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This paper not to be cited without prior reference to the author ---~---~ ---

International Council for the Zxploration of the Sea

S1.T1POSTUH OI:J

lI'l'he Biology of :iI:arly'Stage;s and.

Recrui tnent J:.lechfu""1isDs of HerrinG!' Ho.

5

The :food of herring larvae of Hor~'lOgian SPl.~iIlg spavmars

By

Herman Bj0rkc

Insti tuto of liarine Resea.rch, 3ergen, Nor'oJay

INTRODUCTION

To study the relationship bet,·reel1. gut content of hor:ring and the zoopllli'1ldon co:opo::>i tion, an invGstigation "1;.7<:::'5 carried out in a locality off HorG in spring

1967.

The l:.lateriQl was collected during the period

4 -

10 April, aroillld a current cross placed in a larval consentration (drift station 1 in Dragesund and Nald::en

1968).

Oblique hauls vlere taken at noon and nid..."1.ight "I'li th

3

Clarke-Bur:lpuS plankton samplers equipped ,'d th nets of nylon, Besh siZe

90

j-A • Tne total to'tving tine ",as :f'i ve ninutes lli"J.d the sanplers .. ,ere raiseG. in

5

^r..1 steps each minute. Aftor the outburst of phyto- plaP.2->:ton, the duration of tho total to'wing tiDe 'Has reduced to one :oinute to prevent clogging. The sanpling depths wore

25-5

D,

50-30

^{L.1 m"ld}

75-55

^1:1 aJ."ld the to'wing speed .'.ras

1.5 -

2 knots.

The sanples 'verG each divided into hundrGd suo-s['":oples "V-ri th The

~rnirling Uessel (1Hborg

1951)

nnd tvro of these sn.nples "lOre counted.

The sizes of the larvae a.:..'"ld the yolk wore L1easured.. Dissection of a randoL1ly saople of 100 larvae, showed that the gut content

2

o'ould be detected as external bulges by superficial exaninati9-R;'"

RESULTS AND DISCUSSION

The zooplar.J.<:ton 'was evidently densCl:' in the upper

25

^P

than in the lo"'"mr depths ~ Also a heavy incrc2..scr.-:" in copepod eggs were recorded at the end of the sunpling period. The copepods:

and the copepodites distributed nore evenly tlu~ough the lolhole sanpling depth, but also for these organisDs a snall increase could be traced for the upper haul. Calanus finc.2.rchicus-eggs consti tuted about

90

9~ of the copepod eggs, and C. finnarchic;us:'

" ¥

nauplii about 80

%

of all copepod nauplii. Of the other speci9~

Oithona sioilis was Do~t frequent.

Of

440

larvae exaoined

223,

or 5l

%

contained food par- ticles. Of the larvae caught in daylight,

76 %

had gut content, in contrast to

32 %

of the larvao caught at night. Thus the fee,- ding activity vms redused by night.

Tlw lc:.rvao ";vere sepera ted in four groups depending

on the size of the yolk sac (Table

2).

Larvae at the begir~Ling of the yolk sac stage occurred less frequently \nth gut content than larvae at later stages. This indicates that the larvaes need for food or its feeding ability increased at an age of three to four days after hatching.'

The gut content Has divided in four groups, and of the

total nurdber of food particles Calanus finnarchicus-eggs constituted

I. cl

9''r h

o.

f~RRArchicus-nauplii

3 %,

copepodi tes CU'ld adults of I/;:icro- se.tella nprV'eg.i,c.a

1 %

and others

2 %.

In numbers, eggs of Cope]:?ods constituted

63 %

ⁱⁿ the plmlicton sanples, copepoc-n~uplii

25 %

and Hicrosetella spp. 7

% •

Due the f'oUi"1.d differGl'lces in the eoo- posi tion bet,veen avai.lable planldon and gut content i t is assm:led tnat the larvae selected Calanus-eggs,either because of preference, or because eggs were easier to catch. Bmvers and 1:filliaoson

(1951)

stressed the inportance of copepods at all st~ges as food for larval. But, although copepods in our sanples constituted

43 %

of the plankton s8.I:1ples, they only represented

3 %

^{of the}

gut content. Soleiw

(1942)

found that eggs at Cal~~us constituted the only food of lli"1.ioal origin in herring larvae, but r~s naterial was rather scarce; Byside the eggs he found green food reoains in the guts. Exsept for one Cosinodiscus sp., no green food reT oains wore observed in the present :;':'laterial.

