CM_1988_H_14.pdf (1.426Mb)

Not to be cited without prior reference to the authors.

International Council for.

the Exploration of the Sea

C.M. 1988/H:14

~

Ref. L

Pelagic Fish Committee

Ref. Biological Oceanography Cttee

DISTRIBUTION, DRIFT AND CONDITION OF HERRING LARVAE OFF WESTERN NORWAY IN 1987

INTRODUCTION

, By

R. Sætre, H. Bjørke, and P. Fossum Institute of Marine Research P.O.Box 1870, N-5024 Bergen

Norway

After 1959 the Norwegian spring-spawning herring have been spawning along the western coast of Norway north of 62° N. During the sixties the stock was reduced to a minimum. In the recent years there has been a slight increase in the spawning stock and in 1983 a rich year class was produced.

In 1985 the Institute of Marine Research started a project to study the recruitment mechanisms of the herring. Preliminary results from the project's larvae investigations in 1985 and 1986 have been reported (BJØRKE, FOSSUM and SÆTRE, 1986, FOSSUM, BJØRKE and SÆTRE, 1987). In addition to the early larvae studies in March-April, the

project includes investigations of drift and distribution in May and in July. In August-September the distribution is covered by the international 0-group investigations in the Barents Sea.

The present report gives some preliminary results from the investigation on the herring larvae in March-April 1987.

MATERIALS AND METHODS

The study was carried out during the periods 28 March - 8 April and 10 - 20 April. The first coverage {Fig. 1) was the most complete while the second one was hampered by bad weather. Herring larvae were sampled with a modified conical net of 0.5 m² opening and 375 p m mesh size {ELLERTSEN et al. 1984) from 150 m (or 5 m above the bottom) to the surface. The vertical distributions of temperature, salinity, nutrients and chlorophyll contents were observed by a CTD sonde with a rosett sampler. Seven Argos satellite-tracked, drifting buoys were deployd. These were equipped with a 10 m² window-blind drogue attached to the buoys via a 60 m tetherline.

The materials for the vertical studies were derived from three experiments; one made 10-11 April near Grip, one 12-13 April near Storholmen 'and ane 18~19 April near Sklinna (posisions E, D and F in Fig. 1). The sampling was made over depths of 213, 175 and 147 m respectively. All experiments were made with a Mocness 1 m² sampler

(mesh 333p) (WIEBE et al 1976). The tows were made at a speed of 1.5-2 knots from a fixed point in a fixed direction.

Between 50 and 100 m³ was filtered with the Mocness sampler within each depth interval. At the onset of the experiments the larvae concentrations were located with a vertical plankton haul.

2 .

The number of larvae per m surface was calculated by the formula:

N= n I

V

where n is number of larvae in the sample, I is depth interval and V 2

is volume filtered.

The development of the larvae was classified according to DOYLE

(1977),

and the duration of the stages are given in Table

1

(below).

Table 1. The mean duration of the different substages. {For references see BJØRKE, FOSSUM, NEDREAAS and SÆTRE

1987)

Stage la Stage lb Stage le Stage 2a Stage 2b

3

days

4

days

3

days

11

days

5

days

The herring larvae were preserved in 2% formalin for staging (according to DOYLE

1977),

for dry weight and gut content analysis.

Because of gut content voidance in herring larvae (HAY

1981,

BLAXTER and HOLLIDAY

1963,

ROSEN~AL

1969),

only a comparative analysis with material sampled the two previous year and qualitative analysis were performed. Because of weight loss during formalin fixation {THEILAKER and DORSAY

1980),

samples of larvae were also staged and length measured in vivo, dried to constant weight and weighed in the laboratory on a Cahn electrobalance to searest pg.

If food organisms could be recognized through the epithelium of the gut of the preserved larvae, they were dissected out and classified into one of the following two groups; copepod eggs and copepod nauplii. No other food items were found~ The larvae were rinsed in fresh water, dried to constant weight and weighed after the presented procedure.

RESULTS AND DISCUSSION

Hydrography

The distributions of surface temperature and salinity during the first

coverage {Figs. 2 and

3)

show approximately the same pattern as in

1986

with higher values in the northern offshore areas. The northern part is usually influenced by Atlantic Water masses

{8>35)

while in the southern part the Coastal Water dominate during this part of the year. The northbound Coastal Water is flowing at the eastern side of the shallow bank centered at about

64° 40'

N,

09° 00

E. The Atlantic Water is usually associated with high values of nitrate as seen in Fig.

4.

The relativity .high values of nitrate in the Coastal W.ater indicate that the phytoplankton spring-bloom have not reach its peak.

Fig.

5

shows the vertical hydrographic structure in the three sections A, B and C. The location of the sections appear in Fig. 1. In the two southernmost s€ctions (A and B) the Coastal Water is occupying the upper

100

m over the entire shelf area. In the northernmost section, however, the Coastal Water is confined to a narrow zone along the coast. Under the Coastal Water at SECTION C water of Atlantic origin is present. This has penetrated into the trench at the eastern side of the bank from the south and is clearly seen in the horizontal distributions of temperature and salinity from the deeper layers.

Fig.

6

shows the drifting tracks within the investigated area from the seven Argos buoys while Fig.

7

shows the total tracks. The circulation pattern of the area is to a large degree governed by the bottom topography. Around the shallower banks an anti-cyclonic circulation is favoured. Six of the buoys are confined to the Coastal Current while one was brought into the Atlantic water flowing along the continental slope.

