SC/F16/JR19

Estimation of prey species biomass in the Sanriku region basedon 2008 and 2009 JARPNII acoustic surveys
ATSUSHI WADA1, KEIICHI ONODERA2, MITSUHIRO SAEKI 2 AND TSUTOMU TAMURA1
1
2

Institute of Cetacean Research, 4-5, Toyomi-cho, Chuo-ku, Tokyo, 104-0055, Japan
Miyagi Prefecture Fisheries Technology Institute, 97-6 Sodenohama, Watanoha, Ishinomaki, Miyagi 986-2135, Japan

Contact e-mail:wada@cetacean.jp

ABSTRACTPrey species surveys were conducted in the coastal region off Sanriku, north eastern Japan in spring 2008 and 2009 as a part of JARPNII
coastal component off Sanriku. The surveys were conducted concurrently with a sampling survey of common minke whales. Two stratified
blocks were analysed. Zigzag tracklines were set in the blocks. The surveys were conducted by a trawler type RV, Takuyo-maru. Acoustic
data were recorded continuously along the tracklines by a quantitative echosounder. Samplings using a midwater trawl net were conductedat some stations to identify species and size compositions of acoustic backscatterings. Vertical oceanographic conditions were recorded byusing a CTD. Subsurface oceanographic conditions were recorded continuously along the tracklines. In 2008 the total biomass estimation ofsand lance adult was 8,076tons, while that of sand lance juvenile was 1,237tons. The estimations of biomass of Japanese anchovy were 0.18
tons in blocks B and C, respectively. In 2009 the total biomass estimation of sand lance adult was 2,512tons, while that of sand lance juvenile
was 315tons. The estimation of biomass of Japanese anchovy were 0.64 tons in block B and C, respectively. Biomass estimates of sand lance
were higher than Japanese anchovy in 2008 and 2009 in this study. This result suggested that seasonal movement of common minke whales
could be related to availability of sand lance in Sendai Bay during spring season. These data would be useful as input data for the developmentof ecosystem models in this area.
KEYWORDS: FOOD/PREY, ACOUSTICS; MODELLING; SCIENTIFIC PERMITS; SANRIKUINTRODUCTION
JARPNII was designed to contribute to conservation and sustainable use of marine living resources including whales in
the western North Pacific, especially within Japan’s EEZ (Government of Japan, 2000; 2004). One of the major objectivesof JARPN II is to advance feeding ecology and ecosystem studies, involving studies of prey consumption by cetaceans,
prey preference of cetaceans and ecosystem modeling. To accomplish the goal, sampling survey of common minke whales(Balaenoptera acutorostrata) and survey on biomass estimation of their prey species have been conducted concurrently
off Sanriku, Japan since 2003 as a JARPNII coastal component. Prey species surveys were conducted in the coastal region
off Sanriku, independently from the coastal sampling surveys for common minke whale since 2003 (except 2004, 2011)as a part of JARPNII.
The sand lance (Ammodytes personatus) and Japanese anchovy (Engraulis japonicas) are key prey species in the Sanriku
ecosystem supporting different species of baleen whales, pinnipeds, birds and fish. Changes in its abundance could affectthe biology and abundance on its predators as well the whole ecosystem. For this reason JARPNII considered it important
to conduct yearly monitoring of sand lance and Japanese anchovy biomass in the research area.
This paper presents the results of the sand lance and Japanese anchovy biomass estimation based on the echo sounderdata collected in 2008 and 2009 seasons. It was not possible to evaluate any trend in these abundance with just two surveys
conducted. However the sand lance and Japanese anchovy biomass estimates obtained in the present study are useful toevaluate the impact of these consumption by common minke whales in the research area, and as input data for thedevelopment of the ecosystem models.

