, IThis paper not to be cited without prior reference to the author

International Council for theExploration of the Sea

C.M.1983/J:13Baltic Fish Committee

-.

Length Versus Gutted Weight,Versus Round Weightin Cod of the Kiel Bay

byFritz Thurow

Bundesforschungsanstalt für Fischerei, Institut fürKüsten- und Binnenfischerei, Wischhofstraße 1-3,D-2300Kiel'14, Fed.Rep.of Germany

Abstract: Length and weight of round and gutted cod wassampled throughout the season 1970/71. Relations between thesevariables established per month appeared not to be fully satis­factory. Gutted weight was offered as a better basic variablefor yield assessment than round weight.

Resume: Chaque mois dans la saison 1970/71, on a mesure lalongueur et le poids des morues abattues et pas abattues •

.Pour deduire le poids pas abattu du poids abattu Oll de lalongueur, des equations etaient calcul~es pour chaque' mois.

Mais elles ne sont pas beaucoup satisfaisant. Le poids abbatuest regarde plus convenable comme une variable fondamentale quele poids pas abattu pour estimer le produit.

- 2 -

•

Subject'. ,

The evaluation of the amount of cod caught may be based onlandings or on catch weights. Basic statistics are round weight,gutted weight, head-off weight, or filet. For much of the catch,if not for the total, conversion is inevitable. Since severalcountries are contributing to the,exploitation of each of theBaltic cod stocks, ,their methods of conversion must be calibrated.

It appears that no information is published as to how the weightof the catches has been ascertained in the different countries.Likewise the Working Group on Assessment of:Demersal Stocks inthe Balti~Dem.W.G.) has not reported to have discussed basicdata and methods Underlying the catches reported to the group(Dem.W.G.,1973-1982). This paper tentatively shows some relation- ..ships which,have a bearing on the above assessments.

..- 3 -

•

, .Except for a few samplos, gutted and unguttod weight~ of lnrgocod are generally attributable to separate fish; becauso few roundcod were available for gutting. For almost all undorsized codboth woight categories could be ascertained for identical finh.This procedure genorated highvariance in large cod. In some'size groups represerited by few fish only the average gutted weightappears to be higher than the ungutted we~ght. It is hoped,' how­ever, that the sampIes do also cover a corresponding number of

. fish with too high a weight. During five months in the periodMay-December 1970 a number of cod has been sampled from which

'both measures were ascertained fromtEsame fis~generally rangingabout 18 to 85 cm in length. The average monthly round we1ght/,gutted weight ratios' of these fish correlate nicely with thecorresponding ratios fram Table 2 (Figure 1). Both variables are

. '

not independent, however,'because the sampIes of gutted fish ofTable·2 do also include those which were measured asround fish.(Unfortunately, the data have been mixed up.). Nevertheless,Figure 1 gives some indication·of the reliability of the materialas Table 2 presents results derived from the basic data. Figure 1

suggests, that the round,weight rate derived from identical:fishis about 1,% higher than that derived from a mixture.

r-Iethods

Table 1 shows grauped data which actually represent average weights 'atlength. Originalweight at length data are. separately available.But lack of time prevented the'use of these. Grouped data wereused instead for regression estimates together with the number ofobservations to put some weight on the more reliable pairs ofvalues. ,This,has some bearing. The,total variance is considerablyreduced to whnt may be called an average variance and the correlationappears to be more rigid than it actually iso However, this paperis not meant to show, that the overwhelming part of the variancein the correlation between round and gutted weight is explainedby linear relation. It is more aiming at the need for a widerdiscu~sion of the subjectoutlined in the beginning.

Round weight versus gutted weight.

The grouped data of Table 1 have been used to calculatelinearregressionsfor.r9und over gutted weight at length (Table 2).

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Generally, the number of observations is higher for the groups ofgutted fish thanfor the groups of round cod. The lowest number ofobservations was always used no matter whether these were basedon gutted or ungutted cod.

Table2 shows remarkable differences of the constants a and bbetween months. The round weights calculated from these linearrelations for gutted weights of 0.2 kg and 10 kg suggest seasonalityin the larger weight but not in the lower. There are also quiteconsiderable differences in the length ranges of the monthly sampIesdue to the scarcity of round cod of larger sizes (Table 1). Forfurther analysis the results for March 1971 in Table 2 are omitted.The few fish are all very large and produce a very high variancein that month. The main question arising from these problems iswhether or not seasonality·of the constants is present. ~

The incubation time for cod eggs extends over some 2-S'weeksdepending on the temperature (HeIa and Laevastu,1961). The firstsmall period ofdevelopment, one day or so, is covered by the primarygerm cell stage, where no endoderm, hence no viscera, are present."Round" and "gutted" weight are equal. This could force the slopeto a negative intercept. However, the egg weight is some 3 g andthe embryo is but a small fraction of this. Considering the above­mentioned possible errors, the effect of this development stagecan be neglected. For all practical purposes its plot in the roundover gutted weight graph m~y be considered indentical with theorigin where both variables are zero.