The drift tracks also indicate retention areas with prolonged residence time of the water. One is the bank area at about

63° 05'

N where the buoy released in that area described anti-cyclonic movement over the bank for 12 days before it grounded at the coast. Another such area is the bank at

63° 40'

N where the drifter circulated for about

30

days. These features seem to repeat themselves each year. The same is the case for the apparent meandering of the tracks between

65°

N and

65° 30'

N which also is an effect of the bottom topography. The irregular movements of two of the buoys just south of

66°

N, however, is probably a result of more transient processes along the Coastal

4

Current front. Instabilities of the frontal system is frequently seen in satellite IR imageso

The average transport speed of the drifters between 64° N and 66° N was 10 - 12 nautical miles/day in the Coastal Current and 3 - 6 nautical miles/day along the continental slepe.

Horizontal larvae distribution

The hatching of herring larvae started around 10 March with a peak in the last days of March. The hatching continued until about 25 April but with rather small larvae production after the first week of April

(BJØRKE, 1988).

The horizontal distribution of herring larvae of three different length groups from the first coverage 28 March - 8 April is shown in Figs. 8 -10. The distribution of the smallest larvae indicate the spawning grounds (Fig.8). In the southern part two such areas are apparent. These are about the same as observed both in 1985 and in 1986 (BJØRKE, FOSSUM and SÆTRE, 1986, FOSSUM, BJØRKE and SÆTRE, 1987).

Additionally, spawning have occurred in the northern near-coast area.

The distribution of larger larvae (Figs. 9 - 10) indicate the larval drift routes. Most of the larvae are confined to the Coastal Current close to the coast. A miner part of the larvae seems to fellow an outer raute along the continental slepe as also indicated by ane of the Argos drifters (Fig. 6).

As previously mentioned, the second coverage, 9 20 April was hampered by bad weather and is therefore incomplete. However, the distribution of the smallest larvae from this coverage is included (Fig. 11) because it indicates miner spawning also north of the area of the first coverage. Fig. 12 shows the distribution of larvae south of 63° N for three length groups during the second coverage. As expected, the numbers of the smallest larvae are low as the peak hatching was over during that period. The number of larvae between 9 and 11mm is approximately as during the previous coverage while the

amount of larvae larger than 12 mm is considerably higher.. This may indicate a relatively long residence time of the larvae in this areao

The investigations in 1987 seem to confirm the tentative pattern of drift routes and retention areas put up for the similar studies in 1986 (FOSSUM, BJØRKE and SÆTRE, 1987). The drift speed, however, was apparently higher in 1987 than in 1986.

Vertical larvae distribution

Table 2 shows the number of larvae per m² surface sampled during the experiments. Larvae without yolk-sac and without the characteristics of stage 2a described by DOYLE (1977) are omitted from this table.

Fig. 13 shows the vertical distribution of larvae of all length groups when all depth intervals were sampled. Hence the samples from near Grip 11 April at 07 hrs. are omitted. Near Grip and Storholmen the vertical distribution was almost identical with a maximum of larvae in the 0-19 m interval. At these two stations 94 and 99

%

of the larvae were s~ed in the upper 59 m respectively. Near Sklinna the vertical distribution was different with the majority of the larvae in the 40-59 m interval. At this station only 52

%

of the larvae were sampled in the upper 59 m.

Were any differences in vertical distribution observed at daylight and at night? Fig. 14 shows the vertical ·distribution of larvae caught by day and by night during the experiments. The larvae caught during the day were sampled between 0900 and 1500 hour and the larvae caught during the night were sampled between 2100 and 0200 hours GMT, both hours included. Only larvae from Table 1 are included in these figures. Near Grip the larvae seemed to concentrate in the 0-19 m interval by night and in the 20-39 m interval by day. Near Storholmen the majority of the larvae were found in the 0-19 m interval both by day and by night. Near Sklinna larvae were found throughout the investigated water column though mainly below 40 m. There seems to be no clear changes in vertical distribution during a 24-hrs. period at these stations.

6

Figs. 15-19 shows the vertical stage distribution of the larvae shown in Fig. 14. It is clear that while stage 2a was in majority near Grip and Storholmen, stage lb was in majority near Sklinna. Hence the vertical distribution of these stages will be reflected in the vertical distributions shown in figure 14. Near Grip stage 2a was most common in the 20-39 m interval by night and in the 0-19 m interval by day. Near Storholmen, however, this stage was found mainly in the 0-19 m interval both by day and by night. Near Sklinna larvae'in this stage were found in rather low numbers, but they tended to consentrate in the 0-19 m layer at night.

Near Sklinna·larvae in stage lb was in majority. Here, this stage was found throughout the investigated water column though mainly below 40 m. There seems to be no clear changes in vertical distribution during the 24-hrs. period. Near Grip and Storholmen larvae in this stage was found in higher numbers in the 20-39 m interval by.night and in the 0-19 m interval by day. However, the number of larvae in this stage (lb) at these stations is too low to draw any firm conclutions. By the same reason no firm conclusions can be made concerning the stages la, le og 2b.

Both at the stations near Grip and Storholmen stage 2a was most abundant. The larvae in this stage were, however, differently distributed by day at these stations. While they were most abundant in the upper 19 m at the station near Grip, they were most abundant in the 20-39 m interval near Storholmen. The hydrographical conditions were almost identical with no pronounced pycnocline (Fig.14). Food conditions could have been different at these stations. Samples are taken, but have not been worked up yet. Light conditions could also have been different, but these were unfortunately not measured. This is highly recommended during further trials. Hence, this far, no explanation can be given for the observed differences in the vertical distribution of stage 2a near Grip and Storholmen.