MATERIALS AND METHODS
Survey area
The Sanriku region is northeastern part of the Japanese Main Island that was known to be major grounds of the pastcommercial whaling of common minke whales in spring season (Hatanaka and Miyashita, 1997). This region is one of
the most productive waters in the world ocean due to the mixing of Kuroshio and Oyashio currents. Generally, the Oyashio
water dominates in the survey area in the investigation period (Hanawa and Mitsudera, 1987). Therefore, this region was
an important fishing ground for commercial species such as Japanese sand lance (Nagashima, 2007), Japanese anchovy(Nagashima, 2007), and Pacific krill (Euphausia pacifica) (Taki et al., 1993; Taki, 2002). The possible competition
between the whales and the fisheries in this area was suggested by the JARPN and the JARPNII feasibility study (Tamura
and Fujise, 2002a, b).
1

The sampling survey of minke whale was conducted in the coastal waters within the 50 n.miles (mainly within 30 n.miles)
from Ayukawa, Miyagi prefecture, Japan. In 2003, the prey survey was conducted in a wider area off the Pacific coast of
the northern Japanese Main Island, preliminary. This survey area divided into two parts. To avoid the conflict with nets
in the coastal waters, the waters within 10 miles from the coast were excluded in principle. Since 2005, the prey survey
area was divided into nine blocks (A, B, C, D, E, F, G, H, I, and J) based on bottom depth (20, 40, 100, and 200m) andprefectural boundary (boundary between Miyagi and Fukushima prefecture) (Figure 1). Because of logistical constraint,
the number of blocks changed in each year (Table 1). In 2008 and 2009, 5 blocks (B, C, E, D, E and F) were surveyed.
The details of previous prey surveys (from 2003 to 2007) around Sanriku region were described by Yonezaki et al. (2009).
Track-line design and timing
Saw tooth type zigzag lines were used in each survey. If there was any fishing equipment, track line was cancelled. The
survey was conducted during the daytime from an hour after sunrise to an hour before sunset.
Survey vessels
In 2008 and 2009 surveys, the research vessel (RV) used was a trawler-type RV, “Takuyo maru (TKY)” (Miyagi
prefecture Fisheries Technology Institute, 120 GT) (Figure 2). Net sampling, acoustic data recording using quantitativeechosounders and oceanographic surveys were conducted by Takuyo maru.
Net sampling and quantitative echosounder
In 2008 and 2009, midwater trawl was used. The trawl net was a mouth opening of 7m width / 3.5m height and a 3mm
liner cod end. Towing speed of the trawl nets was 2-4knots. The depth and the height of the mouth of the net weremonitored with a net recorder. All samples were identified to the species as much as possible and weighted aboard thevessels. For the major species (ex. Japanese anchovy, Japanese sand lance, Pacific krill), a sample of 100 animals was
taken, and lengths and weights were measured. Scaled and standard lengths were used to Japanese anchovy and adult /juvenile Japanese sand lances, respectively.
The distribution and abundance of the prey species were investigated with the quantitative echo sounder (EK 500; Simrad,
Norway) on board Takuyo maru. Echo sounder data were recorded continuously while the vessel steamed on
predetermined track line. The nominal steaming speeds on the track line was 9-10knots. Quantitative echo sounder EK500
with frequency at 38 and 120kHz were used to collect data for the acoustic survey. Acoustic data were acquired with
Echoview version 3.00 (Sonar Data Pty Ltd, Australia). The copper sphere technique described in EK 500 operation
manual (Simrad, 1997) was applied for the calibrations. Acoustic data were stored with an aid of software, Echoview(Sonar Data, Australia). Species/size compositions of echo signs were identified by targeting mid-water trawling. Water
temperature and salinity profiles were recorded using Conductivity Temperature Depth profiler (CTD, Seabird, USA).
Data analysis methodology of quantitative echosounder
We applied the same acoustic data analysis described by method of 2009 JARPNII Review paper (Murase et al., 2009),
because it was appropriate for comparison purposes.
The wet weight (wt) of sand lance and Japanese anchovy were calculated with the following formula. Where, SL wasstandard length, TL was total length of prey species. In each stratum that 5% of the upper and lower values were notincluded in the analysis.
Sand lance adult
Sand lance Juvenile
Japanese anchovy

log10 𝑤𝑡(g) = 2.7288 × log10 (𝑆𝐿, 𝑐𝑚) − 2.0371
log10 𝑤𝑡(g) = 3.0572 × log10 (𝑆𝐿, 𝑐𝑚) − 2.4885
𝑤𝑡 (g) = 0.004 × (𝑆𝐿, 𝑐𝑚)3.09(Murase, per com)
(Murase, per com)(Anonymous, 1990)

