,nit"r'llaL'onal Council for theXl lyc.t.l011 of the Sea

C.M.lnSJ/L:37

Biological Oceanograph.v .ornrn i. tot

PLAllKTON SHEETS - EDlTOR'S REPORT 1978-79

This year the report is disappointing as no new sheets have been issued,

no,' indeed have been received by the editor for his attention. Suggest­

ions re ceived by the editor as a resul t of his request in l.;..st year's

report have been acted on as yet without new promises.

1'ht authors whose promises for sheets are still outstanding have again

bee/' sent reminders and a few now given up as hopeless have had their

promises cancelled and attempts are being made to j'ind replacement authors.

Or.ce a.~in ar'ly:t1 ~s < OflS from members of the committee or others would

be ver;,' gratefully re.:eived, and appreciation is expressed for those

already received.

•t is nevertheless h

'llowing session•

d . that further progress will be made during the

•Editor

:..

•

•

In April, Icnßth-frequency modes \'lere distinguishcd at 18-19, 22, 24-26 nnd 28-30cr.l(~nlc~) und 18, 22-24, 26-27 and 29-33cm (fcoale~). Reference to lenßth~at-acednta (Table 3) indicated thnt th()~ corrcspondcd to fish'1, 2, 3-4 and 6-7 y'carsold respoctively. In Hay, modes \.,rore distinljUishcd at simiIar lengths: 19, 22-24and 27-33cr.:l (males) and 19, 23-21• und 33-36cm (females). Dlue \'lllitinß four tosix ycars old' (those around thc mean aGo of recruitment; Bailey~ 1978) werepredocinant'in the April catches (FißUre 8), comprising 44% of a11 males and50% of all fer.m.les. Five-year-old fish cons~ituted the most frequent. class(26.4% overall), being proportionallY'rnore abundant than at any time since 1970,and the relative numbers of youncer fish (32.4%) were hißher in the 1979 samplesthan in those of every other year from 1967 (cf Dailey, 1978, Figure 2). Thc 'percentaco of young fish was even hicher in thc Mny bottom-trawled material~specially frOl:1 Rocl:alL. AlthouCh it i5 incrcaainc, it seeos wilikely thatthe recent level of fishin~ effort hao sicnificantly raised the total:mortalityrate on older blue whitinß, so that theseresulto, together with those from theprevious year (Valsh et al., 1978),'indicate that the 1973 and 1974 year classes\mre comparativcly strancand may be followcd by further stroncr clasoes asoyct'only partially recruited~ . ,

• I • ~

Sex ratio. Tbc aex ratio of blue whiting from research surveys' \o18.S rather le:::svariable from haul to haul in May than in April (Table 4). The mean percentage'and ~tandnrd deviation of male fish was 39.9 +12.9 in the first monthand51. 1• +, 6~6 in tho second, the highest percentäe;e beine; 63.2,· in the 'Uaycommercial sampIe. This last result is slie;htly unexpocted in that the lurgercOr.m1ercial cesh cie;ht be e:>''Pccted to cxert a bias in favour of thc ·bieger fenales.~le data ecncrally aCl'ec with previous findincs, includincr thooe in 1977 and 1978,that in the area \lest of thc IIebridos the propcr'tion of males tcnds to rise M '

tho year procresses, but the relative level of males was lower in 1979 thnn theyeurs before (cf 52-55~6 in April-l1ay; Richards, 1977; and 50-69% in April;\-lalsh ~!:!.., 1978).

11aturity. Owing to thc poor condition of frozen sample'material, data on thematuration staces 0 f bluo.wh!ting' \lere 0 btained only fron fish tuken durine theApril survey. At that time an averaGo 95.6~$ of calos and 85.9~6 of females \lereeither ripe and runnincr or elso apent (Table 4). There \-lere proportionally r.loreapent" males (81%) than femalea (61%), and because of thcir lonGer maturationperiod (Polonoki,i, 1966), more immature fenales (12~~) than males (4~n. Althouc;hthis pattern is broadly similar to that in April 1978, at that tir.:le there wererclativcly fe\ler inoature fish and more spento (89.7;$ of males and 30.25$ offemoJ.co; \loJ.sh 2! Q., 1978). Tbe southerly mieration on to the spa\minc; crroundsthus appears to have occurrcd rather later in 1979.

lfenn \leicht and condition. In April, 'meun weiahto \lere 73.8-103.9c for Maleblue \lhiting und 117.1-152.8g for .fenales, "hilc in Uay they were noticeably10\ofCr, in accordanco \ri.th the 10\lCr maan lenGth: 45.3-83.3e (male) and43.8-83.5 (female). Th1s reprencnts an averaGe di5fcrcnce in weiGht of about115~ (Table 4). The mean condition factor (100 ''l/L ) was very similar in thet\JO months (0.461-0. 1.63) and corrosponds to prcvious asscsomcnts made at thistime of year (O.4~0.47; Richards, 1977; 'lalsh et al., 1978). Condition wasconsistently hic;her in malen in April but higher In fCmalcs in Hay, suce;cstingthat·the post-spawninc:; recovery may proceed l.1ore rnpidly in male fish.