Conclusion: Herring larvae 12-32 days old are mainly found in the upper 59 m and they seems to concentrate in the upper 19 m by night.

Larvae 3-7 days old are found throughout the investigated water column

though mainly below 40 m. There seems to be no clear changes in vertical distribution during a 24 hrs. period of larvae in this stage.

These observations does not deviate from observations made during similar studies in 1985 (BJØRKE et al. 1987) and 1986 (FOSSUM, BJØRKE and SÆTRE 1987}.

Condition of herring larvae

The material consisted of 1770 herring larvae of standard length 8-18 mm and dry weight 50-1265 ~g. 1692 l~rvae were preserved in formalin, while 78 were staged and measured in vivo. The mean standard length and dry weight of the larvae in different developmental stages are given in Table 3 and 4. The larva! material sampled on this survey was composed of both yolksac-larvae and post-larvae. The development of the larval population was somewhat delayed compared to what was found in 1985 when the population was composed of post-larvae in stage 2a.

Compared to 1986, however, when the larvae were in the yolksac stage, the larvae had reached a more advanced stage in the present material

(FOSSUM, BJØRKE and SÆTRE 1987}.

It can be seen from this tables that the larvae shrink during fixation, and tests of the means of length and weights befare and after fixation all show a highly significant length and weight loss (47<t<11.6}. The percent shrinkage is given in TableS. The larva!

samples are from the second coverage. The material sampled the previous year had only half the length-shrinkage compared to the present (3.3-6.5%). while the weight loss was slightly higher (38.6- 45.5%}, {FOSSUM, BJØRKE

&

SÆTRE 1987}.

·In fig. 20 length/weight plot of the larvae not exposed to formalin is shown. There is a streng length/weight-relationship indicated by a correlation coeffisient r=0.97. The slope is higher than was seen with the unpreserved material for 1986. 0.095 compared to 0.082, indicating a faster growth in 1987 than in 1986.

The plots of the preserved material is shown in figs. 21-23. There is a slightly higher growth parameter (the slope of the curve} during the 8

second coverage, and a test of the condition shows that this is significantly higher on the second than on the first cover age (t=4.14). The reasons for this are not full y understood. There can be problems with the sampling procedure, the pre y conditions can have improved (not an item for the investigation this year) or it can be a general condition-improvement of growing larvae. A plot of the condition factor (k=l(mm)3/10w(pg) versus standard length for the two coverages is shown in figs. 24 and 25. The material is somewhat scattered but there is a tendency of decreasing condition towards yolkresoption, and then the condition is increasing when the larvae starts to grow. So the reason for the difference in condition between the two coverages may be that the samples contain larvae of different age. Length/weight plots of preserved material have weaker length/

weight relationships, because of variable weight loss during fixation, r=0.85 for the first coverage and r=0.93 for the second. The growth parameter (the slope = 0.08) is higher than in 1986 (0.04) and equal to the parameter found in 1985 (the slope=0.08), indicating reduced growth in 1986.

The diet of the larvae during stages 1a-2b, a time span estimated to be 28 days (BJØRKE, FOSSUM

&

SÆTRE 1986), is shown in fig. 26. There were found 345 cap. nauplii and 156 cap. eggs in the larval guts. No other food items were found. The low feeding ratio in the larger larvae is most probably due to the emptying of the gut during catching and preservation. The persistaltic movements of the gut must be much strenger in the more advanced larvae. There is a strenger impact of cap. eggs this year than the previous two. The number of cap. nauplii is on the same level as in 1985 and higher than in 1986, another indication of good larvae conditions in 1987. First feeding was seen in stage lb larvae (3-6 days old). Cap. eggs seems to be an important first feeding item. Later on, the importance of this food item. is reduced.

From the mean length and stage duråtion data the growth rate can be calculated. A mean growth rate of 0.36 mm/day in the period 2-26 days post hatching were found. In the yolksac-period the growth was slower, 0.28 mm/day, but in the post-larval period 0.41 mm/day. The specific growth rate can be calculated to be 6.8%, by the method shown

10

in BJØRKE; FOSSUM

&

SÆTRE (1986). Both the growth rate in length and the specific growth rate are almost identical to the rates-round in 1985, and are in accordance with previous results on the same herring stock (DRAGESUND

&

NAKKEN 1973), and with results with larvae from other stocks (LOUGH et al. 1982, WOOD

&

BURD 1976).

REFERENCES

BJØRKE, H. 1988. Sildeklekking (Havforskningsinstituttets

på Egg- {15):1-25.

Møre og

i 1986-87.

Larveprogram) ,

HELP 1988

BJØRKE; H. , FOSSUM, P. , NEDREAAS, K. and SÆTRE, R. 1987.

Yngelundersøkelser - 1985. HELP (Havforskningsinstituttets Egg- og Larveprogram), 1987 (12}:1-74.

BJØRKE, H., FOSSUM, P. and SÆTRE, S. 1986. Distribution, drift and condition of herring larvae off western Norway in 1985. Coun.

Meet. int. Coun. Explor. Sea,1987(H:39}:1-15.