Ho correlation was found bet"veel1. the nU1:J.ber of copepod-

eggs present in the daylight hauls and the nunber of eggs in the guts (Table

4).

The percentage of larvae of larvao containing food (51

%),

is relatively pigh coopared ~dth other findings;

Bowers and Willianson (1951), found a percentage of 28. I t is therefore roasonable to aSSUIlO that larval food was ablll~dant

during the period of our investigation.

SU}:lliARY

1. Tho 5~t content of herring larvae in plankton samples taken aroUJ.~d - a current cross located in a larval-concentration Has exnoinecl.

2~ Calanus fil~larchicus-eggs constituted in nuobers

93 %

of the particles in the gut content.

3. No correlation was fOlL~d between the nuober of eggs in the saoples and nur~bGr of eggs in the ~~ts.

4.

I t is assUDed thG.t larval food 1'JD..S abundant during the period of investigation.

l1~F~R:2::NCES

Bmvers, A. B., and Uillinnson, D. I.' 1951. Food of 12.rval and early post-larval stages o.f autur.m spawn,ed herring in Hanx waters. Rop. _{- - - - -}nar. bioI. State PtErin

6'i,

...;;,...:.

17 - 26.

Dragosunel, 0., and lb1:J~en, 0., 1968. I'~ortali ty - of herring eluring the'larval stage. ~. Heet~ Int.

2..2.:!:E.

^2xplor.

Sea, 1968 (L~).

Soleiw, p. li., 19L.l-2. Arsaker t i l ri1:;:.e og fattige argal1.ger av sild. FiskDir.~. Ser. HavUnders.,

7(2):

1-39.

1Jiborg, K.

F.,

1951. The whirling vessel. An apparatus for the fractioning of plankton sD..nples. Ibiel

2(13):

1-16.

rab1e 1. Density of' zoop1ankton. Sar.1p1ing depth Sta tion nur:1ber 2a 30 4a 5 6 7 8 9 10 11 12 Total

-

Copepod eggs 2199 889 495 857 3664 12113 tI.1004 11904 17338 29333 14386 104182 Copepod naup1ii 791 2330 388 1011 428 4262 5676 3009 3773 3435 5498 30601 Copepodites and 2.5-5 n adults 430 128 35 608 110 176 1074 83.5 1752 1487 1867 8502 Miorosete11a spp.' 11 13 13 102

-

393 174 134 46 358

-

124l~ Oth.ers .. 11 13 122 69 163 873 89 281 830 549 3050 spp.

- -

/' Cope pod eggG 1192 994 2579 2957 1549 1977 1543 1214 2257 1167 17429 Copopod naup1ij 1683 1183 1308 2834 1250 1322 876 1587 963 2077 15038 Copopodites fu'Ld 50-30 i:l adults 603 293 7L~9 473 289 463 544 592 490 511 5007 Hiorosete11a spp. 23 138 25 219

-

386 104 159 48 128 1230 Others spp. 46 50 150 68 30 124 83 63 280 299 1193

-

Copepod eggs 544 2201 1185 175L~ 2284 7968 Copepoc1 nauplij 278 1650 251 2383 870 5432 75-55 t:1 Copepodites anc adults 194 349 244 1118 141 2046 Ivlicrosete11a spp.

-

14 2

-

19 35 Others spp.'