Diocuosion--:.;:.;.;.==~o the whole of thc period for whi'ch April blue whi tinC opa\mint; stocl~

estimates ure available (1973 on\ßrd:::), those made in 1979 were above.md am:3C:JOrJents r.tade at Faroe in February und on the spa\min(; E;roundsthc 'Jeur were hisher than those Of 1978 by factors' of c 2.2 and 2.8

5

rcopectivcly. Chaneen in thc ac;e C01::lpoGition of thc population over the past two... yco.rs nUGfsest that recent !Stroue yenr clasoeo are no\'1 recruitinc to thc spa\lnin:; •

stocl= and probably contributinf) to Hs increaseo. oe:.':mndance. Further cvidencofor compnratively hieh interwity npawninc in 1979 may bo provided by thc ununuallylarc;c llumbers of blue \lllitinc; eßCs collected b:t thc Continuous Plankton Recorderdurine thc April survey (Coo~bs, pers. corMl.). The relative numbcru of aC6s undlarvae alno indicated,that the centra of spa\min~ activity was ooving north durineApril (Coombs, pers. comm.) , these conclusions aCTeeinG with the incrcascd.bluc\1hitinc; densities recorded no:::-th of 58°30 'N tO';JOrds thc end of the cruise. ,

•

,

Acouotic cstim~tes of tho size of thc bIlle \~hitinG s!><:\\minß ntoclv1ifrected bysevcral factors, Dlont notably a:::wunptions about the correct tarcet strenethnnd the proportionality of scatterinc cross-section and weicht, tarcet idcnti­fication, ,variations in the timing of fish maturation and micration, thc c~n­

fir.;uro.tion of the 'survey Crid, the time and area coverac;e of a survey and finallYthc method of analysis of thc accUIllulated density data. This paper is mostconcerned vith the last two points end particularly the latter. Tlw most '6rca.listic estimate of the spawninc biOI:'laas in 1979 was taken to be 23.5 x 10 ,t,calculo.ted using 0. contourinc nethod. Althouc;h rectenGular enalysia a.nd eon­tourine roay cive roasonobly clono rcsults, the advantaGes in presenting an arrQYof sinplc arithmctic mean dcnrdtics in each roctan{:;le as weIl as a contourdiar.;rnr.t lie in ita creater atatiotical uoefulneos end in thc proviflion of acor.lparativc estimate, especially in situations li/here eontouring is diffieult.

Evidonee sugecsts that sinec the t~tal distributional area of the blue whitingsIx.nmin6 stock (roughly 309 000 bn; Buzcta and Nal:J.en, 1975) is considorablycreater than that of the averace Clurvcy, then quoted'estinates of absoluteab'lUldanco are likely to be correopondinGly 10\1.

TIeferences

•

BaHey, R.S.

BniIey, R.S.

BuHe:r, TI.S~

1970

1972

1970

Are-interpretation of ace determination in thcblue tlhi tinr:; HicrolJCsistius poutassou. lCES GM 1970/F:31, pp 5, miueo.

Scottish investieations Oll blue li/hitinc at Rockall.lCES CH 1972/H:33, pp 6, mimeo.

Chances in thc aGc'composition of blue \mitincin thc epawnin~ area llest of Scotland 1967-1970.lCES CU 1978/H:52, pp 6, mimeo ..

Duzeta, R.,und Naklwn, O.

Forbes, S.T.,Pa\1~:lOn, H.G.,Riehards, J. andCushinc, D.H.

HOr\100cl, J. \1.

1975 Abundence estimates of the spalming ntock of blue\/hitine (HicrOl;wsistius poutassou (Risao, 1810»

, in the area lIest of the British lsles in 1972-711.Fisk Dir. SJn-. Sero IIavUnders., 1§., 24,5-257.

