problems, problems, if if obvious, obvious, are are mentioned. mentioned.

sources sources in in the the acoustic acoustic abundance abundance estimate estimate are are enumerated enumerated and and critiqued. critiqued. Outstanding Outstanding

The The results results are are placed placed in in the the context context of_other of_other methods methods of of assessment assessment and and prognoses. prognoses. Error Error

and and estimates estimates of of confidence confidence associated associated with with the the degree degree of of coverage coverage based based on on geostatistics. geostatistics.

survey survey are are expressed expressed through through absolute absolute numbers numbers for for abundance, abundance, composite composite size size distribution, distribution,

averaging, averaging, and and geostatistical geostatistical estimation estimation of of variance, variance, are are described. described. Results Results of of the the acoustic acoustic

integration. integration. Methods Methods of of analysis: analysis: criteria criteria for for echogram echogram interpretation, interpretation, stratification, stratification, global global

distribution, distribution, (7) (7) inter-ship inter-ship calibration calibration of of echo echo integrators, integrators, and and (8) (8) multi-frequency multi-frequency echo echo

associated associated dynamics, dynamics, ( ( 5) 5) herring herring fat fat content, content, ( ( 6) 6) hydrography hydrography with with respect respect to to herring herring

situ, situ, (3) (3) fish fish target target strength strength in in situ, situ, ( ( 4) 4) geographic geographic differences differences in in size size distribution distribution and and

breifly breifly reviewed. reviewed. The The subjects subjects of of these these are are ( ( 1) 1) acoustic acoustic extinction, extinction, (2) (2) fish fish orientation orientation in in

measurements, measurements, and and biological biological sampling. sampling. A A variety variety of of auxiliary auxiliary studies, studies, some some ongoing, ongoing, are are

biology, biology, principal principal elements elements of of the the survey survey are are described, described, namely namely design, design, acoustic acoustic

by by measurements measurements with with RIV RIV "Michael "Michael Sars" Sars" in in December December 1993. 1993. Following Following a a review review of of the the

from from the the December December 1993 1993 and and January January 1994 1994 cruises cruises with with RIV RIV "Johan "Johan Hjort", Hjort", supplemented supplemented

Conditions Conditions for for measuring measuring the the stock stock size size have have been been excellent. excellent. Here, Here, results results are are presented presented

herring herring have have been been wintering wintering in in a a fjord fjord system system in in northern northern Norway Norway in in recent recent years. years.

The The spawning spawning component component and and part part of of the the juvenile juvenile stock stock of of Norwegian Norwegian spring spring spawning spawning

ABSTRACT ABSTRACT

P.O.Box P.O.Box 1870, 1870, N-5024 N-5024 Bergen, Bergen, Norway Norway

Institute Institute of of Marine Marine Research Research

Ingolf Ingolf Kenneth Kenneth R~ttingen, R~ttingen, G. G. Foote, Foote, Ingvar Ingvar Ruse, Ruse, and and Egil Egil Ona Ona

By By

WITH WITH EMPHASIS EMPHASIS ON ON METHODOLOGICAL METHODOLOGICAL ASPECTS ASPECTS

WINTERING WINTERING NORWEGIAN NORWEGIAN SPRING SPRING SPAWNING SPAWNING HERRING, HERRING,

ACOUSTIC ACOUSTIC ABUNDANCE ABUNDANCE ESTIMATION ESTIMATION OF OF

Fishing Fishing Surveys Surveys and and Acoustic Acoustic Measurements Measurements

Exploration Exploration of of the the Sea Sea Joint Joint Session Session on on Estimating Estimating Abundance Abundance from from

International International

Council Council for for the the C.M. C.M. 1994/(B+D+G+H):1 1994/(B+D+G+H):1

~ ~ (• (•

mentionnes. mentionnes. ete ete ont ont majeurs majeurs problemes problemes les les necessaire, necessaire, Si Si

critiquees. critiquees. et et enumerees enumerees soot soot d'abondance d'abondance acoustique acoustique !'estimation !'estimation dans dans d'erreur d'erreur sources sources Les Les

prevision. prevision. de de et et d'evalution d'evalution methodes methodes d'autres d'autres contexte contexte le le dans dans examines examines soot soot resultats resultats Les Les

geostatistique. geostatistique. la la sur sur base base couverture couverture de de degre degre le le avec avec relation relation en en confiance confiance de de l'intervalle l'intervalle

et et

taille taille en en distribution distribution la la l'abondance, l'abondance, pour pour absolu absolu nombre nombre en en exprimes exprimes soot soot acoustique acoustique

campagne campagne la la de de resultats resultats Les Les geostatistique. geostatistique. variance variance la la de de estimation estimation et et global global moyennage moyennage

stratification, stratification, echogrammes, echogrammes, des des d'interpretation d'interpretation criteres criteres decrites: decrites: soot soot d'analyse d'analyse methodes methodes

differentes differentes Les Les multifrequence. multifrequence. echo-integration echo-integration (8) (8) et et navires navires des des echo-integrateurs echo-integrateurs

des des

intercalibration intercalibration (7) (7) distribution, distribution, la la avec avec relation relation en en hydrologie hydrologie (6) (6) hareng, hareng, du du grasse grasse

matiere matiere de de taux taux (5) (5) tailles, tailles, des des distribution distribution la la dans dans geographiques geographiques differences differences (4) (4) situ, situ,

in­

reflexion reflexion de de index index (3) (3) poissons, poissons, des des in-situ in-situ orientation orientation (2) (2) acoustique, acoustique, extinction extinction 1) 1) ( (

suivants: suivants: point point les les concernent concernent Elles Elles brievement. brievement. decrites decrites soot soot variees variees complementaires complementaires

etudes etudes Des Des biologique. biologique. echantillonnage echantillonnage et et acoustiques acoustiques mesures mesures campagne, campagne, de de

plan plan

decrits: decrits: soot soot campagne campagne la la de de elements elements principaux principaux les les biologie, biologie, la la de de revue revue un un Apres Apres

93. 93.

decembre decembre en en Sars Sars Michael Michael R.V. R.V. le le par par effectuees effectuees mesures mesures des des par par completees completees Hjort, Hjort, Johan Johan

R.V. R.V.

le le par par 94 94 janvier janvier et et 93 93 decembre decembre en en effectuees effectuees campagnes campagnes de de resultats resultats les les presentes presentes

soot soot

note, note, cette cette Dans Dans excellentes. excellentes. etaient etaient stock stock du du l'abondance l'abondance evaluer evaluer pour pour conditions conditions

Les Les

annees. annees. quelques quelques depuis depuis Norvege Norvege la la de de nord nord du du fjord fjord un un dans dans hivernent hivernent printemps, printemps,

au au frayant frayant hareng, hareng, stock stock du du juveniles juveniles des des partie partie qu'une qu'une ainsi ainsi adulte adulte composante composante La La

Resume Resume

methodologiques methodologiques aspects aspects les les sur sur institant institant en en

printempts, printempts, au au frayant frayant norvegien, norvegien, hareng hareng de de hivernal hivernal stock stock du du

l'abondance l'abondance de de acoustique acoustique Evaluation Evaluation

weather). weather). Further, Further, admixture admixture with with other other species species is is almost almost negligible. negligible.

confined confined

to to a a

limited limited

geographical geographical

region region which which is is protected protected from from the the ocean ocean (and (and bad bad

estimation estimation

using using

echo echo

integrator integrator

techniques. techniques. This This is is because because the the stock stock at at that that time time is is

The The

wintering wintering

period period seems seems to to be be the the most most suitable suitable period period for for acoustic acoustic abundance abundance

December-beginning December-beginning

of of January, January, the the herring herring start start their their spawning spawning migration. migration.

Vestfjorden Vestfjorden

in in

northern northern

Norway, Norway,

i.e., i.e., Ofotfjorden Ofotfjorden and and Tysfjorden Tysfjorden (Fig. (Fig. 1). 1). At At the the end end of of

Norwegian Norwegian

spring spring

spawning spawning

herring herring have have been been located located in in the the inner inner tributary tributary fjords fjords of of

where where

they they concentrate concentrate

at at high high densities. densities. Since Since 1987/88 1987/88 the the wintering wintering areas areas of of the the

In In

August, August,

after after

the the end end of of

the the feeding feeding season, season, the the herring herring migrate migrate to to the the wintering wintering areas areas

layer layer of of the the water water masses, masses, where where they they feed feed mainly mainly on on copepods. copepods.

areas areas

in in

the the open open ocean ocean

(RfZjttingen (RfZjttingen

1992). 1992). The The herring herring are are mostly mostly distributed distributed in in the the upper upper

the the

Norwegian Norwegian Sea, Sea,

where where

they they feed feed in in summer summer in in scattered scattered concentrations concentrations over over large large

banks banks of of the the

west west

and and

northwest northwest

coast coast of of Norway. Norway. After After spawning, spawning, the the herring herring migrate migrate to to

The The Norwegian Norwegian

spring spring

spawning spawning herring herring stock stock spawns spawns in in February-March February-March on on the the coastal coastal

MIGRATION MIGRATION BIOLOGY BIOLOGY

too. too.

abundance abundance

and, and,

through through

improvements improvements

in in methodology, methodology, those those of of other other pelagic pelagic fish fish stocks stocks

reviewed. reviewed.

Progress Progress

on on these these is is important important for for improving improving estimates estimates of of herring herring stock stock

is is

called called

particularly particularly

to to the the final final

part part of of the the discussion, discussion, in in which which outstanding outstanding problems problems are are

principal principal

methods, methods,

auxiliary auxiliary

studies, studies, methods methods of of analysis, analysis, results, results, and and discussion. discussion. Attention Attention

This This

paper paper

is is divided divided

into into the the following following sections: sections: migration migration biology, biology, materials materials and and

elaboration, elaboration,

and and some some have have already already been been prepared prepared and and are are duly duly cited cited below. below.

auxiliary auxiliary

studies studies are are

outlined. outlined.

Each Each of of these these studies studies may may require require a a separate separate paper paper for for

cruises cruises

is is summarized summarized

here. here.

In In particular, particular, estimates estimates of of stock stock abundance abundance are are given, given, and and

survey survey

and and

research research

cruises cruises

in in December December 1993 1993 and and January January 1994. 1994. The The major major work work of of these these

The The Institute Institute

of of Marine Marine

Research Research has has accepted accepted these these conclusions conclusions in in authorizing authorizing acoustic acoustic

integral integral part part of of the the apparently apparently more more routine routine work work of of surveying. surveying.

and and

acoustic acoustic scattering scattering

properties. properties.

That That is, is, development development of of methodology methodology is is viewed viewed as as an an

that that

auxiliary auxiliary

studies studies

are are essential essential for for improving improving knowledge knowledge of of fish fish biology, biology, behaviour, behaviour,

the the

conditions conditions

for for

performing performing

an an acoustic acoustic abundance abundance survey survey of of herring herring are are excellent, excellent, and and

Principal Principal

conclusions conclusions

drawn drawn

from from these these and and other other survey survey cruises cruises to to the the same same area area are are that that

and and

from from a a

briefer briefer

cruise cruise

to to the the same same area area in in December December 1991 1991 (Foote (Foote et et al. al. 1992a, 1992a, 1993). 1993).

dependence dependence

of of target target

strength strength

have have also also been been documented, documented, both both from from the the mentioned mentioned cruise cruise

December December

1992 1992

has has

been been documented documented (Foote (Foote 1993). 1993). Adjunct Adjunct studies studies on on the the frequency frequency

Abundance Abundance

estimation estimation

of of the the stock stock according according to to the the acoustic acoustic survey survey performed performed in in

surveyed surveyed

while while

wintering wintering

in in

the the Ofotfjord- Tysfjord Tysfjord system system in in northern northern Norway Norway (Fig. (Fig. 1 1 ). ).

In In recent recent

years, years,

the the stock stock of of Norwegian Norwegian spring spring spawning spawning herring herring has has been been acoustically acoustically

INTRODUCTION INTRODUCTION 3 3

migration. migration. spawning spawning the the start start herring herring the the when when

December December of of end end

the the at at

resumed resumed however, however, are, are, migrations migrations These These migrations. migrations. horizontal horizontal

limited limited

only only be be

to to

seem seem

there there

November, November, of of middle middle the the from from month month one one of of period period a a In In

1994. 1994.

