CM_1977_F_23.pdf (579.9Kb)

~. \.(/ T

^OJ

^vt;'.'.

1I.)1lt(!ltA,C;·vr,e-1t-'K1'tOVr,,;; ^.,.~.

^.'

^{Ir_ .}

~l..iA,o~t This p ape ^l' not to be c ^J. t~ad wi t.ho' ~ _E ^l' io ^r rafe renc~to ITlhe au that;,:;, International Council for

the Exploration of the Sea

,-- C.M. 1977/F:23

Demersal fish (N) Committee

INVESTIGATIONS ON DEMERSAL FISH IN THE 8ARENTS SEA IN WINTER 1977.

by

John Dalen, Arvid Hylen and Odd M. Smedstad Institute of Marine.Research, 8ergen

INTRODUCTION

The investigation during the winter 1977 shall be regarded as a continuation of a project initiated in 1970. The aim of the first part of the project was to find the most suitable time of the year to carry out acoustic surveys on demersal fish in the Ba~ents Sea (HYLEN et al. 1972, HYLEN, GJ0S~THER og SMEDSTAD 1972 and HYLEN ~nd

SMEDSTAD 1972). January - February was found to be the most suitable time for such investigations in the sentral and eastern parts of the 8arents Sea (JAK08SEN 09 NAKKEN 1973, MONSTAD og MIDTTUN 1973, ANON 1974 and ANON 1975a). From 1974 the aim of the acoustic investLga.

tions gradually changed to assess absolute abundance of recruits of north-east arctic cod and haddock. The most extensive investigations were carried out in 1977.

MATERIAL AND METHODS

The investigation was carried out from 10 January to 4 February 1977 by R.V. "G.O.Sars" and R.V "Johan Hjort". Survey tracks, stat.ions and the boarder between the eastern and western part of the survey area are shown in Figs. 1 and 2.

An acoustic intercalibration was carried out north of Nordkyn. Un~

fortunately, the quality of thiS calibration was too low for any use.

ThiS, together with a break-down on the bottom trawl winches onboard

- 2 ~.

R.V. "Johan Hjort" made it impossible to assess any absolute abundance of demersal fish west of Nordkyn. The area surveyed by R.V. "G.O.Sars"

cover approximately the same area as in 1974 - 1976.

Echo intensity was observed by a Simrad EK 38 kHz echosounder 8nd

three analog echo integrators (SIMRAD QM). Average integrator reading from each depth channel was recorded at each 5th nautical mile. When more than one species were observed in the same depth interval, the integrator values were distributed on the" species by judging the echo recordings and/or according to the fr~gu~8cies of the species caught on the nearest trawl stations.

The survey area was divided into squares

(3D'

in the north-south direction and 1⁰ in the east-west direction). Echo abundance was calculated for each square, and each square was given a length distri- bution obtained from the nearest trawl stations. For each species the number of speCimens within the different length groups were estimated for"each square by a method described by NAKKEN and DOMMASNES (1975) and extended by DALEN (1975). The abundance of each year class is then estimated by age-length keys obtained during the survey.

RESULTS AND DISCUSSIONS

~l~~e~E§ebl_~Q~_r!~b_~~~~E~~~~~~Q

The relation between the abundance of cod and haddock and the tempera- ture conditions in the deeper water layers is shown in Figs. 3 - 5.

Cod and haddock were mainly distributed in water warmer than 1⁰C. This temperature condition was found west of 3S^oE and in a narrow belt over the Skolpen Bank towards Novaya Zemlja.

COD

Geographical distribution

---

Figs. 6 - 9 shoUl the distribution of the year classes 1976, 1975, 1974 and the 1973 and older respectively. Both the 1976 and 1975 year

- 3 -

class were most abundant in the eastern part of the survey area, while the 1974 year class and the older ones had a more western distribu- tion. However, the distribution of the 1975 year class in 1977 indi- cates that this year class has moved westward after February 1976

(DALEN, HYLEN og SMEDSTAD 1977).

The geographical distributions of the 1975 and 1976 year class were different as 1 year old fish. In 1976 about 93% by numbers of the 1975 year class was recorded in the eastern part of the survey area, while in 1977 about 66% of the 1976 year class was distributed in the eastern part (Table 1). The eastern 'diitribution of the 1975 year class was also recorded during the O-group investigation, and at that time it was supposed that this distribution was due to a considerably greater than average inflow of the Norwegian Current water into the Barents Sea (ANON 1975b).

1 - 3 year old cod has been expected to be more or less stationary.