Juveniles and.adults grow differently throughout·the season in tha~

adultsprodue r~ gonrls,juveniles not. This should'result in season­ality of intercept and slope. The latter is likely to be highestat the onset of spawning when the interceptcan be expected to belowest being generally in the negative range •.

To show the different growth pattern of juveniles and adults letus consider the behaviour of the round weight, Wr , in terms of theratio Wr/Wa • Sexualmaturity of females and males is obtained at38 cm and 35 cm respectively (Thurow,1970). Wewill therefore inspectsizes L 32 cm on the one hand and~40 c~ on thc other although imma­ture fish are also present in the latter and mature ones in thcformer. The bimonthly averages vary1.09.- 1.20 in adults'and only1 .11 '. - .1 .13 in juveniles (Table 3). This suggcsts that a l<?wer value

•

- 5 -, ,

of about 1.1 applies to both groups whereas the highcr valuesdiffer greatly. Correspondingly, Figure 2 suggests strong season­ality in larger cod anda poor one in thc smaller fish. The wcightof the viscera'of adult fish is highest November to Har~h whichfits the ideas outlined,beforc. Production of sexual products andspawning are likely,to produce a regular seasonal cycle in therate of the round weight of adults. A weak maximum in juvenilesiS,exhibited in spring. Whatever the reasons for this latterbehaviour may be" the strong seasonality in adults and the poorone in immature fish are sufficient to produce the said season­ality inthe slope of the round over gutted weight relationship.This is obvious from Figure 3. The slope ,is steep in winter,declines until about August and increases thereafter. The standarddeviation is meant to show that the variance of the slope is muchlower than the variance of the i!1tercept, It is but a fraction ofthe total standard deviation and can not serve as a measure forthe goodness of the indication of seasonality.

The intercept, on the other hand, doos not seem to be acase forseasonality.at all. Here, "average standard deviation" may'serveto show that seasonality does not bear out from the data.

Nevertheless,'there is hardly'any doubt ,that seasonality is present-in the'Wr/Wa relationship and that this is largely due to spawning.The 'cönclusion should be to evaluate the weight ofthe catch (round

weight) ~or each month separately from linear relationships'betweenround and gutted·weight. However, one difficulty arises from the

~ negative intercepts. Some of them tend to make round weight esti-,mates for small cod much smaller than shown by the actual' data.This error increases as cod sizes d~crease (Table 2). In particular,for some undersized cod the round weight estimate may then besmaller than the gutted weight. Clearly, this is not acceptable.On~ way out would be to assurne astraight llne through the origin.If the length composit~on of the samples is.carefully adjusted tothat of the catches, this procedure is likely to be a better toolfor round weight. estimates than regression equations.

still it seems,to beunacceptable to some statistical offices toproduce monthly estimaflst~~~ithone varying constant. A globalannual~ conversion,factor is used.instead~ For instance, a factorof 1.24 instead of the correct one of 1.18 produces an error.of

•

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5 ~~. Such differences, between true and computed catch do notseem to be very high in terms of TAC estimates. But for somestocks which decrease in biomass even these errors may be vital.This appears to apply to the cod stock in subdivision 22 (Thurow,1982) •

In summary, none of the·procedures to estimate catch from guttedweight appears to be satisfactory. It would be more promisingto get rid of the implications with spawning and use gutted weightas basic variable for stocl{ assessment. However, it is advisableto discuss the whole matter within the Committee, whenbasic data,such as shown here, are at hand from morccountries. Lack of timeduring Assessment Working Group meetingsplaces the matter withthe Committee.

Weight-Length-Relationship

Monthlyregression data as shown in Table 2 have been used to com­pute round weights for thc gutted cod of Table 1 and combine themwith those round weights of the same length groups which have beensampled. The results are shown in Table 5. This represents thedata used for the computation of the allometric weight-lengthrelationship (Table 6). Here, variance is further reduced, becausesome round weight value~ in Table 5 are not sampled but computed.Comparisons with independent estimates could indicate how reliablethe equations in Table 6 are.