January January and and

1993 1993

December December in in Tysfjorden Tysfjorden to to tributaries tributaries fjord fjord different different herring from from herring

of of

distributions distributions

length length

shows shows

which which 2c, 2c, Fig. Fig. in in illustrated illustrated is is This This separately. separately. occur occur older older

the the

and and

young young the the

areas areas

other other in in

older, older, the the with with mix mix herring herring young young the the areas areas some some In In area. area.

wintering wintering the the in in

herring herring older older the the

joined joined have have herring herring younger younger the the November November of of beginning beginning

the the in in

and and

tributraries, tributraries,

inner inner the the reached reached have have herring herring the the October, October, of of end end the the By By

fish. fish. immature immature

younger, younger, by by

replaced replaced

been been have have

fjord fjord the the of of part part outer outer the the in in herring herring older older the the December December

by by that that

indicating indicating 1993, 1993,

December December in in and and October October of of beginning beginning the the at at Tysfjorden Tysfjorden of of outlet outlet

the the

in in

herring herring

the the of of

distribution distribution

age age and and length length the the gives gives 2b 2b Figure Figure first. first. arriving arriving herring herring

older older

the the

Tysfjorden, Tysfjorden,

and and

Ofotfjorden Ofotfjorden enter enter herring herring the the October, October, of of beginning beginning the the In In

2a). 2a).

(Fig. (Fig.

migration migration

this this of of

front front the the at at catches catches the the in in dominate dominate herring herring Older Older fishery. fishery.

the the

in in

development development

geographical geographical corresponding corresponding a a by by followed followed is is This This eastwards. eastwards. moves moves

gradually gradually

migration migration the the

of of

front front the the and and Vestfjorden, Vestfjorden, enter enter herring herring the the September September By By

summer. summer.

in in

feeding feeding for for areas areas these these utilize utilize which which herring herring immature immature ecounter ecounter

herring herring

adult adult

the the

Here, Here,

VestedHen. VestedHen. of of west west concentrations concentrations increasing increasing in in appear appear and and Sea Sea

Norwegian Norwegian the the

in in

areas areas

feeding feeding the the from from eastwards eastwards migrate migrate herring herring adult adult the the August August In In

areas areas wintering wintering the the to to Immigration Immigration a) a)

ppt. ppt.

34-35 34-35 of of salinity salinity a a and and 5-7°C 5-7°C of of temperature temperature a a with with masses masses

water water in in winter winter

herring herring the the

speaking, speaking, Generally Generally (1994). (1994). al. al. et et Dommasnes Dommasnes in in discussed discussed is is

situation, situation,

oxygen oxygen the the on on

emphasis emphasis special special with with fjords, fjords, these these of of situation situation hydrographic hydrographic The The

m. m.

450 450 to to

down down

depths depths

have have others others waters, waters, shallow shallow relatively relatively have have these these of of some some

tributaries, tributaries,

many many

has has fjord fjord

The The Ofotfjorden. Ofotfjorden. in in than than complicated complicated more more are are topography topography

general general

and and

bottom bottom both both but but

m, m, 900 900 to to down down depths depths has has basin basin fjord fjord The The Vestfjorden. Vestfjorden.

against against

outlet outlet the the in in

m m 200 200 about about of of sill sill a a has has and and north-south north-south runs runs Tysfjorden Tysfjorden

places. places. in in flat flat remarkably remarkably is is which which m, m, 550 550 about about of of depth depth

a a

with with

basin basin

narrow narrow and and long long

27-km 27-km a a is is there there sill sill the the inside inside Just Just BarS!)y. BarS!)y. at at Vestfjorden Vestfjorden

towards towards m m

320 320

about about of of

sill sill a a

has has

It It km. km. 10 10 is is width width maximum maximum The The axis. axis. east-west east-west an an has has

and and

long long

km km 65 65 is is

It It

1). 1). (Fig. (Fig. area area Vestfjord Vestfjord the the of of part part inner inner the the at at situated situated is is Ofotfjorden Ofotfjorden

areas areas Wintering Wintering

estimation. estimation.

abundance abundance

acoustic acoustic in in

significance significance of of are are factors factors These These content. content. fat fat decreasing decreasing

and and

maturation, maturation,

gonad gonad

distributions), distributions), angle angle tilt tilt associated associated in in changes changes likely likely (with (with

horizontal horizontal and and diurnal diurnal both both

migrations, migrations, as as such such occur, occur, changes changes homogenous. Dynamic Dynamic homogenous.

and and static static

as as

regarded regarded be be

not not should should area area wintering wintering the the in in situtation situtation the the However, However, 4 4

migration migration is is observed. observed.

located located in in deeper deeper water water masses masses than than during during the the immigration. immigration. Only Only limited limited diurnal diurnal

herring herring

are are located located in in the the outer outer part part of of the the wintering wintering area area (Fig. (Fig. 3a). 3a). The The older older herring herring are are

Figure Figure

4c 4c shows shows the the emigration emigration situation. situation. The The older older herring herring emigrate emigrate first, first, thus thus the the older older

separately separately (Fig. (Fig. 2c). 2c). Diurnal Diurnal migration migration is is observed. observed.

in in the the

inner inner parts parts of of the the wintering wintering area. area. In In some some areas areas they they mix, mix, in in some areas areas some they they occur occur

Figure Figure

4b 4b shows shows the the situation situation in in December. December. Both Both older older and and immature immature herring herring are are located located

2b 2b ). ). A A diurnal diurnal migration migration is is observed observed during during the the immigration. immigration.

immigrating immigrating

to to the the wintering wintering areas. areas. The The older older herring herring enter enter the the wintering wintering areas areas first first (Fig. (Fig.

schematically schematically

in in Fig. Fig. 4. 4. Figure Figure gives gives 4a the the situation situation in in October October while while the the herring herring is is

The The general general migration migration dynamics dynamics of of the the wintering wintering situations situations is is illustrated illustrated highly highly

zooplankton zooplankton spring spring bloom bloom commences commences in in the the coastal coastal areas. areas.

immature immature are are left. left. These These will will migrate migrate out out of of the the fjord fjord in in a a feeding feeding migration migration as as the the

In In February February most most of of the the maturing maturing herring herring have have left left the the wintering wintering area, area, and and only only the the

wintering wintering areas areas and and are are located located in in the the outer outer part, part, taking taking part part in in the the spawning spawning migration. migration.

figures figures

show show that that by by the the middle middle of of January January the the older older herring herring have have left left the the inner inner part part of of the the

and and

outer outer part part of of the the wintering wintering area area in in the the period period 11 11 - 16 16 January January 1994 1994 (Fig. (Fig. 3b). 3b). The The

and and

16 16 January January (Fig. (Fig. 3a), 3a), and and by by the the length length distrubution distrubution of of herring herring from from the the inner, inner, middle middle

sampled sampled

from from the the inner inner part part of of the the wintering wintering area area (off (off Narvik) Narvik) on on 1 1 December December 1993, 1993, 10 10

The The progress progress of of emigration emigration is is illustrated illustrated by by the the change change in in length length distribution distribution of of herring herring

herring herring remain remain in in the the inner inner part part of of the the wintering wintering area. area.

herring herring undertake undertake diurnal diurnal migrations migrations only only to to a a limited limited degree. degree. In In January January the the immature immature

is is probably probably related related to to the the currents currents of of the the water water masses masses in in the the fjord. fjord. The The outward outward migrating migrating

fish. fish.

This This emigration emigration takes takes place place in in deeper deeper water water masses masses than than does does the the immigration. immigration. This This

The The

general general situation situation in in the the wintering wintering areas areas in in January January is is thus thus an an emigration emigration of of the the older older

individuals individuals of of the the spawning spawning stock stock (Lambert (Lambert 1987, 1987, Ware Ware and and Tanasichuk Tanasichuk 1989). 1989).

individuals individuals have have a a more more rapid rapid maturation maturation rate rate than than first-time first-time spawners spawners and and younger younger

wintering wintering

areas. areas. This This is is in in agreement agreement with with earlier earlier investigations, investigations, showing showing that that the the older older

As As with with immigration, immigration, the the older older individuals individuals dominate dominate the the migration migration front front out out of of the the

The The older older individuals individuals are are the the first first to to commence commence the the emigration. emigration.

December, December, perhaps perhaps earlier, earlier, marking marking the the start start of of the the spawning spawning migration. migration.

The The

first first individuals individuals probably probably start start emigrating emigrating from from the the wintering wintering area area in in the the latter latter part part of of

b) b) Emigration Emigration from from the the wintering wintering areas areas 5 5

both both

ensure ensure to to

Skjomen Skjomen example, example, for for included included These These areas. areas. interesting interesting other other in in employed employed

were were

designs, designs,

parallel parallel and and zigzag zigzag of of variants variants and and design, design, broad-scale broad-scale first, first, the the of of Parts Parts

(NM). (NM). miles miles nautical nautical 0.5 0.5 of of distance distance

intra-transect intra-transect

with with 'E, 'E, 17°16.1 17°16.1 to to .5'E .5'E 16°19 16°19 from from extended extended 1994 1994 January January in in Ofotfjorden Ofotfjorden

in in

used used

transects transects parallel parallel of of design design basic basic The The Tysfjorden. Tysfjorden. of of part part central central the the in in also also

but but

Ofotfjorden, Ofotfjorden,

namely namely concentration, concentration, largest largest of of regions regions the the in in transects transects spaced spaced equally equally

parallel, parallel, of of

designs designs in in

consist consist these these 1994, 1994, January January and and 1993 1993 December December in in cruises cruises particular particular

the the

For For

developed. developed. were were designs designs survey survey denser denser further, further, fishery, fishery, local local the the and and trawling trawling

from from

knowledge knowledge with with supplemented supplemented survey, survey, first first the the from from findings findings of of basis basis the the On On

hours. hours. 24 24 about about in in Tysfjorden Tysfjorden and and hours hours 15 15 about about

in in

covered covered

be be can can

Skjomen Skjomen and and Rombaken Rombaken including including Ofotfjorden Ofotfjorden knots, knots, eight eight of of speed speed

vessel vessel

a a At At

fjord. fjord.

the the in in herring herring the the of of movements movements large-scale large-scale to to compared compared short short are are that that

periods periods

time time in in

surveyed surveyed be be areas areas fjord fjord or or fjords fjords individual individual that that and and days, days, ten ten about about within within

completed completed be be

measurements measurements auxiliary auxiliary any any and and survey survey the the that that were were this this on on Constraints Constraints

time. time. reasonable reasonable

a a in in distribution distribution herring herring the the of of coverage coverage broad-scale broad-scale comprehensive comprehensive

a a

ensure ensure

to to

attempt attempt fjords fjords both both for for patterns patterns The The (IR). (IR). author author first first the the by by design design earlier earlier

an an on on

based based

is is but but

1993), 1993), (Foote (Foote 1992 1992 December December in in used used first first was was Ofotfjorden Ofotfjorden for for pattern pattern

zigzag zigzag The The

5. 5.