1974 The Llue 1I1hitin~ surve;yn by FRV 'Scotia' andRV 'Ciroluna '. lCES CU 1974/11:44, pp 9, mimco.

1976 The spatial distribution of the blue \~hitine(Hicromesistiua )outassou) by power apectralanalysis. lC~ eIl 197 , :13, pp 3, mimeo.

6

Jones, R.

Pnt/Son, H.G.,Forbes, [JoT. andRichards, J.

197~

The analysis of traw. haul statistics \Tithparticular reference to the cstimation ofsurvival rates. Rapp. P.-v. Reun. Cons. Per.,.int. Explor. Her. ~: 30-39.

TIesuIts of the 1975 acoustic surveys of bluewhiting to 'the \!est of ß_ . taino lCES CH 1975/H: 5, pp 5, mimco.

Pat'/son, HoGo,Blanch%40wer, SoE.,Fol'b f4. S. '1'. andRicha l"l18, J.

1976 Prel~linary results of the 1976Scottish blue ..:hitinC surveys.H:15, pp 4, mimco.

EngIiah andlCES GM 1976/

Polon..ikii, AoS o

• Jicl:cr, \! 0 E.

Sahrhace, D.and Schone, R.

Walsl, H.,Forb~s, SoTo andHutc',eun, JoRo

•

1~?'7

-'975

1975

1978

[Bouta580U of the Porcupine Banl). Ryb.Khoz., 1966, 2, 5-9.

Pl'climinary results of the 1977 blue ~1itinG

surveJ"s to thc west of Scot~·.and. lCES GM 1977/H:33, pp 4, mi@eo.

Co~putation and interpretati)n of biolOßicalstatistics of fish populatioöts. Bull. FishRes. Bd Canada 191, pp 382.

Preliminary results of German investi0ationson blue \!hi tint (Micromesi~ti~~poutassou) •lCES CH 1975!H:28, pp 10, mime.\.

Results of Scottish blue "lhiti~; surveys westof Scotland and at Faroe in 197t'. leES eH 1978/H:51, pp 5, mimeo •

7

'nable 1 1979 8cottieh acouetic estimatee of blue wh!ting abundance (tonne. x 10-6)

8urv~ KE'mOD OF ANALYSISDates arOIL Rectansular t - Contouri.n& I

AM aUlldj AM AM. . GM~

"eb P2-22 Faroes/ 1~O' 1.0' 1.32 1.27 1.21 1.25N of raroehroe-Shet- 1~71 1 ..7' 1.69 1.62 1.51 1..57land CbaDn.

S of Wir 0 ..89 0.9' 1.02 0.98 0.90 0.95Ridp

- . -total for ar.. lSUrVe;yed. ,.6, '.69 ".03 3.88 3-6' '.71

. ·Approx. total. !orewcloacd area. :·...67 ".7" 5.18 ".99 ".61 .....8.5AbunQa.uce per 100 etat.

10.54rectaDgle•• 10.. ,., 11.51 . 11.09 10.}1 10.71

e-A,Pril, 08-21 Continent8.l 19.98 1'+.61 26.. 15 18..22 18059 16.32

Sh611 (Ualin-Roaemary Bk.)

Rockall Chann. 6.31 6.48 4.85 '.'1 3.10 2.90Rockall 2.60 2.88 1.2JJ ".98 4.57 ".28

Total 28.89 83.97 38.52 26.57 20.26 23.50Abundance per 100 85.60 248.80 11'+.13 18.1' 71.81 69.6,atatiatica1 rectanglee.

Method of ~.ia Bank (cler!ve<l abundance)Feb. J.prU '1btal

Contouriq AM 1 2 " ' .•• ~tang&dar GHa4j .. 1

)t.CC5·Decr..iq .'..abaDdaDce Contouriq AM~ 2 .. 61RaC .Ntu.t. (JH/Bfadj)

RectansuJ.,ar AM -. , , 8CoIltouriDa GH. , 6 9""20 Contour1Ag,

6I (~<II.)

Contouring GI.. 5 11

1kble'Z 'Explorer' fisM,tle ~lI've:l rOfSl.ätlS April-I'~ 1?79--i'ishing Blus 1lIh1tiug

B'&ul St&t. Depth No. ~1." nun.tion otDate

,1)' ..... FiGhing GearN " Becto (I!) !aalteta Fiah ~

J:l9

45 100479 41tDl4- 450 0 0 Pelagic tralÜ 50 a1nIt.4,.5D'+

lt6 12 alt 19 42D5 JtOo- 220 6699b PeJ..a8ic trawl 1 bcNr"

500 ' '

"7 ' 12 0It 19 ~100 450 i 96 ~lqio b'a14 .., ldDa.

lt8 1,0419 43JX) ltOQ ,~ Pelacic .travl 50 1I1Da.

lt9 1" ~ 79 'tltlD ltoO , 15i 2 '/62 Pelqio trawl ~ 111118.

