NOAA Technical Memorandum NMFS-AFSC-40

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Alaska Fisheries Science Center

May 1994

Relative Abundance of Gulf of Alaska

Sablefish and Other Groundfish Based

on the Domestic Longline Survey, 1989

by

M. F. Sigler and H.H. Zenger, Jr.
NOAA Technical Memorandum NMFS

The National Marine Fisheries Service's Alaska Fisheries Science Center

uses the NOAA Technical Memorandum series to issue informal scientific and

technical publications when complete formal review and editorial processing

are not appropriate or feasible. Documents within this series reflect sound

professional work and may be referenced in the formal scientific and technical

literature.

The NMFS-AFSC Technical Memorandum series of the Alaska Fisheries

Science Center continues the NMFS-F/NWC series established in 1970 by the

Northwest Fisheries Center. The new NMFS-NWFSC series will be used by

the Northwest Fisheries Science Center.

This document should be cited as follows:

Sigler, M. F., and H. H. Zenger, Jr. 1994. Relative abundance of Gulf

of Alaska sablefish and other groundfish based on the domestic

longline survey, 1989. U.S. Dep. Commer., NOAA Tech. Memo.

NMFS-AFSC-40, 79 p.

 

Reference in this document to trade names does not imply endorsement by

the National Marine Fisheries Service, NOAA.
by

M. F. Sigler and H.H. Zenger, Jr

May 1994

NOAA Technical Memorandum NMFS-AFSC-40

Relative Abundance of Gulf of Alaska

Sablefish and Other Groundfish Based

on the Domestic Longline Survey, 1989

U.S. DEPARTMENT OF COMMERCE

Ronald H. Brown, Secretary

National Oceanic and Atmospheric Administration

D. James Baker, Under Secretary and Administrator

National Marine Fisheries Service

Rolland A. Schmitten, Assistant Administrator for Fisheries

1 2

1

2

Auke Bay Laboratory

Alaska Fisheries Science Center

11305 Glacier Highway

Juneau AK 99801-8626

 Resource Assessment and Conservation Engineering Division

Alaska Fisheries Science Center

7600 Sand Point Way N.E., BIN C-15700

Seattle, WA 98115-0070
This document Is available to the public through:

National Technical Information Service

U.S. Department of Commerce

5285 Port Royal Road

Springfield, VA 22161
Notice to Users of this Document 

This document is being made available in .PDF format for the convenience of users; however, the 

accuracy and correctness of the document can only be certified as was presented in the original hard 

copy format. 

iii

ABSTRACT

The Alaska Fisheries Science Center has conducted an

annual longline survey of sablefish (Anoplopoma fimbria) and

other groundfish in the Gulf of Alaska since 1987. This

survey replicates as closely as practical the Gulf of Alaska

portion of a Japan-U.S. cooperative longline survey conducted

from 1979 to 1994 and also samples gullies not sampled during

the cooperative longline survey. In 1989, 73 stations were

sampled from 26 June to 12 September. Each day, 16 km of

groundline containing 7,200 hooks baited with squid was set

from the chartered fishing-vessel Ocean Prowler.

Sablefish relative population numbers (RPN) on the upper

continental slope decreased significantly: 18% from 1988 to

1989. Most of the decrease was observed in the western and

central areas of the Gulf of Alaska; the RPN remained -about

the same in the eastern areas. The strong 1984 year class

expected to recruit in 1989 was not apparent in the survey

results, nor was there evidence for later strong year

classes. The rougheye (Sebastes aleutianus)- and shortraker

(S. borealis) rockfish RPN increased 35% from 1988 to 1989;

this increase was not statistically significant. The

thornyhead [Sebastolobus alascanus) RPN increased.

significantly (77%). 

 Preceding Page Blank 
THIS PAGE INTENTIONALLY LEFT BLANK
V

CONTENTS

INTRODUCTION . . . . . . . . . . .

METHODS . . . . . . . . . . . . . .

Vessel and Gear . . . . . . .

Survey Area and Operations . .

Data Collection . . . . . .

Analytical Method: . . . . . .

ANALYSIS OF THE CATCH . . . . . . .

Sablefish . . . . . . . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

. . . . .

Rougheye and Shortraker Rockfish . . . .

Thornyheads . . . . . . . . . . . . . .

Other Species . . . . . . . . . . .

Year-Class Strength of Sablefish . . . .

Possible Reasons for Changes in Sablefish RPN .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

Relationship Between Changes in Sablefish,

Thornyhead, and Grenadier RPNs . .

ACKNOWLEDGMENTS . . . . . . . . . . . . . . .

CITATIONS . . . . . . . . . . . . . . . . . .

TABLES . . . . . . . . . . . . . . . . . . .

FIGURES . . . . . . . . . . . . . . . . . . .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

. .

 Preceding Page Blank
From 1979 to 1994, Japan and the United States annually

conducted a cooperative longline survey covering the upper

continental slope of the eastern Bering Sea, the Aleutian

Islands, and the Gulf of Alaska. The research has supplied

information needed to estimate the abundance of sablefish

(Anoplopoma fimbria) and other groundfish species (Lowe and

Sigler 1989; Yoshimura and Sasaki 1989; Clausen and Sigler in

press).

Since 1987, the National Oceanic and Atmospheric

Administration's (NOAA) Alaska Fisheries Science Center has

conducted an additional annual longline survey designed to

continue the time series of the Gulf of Alaska portion of the

Japan-U.S. cooperative longline survey. The domestic

longline survey covers the same stations, (Fig. 1) and season,

and uses similar sampling gear as used on the Gulf of Alaska

portion of the cooperative longline survey. The primary

purpose of the domestic longline survey is to determine

annually the relative abundance and size composition of

sablefish, shortspine thornyhead (Sebastolobus alascanus),

rougheye rockfish (Sebastes aleutianus), and shortraker

rockfish (Sebastes borealis) in the Gulf of Alaska.

This report presents results of the 1989 domestic

longline survey and updates the 1987 and 1988 surveys (Sigler

and Zenger 1989; Zenger et al. 1992). The analysis of

sablefish for the 1989 Japan-U.S. cooperative longline

survey is reported in Fujioka (1991) for the Gulf of Alaska

and in Lowe (1991) for the eastern Bering Sea and Aleutian

Islands. A comparison of the catch rates of sablefish

between the domestic and cooperative longline surveys will be

reported in a separate document (Zenger 1992).

METHODS

Vessel and Gear

The survey vessel was the chartered fishing vessel

Ocean Prowler (47 m, 155 ft). Each day, 16 km (8.6 nautical

miles) of groundline was set. The groundline consisted of

160 sections called skates;

long and included 45 Mustad1

each skate was 100 m (55 fathoms)

size 13/0 circle hooks spaced

2 m (6.5 ft) apart. The groundline was weighted with 3.2-kg

(7-1b) lead balls snapped on at the end of every skate. Each

hook was baited by hand with chopped squid (Illex spp.) at a

rate of about 5.5 kg (12.0 lb) per 100 hooks.

1

Reference to trade names does not imply endorsement by the National

Marine Fisheries Service, NOAA.
2

Bait type, gangion and becket line strength, and hook

brand differed between 1987 and 1988-1989. Details and

reasons for the changes are described in Zenger et al.

(1992). Because of these differences, the 1987 survey was

considered experimental and is not included in the 1988-1989

time series.

Survey Area and Operations

The survey area extends from Islands of Four Mountains

(lat. 52°45'N, long. 170°W) eastward to Dixon Entrance

(Fig. 1) and covers the upper continental slope and selected

gullies. The area of the sablefish commercial fishery

generally corresponds to the upper continental slope and

gullies with bottom depths greater than 400 m, such as

Spencer Gully. Adult sablefish also inhabit shallower

gullies (bottom depths 200-400 m) not targeted during the

commercial fishery. Sampling of gullies has expanded each

year (1987-89) of the domestic longline survey to increase

the amount of adult sablefish habitat sampled (Table 1).

