..

}:.) ....

TIlE GATG'H PBR::mH' OF EFFOnT OF T):UD DUTGR DRIF'fUE'fl"ISl1UJJ.IES DIFFElmN'TRIWIONS OF TEE NOHTH SLA IN TEE. l'KRIOD 1947 1955,

by J .J .,UJL8TRA :;::.;;:;;:;;::;;:;;:;::;;::.:;::~'-='::::

III ordor to contributo to tho discussion of thG Spocin.l Uoo"ting 9

tlh,l' horrill{; cf th0' southeT.ll Nor-th SOtl 9 tho detn ,;J,vnilüblG of tho jJcatch of' offort:1 01' tho Duteh driftrh:d:; fishorios ,:o,rG :prQducocl hora,

1,11 .1953 'HEtvinga shGwed d~1tG nbout thü Dutch driftl1ct fishorios ') ·cY..Cl,tn Ctbout tho herri11.g tr,-::v::l fiBho:L"Y_ Ro cOllsiclorod t110 \~uüstiol'l whOtJ1G1." ovz::rrfishirig' COUlcL be c1otect8d, end c<.'~me to tho conclusion tho.t this wns· ]\or tho c1riftl1ot fishori0s hG 8ho'll70d tho WGetn c2:'Gch per shot i:l lIkant"jbs H

yonr nnd month sopi.:',rc,tely il1 tho püriod 1947-1952.

In thiE:! paper elßo tho ciJtch lJor uni t of (jf:2ort 18 pcr shot in Hkal1tjes 1l 9 in which Q l1k,::,ntje i1 roprusonts r1bout 90-93 kgf3/1 Ho ßV;:l,ilo,blo to trr.';l1sform this volumc ln0E1.8Uro in t'orms of numbors of fishos (lid (1956). S'uch g tr'nllsform,:;.tion \vould hEve giVf)U [1, bottGT 8,'::ltÜ;:ti:::te of II~"vil1gG US8C1 fol" his CQlcul~;/ciol1s the E1.VGrag8 d,nta givon ill thu heI'J:oil1g whicll ho,vü "bO<.-fll publishuc1. in the ill\.nnulcs BiologiquGs!1., ThG fig'ures givo1:1 }1,;:per h8.V8 bocm cc-lculc,tGd from tho ,?"ctunl c:ltches 110r nig'ht n.l1('~

accurnto ostim~::tel:;; might bo o,Xpootocl <>

Furth'ermore 9 the dr:!.tc \11.lerü o0l1sid0red für dj.ffere,nt rGg'iouf.t t;1l1cl periods " .t:l,-~,,~(J:+'\;

,this moetinG is intürGstod prtrticul[~rly in thc herring of thG' 8ol1thern Nort 'wo thOU[)1"0 i t "~ .. tQrth,Yhilo to sho'\i",1 <:Ü30 dc:.tc für other rGsiQ1l.s 0 The following ,i\!o!'ü consid.ciX'O(t ';

a. Tho Gh'}~,1181 Iishory (s01\th ol 510 n.L.) i.n November anel December. -------------,.,--------~""-....,,~-~'--------- . ...--,,_._------_.'-- -,~"--_.-

This fishory toJ:QS place f'x'om th\~ midcllo of Nov8raber till t110 end of hO'rl'inc c(i';nght i8 ill2.inly fUll, spi;1S,rnll'l@; Ctl1cl ~;111G!lt iish. Tho fil::ihory i8 U)t' irnpörtf~trt 011G

TABLE 1 Year ----1947 194:3 12.42. 1950 1951 1952 125.1. 1954

35 30 34 54 43 73 38

This fi21hory'J occLtrring bOtWOl;l:' Octol)0X' nnc:l th8 middlü of DGcombory i8 tho most irilports1:lt Duteh driftl1et fishi:.rios 11 ThG horriuG is rae;i~l.ly in

''''iJGnt condi tions. TADLE 2 ._._--Year

1947 1948 1949 1950 1951 1952 1952- 1954 OctobGr 71 74 43 113 69 100 49 120 Novombor 03 70 77 57 57 59 61 65 DOCOClbor 34 12 23 27 36 19 54 13 pOl'iocl Oc"tobor·-Dooombor 68 66 64 78 58 77 55 90

,.

c. CCl1trol North S8ß fishcry A(betwc.:Jl1j3°30' N.1. OI1~O 11.1.) Augu«t-Ootober.

In ",chis region spD;w.l1i~e. trl.kcs .{Jlo,?o in S~pt8mb8r .... Oct.? b~r9 O~l (1.1 if~0. rel1t,.l~;ro~nds, (Wh~tby~ ])oggor, Borvnck-eo2ost). Ho OOl:lBlClorod the flsnory :111 thu; rog~ol:l ll1 tho periOd from August till Oetober. 1'his might givo 20 picturc of thc abul:ldal1eo of th8 spnwning stocks in tho nrci(',? al though i.:1 mi.x.ing wi th stocks:; sp8.1vl1il1b' olsGwhoro 9 is boul:lo. to ooeur.

