NOAA Technical Memorandum NMFS-AFSC-238
 

Results of Cooperative Research

Acoustic Surveys of Walleye 

Pollock (Theragra chalcogramma)

in the Western Gulf of Alaska from 

September 2007 to September 2011 

by

S. Romain, M. Dorn, and V. Wespestad 

U.S. DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric Administration

National Marine Fisheries Service
 

Alaska Fisheries Science Center
 

July 2012 
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 NMFS-NWFSC series is currently used by 

the Northwest Fisheries Science Center. 

This document should be cited as follows: 

Romain, S., M. Dorn, and V. Wespestad. 2012. Results of cooperative 

research acoustic surveys of walleye pollock (Theragra chalcogramma) 

in the western Gulf of Alaska from September 2007 to September 

2011. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-238, 

35 p. 

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

the National Marine Fisheries Service, NOAA. 
NOAA Technical Memorandum NMFS-AFSC-238
 

Results of Cooperative Research

Acoustic Surveys of Walleye Pollock 

(Theragra chalcogramma) in the

Western Gulf of Alaska from 

September 2007 to September 2011 

by

S. Romain1, M. Dorn2, and V. Wespestad3 

1

 Romain Consulting
 

1122 East Pike St. Suite 718
 

Seattle WA 98122
 

2

Alaska Fisheries Science Center
 

Resource Ecology and Fisheries Management Division
 

7600 Sand Point Way NE
 

Seattle, WA 98115
 

www.afsc.noaa.gov

3

Resources Analysts International
 

21231 8th Pl. W
 

Lynnwood, WA 98030 

U.S. DEPARTMENT OF COMMERCE 

Rebecca M. Blank, Acting Secretary 

National Oceanic and Atmospheric Administration

 Jane Lubchenco, Under Secretary and Administrator 

National Marine Fisheries Service 

Eric C. Schwaab, Assistant Administrator for Fisheries 

July 2012 
This document is available to the public through: 

National Technical Information Service 

U.S. Department of Commerce 

5285 Port Royal Road 

Springfield, VA 22161 

www.ntis.gov 
iii

ABSTRACT

In 2007, the Alaska Fisheries Science Center (AFSC) initiated a cooperative survey to 

assess the abundance of walleye pollock (Theragra chalcogramma) with local fishermen in the 

western Gulf of Alaska. The purpose of the survey was to estimate the abundance and 

distribution of walleye pollock in relatively small bathymetrically-complex areas using local 

fishing vessels active in the pollock fishery. The use of fishing vessels as a sampling platform 

provides more extended seasonal coverage in a restricted spatial area, in contrast to the largescale assessment surveys conducted by the AFSC. The AFSC contracted and equipped a local 

58 foot (18 m) trawler for the project. Originally the scope of the project was to evaluate the 

feasibility of conducting acoustic-trawl surveys of pollock using local fishing vessels. This was 

successfully completed and the project expanded to include other objectives: evaluation of 

transect density in bathymetrically complex regions in the western Gulf of Alaska, temporal 

variability of pollock density during replicate transects, including day/night transects, the timing 

of fish migration to spawning areas, and relationships between pollock adult, young-of-the-year, 

and euphausiid density, and the distribution of foraging humpback whales (Megaptera 

novaeangliae). This report summarizes the estimates of abundance and distribution of walleye 

pollock in areas covered by cooperative acoustic-trawl surveys conducted aboard the fishing 

vessel FV Temptation during September and January in 2007-2011. It also summarizes physical 

oceanographic and biological composition observations, initial findings from ancillary data 

collections of marine mammal observations, and dual-frequency differencing techniques to 

discriminate different types of acoustic backscatter.

v 

CONTENTS

Introduction ......................................................................................................................................1 

Methods............................................................................................................................................2 

Acoustic Equipment, Calibrations, and Data Collection ..............................................................3 

Survey Design ..............................................................................................................................4 

Data Analysis ................................................................................................................................5 

Results ..............................................................................................................................................7 

Oceanographic Conditions ...........................................................................................................7 

Acoustic Calibration .....................................................................................................................7 

Biological Sampling .....................................................................................................................8 

Distribution and Abundance .........................................................................................................9 

Discussion ......................................................................................................................................10 

Acknowledgments..........................................................................................................................12 

Citations .........................................................................................................................................13

INTRODUCTION

 In May of 2006, scientists from the Alaska Fisheries Science Center participated in a pilot 

outreach program in Sand Point, Alaska (Dorn 2006). At the meetings, fishermen raised a 

number of concerns about the adequacy of walleye pollock (Theragra chalcogramma) 

assessment. The issues appeared to be related to the contrasting observational scales of 

fishermen and National Marine Fisheries Service (NMFS) scientists responsible for conducting 

assessment surveys and population modeling. NMFS resource assessment surveys have a large 

spatial scale (i.e., the entire Gulf of Alaska) and occur infrequently (every 2 years for summer

bottom trawl and acoustic-trawl surveys, and annually for the winter acoustic-trawl surveys 

(von Szalay et al. 2010, Guttormsen and Yasenak 2007, Guttormsen and Jones 2010). 

Assessment surveys are used in the stock assessment model for pollock, which estimates stock 

abundance for the Central and Western Gulf of Alaska (Dorn et al. 2011). In contrast, the 

observational scale of fishermen is spatially restricted but temporally extensive since they are 

on the water fishing throughout the year. Fishermen questioned whether NMFS assessment 

activities were appropriately designed to monitor the status of pollock in their area. They noted 

that additional surveys in different seasons and a more comprehensive acoustic-trawl survey 

effort in winter could help address seasonal issues such as movement between spawning and 

feeding areas. Cooperative research projects with the Sand Point fishing community were 

identified as a potential approach for addressing some of these issues, but fishermen wanted the 

assurance that their investment of time and effort will lead to improvements in stock 

assessment.

The acoustic-trawl surveys described in this report resulted from collaboration between 

NMFS scientists, the Aleutian East Borough, and local fishermen to address issues raised during 

the outreach program. Acoustic-trawl surveys were conducted from a local fishing vessel in the 

western Gulf of Alaska during 2007-2011. To some extent, the surveys carried out during this 

period reflected shifting program objectives. The initial objective was simply to demonstrate the 

feasibility of using local fishing vessels to conduct acoustic-trawl surveys and to collect 

acoustic and biological information sufficient to estimate walleye pollock biomass and spatial
2 

pattern. Once this was demonstrated, the focus of the project expanded to include other 

objectives. It is likely that the project will continue to evolve given continued funding for 

cooperative research. Specific objectives of the project were the following:

• Evaluate the feasibility of conducting acoustic-trawl surveys of pollock using local fishing 

vessels, including assessment of day and night differences in pollock density from replicate 

transects.

• Evaluate the quality of acoustic data collected from the Simrad ES60 echosounder. 

• Evaluate the appropriateness of the design of the current winter NMFS acoustic-trawl 

surveys in the western Gulf of Alaska. Specific issues to be addressed included 1) transect 

density in bathymetrically complex regions in the western Gulf of Alaska, 2) temporal 

variability of pollock density during replicate transects.

