) lie at depths of 250 to 400 m;
Russian data indicate that the topography produces much
surface current meandering and upwelling in the region.
In 1967, Soviet trawl fishermen discovered vast quanti-
ties of pelagic armorhead, pentaceros richardsou
',
and
to a lesser extent alfonsin,
Bervx
mend-, closely
associated with summits of these seamounts. Two years
later, Japanese trawlers entered the fishery. They
achieved their highest annual catch per unit of effort
in 1972 with a sharp decline after 1976. With the
advent of the 200-mile U.S. fishery conservation zone,
the Hancock Seamounts came under
U.S.
jurisdiction.
Comparison of the
U.S.
foreign observer data obtained
on Japanese trawlers in 1978-82 with earlier Japanese
data show trawl catches on Hancock have generally been
declining since the high catch of 1972. Seamounts of
the Hawaiian Ridge located south of Hancock and east
of
180"
longitude differ in having shallower summits,
higher summit water temperatures, and fish faunas domi-
nated by subtropical reef and snapper-grouper species.
Meristic and electrophoretic work on pelagic armorhead
indicates the existence of one stock inhabiting the
range of seamounts between Koko and Hancock. Morpho-
logical variation among pelagic armorhead
is
little
understood.
alf onsin
pelagic armorhead
seamounts
2
83

INTRODUCTION
The islands, banks, reefs, and seamounts of the Hawaiian
Ridge extend northwesterly from the island of Hawaii some 3,500
km
to
Colahar, Seamcunt.
To
'-he northwest of Colahan the Emperor
Seamounts extend from the h'ilwaukee Seamount Group northward
2,300
km
to
Meiji
Seamount
(Jackson
et
al.
,
1980). The Emperor-
Hawaiian Ridge area
is
compose? of
at least 107 identifiable
volcanoes
from
which
all
the associated topographical features
originate. These volcanoes are thought to have been produced by
the northward moveipent of the Pacific plate over a "hot spot"
with the bend at the junctior: of the Emperor-Hawaiian Ridge area
caused
by
a shifting
c?'
the
p38te
to
the northwest.
Results
from
a
variety
of
dating techninues on samples obtained from
sites
throughout-
the
Emperor-Hawaiizt- Ridge area show a pattern of
increasing
nqe
with distance
rr~m
the island of Hawaii (Dalrymple
et
al.,
1381).
This indicates that the seamounts
are
among the
oldest of topographic feature,c :Tithin the Emperor-Hawaiian Ridge
area.
The
seamounts
discussed
im
this review are Koko, Yuryaku,
and Kammu
of
the
southern ~mperor Seamounts Chain and Colahan,
C-H,
NW
Hancock,
SE
Hancock,
52?d,
Nero, and unnamed seamounts 8
to
I11
of the northern Hawaiian 'idge.
All
are situated within an
area bounded by
1st.
26"
to
36"N
and long. 174"W to
171"E
(Figure
1).
A
seamount
is
defined
as
a
more-or-less isolated elevation
of the
sea
fls,cr
appearin9 circular or elliptical in cross-
section, with
a
minimum relief of
1
km,
comparatively steep
slopes, and
a
relatively mall summit
area.
Most, if not
all,
seamounts
are
volcanic in origin (Menard, 1964).
Ridge
area
from Koko to Hancock Seamounts (hereafter designated
SE-NRR),
lie
within the mean flow of the North Pacific Current.
Results of Soviet investigations in this region indicate
a
sub-
stantial perturbance in the surface current field, apparently
produced by the seamounts (Borets, 1980). Fedosova (1974)
reported the existence
of
cyclonic and anticyclonic eddies over
the
SE-NHR
seamounts. These eddies fluctuated seasonally in
location and dimension, but apparently persisted throughout the
year.
The sea-surface temperature (SST) annually ranges from
15
to 26°C
at
Koko Seamount, 18"to 27°C near the Hancock Seamounts,
and 22" to 29°C to the south in the vicinity of seamounts
8
and
9.
Maximum
SST
usually occurs during August-September and the
temperatures
are
lowest in February-March
(Eber
et
al.,
1968).
Unfortunately,
temperature
data for the seamount summits
are
scarce,
and comparisons are complicated by the wide range in sum-
mit
elevations. Available data indicate an annual range in
sum-
mit
temperatures of
8"
to
15°C among the more northerly seamounts
(summit depths of
250
to
400
m)
from Yuryaku to
SE
Hancock. The
southern seamounts,
from
Ladd to seamount
8,
hav: shallower
sum-
mit
depths of 50 to
200
m
and
temperatures
of
14
to
24°C (Japan
Marine Fishery Resource Research Center, 1973; Japan Fisheries
Agency, 1974: Gooding, 1980).
The seamounts of the southern Emperor-northern Hawaiian
2
84