Monthly weight calculated for lengths 30 cm and 100 cm do not showa clear seasonal pattern (Figure 5). Small cod exhibit no trend •and little variation. Neither is it clear whether a seasonal courseis concealed in the variation of the weight of the large cod. An

overall regression has therefore tentativelybeen established. Theidea is that conversions are made for cod in the catches. Averagescould therefore be weighted according to catches rather thanaccording to number of observations.

Clearly, what has been said about seasonality in the round/guttedweight regression also holds here. Tbe weight-length relationshipfor the whole year but with gutted weight is likely to explain

more of the variance than with round weight. This is thereforeanother.case~for stock assessments to be based on gutted weight.

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Recommendation

Dearing in mind that the procedures in thc different countriesto estimate the catches of cod .have never been discussedand that the methods have not been calibrated, it is recommended

1.) To make

"Basic Data and their Conversion to Catches"the special theme for 1984 and to urge Committee members todeliver correspondings contributions

2.) To discuss the results thereof, agree on' uniform or comperablemethods, and recommend to the Council to pass aresolutionto the effect that these methods be applied in the future •

Citations

1. ANON. Report of the Working Group on Assessment of DemersalStocks in the Baltic, C.M.s:1973/F:6; 1974/F:4; 1975/P:17; 1976/P:2; 1977/P:2; 1978/J:3; 1979/J:4; 1980/J:3; 1981/J:2; 1982/Assess:17

2. HELA,I. and LAEVASTU,T.,1961, Fisheries Hydrography, Fishing News(Books)Ltd,London,177 p.

3. THUROW,F.,1970, Uber die Fortpflanzung des Dorsches, Gadus morhua, (L.), in der Kieler Bucht, Ber.Dt.Wiss.Komm.Meeresforsch.

21,H.1-4,170-192 pp.4.- 1982, Growth Production of the Baltic Fish Community,

ICES,C.M.1982/J:5, 39 p •

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Table 1: Length-weight frequencies of round and guttedcod of Kiel Bey, May 1970 through September 1971

•

•

L MAY 1970 JUNE 1970 AUGUST 1970Wr,g n Wa,g n Wr,g n Wa,g n Wr,g n Wa,g ncm

102468

20 70 2 61 22 114 2 101 24 ,

6 241 1 212 1 !I8 230 2 209 2 I1

30 293 18 259 18 !2 331 18 298 18 327 3 I4 378 9 337 9 398 136 450 1 375 2 435 26 1

8 388 4 499 2440 675 2 565 4 566 29

III2 783 3 700 3 750 1 630 5 646 22 1I4 883 12 768 26 738 19 I6 981 8 864 7 962 11 828 31 831 8 ,

8 1 240 10 950 7 1 081 21 936 44 996 10

I50 1 363 12 1 162 13 1 189 12 1 03073 1 073 132 1 310 5 1 170 10 1 406 10 1 163 53 1 256 15 I,4 1 493 7 1 281 8 1 440 12 1 301 59 1 268 11 ;

I

6 1 660 5 1 400 9 1 587 6 1 404 36 1 378 9I,,

8 1 800 4 1 630 5 1 785 2 1 538 31 1 650 3II

60 2 250 10 1 805 10 1 825 4· 1 720 25 1 748 13 !2 2 313 4 1 975 2 2 236 5 1 910 18 2 150 2

,,

4 2 500 3 2 183 3 2 227 3 2 075 13 2 104 5 !i6 2 100 2 2 275 2 2 425 2 2 337 7 2 244 8 i8 2 800 1 2 250 1 2 361 10 2 440 5 Ii70 3 400 1 2 664 7 3 350 1 2 865 6 2 667 6 I

2 2 450 2 2 852 6 I4 3 985 2 3 392 10 3 317 36 3 925 2 3 150 2 3 340 2 4 057 38 3 150 1 4 068 5 I80 4 775 2 4 067 3 4 673 3 I2 3 700 1 4 424 5 I

4 5 200 1 5 310 2 I6 4 100 1 5 298 48 5 750 2 5 950 1 4 870 1

90 5 050 2 , 5 510 12 5 780 54 7 400 1 7 225 26 7 283 3 8 360 18

100 7 175 2 7 450 12468

110 11 200 1 10 010 124 11 150 268

120

- 9 .- .