• Evaluate the timing of the Midwater Assessment and Conservation Engineering (MACE) 

Program’s acoustic-trawl survey (mid-February) in Sanak Trough by conducting a survey in 

January prior to the MACE survey. 

• Evaluate relationships between adult pollock density, young-of-the-year pollock density, 

euphausiid density, and the distribution of foraging humpback whales (Megaptera 

novaeangliae). 

 This report summarizes the estimates of abundance and distribution of walleye pollock in 

areas covered by cooperative acoustic-trawl surveys conducted aboard the fishing vessel FV

Temptation during the months of September and January during the years 2007-2011 in the 

western Gulf of Alaska. It describes the use of a fishing vessel as an acoustic survey platform. It 

also summarizes physical oceanographic and biological composition observations, initial 

findings from ancillary data collections of marine mammal observations, and dual-frequency 

differencing techniques to discriminate different types of acoustic backscatter. 

METHODS

Small-scale acoustic surveys were conducted between 2007 and 2011 (Table 1) aboard the 

fishing vessel FV Temptation, a 60-ft multipurpose fishing vessel based in Sand Point, Alaska, 
3 

that participates the midwater-trawl fishery for walleye pollock, as well as several other 

fisheries in the western Gulf of Alaska. Some surveys used the same transect lines as sampled 

by the MACE acoustic-trawl surveys (i.e., Sanak), while transect lines for other surveys were 

designed to cover areas of interest identified by local fisherman. 

The vessel was equipped with a Simrad ES38-12 38 kHz split beam transducer that was 

installed at the start of the project. In 2010, an ES120-7C 120 kHz split beam transducer was 

added. Both transducers are installed in a fabricated fiberglass pod adjacent to the keel about a 

third of the way from the bow to the stern. 

Acoustic Equipment, Calibrations, and Data Collection

 

Raw acoustic data were collected using a Simrad ES60 echosounder and saved on 

external hard drives throughout the survey. In September 2010 the system was upgraded to a 

Simrad ES70 echosounder. Echoview (v. 4.9, Myriax, Pty. Ltd.) was used in conjunction with 

Simrad ER60 Lobes (v. 2.1.1) and a Java utility (Keith et al. 2005) to analyze calibrations and 

acoustic survey data. The ES60 and ES70 introduce a systematic error wave into acoustic data 

(Ryan and Kloser 2004). This error wave was removed using the ES60 Adjust V. 1.6 Java utility. 

Corrected raw data files collected from calibrations were analyzed in Echoview. Sound speed 

and absorption coefficient for calibrations were calculated using the algorithms in Echoview 

(Mackenzie 1981, Francois and Garrison 1982).

 Calibrations were conducted in accordance with standard sphere calibration methods 

(Foote et al. 1987). Majority of calibrations were done in Squaw Harbor, located at 55°13.90 N. 

160°33.14 W., although other sites were also used occasionally (Elliott Bay in Washington; King 

Cove and Balboa Bay in the survey area). A tungsten carbide sphere (38.1 mm diameter) or a 

copper sphere (60 mm diameter) for calibration of 38 kHz and 120 kHz frequencies was

suspended below the vessel while at anchor, at a consistent depth ranging from 14 to 16 m. A 

tungsten carbide sphere was used on all system calibrations except the January 2010 survey, 

when the copper sphere was used. To estimate transducer gains, target strength, and echo 

integration, measurements were collected while spheres were suspended on axis. An attempt 

was made to move the sphere through a grid of angular coordinates to model transducer beam 
4 

characteristics, but several calibrations had a limited number of detections throughout beam 

quadrants. In 2011, a sufficient number of detections were collected, and data for all years were 

analyzed in lobes regardless of the number of detections recorded. The theoretical Sa and gain 

were calculated and were compared to the lobes results for Sa and gain. The results from the 

lobes model for a Sa correction factor and gain were applied to the data. Passive recording was 

conducted in 2007, 2010, and 2012 to assess noise relative to the survey vessel. 

Temperature and salinity were measured during calibrations. Temperature profiles were 

collected using a Seabird Electronics SBE 37-SI MicroCAT. Conductivity, temperature, and 

depth profiles collected on adjacent MACE surveys with a Seabird SBE 19 SEACAT were also 

utilized when the survey vessel could not collect oceanographic data. The calibration for the 

2008 January survey was performed in 20 December, 2007 in Elliot Bay, Washington, and a 

Seabird SB19 was deployed to collect oceanographic data. 

The cooperative research study area is in the western Gulf of Alaska management area 

610 and includes two Steller sea lion (SSL) rookeries and five SSL haulouts (Fig. 1 and 2). 

Regions were surveyed to describe pollock distribution and abundance using systematic, 

parallel transect acoustic surveys similar to those described in Simmonds and MacLennan 

(2005). In the Sanak area the vessel followed the same cruise tracks surveyed by the MACE 

acoustic surveys. Sampling occurred during daylight hours, with comparative surveys 

performed at night in the Guillemot area to assess diel variability in abundance estimates. Trawl

hauls were conducted to ground truth observed acoustic backscatter layers with biological data

using a commercial midwater trawl fitted with a 9.5 mm (0.38 in) nylon mesh codend liner. 

Trawls were sampled for species composition by sorting and weighing all species in the catch. 

Length frequency data were collected for walleye pollock and other common species to the 

nearest centimeter. During the September 2010 and 2011 surveys, marine mammal observations 

were made according to protocols developed by National Marine Mammal Laboratory (NMML)

and logged using the WinCruz program (Holland 1996).

Survey Design
5 

Data Analysis

 The sounder-detected bottom determined by an Echoview bottom detection algorithm was 

used for the initial assessment of bottom depth. This line was visually assessed and manually 

edited based on relative SV to prevent inclusion of backscatter from the bottom in echo 

integration. Areas of acoustic shadow resulting from complex bathymetry were identified 

visually as acoustic dead zone (ADZ) areas and were not included in abundance estimates. 

Areas of incomplete transmissions or missing pings were minimal and removed manually. 

Echosign was categorized by species into pollock and non-pollock regions based on trawl catch 

species composition for surveys with 38 kHz data. Surveys conducted using both 38 kHz and 

120 KHz were analyzed for differences in backscatter. A dual-frequency classification 

Echoview template (version 4.90.48, May 2010), was utilized to examine differences in 

frequency response between 120 kHz and 38 kHz, using Z-score ranges measured for walleye 

pollock and euphausiids developed by De Robertis et al. (2010) for application in the eastern 

Bering Sea. The differences in backscatter for all years with two frequency collections were 

visually analyzed to augment identification of backscatter attributed to pollock, a technique that 

enhanced discrimination of some bottom features from fish. 

In situ target strength was calculated for pollock using length data from the survey 

biological samples. Average weight of pollock was calculated from samples collected during the 

surveys to scale backscatter to biomass in tons. The target strength TSl at fork length l (cm) was 

estimated by using the pollock target strength to length relationship equation at 38 kHz 

frequency (Traynor 1996): 

 

TSl = 20 log10 l – 66. 