BLAXTER,J.H.S. and HOLLIDAY, F.G.T. 1963. The behaviour and physiology of herring and other clupeids. P. 262-394 in RUSSEL, F.S. ed. Adv. mar. Biol. Academic Press, London and New York: 410 p.

DOYLE, M.J. 1977. A morphological staging system for the larval devel- opment of the herring, {Clupea harengus L.}. J. mar. biol.

Ass.,

51:

859-867.

DRAGESUND, O. and NAKKEN , O. 1973. Relationship of p~rent stock size and year class strength in Norwegian spring spawning herringe Rapp. P.-v.- Reun. Cons. perm. int. Explor.Mer., 164: 15-29.

ELLERTSEN, B., P. FOSSUM, P. SOLEMDAL, S. SUNDBY and S. TILSETH. 1984.

A case study on the distribution of cod larvae and

availability of prey organisms in relation to physical processes · in Lofoten. The Propagation of Cod Gadus morhua L.

Flødevigen rapportser., !:453-477.

FOSSUM,P., BJØRKE, H. and SÆTRE, R. 1987. Distribution, drift and condition of herring larvae off western Norway in 1986. Coun.

Meet. int. Coun. Explor. Sea,1987(E:13):1-10.

FOSSUM,P., BJØRKE, H. and SÆTRE, R., 1987. Studies on herring larvae off western Norway in 1986. HELP {Havforskningsinstituttets Egg- og Larveprogram), 1987 (8):1-16, +appendix 23 p.

HAY,D.E. 1981. Effects of capture and fixation on gut contents and body size of Pacific herring larvae. Rapp. P.-v. Reun. Cons.

perm. int. Explor. Mer, 178: 395-400.

LOUGH, R.G., M. PENNINGTON, G.R BOLZ and A.A. ROSENBERG. 1982. Age and growth of larval atlantic herring Clupea harengus L.based on otolith growth increments. Fish. Bull., 80:187-199.

ROSENTHAL, H. 1969. Verdauungsgeschwindigheit, Nahrungswahl und Nahrungsbedarf bei den Larven des Herings, Clupea harengus L.

Ber. dt. wiss. Kommn. Meeresforsch., 20: 60-69.

THEILACKER, G. and DORSEY, K. 1980. Larval fish diversity, a summer of laboratory and field research. IOC Workshop Report no. 28:

105-142.

WIEBE, P.H., BURT, K.H., BOYD, S.H. and MORTON, A.W., 1976. A multiple opening/closing net and environmental sensing system for sampling zooplankton. J. Mar. Res., 34: 313-326.

WOOD, J. and BURD, A. C. 1979. Growth and mortality of herring larvae in the central North Sea. Coun. Meet int. Coun. Explor.

Sea,(H:8):1-7.

WIEBE, P.H., BURT, K.H., BOYD, S.H. and MORTON, A.W., 1976. A multiple opening/closing net and environmental sensing system for

12'

sampling zooplankton. J. Mar. Res.,

34: 313-326.

Tab le

2.

Num ber of larvae per m ² sur face sampled during the experiments.

St. 444,

near Grip.

Date

10

April

1987 11

April

Ho ur

17 20 22 24 02 04 05 _07 09 12 13 15 17

Depth

0-19 48 126 149 95 183 72 25 - ^o 18 20 15 61 812 20-39 38 21 4 14 23 37 29 46 32 14 32 25 27 342 40-59 o

2

2

₅

29 34 2 11 o 8 27 12 10 142 60-79 1 4 1 2 1 2 2 1 o 1 4 2 1 22 80-99 o 1 o 2 2 1 o 1 o o 1 o o 8

100~119

1 3 1 2 1 o 4 o o o 1 o o 13 120-139 o o 1 o o o 2 o o o o o o 3

88 157 158 120 239 146 64 59 32 41

⁸⁵

54 99 1342

St.

478,

near Storholmen.

Date

12

April

13

April

1987 1987

Ho ur

20 23 01 03 05 07 09 11 13 15 17 19

Depth

0-19 48 40 128 77 o 40 28 14 91 56 85 116 723 20-39 62 10 35 34 o 35 26 18 14 23 11 4 272 40-59 3 3 14 9 4 6 3 o o 12 1 3 58 60-79 1 o 2 5 5 o o o o o o 1 14 80-99 o o o 1 1 o 1 o o o o o ₃

100-119 o o o o o 1 o o o o o o 1 120-139 o o 1 1 o 1 o o o o o o ₃

114 53 180 127 10 83 58 32 105 91 97 124 1074

St.

519,

near Sklinna.

Date

18

April

19

April

Ho ur

19 21 23 01 03 05 07 09 11 13 15 17

Depth

0-19 5 11 8 31 8 12 2 2 1 3 7 10 100

20-39 12 14 5 12 1 13 3 3 3 4 3 47 120

40-59 6 18 11 18 5 9 27 15 30 12 19 221 391

60-79 10 22 15 41 11 7 49 30 6 26 13 19 249

80-99 o ₃ 6 27 27 3 9 6 3 52 7 8 151

100-119 o 6 9 16 1 1 2 2 4 7 1 3 52

120-139 o 6 8 16 2 1 ·4 6 1 2 1 o 47

33 80 62 161 55 46 96' 64 48 106 51 308 1110

Table

3 .

Standard length and dry weight in the different developmental stag es (preserved material).