(1)
(2)
(3)

Each backscattering cross section area (σ) was calculated with the following formula based on prey species target strength:  4 10TS ( L) / 10(4)where, TS(L) were Target Strength (TS) of sand lance (juvenile and adult) and Japanese anchovy.
Sand lance adult
Sand lance juvenile
Japanese anchovy

TS = 21.4 × log 𝑒 (𝑆𝐿, 𝑚𝑚) − 170.2
TS = 22.3 × log 𝑒 (𝑆𝐿 , 𝑚𝑚) − 160.2
TS = 20.0 × log 𝑒 (𝑇𝐿, 𝑐𝑚) − 72.5

(Murase, per com)
(Murase, per com)
(Iversen et al., 1993)

(5)
(6)
(7)

Mean backscattering area per square n.mile of survey transect (SA) attributed to prey species for every 1n.mile of survey
transect over 15 to 150m depth was calculated by following formula;s A  4r02 1852 2 

r2 150

r1 152sV dr (

m2)
n.mi 2(8)

SC/F16/JR19
where, r is depth from the surface, r0 = 1m representing the reference range for backscattering strength and SV = 0 if 10log (SV)≦–80dB, because threshold backscattering was set at –80dB. ΔMVBS was calculated quantitatively using
Echoview.
Average area prey species biomass density (  i ) was calculated as follows;i  S A

w

(9)



With this formula mean prey species biomass of each transect in each stratum was calculated. Weighted mean of (  k )of each block was;k 

 (  n )
n
i

i

(10)

i

where,  k = mean SA in kth block, ni = number of transects in kth block, Then variance of  k was calculated with theformula;Var (  k ) 2N  (  i   k ) ni
N 1
 ni 2

2

(11)

Biomass was estimated as;

Bk  A   k(12)where, Bk is density biomass in kth block and A is area of kth block. Variance of Bk was calculated with following formula;

Var ( Bk )  A2 Var (  k )(13)

Coefficient of variation of Bk was calculated as;

CV ( Bk ) Var ( Bk )
Bk

(14)

In this study, biomass estimation of prey species were estimated in blocks B and C. Because, main distribution of sandlance is also covered in blocks B and C.

RESULTS
Survey distance of each block
Track design is shown in Figure 3. The number of transects and survey distance of each block are shown in Table 2. In2008 season, total survey distance in blocks B and C were 99.7 and 91.8n.miles, respectively. In 2009 season, total survey
distance in blocks B and C were 70.1 and 92.4n.miles, respectively.
Sizes of the prey species sampled
The sample size and average length of sand lance and Japanese anchovy by trawl survey in 2008 and 2009 are shown in
Table 3. Body length of sand lance (adult and juvenile) ranged from 80 to 162mm, from 25 to 70mm, respectively. Body
length of Japanese anchovy ranged from 65 to 106mm (Table 3). Results of the size distribution of sand lance and Japanese
anchovy in 2008 and 2009 are shown in Figures. 4, 5 and 6.
Biomass estimation of prey species by each block
The results of the density and biomass estimation of sand lance and Japanese anchovy in each block are shown in Tables
4 and 5. In 2008 season, total biomass estimations of sand lance adult in blocks B and C were 2,718 and 5,358tons,
respectively; those of sand lance juvenile were 82 and 1,155tons, respectively. The biomass estimations of Japanese
anchovy were 0.14 and 0.05tons, respectively. In 2009 season, total biomass estimations of sand lance adults in block B
and C were 790 and 1,722tons, respectively; those of sand lance juvenile were 8 and 307 tons, respectively. The biomass
estimations of Japanese anchovy were 0.39 and 0.24tons, respectively.

3

The mean densities in each prey were from 0.7 to 7.1g/m2 in sand lance adult from 0.01 to 1.5g/m2 in sand lance juvenile.
The mean densities in Japanese anchovy were from 0.0001 to 0.0003g/m2.