However, the results from the 1977 investigations (Table 1) indicate that young cod already from their first year^c of life start to move westwards from the eastern part of their area of distribution. These indications confirm the 1976 findings. In general the distribution of three year old cod and older depends on the distribution of the capelin which in January - February undertakes a spawning migration towards the coast.

~~~~~_s~~e~~~~!~~

Good agreement is observed between the relative year class strength in the immature part of the stock in 1976 and 1977 (Table 1 and Fig.

10). These correspond fairly well to those expected from the O-group surveys (ANON 1976).

An increased abundance by numbers have been observed for the year classes 1971 - 1973 by age (Fig. 10). This might be an effect of ao

insufficient biological sampling in the years 1974 and 1975. Any mar·

- 4 -

tality estilQation can therefore only be made for the year classes 1971 - 1973 on the basis of the 1976/1977 survey data (Table 2). The morta- lities estimated for the year classes 1969 - 1970 on the data from

the cruises in 1974 - 1976 might also have been effected by insufficient sampling.

In Table 2 are given the total mortality coefficients Z(AM), calculated from the acoustic data and Z(VPA) estimated from the method of Virtual Population Analysis where the natural mortality coefficient is assumed equal to 0.20 (ANON 1977).

For the year classes 1969 and 1970 the Z(AM) which are estimated on the basis of the 1976/1977 survey data, are higher than the correspond- ing Z(VPA). This is partly due to maturation of these year classes which in the beginning of the year are on their way to the spawning grounds outside the survey area.

For all year classes, except the 1974 year class, there is observed a reduction in numbers from 1976 to 1977. However, the 1974 year class and earlier poor year classes have been ,difficult to measure by acoustic methods. Bias in the estimated numbers of poor year classes is at

least to some ext~nt caused by insufficient biological sampling (DALEN, HYLEN og SMEDSTAD 1977).

The total mortality Z(AM) of the year classes 1971 - 1972 are higher than the respective mortalities assumed to initiate the Virtual Popu- lation Analysis Z(VPA), while the respective mortality for the 1973 year class is much lower. However, one shall not pay too great attention to these differences, because the Z(VPA) for 1976 are assumed figures.

Even with correct fishing mortality coefficient to initiate VPA, differ- ences might be caused by the fact that Z(AM) only refers to the Barents Sea component of the stock. On the other hand yearly variations in

the ratio of fish which are close to the bottom during the survey, would also effect the

Z(AM).

To try to overcome some of the problems

acoustic surveys with the aim of estimating the absolute abundance of the recruits shall thorefore be undertaken at the same time of the year.

- 5 -

HADDOCK

Geographical distribution

---~---~--~---

Figs. 11 and 12 show the distribution of 1 year old fish and older ones respectively. Both area of distribution and abundance were found to be greater in 1977 than in 1976. Mainly 1 - 4 year old fish were observed in the eastern area, while the western area had a greater component of older fish (Table 3).

§~9~~_~9~e2~!!!2~