St age

1a 1b 1 c 1d 2a 2b 2c 3a

Mean standard length (mm)

8.3 ± 0.8 8.4 ± 0.9 9.4 ± 0.9 10.1 ± 0.8 12.2 ± 1.5 16.4 ± 1.1 17.2 ± 1.0 18.8

Mean dry . weight (J.LQ) 147 ± 36 120 ± 26 123 ± 28 147 ± 30 258 ± 104 636 ± 109 836 ± 60 1265

Nos. of larvae

86 331 281 338 487 9 5 1

Table 4 . Standard length and dry weight of larvae staged and measured in viva.

Stage

1 c 1d 2a 2b

M ean standard length (mm) 11.2 ± 0.4 11.0 ± 0.6 13.6±1.8 17.7

Table 5 . Shrinkage due to fixation Stage

1d 2a

Length

(o/o)

10.0

10.2

Mean dry weight (J.Lg) 219 ± 32 227 ± 32 440 ± 193 1 1 1 8

Weight

(o/o)

36.5

38.2

Nos of larvae

5

22 46 1

G. O. SARS 28.03- 08.04. 87

0 ARGOS BUOY DEPLOYMENT 6. PELAGIC TRAWL

X VERTICAL NET HAUL

• MOCNESS STATION

• CTD - NET HAUL

NUTRIENTS - CHLOROPHYLL

FigQ le Grid of stations during the first coverage, 28 March - 8 April 1987. Bathyrnetric contours for each 100 rn are included. Inserted rnap shows the location of the studied area.

100

. ...;.:

Fig~ 2. Surface temperature, 28 March

".

l l • l

·,.

l l

6:5 l

.

^{· ..}

t°C - Om 28.03-08.04.87

10°

8 April 1987.

HO

JOO oQO

·· ...

!00.

100

'

.

s-om

28.03 - 08.04.87 .·· ..

2~0

62°'~--~~~,~~~~--~----~----~--~----~----T---~----~----T---~----~----~--~

40

Fig. 3. Surface salinity, 28 March 8 April 1987.

100 400

lO O.

Fig. 2. Surface ternperature, 28 March

l

" ...

l • l

,

l ^...

l

6:5

.

^{· ..}

t°C - Om 28.03-08.04.87

8 April 1987.

•o o

4QO

J~O · ... ···

,•'

100 •...

....

o,'

Fig. 3. Surface salinity, 28 March

lO

..

O

s-om

28.03 - 08.04.87

10°

8 April 1987.

400

lO O,

N03 (pM) - Om 28.03 - 08.04.87

Fig. 4. Surface values of nitrate, 28 March- 8 April 1987.

200

300

400

400

400

t•c

SECTION A 1 APRIL 1987

Fig. 5. Hydrographic sections A, B and C. The location of these is indicated in Fig. l.

lOS

400. 700

:ioo·

:· .... ··.:

?'

l(l(l 11 •

·. """'!. : . . ·.·.: c·~.f-;oo ...

. .'.···

DEPLOYMENT POSITION

6 RECOVERY POSITION

62°~--~--~~~~~~.---~~---r----r----r----r----r----.----.----.----,----~--~

40 10°

Fig. 6. Tracks of the drifti~g Argos buoys within the investigation area drogued at 60 m depth.

04oo 09oo 140v 15oo

69oo+---~---~---~-690v

6 8 o o 6 :3 o o

6 7 o o ^{6 7 o J}

6 6 00 6 6 o o

6 5o o ^{6 5o o}

6 4 00 6 4 o o

6 J v v 6 Jo o

o

DEPLOYMENT POSITION

l 5 7 ':J

Cl RECOVERY POSITION

o

TRANSMITTING STOPPE O

6 2 O v ~· l 6 2 o o

0 4 '. o ^{9 0 J 1 4 o o 1 5o o}

Fig. 7. The total tracks of the drifting Argos buoys.

100 100

: ~

•...

^{. ..} •·...

.

^{.. ·}

.

^{•.: ....} ··' :·.

. ^~

100 :•.

.·. .

^:

.

^{-: .. · ..}

100

...

~ ... · ...

. ··• ^,·

.. •..

·'···

HERRING LARVAE (N/m2) < 9mm 28.03.-08.04.1987

Fig. 8. Distribution of herring larvae

<

9mm (N/m 2 ), 28 March- 8 April 1987.

4CO

lO O

JOO

100

..

lO O

.

_/0.

^~

_{o· • 10 .!-}

~0..-­

.

^·~

o~·

.

·.\..

HERRING LARVAE 9mm .:s (N/m2) c 12 mm 28.03.-08.04.1987

Fig. 9. Distribution of herring larvae between 9 and llmm (N/m 2 ), 28 March- 8 April 1987.

)00

' . . • · o • 'i• ..

·· .... ·

.,. ... : •O ... :·. 10~

:

.

· .. ^:

..

o

HERRING LARVAE (N/m2) ~ 12 mm 28.03.-08.04.1987

1~0

62°,_---r--~,~~~~~.----r----r---~---.----~---.---,r---,---~----~---r--~

10°

Fig. 10. Distribution of herring larvae >llmm (N/m 2 ), 28 March 8 April 1987.

04oo osoo oaoo 1 ooo 1 2oo 1 4oo

67Jo4---~---~---~---~---r67Jo

6 7 00 6 7 00

6 6 00 6 6 00

6 5 00 6 5 00

6 4 00 6 4 00

6 3 00 6 3 00

62oo+---~~~~~---r---.---.---+62oo

0400 0600 0800 1000 1200 1400

G. O. SARS 9-20/4 1987.

SILDELARVER 0-8 MM PR.M2.