Table 1: continued

LSEPTEI1BER 1970 OcTOBER 1970 NOVEf1BER 1970

Wr,g n Wa , g " n' vI" g n W ,g n W ,g n Wa,g . ncm r' a r

10 8 61 9 2 7 22 15 18 16 9 14 94 26 6 28 4 25 46 39 3 39 12 35 128 49 7 51 11 45 11

20 74 27 67 2 61 22 95 35 91 2 81 24 124 28 135 1 139 7 122 76 165 21 149 6 173 10 151 108 207 24 186 8 212 3 180 3 222 11 196 12

30 274 11 250 10 263 4· 228 4 243 8 210 8'2 329 8 298 8 353 2 308 2 337 6 284 7

4 387 20 350 20 420 16 476 17 426 17 540 3 449 4 .490 2 .420 2'8 526 35 473 35 . 570 17 497 17 605 10 483 10 .

40 613 15 544 15 650 17 . 583 19. 704 12 587 92· 723 16 645 16 723 13 687 17 779 20 670 154 835 12 755 12 840 9 791 21 941 17 775 176 984 6 876 6 1 008 14 908 44 1 007 27 836 258 1 050 1 920 1 1 081 8 996 62 1 157 22 1 008 32

50 1 313 5 1 191 5 1 144 11 1 090 76 1 378 23 1 127 392 1 350 4 1 235 51 1 54615 1 245 344 1 350 1 1 230 1 1 520 4 1 328 47 1 635 16 1 333 316 1 585 1 1 405 1 1 400 2 1 435 50 1 724 11 1 478 228 1 930 1 1 690 1 1 755 2 1 533 36 1 908 10 1 599 26

60 1 720 1 1 550 1 1 753 24 1 957 7 1 702 142 2 010 1 1 790 1 2 070 2 1 881 24 2 253 4 1 834 164 2 490 1 2 555 2 1 942 23 2 264 9 2 018 166 2 330 1 2 155 1 2 830 1 2 303 15 . 2 571 8 2 267 148 2 550 6. 2 338 10 2 978 4 2 439 7

70 3 440 1 2 810 1 3 600 1 2 595 12 3 266 5 2 742 112 2 720 2 2 778 8 3 588. 4 3 069 124 2 773 3 3 135 2 3 094 8 3 695 2 3 211 86 3 570 1 3 583 6 4 313 8 3 602 13 ,8 4 040 2 3 985 4 4 360 4 3 910 9 ,

80 4 950 1 5 670 2 4 393 42 3 680 1 4 250 4 4 290 1 4 701 104 5 000 1 4 370 1 4 885 6

,!

6 4 985 2 6 190 1 4 638 4 6 090 1 5 028 4 I18 4 170 1 4 805 2 8 050 1 . 5 765 .4 ,

90 6 126 5 I

2 8 020 1 5 940 3 6 880 1 :I

4 7 870 2 !6 7 180 1 6 090 1 j8 !

I100 8 470 1 I2 9 050 1 8 400 2 8 810 2 I4 9 050 1 8 358 4 I

6 9 360 1 8 350 1 10 220 2 I8 I

I110 I2 I4 I6 11 080 18 I

120 . .", , " ... I

- 10 -

Table 1: continued

,

L DECEMBER 1970 JANUARY 1971 FEBRUARY 1971·W g n Wa,g n Wr,g n vla' g n W ,g n W ,g ncm r' r a

10 8 4 7 42 13 15 12'164 23 8 21 7 15 1 14 16 34 12 31 12 31 5 29 58 49 5 44 5 49 5 44 5

20 64 3 57 3 68 11 62 11 63 2 58 22 103 7 92 7· 86 2 78 2 93 1 81 14 128 10 114 10 127 4 116 46 165 8 150 9 161 5 144 58 204 2 179 2 218 1 198 1 209 7 186 7

30 273 8 245 8 239 13 213 13 243 7 216 72 326 12 30212 310 5 269 54 403 14 362 13 358 3 305 26 441 12 385 8 460 1 398 1 356 18 589 5 495 24

40 875 .2 790 1 586 14 643 4.2 812 5· 800 1 720 21 975 2 670 54 944 13 825 2 680 1 960 2 768 56 1 077 18 936 14 1 182 13 864 278 1 206 35 1 041 14 1 254 33 977 36

50 1 375 34 1 176 23 1 275 2 1 290 24 1 065 442 1 479 23 1 265 30 1 625 10 1 401 26 1 185 514 .1 756 17 1 383 22 1 626 8 1 497 21 1 303 306 1 792 16 1 459 13 1 941 8 1 661 16 1 422 318 1 99212 1 653 12 2 218 13 2 053 12 1 520 29