With this expansion, the survey area in 1989 generally

corresponded to the area inhabited by adult sablefish.

Sampled depths ranged from about 200 to 1,000 m, although at

some stations depths less than 150 m were sampled.

The survey was from 26 June to 12 September 1989.

Seventy-three stations were sampled--45 along the upper

continental slope, 27 in gullies,

shelf2. and 1 on the continental

The sampling gear was set from shallow to deep and

usually was retrieved in the same order. Set and retrieval

began about 0630 and 0930 hours, respectively, and retrieval

was completed about 2000 hours.

11 hours.

Soak time ranged from 3 to

Data Collection

Fish species and hook condition were recorded during

sampling gear retrieval. Hook condition was classified as

baited, unbaited, or ineffective. Ineffective hooks were

missing, broken, or tangled. Time and depth were recorded

when every fifth skate was hauled aboard.

1

The 45 stations on the upper continental elope correspond to station

numbers 62-86, 88-102, and 104-108 of the Japan-U.S. cooperative longline

survey (Yoshimura and Sasaki 1989). Gully station 26 corresponds to

station 87 of the cooperative longline survey. Shelf station 42

corresponds to station 103 of the cooperative longline survey and is on

the continental shelf off Baranof Island. The remaining 26 gully

stations are additional to the original 47 stations of the cooperative

longline survey.
3

Sablefish, Pacific cod (Gadus macrocephalus), arrow-tooth

-flounder (Atheresthes stomias), rockfish (Sebastes spp.), and

thornyhead (Sebastolobus spp.) fork lengths were measured.

Vent length--the length from snout to vent (SV)--was measured,

for grenadiers (Macrouridae). Sablefish and Pacific cod were

sorted into eight depth strata (Table 2) for measuring length

and determining sex, whereas other species were not.

Analytical Methods

The number of fish caught per skate (catch per unit

effort, CPUE) was calculated by species for each stratum at a

station. The CPUE for each stratum of a station was

multiplied by the area of the stratum (Table 3) to compute

relative population numbers (RPN, an index of relative

abundance in numbers) (Gulland 1969; Quinn et al. 1982;

Sasaki 1985). The resultant values were averaged within the

area to obtain an RPN for each stratum and area. Relative

population numbers were calculated only for depths

201-1,000 m because this range generally corresponds to the

depths sampled. Relative population numbers were not

calculated for shallower depths because depths less than

200 m were sampled at only some stations (see Survey Area and

Operations).

Relative population number weighted length frequencies

(RPN LF) were computed for depths 201-1,000 m to examine the

size compositions of the species. Catch per unit effort

weighted length frequencies (CPUE LF) of sablefish were

computed for depths 101-200 m for evidence of relatively

strong year classes. Length compositions for depths

101-200 m from previous Japan-U.S. cooperative longline

surveys were used to document the relatively strong 1977 and

1980 year classes of sablefish (Sigler and Fujioka 1988). A

CPUE LF was calculated instead of an RPN LF because RPNs were

not estimated for these depths for the reason noted in the

previous paragraph. Relative population weights (RPW, an

index of relative abundance in weight) were computed from the

RPN LF and length-weight equations to assess relative

biomass. Computation of the RPN, RPW, and length

compositions is described in more detail in Sigler and Zenger

(1989)3.

3

All stations established by the cooperative longline survey (stations

1-47) previously were classified as upper continental slope stations,

although this classification was incorrect for two stationa. These two

stations, 26 in Amatuli Gully and 42 off Baranof Island, have been

reclassified now that the domestic longline survey extensively samples

gully areas. As a result, the RPNs and RPWs for 1980 presented in Zenger

and Sigler (unpubl. manuscr.) differ slightly from those presented in

this report:
4

The RPNs apply only to the area surveyed and represent

only the portion of each species' population that is resident

in the survey area. For sablefish, rougheye and shortraker

rockfishes, and shortspine thornyheads, the survey area

covers most of the area inhabited by the adults of these

species (M. Sigler, unpubl. data) and therefore generally

represents the adult fraction of these species' populations.

In contrast, the area inhabited by Pacific cod, Pacific

halibut (Hippoglossus stenolepis), rockfish species other

than rougheye and shortraker rockfishes, grenadiers, and

arrowtooth flounder is broader than the survey area. Thus,

the RPNs do not reflect the abundance of these species as a

whole.

As noted earlier, fewer gullies were sampled in 1988

than in 1989 (Table 1). Therefore, to compare gulf-wide

abundance interannually, overall RPNs are restricted to

gullies sampled in both 1988 and 1989 and the upper

continental slope. The area sampled in 1988 was 88% of the

size sampled in 1989. Unlike overall 1989 RPN, overall 1989

length compositions are not restricted to areas also sampled

in 1988, because their shape was similar to overall length

compositions that included all areas sampled in 1989.

Relative population numbers for the upper continental

slope in 1988 and 1989 were compared to determine whether

differences between years were statistically significant.

The null

where i

hypothesis tested was that RPNi,j

= 1988, i' = 1989, j = species. A

- RPNi',j = 0,

s in Sigle: and

Fujioka (1988), the bootstrap method (Efron 1982; Efron and

Tibshirani 1986) was used to compare RPNs. Only the RPNs for

the upper continental slope for each species were compared

because of the limited number of gullies sampled in 1988.

ANALYSIS OF THE CATCH

Sablefish

Sablefish abundance for the upper continental slope

decreased 18% from 1988 to 1989 (Table 4); this drop in RPN

was statistically significant (p c 0.001). Abundance

decreased only for the western and central Gulf of Alaska,

dropping 46, 27, and 13% for the Shumagin, Chirikof, and

Kodiak International North Pacific Fisheries Commission's

(INPFC) statistical areas, respectively, and remained about

the same for the Yakutat and Southeastern INPFC areas. The

RPN for the four gullies sampled in both 1988 and 1989

(Shumagin Gully, Shelikof Trough, Amatuli Gully, and Spencer

Gully) increased slightly from 1988 to 1989. The overall RPN

combining these gullies and the upper continental slope
5

decreased slightly (10%) from 668,186 in 1988 to 601,517 in

1989.

Mean length increased from 1988 to 1989 in several areas

(Fig. 2): females and males in the Kodiak (Fig. 2c) and

Yakutat INPFC areas (Fig. 2d), Shumagin Gully (Fig. 2g),

Shelikof Trough (Fig. 2h), Amatuli Gully (Fig. 2i), and

Spencer Gully (Fig. 2j). This increase in mean length was

due to an increase in the proportion of relatively large

fish. In the remaining INPFC areas--females and males in

Shumagin (Fig. 2a), Chirikof (Fig. 2b), and Southeastern

(Fig. 2e) --length compositions were similar in shape and

location in 1988 and 1989. Overall, from 1988 to 1989, the

number of relatively small fish decreased for females and was

similar for males, and the number of relatively large fish

increased for both females and males (Fig. 2k).

From 1988 to 1989, RPW decreased (12%) for the upper

continental slope and increased (8%) for the four gullies

sampled both years (Table 5). The percentage changes differ

'from those for the corresponding RPNs because of an increased

proportion of larger sablefish from 1988 to 1989 (i.e.,

although there were fewer sablefish in 1989 than in 1988,

they were larger; therefore, the RPW did not decrease as much

as the RPN).

There was no evidence from the length compositions for

101-200 m of any upcoming strong year classes in 1985 or

later. Length-at-age distributions for sablefish in the Gulf

of Alaska sampled previously in the cooperative longline

survey showed age-4 males were mostly 46-54 cm fork length

(FL) (mean 51.7 cm) and age-4 females 46-58 cm FL (mean 54.6

cm) (Clausen and Sigler in press). There were no distinct

modes at or below these length ranges in 1988 or 1989 (Fig.

3) except for a mode about 54 cm FL in 1988 for both males

and females in the Yakutat INPFC area (Fig. 3d).