Fig. Fig. in in

indicated indicated tracks tracks the the along along conducted conducted was was survey survey first-time first-time basic basic The The

Tysfjorden. Tysfjorden.

and and

Ofotfjorden Ofotfjorden of of coverages coverages repeated repeated in in employed employed were were grids grids survey survey Various Various

design design Survey Survey

fishery. fishery. herring herring on-going on-going the the in in participating participating boats boats fishing fishing

commercial commercial from from

samples samples by by supplemented supplemented were were catches catches Own-vessel Own-vessel trawling. trawling. performed performed

also also which which

vessels, vessels, both both by by measured measured were were profiles profiles (STD) (STD) Salinity-temperature-depth Salinity-temperature-depth

measurements. measurements.

photographic photographic and and acoustic acoustic special special to to addition addition in in exercise, exercise, calibration calibration

acoustic acoustic an an

and and concentration, concentration, dense dense of of regions regions of of surveys surveys finer-scale finer-scale additional, additional,

fjords, fjords, both both

of of survey survey large-scale large-scale a a of of consisted consisted These These 1994. 1994. January January 6-17 6-17 cruise, cruise,

second second

the the

during during

system system fjord fjord the the in in measurements measurements performed performed Hjort" Hjort" "Johan "Johan R1V R1V Only Only

calibrations. calibrations. inter-ship inter-ship and and calibration calibration

acoustic acoustic

an an

to to addition addition

in in areas, areas, certain certain in in repeated repeated surveys, surveys, acoustic acoustic of of series series a a performed performed

vessel vessel

second second This This Hjort". Hjort". "Johan "Johan RN RN with with calibrations calibrations inter-ship inter-ship and and calibration calibration

acoustic acoustic

an an to to

addition addition in in measurements measurements environmental environmental and and acoustic acoustic special special of of series series

a a

performed performed

then then

Sars" Sars" "Michael "Michael RN RN cruises. cruises. respective respective their their of of beginning beginning the the at at design, design,

survey survey same same the the

on on based based system, system, fjord fjord the the of of surveys surveys acoustic acoustic large-scale large-scale performed performed

vessels vessels Both Both

December. December. 4-15 4-15 period period the the during during Hjort" Hjort" "Johan "Johan RN RN and and December, December,

November-15 November-15 29 29 period period the the during during operated operated Sars" Sars" "Michael "Michael RN RN Tysfjorden: Tysfjorden: and and

Ofotfjorden Ofotfjorden in in

measurements measurements 1993 1993 December December the the in in involved involved were were vessels vessels research research Two Two

operations operations Vessel Vessel

METHODS METHODS AND AND MATERIALS MATERIALS 6 6

at at 38, 38, 120, 120, and and 200 200 kHz, kHz, are, are, respectively, respectively, ±0.2, ±0.2, ±0.5, ±0.5, and and ±0.5 ±0.5 dB. dB.

transducer transducer at at 18 18 kHz kHz was was difficult, difficult, with. with. estimated estimated uncertainty uncertainty of of ±1 ±1 dB. dB. The The uncertainties uncertainties

earlier earlier occasions, occasions, for for example, example, that that described described by by Foote Foote et et al. al. ( ( 1993), 1993), calibration calibration of of the the

previous previous year, year, consistent consistent with with the the basic basic level level of of uncertainty uncertainty in in calibration calibration state. state. As As on on

The The instruments instruments had had performed performed stably, stably, with with insignificant insignificant change change in in performance performance over over the the

38-mm-diameter 38-mm-diameter sphere sphere of of tungsten tungsten carbide carbide with with 6% 6% cobalt cobalt binder binder at at 120 120 and and 200kHz. 200kHz.

125-mm-diameter 125-mm-diameter copper copper sphere sphere at at 18kHz, 18kHz, 60-mm-diameter copper copper 60-mm-diameter sphere sphere at at 38kHz, 38kHz, and and

target target method method recommended recommended by by ICES ICES (Foote (Foote et et al. al. 1987). 1987). The The calibration calibration targets targets were were the the

The The acoustic acoustic instruments instruments were were calibrated calibrated during during each each cruise cruise according according to to the the standard­

described described in in the the section section on on analysis analysis methods. methods.

24 24 hours hours of of collection, collection, and and often often within within four four hours. hours. The The process process of of interpretation interpretation is is

All All postprocessing postprocessing was was performed performed on on BEL BEL Survey Survey data data were were generally generally interpreted interpreted within within

resolution. resolution.

region region from from 10 10 m m over over the the detected detected bottom bottom to to 5 5 m m under under the the same, same, with with 0.1-m 0.1-m depth depth

such such time time series series was was supplemented supplemented by by a a near-bottom near-bottom time time series series of of values values covering covering the the

resolution resolution in in depth depth over over the the 500-m 500-m range range and and 2-m 2-m resolution resolution over over the the 1000-m 1000-m range. range. Each Each

data data consisted consisted of of digitized digitized time time series series of of the the volume volume backscattering backscattering strength, strength, with with 1-m 1-m

indentifying indentifying data data as as vessel vessel log log and and Global Global Positioning Positioning System System (GPS) (GPS) coordinates. coordinates. Survey Survey

Data Data from from the the EK500 EK500 system system were were automatically automatically logged logged on on BEl BEl together together with with such such

beam beam devices. devices.

short-range short-range measurements. measurements. Both Both 38-kHz 38-kHz transducers transducers and and the the 120-kHz 120-kHz transducer transducer are are split­

were were used used during during surveying. surveying. The The towed towed 38-kHz 38-kHz transducer transducer was was used used during during some some special special

The The cruising cruising speed speed during during surveying surveying was was about about eight eight knots. knots. Hull-mounted Hull-mounted transducers transducers

measurements measurements were were performed performed at at 18, 18, 120, 120, and and 200 200 kHz, kHz, in in addition addition to to 38 38 kHz. kHz.

general, general, two two EK500 EK500 systems systems were were operated operated concurrently, concurrently, each each with with two two transducers. transducers. Thus Thus

the the bottom bottom depth, depth, which which was was often often in in excess excess of of 500 500 m, m, and and use use of of multiple multiple frequencies. frequencies. In In

kHz. kHz. The The pulse pulse repetition repetition frequency frequency was was nominally nominally about about 1/s, 1/s, but but this this was was dependent dependent on on

The The primary primary frequency frequency was was 38 38 kHz, kHz, with with pulse pulse duration duration 1 1 ms ms and and receiver receiver bandwidth bandwidth 3.8 3.8

made made with with both both vessels, vessels, but but only only those those made made with with R/V R/V "Johan "Johan Hjort" Hjort" are are analyzed analyzed here. here.

and and Bergen Bergen Echo Echo Integrator Integrator (BEl) (BEl) (Foote (Foote et et al. al. 1991). 1991). Large-scale Large-scale measurements measurements were were

These These were were made made with with the the SIMRAD SIMRAD EK500 EK500 echo echo sounder sounder system system (Bodholt (Bodholt et et al. al. 1989) 1989)

Principal Principal acoustic acoustic measurements measurements

December December 1992 1992 survey, survey, affected affected the the placement placement of of transects, transects, hence hence design. design.

instance, instance, the the lowering lowering of of a a power power line line from from 35 35 m m to to 26 26 m m over over high high water water since since the the

and and KjS!)psviksundet. KjS!)psviksundet. In In designing designing a a finer-scale finer-scale system system of of transects transects for for Hy11S!)ysund, Hy11S!)ysund, for for

daytime daytime and and night-time night-time coverages, coverages, and and such such navigationally navigationally difficult difficult areas areas as as HullS!)ysundet HullS!)ysundet 7 7

from from measured measured were were Angles Angles release. release. automatic automatic or or manual manual with with either either taken taken were were Pictures Pictures

illumination. illumination. strobe strobe with with equipment equipment underwater underwater using using measured measured were were angles angles tilt tilt Herring Herring

situ situ in in orientation orientation Fish Fish

1987). 1987). (Foote (Foote herring herring spawning spawning

spring spring Norwegian Norwegian for for used used one one standard standard the the is is relation relation The The TS-l TS-l centimeters. centimeters. in in length length fish fish

0 0 rms rms the the denotes denotes and and l l m, m, 1 1 of of distance distance reference reference the the is is strength, strength, target target denotes denotes r r TS TS where where

r r 41t 41t o o

2 2

= = 71.9, 71.9, - log log l l 20 20

log-- 10 10 TS TS

oh oh

for for equation equation ab' ab'

defining defining the the through through size size fish fish to to a a related related is is of of value value absolute absolute The The 2.41. 2.41. be be e e to to assumed assumed

is is I I section, section, cross cross ab' ab' a a backscattering backscattering and and e e extinction extinction of of ratio ratio mean mean the the below, below, reported reported

computation computation the the in in Thus, Thus, section. section. cross cross backscattering backscattering the the with with associated associated that that as as limited limited

as as least least at at is is this this of of knowledge knowledge distribution, distribution, orientation orientation e.g., e.g., behaviour, behaviour, and and maturation, maturation,

of of degree degree size, size, fish fish depth, depth, on on depends depends undoubtedly undoubtedly section section cross cross extinction extinction the the While While

cm. cm. 3.2 3.2 deviation deviation standard standard and and 34.0, 34.0, root-mean-square root-mean-square 33.9, 33.9, mean mean with with

distribution distribution length length herring herring for for cm 22.7 22.7 is is section section cross cross extinction extinction the the terms, terms, absolute absolute In In

2 2

2.41±0.33. 2.41±0.33. is is sections sections cross cross backscattering backscattering and and extinction extinction of of ratio ratio the the that that suggests suggests analysis analysis

Statistical Statistical layer. layer. fish fish intervening intervening the the to to due due echo echo bottom bottom of of diminution diminution the the demonstrated demonstrated

Ofotfjorden Ofotfjorden outer outer in in bottom bottom flat flat and and layer layer herring herring the the of of integration integration echo echo pairwise pairwise brief, brief, In In

1994). 1994). (Foote (Foote elsewhere elsewhere

detail detail in in described described are are this this of of Results Results anew. anew. performed performed was was measurement measurement the the 1991, 1991,

and and 1990, 1990, 1988, 1988, in in measured measured was was section section cross cross extinction extinction the the when when state state class-dominated class-dominated

1983-year­ its its to to relative relative stock stock herring herring the the of of composition composition different different the the Given Given ). ). 1992b 1992b al. al.

et et (Foote (Foote earlier earlier employed employed method method a a to to according according section section cross cross extinction extinction the the measuring measuring

for for suitable suitable also also were were Conditions Conditions necessary. necessary. compensation compensation make make and and extinction extinction acoustic acoustic

significant significant cause cause to to extended extended and and dense dense sufficiently sufficiently often often were were herring herring of of Concentrations Concentrations

extinction extinction Acoustic Acoustic

STUDIES STUDIES AUXILIARY AUXILIARY

fishery. fishery. commercial commercial the the from from 26 26 and and vessel vessel research research by by

taken taken were were samples samples 18 18 these, these, Of Of taken. taken. were were herring, herring, 100 100 of of consisting consisting each each samples, samples, 44 44

Altogether Altogether respectively. respectively. 1994, 1994, January January and and 1993 1993 October-December October-December in in locations locations sampling sampling

the the show show b b and and 6a 6a Figures Figures seine). seine). (purse (purse fishery fishery commercial commercial the the from from catches catches from from

and and (trawl) (trawl) catches catches vessel vessel research research from from originate originate herring herring the the of of samples samples biological biological The The

sampling sampling Biological Biological 8 8

abundance, abundance, because because the the conversion conversion factor factor is is length length (TS) (TS) dependent. dependent.

into into account account when when converting converting the the average average backscattering backscattering cross cross section section to to herring herring

wintering wintering area area vary vary throughout throughout the the wintering wintering period period (Figs. (Figs. 2 2 and and 3). 3). This This must must be be taken taken

these these migrations, migrations, the the length length and and age age distributions distributions of of herring herring in in the the different different parts parts of of the the

previous previous section section (Migration (Migration pattern pattern of of Norwegian Norwegian spring spring spawning spawning herring). herring). As As a a result result of of

The The basic basic dynamics dynamics of of the the migrations migrations to to and and from from the the wintering wintering areas areas is is described described in in a a

Geographic Geographic differences differences in in size size distribution distribution and and associated associated dynamics dynamics

(Kautsky (Kautsky et et al. al. 1990, 1990, Reynisson Reynisson 1993). 1993).

biomass biomass calculations calculations and and in in situ situ target target strength strength data data are are also also discussed discussed in in other other reports reports

The The findings findings of of a a large large difference difference between between the the applied applied target target strength-length strength-length relation relation for for

integration. integration.

the the target target strength strength values values obtained obtained from from combined combined individual individual countings countings and and echo echo

These These high high target target strengths strengths measured measured in in situ situ using using a a split split -beam -beam system system are are comparable comparable to to

strength-length strength-length relation relation as as presently presently applied applied in in biomass biomass calculations calculations 20 20 = = logL- (TS (TS 71.9). 71.9).

target target strength strength of of herring herring is is significantly significantly higher higher than than what what is is deduced deduced from from the the target target

Preliminary Preliminary analysis analysis of of the the data data sampled sampled within within the the herring herring layers layers indicates indicates that that the the in in situ situ

results results from from these these experiments experiments are are reported reported elsewhere. elsewhere.

counting counting methods. methods. The The three three systems systems were were calibrated calibrated several several times times during during the the survey. survey. The The

individual individual fish fish for for target target strength strength measurements measurements and and to to measure measure volume volume density density by by

scanning scanning sonar, sonar, and and Photosea Photosea stereo stereo camera, camera, was was lowered lowered into into the the herring herring layers layers to to resolve resolve

cabled cabled rig rig containing containing a a SIMRAD SIMRAD EKSOO EKSOO split-beam split-beam transducer, transducer, SIMRAD SIMRAD FS3300 FS3300