Figø ll. Distribution of herring larvae <9 mm (Njm2), 9-20 April 1987.

·'

,11 ,2

,a ,a

·'

6200+---L~~~~---~---~6200

0400 0600 0800

G.O.SARS 9-20/4 1987.

SILDELARVER 0-8 MM PR. MMZ.

,u

,2 ,a

,l ,1 o

,14 ·'

,a ,u

,12 .~o

..

^{,11 ,H}

,H ,u

,2 ,11

,u ,l ,21 ,H ,21

.1•,,. ^,31

o 400

6Joot---0-6~oo---~~~~----~--~0~8+o~Joo

Fig. l 2 •

,a

,12

·' ^,a

,11

,11 ·' ^,22 .• ·' ^,27

,2 ,1+

,l .• ^,1J1

,a ,10 ,10

,l

..

..

,1J ,U ,l ,a ^,14

·'

..

,U ·'

J/A/2.

Distribution of groups south of

herring l~rvae in three 630N (N/m ), 9-20 April

length 1987.

::::.?!

:z:

---l

<C

>

0:::

LL..J 1-:z:

::c

1-- CL LJ...I

o

:::?:

:z:

--l

<

>

a:::

w

l -z

:c

t - CL w o

::E

:z

--l

<(

>

0::

LL.J 1-:z :c

1-- 0...

o w

A ^GRIP

26 27

33 34

0-19

20-39

·.

_... '

\

.

•, '

40-59 ^\ ' ^\

\

60-79 80-99 100-119 120-139

o

200 400 600

8 STOR HOLMEN

2~5

2?

33 34

0-19

· ..

_',\ '

\

20-39 ^{1'·. \} ,., ^•,

"(,

40-59 ^{') .,,} ··, 60-79

80-99 100-119 120-139

o

200 400 600

c _2e.s ^SKLINNA

_2~

33 34

0-19 ^\ \

\

\

20-39 ^{\ \} \

l

40-59 60-79 80-99 100-119 120-139

o

100 200 300 400

\

\

\

\

' _{' '}

\

' \

\

\

.

' ^\ ' ^\ 800 1000

'<·. ,., '· .•

\ ·•

1'.

,

_,., ^..

~

~

'

^'.

··~

6 ^{•,\ ' \}

800 1000

500 600

28 ^ot 35 5o

1oo

D

to

c

- - temperature ... density ... _ -· salini ty

1200 nos/m2 surface

2l.5 ot 3'5 so 100

D

- - tempera ture ... density ----salinity

7 ^{t° C}

12 00 nos/m2 surface

27.5 ot 3'5 solo o

D

- - temperature ... density

~--- salinity

t° C

700 nos/m2 surface

FIG.

13.

Vertical distribution of herring larvae, temperature, salinity and density at the stations near Grip, Storholmen and Sklinna.

~

:z

- l

<

>

a::

L.a..J

...

:z :c ...

0..

L.a..J Cl

:!!

:z

- l

<

>

a::

L.a..J

...

::z :::c ...

0..

L.a..J Cl

:!!

::z

_ J

<C

>

a::

L.a..J

...

::z :c ...

0..

L.a..J Cl

0-19 20-39 40-59 60-79 80 -'99 100-119 120-139

o 20 40 60 80 100

c

0-19 - 20-39 - 40-59 60-79 - 80-99 - 100-119- 120-139-

E

0-19 20-39 40-59 60-79 80-99 100-119 120-139

NOS/M2 SURFACE

STOR HOLMEN

Do yl ight

u l

l l l

o 50 l 00 150

NOS/M2 SURFACE

SKLINNA

Doylight

120

l

200

o 1 o 20 ~o 40 so 60 10 80 NOS/M2 SURFACE

::e :z

- l

<

>

a::

L.a..J

...

:z :c ...

0..

L.a..J Cl

O

^{All stoges :!!}

:z

- l

<C

>

a::

L.a..J

...

:z :c ...

0..

L.a..J Cl

O

^{All stoges ~}

::z

_ J

<

>

a::

L.a..J

...

:z :c ...

0..

L.a..J Cl

0-19- 20-39 -...__

40-59 -,...

60-79 - 80-99 - 100-119- 120-139-

l

-,

l l .1

o 100 200 300 400 500

D

0-19 20-39 40-59 60-79 80-99 100-119 120-139

F

0-19 20-39 40-59 60-79 80-99 100-119 120-139

-

- - - -

-

-

NOS/M2 SURFACE

STOR HOLMEN

N ight

o 20 40 60 80100120140160180 NOS/M2 SURFACE

SKLINNA

N ight

l

r

l

l

l

l

l r l

o

20 40 60 80 90 NOS/M2 SURFACE

FIG.

14.

Vertical distribution of larvae in all stages at the three stations during the day and the night.

O

^All stoges

O

^All stoges

::::E z

-1 <

>

a::

l.I.J 1-z

::J:

1- CL u.J o

0-19 20-39 40-59 60-79 80-99 100-119 120-139

0-19 20-39 40-59

80-99 100-119 120-139

STOR HOLMEN

Daylight

Lorvoe < 3 doys old

0.0 0.5

NOS/M2 SURFACE

SKLINNA

Da yl ight

Lorvoe < 3 doys old

1.0

o

2 4 6 8 10 12 14 16 NOS/M2 SURFACE

O

^{Sloge lo}

O

^{Stoge lo ::::E}

z

....J

<

>

a::

u..J 1-z

::J:

1- CL u..J

o

0-19 - 20-39 - 40-59 - 60-79 - 80-99 - 100-119- 120-139-

SKLINNA

Night

Lorvoe < 3 doys old

l

l

o

l ^l

l l

l

NOS/M2 SURFACE

l

l 2

FIG.