The length compositions for 101-200 m changed somewhat

from 1988 to 1989, probably due to a year class originating

before 1985. From 1988 to 1989, the proportion of fish

55-65 cm FL often decreased (Shumagin (Fig. 3a) and Yakutat

INPFC areas (Fig. 3d)), whereas the proportion of fish

60-70 cm FL often increased (Chirikof (Fig. 3b) and Yakutat

INPFC areas (Fig. 3d), Shumagin Gully (Fig. 3f) and Shelikof

Trough (Fig. 3g)). In the Shumagin and Chirikof INPFC areas

and in Shelikof Trough and Shumagin Gully, the FL mode

progressed from 57-59 cm in 1988 to 60-62 cm in 1989 for

males, and from 59-61 cm to 63 cm for females. Based on the

length-at-age data from the cooperative longline survey (Fig.

4), the modes represent 4- or 5-year-old fish in 1988 (1984

or 1983 year class) and 5-year-old fish in 1989 (1984 year

class).
6

Rougheye and Shortraker Rockfish

The combined RPN for rougheye and shortraker rockfish on

the upper continental slope increased 35% from 1988 to 1989

(Table 6); however, this increase in the RPN was not

statistically significant (p = 0.064). The PPN increased in

all areas of the upper continental slope. The RPN for the

Southeastern INPFC area increased the most (92%).

The number of rougheye and shortraker rockfish in

gullies is relatively unimportant compared to the number on

the upper continental slope and accounted for only 9% of the

total rougheye and shortraker rockfish PPN in 1989. A

notable change in population size was observed for Shelikof

Trough, where abundance increased 105%. This change is

suspect, however, because the RPNs are based on catches of

only 38 rockfish in 1988 and 85 rockfish in 1989. (The RPN

appears relatively large because of the large area of

Shelikof Trough.)

The combined RPW for rougheye and shortraker rockfish

for the upper continental slope also increased markedly from

1988 to 1989 (Table 7). The increase is due to increased

rougheye rockfish RPW (81%). Shortraker rockfish RPW

remained about the same.

From 1988 to 1989, the length composition was similar

for rougheye rockfish (Fig. 5) and dissimilar for shortraker

rockfish (Fig. 6a). The change for shortraker rockfish was

due to differences in the length compositions at lengths less

than 55 cm FL. (At larger sizes, the length compositions

were similar.) A distinct mode (composed of two smaller

modes) at 35-50 cm FL was observed in 1988, but not in 1989.

This mode and subsequent change is attributable to the length

compositions observed in the Shumagin INPFC area (Fig. 6b).

Thornyheads

Thornyhead abundance on the upper continental slope

increased 77% from 1988 to 1989 (Table 8); this increase in

the RPN was significant (p < 0.001). The gully RPN accounted

for 21% of the total RPN in 1989. Thus, the gully fraction

is an important part of the thornyhead population. In 1989,

relatively large numbers of thornyheads were found in Amatuli

Gully, Yakutat Valley, Ommaney Trench, and Dixon Entrance.

Of these areas, only Amatuli Gully was sampled in both 1988

and 1989. The RPN increased 95% in Amatuli Gully.

Like the RPN, the thornyhead RPW for the upper

continental slope increased markedly (69%) (Table 9). The

RPW increased in all areas of the upper continental slope and
7

also in Amatuli Gully. The size composition was similar in

1988 and 1989 (Fig. 7). The mean length decreased slightly.

Other Species

As mentioned in the Analytical Methods section, only an

unknown fraction of the following species' populations was

sampled. Thus, these results do not represent the

populations as a whole.

Grenadier abundance on the upper continental slope

increased 87% from 1988 to 1989 (Table 10); this increase in

the RPN was significant (p < 0.001). Greatest increases were

in the Shumagin, Chirikof, and Kodiak areas, accounting for

96% of the change. In contrast to the large numbers of

grenadier on the upper continental slope, the number in the

gullies was trivial, less than 1% of the total grenadier RPN.

The proportion of giant grenadiers (Albatrossia

pectoralis) shorter than 31 cm SV increased from 1988 to 1989

(Fig. 8), and, as a result, the mean length decreased 1 cm.

This change was apparent in the Shumagin and Chirikof areas,

but not in the remaining INPFC areas of the upper continental

slope. Unlike giant grenadiers, the length composition for

popeye grenadier (Coryphaenoides cinereus) was similar from

1988 to 1989 (Fig. 9). (Popeye grenadier were caught

primarily in the Kodiak, Yakutat, and Southeastern INPFC

areas.)

Pacific cod abundance on the upper continental slope

decreased 28% from 1988 to 1989 (Table 11); this change in

the RPN was not statistically significant (p = 0.182).

Abundance decreased in all INPFC areas of the upper

continental slope except the Kodiak area, where abundance

remained about the same.

The gully fraction was an important part of the sampled

Pacific cod population, 82% of the total RPN for 1989. The

most important area was Shelikof Trough, which comprised 76%

of the total RPN in 1989. The RPN for sampled gullies

decreased 13% from 1988 to 1989 (Table 11).

The length composition was similar in 1988 and 1989,

except the proportion of females at 65-77 cm FL increased

(Fig. 10). The mean length increased 1 cm as a result of

this change. The additional females at 65-77 cm FL were

apparent only in Shelikof Trough (Fig., 10b).

Pacific halibut abundance on the upper continental slope

increased 15% from 1988 to 1989 (Table 12); this change in

the RPN was not significant (p = 0.366). The RPN increased

in the Shumagin and Chirikof INPFC areas, remained about the
8

same in the Kodiak INPFC area, and decreased in the Yakutat

and Southeastern INPFC areas. The gully fraction was an

important part of the sampled Pacific halibut population, 73%

of the total Pacific halibut RPN in 1989. The RPN for

gullies sampled both years was similar.

Arrowtooth flounder abundance for the upper continental

slope increased 13% from 1988 to 1989 (Table 13); this

increase in the RPN was not significant (p = 0.400). The RPN

increased in the Shumagin and Kodiak INPFC areas, remained

about the same in the Chirikof and Southeastern INPFC areas,

and decreased in the Yakutat INPFC area. The gully fraction

was an important part of the sampled arrowtooth flounder

population, 69% of the total arrowtooth flounder RPN in 1989.

The arrowtooth flounder size composition for 1988 was

bimodal with modes at 55 and 70 cm FL (Fig. 11a). In 1989,

the number of arrow-tooth flounder 55-70 cm FL increased and a

single mode at 58 cm FL was observed. Mean length increased

from 59.6 to 62.3 cm FL from 1988 to 1989. The change in the

size composition was due to increased numbers of 55-70 cm FL

fish in the Shumagin, Chirikof (Fig. 11b), Kodiak, and

Yakutat INPFC areas, Amatuli Gully, and a shift in the mode

from 55 to 59 cm FL in Shelikof Trough (Fig. 11c).

Skate abundance on the upper continental slope increased

14% from 1988 to 1989 (Table 14); this increase in RPN was

not significant (p = 0.715).

population was important,

The gully fraction of the skate

86% of the total skate RPN in 1989.

Two gullies (Shelikof Trough and Amatuli Gully) accounted for

68% of the total skate RPN in 1989. The RPN increased 77% in

Shelikof Trough and decreased 21% in Amatuli Gully.

Forty-seven additional species (or species groups) were

caught during the survey (Table 15). They were a minor

component of the catch: less than 2% of the total RPN in

1989.

Year-Class Strength of Sablefish

There was no evidence from 1988 or 1989 length

compositions for the 101-200 m depth stratum of a strong year

class of sablefish originating in 1985 or later (Fig. 3a-i).

These length compositions indicate a distinct, though not

necessarily strong, year class originating in 1983 or 1984.