Herring Herring target target strength strength was was studied studied by by in in situ situ techniques techniques from from RIV RIV "Michael "Michael Sars". Sars". A A

Fish Fish target target strength strength in in situ situ

further further addressed addressed in in Ruse Ruse et et al. al. (1994). (1994).

tilt tilt angle angle measurements measurements made made in in December December and and January. January. The The tilt tilt angle angle measurements measurements are are

studies studies as as when when the the ship ship is is drifting. drifting. There There seems seems to to be be no no systematic systematic difference difference between between

whether whether the the tilt tilt angle angle distribution distribution is is the the same same in in the the survey survey situation situation as as it it is is during during such such

obviously obviously have have a a strong strong impact impact on on Further Further TS. TS. investigation investigation is is therefore therefore needed needed to to find find

to to swim swim at at an an upward upward angle angle in in order order to to maintain maintain depth. depth. The The observed observed tilt tilt angles angles will will

the the low low bouyancy bouyancy resulting resulting from from the the compressed compressed swimbladder, swimbladder, the the herring herring therefore therefore have have

may may be be that that at at night night the the fish fish swim swim more more slowly slowly than than at at daytime daytime and and do do not not school. school. With With

less less than than 1120 1120 of of its its surface surface volume. volume. A A possible possible explanation explanation for for the the difference difference in in tilt angle angle tilt

observations observations are are from from below below 200 200 m m depth. depth. Consequently Consequently the the swimbladder swimbladder is is compressed compressed to to

majority majority of of the the herring herring are are swimming swimming with with a a pronounced pronounced upward upward tilt. tilt. Both Both sets sets of of

Most Most herring herring are are swimming swimming horizontally. horizontally. Fig. Fig. 7b 7b shows shows a a night night situation. situation. Here Here the the

of of the the picture picture vertically vertically were were measured. measured. A A typical typical day day situation situation is is presented presented in in Fig.7a. Fig.7a.

Only Only herring herring visually visually evaluated evaluated to to swim swim parallel parallel to to the the picture picture plane plane and and in in the the central central 1/3 1/3

copied copied positives positives using using a a specially specially developed developed Autocad Autocad programme programme and and a a digitizing digitizing tablet. tablet. 9 9

depths, depths, same same the the at at method method Winkler Winkler the the using using measurements measurements and and CTD CTD the the by by

oxygen oxygen measured measured between between regression regression linear linear a a by by made made was was oxygen oxygen recorded recorded continously continously

the the of of correction correction A A 9). 9). (Fig. (Fig. stations stations 35 35 the the of of most most at at method method Winkler Winkler the the using using

depths depths 15 15 to to 10 10 from from at at samples samples water water discrete discrete against against compared compared were were measurements measurements

oxygen oxygen recorded recorded The The sensor. sensor. oxygen oxygen with with probe probe CTD CTD + + 911 911 Seabird Seabird a a using using measured measured

were were oxygen oxygen dissolved dissolved and and salinity, salinity, temperature, temperature, as as such such variables variables Environmental Environmental

distribution distribution herring herring to to respect respect with with Hydrography Hydrography

1993/94. 1993/94. period period wintering wintering the the in in content content fat fat in in variation variation the the shows shows 8 8 Figure Figure survey. survey.

January January the the %in %in 15 15 to to decreasing decreasing 16%, 16%, was was survey survey November/December November/December the the during during

4 4 2 herring herring of of content content fat fat mean mean The The extraction. extraction. ether ether ethyl ethyl with with grinding grinding S0 Na is is content content

fat fat the the determining determining for for used used method method The The in in plant plant production production Bod~. Bod~. meal meal a a at at delivered delivered

catches catches seine seine purse purse from from determined determined was was area area survey survey the the in in herring herring the the of of content content fat fat The The

content content fat fat Herring Herring

1). 1). Table Table 6b, 6b, Fig. Fig. J, J, and and I I (strata (strata

17°E 17°E of of west west and and east east strata, strata, two two into into divided divided was was Ofotfjorden Ofotfjorden Consequently, Consequently, b). b). and and 3a 3a

(Figs. (Figs. eastern eastern the the in in younger younger and and fjord fjord the the of of part part western western the the in in distributed distributed were were herring herring

larger larger the the so so Ofotfjorden, Ofotfjorden, of of out out migrating migrating were were herring herring mature mature large, large, the the January, January, In In

adjustments. adjustments.

minor minor with with data data acoustic acoustic 1994 1994 January January the the of of estimation estimation abundance abundance the the for for applied applied

was was 1993 1993 December December from from stratification stratification the the D), D), (stratum (stratum Ofotfjorden Ofotfjorden of of exception exception the the With With

survey survey 1994 1994 January January b) b)

b). b). and and 3a 3a (Figs. (Figs. 1990) 1990) and and 1989 1989 1988, 1988, classes classes year year the the (mainly (mainly Ofotfjord Ofotfjord

entire entire the the in in classes classes year year younger younger and and class class year year 1983 1983 the the of of mixture mixture a a December December in in

were were there there herring, herring, immature immature with with E) E) (stratum (stratum Skjomen Skjomen tributary tributary the the of of exception exception the the With With

2c). 2c).

(Fig. (Fig. basin basin main main the the in in as as herring herring large large same same the the were. were. there there (Hellemofjorden) (Hellemofjorden) tributaries tributaries

other other In In 2c). 2c). (Fig. (Fig. herring herring immature immature partly partly and and younger younger of of consentrations consentrations were were there there

however, however, B), B), (stratum (stratum Tysfjorden Tysfjorden Indre Indre and and Stefjorden Stefjorden fjords fjords tributary tributary the the In In 2b. 2b. Fig. Fig. in in

shown shown is is herring herring of of type type this this of of distribution distribution age age and and length length typical typical class. class. A A year year 1983 1983 the the

of of herring herring mainly mainly were were 6a) 6a) Fig. Fig. A, A, (stratum (stratum Tysfjorden Tysfjorden in in basin basin main main the the in in herring herring The The

survey survey 1993 1993 December December a) a)

1. 1. Table Table

in in given given are are strata strata different different the the in in herring herring the the of of length length mean mean on on data data and and b, b, and and 6a 6a

Figs. Figs. shown in in shown are are These These 1994). 1994). January January in in survey survey corresponding corresponding the the for for six six survey, survey, 1993 1993

December December the the for for strata strata (five (five strata strata into into divided divided is is area area distribution distribution herring herring total total the the Thus Thus 10 10

separately separately and and from from the the combined combined transects. transects.

different different from from zero. zero. The The same same results results apply apply to to the the data data from from each each transect transect treated treated

entire entire water water column column is is that that is is not not significantly significantly a a different different from from unity, unity, nor nor is is significantly significantly b b

were were determined determined by by ordinary ordinary linear linear regression regression analysis. analysis. The The result result for for applicable applicable to to the the sA sA

variables variables are are denoted denoted and and x, x, then then the the coefficients coefficients y y a a and and in in b b the the equation equation + + ax ax = = b b y y

namely namely for for R/V R/V "Michael "Michael Sars" Sars" on on that that for for sA sA RIV RIV "Johan "Johan Hjort". Hjort". If If the the respective respective

analysis analysis was was performed performed of of corresponding corresponding values values area area of backscattering backscattering coefficient coefficient sA' sA'

inevitable inevitable differences differences in in corresponding corresponding positions positions of of the the vessels. vessels. A A linear linear regression regression

resolution. resolution. These These values values were were further further averaged averaged over over 0.2-NM 0.2-NM intervals intervals to to help help alleviate alleviate

Data Data collection collection by by the the two two vessels vessels were were analysed analysed in in the the customary customary manner, manner, with with 0.1-NM 0.1-NM

the the two two transects. transects.

other other with with distance distance of of 1 1 NM NM between between vessels. vessels. The The lead lead was was exchanged exchanged after after the the first first of of

its its end, end, covering covering a a depth depth range range from from about about 700 700 to to 160 160 m. m. Again, Again, one one ship ship followed followed the the

transect transect from from the the western western side side of of east east to to Stefjord Stefjord Hauk~yfjord Hauk~yfjord with with continuation continuation towards towards

A A second second inter-ship inter-ship calibration calibration exercise exercise was was performed performed in in Tysfjorden Tysfjorden over over an an 8-NM 8-NM

case case like like the the present present one. one.

does does not not periodically periodically log log all all instrument instrument settings settings in in a a file file for for possible possible reference reference use, use, as as in in a a

one one of of the the vessels, vessels, revealing revealing at at the the same same time time a a weakness weakness in in the the acoustic acoustic system, system, which which

600,000 600,000 m /NM The The exercise exercise miscarried, miscarried, however, however, . . from from loss loss of of instrument instrument

settings settings on on

2 2

when when measured measured over over 0.1-NM 0.1-NM intervals, intervals, spanned spanned four four orders orders of of magnitude, magnitude, from from 40 40 to to

range range of of acoustic acoustic fish fish densities, densities, expressed expressed in in units units of of the the area area backscattering backscattering coefficient coefficient

followed followed each each other other with with 1- NM NM separation, separation, exchanging exchanging the the lead lead after after each each transect. transect. The The

half half of of Ofotfjorden, Ofotfjorden, spanning spanning a a depth depth range range from from about about 200 200 to to 500 500 m. m. The The vessels vessels

first first exercise exercise was was performed performed three three times times along along a a 16-NM 16-NM east-west east-west transect transect in in the the eastern eastern

exercises exercises in in which which the the reference reference target target was was the the mid-water mid-water scattering scattering layer layer of of herring. herring. The The

During During the the first first cruise, cruise, the the two two research research vessels vessels performed performed two two inter-ship inter-ship calibration calibration

Inter-ship Inter-ship calibration calibration of of echo echo integrators integrators

migration migration pattern pattern may may also also indicate indicate that that the the migration migration is is an an oxygen-influenced oxygen-influenced migration. migration.

not not observed observed to to stay stay in in water water with with oxygen oxygen below below 1.0 1.0 ml/1. ml/1. The The observed observed variable variable diurnal diurnal

The The herring herring tended tended to to avoid avoid water water with with dissolved dissolved oxygen oxygen less less than than about about 1.5 1.5 ml/1, ml/1, and and was was

occasionally occasionally the the whole whole layer, layer, ascend ascend from from 200 200 m m to to about about 50 50 m m depth depth during during night-time. night-time.

the the fjord. fjord. The The main main biomass biomass is is found found in in the the deeper deeper layer layer (Fig. (Fig. 11), 11), while while parts, parts, or or

at at about about 200 200 m m depth, depth, is is directly directly related related to to the the vertical vertical distribution distribution of of herring herring biomass biomass in in

10). 10). A A typical typical two-layer two-layer minimum minimum in in dissolved dissolved oxygen, oxygen, one one at at 70 70 - 100 100 m m depth depth and and one one

7.0°C 7.0°C and and a a salinity salinity between between 34.0 34.0 and and 34.9 34.9 ppt ppt at at the the depths depths between between 70 70 and and 230 230 m m (Fig. (Fig.

fjord fjord water water occupied occupied by by the the wintering wintering herring herring maintains maintains an an almost almost constant constant temperature temperature of of

et et al. al. (1994). (1994). Similar Similar conditions conditions were were also also observed observed in in November/December November/December 1993. 1993. The The

The The general general topography topography and and hydrography hydrography of of the the fjord fjord system system are are described described by by Dommasnes Dommasnes

2 2

2

= = (0 0 = = 0.830-0.198, 0.830-0.198, = = 126, 126, n n 0.94). 0.94). (CTD) (CTD) X X r

2 2 11 11

and and Rombaken, Rombaken, Bogen, Bogen, excluding excluding but but Herjangsfjord Herjangsfjord including including Ofotfjord Ofotfjord central central 1) 1) ( ( of of

consist consist these these Ofotfjorden, Ofotfjorden, For For variograms. variograms. experimental experimental and and sections sections cross cross backscattering backscattering

average average computing computing of of purpose purpose the the for for coverage, coverage, acoustic acoustic of of degree degree of of basis basis the the on on

mainly mainly regions, regions, geographical geographical limited limited more more into into divided divided been been has has region region the the Consequently, Consequently,

complicated. complicated. geometrically geometrically is is region region survey survey the the 5, 5, and and 1 1 Figs. Figs. to to according according Clearly, Clearly,