60 2 238.10 1.829 9 2 313 14 2 300 1 2 101 11 1 798 262 2 669 7 2 040 9 . 2 241 8 2 319 14 1 909·154 2 541 10 2 135 19 2 730 5 2 294 7 2 042 136 2 517 10 2 295 13 2 726 7 2 270 1 2 713 13 2243 268 3 200 3 2 602 11 2 878 9 2 668 5 2 834 9 2 528 19

70 2 825 4 2 793 16 3 540 4 2 880 3 2 943 6 2 720 242 3 378 6 2 865 15 3 553 10 2 865 2 3 515 6 2 929 304 3 126 5 3 250 1 2 780 4 3 966 9 3 118 296 4 070 3 3 677 15 4 350 1 3 375 4 3 877 3 3 485 238 .5 395 2 4 178 16 4 400 2 3 415 2 4 184 5 3 650 29

80 4 635 2 4 272 22 4 348 5 4 470 2 3 903 142 4 689 17 4 606 5 4 240 2 4 195 184 5 133 6 5 450 2 4 484 9 5 400 2 4 763 166 8 160 1 5 058 14 4 777 6 4 982 198 6 695 2 5 808 22 5 583 8 5 329 12

90 6 066 14 5 390 4 5 720 1 5 488 202 6 762 13 5 905 4 9 460 1 6 164 204 7 167 9 6 050 1 6 235 4 6 940 1 6 419 146 11 650 1 7 419 16 6 690 5 6 556 88 7 983 12 7 010 1 7 263 14

100 I 8 693 9 7 040 3 7 689 102 8 529 9 8 537 3 7 610104 8 240 4 8 610 5 7 923 76 10 422 5 9 315 2 8 818 48 9 353 6 9350 2 10 675 2

110 10 280 1 8 950 1 9 625 2 10 027 32 11 005 4 10 480 14 10 502 5 11 345 26 12 660 1 11 810 28

120, 2 14 000. 1

i

I

T 11 -Table 1: continued

.L MARcH 1971 APRIL 1971 my 1971

cm \'lr,g n Wa,g n Wr,g n Wa,g n Wr,g n . Wa,g n

10 7 2 6 22 13 7 ·10 7 11 14 19 19 15 196 31 12 26 12 40 2 35 28 46 21 40 21 50 7 43 7

20 64 12 56 12 69 9 60 92 95 10 84 10 93 8 83 84 124 3 107 3 119 3 105 36 140 1 126 1 153 1 139 18 213· 10 186 10 209 4 187 4

30 255 24 224 24 263 13 233 132 300 1 281 15 257 15 304 23 267·234 320 2 352 14 314 14 356 13 333 166 420 3 442 4 388 4 396 3 413 78 459 16 500 1 484 3 460 1 483 4

40 538 6 555 2 540 6 497 3 552 62 639 7 725 ·2 598 9 638 9 644 124 920 3 787 . 7 774 5 ·847 146 1 088 5 835 2 848 20 1 174 5 847 298 1 187 12 928 10 912 59 986 10 947 37

50 1 260 13 966 10 981 57 1 290 13 1 040 422 1 457 16 1 112 15 1 081 61 1 138 6 1 177 404 1 568 9 1 258 4 1 197 56 1 573 11 1 310 336 1 821 11 1 580 4 1 338 40 1 891 7 1 392 228 2 065 8 1 695 4 1 489 28 1 700 3 1 719 12

60 2 040 6 1 848 4 1 613 20 2 680 1 1 700 222 2 121 7 1 907 3 1 621 14 2 158 5 1 751 244 2 155 2 2 518 4 1 981 12 2 177 3 1 965 246 ! 3 428 5 2 040 1 2 480 3 2 151 9 2 579 7 2 185 26,

8 , 3 423 4 2 663 3 2 086 7 2 271 1070 i 3 053 1+ 3 095 2 2 950 2 2 182 5 2 487 15

2 3 628 4 ·3 205 2 3 000 13 2 731 104 3 665 2 3 150 1 3 138 5 3 440 1 3 197 146 4 740 1 2 880 1 3 390 . 1 3 337 7 3 920 1 3 351 88 I 4 590 2 3 265 2 3 170 1 3 660 4 3 335 2I

80 j' 6 160 1 4 350 1 4 020 1 3 773 3 4 760 22 ' 5 100 1 4 630 3 4 200 54' I. 5 860 1 4 150 1 4 510 2 5 090 16 4 860 1 4 750 1 5 160 1 3 953 3 4 643 38 6 190 1 5 350 1 5 400 1

90 I 5 720. 3 4 583 3 4 940 12 9 790 1 6 600 2 5 973 4 5 370 14 . 7 313 3 5 313 3 5 600 26 6 935 4 6 458 4 8 010 18 12 300 1 8 663 3 7 8001

100 7 528 42 7 770 1 8 770 146 8 510 38 10 790 1

110 9 874 52 10 623 4l~

(.)F1 1 1+ 345 ?