Previous evidence for a strong 1984 year class is conflicting

(Clausen and Sigler in press). Supporting information

includes an observed abundance of age-l sablefish in the

inside waters of Southeast Alaska in 1985 (Fujioka 1987), and

length compositions from the 1986 trawl survey of the eastern

Bering Sea (McDevitt 1987), the cooperative longline survey

in 1986-87 (Sigler 1987, 1989), and the domestic longline
9

survey in 1987 (Sigler and Zenger 1989). More recent

evidence does not support the presence of a strong 1984 year

class and includes length compositions from the 1987 trawl

survey in the eastern Bering Sea (McDevitt 1988) and the

cooperative longline survey in 1988 (Clausen and Sigler in

press) and sampling in inside waters of Southeast Alaska in

1988 (Bracken 1988).

Further evidence contrary to the presence of a strong

1984 year class is the decrease from 1988 to 1989 in the

numbers of relatively small females and the absence of change

in the numbers of relatively small males in the length

compositions for 201-1,000 m (Fig. 2k). These observations

indicate the lack of substantial recruitment to the upper

continental slope in 1989. Previous strong year classes in

1977 and 1980 fueled sharp jumps in sablefish abundance in

1980-82 and 1984-85, respectively (Sigler and Fujioka 1988),

which led to the expectation that the 1984 year class would

primarily recruit to the upper continental slope in 1989

(Sigler 1989). The lack of substantial recruitment in 1989

indicates that the 1984 year class is not strong. Further,

the absence of substantial recruitment to replace fish lost

to fishing and natural mortality probably accounts for the

decline in sablefish abundance from 1988 to 1989.

Possible Reasons for Changes in Sablefish RPN

The number of relatively large fish increased from 1988

to 1989 (Fig. 2k), perhaps due to growth in length or

migration of sablefish into the Gulf of Alaska. A recent

migration study concludes that a nontrivial number of

sablefish migrate in and out of the Gulf of Alaska each year

(Heifetz and Fujioka 1991). A similar unexplained increase

in the number of relatively large sablefish was observed in

1985 (Fujioka 1987).

The Shumagin INPFC area RPN decreased sharply from 1988

to 1989. There is some concern that the commercial fishery,

which was in progress at the time of the survey, may have

depressed survey catch rates. A "season effect" is unlikely

to account for the entire drop because the fishery and survey

also co-occurred in the Shumagin INPFC area in 1988 (Table

16) and because the RPN also dropped sharply in the adjacent

Chirikof INPFC area, where most commercial fishing finished

more than 4 weeks before the 1989 survey began.

Relationship Between Changes in Sablefish,

Thornyhead, and Grenadier RPNs

Grenadier RPN nearly doubled from 1988 to 1989. Their

catch rates (Fig. 12) increased primarily in areas where

sablefish catch rates declined (Fig. 13), indicating 'that the
10

two changes are related. One scenario is that as sablefish

numbers decreased, the number of baited hooks available to

grenadiers increased. (We believe that sablefish can

outcompete grenadiers for baited hooks, although this

hypothesis has not been tested.) Under this scenario, the

increase in the grenadier RPN reflects the increased

availability of baited hooks and not a change in the number

of grenadiers in the survey area. Another scenario is that

grenadiers, whose range extends deeper than the surveyed

depths, moved upslope into the survey area as sablefish

abundance decreased. This theory is reasonable because the

distance to move upslope is relatively short--less than

several kilometers. Under this scenario, the number of

grenadiers within the survey area increased.

Thornyhead RPN also increased from 1988 to 1989; again,

the change may reflect the decrease in sablefish abundance.

Thornyhead RPN increased in all areas of the Gulf of Alaska

(Table 8), whereas sablefish RPN decreased only in the

western and central areas of the gulf (Table 4); thornyhead

catch rates generally increased where sablefish catch rates

declined (e.g., stations 2-16, especially at depths greater

than 401 m; stations 37-40, depths less than 400 m)

(Fig. 14). Unlike grenadiers, however, the increased numbers

of thornyheads are not due to immigration because the survey

generally covers the adult thornyhead range in the Gulf of

Alaska. Instead, increased availability of baited hooks due

to decreased sablefish numbers may be the cause of the

increased thornyhead RPN.4

Rockfish RPN also increased from 1988 to 1989. The

increased rockfish RPN is due primarily to increased catch

rates at stations 34-38 (Yakutat INPFC area) at depths

201-400 m and stations 39-47 (Southeastern INPFC area) at

depths 201-800 m (Fig. 15). These increased rockfish catches

are not related to decreased sablefish catches. Further, the

survey area generally covers the extent of rougheye and

shortraker rockfish habitat in the Gulf of Alaska; thus, the

changes in RPN are probably not because of immigration.

The increases in the grenadier and thornyhead RPN

(Tables 8, 10) were statistically significant, whereas the

RPN increases for rockfish (Table 7) were not. Thus the

4

We assume that sablefish can outcompete grenadiers, thornyheads, and

rockfish for baited hooks, but do not know among these latter three

species which is the best competitor. In this discussion, we are

assuming that they are equal competitors, thus implying that increased

numbers of baited hooks will result in increased RPN for all three

species.
11

change in the rockfish RPN may be due to inherent variability

in the index rather than a real change in abundance.

Alternatively, the increased RPN for grenadiers,

thornyheads, and rockfish may be due to recruitment of young

fish. The lack of change in the length compositions for

thornyhead and rockfish (except for shortrakers in the

Shumagin INPFC area) (Figs. 5-7) indicates that recruitment

was not responsible for the RPN changes for these two

species. For giant grenadiers, the proportion of fish

shorter than 31 cm SV increased (Fig. 8), indicating that

recruitment might be responsible for the increased RPN. The

likelihood of this scenario cannot be differentiated from the

other two scenarios previously discussed for grenadiers,

however.

The apparent connection between changes in the

grenadier, thornyhead, and sablefish RPN indicates the danger

of simply, interpreting longline catch rate changes as

reflecting real changes in abundance. The previous

discussion indicates that the changes in grenadier and

thornyhead RPN do not reflect changes in their abundance.

Experiments with hook timers, electromechanical devices which

measure the arrival time of fish to the hook, imply that

sablefish longline catch rate is a linear function of

sablefish density (Sigler 1993). Similar experiments could

be completed to examine the functional form of this

relationship for grenadiers and thornyheads.

ACKNOWLEDGMENTS

We thank the crews of the FV Prowler and FV Ocean

Prowler and thank their experienced and extraordinarily

helpful skipper Jerry Kennedy, captain of FV Prowler in

1987-1988 and of FV Ocean Prowler in 1989. We also thank

Dave King and his crew at the Net Loft for building the

fishing gear.
12

CITATIONS

Bracken, B. E. 1988. Report to the Board of Fisheries:

1988 Southeastern-Yakutat groundfish fisheries. Unpubl.

manuscr., 40 p. Alaska Dep. Fish and Game, Div. of

Commer. Fish., P.O. Box 667, Petersburg, AK 99833.

Clausen, D. M., and M. F. Sigler. In press. Relative

abundance of sablefish in the Gulf of Alaska, based on

the Japan-U.S. cooperative longline survey, 1988. In

T. K. Wilderbuer (editor), Condition of groundfish

resources of the Gulf of Alaska in 1989. NOAA Tech.

Memo. NMFS F/NWC-000.

Mar. Fish. Serv.,

Alaska Fish. Sci. Cent., Natl.

NOAA, 7600 Sand Point Way NE, Bin

C15700, Seattle, WA 98115-0070.

Efron, B. 1982. The jackknife, the bootstrap, and other

resampling plans.

Math. 38.

CBMS-NSF Regional Conf. Ser. Applied

Soc. Ind. and Appl. Math., Philadelphia,

92 p.

Efron, B., and R. Tibshirani. 1986.

standard errors,

Bootstrap methods for

confidence intervals, and other

measures of statistical accuracy. Stat. Sci. 1:54-77.

Fujioka, J. T. 1987. Sablefish. In R. L. Major (editor),

Condition of groundfish resources of the Gulf of Alaska

as assessed in 1986, p. 51-83.

Tech. Memo.