 

The proportion pl of backscatter attributable to pollock at fork length l was then estimated as:

 , 





 









 





=

∑ 10

10

10

10

l

l

TS

l

TS

l

l

f

f

p
6 

where fl is the number of pollock at fork length l in the length frequency sample. 

The estimated backscatter, the sA, nautical area scattering coefficient, m

2

/nmi2 , of 

pollock in a survey was processed using Echoview, and then used to obtain the number (Nl) of 

pollock at length l for an elementary distance sampling unit (EDSU) of 0.5 nautical mile (nmi)

 . 

Biomass (B) for each survey was then estimated as:

∑ ×=

1000

ˆ

l

l

W NB × SD nmi2, 

where W is the average pollock weight in kilograms obtained from survey samples which is 

then divided by 1000 to express biomass in metric tons (t), and SD is the EDSU of 0.5 nmi 

multiplied by one-half the distance between transects, which varied by regions.

 To account for observed spatial structure, geostatistical methods were used to compute 

relative estimation error, defined as the ratio of the square root of the estimation variance to the 

estimate of biomass. A one-dimensional (1D) geostatistical method (Petitgas 1993, Williamson 

and Traynor 1996, Petitgas and Lafont 1997) was used to calculate relative estimation errors for 

the acoustic-based estimates for areas with surveys that met the minimum area requirements and 

1D EVA assumptions of parallel transects of relatively equal length. For surveys conducted in 

smaller areas, standard variance estimates were calculated. These errors quantify only transect 

sampling variability and do not account for other sources of known error such as uncertainties 

in target strength, trawl sampling efficiency, or error resulting from equipment and collection 

issues.

10 104

TSl

Al

l

sp N

×

× =

π
7 

RESULTS

Temperature and salinity observations conducted during calibration indicated that there 

was little variation within a season (Table 2). The mean temperature from the September 

surveys ranged from 9.7°C to 9.9°C, and the mean salinity ranged from 31.4 to 31.5 PSU. The 

mean temperature for the January surveys calibrations ranged from 3.6°C to 4.5°C, and the 

mean salinity ranged from 30.8 to 31.7 PSU. The temperature and salinity observations used for 

the 2007 September survey and the 2008 January survey were obtained from the Midwater 

Assessment and Conservation Engineering (MACE) surveys in the area that occurred in August 

2007 and February 2008, respectively (Guttormsen et al. 2010). No observations of temperature 

or salinity were made for the 2009 September survey. 

Oceanographic Conditions

 Calibration results showed insignificant variation in estimated gain parameters between 

years (Tables 3 and 4, Fig. 3). The average theoretical sv gain for all years was 20.87 and the 

average of the lobes gain combined with Sa correction was 20.93. It is likely that the variations 

between the surveys reflect measurement error rather than changes in system characteristics.

Calibrations from September 2007, December 2007, and September 2009 had equipment setting 

and collection technique issues that complicate interpretation. In September 2007, excess power 

was transmitted at 38 kHz, and a 50 kHz Furuno sounder was running during calibrations. The 

excess power can create a situation where the linear relationship between the source level and 

return signal is lost due to issues with harmonics (Urick 1993, Tichy 2003). The calibration for 

the January 2008 survey was performed in December 2007 in Puget Sound, WA, rather than in 

the western GOA, therefore oceanographic conditions significantly differed between the 

calibration and the survey. In September 2009, the tungsten carbide sphere and connecting 

swivel were close enough that the two could not be separated reliably in the acoustic data and 

sound speed had to be estimated due to a lack of environmental measurements; gain correction 

values from the September 2010 surveys were used for analysis of 2009 acoustic data. The 

January 2011 calibration results for the 38 kHz frequency appeared consistent with subsequent 

calibrations; however, the model had a high RMS value of 0.49. Overall, the on-axis data from 

Acoustic Calibration
8 

2010 and 2011 calibrations do not indicate any major malfunctions in the acoustic systems. The 

September 2010 calibration had full coverage of a grid of angular coordinates utilized by the 

Simrad lobes program for modeling beam characteristics, a sufficient number of on-axis 

readings, and environmental data collected during the calibration. This calibration compared 

well to the calibrations that had less complete collections.

 

 Noise was removed in the Echoview software for 120 kHz using techniques described by 

De Robertis and Higgenbottom (2007). Analysis of passive measurements conducted indicated 

that the -70db threshold on the 38 kHz data would account for all noise on this frequency. 

Biological data were collected from verification trawls conducted throughout the survey 

areas (Table 5). An attempt was made to make a least one trawl in each area surveyed, however 

this was not always possible due to weather conditions and the absence of sufficiently 

concentrated pollock aggregations. The majority of the catch composition by weight was

walleye pollock (Tables 6 and 7), although eulachon and capelin were occasionally caught in 

relatively high numbers, particularly in close association with age-0 pollock. 

Biological Sampling

Length samples were collected from pollock during every survey and samples from all 

regions were combined and used to describe the target strength of observed backscatter layers 

identified as pollock (Fig. 4 and 5). 

 In September of 2010, verification trawls conducted in Nagai Strait to identify 

backscatter indicated substantial aggregations of age-0 pollock at depths of 130 m or shallower, 

with larger adults caught at 160 m and deeper (Fig. 6). The tows targeted two distinct 

aggregations which were observed throughout the Nagai transects, and distribution pattern 

remained consistent throughout, with a dense school located above a more diffused aggregation 

close to the bottom. The aggregations that visually resembled the sample at 130 m ranged in 

depth from approximately 110 m to 140 m and appeared as dense layer on the echogram. The 

aggregations that resembled the 160 m sample ranged from the bottom to approximately 140 m 

depending on bottom depth. The distribution of adults close to bottom and age-0 above 
9 

indicated are consistent with patterns observed in more data rich surveys (Brodeur and Wilson 

1996) and distinct differences in appearance could be observed on the echograms (Fig. 7). An 

average weight obtained from all pollock samples was used to scale the backscatter to biomass. 

Distribution and Abundance

Acoustic data from transects were collected over areas ranging from approximately 

8 nmi2 to 140 nmi2. Biomass and relative estimation error was calculated for most surveys 

(Table 8). Surveys in Korovin Strait and King Cove contained too few transects for onedimensional (1D) geostatistical method to be employed. Instead the error was calculated using 

the standard formula for sample variance.

 

Biomass estimates for surveys conducted in the Guillemot area in 2008 was 8,287 t, with 

differences in estimates observed between two transects surveyed during daylight hours of 

2,751 t compared to 3,697 t observed at night. Day and night comparative survey differences 

were less extreme in 2011, with 1,182 t estimated for day time abundance and 1,275 t at night. 

In the Korovin Strait region the highest biomass estimate of 3,050 t was observed in 2007, with 

subsequent years having less pollock (Fig. 8). In the Whale region, biomass did not vary greatly 

between the total estimate in September of 3,067 t, and the January 2008 estimate of 4,187 t, 

with high-density measurements occurring essentially in the same place (Fig. 9). In the 

Morzhovoi region, 262 t of pollock was observed in January of 2010 and 1,949 t in September 

2011(Fig. 10). In the Pavlof area, 5,539 t was observed in September 2007, increasing to 8,478 t 

in September 2011 (Fig. 11). In Sanak Gully, much of the observed biomass occurred in no 

trawl zones (Fig. 12), but overall was consistent with MACE estimates conducted a month later. 