TAB1E 2-YOGI'

1947 1948 1949 19512 1951 1952 1953 1954 1955 ~

Augus:t 21 39 18 23 21 21 29 31 21

Septembor 47 48 31 34 36 38 33 30 25 Octobor 70 35 33 41 33 76 23 74 41 pcrioe,1. August-Odober 49 42 27 30 30 35 30 31 29

cl. Centro.l North Soo. B (betwO(;)l1 .55_° N ,,~_o ___ - 57° lTq~oJ r,lqy ____ -:~ Soptomber"

ThG summor fiEjho::-ey in th.Q Contrr.:l Horth Sea 18 roprusontocl by thiti t,--:blo Q Tho period from U8,Y till tho ond of 8optumbor is considorod 0 Thü i;1r8C i8 mcdnly i:1 :f'ooG.ing ground in tb.o poriod conBidul'dcl:; 0.1 though BOli10 Spcl.1.i\/ning mny acour in August ::\nd Septombor,

ff1ABLE 4

Yoar

1947 1948 1949 1950 1951 1952 1953 1'2)4 1955 May 13 17 14 8 2 8 Jun8 36 17 6 8 17 13 27 15 34 July 23 27 14 17 21 33 36 30 31 Au{~u$t 9" '"oL 37 1[l 27 2~? 23 32 41 23 Süptombor 45 59 30 36 41 40 30 34 31 pe ri od ]lny-Soptombor 34 33 18 24 24 28 32 27 2S

o. N~hern North 80'8 (north C;f )7° N "L_,,) I'l.sy ..... ~Gpt8mbGr.:'. Dato, o.bout tho summor fishcry in tho J'101'1.nern North SeLl. 2,1"0 givun her~}9 für 'thü po-riod N[~y till tho üncl of ~)GJ?tümbGr .. f-Phis :fishE:-lry too i8 lnc:.inly Q. fi811.ory for fcoding herrill[j9 ",,1 though Homu ßp;;Jlin'üng- to.kGS pl~,ce in August <lud Soptr,.nl1bor"

1947 1,.Ic.~y

Jul10 36

/July 33

August 43

Sopt0mbor 68

}io:riod l:~GY­Soptü mb8r" 37

1948 1949 15 16

14 11

31 12

19 19

16 12

TABLE .'2 Yoo.~

1950 1951

11

10 16

27 21

15 16

18 16

1952 lJ5~ 1954 1955 21 17 19 26 19 10 45

31 25 14 41 26 68 64 59

68 20 54

27 39 17 48

..

':f'~" 'Jr)tf;tl',-:N'orth ~'Öa -'STIel. ßngli~1-11 Cht1unel ~

F:i..nally t11o. m02.n o"tch p~r unH of ()ff'ort oftho DU"\;Ch loggors? "ü fh.Clr;t:k>;'ii<,·,,>':''? n'ets is ,gj;VOll , for tho wholB North So;;; fi.ßhüry"

TABLE 6 Year

1947 1948 1942 1950 1951 1952 1953 1954

48 41 29 41 38 45 41 47

In order to '088 whother tho English 2nd Dntch do,tD.. c.bout th0 E;::tst-Al'lGTi,!~1!1 corref:'Jpol1d:t a compo.rison WQ8 m8.do q .A difficulty iß met herG)! beoattl.Jo Gur dg'i;'fi dre'<'·""??,,, o:x.prozsocl in thG c<:ltch por shot in "k.;:tntjos11 9 whL! .. o in most of tho English' ' tho u'l1.mbcrs of her:ring pur lC~l1dil1g- ,:trc; oonsidered. Only f:eom t,\blo 2 of 13urd pnper (Pn.rt.JII 9 !1Changc~s ßscribod to fishine l1 ) the moall cG1tch per InlJ.ding' irr.: crans f~or -eho ~-,/hol0 E[1J.~t ..... Anglinn rishery mo.y be cr:ücula"t;ed ~ Compnring thQIfe tho- Duteh datu? wo g\)t ,;

Year

r:[lhose two ,sotfJ of dD,tC!' show? üXCGpt thü low cntehos in :l9,[55~ relatively ngroGl1lont" The Dutch do.tn d.i:2iplay an incrensing variabili ty 'I- To evaluo.te co,tchO,'.;l show signs of dOCr(;i2SQ or incrons0p 0. compnrison WC'!,~l mado für thG' perl' 1941--195° ;:md 1951-1955, for both i'ish0l'los. We find that tho mean ctltches per If.~.ndil1g for tho English 1:-'ishory were 48 ~,;md 40 crnns 9 respcctivoly? iNhich menus decr8nse of 16,5%, fol' tho Dutch fiBhc;ry the data wero 69 aurI 64. kantjes, rneaus 8. clecre[~so of 7'{0" Thus tho docro[,~s6 in tho English fishory is moro than in th0' Dutch fishery, For both th0 El1ßlish (md Dutch ontohes tho decreaso the poriod 1951-1955 compared wHh 1947-1955 i8 m"il11y due to t110 bad rosults 1955 ~