15.

Vertical distribution of larvae in stage la at the three stations during the day and the night.

O

^{Stoge lo}

...J

<

>

0:::

u.J 1-z

:I: l -

a..

o u.J

:z:

...J

<

>

0:::

u.J 1-z

:I: l -

a..

u.J o

z

...J

<

>

0:::

u.J 1-z

:I:

l -a..

u.J o

0-19 20-39 40-59 60-79 80-99 100-119 120-139

0-19 20-39 40-59 60-79

80~99

100-119 120-139

0-19 20-39 40-59 60-79 80-99 100-119 120-139

o

2 3

NOS/U2 SURFACE

STOR HOLMEN

Da yl ight

larvoe 3-7 days old

o 2 3

NOS/1.42 SURFACE

SKLINNA

Daylight

Larvoe 3-7 days old

5

O 1 O 20 JO 40 50 60 NOS/M2 SURFACE

~ Stoge lb

~ Stoge lb

~ Stoge lb

...J

<

>

0:::

u.J 1-:z:

:I: l -

a..

u.J o

::::!;

:z:

_ J

<

>

0:::

u.J 1-:z:

:I:

1-a..

l.J..J

a

:z:

...J

<

>

0:::

l.J..J 1-:z:

:I:

l -a..

u.J a

0-19 20-39 40-59 60-79 80-99 100-119 120-139

0-19 20-39 40-59 60-79 80-99 100-119 120-139

0-19 20-39 40-59 60-79 80-99 100-119 120-139

o

2 3

NOS/1.42 SURFACE

STOR HOLMEN

Night

larvoe 3-7 days old

o ^{l 2 3}

NOS/1.42 SURFACE

SKLINNA

Night

Larvoe 3-7 days old

5

O 1 O 20 JO 40 50 60 70 80 NOS/M2 SURFACE

FIG.

16.

Vertical distribution of larvae in stage lb at the three stations during the day and the night.

~ St age lb

~ St age lb

~ St age lb

GRIP

Da yl ight

lorvoe J-7 doys old

o -19 ~J~fj~~~~tf~~-

:z

- l

<

>

0:::

w

1-:z

2 o-J 9 ~Jg§§~~~?~~~~~ft*-*l.~i~~f~~?-

:z:

-1

40-59

60~79

80-99 100-119 120-139

~ 40-59

0:::

~ 60-79

:z 80-99 ::z::

6:: 100-119

I..I.J

o 120-139

- l

<

>

0:::

w

1-:z ::z::

l -c..

w o

0-19 20-39 40-59 60-79 80-99 100-119 120-139

o 2 3 4 5

NOS/M2 SURFACE

STOR HOLMEN

Do yl ight

lorvoe 7-10 doys old

o 2 3 4 5

NOS/M2 SURFACE

SKLINNA

Doylight

lorvoe 7-1 O doys old

o 2 3 4 5 6 7

NOS/M2 SURFACE

~ Stoge le

ffi1

Stoge 1 c

fill

St age 1 c

::z::

0-19 20-39 40-59 60-79 80-99

6::. 100-119

w

o 120-139

::::æ :z:

- l

<

>

0:::

w 1-:z:

::z::

1- Cl..

w o

- l

<

>

0:::

w

1-:z:

::z::

l -c..

w o

0-19 20-39 40-59 60-79 80-99 100-119 120-139

0-19 20-39 40-59 60-79 80-99 100-119 120-139

GRIP

Night

lorvoe 7-10 doys old

o

2 4 6 8 10 12 14 16 18 NOS/M2 SURFACE

STOR HOLMEN

N ight

lorvoe 7-10 doys old

o 1

NOS/M2 SURFACE

SKLINNA

Night

lorvoe 7-10 doys old

o J 4 5

NOS/M2 SURFACE

FIG. 17. Vertical distribution of larvae in stage le at the three stations during the day and the night.

~ St age 1 c

[ill Stoge le

[1 Sl age l c

:::::E

:z

...J

<

>

0::

LU 1-:z

:I: 1- o_

LU o

::=:

:z

...J

<

>

o::

LU 1-:z

:I: 1- o_

LU o

...J

<

>

0::

LU 1-:z

:I:

l -o_

LU o

0-19 20-39 40-59 60-79 80-99 100-119 120-139

o 20 40 60 80 100

NOS/1.12 SURFACE

STOR HOLMEN

Daylight

Lorvoe 12-23 doys old 0-19

20-39 40-59 60-79 80-99 100-119 120-139

o 20 40 60 80100120140160180 NOS/1.42 SURFACE

0-19

SKLINNA

Do yl ight

Larvoe 12-23 doys old

2 o-3 9 -,:;:;::'::;:,.: :,;:;.,

*'*~~-....