Stratification Stratification

database. database. a a in in stored stored and and interpretation, interpretation,

the the to to according according class class scatterer scatterer by by split split echogram, echogram, the the of of regions regions -selected -selected or or delimited delimited

operator­ for for computed computed automatically automatically are are of of Values Values species. species. non-target non-target to to sA sA or or herring, herring,

species, species, target target the the to to registrations registrations assigning assigning of of consists consists alia. alia. Classification Classification inter inter profile, profile,

STD STD and and composition composition catch catch as as data data auxiliary auxiliary such such by by aided aided BEl, BEl, running running workstation workstation

the the of of screen screen electronic electronic the the on on displayed displayed generally generally is is which which echogram, echogram, the the on on appearance appearance

their their of of basis basis the the on on classified classified are are registrations registrations acoustic acoustic specific specific process, process, this this In In

interpretation interpretation Echogram Echogram

ANALYSIS ANALYSIS OF OF METHODS METHODS

measurements. measurements. acoustic acoustic principal principal on on section section the the in in above above

described described calibration, calibration, in in uncertainties uncertainties the the of of light light the the in in viewed viewed be be to to are are measurements measurements

The The determined. determined. be be to to yet yet has has dependence dependence frequency frequency the the as as extinction, extinction, for for compensation compensation at at

attempt attempt without without measurements, measurements, the the from from directly directly derived derived are are values values reported reported The The 2. 2. Table Table

in in performed performed is is 1994 1994 January January in in cruise cruise the the of of survey survey first first the the from from data data of of comparison comparison A A

Korneliussen. Korneliussen. R.J. R.J. to to due due operation operation

entirely successful successful entirely an an cruise, cruise, first first the the during during BEl BEl to to extension extension an an of of adoption adoption and and testing, testing,

development, development, involved involved This This data. data. 38-kHz 38-kHz the the with with together together interpreted interpreted were were 200kHz 200kHz and and

120, 120, 18, 18, at at Data Data processing. processing. further further for for logged logged automatically automatically and and BEl BEl by by received received were were

they they where where (LAN), (LAN), network network local-area local-area the the over over broadcast broadcast were were tranceiver tranceiver each each from from Data Data

frequency. frequency.

transmit transmit respective respective the the of of 10% 10% were were bandwidths bandwidths receiver receiver nominal nominal The The ms. ms. 0.2 0.2 and and 0.3, 0.3, 1, 1,

2, 2, were were durations durations pulse pulse corresponding corresponding The The 200kHz. 200kHz. and and 120, 120, 38, 38, 18, 18, frequencies, frequencies, four four of of

each each at at simultaneously simultaneously made made were were Hjort" Hjort" "Johan "Johan RIV RIV with with measurements measurements mentioned, mentioned, As As

integration integration echo echo Multi-frequency Multi-frequency

92. 92. is is intervals intervals 0.2-NM 0.2-NM of of number number

The The of of y y units units x x with with each each 71, 71, 304 304 = = and and sA' sA' 29459 29459 = = are are values values mean mean The The 1906. 1906. ± ± 1084 1084

= = = = b b and and 0.049 0.049 ± ± a a 0.931 0.931 following: following: the the are are deviations deviations standard standard first first with with coefficients coefficients

the the of of values values the the transects, transects, combined combined the the for for and and kHz kHz 38 38 at at made made measurements measurements For For 12 12

computed computed

for for the the various various strata, strata, and and models models have have been been fitted fitted to to these. these. In In some some cases, cases, the the

et et al. al. 1990, 1990, Petitgas Petitgas 1993). 1993). For For the the present present data, data, experimental experimental variograms variograms have have been been

known known

(Laurec (Laurec and and Perodou Perodou 1987, 1987, Conan Conan et et al. al. 1988, 1988, Petitgas Petitgas and and Poulard Poulard 1989, 1989, Guillard Guillard

Application Application

of of geostatistics geostatistics in in the the analysis analysis of of fish fish abundance abundance survey survey data data is is becoming becoming well well

Geostatistics Geostatistics

function function by by N. N.

characteristics characteristics of of the the region region is is derived derived by by multiplying multiplying the the length length probability probability density density

the the region. region. The The result result is is the the estimated estimated total total number number of of scatterers. scatterers. N N The The length length distribution distribution

The The

cumulative cumulative

abundance abundance figure figure is is derived derived by by multiplying multiplying p p by by the the total total A A surface surface area area of of

where where p p is is the the sought sought A A area area density density of of target target scatterers. scatterers.

= = SA SA pAO pAO , ,

echo echo integration, integration, namely namely

converted converted

to to a a measure measure of of biological biological density density according according to to the the fundamental fundamental equation equation of of

The The

arithmetic arithmetic mean mean of of blocks blocks containing containing measured measured sA-values sA-values is is computed. computed. This This is is

part part of of a a grid grid of of blocks blocks covering covering the the entire entire survey survey region. region.

averaged averaged

over over individual individual blocks, blocks, or or statistical statistical squares, squares, of of side side length length 0.2 0.2 NM. NM. These These are are

GPS, GPS,

and and because because of of

integration integration

over over 0.1-NM 0.1-NM intervals intervals of of sailed sailed distance, distance, values values of of are are sA sA

Because Because

of of uncertainty uncertainty in in the the precise precise positions positions of of data data collection, collection, notwithstanding notwithstanding use use of of

Global Global averaging averaging

system. system. Data Data from from Tjeldsund Tjeldsund are are not not analyzed analyzed here. here.

quantity quantity

of of younger younger herring herring in in the the context context of of the the biomass biomass present present in in the the Ofotfjord- Tysfjord Tysfjord

Tjeldsund Tjeldsund

was was acoustically acoustically surveyed surveyed in in December December 1993, 1993, but but with with finding finding of of a a rather rather small small

west west or or east east

of of the the meridian meridian

at at 17°E. 17°E. The The respective respective areas areas are are 51.2 51.2 and and 40.6 40.6 NM . .

2

cruise, cruise,

the the data data of of central central Ofotfjorden Ofotfjorden must must be be separated separated into into two two parts, parts, as as the the data data lie lie

The The

geographical geographical subdivisions subdivisions are are affected affected only only in in one one way: way: for for the the January January 1994 1994 survey survey

differences differences in in size size distribution distribution and and associated associated dynamics. dynamics.

-values, -values, the the fjords fjords sA sA are are divided divided into into the the regions regions described described in in the the section section on on geographic geographic

Biologically, Biologically,

and and for for purposes purposes of of assignment assignment of of the the average average backscattering backscattering cross cross section section to to

apparently apparently justified justified by by the the encountered encountered distributions distributions of of herring. herring.

( 1 1 ( 0) 0)

northern northern Tysfjord. Tysfjord. The The boundaries boundaries of of these these regions regions are are somewhat somewhat arbitrary, arbitrary, but but are are

KjS!)psviksund, KjS!)psviksund,

(8) (8) eastern eastern HaukS!)yfjord HaukS!)yfjord including including Stefjord, Stefjord, (9) (9) western western HaukS!)yfjord, HaukS!)yfjord, and and

(4) (4) Hellemofjord, Hellemofjord, (5) (5) eastern eastern HullS!)ysund HullS!)ysund and and Mannfjord, Mannfjord, (6) (6) inner inner Tysfjord, Tysfjord, (7) (7)

justifying justifying its its neglect. neglect. Tysfjorden Tysfjorden is is divided divided into into the the following following seven seven regions: regions:

Skjomen, Skjomen,

(2) (2) Rombaken, Rombaken, and and (3) (3) Skjomen. Skjomen. The The occurrence occurrence of of fish fish in in Bogen Bogen was was minimal, minimal, 13 13

conditions. conditions. prevailing prevailing under under least least at at abundance, abundance, of of measures measures reasonable reasonable yielding yielding

of of capable capable seem seem hours hours 12-24 12-24 of of period period a a in in conducted conducted be be can can that that Surveys Surveys days. days. of of period period

a a over over movement movement horizontal horizontal little little be be to to appears appears there there however, however, Often, Often, unpredictable. unpredictable. be be

to to appear appear movements movements horizontal horizontal large large Rather Rather behaviour. behaviour. schooling schooling daytime daytime and and migration migration

vertical vertical diurnal, diurnal, with with associated associated changes changes regular regular ignoring ignoring hours, hours, 12-24 12-24 say say time, time, of of period period

rather short short rather a a over over dramatically dramatically changes changes occasionally occasionally distribution distribution spatial spatial the the that that namely namely

system, system, fjord fjord same same the the in in herring herring of of observations observations earlier earlier confirms confirms cruises cruises reported reported the the

of of observation observation One One vessel. vessel. research research the the of of passage passage the the to to due due effects effects behavioural behavioural other other or or

reactions reactions avoidance avoidance of of presence presence possible possible and and sections, sections, cross cross extinction extinction and and backscattering backscattering

of of values values of of appropriateness appropriateness coverage, coverage, acoustic acoustic of of degree degree stock, stock, the the of of distribution distribution

spatial spatial the the concern concern here here reported reported survey survey of of kind kind the the about about asked asked be be to to questions questions Major Major

assessment. assessment. abundance abundance their their for for prerequisite prerequisite a a 1993), 1993),

(Gunderson (Gunderson surveying surveying acoustic acoustic to to fish fish the the of of availability availability the the for for importantly importantly argues argues but but

validity, validity, their their prove prove not not does does This This consistency. consistency. internal internal strong strong a a show show results results the the Clearly, Clearly,

sources sources Error Error

DISCUSSION DISCUSSION

5. 5. Table Table in in presented presented also also are are mean mean the the of of error error

standard standard and and variance variance estimation estimation The The excluded. excluded. and and included included both both are are transects transects parallel parallel the the

connecting connecting end-links end-links designs, designs, several several the the from from data data the the analyzing analyzing In In 5. 5. Table Table in in compared compared

are are transects, transects, spaced spaced equally equally parallel, parallel, of of system system fine-scale fine-scale subsequent subsequent and and pattern pattern

zigzag zigzag large-scale large-scale initial initial the the with with surveyed surveyed as as Ofotfjord, Ofotfjord, central central for for estimates estimates Abundance Abundance

4. 4. Table Table in in presented presented are are estimate, estimate, abundance abundance

stock stock respective respective the the by by weighted weighted distributions distributions length length individual individual the the combining combining by by formed formed

distributions, distributions, length length composite composite Corresponding Corresponding shown. shown. are are extinction extinction for for compensation compensation

with with and and without without Estimates Estimates cruises. cruises. both both during during followed followed designs designs survey survey zigzag zigzag large-scale large-scale

initial initial the the on on based based are are Estimates Estimates form. form. summary summary in in given given is is system system Tysfjord Tysfjord Ofotfjord-

the the for for abundance abundance total total 3, 3, Table Table In In tables. tables. of of series series short short a a through through presented presented are are These These

RESULTS RESULTS

1993). 1993). (Foote (Foote analyzed analyzed

were were 1992 1992 December December from from data data survey survey acoustic acoustic the the that that manner manner very very the the in in effected effected

been been has has This This computed. computed. be be to to variance variance estimation estimation the the allows allows models models these these of of Use Use

terms. terms. spherical-function spherical-function and and nugget nugget summing summing

by by fitted fitted be be can can which which variograms, variograms, bounded bounded of of cases cases important important are are there there between, between,

In In variogram. variogram. increasing increasing linearly linearly with with scales, scales, all all at at seen seen is is structure structure cases, cases, other other In In NM. NM.