U.S. Dep. Commer., NOAA

NMFS F/NWC-119.

Natl. Mar. Fish. Serv.,

Alaska Fish. Sci. Cent.,

Bin C15700,

NOAA, 7600 Sand Point Way NE,

Seattle, WA 98115-0070.

Fujioka, J. T. 1991. Sablefish. In Stock assessment and

fishery evaluation report for the 1992 Gulf of Alaska

groundfish fishery, section 4. N. Pac.

Council,

Fish. Manage.

P.O. Box 103136, Anchorage, AK 99510.

Gulland, J. A. 1969. Manual of methods for fish stock

assessment. Part 1. Fish population analysis. FAO,

Rome. St. Paul's Press Ltd., Malta, Italy, 154 p.

Heifetz, J., and J. T. Fujioka. 1991. Movement dynamics of

tagged sablefish in the northeastern Pacific. Fish.

Res. 11:355-374.

Lowe, S. A. 1991. Sablefish. In Stock assessment and

fishery evaluation report for the groundfish resources

of the Bering Sea/Aleutian Islands region as projected

for 1992, section 8. Pac. Fish. Manage. Council, P.O.

Box 103136, Anchorage, AK 99510.
13

Lowe, S. A., and M. F. Sigler. 1989. Relative abundance of

sablefish in the eastern Bering Sea and Aleutian Islands

region based on the 1988 Japan-U.S. cooperative longline

survey. Unpubl. manuscr., 26 p. Alaska Fish. Sci.

Cent., NMFS, NOAA, 7600 Sand Point Way NE, BIN C15700,

Seattle WA 98115-0070.

McDevitt, S. A. 1987. Sablefish. In R. G. Bakkala and

J. W. Balsiger (editors), Condition of groundfish

resources of the eastern Bering Sea and Aleutian Islands

region in 1986, p. 97-115. U.S. Dep. Commer., NOAA

Tech,. Memo. NMFS F/NWC-117. Alaska Fish. Sci. Cent.,

Natl. Mar. Fish. Serv., NOAA, 7600 Sand Point Way NE,

Bin C15700, Seattle, WA 98115-0070.

McDevitt, S. A. 1988. Sablefish. In R. G. Bakkala

(editor), Condition of groundfish resources of the

eastern Bering Sea and Aleutian Islands region in 1987,

p. 101-115. U.S. Dep. Commer., NOAA Tech. Memo. NMFS

F/NWC-139. Alaska Fish. Sci. Cent., Natl. Mar. Fish.

Serv., NOAA, 7600 Sand Point Way NE, Bin C15700,

Seattle, WA 98115-0070.

Quinn, T. J. II, S. H. Hoag, and G. M. Southward. 1982.

Comparison of two methods of combining catch-per-uniteffort data from geographic regions. Can. J. Fish.

Aquat. Sci. 39:837-846.

Sasaki, T. 1985. Studies on the sablefish resources in the

North Pacific Ocean. Bull. 22, Far Seas Fish. Res. Lab.

(Shimizu), 108 p.

Sigler, M. F. 1987. Preliminary assessment of the Gulf of

Alaska sablefish population based on the Japan-U.S.

cooperative longline survey, 1986. NWAFC Processed Rep.

87-14, 28 p. Northwest and Alaska Fish. Cent., Natl.

Mar. Fish. Serv., NOAA, Auke Bay Lab., 11305 Glacier

Hwy., Juneau, AK 99801-8626.

Sigler, M. F. 1989. Assessment of Gulf of Alaska sablefish

based on the Japan-U.S. cooperative longline survey,

1987. In T. K. Wilderbuer (editor), Condition of

groundfish resources of the Gulf of Alaska in 1988.

U.S. Dep. Commer., NOAA Tech. Memo. NMFS F/NWC-165, p.

243-273. Alaska Fish. Sci. Cent., Natl. Mar. Fish.

Serv., NOAA, 7600 Sand Point Way NE, Bin C15700,

Seattle, WA 98115-0070.

Sigler, M. F. 1993. Stock assessment and management of

sablefish Anoplopoma fimbria in the Gulf of Alaska.

Doctoral dissertation, University of Washington,

Seattle, 205 p.
14

Sigler, M. F., and J. T. Fujioka. 1988. Evaluation of

variability in sablefish, Anoplopoma fimbria, abundance

indices in the Gulf of Alaska using the bootstrap

method. Fish. Bull., U.S. 86:445-452.

Sigler, M. F., and H. H. Zenger, Jr. 1989. Assessment of

Gulf of Alaska sablefish and other groundfish based on

the domestic longline survey, 1987. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS F/NWC-169, 54 p. Alaska Fish.

Sci. Cent., Natl. Mar. Fish. Serv., NOAA, Auke Bay Lab.,

11305 Glacier Hwy., Juneau, AK 99801-8626.

Yoshimura, T., and T. Sasaki. 1989. Preliminary report on

Japan-U.S. joint longline survey by the Tomi maru no. 88

in 1988. Unpubl. manuscr., 19 p. (Document submitted

to the annual meeting of the International North Pacific

Fisheries Commission, Seattle, Washington, 1989

October.) Fisheries Agency of Japan, Far Seas Fisheries

Research Laboratory, 5-7-l Orido, Shimizu, Shizuoka,

Japan 424.

Zenger, H. H., Jr. 1992. A comparison of the catch rates of

sablefish between the domestic and cooperative longline

surveys. Unpubl. manuscr., 30 p. Available Alaska

Fish. Sci. Cent., NMFS, NOAA, 7600 Sand Point Way NE,

Bin C15700, Seattle, WA 98115-0070.

Zenger, H. H., Jr., M. F. Sigler, and E. R. Varosi. 1994.

Assessment of Gulf of Alaska sablefish and other

groundfish species based on the 1988 National Marine

Fisheries Service longline survey. U.S. Dep. Commer.,

NOAA Tech. Memo. NMFS-AFSC-39, 55 p.
TABLES
THIS PAGE INTENTIONALLY LEFT BLANK
17

Table 1 .--Number of stations sampled in Gulf of Alaska

gullies by year. Domestic longline surveys,

1987-89.

Gully name 1987 1988 1989

Table 2.- -Depth stratification.

Domestic longline

surveys, 1987-89.

Depth range

Strata (m)

 Preceding Page Blank 
18

Table 3 .--Area (km2

) of the Gulf of Alaska for depths 201-1,000 m.

Area is listed by International North Pacific Fisheries

Commission area for the upper continental slope and by gully

for the gully areas.

Sampled

site

Area (km2)

Depth: 201- 301- 401- 601- 801- 201-

(m) 300 400 600 800 1,000 1,000

Upper continental slope

Gullies

Sources: E. Brown, Alaska Fisheries Science Center, RACE Division, Seattle, WA, pers. commun.,

1985; R. Haight, Alaska Fisheries Science Center, Auke Bay Laboratory, pers. commun., 1986.

Discrepancies in totals are due to rounding.
19

Table 4 .--Relative population number (RPN) for sablefish by International

North Pacific Fisheries Commission area for the upper

continental slope and by gully for gully areas. Gulf of Alaska

(GOA) total is the combined RPN for areas sampled in both 1988

and 1989. Gully total is the combined RPN for gullies sampled

in both 1988 and 1989. Domestic longline surveys, 1988 and

1989.

Depth

(m) Year RPN

Upper continental slope

Shumagin Chirikof Kodiak Yakutat Southeastern Total

Gullies

Shumagin Shelikof Amatuli Yakutat Alsek

Gully Trough Gully W-Ground Valley Strath
20

Table 4.--Continued.

Spencer Ommaney Iphigenia Dixon Gully GOA

Gully Trench Gully Entrance total total

Discrepancies in totals are due to rounding.
21

Table 5 .-&Relative population weight (RPW) for sablefish by International

North Pacific Fisheries Commission area for the upper

continental slope and by gully for gully areas. Gulf of Alaska

(GOA) total is the combined RPW for areas sampled in both 1988

and 1989. Gully total is the combined RPW for gullies sampled

in both 1988 and 1989. Domestic longline surveys, 1988 and

1989.