40-591~~~~~

60-79

i

80-99 100-119 120-139

o 3 4 5

NOS/t.l2 SURFACE

flli] Stage 2a

f:J

Stoge 2o

fl] Stage 2o

...J

<

>

o::

LU 1-:z

::IZ l -o_

LU o

...J

:;

o::

LU 1-:z

:I:

l - o_

LU o

::=:

::z:

-1

<C

>

o::

LU 1-:z

:I:

1-o_

LU o

0-19 20-39 40-59 60-79 80-99 100-119 120-139

0-19

o 50 100 150 200 250 300 350 400 450 NOS/1.12 SURFACE

STOR HOLMEN

Night

Lorvoe 12-23 doys old

20-39 ... .,,,,,,,,,,,,,, 40-59

60-79 80-99 100-119 120-139

0-19 20-39 40-59 60-79 80-99 100-119 120-139

o 20 40 60 80 100 120 140 160 NOS/1.12 SURFACE

SKLINNA

N ight

Larvae 12-23 doys old

o

10 15 20

NOS/1.12 SURFACE

FIG. 18. Vertical distribution of larvae in stage 2a at the three stations during the day and the night.

fli]

Stoge 2o

O

^{Stoge 2a}

LJ

^{Stoge 2o}

::e . ::z

:I:

l -a..

L.U o

:z

- l

<

>

c::t::

L.U 1-::z ::r::

l -a..

w o

- l

<

>

~ L.U t-

:z:

::r::

t-a..

L.U o

GRIP

Da yl ight

Lorvae 23-28 days old

0-191~~~~~

20-39 40-59 60-79 80-99 100-119 120-139

o

1 2 3

0-19 20-39 40-59 60-79 80-99 100-119 120-139

NOS/M2 SURFACE

STOR HOLMEN

Daylight

Lorvoe 23-28 doys old

o ^{4 6 8} 10 12 NOS/Id2 SURFACE

SKLINNA

Oaylight

Lorvoe 23-28 doys old O -19 ,~;·:;· :;•:;w; :•~:; :~::~::~

.~:·~: ::·: ... ^~.

2 o -3 9 -;~!;~: ~~~;

4

o -

5 9 -~::: ^:.•; :@;::; :~::~ :~::?

6

o-

7 9 ·::.~ ::·::·::·: ::::::::. :~::~

80-99 - 100-119- 120-139-

~---~,~---~,

o 1

NOS/M2 SURFACE

~ Stage 2b

!Ø] Stoge 2b

[§]

Stoge 2b

- l

<

>

~ LL.J t-:z:

:t: t-

a.. L.U

o

:z:

- l

<

>

~

L.U 1-:z:

:::t:

t-a..

LL.J

o

:z:

- l

<

>

~

L.U 1-:z:

:::t:

t-a..

L.U o

0-19 20-39 40-59 60-79 80-99 100-119 120-139

GRIP

Night

Lorvoe 23-28 days old

o

4 6 8 10 12 NOS/M2 SURFACE

STOR HOLMEN

Night

Lorvoe 23-28 doys old

0-19 ~~~~~~~

2·0 -39 40-59 60-79 80-99 100-119 120-139

0-19 20-39 40-59 60-79 80-99 100-119 120-139

o 5 10 15 20 NOS/M2 SURFACE

SKLINNA

Ni gh t

Lorvoe 23-28 doys old

o 2 3 4 5

NOS/M2 SURFACE

25

FIG.

19.

Vertical distribution of larvae in stage 2b at the three stations during the day and the night.

~ Stoge 2b

!Ø] Stoge 2b

!Ø] Stoge 2b

1000

1-

:c

^N=74

(!J ₈₀₀

w s

₆₀₀

>-

a: o

₄₀₀

200

o

8 1 o 1 2 1 4 1 6 1 8

STANDARD LENGTH (MM)

Fig.20. The standard length/ dry weight plot of the larvae not exposed to formalin fixation.

<3

::.l

-

l-I (!J

s w

>-

0:

o

1500

1000

500

y= 22,2676 * 1 OA(0,0827x) R = 0,88 N=1495

O+-~~~~~~~~~~~~~

5 10 15 20

ST AND ARD LENGTH (MM)

Fig.21. Length/dry weight plot of the total formalin preserved material sampled in

1987.

-

(!) ::l 700

-

^{y = 25,9225 *} 1 QA(0,0757x) R = 0,85 m

1- 600 N=1140 m

:c

(!) ₅₀₀

w $

⁴⁰⁰

>-

^I!J

a:

³⁰⁰

o

200

·100

o

6 8 1

o

^{1 2 14 1 6 1 8}

STANDARD LENGTH (MM)

Fig.2 2.Length/dry weight plot of the larvae sampled on the first coverage. ·

-

(!) 1500

-

::l l-I

o w

$

¹⁰⁰⁰

>-

c: o

500

y= 17,7563 * 1 OA(0,0932x) R ^{= 0,93}

N=360

m

0+-~~--~~~~--~----~---~---

5 ¹

o

^{15 20}

STANDARD LENGTH (MM)

Fig.23. Length dry weight plot of the larvae sampled on the second coverage.

o

N D A F

c

T

o

R

o

K D N A F T c

o

R

2

•

o

8 1

o

^{1 2 14} 1 6 1 8

ST LENGTH (MM)

"

Fig.24. Length versus condition of the larvae sampled on the first coverage.

3~---~

• . .. ..

2

• • • • ••

•

04---~~----~---~---P---+---~

8 1 o 12 14 16 ' 1 8 20

ST LENGTH (MM)

Fig.25. Length versus condition of the larvae sampled on the second coverage.