Figure
1.
The southern Emperor-northern Hawaiian Ridge
seam0
un
t
s
Besides fluctuations in the current field and
water
tempera-
ture,
seasonal changes in plankton biomass over the seamounts
have been observed in the
area
between
lat.
27" and 37"N, long.
170"E and 178"W. Soviet investigators found
areas
of
highest
plankton biomass in the spring. These
areas
were
displaced down-
current of upwelling zones in the winter-spring period, whereas
in spring-summer they
were
found near eddies. The winter-spring
conditions
were
explained relative to the intensification of the
North Pacific Current and the directional coincidence of prevail-
ing winds, whereas during spring-summer there
was
a
weakening of
this
current (Fedosova, 1974). Pontekorvo (1974) suggested
that
zones of upwelling
are
produced on opposite
sides
of
a
seamount.
These zones
are
roughly aligned with the prevailing current and
intensified during the winter. Bezrukov and Natarov (1976)
attributed
the formation of high biological productivity over the
SE-NHR
seamounts to
a
favorable abiotic regime produced by the
intense
vertical
water
circulation.
2 85

SEMOUNT
TRAWL
FISHERY
--
PAST
AND
PRESENT
The discovery of
a
bottom
trawl
fishery resource on the
SE-NHR
seamounts
was
made by
a
Soviet commercial
trawler
in
November 1967. The resource consisted primarily of pelagic
armorhead, Pentweros
',
and alfonsin,
I&.LYX
splendmns
(Figures 2 and 3). Shortly thereafter,
a
Soviet
trawl
fishery
began on the SE-NHR seamounts. From December 1969 through July
1970, Soviet trawlers harvested approximately 133,400
metric
tons
(MT) of pelagic armorhead from the seamounts (Sakiura, 1972).
This
is
the only catch data available for the Soviet
trawl
fleet
although Soviet trawlers have probably continued to fish the
sea-
mounts to the present. In 1968-69, two Soviet research
cruises
surveyed an
area
from
lat.
21" to 36'N, and long. 160"E to 165"W.
Seamounts surveyed
were
Koko,
Milwaukee
(consisting of
Kammu,
Yuryaku, and
Daikakuji
Seamounts), Hancock (refers to
NW
and
SE
Bancock Seamounts), and two unidentified seamounts. Pelagic
armorhead
was
the principal species caught on each seamount.
Total
catch of alfonsin ranged from
5
to 30 percent
at
Koko and
accounted for 25 percent
at
Milwaukee. The catch of alfonsin on
the
other seamounts
was
not given. Catches of pelagic armorhead
at
each seamount
were
found to vary diurnally. Catches would
generally increase after 1800 hours and peak just before sunrise
(Sakiura, 1972).
The Japanese seamount
trawl
fishery began in August 1969.
An initial 2-year exploratory phase defined suitable trawl
grounds and developed
markets
for the catch. Unlike the Soviets,
the Japanese have made available their
trawl
catch and effort
data, by seamount, for pelagic armorhead and alfonsin caught
during 1969-81 (Takahashi and Sasaki, 1977;
Sasaki,
unpublished
data). These data cover trawling on the following seamounts:
Koko,
Milwaukee,
Colahan,
C-HI
Hancock, and others.
Figure 4 shows the annual effort (in
trawl
hours)
at
each of
the seamounts during 1969-81. During the exploratory phase
Milwaukee
was
surveyed intensively, whereas during 1972-73 effort
was
more equitably partitioned among
all
the seamounts. Effort
during the following years (1974-81)
was
concentrated
at
Koko and
Milwaukee.
The annual catch of pelagic armorhead
is
shown in Figure 5
for 1969-81. The annual catches fluctuated widely
at
Milwaukee
during 1969-77, whereas they fluctuated
less
at
Koko, Colahan,
and Hancock. The fluctuations in catch
at
Koko and
Milwaukee
during 1969-71 and 1974-76 appear to coincide with fluctuations
in effort. Outside of these fluctuations, the catch record shows
two remarkable events. First
was
the high annual catches
at
Colahan in 1972 and Hancock in 1973 with
a
decline and modest
increase in effort, respectively. Also, the 1972 catch
at
Mil-
waukee
showed
a
large increase compared with the 1971 catch in
spite of
a
decrease in effort. The second event
was
the plummet-
ing of catches starting in 1977
at
Koko and
Milwaukee
despite
increased effort and
a
subsequent depression in catches
at
all
seamounts through 1981, regardless of changes in effort.
2 86

Figure
2.
Morphological
variation in specimens
of pelagic armorhead,
Penta ceros richardsoni.
Upper specimen repre-
sents the lean type,
middle specimen the
intermediate type, and
lower specimen the fat
tY Pe
*
Fi
.gure
3.
Specimens
of alfonsin, genus
Beryx. Upper spe-
cimen is
B.
deca-
dactvlu
s
and the
lower specimen,
B.
SDlendens.
2
87

2.20(
I
1
I
I
I
I
T----l
-
KOKO SEAMOUNT
&.----
MILWAUKEE SEAMOUNT
0
COLAHAN SEAMOUNT
0
HANCOCK SEAMOUNT
0.
.-
..
-
.
.
-..
x
-------
x
V-
-.-.-.-.-
C
-
H
SEAMOUNT
OTHERS
YEAR
Figure
4.
Yearly effort of Japanese trawl fishery for
pelagic armorhead and alfonsin at
six
seamounts within the Emperor-Hawaiian Ridge
2
88