- -

4 52 96 152

Table 2. lTul':lbor of' horring 1arvao in dif'f'oront yolk sac stages during tho inv0stigntion

perio(~. Nur:!~er 0:1:'

1ar'vaes 1vith fooe: in tho ,::'clt';,

"

in brackets. Daylight hauls ovon otation l1.uI:1bers, night hauls

{.!:LI . .'::;",en

nunbers. ---.--- ---._---- Station nunbero

~

2a 2b 3b 3c 4a 4b 6 7

8

9

10 11 12

Total --- Depths of' sa::1p1ill.g 2.5-0 2.5-0 2.5-0 25··0 25-0 75-0 25-0 75-0 75-0 50-0 75-0 7.5-0 50-0 50-0 50-0 50-0

1'li

thout yoll: sac 1 4(4) 4(4) .5 10(3) 27(8) 21(1.5)26(23)3 1 (11)16(15)10(5) 4(3) 3(1) 1(1) 4(1) 3(1) 170(95) Gna11 yolk oac 3 6(6) 7(5) 10(3) 28(6) 11(9) 17(12)27(11)18(17)10(5) 1 6(1) 2(1) 146(76) Hediun yolk sac 4(4) 4(2) 1(1) 5(1) 20(6) 2(2) 4(/+)

10(7) 2(2~

4 4(2) 9(5) 3(2) 1 73(38) Large yolk sac 3(1) 1 1 8 2(2) 2(2)

L~

(3) 3 4(1) 3 8(1) 6(1) 6(3) - 51(14) ---- Total 8(4)17(13)12(10)21(4) 11(3)

83(20~36{28)49(41)72(32)39(34)28(11)12(5)20(7)10(4)16(5)

6(2) 440(223)

s

I i tation nunber 1 20.

-

ar..lpling dopth 25-0 25"';0

.Q, o

H

o

^alo.nua

eggo

I

alanus nauplH

I

iQJ::Q_gLt~IL<?-app , thors spp.

---

I "

.5

1

-

I x:Vnidentified rel:1ail1.s

y:

Oosinodiscus sp.

37 1

-

z: Eggs of O~thona 8iuili3 '..:'ublE

3.

lIunbers bf different food particles in the guts of the sanpled herring larvae. I

,

4£1. 2b

.3~3b

3c

4h

5

6

7 8 9

-;;~o

25-0 25-0 75-0 25-0 ~5-0 75-0 50-0 ~5-0 75-0 50-0

26 16

r' ::> 35 53 106 43 140 30 .1L~ 32

- - - - - - - .5 -

10

- - - -

1

-

2 4 2

- - -

2z·

i 1"<' 4"', ly 3-r

I

I

-'~ J>' .L~ 1 I i b

... 10 11 12

-I

':;0-0 50-0 50-0 Total

%

13 13 2 570 94

- -

1 18 3

- - -

8 1 11 2 !

Nunber of larvae caughtt (in brackets

1arvao with gut content), nuo.ber of Cal2.!lus filLOarchicus-egGs pr larvac, &~C nunber per 1arvac of Ca1auus firzmrchicus-eggs found in

the gut.

Sanp1ing! Station numbcri 2a 4b

I ⁶

^{1 8}

I

¹⁰

depths

L ____ ^~_ 1 ^{L _~_}

^L_

^{J __ t~} ____

^{1 12}

r-~

--- ---: ^{i ---}

't-~;--~--I-· ---~I

i Humber of

larvae 17(13) 27(24) 9(7)

1(1)

5(8) 2(1) Calnnus fin-

25-5 ^r..:l Llarch~cus eggs

per larvae 550 70 2400 12600 3700 5600 Hunbors per

1arvc!.c of

3.00

I

^9.00

Ca1nnus-eggs 2.17 2.25

I

^{2.l.W 1.00}

found in Jche

I

^{1 f}

t gt..-1ts

I I _J

I

I I

^{i I}

Hunbor of

115(14~ 30(27/ 6(11)

1

5(1)

In-rvnc

-

^LJ.(l)

Calo.nus

fl£-

f

^{250 350}

I

^{1400 I 1150}

:c.1archicus-cgg~

-

¹³⁵⁰

50-30 :n per 1arvo.c

I

^I

Nunbers per larvae of

Calanus-eggs

-

^{2.67 3~78 0.83 0.20 0.00}

founel in the

guts t

1 I

NUDber of 7(3) 5(0)

I

1arvo.e

-

^I

I

I

ICa..1anus ~-

,

I

75-55 ^hI :t:tarchicus-eggs

-

¹¹⁰⁰

1

9700

per larvae Nunbors per

larvae of ^I

Co..llli"Lus-eggs

-

0.57 0.00 ^{I I I} fOUJ."1.d i..""'1. the

I

^I

,guts _{I ! ,}

I

_;