120 . . . .~" - ". ~. ..132 16 980 2

•

•

•

•

- 12 -

Table 1: con~inued

... JUNE 1971 JULY 1971 AUGUST 1971iL Wr,g on Wa,g n Wr,g n \'1a ,g n Wr,g n v1a' g ncm

10 .24 30 1 25 16 37 6· 47 48 57 22 49 22 63 3 57 3

20 74 18 65 18 82 19 72 19 79 5 71 52 104 29 92 28 108 20 98 20 109 8 98 84 134 19 120 19 144 26 127 25 141 12 127 136 185 8 163 8 181 20 °163 20 179 16 161 158 244 2 202 3 216 26 194 26 224 17 201 17

30 286 6 252 10 263 5 231 5 273 25 236 252 318 20 293 20 329 11 .290 6 284 9 281 104 377 11 344 11 384 31 340 9 355 19 355 306 395 2 416 6 443 36 406 13 410 5 441 518 521 7 445 2 542 22 491 15 585 2 505 46

40 656 5 478 6 613 13 560 23 580 1 596 332 710 1 567 3 760 6 726 20 770 2 699°434 793 3 720 5 874 7 811 46 780 1 753 866 925 2 778 16 978 4 869 80 860 1 934 958 1 058 4 922 33 1 074 7 949 73 1 030 2 1 015 96

50 1 147 7 1 056 40 1 132 6 1 030 6 1 088 962 1 200 3 1 138 27 1 169 46 1 275 6 1 216 954 1 445 2 1 290 31 1 405 2 1 264 36 1 430 1 1 345 916 1 780 1 1 441 21 1 600 1 1 438 44 1 715 2 1 488 898 1 564 12 1 533 32 1 750 1 1 610 74

60 1 720 7 1 726 22 2 025 2 1 769 58,2 2 190 1 1 743 7 1 914 16 1 960 1 1 °955 38

4 2 197 3 2 040 11 2 111 176 2 660 1 2 407 7 2 293 12 2 370 388 2 687 3 2 870 1 2 386 11 2 472 31

70 3 870 1 2 793 3 2 792 9 2 665 352 3 218 4 3 105 6 3 010 394 3 850 1 3 187 3 3 397 7 2 924 356 2 690 1 3 323 3 3 635 2 3 369 258 3 280 1 3 345 2 3 797 44

80 4 140 4 4 166 282 4 170 1 4 203 °234 5 260 ° 1 4 719 206 4 755 1 4 924 208 6 195 2 5 285 15

90 5 460 1 5 530 1 5 851 162 5 550 1 6 420 104 6 740 66 7 230 1 6 925 2 6 873 48 6 690 1 7 195 6

100 8 630 424 7 675 26 8 950 18 9 860 3

1102 9 660 1 10 350 1468

120

- 13 -

Table 1: continued

L SEPTEMBER 1971Wa,g n Wr,g ncm

102468

20246 170 1 190 18 210 1 240 1

30 247 4 273 42 300 8 334 84 311 2 337 26 415 2 475 28 500 1

40 721 8 630 32 743 12 766 54 825 15 865 46 923 23 767 38 987 40 1 016 5

50 1 102 76 1 218 82 1 195 83 1 250 34 1 321 81 1 410 16 1 435 80 1 470 18 1 553 74 1 740 3

60 1 721 76 1 800 52 1 854 494 2 108 40 1 760 16 2 340 32 2 490 18 2 511 32

70 2 624 36 2 000 12 2 941 294 3 224 276 3 470 268 3 885 27

80 4 168 282 4 239 174 4 628 166 5 002 138 5 407 14

90 5 745 112 6 000 44 7 503 66 6 668 108 6 873 3

100 7 940 22 8 340 24 9 620 26 8 607 38 9 614 5

110 I2 I4 I6 I

8 I120 I

Table 2 : Linear . regression of round weight versus gutted weight,Wr = a+bWa , for cod of Kiel Bay

MONTH I W Wa n b a W Wr forr range,cm -..r

YEAR! g g max.(frequent) W Wa=200 g, 10 000 ga

V 7011755 1490 72 1.1822 -6.1873 42(42)-( 66) 80 1.178 230 11 816VI 70 11028 904 160 1.1224 13.424 20(30)-( 66) 74 1.137 238 11 237 ~