0.2 0.2 namely namely analysis, analysis, of of size size scale scale basic basic the the at at least least at at structure, structure, of of absence absence an an show show data data 14 14

understanding understanding

it, it,

is is necessary necessary for for proper proper stratification stratification in in analyzing analyzing large-scale large-scale survey survey data, data,

replete replete

with with biological biological implications. implications. Describing Describing this this structure, structure, not not to to mention mention

Geographical Geographical

separation separation

or or structuring structuring of of the the stock stock even even within within a a limited limited fjord fjord system system is is

herring, herring, and and North North Sea Sea herring) herring) must must be be solved. solved.

important important

herring herring

stocks stocks (Norwegian (Norwegian spring spring spawning spawning herring, herring, Icelandic Icelandic summer summer spawning spawning

split-beam split-beam

techniques techniques

and and TS-length TS-length relations relations used used in in the the acoustic acoustic biomass biomass estimation estimation of of

The The problem problem

of of the the reported reported discrepancy discrepancy between between in in situ situ TS TS measurements measurements using using

orientation orientation

remains remains a a subject subject of of the the greatest greatest importance importance to to stock stock abundance abundance estimation. estimation.

those those

of of

depth, depth,

depth depth history, history, physiological physiological state state including including fat fat content content (Ona (Ona 1990), 1990), and and

acoustic acoustic

properties properties of of

herring herring in in situ, situ, especially especially to to delineate delineate such such possible possible dependences dependences as as

studies studies

performed performed

concurrently concurrently with with the the surveying surveying measurements. measurements. Thus, Thus, measuring measuring the the

That That

there there

are are outstanding outstanding problems problems is is evident evident from from the the number number and and extent extent of of auxiliary auxiliary

Outstanding Outstanding problems problems

significant significant avoidance avoidance reactions. reactions.

R/V R/V

"Johan "Johan Hjort" Hjort"

in in Table Table 3. 3. Such Such an an agreement agreement argues argues strongly strongly for for the absence absence the of of

extinction extinction

indicates indicates

agreement agreement to to within within about about 10% 10% of of the the corresponding corresponding result result shown shown for for

been been

presented presented here, here,

for for want want of of time, time, a a preliminary preliminary analysis analysis of of data data not not compensated compensated for for

conditions. conditions.

While While

results results from from the the large-scale large-scale survey survey with with RIV RIV "Michael "Michael Sars" Sars" have have not not

remarkable remarkable

by by

the the

apparent apparent specificity specificity of of reactions reactions to to time, time, place, place, and and intangible intangible in in situ situ

not not prevented prevented

results results

obtained obtained at at different different times times from from showing showing a a consistency consistency made made more more

Avoidance Avoidance

reactions reactions

have have not not been been proven proven to to be be absent. absent. If If present, present, however, however, these these have have

with with the the same same variables variables that that influence influence the the backscattering backscattering cross cross section. section.

Determination Determination

of of this this quantity quantity is is intrinsically intrinsically statistical, statistical, but but it it probably probably shares shares dependence dependence

remains remains

to to be be

done. done. The The situation situation is is similar similar with with respect respect to to the the extinction extinction cross cross section. section.

distribution distribution

in in relation relation to to depth, depth, impact impact of of changing changing fat fat content content on on the the target target strength), strength),

are are

outlined outlined

in in the the present present paper paper (in (in situ situ target target strength strength measurements, measurements, tilt tilt angle angle

However, However,

fundamental fundamental

work work on on the the target target strength-length strength-length relation, relation, of of which which some some topics topics

prognosis prognosis

has has been been the the basis basis for for management management of of this this commercially commercially important important stock. stock.

tuning tuning

process process

to to estimate estimate the the stock stock size size as as a a starting starting point point for for a a stock stock prognosis. prognosis. This This

the the ICES ICES

Working Working

Group Group on on Atlanto-Scandic Atlanto-Scandic Herring Herring and and Capelin Capelin (Anon. (Anon. 1994) 1994) in in a a

have, have,

together together

with with

other other estimates estimates of of the the spawning spawning stock stock (from (from tagging), tagging), been been utilized utilized by by

applied. applied.

The The

results results from from previous previous acoustic acoustic surveys surveys in in the the wintering wintering area area (Foote (Foote 1993) 1993)

target target

strength-fish strength-fish

length length relationship relationship for for Norwegian Norwegian spring spring spawning spawning herring herring has has been been

depends depends

entirely entirely

on on the the backscattering backscattering cross cross section section or or target target strength. strength. Here, Here, the the standard standard

Whether Whether

the the stock stock abundance abundance estimates estimates are are to to be be interpreted interpreted as as absolute absolute or or relative relative

measure measure (Anon. (Anon. 1993). 1993).

disregards disregards

this. this.

It It has has been been earlier earlier argued argued that that the the estimation estimation variance variance is is the the more more useful useful

quantity quantity

includes includes

information information on on spatial spatial structure, structure, through through the the variogram, variogram, while while the the second second

corresponding corresponding

values values

for for the the standard standard error error of of the the mean mean shows shows no no regular regular pattern. pattern. The The first first

Ofotfjord Ofotfjord

in in January January 1994, 1994, comparison comparison of of values values of of the the estimation estimation variance variance with with

is is assessed assessed

by by the the estimation estimation variance. variance. In In the the case case of of herring herring as as measured measured in in central central

The The

degree degree

of of acoustic acoustic

coverage coverage relative relative to to the the stock stock distribution distribution and and area area to to be be surveyed surveyed 15 15

pp. pp. 69 69 144. 144. Res., Res., Res. Res. Coop. Coop. ICES ICES

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

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

[Mimeo] [Mimeo] pp. pp. 10 10 1994/(B+D+G+H):2. 1994/(B+D+G+H):2. CM CM ICES ICES

speculations. speculations. and and measurements measurements new new herring: herring: of of section section cross cross Extinction Extinction 1994. 1994. K.G. K.G. Foote, Foote,

[Mimeo] [Mimeo] pp. pp. 12 12 1993/D:45. 1993/D:45.

CM CM ICES ICES fjord. fjord. a a in in hibernating hibernating herring herring of of estimation estimation Abundance Abundance 1993. 1993. K.G. K.G. Foote, Foote,

981-987. 981-987. 82: 82: Am., Am.,

Soc. Soc. acoust. acoust. surveys. surveys. J. J. integrator integrator echo echo in in use use for for strengths strengths target target Fish Fish 1987. 1987. K.G. K.G. Foote, Foote,

63-69. 63-69. 51: 51: Sci., Sci., mar. mar. ICES ICES J. J. areas. areas. wintering wintering

herring herring in in concentrations concentrations oxygen oxygen Reduced Reduced 1994. 1994. I. I. RS?Sttingen, RS?Sttingen, and and F. F. Rey, Rey, A., A., Dommasnes, Dommasnes,

[Mimeo] [Mimeo]

pp. pp. 8 8 1988/D:21. 1988/D:21. CM CM ICES ICES herring. herring. of of school school a a in in distribution distribution spatial spatial of of analyses analyses

Geostatistical Geostatistical 1988. 1988. M. M. Cumeau, Cumeau, and and M. M. Chadwick, Chadwick, E., E., Wade, Wade, U., U., Buerkle, Buerkle, G.Y., G.Y., Conan, Conan,

123-130. 123-130.

11(3): 11(3): lOA, lOA, Proc. Proc. system. system. echo-sounder echo-sounder new new A A 1989. 1989. H. H. Solli, Solli, and and H. H. Nes, Nes, H., H., Bodhold, Bodhold,

1994/Assess:8. 1994/Assess:8. CM CM

ICES ICES Group. Group. Working Working Capelin Capelin and and Herring Herring Atlanto-Scandian Atlanto-Scandian the the of of Report Report 1994. 1994. Anon. Anon.

pp. pp. 87 87 195. 195.

Rep., Rep., Res. Res. Coop. Coop. ICES ICES 1991. 1991. September September 5-9 5-9 Reykjavik, Reykjavik, Data, Data, Survey Survey Acoustic Acoustic to to

Techniques Techniques Statistical Statistical Spatial Spatial of of Applicability Applicability the the on on Workshop Workshop the the of of Report Report 1993. 1993. Anon. Anon.

REFERENCES REFERENCES

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swimbladder swimbladder including including especially especially work, work, laboratory laboratory in in participation participation for for thanked thanked are are Tiarsin, Tiarsin,

M. M. Kinacigil and and Kinacigil T. T. scientists, scientists, guest guest Two Two cruise. cruise. 1993 1993 December December the the during during plotter plotter

new new a a testing testing and and maps maps distribution distribution preparing preparing for for 0stensen 0stensen 0. 0. and and cruise, cruise, 1994 1994 January January

the the during during samples samples biological biological analyzing analyzing for for NS?Sdtvedt NS?Sdtvedt A. A. BEl, BEl, on on work work for for Korneliussen Korneliussen

R.J. R.J. data, data, of of gigabytes gigabytes interpreting interpreting for for Romslo Romslo A. A. and and Hansen Hansen K.A. K.A. thanked: thanked: particularly particularly

are are following following The The help. help. steadfast steadfast their their for for thanked thanked are are cruises cruises the the on on participants participants Fellow Fellow

ACKNOWLEDGEMENT ACKNOWLEDGEMENT

frequencies. frequencies. same same the the at at operate operate that that models models transducer transducer new new with with Hjort" Hjort" "Johan "Johan

RIV RIV board board on on mounted mounted transducers transducers 120-kHz 120-kHz and and 18- current current the the of of replacement replacement clear: clear: is is

solution solution The The eliminated. eliminated. be be must must performance performance transducer transducer inferior inferior to to due due uncertainties uncertainties gross gross

potential, potential, this this realize realize to to Certainly Certainly however. however. developed, developed, be be to to remains remains tool tool The The 1993). 1993). ( ( al. al.

et et Foote Foote in in example, example, for for found, found, is is this this on on Speculation Speculation properties. properties. scattering scattering and and behaviour behaviour

fish fish about about learning learning for for tool tool valuable valuable potentially potentially a a is is integration integration echo echo frequency frequency Multiple-

important. important. similarly similarly is is content, content, oxygen oxygen dissolved dissolved especially especially hydrography, hydrography, with with

herring herring of of distribution distribution spatial spatial of of connection connection the the Understanding Understanding work. work. this this in in attempted attempted as as 16 16

1776-1784. 1776-1784.

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Ware, Ware,

D.M. D.M. and and Tanasichuk, Tanasichuk, R. R. 1989. 1989. Biological Biological basis basis of of maturation maturation and and spawning spawning waves waves

CM CM 1992/H:18. 1992/H:18. 10 10 pp. pp.

R~ttingen, R~ttingen, 1992. 1992. I. I. Recent Recent migration migration routes routes of of Norwegian Norwegian spring spring spawning spawning herring. herring. ICES ICES

herring herring in in the the period period 1985-1992. 1985-1992. ICES ICES CM CM 1993/B:40. 1993/B:40.

Reynisson, Reynisson, P. P. 1993. 1993. In In situ situ target target strength strength measurements measurements of of Icelandic Icelandic summer-spawning summer-spawning

on on hake hake in in the the Bay Bay of of Biscay. Biscay. ICES ICES CM CM 1989/G:62. 1989/G:62. 21 21 pp. pp. [Mimeo] [Mimeo]

Petitgas, Petitgas,

P. P. and and Poulard, Poulard, J.C. J.C. 1989. 1989. Applying Applying stationary stationary geostatistics geostatistics to to fisheries: fisheries: a a study study

application. application. ICES ICES mar. mar. J. J. Sci., Sci., 285-298. 285-298. 50: 50:

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

fish. fish. mar. mar. J. J. biol. biol. Ass. Ass. U.K., U.K., 70: 70: 107-127. 107-127.

Ona, Ona, E. E. 1990. 1990.

Physiological Physiological factors factors causing causing natural natural variations variations in in acoustic acoustic target target strength strength of of

1987/D:9. 1987/D:9. 27 27 pp. pp. [Mimeo] [Mimeo]

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Huse, Huse, 1., 1., Foote, Foote, K.G., K.G., Ona, Ona, E. E. and and R~ttingen, R~ttingen, 1994. 1994. I. I. Angular Angular distribution distribution of of

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D.R. D.R. 1993. 1993. Surveys Surveys of of fisheries fisheries resources. resources. Wiley, Wiley, New New York. York. 248 248 pp. pp.

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strength strength of of mature mature herring. herring. ICES ICES CM CM 1993/B:30. 1993/B:30. 8 8 pp. pp. [Mimeo] [Mimeo]

Foote, Foote,

K.G., K.G., Hansen, Hansen, K.A. K.A. and and Ona, Ona, E. E. 1993. 1993. More More on on the the frequency frequency dependence dependence of of target target

aggregating aggregating fish. fish. acoust. acoust. J. J. Soc. Soc. Am., Am., 91: 91: 1983-1989. 1983-1989.