24
r------
I
I
I
1
I
I
I
1
22
-
a-
I8
-
16
-
14
-
-
5
8.
-
'2-
-
I
V
IO
-
8-
6-
4-
2-
-
KOKO SEAMOUNT
A
MILWAUKEE SEAMOUNT
0..
-
. .
-.
.
-
.
.-
COLAHAN SEAMOUNT
x-
-
-
-
- -
-
-
-
x
C-H SEAMOUNT
v
HANCOCKSEAMOUNT
i
Rl
I
I\
I'
I
I
OTHERS
I
.--.--.--.--.--..
I
I
I
I
I
I
I
YEAR
Figure
5.
Yearly catch
of
pelagic armorhead taken by
Japanese trawlers at six seamounts within
the Emperor-Hawaiian Ridge
2
89

The annual Japanese catch
per
unit effort (CPUE) of pelagic
armorhead during 1969-81
is
shown in Figure 6. The depressed
CPUE
during 1969-71
is
probably indicative of the exploratory
nature of the fishery during this
time.
The
CPUE
for all
sea-
mounts rose during 1972-73, declined
at
most seamounts until
1978, and thereafter, remained
at
a
low level through 1981. The
general decline reflects the decline in catch over each seamount
with the exception of Hancock in 1978 and
C-H
in 1981. The
increased CPUE
at
Hancock in 1978 resulted from a 178-MT catch
during 6 trawling hours in May.
A
51-MT catch during 5
trawl-
ing hours in January and
a
99-MT catch in 7 hours in February
accounted for the increase
at
C-H
in 1981. Also the
peak
CPUE
at
Hancock in 1972 resulted from
a
1,870-MT catch in
24
trawling
hours during July.
All
these CPUEs
appear
to represent fortui-
tous increases in pelagic armorhead availability over very short
periods of
time.
pelagic armorhead for
all
seamounts combined during 1969-81.
Although CPUE steadily declined throughout 1973-79, catches
were
fairly steady during 1972-76 even if more effort
was
expended
during 1974-76 than during the previous 2 years. Although only
5.7 percent (1,236 hours)
of
the total effort (21,625 hours
throughout 1969-81) over
all
the seamounts
was
expended during
1972-73, the catch amounted to 29.8
percent
(54,927
MT)
of
a
total 184,109
MT
harvested from
all
seamounts during 1969-81. In
contrast, the total catch during 1977-81
was
only 5.8 percent
(10,679 MT) despite the fact that 48.5 percent (10,494 hours) of
the total effort
was
expended.
The highest total catch of pelagic armorhead during 1969-81
occurred
at
Milwaukee
(Figure 8).
Milwaukee
contributed 53.6
percent toward the total catch and also received the greatest
effort (48.0
percent).
Hancock contributed 8.7 percent toward
the total catch with 4.7
percent
of
the total effort.
ery
was
alfonsin. The annual catches
at
each seamount, shown in
Figure 9,
were
either
small
or
incompletely reported during
1969-75. Since armorhead
is
the primary target
species
of the
trawl fishery, catches of alfonsin, although important,
are
inci-
dental. Apparently no alfonsin catch data
were
collected and/or
published for 1974-75.
From
1976
to
1981,
all
seamounts showed
an overall catch increase with the exception of Hancock. Figure
10 also shows
a
similar
trend in CPUE with the exception again
at
Hancock. These increases in alfonsin catch and CPUE closely
coincide with the sharp decreases and sustained depression in
catch and
CPUE
of pelagic armorhead.
Figure 7 shows
a
plot of annual catch, effort, and CPUE
of
The second
species
of
importance
in the Japanese
trawl
fish-
2
90

IE
9c
BC
7(
61
5
4
A
\
\
\
'\
\
\
-
KOKO SEAMOUNT
0..
-.
.
-
.
.
-
. .
-
.
COLAHAN SEAMOUNT
X
--------
-
x
C-ti SEAMOUNT
V
v
HANCOCK SEAMOUNT
A---- -A
MILWAUKEE SEAMOUNT
--.
OTHERS
e-.
-
.
-.
-
.
-
.
YEAR
Figure
6.
Yearly catch per unit effort
of
pelagic
armorhead taken
by
Japanese trawlers at six
seamounts within the Emperor-Hawaiian Ridge
291

1969
1970
1971
1972
1973
I974
1975
I976
1977
I978
I979
1980
1981
I
..
..
.
I
I
I
I
,
I
60
50
40
30
20
10
0
10
20
30
CPUE
(
MT/
HOUR
)
CATCH
(
io3
MT
)
Figure
7.
Three-way plot
of
yearly effort, catch, and
catch
per
unit
effort of pelagic armorhead
from Japanese trawl fishery data: all
seamounts combined
292