VII 70 I~

VIII IIX 701 608 544 166 1.1458 -15.73 24 2T( 50) 70 1.118 213 11 442

I X 7011035 922 121 1.2035 -74.98 28 28 -( 58j 86 1.123 166 11 960I XI 70 i1316 1105 319 1.1995 -10.12 10 10 -( 80 96 1.191 230 11 985i XII 70! 1340 1124 294 1.2482 -62.34 10 10 -( 80 96 1.192 187 12 420: I 71 11509 1267 44 1.2117 -26.11 20 68)-( 72 84 1.191 216 12 091I 11 71 11777 1486 286 1.2030 -11.26 14 16)-( 84~ 94 1.196 229 12 019I 111 71 [6258 4440 9 1.3648 197.39 66(78)-( 78 98 1.409 470 13 845! IV 71, 569 497 214 1.1756 -14.32 10~10r( 72~ 86 1.145 221 11 742i V 71 i 866 732 154 1.1893 -4.368 16 18 -( 66 76 1.183 233 11 889I VI 71 i 388 344 176 1.1160 3.712 14 16 -( 54) 76 1.128 227 11 164I VII 71 I 392 354 208 1.1221 -4.785 18(18)-( .50~ 56 1.107 220 11 216

VIII 401 375 137 1.0717 ~.0778 20(20)-( 62 62 1.069 214 10 716IX 71 I 898 856 59 1.0598 -9.698 26(30)-( 60) 70 1.049 202 10 588

I

VI average weight in sampIe, S standard deviation, t student test statistic

•

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- 15 -

Table 3: Seasonality of the round, gutted weight ratioof juvenile and adult cod.of Kiel Bay

MONTHSIZES <. 32 cm .

\~rSIZES '::>'40 cm Wr

Wr Wa--

\'l W--YEAR n Wa

n Wr a a

I 71 157 141 27 1.113 3973 3505 20 1.13411 71 159 141 42 1.128 2076 1735 241 . 1.197

111 71 6258 4440 9 1.409IV 71 121 107 136 1.131 1664 1467 80 1.134

IV 70 1755 1490 72 1.178V 71 191 168 71 1.137 1461 1261 90 1.159

VI .70 286 255 43 1.122 1386 1217 107 1.139VI 71 143 128 128 1.117 1334 1153 33 1.157

VII 71 162 144 124 1.125 939 850 47 1.105VIII 71 207 185 92 1.119 1305 1222 20 1.068

IX 70 247 224 33 1.103 946 844 62 1.121IX 71 300 269 14 1.115 1418 1190 44 1.192X 70 266 229 9 1.162 1242 1115 92 1.114

XI 70 128 113 84 1.133 1806 1521 225 1.187XII 70 116 108 93 1.074 2079 1737 180 1.197

1/11 158 141 69 1.122 2221 1871 261 1.187III/IV 121· 107 136 1.131 2129 1768 89 1.204V/VI 183 162 242 1.130 1491 1288 302 1.158VII/VIII 181 161 216 1.124 1048 961 67 1.091IX/X 263 236 56 1.114 1188 1047 198 1.135XI/XII 122 110 177 1.109 1927 1617 .405 1.192

Table 4: Seasonality of the round~ gutted weight ratioof cod of all sizes sampled in Kiel Bay

!'10NTH 'tl WaWr . fraction of

n average yield 1970/80r W FR GERNANYa1/11 1741 1457 330 1.195 .35

III/IV 769 656 223 1.172 .17V/VI 876 757 562 1.157 .08

VII/VIII 396 362 345 1.094 .09lxix 807 730 346 . 1 .105 .12XI/XII 1328 1114 613 1.192 .19 .

aver. '\',eighted acc.to yield 1.168S .037

- 16 -Table 5: Length-weight frequencies in cod of Kiel Bay

1970/71, round weight, partly converted fromgutted weight

. .L JAN. FEB.