Foote, Foote,

K.G., K.G., Ona, Ona, E. E. and and Toresen, Toresen, R. R. 1992b. 1992b. Determining Determining the the extinction extinction cross cross section section of of

strength strength of of mature mature herring. herring. ICES ICES CM CM 1992/B:10. 1992/B:10. 8 8 pp. pp. [Mimeo] [Mimeo]

Foote, Foote, K.G., K.G., Hansen, Hansen, K.A. K.A. and and Ona, Ona, E. E. 1992a. 1992a. On On the the frequency frequency dependence dependence of of target target

Postprocessing Postprocessing system system for for echo echo sounder sounder data. data. acoust. acoust. J. J. Soc. Soc. Am., Am., 90: 90: 37-47. 37-47.

Foote, Foote, K.G., K.G., Knudsen, Knudsen,

H.P., H.P., Korneliussen, Korneliussen, R.J., R.J., P.E. P.E. Nordb~, Nordb~, and and K. K. R~ang, R~ang, 1991. 1991. 17 17

5.2 5.2 -43.9 -43.9 25.20 25.20 K K Skjomen Skjomen 1994 1994 January January

7.7 7.7 -42.1 -42.1 30.89 30.89 J J 17°E 17°E of of E E Ofotfjorden Ofotfjorden 1994 1994 January January

9.4 9.4

-41.3 -41.3 34.03 34.03 I I 17°E 17°E of of W W Ofotfjorden Ofotfjorden 1994 1994 January January

6.7 6.7 -42.7 -42.7 28.80 28.80 H H Stefjord Stefjord 1994 1994 January January

6.6 6.6 -42.8 -42.8 28.50 28.50 G G Tysfjord Tysfjord Inner Inner 1994 1994 January January

10.0 10.0 -41.0 -41.0 35.15 35.15 F F Tysfjord Tysfjord 1994 1994 January January

5.2 5.2 -43.9 -43.9 25.20 25.20 E E Skjomen Skjomen 1993 1993 December December

9.5 9.5 -41.2 -41.2 34.16 34.16 0 0 Ofoten Ofoten 1993 1993 December December

6.3 6.3

-43.0 -43.0 27.80 27.80 c c Tjeldsund Tjeldsund 1993 1993 December December

8.1 8.1 -41.9 -41.9 31.63 31.63 B B Tysfjord Tysfjord Inner Inner Stefjord, Stefjord, 1993 1993 December December

10.1 10.1 -41.0 -41.0 35.23 35.23 A A Tysfjord Tysfjord 1993 1993 December December

TS(dB) TS(dB) !(cm) !(cm) region region Fjord Fjord Stratum Stratum Eeriod Eeriod ) ) (cm (cm Cruise Cruise ab ab

2 2

centimeters. centimeters. in in expressed expressed is is where where ! !

71.9, 71.9,

-

2 2 log log

TS=20 TS=20 equation equation the the from from derived derived are are strength strength target target and and 2 2 length length

root-mean-square root-mean-square The The differentiated. differentiated. is is ab ab section section cross cross backscattering backscattering

mean mean the the which which in in Tysfjorden Tysfjorden and and Ofotfjorden Ofotfjorden of of state state 1. 1. Biological Biological Table Table

(5.9) (5.9) (6. (6. 2) 2) ( ( 4. 4. 1) 1) (3.7) (3.7)

Skjomen Skjomen 9.5 9.5 25.2 25.2 110 110 14.3 14.3 13.3 13.3 10.1 10.1 9.0 9.0

(4.3) (4.3) (3.3) (3.3) (2.6) (2.6) (2.0) (2.0)

Rombaken Rombaken 5.2 5.2 30.9 30.9 58* 58* 0.19 0.19 0.19 0.19 0.15 0.15 0.18 0.18

E E of of 17°E 17°E (2.0) (2.0) (2.1) (2.1) (2.3) (2.3) (2.1) (2.1)

Central Central Ofotfjorden Ofotfjorden 40.6 40.6 30.9 30.9 237* 237* 73.1 73.1 63.2 63.2 51.6 51.6 56.7 56.7

W W of of 17°E 17°E (1.4) (1.4) (1.4) (1.4) (1.5) (1.4) (1.4) (1.5)

Central Central Ofotfjorden Ofotfjorden 51.2 51.2 34.0 34.0 310 310 89.6 89.6 76.1 76.1 49.4 49.4 89.5 89.5

Stratum Stratum

~(cm) ~(cm)

s s

(NM2) (NM2)

18 18 n n 38 38 120 120 200 200

~,, ~,, Area

sA(1000m sA(1000m /NM) /NM) & & (cv) (cv) vs. vs. f(kHz) f(kHz)

2 2 2 2

i~ i~ expressed expressed in in parentheses parentheses below below the the mean mean value value of of sA. sA.

n n to to 235 235 and and 34 34 at at the the respective respective locations. locations. The The coefficient coefficient of of variation variation cv cv

absence absence of of data data at at 120 120 kHz kHz from from a a 5-NM 5-NM interval interval of of integration, integration, which which reduced reduced

which which there there me~sured me~sured are are values values of of sA. sA. The The asterisks asterisks call call attention attention to to the the

fish fish length, length, and and n n the the number number of of statistical statistical squares squares of of side side length length 0.2 0.2 NM NM in in

geographical geographical

and and biological biological strata. strata. The The quantity quantity denotes denotes the the ~ ~ root-mean-square root-mean-square

at at each each of of four four frequencies frequencies during during the the January January 1994 1994 cruise, cruise, selected selected from from four four

2. 2. Table Table Mean Mean values values of of sA sA uncompensated uncompensated for for extinction extinction as as measured measured simultaneously simultaneously

10 14.6 14.6 10 10.2 10.2 1994 1994 January January

9 9 9 9

10 13.2 13.2 10 9.5 9.5 1993 1993 December December

9 9 9 9

comE.ensation comE.ensation compensation compensation period period Cruise Cruise

With With Without Without

extinction. extinction. acoustic acoustic

for for compensation compensation with with and and without without both both performed performed are are Computations Computations fish. fish.

of of numbers numbers total total as as expressed expressed surveys, surveys, zigzag zigzag large-scale large-scale the the from from derived derived

system, system, Ofotfjord-Tysfjord Ofotfjord-Tysfjord the the in in herring herring for for figures figures Abundance Abundance 3. 3. Table Table

-

39.75 39.75

0.00 0.00

0.00 0.00

0.03 0.03 0.03 0.03

39.25 39.25

0.00 0.00

0.00 0.00

0.09 0.09 0.10 0.10

38.75 38.75

0.00 0.00

0.00 0.00

0.65 0.65 0.72 0.72

38.25 38.25 0.29 0.29

0.29 0.29

0.83 0.83 0.93 0.93

37.75 37.75

1.05 1.05

1.09 1.09

2.30 2.30 2.48 2.48

37.25 37.25

4.40 4.40

4.55 4.55

4.17 4.17 4.47 4.47

36.75 36.75

6.81 6.81

7.13 7.13

5.85 5.85 6.31 6.31

36.25 36.25

9.83 9.83

10.39 10.39

6.28 6.28 6.67 6.67

35.75 35.75

8.23 8.23

8.81 8.81

4.97 4.97 5.24 5.24

35.25 35.25

9.88 9.88

10.44 10.44

2.73 2.73 2.87 2.87

34.75 34.75

4.57 4.57

4.80 4.80

2.37 2.37 2.55 2.55

34.25 34.25

3.41 3.41

3.55 3.55

2.53 2.53 2.65 2.65

33.75 33.75

2.43 2.43 2.50 2.50

3.09 3.09 2.95 2.95

33.25 33.25 5.64 5.64

5.80 5.80

3.99 3.99 3.88 3.88

32.75 32.75 4.56 4.56

4.74 4.74

4.88 4.88 4.82 4.82

32.25 32.25 4.81 4.81

4.86 4.86

6.10 6.10 6.07 6.07

31.75 31.75 2.47 2.47

2.50 2.50

4.32 4.32 4.43 4.43

31.25 31.25 4.30 4.30

4.41 4.41

4.73 4.73 4.83 4.83

30.75 30.75 1.51 1.51

1.53 1.53

4.03 4.03 3.81 3.81

30.25 30.25 1.08 1.08

1.07 1.07

3.69 3.69 3.85 3.85

29.75 29.75 1.34 1.34

1.30 1.30

3.01 3.01 2.84 2.84

29.25 29.25 0.69 0.69

0.69 0.69

2.92 2.92 2.76 2.76

28.75 28.75 0.80 0.80

0.71 0.71

2.36 2.36 2.23 2.23

28.25 28.25 1:77 1:77

1.70 1.70

4.02 4.02 3.84 3.84

27.75 27.75 1.09 1.09

1.02 1.02

3.30 3.30 3.19 3.19

27.25 27.25 2.71 2.71

2.41 2.41

4.25 4.25 4.12 4.12

26.75 26.75 2.57 2.57

2.16 2.16

3.24 3.24 3.08 3.08

26.25 26.25 2.71 2.71

2.31 2.31

2.11 2.11 2.02 2.02

25.75 25.75 1.61 1.61

1.33 1.33

1.26 1.26 1.14 1.14

25.25 25.25 0.66 0.66

0.57 0.57

0.45 0.45 0.43 0.43

24.75 24.75 0.20 0.20

0.17 0.17

0.29 0.29 0.27 0.27

24.25 24.25 0.66 0.66

0.54 0.54

0.40 0.40 0.37 0.37

23.75 23.75

1.47 1.47 1.19 1.19

1.02 1.02 0.90 0.90

23.25 23.25 1.01 1.01

0.86 0.86

1.09 1.09 0.99 0.99

22.75 22.75 2.38 2.38

2.00 2.00

1.17 1.17 0.96 0.96

22.25 22.25 1.01 1.01

0.87 0.87

0.58 0.58 0.50 0.50

21.75 21.75 1.01 1.01

0.86 0.86

0.24 0.24 0.19 0.19

21.25 21.25 0.20 0.20 0.17 0.17

0.06 0.06 0.06 0.06

20.75 20.75 0.50 0.50 0.41 0.41

0.31 0.31 0.36 0.36

20.25 20.25 0.00 0.00 0.00 0.00

0.05 0.05 0.06 0.06

19.75 19.75 0.05 0.05 0.04 0.04

0.05 0.05 0.06 0.06

19.25 19.25 0.31 0.31 0.25 0.25

0.05 0.05 0.07 0.07

(cm) (cm) Without Without With With Without Without With With

Length Length December December 1993 1993 January January 1994 1994

with with compensation compensation for for extinction. extinction.

expressed expressed

as as percentage. percentage.

The The weighting weighting functions functions are are computed computed both both without without and and

individual individual

biologicaL biologicaL strata strata by by the the estimated estimated abundance abundance in in each each stratum, stratum,

Ofotfjord-Tysfjord Ofotfjord-Tysfjord

system, system, obtained obtained by by weighting weighting length length distributions distributions for for

Table Table

4. 4. Probability Probability density density functions functions of of length length for for herring herring over over the the entire entire

16.0 16.0 15.2 15.2 10 10 1.83 1.83 13.3 13.3 13.3 13.3 10 10 1.42 1.42 ends ends w/o w/o Parallel Parallel 17°E 17°E of of E E

109 109 1.71 1.71

14.7 14.7

10.8 10.8 109 109 1.35 1.35 12.1 12.1 10.1 10.1 w/ends w/ends Parallel Parallel 17°E 17°E of of E E

109 109

5.62 5.62

20.0 20.0

29.4 29.4 109 109 3.32 3.32 13.8 13.8 22.7 22.7

Zigzag Zigzag

17°E 17°E of of E E 9 9 9 9

8.9 8.9

11.8 11.8 10 10 7.59 7.59 6.2 6.2 7.4 7.4 10 10 5.50 5.50 ends ends w/o w/o Parallel Parallel 17°E 17°E of of W W

109 109 7.31 7.31 7.9 7.9

9.6 9.6 109 109 5.8 5.8 5.30 5.30 6.8 6.8 w/end w/end Parallel Parallel 17°E 17°E of of W W

109 109 5.54 5.54

12.9 12.9

14.4 14.4 109 109 4.14 4.14 8.1 8.1 10.2 10.2

Zigzag Zigzag

17°E 17°E of of W W 9 9 9 9

se se

N N se se N N design design Surve~ Surve~ crE crE Stratum Stratum crE crE

comEensation comEensation With With compensation compensation Without Without

mean. mean. the the of of percentages percentages as as expressed expressed are are

se, se, mean, mean, the the of of error error standard standard and and crE crE variance variance estimation estimation The The extinction. extinction.

for for compensation compensation with with and and without without both both given given are are N N Numbers Numbers 1994. 1994. January January

9-10 9-10 on on separation separation 0.5-NM 0.5-NM with with transects transects spaced spaced equally equally parallel, parallel, of of system system

a a by by and and 1994 1994 January January 7 7 on on design design zigzag zigzag large-scale large-scale the the by by Ofotfjorden Ofotfjorden

central central in in surveyed surveyed herring herring of of estimates estimates abundance abundance of of Comparison Comparison 5. 5. Table Table

Ofotfjorden, Ofotfjorden, Fig. Fig.