I
HANCOCK SEAMOUNT
1
I
I
I I
1
I
I
COLAHAN SEAMOUNT
I
0
Figure 8. Three-way plot of effort, catch, and catch
per unit effort of pelagic armorhead from
Japanese trawl fishery data: years 1969-81
combined
2
93

r
3.530
I
I
2,500
j
-
KOKO SEAMOUNT
A------4
MILWAUKEE SEAMOUNT
COLAHAN SEAMOUNT
E..
-
.
. -.
x
_________
x
.-
.
,
C-H SEAMOUNT
OTHERS
V--
v
HANCOCK SEAMOUNT
1,000
-
YEAR
Figure
9.
Yearly catch
of
alfonsin taken by Japanese
trawlers
at
six seamounts within the Emperor-
Hawaiian Ridge
2
94

eo
-
KOKO SEAMOUNT
A----- A
MILWAUKEE SEAMOUNT
0
..-
. .
-
. ._ . . -. .
0
COLAHAN SEAMOUNT
V
HANCOCK SEAMOUNT
.
OTHERS
x
C-H SEAMOUNT
X
_______--
I
I
I I I I
I
1
I
1
iI
X
I
I
I
I
I
I
I
I
I
I
I
1
i
Fisure
10.
Yearly catch per unit effort
of
alfonsin
<
-
taken
by
Japanese trawlers at
six
seamounts
within the Emperor-Hawaiian Ridge
295

The largest catches of alfonsin
were
made during 1980-81,
accounting for 59.0 percent (16,558 MT) of
a
total 28,063 MT
reportedly harvested throughout 1969-81. During 1969-76 before
pelagic armorhead catches dropped
at
all seamounts,
its
contri-
bution to the total catch
(only
pelagic armorhead and alfonsin
are
considered here) 'was 98.6 percent (173,430 MT) and alfonsin
1.4
percent (2,532
MT).
For 1977-81, when catches of pelagic
armorhead remained low,
it
accounted for only 29.5 percent
(10,679
MT)
of
the
total
catch while alfonsin rose
to
70.5
per-
cent (25,531
MT).
The effort expended during the two periods
was
11,131 trawling hours
for
1969-76 and 10,494 trawling hours for
1977-81.
In
1969-81, the largest amount of alfonsin
was
taken
at
Milwaukee
,
contributing 55.4 percent
(15
,
534
MT) toward the total
catch. The effort expended there
was
48.0 percent (10,373 hours)
of
a
total
21,625 hours for all seamounts.
Like
the Soviets, the Japanese also observed diurnal fluctu-
ations in the CPUE of pelagic zs-?orhead.
Results
of
trawl
survey
work
at
Kammu,
Col-ahan, and Hancock showed two peaks
in
CPUE over
a 24-hour
day
(Kitani
and
Iguchi, 1974). The CPUE generally
peaked between 0300 to 0700 and
1600
to 1800 hours. with the
possib?-!.e
exception,
of
the exploratory phase,
it
is
assumed that
trawl
hauls
were
mostly made at night.
The inclusion of Hancock within the 200-mile U.S. fishery
conservation zone
(FCZ)
in March 1977 placed management of the
fishery
resources
there under jurisdiction of the United States.
Regulations
were
implemented and
an
annual catch
quota
for bottom
trawling and bottom longlining
of
2,000
MT
and a
limit
on effort
of
GO
vessel-days
were
set.
A
license
and
complete
catch
reports
for each
trip
are
also
required. Another
requirement
is
the
placement
of
a
U.S.
fishery observer onboard all vessels
permit-
ted to operate within the FCZ. This
latter
requirement allowed
an onsite inspection of this fishery and the opportunity
to
independently gather catch data. Japan's total yearly catch
quota
for
all
species
(except
for nonretention ones)
at
Hancock
was
1,000
MT. During 1978-82, nine
Japanese
trawlers
operated
under permit
at
Hancock, each with a U.S. observer onboard.
In
1977, Japanese
trawlers
fished Hancock only during the period
before
its
inclusion in the
FCZ.
The number of Japanese
trawlers
that fished at Hancock was one each
in
1978 and 1979, two each
in
1980 and 1981, and three during 1982.
The effort data collected by U.S. observers1
at
Hancock
during 1978-82
are
not in agreement with published Japanese data
which apparently exclude effort and catch
at
SE
Hancock during
'U.S.
foreign observer
reports
for Japanese
permit
trawling
at
Hancock Seamounts during 1978-82
are
available from Southwest
Fisheries
Center
Honolulu Laboratory, National
Marine
Fisheries
Service,
NOAA,
Honolulu,
HI
96812. They include reports on the
RY!.w2Maruu2,mMarurKitakam
.i
Maru,
and
Takachlho
I4a.u.
2 96