Differences biomass between years in the Unga Strait and Guillemot regions were not analyzed 

as the overall area sampled and transect orientation were different. The highest biomass of 

30,646 t was seen in a full survey of the Nagai area in 2010, with only 3,283 t observed along 

the same transect lines in 2011.

Mean nominal euphausiid sA was calculated from the 120 kHz data in 2010 for backscatter that 

showed a frequency response within the range for euphausiids based on De Robertis et al. 

(2010) (Table 9). Areas of interest in 2010 included Nagai Strait and surrounding areas of 
10 

Korovin Strait, Popof Strait, as each area had aggregations of age-0 and adult walleye pollock, 

and possible aggregations of euphausiids, in addition to high numbers of marine mammal 

sightings, primarily humpback whales (Megaptera novaeangliae) (Fig. 13). The high abundance 

of both forage species (euphausiids and age-0 pollock) and predator species such as humpback 

whales suggests that these were areas where strong biological interactions were occurring.

Without in situ zooplankton sampling, it is impossible to say what kinds of organisms were 

falling into the euphausiid response range, as the material properties of many species of 

zooplankton are unknown and the differences backscatter responses may fall into the same 

range (Smith et al. 2010). The September 2011 surveys did not observe the same high biomass 

and had very few humpback whale sightings overall. 

A zooplankton tow was conducted in September 2011 in Pavlof Bay using a 500 μ ring net 

attached to the codend of the commercial pollock net and streamed approximately 7 m behind 

the codend. The tow was a test to see if this towing configuration would be effective in 

capturing zooplankton to ground truth the 120 kHz data. The species composition did show 

presence of euphasiids, primarily Thysanoessa species, but the species composition was 

dominated by the small planktonic mollusk Limacina, known commonly as a sea butterfly 

(Table 10). It is unclear whether this was a chance occurrence, or if this species is unusually 

common in the area.

DISCUSSION

 

Representational acoustic data are dependent on accurate measurements of 

oceanographic conditions, equipment properties, biological factors, and appropriate survey 

design. Although there are some challenges to using a fishing vessel to conduct acoustic 

surveys, they are not insurmountable. Initial problems with calibration and equipment were 

resolved and quality acoustic data were collected during this project. There are some intrinsic 

limitations to using a 60-foot vessel to conduct acoustic surveys in the Gulf of Alaska. Weather 

conditions are often severe, particularly in winter, which can limit the time available for 

surveying, doing sample tows, and on-deck recording of information. The availability of the 

charter vessel depends on fishing seasons for pollock, Pacific cod (Gadus macrocephalus) and 
11

Tanner crab (Chionoecetes bairdi), which put limits on both timing and duration of survey 

work. Nevertheless, usable acoustic data and biological samples were collected during both 

September and January.

The pollock biomass estimates for Sanak in early January 2010 of 1,199 t and January 

2011 of 1,374 t suggested that spawning aggregations had not yet formed in this area. Scientific 

surveys conducted in mid- to late February have consistently shown high percentages of 

females in post-spawning condition, suggesting that peak spawning occurs earlier in this area 

(Guttormsen and Jones 2010). The biomass estimate in February 2010 was 26,678 t 

(Guttormsen and Jones 2010), but no scientific survey was conducted in this area in 2011. 

Identifying the time of peak spawning would require surveys to be conducted between early 

January and mid-February, which would be difficult under cooperative research arrangements, 

given the current fishing seasons for pollock, Pacific cod, and Tanner crab. 

Walleye pollock are extremely patchy in the western Gulf of Alaska. High-density 

aggregations are frequently associated with bathymetric features of the continental shelf, such as 

depressions and troughs. The spatial distribution and temporal variability of walleye pollock in

this study is similar to the results of Walline et al. (2012), which surveyed walleye pollock in 

troughs near Kodiak Island. The strong dependence of pollock density and bathymetric features 

creates complications for designing surveys since a set of parallel transects would not 

necessarily be effective in surveying fish populations with irregular spatial structure. One useful 

outcome of these small-scale surveys is the identification of these areas of high density that are 

well known to fishermen, but which may not be surveyed adequately by current MACE surveys, 

given their broader geographic scale. Nevertheless the small-scale surveys conducted to date 

have not found large aggregations of pollock outside of the areas surveyed by the current 

MACE survey design. Very patchy and very dense aggregations of pollock in areas such as 

Korovin Strait and Popof Strait cannot be surveyed effectively by a single transect, as in the 

current MACE survey design. However, since these areas are not large, the biomass found in 

these areas is a small percentage of the total biomass in the western Gulf of Alaska.
12 

Use of frequency differencing between 38 and 120 kHz echosounders to identify 

echosign that is characteristic of euphausiids provided interesting but preliminary results 

(Fig. 7). Additional work is planned to evaluate spatial pattern and potential interactions 

between age-0 pollock, adult pollock, euphausiids, and humpback whales. Current sampling 

methods are not effective in capturing either age-0 pollock or euphausiids, which limits the 

ability to confirm acoustic targets other than juvenile and adult pollock. Given that the material 

properties of species falling into the euphausiid range can be similar in backscatter response, 

backscatter alone is completely insufficient to identify whether the return encountered in 2010 

were actually euphausiids. Alternative sampling methods are under consideration, but novel 

approaches may be needed given the difficulty of deploying conventional zooplankton samplers 

on a commercial fishing vessel.

 During the 2010 pollock D-season starting 1 October, there was a spike in the bycatch of 

Chinook salmon in area 610. The observer estimate of Chinook salmon bycatch in area 610 was 

28,000 fish, which is about 20 times the average (since 2003) during this time of the year 

(NPFMC 2011). Since the pollock fleet was primarily fishing in the western part of Nagai Strait, 

the acoustic surveys in this area provided information on the distribution of adult pollock and 

forage species just prior to the D-season pollock opening. Qualitative evaluation of survey 

results indicates that there was strong overlap between adult pollock and high densities of 

forage species, such as age-0 pollock and euphausiids. The high density of forage species may 

have attracted other predators such as Chinook salmon into the area. While these results are 

suggestive, a single observation does not provide information about whether conditions in the 

fall of 2010 were exceptional. This highlights the value of an ongoing, economical, and flexible 

program to monitor major ecosystem components in the western Gulf of Alaska. 

ACKNOWLEDGMENTS

We acknowledge the essential contribution of Dwain Foster, captain of the FV 

Temptation, to this work. We also acknowledge Beth Stewart, Melvin Larsen, and Carol Foster 

for their help in making this work successful. We are grateful for the continued support of the 

Aleutians East Borough. 
13 

CITATIONS

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dynamics of age-0 walleye pollock in the Gulf of Alaska. Fish. Ocean. 5 (Suppl. 1): 148-

166. 

De Robertis, A. D., and I. Higginbottom. 2007. A post-processing technique to estimate the 

signal-to-noise ratio and remove echosounder background noise. ICES J. Mar. Sci.

64:1282-1291. 