The 1975 year class was the most abundant year class in 1977 (Fig. 13), It made up 5B.6% by number, while the 1976 and 1974 made up 19.2% and 14.8% respectively (Table 3). The 1975 year class was reduced by

number from 1976 to 1977, while the abundance of the other year classes apparently increased in number. This was possibly caused by insuffi- cient sampling of haddock in 1976, which involved a great overestima- tion of the 1975 year class and a corresponding underestimation of the other year classes (DALEN, HYLEN og SMEDSTAD 1977). The estimated relative year class strength based on the 1977 survey, corresponds with that expected from the O-group surveys (ANON 1976). A more exten- sive biological sampling of the fish might be responsible for the ob- served improvement in the abundance estimates.

REDFISH

Fig. 14 shows the echo abundance of redfish. This species had a more western distribution than cod and haddock. Mostly small redfish is observed in the eastern part of the distribution.

\

\

.• 6 -

REFERENCES

ANON 1974. Gyteinnsiget av lodde vinteren 1974. ~he spawning migra- tion of capelin the winter of 1974. ] Fiskets Gang, 60: 713w 718.

ANON 1975a. Unders0kelser pA lodde og torsk i Barentshavet vinteren 1975. [Investigations on capelin and cod in the Barents 50a

during the winter of 1975.] Fis'kets Ga~.9., 62: 69-73.

ANON 1975b. Preliminary report of the international O-group fish survey in the Barents Sea and adjacent waters in August - September 1975. f..?~n D Meet.~ int. CDun. ExplDE,. S~;~1.212

(H:48): 1-5, [Mimeo.] .

ANON 1976. Preliminary report of the international O-group fish survey in the Barents Sea and adjacent waters in August - September 1976. eaun. Meet. into Count Explor. ~ea, )976 (H:43) 1-5, [MimeoJ

ANON 1977. Report of the North-East Arctic Fisheries Working Group, Charlottenlund, 14 - 18 March 1977. eoun. Meet. int.~C9.u.n.

Ex'p 1 a r. Sea, 1 977 (F: 6) 1 - 30 , [rh m ea.]

DALEN, J. 1975. Programbeskrivelser for datamaskinprogrammer for fordeling og statistisk behandling av karakteristiske st0r~­

eIser hos fisk. Fore.l0pig rapl2-0_;:t~. Fiske~E...!..-Havf ..,;.insL , Bergen.: 1-8. [Mimeo,]

DALEN, J., HYLEN, A. og SMEDSTAD, O.M. '1977. Akustisk mengdcmaling av torsk og hyse i Barentshavet i februar 1976. [Aco~3tic

abundance estimation of cod and haddock in the Barents Sea in February 1976.J risken Hav..!.L_1977. [In print.]

- 7 -

H Y L EN, A., J A K 0 B S EN, T., L A H N - J 0 H ANN E S S EN, J., S i"1 E D S TA D, O. M. 0 9

S~TRE, R. 1972. 8unnfiskundersokelsel' ved Bj0rnoya, Spits- bergen og i Barentshavet med FIF "G.O.Sars" 3. - 20. november 1970. [Demersal fish investigations in the waters off Bear Island, Spitsbergen and in the Barents Sea with R.V. "G.O.Sarsll 3 - 20 November 1970.J Fiskets Gan~, 58: 189-202.

HYLEN, A., GJ0S~THER, J. og SMEDSTAD, O.M. 1972. Fiskeriundersokelser ved Bj0rnoya, Spitsbergen og i BBrentshavet 1. - 27. juni

1971. [Fisheries investigat~?n~.in the waters off Bear Island, Spitsbergen and in the 8arents Sea 1 - 27 June 1971.J Fiskets ( . Gang, 58: 257-265.

HYLEN, A. og SMEDSTAD, O.M. 1972. Norwegian investigations on young cod, haddock and redfish in the Barents Sea and adjacent

waters 1970 - 1972. Ccun. Meet. into Coun. Explor. Sea, 1972 (F:38): 1-12. [~imeoJ

JAKOBSEN, T. og NAKKEN, D. 1973. Loddeundersokelser med FIF "G.O.Sars"