1978-81, thereby explaining the higher effort and catches reported
by
U.S.
observers (Figure
11).
Since no independent estimates of
catch and effort
exist
for earlier fishing conducted at Hancock,
it
is
not known whether
earlier
data
were
also excluded for
SE
Hancock. In addition, the trawler fishing
at
Hancock in 1978 used
a
different measure of effort from the conventional one,
i.e.,
elapsed
time
the
trawl
net
was
submerged. Effort was therefore
roughly adjusted using data from a comparable-sized Japanese
trawler.
These discrepancies probably account
for
the differ-
ences in effort, catch, and
CPUE
at
Hancock during 1978. The
other discrepancies for 1979-81 may solely
result
from the exclu-
sion by the Japanese of SE Hancock from the Hancock category.
Despite these discrepancies, observer data collected during
1978-82 show
a
similar sustained trend of low pelagic armorhead
catches.
5oc
4oc
-
m
a
2
30(
I
(3
-I
z
3
I-
-
I-
201
a
e
LL
W
IO
Figure
11.
I
1
I
EFFORT
\
d
I
1
1
I
0
L
1978
1979
1980
1981
1982
YEAR
-
E
3
0
I
(3
J
a
I-
\
I-
r
w
2
a
V
f
x
-
I
Yearly effort, catch, and catch per unit
effort of pelagic armorhead taken by
Japanese
trawlers
at
Hancock Seamounts
as
determined by
U.S.
foreign observers
2
97

~
i
I
400
'
/
A/
I
0-
Figure 12.
1-
-
loo
r
--
EFFORT
i
~
\
T5e
observer
data also
show
low alfonsin catches at Hancock
during 1977-82, a trend apparer?t in earlier years (Figure 9)
acccrdjry tu
a
report
Sy
Takahashi and Sasaki (1977).
obsc_<~cr
data
show
a slight increase in catch and CPUE for alfon-
sin
with
less
effort
than that. made in 1981 (Figure
12).
The 1982
Since 1976, the Southwest Fisheries Center Honolulu Labora-
tory
of
the National Marine Fisheries Service (NMFS) has made
several very limited surveys of the fishery resources of the
Emperor-Hawaiian Ridge seamounts as an adjunct to the tripartite
and
Sea
Grant investigations of the Northwestern Hawaiian Islands
(NWHI). Most
of
the effort was concentrated at Hancock. Because
of
differences in gear and technique, and the small amount of
trawling effort, data from NMFS surveys are not directly compara-
ble
with the Japanese data. The NMFS surveys, however, were
298
5
4
-
(L
3
0
.3
;
5'
25
z
a
(L
I-
I-
\
W
3
V
a
I
0
Yearly effort, catch, and catch per unit
effort of alfonsin taken by Japanese
trawlers at Hancock Seamounts as determined
by
U.S.
foreign observers

important
as
initial exploratory work and as a means for deter-
mining
species
composition of the seamount community and collect-
ing samples for life history studies.
Besides trawling,
NMFS
investigated the Hancock
summits
with
bottom handlines and traps. Bottomfishing
was
conducted primar-
ily with 10-hook and 20-hook handline rigs powered by hydraulic
gurdies. Catches consisted primarily of pelagic armorhead and
spiny dogfish,
Saualus
sp.
At
Koko, the handline catch consisted
solely of the rockfish, Ucolenus gvius. Trapping
was
also
conducted
at
Hancock using
a
variety of fish traps. Catches
were
dominated by
Ssualus
sp.
and pelagic armorhead
was
rare.
Although catches of
Saualus
sp. were
relatively high from hand-
line and trap fishing, they
were
incidental in the trawl catches.
o!l’EIER SEAHOUNT
FISHERIES
Bottom longlining
Although emphasis has been on trawl fishing, other fisheries
operate on and around the seamounts. In 1972-73, a bottom long-
line
fishery which primarily targeted alfonsin
was
initiated
at
Milwaukee.
Other
species
caught in this fishery
are
&peroslvphe
iaDOnica,
UiUu.is
zonifer,
Wlicolenus avius, and Sebastes spp.
(Sasaki,
1978). The gear
is
used to fish the
summit
and slopes
and can be
set
in
areas
inaccessible to
trawlers.
1.1.
Ikehara
(1976: personal communication) reported that bottom longlining
at
Koko yielded an unspecified quantity of
E.
zonifer
at
depths
Of 800 to
900
m.
However, no catch and effort data on the
sea-
mount bottom longline fishery
are
available. An interview with
one of the fishing
masters
revealed that catches of alfonsin and
Sebastes
spp.
were
declining by 1976 and fewer Japanese vessels
were
fishing the
area
(Suisan
Sekai,
1976). The fishing master
also stated that
a
number of Korean vessels
were
involved in this
fishery
.
Gill netting
ing in 1981 for the squid, QmmtreDhea
bartramll
(Suisan Sekai,
1981). Fishing
was
conducted in the
area
of
the Emperor Sea-
mounts. However, since no specific locations
were
given
it
is
unknown whether this fishery included the southern Emperor
Sea-
mounts. These vessels
were
reportedly catching 3 to 6
MT
per
day. Approximately 200 Japanese squid jigging vessels and
200
gill net vessels
were
also operating on the Emperor Seamounts.
Cololabis
Saira,
in the
same
area.
It
was
reported that larval
and juvenile saury
are
abundant in
waters
around the
SE-NHR
(Selitskaya, 1972).
It
was
reported that 79 Taiwan gill net vessels began fish-
..
Other Taiwan vessels
were
reported to
be
fishing for saury,
299