Depth

(m) -Year RPW

Upper continental slope

Shumagin Chirikof Kodiak Yakutat Southeastern Total

Gullies

Shumagin Shelikof Amatuli Yakutat Alsek

‘Gully Trough Gully W-Ground Valley Strath
22

Table 5 .--Continued.

Spencer Ommaney Iphigenia Dixon Gully GOA

Gully Trench Gully Entrance total total

Discrepancies in totals are due to rounding.
23

Table 6 .--Relative population number (RPN) for rougheye and shortraker

rockfish by International North Pacific Fisheries Commission

area for the upper continental slope and by gully for gully

areas. Gulf of Alaska (GOA) total is the combined RPN for

areas sampled in both 1988 and 1989. Gully total is the

combined RPN for gullies sampled in both 1988 and 1989.

Domestic longline surveys, 1988 and 1989.

Depth

(m) Year RPN

Upper continental slope

Shumagin Chirikof Kodiak Yakutat Southeastern Total

Gullies

Shumagin Shelikof Amatuli Yakutat Alsek

Gully Trough Gully W-Ground Valley Strath
24

Table 6 .--Continued.

Spencer Ommaney Iphigenia Dixon Gully GOA

Gully Trench Gully Entrance total total

Discrepancies in totals are due to rounding.
25

Table 7 .--Relative population weight (RPW) for

rougheye and shortraker rockfish by

International North Pacific Fisheries

Commission area for the upper

continental slope and by gully for

gully areas. Gulf of Alaska (GOA)

total is the combined RPW for areas

sampled in both 1988 and 1989. Gully

total is the combined RPW for gullies

sampled in both 1988 and 1989.

Domestic longline surveys, 1988 and

1989.

RPW

Rougheye Shortraker

1988 1989 1988 1989

Upper continental slope

Gullies
26

Table 8 .--Relative population number (RPN) for thornyheads by

International North Pacific Fisheries Commission area for the

upper continental slope and by gully for gully areas. Gulf of

Alaska (GOA) total is the combined RPN for areas sampled in

both 1988 and 1989. Gully total is the combined RPN for

gullies sampled in both 1988 and 1989. Domestic longline

surveys, 1988 and 1989.

Depth

(m) Year RPN

Upper continental slope

Shumagin Chirikof Kodiak Yakutat Southeastern Total

Gullies

Shumagin Shelikof Amatuli Yakutat Alsek

Gully Trough Gully W-Ground Valley Strath
27

Table 8 .--Continued.

Spencer Ommaney Iphigenia Dixon Gully GOA

Gully Trench Gully Entrance total total

Discrepancies in totals are due to rounding.
28

Table 9 .--Relative population weight (RPW) for

thornyheads by International North Pacific

Fisheries Commission area for the upper

continental slope and by gully for gully

areas. Gulf of Alaska (GOA) total is the

combined RPW for areas sampled in both 1988

and 1989. Gully total is the combined RPW

for gullies sampled in both 1988 and 1989.

Domestic longline surveys, 1988 and 1989.

Thornyhead RPW

1988 1989

Upper continental slope

Gullies
29

Table 10 .--Relative population number (RPN) for grenadiers by

International North Pacific Fisheries Commission area for the

upper continental slope and by gully for gully areas. Gulf of

Alaska (GOA) total is the combined RPN for areas sampled in

both 1988 and 1989. Gully total is the combined RPN for

gullies sampled in both 1988 and 1989. Domestic longline

surveys, 1988 and 1989.

Depth

(m) Year RPN

Upper continental slope

Shumagin Chirikof Kodiak Yakutat Southeastern Total

Gullies

Shumagin Shelikof Amatuli Yakutat Alsek

Gully Trough Gully W-Ground Valley Strath
30

Table 10 .--Continued.

Spencer Ommaney Iphigenia Dixon Gully GOA

Gully Trench Gully Entrance total total

Discrepancies in totals are due to rounding.
31

Table 11 .--Relative population number (RPN) for Pacific cod by

International North Pacific Fisheries Commission area for the

upper continental slope and by gully for gully areas. Gulf of

Alaska (GOA) total is the combined RPN for areas sampled in

both 1988 and 1989. Gully total is the combined RPN for

gullies sampled in both 1988 and 1989. Domestic longline

surveys, 1988 and 1989.

Depth

(m) Year RPN

Upper continental slope

Shumagin Chirikof Kodiak Yakutat Southeastern Total

Gullies

Shumagin Shelikof Amatuli Yakutat Alsek

Gully TroughGully W-Ground Valley Strath
32

Table 11 .--Continued.

Spencer Ommaney Iphigenia Dixon Gully GOA

Gully Trench Gully Entrance total total

Discrepancies in totals are due to rounding.
33

Table 12 .--Relative population number (RPN) for Pacific halibut by

International North Pacific Fisheries Commission area for the

upper continental slope and by gully for gully areas. Gulf of

Alaska (GOA) total is the combined RPN for areas sampled in

both 1988 and 1989. Gully total is the combined RPN for

gullies sampled in both 1988 and 1989. Domestic longline

surveys, 1988 and 1989.

Depth

(m) Year RPN

Upper continental slope

Shumagin Chirikof Kodiak Yakutat Southeastern Total

Gullies

Shumagin Shelikof Amatuli Yakutat Alsek

Gully Trough Gully W-Ground Valley Strath
34

Table 12 .--Continued.

Spencer Ommaney Iphigenia Dixon Gully GOA

Gully Trench Gully Entrance total total

Discrepancies in totals are due to rounding.
35

Table 13 .--Relative population number (RPN) for arrowtooth flounder by

International North Pacific Fisheries Commission area for the

upper continental slope and by gully for gully areas. Gulf of

Alaska (GOA) total is the combined RPN for areas sampled in

both 1988 and 1989. Gully total is the combined RPN for

gullies sampled in both 1988 and 1989. Domestic longline

surveys, 1988 and 1989.

Depth

(m) Year RPN

Upper continental slope

Shumagin Chirikof Kodiak Yakutat Southeastern Total

Gullies

Shumagin Shelikof Amatuli Yakutat Alsek

Gully Trough Gully W-Ground Valley Strath
36

Table 13 .--Continued.

Spencer Ommaney Iphigenia Dixon Gully GOA

Gully Trench Gully Entrance total total

Discrepancies in totals are due to rounding.
37

Table 14 .--Relative population number (RPN) for skates by International

North Pacific Fisheries Commission area for the upper

continental slope and by gully for gully areas. Gulf of

Alaska (GOA) total is the combined RPN for areas sampled in

both 1988 and 1989. Gully total is the combined RPN for

gullies sampled in both 1988 and 1989. Domestic longline

surveys, 1988 and 1989.

Depth

(m) Year RPN

Upper continental slope

Shumagin Chirikof Kodiak Yakutat Southeastern Total

Gullies

Shumagin Shelikof Amatuli Yakutat Alsek

Gully Trough Gully W-Ground Valley Strath
38

Table 14 .--Continued.

Spencer Ommaney Iphigenia Dixon Gully GOA

Gully Trench Gully Entrance total total

Discrepancies in totals are due to rounding.
39

Table 15.- -Numbers of each species caught during the 1989 domestic

longline survey that are not discussed in the text.

Common name Scientific name Number caught
40

Table 16 .--Sablefish commercial fishing season

start and end dates, 1988-1989, in the

Gulf of Alaska for the Central and

Western North Pacific Fishery

Management Council (NPFMC) management

areas" and survey dates.