De Robertis, A. D., D. R. McKelvey, and P. H. Ressler. 2010. Development and application of 

an empirical multi-frequency method for backscatter classification. Can. J. Fish. Aquat. 

Sci. 67(9):1459-1474. 

 

Dorn, M.W. 2006. Outreach in Alaska fishing communities: a pilot project in Sand Point. AFSC 

Quarterly Report, April-June 2006. 

(http://www.afsc.noaa.gov/Quarterly/amj2006/items3.htm).

Dorn, M.W., K. Aydin, S. Barbeaux, M. Guttormsen, K. Spalinger, and W. Palsson. 2011. 

Assessment of the walleye pollock stock in the Gulf of Alaska. In Stock Assessment and 

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the Gulf of Alaska Groundfish Plan Team, North Pacific Fishery Management Council, 

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Foote, K. G., H. P. Knudsen, G. Vestnes, D. N. MacLennan, and E. J. Simmonds. 1987. 

Calibration of acoustic instruments for fish density estimation: a practical guide. ICES 

Cooperative Research Reports, Int. Council. Explor. Sea Coop. Res. Rep. No. 144, 69 p. 

Francois, R. E., and G. R. Garrison. 1982. Sound absorption based on measurements. Part II: 

Boric acid contribution and equation for total absorption. J. Acoust. Soc. Am. 72:1879-

90. 
14 

Guttormsen, M. A., and P. T. Yasenak. 2007. Results of the 2003 and 2005 echo integrationtrawl surveys in the Gulf of Alaska during summer, Cruises MF2003-09 and OD2005-

01. AFSC Processed Rep. 2007-04, 61 p. Alaska Fish. Sci. Cent., Natl. Mar, Fish. Serv., 

NOAA, 7600 Sand Point Way NE, Seattle WA 98115. 

Guttormsen, M. A., and D. Jones. 2010. Results of the acoustic-trawl surveys of walleye pollock 

(Theragra chalcogramma) in the Gulf of Alaska, February-March 2010 (DY2010-01 

and DY2010-02). AFSC Processed Rep. 2010-05, 85 p. Alaska Fish. Sci. Cent., NOAA, 

Natl. Mar. Fish. Serv., 7600 Sand Point Way NE, Seattle WA 98115. 

Holland, R. 1996. WINCRUZ: Windows real time sighting-effort event logger. 

(http://swfsc.noaa.gov/uploadedFiles/Divisions/PRD/WinCruz.pdf).

Keith, G. J., T. E. Ryan, and R. J. Kloser. 2005. ES60Adjust.jar Java Software utility to remove 

a systematic error in Simrad ES60 data. CSIRO Marine and Atmospheric Research. 

Castray Esplanade, Hobart 7001, Tasmania, Australia.

Mackenzie, K.V. 1981. Nine-term equation for sound speed in the ocean. J. Acoust. Soc. Am.

70:807-12. 

North Pacific Fishery Management Council. 2011. Chinook Salmon Bycatch in the Gulf of 

Alaska Pollock Fishery, Environmental Assessment/ Regulatory Impact Review/ Initial 

Regulatory Flexibility Analysis for Amendment 90 to the Fishery Management Plan for 

Groundfish of the Gulf of Alaska. 

(http://www.fakr.noaa.gov/npfmc/PDFdocuments/bycatch/GOAChinookBycatch511.pdf). 

Petitgas, P. 1993. Geostatistics for fish stock assessments: a review and an acoustic application. 

ICES J. Mar. Sci. 50: 285-298. 
15 

Petitgas, P., and T. Lafont. 1997. EVA 2: Estimation variance. Version 2: a geostatistical 

software on Windows 95 for the precision of fish stock assessment surveys. ICES CM 

1997/Y:22. 

Ryan T. E., and R. J. Kloser. 2004. Improving the precision of ES60 and EK60 echosounder 

applications. Report of the Working Group on Fisheries Acoustic Science and 

Technology (WGFAST); 20–23 April 2004; Gydnia, Poland. 2004. ICES CM 

2004/B:06. 

Simmonds, J., and D. MacLennan 2005. Fisheries Acoustics Theory and Practice. Blackwell 

Publishing. 437 p. 

Smith, J. D., P. H. Ressler, and J. D. Warren. 2010. Material properties of euphausiids and other 

zooplankton from the Bering Sea. J. Acoust. Soc. Am. 128:2664-2680. 

Tichy, F. E., H. Solli, and H. Klaveness. 2003. Non-linear effects in a 200 kHz sound beam and 

the consequences for target-strength measurement. ICES J. Mar. Sci. 60: 571-574. 

Traynor, J. 1996. Target strength measurements of walleye pollock (Theragra chalcogramma) 

and Pacific whiting (Merluccius productus). ICES J. Mar. Sci. 53: 253-258. 

Urick, R. J. 1993. Principles of underwater sound 3rd edition. Peninsula Publishing. 

von Szalay, P. G., N. W. Raring, F. R. Shaw, M. E. Wilkins, and M. H. Martin. 2010. Data 

report: 2009 Gulf of Alaska bottom trawl survey. U.S. Dep. Commer., NOAA Tech. 

Memo. NMFS-AFSC-208, 245 p. 

Walline, P. D., C. D. Wilson, A. B. Hollowed, and S. C. Stienessen. 2012. Short-term effects of 

commercial fishing on the distribution and abundance of walleye pollock (Theragra 

chalcogramma). Can. J. Fish. Aquat. Sci. 69:354-368. 
16 

Williamson, N., and J. Traynor. 1996. Application of a one-dimensional geostatistical procedure 

to fisheries acoustic surveys of Alaskan pollock. ICES J. Mar. Sci. 53: 423-428. 
17 

Table 1.--Itinerary and scientific personnel for the 2007-2011 cooperative research acoustic 

surveys in the western Gulf of Alaska. 

1

AFSC - Alaska Fisheries Science Center, Seattle WA. 

2 RAI-Resource Analysts International, Lynnwood WA. 3

AEB-Aleutians East Borough, Alaska. 

Itinerary Areas Surveyed

24- 28 September 2007 Korovin Strait, Pavlof, Unga Strait, Whale

17-21 January 2008 Guillemot Island, The Whale

27-28 September 2009 Korovin Strait, Unga Strait, Nagai Strait

8-13 January 2010 King Cove, Morzhovoi Bay, Sanak, Unga Strait

19-24 September 2010 Nagai Strait (partial), Popof Strait, Korovin Strait,

4-11 January 2011 Sanak, Guillemot Island, Nagai Strait

16-24 September 2011 Whale, Korovin, Nagai Popof, Morzhovoi, Pavlof

Scientific Personnel Position Organization Nation Survey

Martin Dorn Chief Scientist AFSC1 USA All

Vidar Wespestad Fishery Biologist RAI2 USA All

Abigail McCarthy Fishery Biologist AFSC1 USA Sept.

2009

Cherilyn Lundgren Marine Mammal

Technician

AEB3 USA Sept.

2010
18 

Table 2.--Mean values of temperature and salinity measurements utilized for calibrations.