Coral
dragging
seamomts occurred in
1965
when Japanese fishermen found exten-
sive beds of pink coral at Milwaukee.
H.
Ozawa (1970: personal
communication) revealed that 113 MT of pink coral
was
harvested
at
Milwaukee
in
1969
by Japanese fishermen. The harvesting
method employed in this fishery involves the dragging
of
a
weighte6 object across the botton. Tangle nets attached to the
weight collect the pieces
of
dislodged coral. This fishery
apparently targets two species of pink coral: Corallium
no!'., found between 915 and 1,281
m.
The first fishery resource
to
be discovered on the SE-NHR
secundum, present at depths of 275 to 458
m,
and
Coralllum
-
sp.
Precious coral resources
are
present at seamount
10
(Grigg,
1974) and at Kancock al-thou95 ?vecious corals
at
the latter have
apparently been harvested
by
foreign fishermen prior to 1977.
Kith the advent of the 200-mile
?'sS.
FCZ, foreign harvesting of
precious
corals
and their retention through incidental catches by
foreign
tzawlers
or
longliners, under
permit
to fish Hancock,
are
prohibited.
However,
R.W.
Grigg (1983: personal communication)
has
found
'chat
20
MT
cf
precious corals
were
illegally harvested
within the
FCZ
by foreign fishermen during 1980-82. During this
time,
about
600
MT
of
precious corals were harvested throughout
the Emperor Seamounts by Japan and Taiwan. Reports from
U.S.
foreign observersZ indicate few incidental
trawl
catches of
pre-
cious corals occur
at
Kancock; all such catches are not retained.
ICEBTBYOFAWNA
OF
THE
SBAMQUNTS
During the early
1970s,
Japanese efforts to expand the
trawl
fishery for pelagic armorhead extended to various seamounts
located throughout the
MHI.
Survey
results
showed
a
distinct
change in the ichthyofauna
at
the seamounts located southeast of
Hancock. The commercial and incidental species of the SE-NHR
seamounts
were
absent from the predominantly subtropical ichthyo-
fauna on the southern seamounts (Ladd, Nerol and seamounts 8 to
11).
These
results
indicated
a
sharp demarcation of the ichthyo-
fauna coinciding with the 180th meridian (Iguchi, 1973; Japan
Marine Fishery Resource Research Center, 1973; Japan Fisheries
Agency, 1974). Seamount survey data collected by
NMFS,
plus pub-
lished information (Barsukov, 1973; Barsukov and Fedorov, 1975;
Katayama, 1975; Chen, 1980: Nakaya
et
al., 1980; Kanayama, 1981;
Borets, 1982: Dolganov, 1982; Parin and Mikhailin, 1982; Nakabo
et
al.,
1983;
Yabe, 1983) and a personal communication
(1.1.
Ikehara, 1976) have provided new records of the distribution
of
species (Table
1).
The few
species
reported from Colahan and
seamounts
10
and
11
reflect the
small
effort expended there. No
data an
C-H
seamount are available.
2See footnote
1
300

TABLE
1.
DISTRIBUTION
OF
FISH
SPECIES
BY
SEAMOUNT
Spcies Family
Ks
I%
CS
HS
SS
Ls
S9
S8
Kyctophidae
Berycidae
Berycidae
Trachichthyidae
Diretmidae
Zeidae
Centrolohidae
Apogonidae
Scorpaenidae
Moridae
MaCrOKhamphOSidae
Naneidae
Antigoniidae
Smrpenidae
Moridae
Laphiidae
Scombridae
Enthidae
Moridae
Ihwlichthyidae
Squalidae
kthylagidae
Gonostwtidae
Gonostmtidae
Astronesthidae
Chauliodontidae
Chlorophthalmidae
Macrouridae
Trachiperidae
Ogcocefialidae
Chaunacidae
Enthidae
Pleuronectidae
Platycehalidae
Callionymidae
Peristediidae
Trichiuridae
Trichiuridae
Serranidae
Chimeridae
Scorpaenidae
Scorpaenidae
Scorpaenidae
Serranidae
Moridae
Moridae
Ereuniidae
Fentacerotidae
Ser ranidae
Ser rsnidae
BBnbropsidae
Congridae
Lutjanidae
Antigoniidae
harelichthyidae
Mugilcididae
___
301
X
X
X
X
X
X
X
X
X
X
X
xxx
xxx
X
X
xxx
X
X
xxx
X
X
X
X
X
xxx
X
X X
X
X
X
X
X
X
X
X
X
X
X
X
X X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X X
X
X
X
X