Survey

Year Area Fishery Dates dates

aRon Berg, National Marine Fisheries Service, Alaska Regional

Office, P.O. Box 21668, Juneau, AK 99802. Pers. commun., July 1990.
FIGURES
THIS PAGE INTENTIONALLY LEFT BLANK
Figure 1 .--Station locations for the 1989 NMFS longline survey of the Gulf of Alaska and boundaries of

International North Pacific Fisheries Commission statistical arcas.
44

Figure 2a. - -Sablefish length frequencies weighted by relative population number,

by sex, for the International North Pacific Fisheries Commission

Shumagin statistical area, upper continental slope, sampled during

National Marine Fisheries Service longline surveys of the Gulf of

Alaska, 1988 (--) and 1989 (-).
45

Figure 2b.--Sablefish length frequencies weighted by relative population number,

by sex, for the International North Pacific Fisheries Commission

Chirikof statistical area, upper continental slope, sampled during

‘National Marine Fisheries Service longline surveys of the Gulf of

Alaska, 1988 (--) and 1989 (-).
46

Figure 2c. - -Sablefish length frequencies weighted by relative population number,

by sex, for the International North Pacific Fisheries Commission

Kodiak statistical area, upper continental slope, sampled during

National Marine Fisheries Service longline surveys of the Gulf of

Alaska, 1988 (--) and 1989 (-).
47

Figure 2d.--Sablefish length frequencies weighted by relative population number,

by sex, for the International North Pacific Fisheries Commission

Yakutat statistical area, upper continental slope, sampled during

National Marine Fisheries Service longline surveys of the Gulf of

Alaska, l988 (--) and 1989 (-).
48

Figure 2e.--Sablefish length frequencies weighted by relative population number,

by sex, for the International North Pacific Fisheries Commission

Southeastern statistical area, upper continental slope, sampled

during National Marine Fisheries Service longline surveys of the

Gulf of Alaska, 1988 (--) and 1989 (-).
49

Figure 2f.-- Sablefish length frequencies weighted by relative population

number, by sex, for the upper continental slope of the combined

areas sampled during National Marine Fisheries Service longline

surveys of the Gulf of Alaska, 1988 (--) and 1989 (-).
50

Figure 2g. -- Sablefish length frequencies weighted by relative population number,

by sex, for Shumagin Gully, sampled during National Marine Fisheries

Service longline surveys of the Gulf of Alaska, 1988 (--) and 1989 (-).
51

Figure 2h. --Sablefish length, frequencies weighted by relative population number,

by sex, for Shelikof Trough, sampled during National Marine Fisheries

Service longline surveys of the Gulf of Alaska, 1988 (--) and 1989 (-).
52

Figure 2i.--Sablefish length frequencies weighted by relative population number,

by sex, for Amatuli Gully, sampled during National Marine Fisheries

Service longline surveys of the Gulf of Alaska, 1988 (--) and

1989 (-).
53

Figure 2j.--Sablefish length frequencies weighted by relative population number,

by sex, for Spencer Gully, sampled during National Marine Fisheries

Service longline surveys of the Gulf of Alaska, 1988 (--) and 1989 (-),

Depth interval 401-600 m, only.
54

Figure 2k. --Sablefish length frequencies weighted by relative population

number, by sex, for the combined areas sampled during National

Marine Fisheries Service longline surveys of the Gulf of Alaska,

1988 (--) and 1989 (-). Note: In 1988, sample included the

upper continental slope, Shumagin Gully, Shelikof Trough, Amatuli

Gully, and Spencer Gully; in 1989, sample included the above plus

W-grounds, Yakutat Valley, Alsek Strath. Ommaney Trench,

Iphigenia Gully, and Dixon Entrance.
55

Figure 3a.--Sablefish length frequencies weighted by catch per unit effort (CPUE),

by sex, for depths 101-200 m in the International North Pacific

Fisheries Commission Shumagin statistical area, sampled along the

outer continental shelf during National Marine Fisheries Service

longline surveys of the Gulf of Alaska, 1988 (--) and 1989 (-).
56

Figure 3b.--Sablefish length frequencies weighted by catch per unit effort (CPUE),

by sex, for depths 101-200 m in the International North Pacific

Fisheries Commission Chirikof statistical area, sampled along the

outer continental shelf during National Marine Fisheries Service

longline surveys of the Gulf of Alaska, 1988 (--) and 1989 (-).
57

Figure 3c.--Sablefish length frequencies weighted by catch per unit effort (CPUE),

by sex, for depths 101-200 m in the International North Pacific

Fisheries Commission Kodiak statistical area, sampled along the outer

continental shelf during National Marine Fisheries Service longline

surveys of the Gulf of Alaska, 1988 (--) and 1989 (-).
58

Figure 3d.--Sablefish length frequencies weighted by catch per unit effort (CPUE),

by sex, for depths 101-200 m in the International North Pacific

Fisheries Commission Yakutat statistical area, sampled along the

outer continental shelf during National Marine Fisheries Service

longline surveys of the Gulf of Alaska, 1988 (--) and 1989 ( -). 
59

Figure 3e.--Sablefish length frequencies weighted by catch per unit effort (CPUE),

by sex, for depths 101-200 m in the International North Pacific

Fisheries Commission Southeastern statistical area, sampled along the

outer continental shelf during National Marine Fisheries Service

longline surveys of the Gulf of Alaska, 1988 (--) and 1989 (-).
60

Figure 3f.--Sablefish length frequencies weighted by catch per unit effort (CPUE),

by sex, for depths 101-200 m in Shumagin Gully, sampled during

National Marine Fisheries Service longline surveys of the Gulf of Alaska,

1988 (--) and 1989 (-).
61

3g.--Sablefish length frequencies weighted by catch per unit effort (CPUE),

by sex, for depths 101-200 m in Shelikof Trough, sampled during

National Marine Fisheries Service longline surveys of the Gulf of

Alaska, 1988 (--) and 1989 (-).
62

Figure 3h.--Sablefish length frequencies weighted by catch per unit effort (CPUE),

by sex, for depths 101-200 m in Amatuli Gully, sampled during

National Marine Fisheries Service longline surveys of the Gulf of

Alaska, 1988 (--) and 1989 (-).
63

Figure 3i. -- Sablefish length frequencies weighted by catch per unit effort (CPUE),

by sex, for depths 101-200 m on the W-grounds, sampled during the

1989 National Marine Fisheries Service longline survey of the Gulf of

Alaska.
64

Figure 4.--Length-at-age distribution of sablefish for the upper continental slope of the

Gulf of Alaska (201- 1,000 m depth), based on samples collected during the 1984

Japan-U.S. cooperative longline survey. “n” refers to the number of fish aged.