50 15 9'+ 79 lt6E2 450 2 628 Pelasic trawl • haur

51 180479 42ID ltoo- 10 2710 PeJ.aa1c ~rtlvl 30 a1Iw.4.50

• 52 18 05 '79 431)6 19Z 1i 535 BottOll trawl 1 hour

53 'l8 05 19 43D5 ? 22 116V 8otto~ trawl 1 hour

55 19 05 19 45D6 302 45i 9 802 Ho'twm tra\lll 1 hour

57 21 05 79 44D5 1~ 0 2 BottOll trawl 1 heur

58 21 05 79 431>5 156 ? 2484 BottOl:l trawl 1 hour

59 220519,44D6-

329 ? 2236 Bottos trawl 1hour44D? •60 22 05 '79 4400 128 0 10 Bottom trawl. 1 hour

61 22 05 79 43D5 1~ 12 6 667 Bottom trawl .. bo~

6~ Z2 05 19 42D5 156 1i 623 Bot tOll tX'8.wl 1hour

6, Z3 05 79 421)5 178 16 8 518 Bottom trawl ~ hour

64 ~ 0579 42D.5 161 14 8 222 BottOll tre....l 1 hoJuo

6.5 2.3 05 79 4205 192 6 2966 Bottom trawl 1 bour

• 66 ~05 79 41])5 4~ 73 12061 Bottca trawl 1 bour ,67 24 05 79 411)5 m ? 12 4~ Bottoa trawl 1 bcNr

,

68 2ft 05 79 4305 198 16 •.. 9 )JIt 8)ttoll trawl 1 hour

70 2.5 05 194)1X)- 131 ? '195 Botto:n trawl 1 hour43E1

\

i71 2f, 05 79 4}E1 119 92 Bottom trawl 1 hour

7Z 26 05 79 44ID 156 l' 5 Yto Bottom trawl 1 bour

73 26 05 ?9 44E1 150 ~ 7rp Bottoa trawl 1 hour

74 26 05 79 44E2 91 i 173 Bot tom trawl 1 hour

75 2.? 05 ?9 45E2 82 0 J Bottoo trawl 1 hour

e ·e!ahle 3 Micramesiatius ROutaS8DQ. ,... length at age (Oll)

Aße (yurs)8 1-'1 2 3 5 6' 7 9 1Q . 11 12 13 15+ 'fetal

Re!. Sex

AprU 1979 ,-F:191'+6 f '9.24 2}.98 25.75 Zl.~ 28.29 ~.08 29.83 29.73 30.'10 - - - - - 26.13

19.,z.. 23.68 26.82 28.'2 29.92 32.21 33.44 '3-06 -32-71 ;».67 ",,08 ".00 ".00 - 2:7.4747 r - 21.50 22.50 25.62 26.?O C:8.12 29.Ato ~.oo 29.20 31.00 - "'.00 - - 'Zl.63

22.50 24.00 26.00 Zl." 29.43 29.00 34.00 - • ".10 ;52.00 - 34.00 28.1548 f - 20.25 25.66 26." 29.00 30.00 - 30.12 ~.4, ".'50 ~."7 31.00 - • 29.24

19.25 21.50 24.71 28~25 29.65 30.64 31.76 32.85 ".05 ".04 »'07 ".8, ,z..50 - y..oo ;0.80lt9 { ~.6' 28.08 28.57 29.88 - 31.00 32.00 31.36 • - ~.oo - 29.06

26.74 29.81 ~.06· '1.21 31.93 33.2) ".53 31.47 ».8, 34.~ ""59 :54.!to 35.42 31.4350 f 23.?O ~.97 2'7.45 29.04 28.50 28.00 30.2,5 - 30.00 - - - - - 26.18

~- 24.12 ·26.19 28.'" 30.37 31.61 32•.53 )2.94 36.25 34.00 "'.00 - ~.OO - - 28.5751 { 19.4, 23.72 ~.91 26.8, ZI.71 .28.62 - 3'.00 ~.51 '1.00 • - - - - 26.52