i Barentshavet i februar - mars 1973. [Capelin investiga- tions with R.V. "G.O.Sars" in the Barents Sea in February - March 1973.J Fiskets Gan~, ~: 916-919.

MONSTAD, T. og MIDTTUN, L. 1973. Loddeundersokelser med FIF IIJohan Hjort" i Oarentshavet i januar - februar 1973. [Capelin investigations with R.V. "Johan Hjort" in the Barents Sea in January - February 1973.J Fiskets Gang, 59: 817-821.

NAKKEN, D. and DOMMASNES, A. 1975. The application of an echo inte- gration system in investigations on the stock strength of the 8arents SeB capelin (Mallotu8 villosus, MOller) 1971 - 1974. :'ou!l' M8et._ int. CDun, Explor. Se8, 197~ (8:25) 1,a9.

[MimeD

.J

i I

Table 1. Distribution of cod on year classes, numbers in millions and percentages, in the eastern and western part of the survey area in 1976 and 1977.

~

1976 1975 1974 1973 1972 1971 1970 1969 Older Total I Area class

NI%

Year

N % N % N % N % N % N % N %

N % N

1%

.. 1976

-

934 93 50 86 240 78 83 39 17 20 6 6 1 5 + + 1332 74 East 1977 29 66 897 92 67 66 136 47 34 28 6 15 4 9 + 4 + 4 1175 72 1976

-

68 7 8 14 69 22 61 66 80 104 94 19 95 3 100 465 26

I I

129 West

2SJ

1977 15 34 78 8 34 34 151 53 90 72 39 85 37 91 7 96 2 96 454 . ! 1

N -

1002 58 309 212 83 110 20 3 1797 l I 1976

I

ufo

-

55.8 3.2 17.2 11. 8 4.6 : 6.1 1.1 0.2 100.0

I

Total

~

44 975 101 288 124 45 41 7 3 1629 1977

%

2.7 59.9 6.2 17.7 7.6 2.7 2. 1 0.4 0.2 100.0

I

CJ

- 9 "'

Table 2. Yearly reduction in percent and total mortality (Z)

calculated from abwndance estimates from acoustic metho~s

(AM)

and virtual population analysis

(VPA).

, 0, i

% (AM) ~ (AM) Z (VlpA)

Yea;r ^1974~ 1975- ^1976~ 1974- 1975- 1976- 1974.- 1975" 1976-

Gl~$l?e s 1975 1976 1977 1975 1976 1977 1975 1976 1977

I ~ :

1969 35 43 65 0.40 0.56 1. 06 0.64 0.69 0,62 1970 36 35 63 0.45 O. -43 0.98 0.60 0.57 0.55

1971 46 ^{. ,} ·0.61 0.48

~9'7? 42 0,54 _Of~8

1973 7 0.07

0.4

⁷

-

Ta-,L-,""S. Distribution of haddock on year classes, numbers in millions and pprcentages) in the eastern and western part of the survey area in 1977. Yearclass 1976 1975 1974 1973 1972 1971 1970 Older Total N in millions 105 . 529 110 24 1 I + I 770 East

%

of yearclass 42 69 57 43 12 9 4 5 59 N in million s 145 233 82 32 7 7 10 14 531 West

%

of yearclass 58 31 43 57 88 91 9n 95 41 N in millions 250 762 192 56 8 8 10 15 1301 Total

%

of stock 19.2 58.6 14.8 4.3 0.7 0.6 0.8 1.1

I I

-" o

1

75°'

74°

,73°

72?

71°

70⁰

69°

68⁰

- 11 -

l' -~----~-~---_ _ _ """'_""""""-' _____ '-.""_-r-,..,...._'_ "'~---"--.. -

Q

l--..]5

z-z

1 I

~

1""""1 --r-..---r-'.."...---r~

7. ·1

- -~!'" • 2

,--.r~,.---,l. ~ ^r

10° ,12⁰ 11.° 16° 18⁰ 20° 22° 24° 26° 28° 30⁰ 32° ~4°' 36° 380 40° 42° 4(.°, 46^q

Fig., 1. Survey routes and hydrographicstatio,ns.

0

SOt\de ~tatio;t').,

2) boarder between eastern and western area.

'75

74°

73°.'

72°'

71°

70°

69°

68⁰

Q

h l'I\"~ _~ L~

t!<l.'h'4J,

~~

15

~~?t4r~

~~,-~r'"

~~

q .1

Ad

jiill'~ , I "1' i . "

~j : - " - . , - . , - . , - , - , ~, I I , i I i i

100 12° 14° 16° 18° 20° 22° 21.° 26° 28° 30" 32° 34° 36° 38° 1.0° 42~ I.I.Q 1.6⁰

Fig. 2. Trawl stations. 1) Bottom trawl, ,2) Mid,wat~r trawl.

75°'

74°

73°'

72'>'

71°

70°·

69°

~ 12 ""

Q

~

^{, / / / ,-. , .. , / '}

~-'--

U· 5~

~~

.. -... ---l

\.~~O I

~ 2--\~

3

~12~

~'

68° I 1<1" ^{I I} ,g.,-{,,,, ^I I ^'-,), I

~ '1

I

10° 12° 14° 16° 18° 20° 22° 24° 26° 28° 300 32° 34° 36° 38° 40" 42° 4/'° 1.6°