(Ages determined by the “break-and-burn” method, a technique that is being

reevaluated. Thus changes in the above ages may result. From Clausen and

Sigler 1989).
65

Figure 5.--Rougheye rockfish length frequencies weighted by relative

population number, for the combined areas sampled during

National Marine Fisheries Service longline surveys of the Gulf of

Alaska, 1988 (--) and 1989 (-). Note: In 1988, sample

included the upper continental slope, Shumagin Gully, Shelikof

Trough, Amatuli Gully, and Spencer Gully; in 1989, sample

included the above plus W-grounds, Yakutat Valley, Alsek

Strath. Ommany Trench, Iphigenia Gully, and Dixon Entrance.
66

Figure 6a.--Shortraker rockfish length frequencies weighted by relative

population number, for the combined areas sampled during

National Marine Fisheries Service longline surveys of the Gulf of

Alaska, 1988 (--) and 1989 (-). Note: In 1988, sample

included upper continental slope, Shumagin Gully, Shelikof

Trough, Amatuli Gully, and Spencer Gully; in 1989, sample

included the above plus W-grounds, Yakutat Valley, Alsek Strath,

Ommaney Trench, Iphigenia Gully, and Dixon Entrance.
67

Figure 6b.--Shortraker rockfish length frequencies weighted by relative

population number for the International North Pacific Fisheries

Commission Shumagin and Chirikof statistical areas, sampled

during National Marine Fisheries Service longline surveys of the

Gulf of Alaska, 1988 (--) and 1989 (-).
6 8

Figure 7.--Thornyhead rockfish length frequencies weighted by relative

population number, for the combined areas sampled during

National Marine Fisheries Service longline surveys of the Gulf

of Alaska, 1988 (--) and 1989 ( -). Note: In 1988, sample

included the upper continental slope, Shumagin Gully,

Shelikof Trough, Amatuli Gully, and Spencer Gully; in 1989,

sample included the above plus W-grounds, Yakutat Valley

Alsek Strath, Ommaney Trench, Iphigenia Gully, and Dixon

Entrance.
69

Figure 8.--Giant grenadier length frequencies weighted by relative

population number, for the combined areas sampled during

National Marine Fisheries Service longline surveys of the Gulf

of Alaska, 1988 (--) and 1989 (-).
70

Figure 9.--Popeye grenadier percent length frequencies for the combined

areas sampled during National Marine Fisheries Service longline

surveys of the Gulf of Alaska, 1988 (--) and 1989 (-).
71

Figure l0a.--Pacific cod length frequencies weighted by relative population

number, by sex, for the combined areas sampled during National

Marine Fisheries Service longline surveys of the Gulf of Alaska,

1988 (--) and 1989 (- ). Note: In 1988, sample included the

upper continental slope, Shumagin Gully, Shelikof Trough, Amatuli

Gully, and Spencer Gully; in 1989, sample included the above plus

W-grounds, Yakutat Valley, Alsek Strath, Ommaney Trench,

Iphigenia Gully, and Dixon Entrance.
72

Figure 10b. --Pacific cod length frequencies weighted by relative population

number, by sex, for Shelikof Trough, sampled during National

Marine Fisheries Service longline surveys of the Gulf of Alaska,

1988 (--) and 1989 (-).
73

Figure 1 la.--Arrowtooth flounder length frequencies weighted by relative

population number, for the combined areas sampled during

National Marine Fisheries Service longline surveys of the Gulf

of Alaska, 1988 (--) and 1989 (- ). Note: In 1988. sample

included the upper continental slope, Shumagin Gully. Shelikof

Trough, Amatuli Gully, and Spencer Gully; in 1989, sample

included the above plus W-grounds, Yakutat Valley, Alsek

Strath, Ommaney Trench, Iphigenia Gully, and Dixon Entrance.
Figure 11 b.--Arrowtooth flounder length frequencies weighted by relative population number for the International

North Pacific Fisheries Commission Shumagin, Chirikof, Kodiak, and Yakutat statistical areas, sampled

during National Marine Fisheries Service longline surveys of the Gulf of Alaska, 1988 (--) and

1989 (-).
75

Figure 1lc.--Arrowtooth flounder length frequencies weighted by relative

population number for Shelikof Trough and Amatuli Gully,

sampled during National Marine Fisheries Service longline surveys

of the Gulf of Alaska, 1988 (--) and 1989 (-).
76

Figure 12.--Distribution of giant grenadier catch per unit effort (fish/skate) from National

Marine Fisheries Service longline surveys of the Gulf of Alaska, 1988-89,

smoothed by distance-weighted least squares with depth stratum and station

number. Depth strata: 3 = 201-300 m; 4 = 301-400 m; 5 = 401-600 m;

6 = 601-800 m; and 7 = 801-1,000 m.
77

Figure 13.--Distribution of sablefish catch per unit effort (fish/skate) from National Marine

Fisheries Service longline surveys of the Gulf of Alaska, 1988-89, smoothed by

distance-weighted least squares with depth stratum and station number. Depth

strata: 3 = 201-300 m; 4 = 301-400 m; 5 = 401-600 m; 6 = 601-800 m; and

7 = 801-1,000 m.
78

Figure 14.--Distribution of thornyhead catch per unit effort (fish/skate) from National Marine

Fisheries Service longline surveys of the Gulf of Alaska, 1988-89, smoothed by

distance-weighted least squares with depth stratum and station number. Depth

strata: 3 = 201-300 m; 4 = 301-400 m; 5 = 401-600 m; 6 = 601-800 m; and

7 = 801-1,000 m.
79

Figure 15.--Distribution of combined shortraker and rougheye rockfish catch per unit effort

(fish/skate) from National Marine Fisheries Service longline surveys of the Gulf

of Alaska, 1988-89, smoothed by distance-weighted least squares with depth

stratum and station number. Depth strata: 3 = 201-300 m; 4 = 301-400 m;

5 = 401-600 m; 6 = 601-800 m; and 7 = 801-1,000 m.
RECENT TECHNICAL MEMORANDUMS

Copies of this and other NOAA Technical Memorandums are available from the

National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22167

(web site: www.ntis.gov). Paper and microfiche copies vary in price. 

AFSC39 ZENGER, H. H., Jr., M. F. SIGLER, and E. R. VAROSI. 1994. Assessment of Gulf of Alaska sablefish

and other groundfish species based on the 1988 National Marine Fisheries Service longline survey, 79

p. NTIS No. PB94-204872.

 

38 LOWRY, L. F., K. J. FROST, R. DAVIS, R. S. SUYDAM, and D. P. DEMASTER. Movements and

behavior of satellite-tagged spotted seals (Phoca largha) in the Bering and Chukchi Seas, 71 p. NTIS No.

PB94-180684.

37 BUCKLEY, T. W., and P. A. LIVINGSTON. 1994. A bioenergetics model of walleye pollock (Theragra

chalcogramma) in the eastern Bering Sea: Structure and documentation, 55 p. NTIS No. PB94-181831.

36 YANG, M-S., and P. A. LIVINGSTON. 1994. Variations in mean stomach content weights of walleye

pollock, Theragra chalcogramma, in the eastern Bering Sea, 32 p. NTIS No. PB94-178084.

35 PARKS, N. B., and F. R. SHAW. 1994. Relative abundance and size composition of sablefish

(Anoplopoma fimbria) in the coastal waters of California and Southern Oregon, 1984-1991. NTIS

number pending.

34 SAMPLE, T. M., and D. G. NICHOL. 1994. Results of the 1990 U.S.-U.S.S.R. cooperative bottom

trawl survey of the eastern and northwestern Bering Sea continental shelf, 183 p. NTIS No. PB94-

181849.

33 WEINBERG, K. L., M. E. WILKINS, R. R. LAUTH, and P. A. RAYMORE, JR. 1994. The 1989

Pacific west coast bottom trawl survey of groundfish resources: Estimates of distribution, abundance, and

length and age composition, 168 p. plus Appendices. NTIS No. PB94-173796.

32 PEREZ, M. A. 1994. Calorimetry measurements of energy value of some Alaskan fishes and

squids, 32 p. NTIS No. PB94-152907.

31 RONHOLT. L. L., K. TESHIMA, and W. D. KESSLER. 1994. The groundfish resources of the

Aleutian Islands region and southern Bering Sea 1980, 1983, and 1986, 351 p. NTIS No. PB94-

152915

30 LORENZ, J. M. 1994. Distribution and habitat of adult salmon in the Situk River, Alaska: Potential

impacts of flooding from Russell Fiord, 27 p. NTIS No. PB94-151859.

29 IGNELL, S. E., L. J. SIMON, and M. L. DAHLBERG. 1994. Estimation of salmonid bycatch in the

1989 Japanese squid driftnet fishery, 45 p. NTIS No. PB94-152105.

28 MORTENSEN, D. G., and H. SAVIKKO. 1993. Effects of water temperature on growth of juvenile

pink salmon (Oncorhynchus gorbuscha), 12 p. NTIS No. PB94-145349.

27 LOW, L-L. (coordinator). 1994. Status of living marine resources off Alaska, 1993, 110 p. NTIS No.

PB94-149846.

26 LOW, L-L. (coordinator). 1993. Status of living marine resources off the Pacific coast of the United

States for 1993, 90 p. NTIS No. PB94-133733.

25 KINOSHITA, R. K., A. GREIG, J. D. HASTIE, and J. M. TERRY. 1993. Economic status of the

groundfish fisheries off Alaska, 1992, 102 p. PB94-142759.