DISCUSSION
Biomass estimates of sand lance were higher than Japanese anchovy in the 2008 and 2009 surveys. This result was similar
to those of a previous study (Murase et al., 2009).
Sand lance is distributed in the central region of the Sendai Bay where the water depth was 40-70m with medium to large
gravel bottom substrate (Kobayashi et al., 1995). Adult sand lance (local name: Meroudo) in the Sendai Bay burythemselves in the substrate and estivate without feeding during summer while their feeding occur in pelagic water fromlate winter to early summer (Kobayashi et al., 1995; Kodama, 1980). Their spawning occur during the rest of season.
Because of their unique life history, sand lance is a resident species in the Sendai Bay in contrast to other migrant pelagic
fish such as Japanese anchovy. Sand lance in Sendai Bay in spring would be a predictable prey species for common minke
whales. This could be one of the reasons why common minke whales are distributed in the Sendai bay in spring.
It was reported that lesser sand eel (A. marinus) was an important prey for common minke whale in a local region (theeastern North Sea) of the eastern North Atlantic (Windsland et al., 2007). A small scale habitat study in the coastal waterof Scotland suggested that seasonal movement of common minke whales could be related to availability of lesser sandeel (Macleod et al., 2004). Based on the results of this study, it can be concluded that the sand lance is a locally andtemporally important species for common minke whales in Sendai Bay. Windsland et al. (2007) reported that common
minke whales could switch their prey from sand eel to haddock in the eastern North Sea when the recruitment of sand eel
was poor. It is expected that such prey switching might occur in Sendai Bay when biomass of sand lance is low. Tamura
et al (2016: SC/F16/JR17), however, suggested that prey switching do not occur in Sendai Bay.
Commercial fishing of sand lance operates in Sendai Bay in spring. Traditionally, juvenile (body length ≤ 10 cm) andadult sand lance are captured by lift net with light and large dip net, respectively. Bottom trawl fishing boats participatedin adult sand lance fishing from 1984 to 1989 (Nagashima, 2004). Because the negative effects of bottom trawling onabundance of sand lance, local fishing associations abstained of conducting trawl fisheries and they set a fishing quota
for lift net fishing in 1990 (Nagashima, 2004). The abundance of sand lance increased after 1990 again. Sand lance in
Sendai Bay is considered as a distinctive stock based on biological and morphological characteristics (Kodama, 1980).
Though they are distributed in coastal waters around Japan. Because both commercial fishing and minke whales target
on the single stock of sand lance in the small area, effect of commercial catch and feeding by common minke whales is
expected to be high.
Similar acoustic surveys were conducted in JARPNII in 2005 and 2006 (Appendix 2: Murase et al. 2009). In 2005 and2006 season, in blocks B, C, E and F, biomass of sand lance were reported 7,610 and 28,340tons, respectively. In 2005
and 2006 seasons, in blocks B, C, E and F, biomass of Japanese anchovy were reported 1,320 and 9,060tons, respectively.
A direct comparison of those surveys with the present study is complicated, because differences in the blocks surveyed.
Although the densities were similar between both studies, difficulties experienced in the comparison of prey species
abundance derived from echo sounder surveys should be recognized. Factors that should be considered in the comparisons
include differences in survey coverage, differences in design and timing of surveys and differences in the methods for
estimating biomass of prey species.
There are some general limitations to the interpretation of the result of abundance estimation of prey species using echosounder: 1) background prey species could not be detected by echo sounder because of low density, 2) surface prey species
which meant could distribute shallower than the transducers. These limitations would contribute to an underestimation of
prey species biomass. Overall, the results presented here provided general distribution and biomass patterns of preyspecies in the survey area. The following points should be considered to improve the echo sounder survey in future: 1)
survey should be conducted in peak abundance season to minimize seasonal effect on abundance estimation, 2) survey
should be conducted in same area and survey timing to interpret yearly changes, and 3) prey survey should be conductedconcurrently with cetacean samplings.
However, these results of estimates of sand lance by echosounder could be useful for comparing to the prey consumption
by common minke whales (Tamura et al, 2016: SC/F16/JR17).
Results of preliminary ecosystem modelling work suggested that feeding of minke whales had substantial impact on MSY
of sand lance but the magnitude was depended on shape of functional response (relationship between consumption by
predator and prey availability) (Okamura et al., 2009). See updated results of the ecosystem modelling work in Kitakado
et al. (2016: SC/F16/JR29).