Fig. 3, Temperature tOe at 150 m depth.

75

74°

o

73°

72°

:2 ---- 71°

70°

~ ~"

"

^'-'-

'.

- r ~----.-~...,--r----r-~~'T----tl-r--rt

69°'

!i8°

10° 12° 14° 16° 18° 20° 22° 24° 26° 28° 30" 32° 34° 36° 38° 1.0° 42°' 44~ 1.5°

Fig. 4. Temperature t

° e

near the bottom.

75⁰.1

!

71.°

73°

72°

71°

70⁰-

69°

- 13,

---~--~~---'----l

J:0- ^I

A1

^{,20, ~20} _50J ^{50 10}

L

~20

^s'Ql

/f;~

\~L/,~sU ,20~

. ~ ~;JfJJif'?

_O~'-'//

\

68⁰¹

,""I

,e ^{I )}

26° 28° 30° 32° 34° 36° 38⁰ 1.0°. 1.2° 41.0 1.6°' 1.8°

Fig. 5. Echo abundance of _cod and haddock

observed by R/V "G. O. Sars".

75°-

71.°

73°

72°

71^0•

70°

69°

o~

, , 5

-

~GJU/ _{~_~~ \to}

"

68°-+-,-^o --.---,---,----r I 1 I

~

^"'--. ,,-- •

26 280 300 320 ³⁴⁰ 1 ^36" 1 1 I " , 1 '\ ^{I 1 I 1} -.-.--,L--, 1 I. I I 38° 1.0⁰ 1.2° 1.1.0 1,6° 1.8°

Fig. 6. Distribution of 1 year old cod in

1000 per (nautical mile)2.

- 14 ~

75°

74°

73°

n°

?

68°'1 ,'>', ^{I ' If I} ,~

26° 28° 30° 32° 34° 36° 38° 40° 4~0 44° 46° 48°

Fig. 7. Distribution of 2 year s old cod in

1000 per {nautical mile)2.

75°

71.?

73°

n°

70°·

69°

6s01 i I i i I I j , i I r I I~ I I J ' a' ,l,

26° 28° 30° 32° 31.° 36° 38° 40° 1.20 44~ 46° 4ao

Fig. 8. Distribution of 3 year sold qod in

1000 per {nautical mile)2.

':f~' :'

')~~'~; ^{.. :.}

- 15 .~

"o{ ^l

71.0

JNo _~O~~

73°

70"

69°

68°f-" .-.----r-

,-,-.-b

26° 28° 30^Q• 32° 31.° 36° 38° (.0° 1.2° 41,0 46° 4$°

Fig, 9. Distribution

of

4 years and older cod - numb.er s in 1000 per {nautical mile)2.

100

30

25

V)

5 ~

²⁰

.~

g

o

o

u

u.

I:> 15

0:

~

:::>

z:

10

5

I~

I~

-

I·

I-

o

T

.' . ;. .

~.:

\\-

.

r.,;,

:;:

L

I

.1 1I

....

::::

...

?

,' . . ^'.

.'. ^-:.:

.', {

~: ~

^.;.;

I ^ill

1.1.

•••••

••••

••• 1

,...

••••

:

^{r:::: .:.}

;:;

~.'>

.... _:.:

<

^{:~' ~} ~t ^:;::

,', _':;

,'~

^"ll

:;; ^". ::::

76 75 71. 73

- 16 -

o

¹

~ ~

i:S 3 c:J ₀ 4

'"

1

~ ~ ~ ~ ....

;:::

;:;:

::::

::::

::::

.. ^' :::: ~

::::

:;::

.{ _....

::1:

, :::: _'~"

\}

• •••

i

^{r;:: :.:}

1I ^~,'ii

^....

":::: ^{,'0' ....} _~~{ j

•

•••••

,','

. ...

p~/~ • :r-

~

(

,,";':

~>:::

^~

,

',',

"::::; .)~

< ;::: [.~ ^,','

~} ~.: \ ~y ^{0. {} :::::

ti ::i:h

_{~ Ml}

" ^..,..,

72 71 70 69 68 57p6 6564

YEAR CLASS

Fig, 10. Numbers in millions of cod versus year classes as

o bs er'Ved on surveys in 1) 1974, .2)1975; 3) '1976, 1) 1977.

- 17 -

---..

---.--·-·----~~~·----1

75°' I

71.°

73°

72°

69°

68° I ,,,,,) , ' , ^I

26° 28° 30· 32° 34° 36° 38° 1.0° 42° 1.4° 46° 48⁰

Fig. 11. Distribution of 1 year o~d hadgQck

in 1000 per {nautical mile)4.

75°

o

74°

73°· ,.

72°'

70°

69°

26° 28⁰ 30⁰ 32° 34° 36° 38~ 40° 42° I.i,' "f," "Cl'

Fig. 12. Distribution of 2. year$ and older

haddock .~ number s in lOOO per

(nautical mile)2.

l/')

z o ::J ~

:z:

~

800

750

300

250

!:i::: 200

u o

· 0

o

«

:x:

u. o

a:: 150

UJ co

:z: ::::>

z

100

50

o

- 18 -

'l.:,

..

nnnn

76 75 74 73 72 71 70 69+

YEAR CLASS

Fig. 13. Numbers in millions of haddock ver~us year c;lasses as observed on Gruise :i,n 1977.

75°'

74°

n°

~. V[J

_{10 20}

,./ 10

,507)

72°1,

00

50~

_-=--

71°

70°

69°

~19 •.

O.

68°\ ""~ 01 ,),

26° 28° '30⁰ 32° 34° 36° 38° 40. 42° 44°. !.li^P 1.8°

Fig. 14. Echo abundance Q£ l'e<;l£~sh observed by R/V "G. O. Sal's",