TABLE
1.
DISTRIBUTION
OF
FISH
SPECIES
BY
SEAMOUNT
(continued)
Species Family
Ks
m
cs
Hs
ss
Ls
ts
s9
58
Squlidae
Squalidae
Sternoptychidae
Lut
janidae
Astronesthidae
Bothidae
Genmlidae
Gonostaratidae
Hoplichthyidae
Moridae
Myctophidae
Myctophidae
miloididae
Serranidae
SyMphobranchidae
Argentinidae
Dasyatidae
Squalidae
Trachichthyidae
Squalidae
Soor
paenidae
Trichiur idae
Moridae
Zeidae
Trachichthyidae
Carcharhinidae
Hewnchidae
Chlorophthalmidae
Triacanthidae
Bramidae
Alopiidae
Anoplopmtidae
Squalidae
Carangidae
Centrolophidae
Priacanthidae
Antigoniidae
Moridae
Squalidae
Genwlidae
Fentacerotidae
Folymixiidae
Fistulariidae
Veliferidae
Carangidae
Carangidae
Carangidae
Mullidae
Mullidae
mtidae
Carapidae
olaetodontidae
olaetodontidae
Ostraciontidae
Canthigasteridae
Balistidae
X
X
X X
X
xx
xx
xx
xx
xx
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
xx
X
xx
X
X
X
xx
X
X
X
xxx
X
X
xx
xxx
xx
X X
X
X
X
xxx
X X
X X
X
X X
X X
X
X
X X
X
302

TABLE
1.
DISTRIBUTION
OF
FISH
SPECIES
BY
SEAMOUNT
(continued)
xxx
Lutjanidae
Carangidae
X
Acanthuridae
X
Priacanthidae
X
Ser ranidae
X
Scorpenidae
X
Cheilodactylidae
X
Congr idae
X
Congr idae
X
Muraenidae
xx
Muraenidae
Serranidae
xxxxx
Carangidae
xxx
Muraenidae
X
Congr idae
X
Carangidae
X
ELelis.Lzi&i~
,
Lutjanidae
xxxx
--
mpQthQ=berndti
X
-+?=
ISeLidadumerlll
Lutjanidae
xx
Lut
janidae
xxx
Lut
janidae
X X
E--
Scorpenidae
xxx
Snboeroides-
Tetraodontidae
X
Bodlanus-
Labridae
X
Note:
KS
=
Koko
Seamount;
Ms
=
Milwaukee Seamount Group;
CS
=
Colahan
Seamount;
HS
=
Hancock
Seamounts;
SS
=
Seamounts
10
and
11;
LS
=
Ladd
Seamount; NS
=
Nero Seamounts;
S9
=
Seamount
9;
58
=
Seamount
8
Most fishes occurring on the
summit
of
northern seamounts
are
deep-water, benthic-demersal
forms.
The predominance
of
these types
is
hardly surprising since the collections
were
derived almost solely from bottom
trawls.
Some mesopelagic types
were also collected, although
it
is
uncertain whether these spe-
cies
were
collected in the
water
column above the seamount or
represent mesopelagic species which exhibit more demersal af f in-
ities.
Most fishes collected from the northern seamounts were
small
and of no commercial value. Of the 80 fish species found
only among the northern seamounts, more than
50
percent are known
to occur elsewhere within the Hawaiian archipelago. Table
1
also
shows that
9
of t.he
90
species found
at
the northern seamounts
are
distributed beyond the 180th meridian. Most of the transi-
tional
species
occurred
at
Ladd and Nero Seamounts. Two of them,
Hyperom
e
japonica and pelagic armorhead, have distributions
centered in the northern seamounts. Only one specimen of
B.
southern seamounts. The remaining seven transitional species
are
known from elsewhere in the Hawaiian archipelago.
Apart
from the transitional species, subtropical reef fishes
and members
of
the commercially important snapper-grouper complex
and two of pelagic armorhead
were
taken within the
3
03

characterize the ichthyofauna of the southern seamounts. Sea-
mounts 10 and
11
may
be
exceptions. Although these
new
results
confirm
a
distinct ichthyofaunal change near the 180th meridian,
the ichthyofauna of Ladd and Nero (and probably seamounts 10 and
11)
may be of
a
more transitional nature than originally thought.
Since most of the fishes inhabiting the northern seamounts occur
elsewhere
in
the deeper
waters
of the Hawaiian Archipelago, the
shallower
summits
and
warmer
temperatures
characteristic of
southern seamounts apparently offer an unsuitable habitat for
these species.
LIFE
HISTORY OF
TARGET
SPECIES
Pelagic
armorhead
pelagic armorhead
came
from
results
of Soviet ichthyoplankton
surveys over the SE-NHR seamounts in 1969 and 1976 (Borets,
1979). These specimens ranged from 5 to
20
mm
long and occurred
more frequently south of 33"N. The egg, larval, and juvenile
stages inhabit the surface layers and their distribution
is
sub-
ject
to the meanderings of the surface currents (Borets, 1979).
The first report of a juvenile
was
a
35-mm specimen collected
off
Cape
Horn, South
America
and
was
initially given the name
then, juveniles have been collected off
New
Zealand (Smith,
1964), from south of the Aleutian Islands (Honma and Mizusawa,
1969; Randall, 1980), and off Gough Island in the southeast
Atlantic (Borets, 1980).
Pelagic armorhead
was
first described in 1844 from
a
530-mm adult specimen
taken
in deep
water
off
Cape
Point, South
Africa (Smith, 1964). Adults
are
known elsewhere in the south-
east
Atlantic from Valdivian Seamount in the Walvis Ridge area
(Borets,
1980). In the Pacific, adults
are
known from both
hemispheres. Besides the large population inhabiting the SE-NHR
seamounts,
adults also occur
at
Mellish Bank (Takahashi and
Sasaki, 1977) and at Ladd Seamount and
Kure
Atoll (from
a
single
specimen collected
at
each) (Randall, 1980). In Japanese waters,
adults occur around the Boso Peninsula
(Abe,
1957) and off
Hachijo Island and the Ogasawara Islands (Abe, 1969;
Zama
et
al.,
1977b).
A
few adult specimens have also been collected
in
waters
along western North America
from
British Columbia (Welander
et
al.,
1957; Clemens and Wilby, 1961;
Hart,
19731, Oregon (Wagner
and Bond, 1961), and California (Follett and Dempster, 1963;
Smith, 1965). Adults and juveniles
also
inhabit
waters
south of
the
Aleutian
Islands and around the Gulf of Alaska in the north-
east Pacific (Welander
et
al.,
1957; Chikuni, 1970). In the
South Pacific, the Soviets collected five adult specimens from
one of the seamounts located on the Sala y Gomez Ridge in the
vicinity of
Easter
Island (Borets, 1980). The Japanese obtained
three large adults off the east coast of
Australia
at
Derwent
Hunter Seamount.
Distributional information on the
smallest
reported
sizes
of
Penta
cero5
knerj,
by Steindachner in 1866 (Smith, 1964). Since
304