ACKNOWLEDGEMENT
Data of this study were collected by many crews and researchers. We thank the captains, crews and researchers who
dedicated to collect data in the field. Our sincere thank to Luis A. Pastene of the Institute of Cetacean Research (ICR) and4

SC/F16/JR19
Hiroto Murase of the National Research Institute of Far Seas Fisheries, Fisheries Research Agency (NRIFSF) for theirvaluable suggestions and useful comments on this paper. This survey was supported by Fisheries Agency of Japan,
Fisheries Research Agency of Japan, Miyagi Prefecture and the Institute of Cetacean Research. We thank these
institutions for their support.

REFERENCES
Hanawa, K., and Mitsudera, H. 1987. Variation of water system distribution in the Sanriku coastal area. J. Oceanog. Soc. Japan. 42: 435-46.
Hatanaka, H., and Miyashita, T. 1997. On the feeding migration of the Okhotsk Sea-West Pacific Stock of minke whales, estimates based on lengthcomposition data. Rep. Int. Whal. Comm. 47: 557-64.
Iversen, S.A., Zhu, D., Johannesen, A. and Toresen, R., 1993. Stock size, distribution and biology of anchovy in the Yellow Sea and East China Sea.
Fish. Res. 16:147-63.
Kitakado, T., Murase, H., Tamura, T., Onodeta, K. and Saeki, M. 2016. Predation impacts on sand lance population by consumption of common minke
whales off Sanriku region. Paper SC/F16/JR29 presented to the JARPNII special permit expert panel review workshop, Tokyo, February 2016
(unpublished). **pp.
Kobayashi, N., Nagashima, H., Kodama, J., Kikuchi, Y., Kobayashi, I and Sato, K. 1995. Study on the ecological and resource of the sandeel, Ammodytes
personatus Girard, in Sendai Bay. Bull. Miyagi Pref. Fish. Res. Dev. Center. 14: 38-49. (in Japanese)
Kodama, J. 1980. Studies on the structure of populaton and the ecology of sand-lance, Ammodytes personatus GIRARD, in the coastal waters of Miyagi
prefecture. Bull. Miyagi Pref. Fish. Exp. St. 10:1-31 (in Japanese)
Macleod, K., Fairbairns, R., Gill, A., Fairbairns, B., Gordon, J., Blair-Myers, C. and Parsons, E. C. M. 2004. Seasonal distribution of minke whales
Balaenoptera acutorostrata in relation to physiography and prey off the Isle of Mull, Scotland. Mar. Ecol.-Prog. Ser. 277: 263-74.
Murase, H., Kawahara, S., Nagashima, H., Onodera, K., Tamura, T., Okamoto, R., Yonezaki, S., Matsukura, R., Minami, K., Miyashita, K., Yoshida,
H., Goto, M., Bando, T., Inagake, D., Okazaki, M., Okamura, H. and Kato, H. 2009. Estimation of Prey preference of common minke Whales(Balaenoptera acutorostrata) in a coastal component (off Sanriku) of JARPNII in 2005 and 2006. Paper SC/J09/JR10 presented to the JARPNII
Review Meeting, Tokyo, January 2009 (unpublished). 15pp.
Nagashima, H. 2004. Dynamics in population density time series of sand lance, Ammodytes personatus GIRARD, in Sendai Bay. Miyagi Pref Rep Fish
Sci 4:51-9.
Nagashima, H. 2007. Estimation of Japanese anchovy (Engraulis japonicus) population structure in Miyagi coastal waters. Miyagi Pref. Rep. Fish. Sci.
7: 1-8.
Okamura, H., Nagashima, H. and Yonezaki, S. 2009. Preliminary assessment of impacts on the sand lance population by consumption of minke whales
off Sanriku region. Paper SC/J09/JR14 presented to the JARPNII review workshop, Tokyo, January 2009 (unpublished). 20pp.
Simrad. 1997. Simrad EK500 Scientific Echo Sounder Operation Manual P2170G. Simrad AS Horten, Norway.
Taki, K. 2002. Annual variations in the conditions of fisheries for Euphausia pacifica in Sanriku and Joban waters, north eastern Japan. Bull. Fish. Res.
Agen. 3: 7-26 (in Japanese with English abstract).
Taki, K., Kotani, Y., Kuroda, K., and Kasuya, T. 1993. Effect of surface water temperature and salinity on the catch of Euphausia pacifica in near shore
waters off the Onagawa coast, Miyagi prefecture, northern Japan. Bull. Tohoku Natl. Fish. Res. Inst. 55: 29-35 (in Japanese with English abstract).
Tamura, T., and Fujise, Y. 2002a. Geographical and seasonal changes of the prey species on minke whale in the Northeastern Pacific. ICES J. Mar. Sci.
59: 516-28.
Tamura, T. and Fujise, Y. 2002b. Food habit of common minke whales based on JARPNII. Appendix 4, pp 47-63. In: Government of Japan (Fujise, Y.,
Kawahara, S., Pastene, L.A. and Hatanaka, H. Eds.) Report of 2000 and 2001 feasibility study of the Japanese Whale Research Program under Special
Permit in the western North Pacific-Phase II (JARPNII). Paper SC/54/O17 submitted to the 54th IWC Scientific Committee Meeting (Available fromthe IWC Secretariat).
Yonezaki, S., Nagashima, H., Murase, H., Yoshida, H., Bando, T., Goto. M., Kawahara, S. and Kato, H. 2009. Methodology and procedures of surveys
of prey of common minke whales JARPNII – Coastal component of Sanriku -. Paper SC/J09/JR5 presented to the JARPNII Review Meeting, Tokyo,
January 2009 (unpublished). 6pp.
Windsland, K., Lindstrøm, U., Nilssen, K. T. and Haug, T. 2007. Relative abundance and size composition of prey in the common minke whale diet inselected areas of the northeastern Atlantic during 2000-04. J. Cetacean Res. Manage. 9: 167-78.