Year Month

Temp

(C°)

Salinity

(PSU) Source

2007 September 9.85 31.5 SB19

2008 January 3.6 31.5 SB19

2009 September no data no data no data

2010 January 4.45 30.83 SBE 37-SI

2010 September 9.66 31.43 SBE 37-SI

2011 January 3.92 31.65 SBE 37-SI

2011 September 3.92 31.65 SBE 37-SI
19 

Table 3.--Simrad ES60 38 kHz acoustic system description, settings, and results from sphere acoustic system 

calibrations for the western Gulf of Alaska cooperative research acoustic surveys. 

 Survey Calibration

System 

Settings

Sept.-07 

*

Dec.-07

**

Sept.-09 

*** Jan.-10 Sept.-10 Jan.-11 Sept.-11

Echosounder:

Simrad 

ES60

Simrad 

ES60

Simrad 

ES60

Simrad 

ES60

Simrad 

ES60

Simrad 

ES70

Simrad 

ES70

Simrad 

ES70

Transducer: ES38-12

Frequency (kHz): 38

Transducer depth (m): 3.4

Pulse length (ms): 1.024 1.024 1.024 1.024 1.024 1.024 1.024 1.024

Transmitted power (W): 1000 2000* 1000 1000 1000 1000 1000 1000

Angle sensitivity: 12.5

2-way beam angle (dB): -15.5 -16.2 -16.2 -16.2 -16.2 -16.2 -16.2 -16.2

Gain (dB): 21.5 21.09 21.45 20.63 21.81 21.33 21.62 21.52

Sa correction (dB): 0 -0.67 -0.64 -0.46 -0.66 -0.62 -0.66 -0.63

3 dB beam width (degree): 

Along: 12.5 7.48 12.75 11.58 19.08 14.16 10.84 17.60

Athwart: 12.5 14.17 11.91 12.84 11.57 13.98 13.72 7.29

Angle offset (degree):

Along: 0 -0.52 0.04 -0.07 -0.26 -0.34 0.01 0.18

Athwart: 0 -0.86 -0.29 -0.04 0.03 0.19 0.14 0.18

RMS (from Simrad lobes model): .26 .34 .15 .05 .13 .49 .01

Sv Threshold (dB) -70 -70 -70 -70 -70 -70 -70

Reference standard sphere TS 

dB): -42.3 -42.3 -42.3 -42.3 -33.6 -42.3 -42.3

Sphere range from transducer (m): 14.7 14.7 8.38 16.1 15.46 15.85 15.2

Absorption coefficient (dB/m): 0.009937 0.009929 0.00878 0.00917 0.00953 0.00917 0.009782 0.0091280

Sound velocity (m/s): 1470 1470.6 1482.6 1484.55 1463.37 1484.55 1462.21 1485.06

* Maximum power for the Simrad ES60 38 kHz in hull-mounted configuration is specified as 1,000 W. 

** Calibration performed In Elliot Bay, Washington.

*** The physical calibration set up did not allow enough separation between the target and rigging/no CTD.
20 

Table 4.--Simrad ES120 kHz acoustic system description and settings during the western Gulf of 

Alaska cooperative research acoustic surveys.

 Survey

System Settings Sept.-2010 Jan.-2011 Sept.-2011

Echosounder:

Simrad 

ES70

Simrad 

ES70

Simrad 

ES70

Simrad 

ES70

Transducer: ES120-7C

Frequency (kHz): 120 

Transducer depth (m): 3.4

Pulse length (ms): 1.024 

Transmitted power (W): 1000 1000 1000 1000

Angle sensitivity 23

2-way beam angle (dB): -21 -21 -21 -21

Gain (dB): 27 26.01 26.06 25.87

Sa correction (dB): 0 -0.08 -0.12

3 dB beam width (degree): 

 

Along: 7 8.71 6.38 7.08

Athwart: 7 6.22 6.6 6.76

Angle offset (degree): 

 

Along: 0 0.89 -0.02 0.16

Athwart: 0 -0.02 -0.03 -0.02

Reference standard sphere TS 

(dB): --- -39.5 -39.5 -39.5

Sphere range from transducer 

(m): --- 15.48 15.37 14.74

Absorption coefficient (dB/m): 0.0349200 .028594 0.0351270

Sound velocity (m/s): 1484.55 1462.21 1485.06

RMS 0.76 0.26 0.16
21 

Table 5.--Midwater trawl hauls for 2007 through 2011 cooperative research acoustic surveys. 

Area Year Date Gear Time Duration Position Depth (m) Temperature (°C) Total catch 

( )

Pollock

k (local) Type (local)

)

(minutes) Latitude 

(N)

Longitude 

(W)

Footrope Bottom Gear Surface % 

Unga 200 24- AW 12:49 22 55° 27.69 160° 26.14 132 164 5.2 11 1.637 89.97

Unga 200 24- AW 12:49 10 55° 26.86 160° 31.18 82 144 5.9 11 1.555 99.44

Korovin 200 25- AW 12:49 11 55° 23.18 160° 16.85 109 200 5.8 10.5 3.999 99.97

Pavlof 200 26- AW 12:49 8 55° 24.2 161° 40.28 90 105 6.2 11.1 4.486 99.69

Whale 200 27- AW 12:49 3 55° 32.18 160° 15.54 85 186 5.1 10.8 2.428 97.10

Korovin 200 28- AW 12:49 24 55° 22.85 160° 17.82 137 198 6.3 10.8 0.494 98.70

Guillemot 200 18-Jan AW 12:49 15 55° 33.31 160° 09.44 180 181 n/a 3.6 4.986 99.72

Guillemot 200 20-Jan AW 12:49 16 55° 33.73 160° 15.29 165 189 5.9 3.5 0.498 99.60

Unga 200 28- AW 18:04 28 55° 28.13 160° 24.95 105 175 n/a 10.1 n/a n/a

King 201 11-Jan AW 13:34 31 55°00.29 162°21.24 84 123 4.9 n/a 0.0187 0

Unga 201 13-Jan AW 11:58 49 55°28.64 160°23.97 175 205 5.4 n/a 1.50 99

Nagai 201 19- AW 16:54 25 55° 16.98 160° 11.33 132 183 7.5 9.4 0.011 0.02

Nagai 201 20- AW 14:15 41 55° 06.81 160° 21.01 198 218 7.4 10.7 9.074 99.99

Popof 201 21- AW 12:53 29 55°13.25 160° 22.44 123 174 7.6 10.5 0.014 99.34

Popof 201 21- AW 14:15 34 55° 13.75 160° 22.86 157 172 7.6 10.2 1.500 99.97

Nagai 201 22- AW 14:24 35 55° 12.27 160° 12.43 199 227 7.7 10.4 0.500 99.93

Nagai 201 24- AW 15:48 32 55° 03.03 160° 26.09 128 155 7.7 10.3 0.002 99.04

Guillemot 201 9-Jan AW 1002 18 55° 57.69 160° 25.45 162 190 5.4 n/a 13.612 99.98

Nagai 201 11-Jan AW 1414 15 55° 12.94 160° 19.91 193 230 4.3 n/a 3.000 99.99

Whale 2011 16- AW 18:51 40 55°32'00 160°15'59 184 231 n/a n/a 0.32 92.7

Korovin 2011 17- AW 12:10 11 55°22'51 160°18'33 124 231 3.8 9.6 0.00 3.17

Nagai 2011 17- AW 18:36 25 55°13'43 160°23'05 100 210 6.5 7.7 0.27 36.24

Nagai 2011 20- AW 20:22 21 55°08'56 160°19'40 97 115 6.1 n/a 0.36 90.54

Morzhovo 2011 22- AW 17:30 20 54°52'54 163°02'25 59 98 6.1 8.1 0.23 90.16

Pavlof 2011 24- AW 15:27 20 55°21'52 161°40'00 83 129 6.7 7.7 2.50 87.77
22 

Table 6.--Species composition for midwater trawl hauls for all winter cooperative research acoustic 

surveys. 