Apparently, pelagic armorhead in the Pacific have an anti-
tropical distribution. The lowest latitudinal records are at
Kure Atoll
(lat.
28"30.82'N, long. 178"20.86'W) in the North
Pacific (Randall, 1980) and Sala y Gomez Ridge
(lat.
24"57'S,
long. 97'41'W) in the South Pacfic (Borets, 1980).
A
preliminary
effort to locate pelagic armorhead in the Hawaiian islands
(lat.
20" to 22"N)
was
unsuccessful (Okamoto, 1982). Borets (1980)
recognized two distributional centers
of
reproductive adults:
the SE-NHR seamounts and Walvis Ridge. Aside from these
areas,
"good" fishing grounds
were
reported near Hachijo Island
(Abe,
1969).
A
number of pelagic armorhead have also been caught in
oceanic waters of the northeastern Pacific by Japanese whaling
ships. These fish
were
taken
by night handlining
at
the surface
under ship's lights. They have
also
been found in the stomachs
of
sei
whales captured from this
area
(Chikuni, 1970; Sasaki,
1974). The presence of large numbers of pelagic armorhead in
sei
whale stomachs infers an epipelagic existence in these waters
since these whales
are
known to preferentially feed on surface-
dwelling fish (Chikuni, 1970).
from surface or nearsurface
waters
during June-September
(Welander
et
al.,
1957; Honma and Mizusawa, 1969; Chikuni, 1970;
Randall, 1980). Pelagic armorhead school in the surface
waters
of the northeast Pacific during daylight and nondaylight hours.
Among the SE-NHR seamounts, pelagic armorhead are commercially
taken from depths of 200 to 490
m
(Takahashi and
Sasaki,
1977).
Aggregations of pelagic armorhead have been recorded on the
slopes of seamounts
at
the 800- to 900-m depth (Sakiura,
1972;
Borets, 1980). Chikuni (1970, 1971) suggested that the horizon-
tal
and
vertical
distribution of pelagic armorhead
is
correlated
with
a
certain temperature range.
He
surmised that the absence
of pelagic armorhead during northeast Pacific winters indicated
a
lower tolerance
limit
of 5"C, and that their year-round occur-
rence on the SE-NHR seamounts and during
summer
in the northeast
Pacific suggested an upper
limit
of
15"
to 20°C. Chikuni sug-
gested
a
preferred range of 8"to 15°C and reasoned that their
absence on the Emperor Seamounts north of Koko (depths of 1,000
m
or
more)
and on Hawaiian Ridge seamounts
east
of
the 180th
meridian (shallow summits)
was
due to intolerably low and high
temperatures,
respectively.
diurnally on the seamounts. The Soviets report that this
is
due
to
a
vertical migration upwards from the summit
as
daylight
approaches and
a
descent to the
summit
at
dusk. The fish remain
on the
summit
during darkness and in the upper water layers (80-
to 100-m depth) during daylight (Sakiura, 1972). Barnett3
reported
a
correlation between poor night catches and shipboard
Pelagic armorhead in the northeast Pacific
are
known only
As
stated
earlier,
the catches
of
pelagic armorhead vary
3See footnote
1,
specifically
W.B.
Barnett, 1981, Southwest Fish-
eries
Center Administrative Report H-81-9.
305

fish finders showing concentrations of fish (presumed to
be
pelagic armorhead)
at
levels either above
or
beyond the summit.
A
variation of the hypothesis reported by
Sakiura
was
proposed by
Kitani and Iguchi (1974). They agreed that the fish
rise
off the
summit
during daylight, but they also maintain that the fish
descend
past
the
summit
during the night. Consequently,
it
was
felt
these fish
pass
through the
summit
level
twice
during the
night: once after dusk and again before dawn. Both