The English anel Dutch dntrt ll.greo on the point that the NovGrnber cntehos n1'8 Shov,ling ß rE:ductioll rather th8.h 1;he October ct'.tches 1;1 Gompnring ;J,gein i:;110 1947-1950 o.nd 1951·-1955 we find fol' the Octohel' CGtchos of tho Jlutc11 fleet 2. lnemi on:tch POl' Elhot of 75 c\nd 78 k:\ntjes 9 X'0specti v01Y9 für tho November ca/eches ageinst 56 kc"nt.jes 1;1 Tho October cr:tches h;::rvo gone up [tf'tel' th0 vvar 9 thG ce.tchos are ~jlowly decX'c.l2.singO' The English f'igures'l ex}')ressEKl in numbers per unit 12,:hc1iuG' show n dGCrerLS8 for both October 'D.nd N-ovomber'] although c1uction in Novomber is much l!10ro sGrious thnn in Octobero

In gonoral wo mny say that tho Dutch do,t2. probnbly givü CI, lass pOßsimistio picturo of tho EE\st-AngUan fishory tlMn the English. T11is miglü 100 due td t11e f'1ct tha'0 tho English ,ccud Dutc11 herring boats wOl'k pE\rtly in differont areas.>

Wo mndo the comparisol1 betwoc,n t110 two periods 1947-1950 E\nd 1951·.1955 also für the other fishorio8 ~ Thü following t2,blo gives L1 pio"Gure of this

1947-1950

COl1tral North SOEo A (August-Soptombor)

Contrn.l lTorth SO[\ B (May-Sept8mber)

37

27 Northern Nort11 Sea (May-[)eptember) 21

Tot,ll North Son 40

J("ntjos pOl.' shot

'rh01.English 0112.111101 1s left out bece.uso tho l1umbor$ of shots 2.l.'k) gonor,dly

31

..

- 4 -

'1'ho toto,l Dutch driftnet fishery shows 8, small ri8e in the meO,l1 c2tch per shot in "kcmtjos" in -cho pGriod of 1947-1955, '1'his ris0 808m3 -Co b0 Quoto 1) ri80 in tho, c8.tches in -eho SUn1ill8'r fishorios .. Hoth thes-c} fishoriGs show DJ'l iucro8,se in thü c8.tchos 9 but OSlJDcit'.lly the catchoß l10rth of 57° N "L" increasod. Tho ]inr:r'c~Angli;J,tl fishol"Y 2.nd tho Contrnl North Süc\ B fi~ih8ry shOWGd G dücrGn.so .. This decrCD,se V/;3,8 of specio.l importz~nco on tlle ßPi..l'vvl1irig e;rounds of tho Ce:ntr~11 Nor-bh Süß? c:::tchOf:;! goin!)' elow11 by 16% oomporoQ wHh 7% in ßast-Anglia.

Al i110Ugh eX[1ct data nre missing~ \VO hC.V8 r02~Bons to believo the sunlil1er ..... cLriftnet fi,sherios to 00 conoorllod m<-~i:nly 1ui th rr;.ther young herril'lg. In, the fishetiQs :for }spo.wning herrillß' i3.-l1Q hGrring 011 thoir wny to thG spa1~'irning e;rounds both young and olcror herril1g nr0 CGught. If this i~1 true 1 the dp"ta shown o.bovo ;Noul(~ inc.icnte that, thero Cl,rQ more young ",nd los S oldor ller:ring' in tho poriod froni 195t-1955 thaJ.~ in tho pGrioe: of' 1947-1950. ThiD ,,'grOGS v1i th -che fact th!'\t thü Odobür catohes on ,'tho' E.::S-t .... J1l1g1iCln fishury incronsed C>.nd the Novembor cc~tchos docrc;J.sod? bGC,;1USO we kl1ditY from :8~ngliE;lh inv8stigc1tions that the Octob,n' herrin@,' is ffietinly you.:ng horringjl v;rhorelis in Novombor C'D.ught horring tho alder' indivic1ualfJ plny ;;: more import;?,nt part.

Howover, in thG August-fishery north of 57° N .'L., whieh probr"bly pnrtly includ."" 0, fisher;y 'for sp2\'n:1int;~- h8rring~ cc.tches hf~V() incroL"].socl i11 tho pcriocl cf 1~)47-1955 (SOG tnblo 5) 0 Similnr fishorios in thD c011tr21 and Routhern North SO<1 fJhowod n decreaso in the mGfLn CCttch per shot 0 Thorefore'1 diff'orencos in thu sizGS of tho clifforont sp;·:"rwning stocks might 0,180 be involvod in the dif'feront courSG of thc monn catch POl' shot in tho l1orthorn nlld. southern North Scn in the period. from 1947-1955 •

• "