January 2008

Common Name Scientific Name Number Weight (kg)

walleye pollock Theragra chalcogramma 13,906 5,484.00

eulachon Thaleichthys pacificus 149 10.00

arrowtooth flounder Atheresthes stomias 2 4.00

squid Teuthoidea 42 2.00

January 2010

Common Name Scientific Name Number Weight (kg)

walleye pollock Theragra chalcogramma 1,422 1,439.80

eulachon Thaleichthys pacificus 627 33.20

Chinook salmon Oncorhynchus tshawytscha 1 18.60

arrowtooth flounder Atheresthes stomias 11 7.60

flathead sole Hippoglossoides elassodon 17 7.35

smooth lumpsucker Aptocyclus ventricosus 4 6.20

Pacific cod Gadus macrocephalus 2 5.90

herring Clupea pallasii 1 3.40

January 2011

Common Name Scientific Name Number Weight (kg)

walleye pollock Theragra chalcogramma 18,472 13,429.92

Pacific cod Gadus macrocephalus 19 89.30

arrowtooth flounder Atheresthes stomias 52 66.10

flathead sole Hippoglossoides elassodon 63 22.60

eulachon Thaleichthys pacificus 172 9.50

Chinook salmon Oncorhynchus tshawytscha 1 7.00

smooth lumpsucker Aptocyclus ventricosus 3 5.20

prickleback Stichaeidae 2 0.10

capelin Mallotus villosus 5 0.10

sand lance Ammodytidae 1 0.001
23 

Table 7.--Species composition for midwater trawl hauls for all fall cooperative research acoustic surveys.

September 2007

Common Name Scientific Name Number Weight (kg)

walleye pollock Theragra chalcogramma 41,653 14,597.80

salmon shark Lamna ditropis 1 159.10

eulachon Thaleichthys pacificas 394 50.10

arrowtooth flounder Atheresthes stomias 28 37.60

jellyfish Cnidaria 30 20.80

Pacific cod Gadus macrocephalus 4 7.70

squid Teuthoidea 7 3.51

smooth lumpsucker Aptocyclus ventricosus 5 3.70

Chinook salmon Oncorhynchus tshawytscha 1 3.40

September 2010

Common Name Scientific Name Number Weight (kg)

walleye pollock Theragra chalcogramma 9,581 7,946.86

Pacific cod Gadus macrocephalus 24 52.90

eulachon Thaleichthys pacificas 134 47.50

jellyfish Cnidaria 55 28.10

Chinook salmon Oncorhynchus tshawytscha 4 14.50

smooth lumpsucker Aptocyclus ventricosus 12 14.41

arrowtooth flounder Atheresthes stomias 43 11.90

flathead sole Hippoglossoides elassodon 2 8.20

capelin Mallotus villosus 207 1.23

salps Tunicates 9 1.11

squid Teuthoidea 2 0.01

September 2011

Common Name Scientific Name Number Weight (kg)

walleye pollock Theragra chalcogramma 3,899 3,178.04

Pacific cod Gadus macrocephalus 114 166.36

arrowtooth flounder Atheresthes stomias 24 33.51

flathead sole Hippoglossoides elassodon 7 2.71

eulachon Thaleichthys pacificas 361 18.62

Chinook salmon Oncorhynchus tshawytscha 2 1.16

smooth lumpsucker Aptocyclus ventricosus 7 3.93

capelin Mallotus villosus 27 0.10

sand lance Ammodytidae 155 3.50

jellyfish Cnidaria 485 269.52

salmon shark Lamna ditropis 3 537.79

snailfish Liparidae 1 0.02

squid Teuthoidea 3 0.03
24 

Table 8.--Estimates of walleye pollock biomass for all surveys in all years. 

Date Survey Area nmi2 Biomass (t) Relative Error %

September 2007 Korovin * 9 3,050 1.62

September 2007 Korovin 2nd pass* 9 2,002 2.28

September 2009 Korovin* 9 851 0.31

September 2010 Korovin* 9 541 1.30

September 2011 Korovin 9 538 5.2

September 2007 Pavlof 90 5,539 25.21

September 2011 Pavlof 90 8,478 7.2

September 2007 Unga 58 1,222 1.72

September 2009 Unga 35 516 4.88

January 2010 Unga 40 994 7.09

September 2011 Unga 58 1,391 5.4

September 2007 Whale 8 3,067 5.66

January 2008 Whale 8 4,187 5.67

January 2008 Guillemot day 25 8,287 3.00

January 2008 Guillemot day (partial) 4 2,715 6.42

January 2008 Guillemot night (partial) 4 3,697 6.16

January 2011 Guillemot day 25 1,182 17.26

January 2011 Guillemot night 25 1,275 11.79

September 2011 Guillemot 50 1,066 2.1

September 2009 Nagai (partial) 17 6,846 8.67

September 2010 Nagai 110 30,646 8.60

September 2010 Nagai (partial) 92 26,808 7.38

September 2010 Nagai (partial) 57 23,860 6.71

January 2011 Nagai (partial) 57 1,223 16.19

September 2011 Nagai 110 3,283 11.1

January 2010 King Cove* 5 4 12.32

January 2010 King Cove 2nd pass* 5 2 29.94

January 2010 Morzhovoi 60 262 3.61

September 2011 Morzhovoi 60 1,949 8.5

September 2010 Popof 20 5,258 4.97

January 2010 Sanak 124 1,199 2.95

January 2011 Sanak 143 1,374 3.71

*EVA variance model was not applied for Korovin Strait or King Cove surveys because there were too few transects; standard 

errors are shown instead for this area.

**Unga and Guillemot regions had different area coverage and transect orientation between years. 
25 

Table 9.--Backscatter within the euphausiid range of frequency response.

Date Survey Region; Area Sampled in nmi2 Euphausiid sA

September 2010 Nagai; 110 18183.1 

September 2010 Korovin; 9 5635.4

September 2010 Popof; 20 3279.1

January 2011 Sanak 11934.6

January 2011 Guillemot day 18133.6 

January 2011 Guillemot night 9935.3

September 2011 Nagai(partial) 28633.9

September 2011 Guillemot 12467.3

September 2011 Morzhovoi 2223.2 

September 2011 Pavlof 32939.4

September 2011 Unga 6624.7 

Table 10.--Species composition for a zooplankton tow conducted in September 2011 in Pavlof Bay. 