19.50 24.95 25.'10 2B.;n 29.Jt6 30.~ ~.84 31.46 '1.08 33.00 - ~.50 - - .. 28.50KC1 f 24.50 Zl.71 Z1.67 28." 29.67 30.50 ;,>." 30.61 ".20 ".00 - - - 28.94

~.22. 29.11 29.83 '1.00 31.85 32.00 32.67 ".12 "'.75 ".~ 34.80' - . ;,It.OO 31.03

Ma119?918.47 26." 29.88 30.81 30.28 29.'69 24.60l:l9/52,62-65 { 19.96 22.00 23.56 29.10 ~.". 30.~ 33.00 :J);o50 29.0018.82 19.58 2'.51 25.21 29.16 :50.96 30.02 }2.35 '1.81 ?J2,.Zl - • ".00 - ~.OO 25.62

'E'!9/'l2 f a:76 26.38 26.68 2B.71 27.89 - ~.oo - • - 25.332~.38 26.47 30.00 28.27 i!!).6? 3'.00 - 36.00 - 24.65

KC2 r 25.00 25.00 ~.·75 27.?O 29..50 30.20 30.00 ;'>.00 30.1'1 31.25 31.17 ,0.50 '1.00 - 29.63Zl.1tO 29.67 28.75 32.00 32.36 }2.18 32.'4 ".00 )2.71 . :52.00 32.50 3'.00 35.00 31.56

,.

Ta.ble 4 l{icromesietius egutß3§m! Sex ratio, stage of m~t~rity, mern weight anJ condition factors

Stage of MaturitySex Ratio~ ~ cf' (%) ~ (f.) liean vei.~ht (g) Condition ( .)

Date

:;:/46 F.9~ * t i R RR SP 11m *

.t , .RR SP e ~ ~ c1' ~

L , ~1IIlll n 2 7R n

12 04 79 47.1 8.S 0.3 8.1 82.7 84 15.6 1.6 6.1 12.3 64.6 98

12 04 79 47 50.5 49.5 12.2 87.8 41 2.1 4.2 29.2 64.6 41I

13 04 79 48 r3•9 76.1 3.2 96.8 27 7.5 1.0 23.4 68.2 97

14 04 79 49 25.9 74.1 43.5 56.5 33 57.3 42.7 69 103.9 . 152.8 141.4 0.465 0.457 0.459{

15 04 79 50 !42.5 57.5 7.5 6.4 85.8 49 38.2 1.4 9.7 50.7 83 75.9 117.9 lCJl.2 0.498 0.457 0.473

18 04 79 51 1s6.3 43.7 6.2 15.8 78.0 BO 7.6 19.7 72.7 68 84.1 117.1 99.3 0.460 0.443 0.4')2I

19 04 79 "Kings-ICrolS ''1 27.7 72..3 101.4 124.0 117.7 0.416 0.408 0.410

TOTAL APiIL '39.9- ±12.9 j 4.4 0.1 14.) 81.3 314 11.8 1.4 1.4 25.3 60.6 456 88.0+ 129.3+113.9+ 0.474+ 0.4~2+ 0.461+

IB 05 79 179/52 f45.5 54.6 80.9 77.9 79.3 0.439 0.444 0.442

22 05 79 62 46.5 53.5 76.0 64.4 69.8 0.427 0.434 0.431

23 05 79 63 15°·6 49.4 45.3 42.3 43.8 0.4C2 0.512 0.497

23 05 79 64 45.7 54.3 47.2 49.1 48.2 0.475 0.492 0.484

23 05 79 65 49.0 51.0 49.0 52.3 50.7 0.466 0.470 0.468

26 05 79 72 158•8 41,,2 83.3 83.8 83.5 0.461 0.441 0.453

25 05 79 wKings-~3.5 46.5 115.2 126.5 119.3 0.439 1<>.400 0.425Cro8s''2 .

W1':..t 'WA! 51.4t 6.6 ~ 63.6+ 61.1;+ 62.5+ 0.458+ to.466+ 0.463+

I It Resea.rch hauls only - mean cf means

1 I

<10-.

• f

100~181

•tmneslkm2

"

••• ••. . '.· ....• ••••·.....

•

•

_......... -......- ---"';0- .~._-- ..- -15· 11.· 13° 1~ 11- 10· 9~ S· ," . ti~ S' ... i-.

D4 05 06 07 08 '09 fO E1 .E2 [) f4- E5 t6 E1...