5

Table 1. Summary of prey surveys in Sanriku region from 2003 to 2013 excluding 2004 and 2011.
Gross
Tonnage(t)

SeasonDate

Area(Block)Vessel2003

9-28 Apr.

35N-41N
I,II

Kaiyo-Maru No.7

Midwater
trawl

499

Bongo net

Sabiki

IKMT

EchosounderFrequency
(kHz)

22

4

-

17

EK500

38,120,200

No survey

2004
2005

11-27 Apr.

38.21N-37.54N-37.40N
A,B,C,D,E,Fand G

Takuyo-Maru

120

14

-

-

-

EK500

38,120,200

2006

11-27 Apr.

38.21N-37.54N-37.40N
A,B,C,D,E,F,G,H, I and J

Takuyo-Maru,
Syunyo- MAru

120
887

11

1

2

-

EK500

38,120,200

2007

9-27 Apr.

38.21N-37.54N-37.40N
B,C,D,E,F and G

Takuyo-Maru

120

10

-

-

-

EK500

38,120,200

2008

9-24 Apr.

38.21N-37.54N-37.40N
B,C,D,E and F

Takuyo-Maru

120

9

-

-

-

EK500

38,120,200

2009

20 Apr.-1 May

38.21N-37.54N-37.40N
B,C,D,E and F

Takuyo-Maru

120

9

-

-

-

EK500

38,120,200

2010

16-27 Apr.
13-22 May

38.21N-37.54N-37.40N
B,C,E and F

Takuyo-Maru

120

12

-

-

-

EK500

38,120,200

Cancelled(Effects of the Great East Japan Earthquake )

2011
2012

16-21 Apr.
14-18 May

38.40N-38.15N-37.54N
A,B,C and D

Takuyo-Maru

120

12

-

-

-

EK500

38,120,200

2013

16-24 Apr.
21-23 May

38.40N-38.15N-37.54N
A,B,C and D

Takuyo-Maru

120

8

-

-

-

EK500

38,120,200

Table 2. Detail of prey survey in Sanriku region in 2008 and 2009.
2008

2009

Block

NumberoftransectSurveydistance(n.miles)NumberoftransectSurveydistance(n.miles)