Species Number

Limacina sp. 672,011

Copepoda 5,600

Unidentifed euphausiids 1,552

Thysanoessa sp. 531

Clione limacine 317

Chaetognaths 303

Brachyura megalopa 33

Hyperiid amphipods 16

Unidentified amphipods 2

Lumpenus maculates 3

Unidentified mysids 1

Unidentified polychaete 1
26 

Figure 1.--Survey locations and cruise tracks for western Gulf of Alaska cooperative research acoustic 

surveys from 2007 through 2011. 

Figure 2.--Cooperative survey location in NMFS Management area 610. 

610
27 

Figure 3.--Integration gain measured by standard sphere calibrations normalized to the average over the 

period. System settings (relative to the average) are also shown. The December 2007 calibration 

was performed in Elliott Bay, Washington. 

0.92

0.94

0.96

0.98

1.00

1.02

1.04

1.06

1.08

System Sep-07 Dec-07 Sep-09 Jan-10 Sep-10 Jan-11 Sep-11
28 

Figure 4.--Walleye pollock length composition in the all areas during January surveys. 

0 

10

20

30

40

50

10 30 50 70

Frequency

Length (cm)

January 2008

0 

5 

10

15

20

25

10 30 50 70

Frequency

Length (cm)

January 2010

0 

10

20

30

40

50

10 30 50 70

Frequency

Length (cm)

January 2011
29 

Figure 5.--Walleye pollock length composition in all areas during September surveys. 

0 

10

20

30

40

50

60

70

80

90

100

10 30 50 70

Frequency

Length (cm)

September 2007

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10

10 20 30 40

Frequency

Length (cm)

September 2009

0 

10

20

30

40

50

60

70

0 10 20 30 40 50 60 70 80

Frequency

Length (cm)

September 2011
30 

Figure 6.--Walleye pollock length composition in September 2010.

Sept 2010 (all hauls)

0

10

20

30

40

50

60

70

5 15 25 35 45 55 65 75

Length (cm)

Frequency

Tows > 160 m depth

0

10

20

30

40

50

60

70

5 15 25 35 45 55 65 75

Length (cm)

Frequency

Tows < 130 m depth

0

10

20

30

40

50

60

70

5 15 25 35 45 55 65 75

Length (cm)

Frequency
31 

Figure 7.--Comparison of backscatter on an example echogram at 38 and 120 kHz on a portion of a transect in the western part of Nagai 

Strait in September 2010. 

38 kHz

120 kHz

Age-0 

pollock 

Adult 

pollock 

Zooplankton 
32 

Figure 8.--Distribution of walleye pollock biomass for surveys in the Korovin area in September 2007-

2011. 

Figure 9.-- Distribution of walleye pollock biomass for surveys in the Whale area in 2007 and 2008. 

Biomass

September 

2007 

January 

2008 

Biomass

September surveys

 2007 2009 2010 2011 
33 

Figure 10.--Distribution of walleye pollock biomass for surveys in the Morzhovoi area in 2010 and 2011. 

 

Figure 11.--Distribution of walleye pollock biomass for surveys in the Pavlof area. 

Biomass

January 

2010 

September 

2011 

Biomass

September

2011 

September 

2007 
34 

Figure 12.-- Distribution of walleye pollock biomass for surveys in the Sanak area in 2010 and 2011. 
35 

Figure 13.--Distribution of walleye pollock biomass and marine mammal observations in Nagai Strait and surrounding areas in 

September 2010. 

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 electronic (.pdf) copies vary in price. 

AFSC237	 SMULTEA, M., D. FERTL, D. J. RUGH, and C. E. BACON. 2012. Summary of systematic bowhead 

surveys conducted in the U.S. Beaufort and Chukchi Seas, 1975-2009, 48 p. NTIS number pending. 

236	 ECHAVE, K., M. EAGLETON, E. FARLEY, and J. ORSI. 2012. A refined description of essential fish 

habitat for Pacific salmon within the U.S. Exclusive Economic Zone in Alaska, 106 p. NTIS number 

pending. 

235	 CHILTON, E. A., C. E. ARMISTEAD, and R. J. FOY. 2012. The 2011 Eastern Bering Sea continental 

shelf bottom trawl survey: Results for commercial crab species, 118 p. NTIS number pending. 

234	 ALLEN, B. M., and R. P. ANGLISS. 2012. Alaska marine mammal stock assessments, 2011, 288 p. 

NTIS number pending. 

233	 KONDZELA, C. M., W. T. McCRANEY, H. T. NGUYEN, and J. R. GUYON. 2012. Genetic stock 

composition analysis of chum salmon bycatch samples from the 2010 Bering Sea groundfish fisheries, 

29 p. NTIS No. PB2012-107442. 

232	 GUTHRIE, C. M. III, H. T. NGUYEN, and J. R. GUYON. 2012. Genetic stock composition analysis of 

chinook salmon bycatch samples from the 2010 Bering Sea trawl fisheries, 22 p. NTIS No. PB2012­

104700. 

231	 SMITH, K. R., R. A. MCCONNAUGHEY, and C. E. ARMISTEAD. 2011. Benthic invertebrates of the 

Eastern Bering Sea: A synopsis of the life history and ecology of snails of the genus Neptunea., 58 p. 

NTIS No. PB2012-108929. 

230	 HIMES-CORNELL, A., C. PACKAGE, and A. DURLAND. 2011. Improving community profiles for the 

North Pacific fisheries, 85 p. NTIS No. PB2012-108928. 

229	 YANG, M-S. 2011. Diet of nineteen mesopelagic fishes in the Gulf of Alaska, 67 p. NTIS No. PB2012­

PB2012-102005. 

228	 LEW, D. K., and A. HIMES-CORNELL. 2011. A guide to designing, testing, and implementing Alaska 

Fisheries Science Center economic and social surveys, 43 p. NTIS No. PB2012100169. 

227	 LAUTH, R. R. 2011. Results of the 2010 eastern and northern Bering Sea continental shelf bottom 

trawl survey of groundfish and invertebrate fauna, 256 p. NTIS No. PB2012100168. 

226	 TESTA, J. W. (editor). 2011. Fur seal investigations, 2008-2009, 80 p. NTIS No. PB2012100205. 

225	 RARING, N. W., P. G. VON SZALAY, F. R. SHAW, M. E. WILKINS, and M. H. MARTIN. 2011. Data 

Report: 2001 Gulf of Alaska bottom trawl survey, 179 p. NTIS No. PB2011-111406. 

224	 HOFF, G. R., and L. L. BRITT. 2011. Results of the 2010 eastern Bering Sea upper continental slope 

survey of groundfish and invertebrate resources, 300 p. NTIS No. PB2011-111407. 

223	 ALLEN, B. M., and R. P. ANGLISS. 2011. Alaska marine mammal stock assessments, 2010, 292 p. 

NTIS No. PB2011-111461. 

222	 GRAY, A. K.,W. T. MCCRANEY, C. T. MARVIN, C. M. KONDZELA, H. T. NGUYEN, and J. R. 

GUYON. 2011. Genetic stock composition analysis of chum salmon bycatch samples from the 2008 

Bering Sea groundfish fisheries, 29 p. NTIS No. PB2011-110765.