55· '.-t--~t---+--+---+---+--~f-~

56-

nGURE 1 I ~ C-ö+1&\ I _ FobruAr7 1979. Cruiee track endblu.'wh1ting dena1t7 dietrlbutlone

• •I

.'; : . " ..." ..: .... -:

,".:.::: '

yy;:mE 2 I e..>fpt> ./ - Aprj 1 1 ,-; • Cruise track andbl:'e './:i t'~nc c.:.e~~.·: '.J distributilm.

.j

4 ..,

.: ..

• •itI

• ~t- . , , Al•• t"

f'.', I~lJI

I.1I

l'I,,~

i~~-.riS

.'...'.

,..·/~ ..~. ;'1• .; .....l'~,

"

•

..~

~,

"

R~tativ. echo­c.acticna, A})rl1 1979.

J " .*" '. '••/.

•

"

\

I) ••.. : ~- 1~_-.l"L-._~~·_~---L__, •T' .__..._.....J..._ _

"

..

.,.

·~:·.'jr __

..---_.. _.... --

Ea

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ES f6E4E3E2EOD9080106os1S-

." 9 ) co

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~r ,. • •

.;, - ....

112N3 ·"'2lir7,1 '4 ~. .. -

n-7 S1-Q .

3 .,2\·3 1~'1 54-' ~~·1

.4 , ! 3

. m-I ~.. a'l IDol, --6 , , , .

:n~6 'SOO

,,29-1.

S·

~~-1 0•\

J - ,

105-3 . 139-2 llZ-t

32·7 -. ~28-0. "I 6 ',~ "

•

60-3 0,

- ,3

:31·0 . 16-Q

, 236-0 ..

,

. 15·' 7·]

115·1 48".~

.-

0·0 .A M (tomes km-2.' "

o No ~;hr ru 15

.~ •...

Arithllletic IDMn denaitiee ot blue whiting :i.n Febru8.r;y(d.~ed outline) ancl April (full outline) 19'79.

-',

-II

I'. -I

"

Cant Shelf S GI 5rII

20 -

10 L Il,' .. {Ollt Sh.1t M .r sa"lloL...........dJJ.Im,..o e-:p-il nJTJ--:lJ.---..

20

10

Ot-a----,q..-.......LL!..L4.LJ.1..L.U.LLL.f..U.I..iIIIICb_.10 -

L Rockal Ch.....

o '-1II-u---tf1..QJ:J!h m Jl--__~ [ n','~__R_GdCIIl

40

-'e:a.- -...0:

•

-.

.. '"

- '1

i

4-0

All Arass

FaroI /Shetl~dChlnnel

S of WI T RI~SJlt

I I

•

.: All A...u

I'?O •

I ,. I I I I ; .•

2,0 3-0

.:--log,o ( t.kmi -+1)

LA

1·01 LI'

o

10

OU-.LLJUICl-.L-t:I.:L..L.4.-'o..L.JL.J-L.a...&.4..L.Al:1'--~­

•

>- 10uc~ 0 U-!.CD.-LLJ.J4-I:u..u..u.J--4..Ll.Ll.Ju..L..u..J-UU .l...1::i::l::z:a

~ ~ 10c.. r n MI _ n..- h.Of! / H Faro•

•LL. 0 b. n~ _

20

10

o -"""""'''''''''''''-T

~ &Jl_O......~J-fi&_20

•

FIGURE 5~

Lo5-trequency distribution of blue Whitingdensity deterrn~uatio~8. -

. . .

II

\

•

--0-+--1-I---.......-"""+----f----i---t---r---it--·t-··-.J ----r---:-ll---+---t-----t~I 0 •

naURE 6 T.nlvling atatiol18, Afri1-!!5t 1979

45-51.: April5~15: May8tationa vbere DO blue .m1t1ng toun4 bracketed•. '

.- t

, :

.. .I

".I

,','. ';

l·. .~ ,

.. t

•

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··~6 51,

..'; .. -.... .

•

. -. . -' ...

(ONtSHElF

- , ........ '.

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-- '.-.

. -.. _..• ,:. ....... ;~. .:

•

.:...:- .- ...._~ ...... :-.. .. -.'

. -..... .... .---',~ .." .

ROCKAll

214 ; .let APJ!IL4~ ,; ,)

D- .......;- --.-:·~Z01~CIiO....~.~-~=----~

~ ....

- .: .'

.•' '-.c..

•

•

". .FIGtmE ? Percontabe lenst~-:roquenc~üistributions.

I'lwnber 0: fiah meaGUl"ed al80 ahO\"41.. .