B

9

99.7

8

70.1

C

9

91.8

13

92.4

Table 3. The number of individuals of samples, minimum, maximum and average of body length of sand lance andJapanese anchovy sampled by trawl surveys in 2008 and 2009
Numbers

Average(mm)

Minimum(mm)

Maximum(mm)

Sand lance (Adult)

201

105

80

162

Sand lance (Juveile)

507

41

25

70

Japanese anchovy

33

85

65

106

Species6SC/F16/JR19

Table 4. Mean density and biomass of sand lance and Japanese anchovy in blocks B and C in 2008.
(Block B)
SpeciesMean
density(g/m2 )

Biomass
(t)

CV
(%)

Sand lance (Adult)

2.4

2,718

4.9

Sand lance (Juveile)

0.07

82

4.7

Japanese anchovy

0.00010.14

4.0

Biomass
(t)

CV
(%)

(Block C)
SpeciesMean
density(g/m2 )

Sand lance (Adult)

7.1

5,358

8.2

Sand lance (Juveile)

1.5

1,155

6.0

Japanese anchovy

0.00010.05

5.0

Table 5. Mean density and biomass of sand lance and Japanese anchovy in blocks B and C in 2009.
(Block B)
SpeciesMean
density(g/m2 )

Biomass
(t)

CV
(%)

Sand lance (Adult)

0.7

790

3.6

Sand lance (Juveile)

0.01

8

3.9

Japanese anchovy

0.0003

0.39

6.3

Biomass
(t)

CV
(%)

(Block C)
SpeciesMean
density(g/m2 )

Sand lance (Adult)

2.3

1,722

3.4

Sand lance (Juveile)

0.4

307

5.5

Japanese anchovy

0.0003

0.24

4.2

7

Figure 1. The survey area and nine blocks of prey species surveys of Sanriku region since 2005.
Blocks H, I and J were investigated in 2006 only.
In 2008 and 2009, five Blocks (B, C, D, E and F) were investigatedFigure 2. Prey surveys vessel, Takuyo-maru (TKY) in 2008 and 2009.

Figure 3. The track line of prey surveys in 2008 and 2009.

8

SC/F16/JR19

Figure 4. Body length distribution of sand lance juvenile sampled by trawl survey in 2008 and 2009.

Figure 5. Body length distribution of sand lance adult sampled by trawl survey in 2008 and 2009.

Figure 6. Body length distribution of Japanese anchovy sampled by trawl survey in 2009.

9

Appendix 1. Information of prey species in the coastal waters
off Sanriku.
MITSUHIRO SAEKI AND KEIICHI ONODERA
Miyagi Prefecture Fisheries Technology Institute, 97-6 Sodenohama, Watanoha, Ishinomaki, Miyagi 986-2135, Japan
Japanese sand lance
R/V Takuyo Maru (120GT), Miyagi Prefecture Fisheries Technology InstituteResearch period: every year in January
Research area: Sendai Bay
Methods: Bongo net by Takuyo Maru (120GT)
Index: CPUE (no. of individuals per m3)

Figure 1. Occurrence of sand lance (juvenile) in January around Sendai Bay (ind./m 3)

10

SC/F16/JR19

Year
Figure 2. Yearly change of Density Index (ind./m3) of sand lance in the estivation period around Sendai Bay

11

Appendix 2. Estimation of prey species biomass based on
acoustic surveys.
(Adapted from Murase et al., 2009)

Table 1. Summary of the results of estimation of prey species biomass based on Echosounder.
Sand lance
Biomass (103 t)

Year

Analyzed blocks

Remarks

2005

B, C, E and F

7.61 Murase et al. 2009

2006

B, C, E and F

28.34 Murase et al. 2009

2008

B, C

9.31 This study

2009

B, C

2.83 This study

Japanese anchovy
Biomass (103 t)

Year

Analyzed blocks

2005

B, C, E and F

1.32 Murase et al. 2009

2006

B, C, E and F

9.06 Murase et al. 2009

2008

B, C

0.0002 This study

2009

B, C

0.0006 This study

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Remarks