1 1

Tysfjorden Tysfjorden

and and adjoining adjoining areas. areas.

1 1 4° 4°

15° 15°

1 6 6 1 ° °

17° 17° 18° 18°

/. /.

)' )'

t t

68° 68°

( ( ......

( (

/ / ;

i i

30' 30' 68° 68°

1993. 1993. - 11.12 11.12 and and 1.10 1.10 Tysfjorden, Tysfjorden,

of of

outlet outlet the the at at

herring herring of of 2b 2b Fig. Fig. distributions distributions Length Length

Lcngdc(cm) Lcngdc(cm)

Alder(i1r) Alder(i1r)

Lcngdc(cm) Lcngdc(cm)

34 34

32 32 :w :w 30 30

26 26 21 21

22 22

20 20

u u 10 10 0 0 4 4 ao ao :JU :JU :JG :JG :J4 :J4 :J2 :J2

0 0 0 0

V V

10 10

20 20 -

10 10

L L

t t ~ ~

ao ao

n n

n n

c c

c c

c c

40 40

s s

5 5

5 5

20 20

0 0

0 0

50 50

0 0

I" I"

r r

r r

p p P P GO GO

p p

ao ao 70 70

uo uo

20 20

!JO !JO ~0 ~0

11.12.93 11.12.93

11.10.93 11.10.93

1993. 1993. -

9.9 9.9 E), E), 14° 14° (approximately (approximately Vestfjorden Vestfjorden

areas. areas. wintering wintering the the to to immigration immigration the the of of

front front

the the at at

herring herring of of

distribution distribution

age age and and Length Length

2a 2a Fig. Fig.

Aldc1'(i11·) Aldc1'(i11·) l.cngrlc(cm) l.cngrlc(cm)

11 11 10 10

4 4

' ' ;: ;:

0 0 :10 :10 :.:n :.:n .(0 .(0 Jr. Jr. :12 :12 :14 :14 :tO :tO L_,_.~- 20 ...... ~~ ~~

11- l 10 10

·20 ·20

1\ 1\

10 10

l l

l l

n n

n n

c c

c c

s s

:so :so

s s

.. .. :!0 :!0

0 0

0 0

r r

r r

40 40

p p p p

ao ao

::.o ::.o • •

(j(l (j(l ~0 ~0 fJ.9.fJ3 fJ.9.fJ3

January January 1994. 1994.

tributaries tributaries of of Tysfjorden Tysfjorden

in in

December December 1993 1993 and and

Fig. Fig. 2c 2c

Length Length distributions distributions of of herring herring in in different different

Lcngdc(cm) Lcngdc(cm) Lcngdc(cm) Lcngdc(cm)

lU lU

20 20

A!~ A!~

24 24

211 211

211 211

:JO :JO

a-! a-! :12 :12

ao ao an an 111 111 20 20 22 22 20 20 21 21 20 20 an an 34 34 32 32 :10 :10 :Ill :Ill 40 40

0-

0-

l l

L L

10 10

n n n n 10 10

c c

c c

s s

s s

0 0

0 0

r r

r r

p p 20 20

p p 20 20

30 30 :10 :10

9.1.91. 9.1.91. 8.1.94 8.1.94

Stcfj Stcfj Tysfj/Hcllcmofj Tysfj/Hcllcmofj

-----· -----·

Lcngde{cm) Lcngde{cm) Alder{ar) Alder{ar)

20 20 22 22 24 24 20 20 20 20 30 30 ::12 ::12 34 34 :JO :JO 4 4 3D 3D 2 2 n n lO lO 0 0

10 10

t t t t

n n n n

c c c c

s s

10 10 s s 20 20

0 0 0 0

r r r r

p p p p

30 30

20~------~ 20~------~ 40 40

6.12.93 6.12.93 Tysfj/Indrc Tysfj/Indrc

1994. 1994.

January January

16 16

-

11 11

period period

the the

in in

Ofotfjorden Ofotfjorden

of of

part part

inner inner

and and

right) right)

(upper (upper

middle middle

left), left),

(upper (upper

outer outer

the the

from from

herring herring of of 3a 3a Fig. Fig.

distributions distributions Length Length

Alcler(;ir) Alcler(;ir)

10 10 0 0

0 0 4 4 :Z :Z

JO JO 30 30

0 0 rrr-r-rr-

JO JO

l l

l l

n n

10 10 n n c c 20 20

c c s s

s s

0 0

0 0 r r -30 -30

r r

p p

p p 20 20

40 40

DO DO

30 30

16.1.94-

Ofotfjordcn/Narvik Ofotfjordcn/Narvik

Alclcr(ar) Alclcr(ar)

Lcngclc(cm) Lcngclc(cm)

Alclc•·(ar) Alclc•·(ar)

12 12 Lcngclc(cm) Lcngclc(cm)

. . 10 10

0 0

0 0

:z :z

4 4

:JO :JO

:JO :JO

34 34

:J:Z :J:Z

:10 :10

20 20

20 20

24 24

:ZZ :ZZ

:tO :tO

0 0

I I

12+ 12+

10 10

0 0

0 0

.. ..

2 2

-10 -10 I·""."' I·""."'

an an I I I I ao ao

1\ 1\ a-1 a-1 I I I I a:z a:z

30 30

:zn :zn :za :za 2-1 2-1 22 22 :zo :zo .,-J-rr-filllliilli .,-J-rr-filllliilli

0 0 ,-,-,-,-,,..r-;-

10 10

10 10 l l

l l

n n

. l l .

l l

n n

n n c c

n n

c c

c c s s

c c 20 20

s s

s s 20 20

0 0

JO JO

S S 0 0

0 0 r r

0 0

r r

r r

p p r r

p p

p p

30 30 p p

30 30

40 40

40 40

20~------r 20~------r

20 20

11.1.9'1-

11.1.f:H 11.1.f:H

Ofotfjordcn/Liland Ofotfjordcn/Liland

nJy nJy a a D D n/ n/ d c c d or or j j o o tf tf f f 0 0

December December 1993, 1993, 10 10 and and 16 16 January January 1994. 1994.

inner inner part part of of the the wintering wintering area area (at (at Narvik) Narvik) from from 1 1

Fig. Fig. 3b 3b Changes Changes

in in length length distribution distribution of of herring herring ·from ·from the the

Lengdc(cm} Lengdc(cm} Aldcr(ar} Aldcr(ar}

o o

z• z• 1 1 :Jo :Jo 20 20 :J:.: :J:.: 22 22

ao ao

20 20 an an

20 20 :H :H

z z 4 4 0 0 0 0 10 10

I I

,_ ,_ 10 10

t t

t. t.

n n 10 10

n n

. . 20 20 c c c c

s s

s s

0 0

0 0

r r

r r :10 :10

p p

20 20

p p

40 40

30 30 50 50

16.1.94· 16.1.94·

Lcngde(cm) Lcngde(cm) Alder(ar} Alder(ar}

Lcngdc(cm} Lcngdc(cm}

ao ao 20 20 az az 22 22

ao ao 20 20 ao ao 20 20 z~ z~ a~ a~ o o 2 2 G G ~ ~ 10 10

10 10 20 20 22 22 24 24 I I 26 26 20 20 JO JO 32 32 34 34 JG JG :JO :JO

10 10

l l

t t

n n L L 10 10 • •

n n

n n

20 20

c c c c

c c

s s s s

s s

0 0

0 0

0 0

r r :JO :JO r r

r r

p p

20 20

p p

p p

40 40

20~------30~------r 30~------r 50 50

1.12.93 1.12.93 1 1 0.1.94· 0.1.94· Narvik;Sk. Vestfjorden Bar121y JOmen

100 j I ) Night I ==J , E 2oo ~ t t l 1' ) Day ..c I ~~-=j I 6. 300 Q) ··o 400

f...., ~...... 500 I ~ A

Vestfjorden Bar121y Narv i k; s kj omen

1 00 Night ...... E 200 ..c. 4-l Day

Q)0. 300 0 400 -

· :SOD B

Vestfjorden Bare;y Na rv i k1 s kj omen

Night 100 __ ..._ ____.t t _ ...... Day E I_---- __ j 200 ..c. 4-l 0. 300 < -.v If' Q) 0 c 400

500 c

c-=-=-=-J Young and immature herring Adult herr~ng

Fig. 4 Schematic presentation of immigration and emigration in relation to the wintering area. See text for explanation.

/, /,

Ofotfjorden Ofotfjorden and and Tysfjorden Tysfjorden in in tracks tracks Fig. Fig. 5 5 Survey Survey

~§::.·---"~~~= ~§::.·---"~~~=

I-- I--

1 1 ...... -

------

=:.=.:::::-- ~ ~ -----

--

__ __ ......

TYSfJC)ftD[H TYSfJC)ftD[H Of'OTr Of'OTr ..oiiiXH ..oiiiXH 01 01

no:cu no:cu :D:l.I"Y :D:l.I"Y lU':7 lU':7

...... _ _

denote denote different different strata strata (Table (Table 1) 1)

Commercial Commercial catch catch (purse (purse seine) seine) . . Encircled Encircled letters letters

December December 1993. 1993. F= F= Reseach Reseach vessel vessel (trawl), (trawl), K= K=

spawning spawning herring herring in in the the wintering wintering areas, areas, October­

Location Location

of of biological biological samples samples of of Norwegian Norwegian Fig. Fig. spring spring 6a 6a

16°00' 16°00' 17°00' 17°00'

6lo' 6lo'

TYSFJORD TYSFJORD 68~0' 68~0' _68°30'

\D

TYSFJORD

68°0 I .,,

16°00' 17"o0'

Fig. 6b Location of biological samples of Norwegian spring spawning herring in the wintering areas, January 1994. F=Research vessel (trawl), K=Commercial catch (purse seine) . Encirled letters denote different strata (Table 1).

situation. situation.

Night-time Night-time

area. area.

wintering wintering

the the in in

herring herring of of

distribution distribution

angle angle Tilt Tilt

7b 7b Fig. Fig.

-90° -90°

5 5

oo oo N=1484 N=1484

90° 90°

situation. situation.

Daytime Daytime

area. area.

wintering wintering

the the in in

herring herring of of

distribution distribution

angle angle

Tilt Tilt 7a 7a Fig. Fig.

-90° -90°

~30 ~30

oo oo N=800 N=800 90° 90°

1.2-1994. 1.2-1994. to to 1.9-1993 1.9-1993 period period the the in in area area wintering wintering

the the in in herring herring of of content content fat fat in in 8 8 Fig. Fig. Variation Variation

1.2.94 1.2.94 94 94 1.1. 1.1. 93 93 1.12. 1.12. 93 93 1.11. 1.11. 93 93 1.10. 1.10. 93 93 1.9. 1.9.

~----~--~--~~h ~----~--~--~~h

5 5

10 10 Q Q

t_ t_

a a

V) V)

Cl.J Cl.J

c:: c:: ~ ~

~ ~

15 15

~ ~

20 20 25 25 68°30'N

68°

16° 17° 18°

Fig. 9 Hydrographical stations worked from R/V "Michael Sars" during the November/December 1993 survey.

conditions. conditions. oxygen oxygen and and salinity salinity temperature, temperature,

10 10 Fig. Fig. showing showing Ofotfjorden Ofotfjorden entire entire the the along along Section Section

500 500

,1:00 ,1:00

300 300 ~ ~

~ ~

p.. p..

E-< E-< ::r: ::r:

5 5

200 200 -. -.

100 100

0 0

~ ~

~ ~

p.. p..

E-< E-<

::r: ::r:

~ ~

~ ~

p.. p..

E-< E-<

::r: ::r:

.•. .•. 1160 1160 0

100

z ·200

I I­ Q_w 0 300

·400

·500 0 2 4 6 8 10 OXYGEN

Fig. 11 Echo recordings of two herring layers, with corresponding oxygen profile.