;

BAR. APR. IJIAY JUNEcm W,g n W,g on W,g n W,g n W,g n \'l,g n

10 ,. 7.0 22 12.9 7 11 14 15.0 1 18.7 19 30 16 31.2 5 31.3 12 40 2 37 68 49.2 5 46.1 21 50 7 57 22

20 67.7 11 63 2 64.4 12 .69 9 73 202 85.5 2 93 1 94.6 10 93 8 105 314 127 4 124 3 119 3 134 196 161 5 140 1 153 1 191 98 218 1 209 7 213 10 209 4 237 5

30 239 13 243 7 255 24 263 13 292 28'2 310 5 300 1 281 15 304 23 324 38

4 358 3 320 2 352 14 361 16 377 206 460 1 398 1 420 3 442 4 443 7 448 88 495 24 459 16 545 3 534 4 521 7

40 586 14 762 4 538 6 607 6 568 6 641 1_2 720.21 792 5 639 7 706 9 691 15 708 84 680 1 845 5 920 3 . 922 7 906 14' 872 316 1 102 27 1 088 5 978 20 1 009 36 943 478 1 247 36 1 187 12 1 045 59 1 104 44 1 076 7'7

50 1 275 2 1 281 44 1 260 13 1 118 57 1 277 55 1 197 1132 1 625 10 1 408 51 1 457 16 1 229 61 1 329 50 1 340 804 1 626 8 1 515 30 1 568 9 1 393 56 1 524 41 1 491 906 1 941 8 1 680 31 1 821 11 1 569 40 1 684 31 1 637 578 2 218 13 1 915 29 2 065 8 1 738 28 1 876 17 1 787 4360 2342 15 2 130 26 2 040 6 1 882 20 2 103 32 1 969 322 2·241 8 2 317 15 2 121 7 1 901 14 2 108 26 2 173 254 2 730 5 2 364 13 2 155 2 2 387 12 2 310 27 2 390 166 2.724. 8 2 700 26 3 428 5 2 507 9 2 515 28 2 693 1'4,-~ .

8 2 878 9 2 937 19 3 423 4 2 538 7 2 645 10 2 775 1370 3 540 4 3 181 24 3 053 4 2 714 5 2 963 22 3 359 9

2 3 553 10 ,3 513 30 3 628 4 3 468 13 3 160 10 3 427 64 3 308 5 3 810 29 3 665 2 3 572 5 3 680 14 3 886 136 4 097 5 4 142 23 4 740 1 3 837 7 3 858 10 3 620 58 4 240 4 4 346 29 4 590 2 4 010 4 3 859 2 3 280 1

80 5 196 5 4 653 14 6 160 1 4 288 3 4 926 52 5 504 5 4 947 18 5 977 1 5 426 3 4 763 64 5 375 11 5 679 16 5 860 1 5 286 2 5 953 26 5 709 6 5 982 19 5 214 2 4 807 3 5 216 48 6 672 8 6 400 12 7 255 1 5 839 2 6 653 2 6 884 1

90 6 441 4 6 547 20 6 704 3 5 371 3 5 800 3 6 317 12 7 056 4 7 507 20 8 763 2 7 000 4 6 609 64 7 171 5 7 656 14 8 571 3 6 227 3 7 173 36 7 995 5 7 876 8 8 128 4 7 569 4 8 637 4 8 365 18 8 377 1 8 726 14 10 869 3 9 142 1 7 740 1

100 8 413 3 9 239 10 8 823 . 4 8 301 2 8 620 12 10 202 3 9144 10 9 106 1 10 278 14 10 289 5 ,9520 76 11 131 2 10 597 4 9 974 3 10 355 18 11 173 2 12 831 2 12 646 1

110 10 651 3 .12 ,051 3 11 572 5 12 958 12 12 524 1 12 450 4 11 177 14 12 550 5 13 637 2 12 901 26 14 196 28 16 812 2

1202 16 730 1

132 19 901 2

.-----------------~--~-~- -

- 17 -'

Table 5: eontinued

L JULY AUG. SEPT.' OCT •. NOV. DEC.ern W,g n W,g n \'1, g n W,g n W,g n W,g n,10 .. 8.2 61 8.7 . 2 7.8 4

2 15 18 15.5 9 12.7 154 26 6 27.8 4 22.9 86 39 3 38~7 12 34.3 128 63 3 49 7 50.7 11 48.8 5

20 82 19 79 5 74 27 67 2 63.7 32 . 108 20 109 8 95 35 91 . 2 103 '74 144 26 141 12 124 28 139 7 128 106 181 20 179 16 166 22 173 10 167 .98 216 26 224 17 208 25 212 3 223 12 204 4

30 263· 5 273 25 274 15 263 4 243 8 273 82 329 11 302 12 ·331 16 353 2 337 7 326 124 384 31 . 388 43 382 22 420 1 403 146 443 36 476 77 . 476 19 540 3 490 2 '441 128 542·22 551 70 526 35 570 17 605 10 589 5

40 613 23 636 62 616 18 649 19 704 12 875 22 784 20 745 65 733 21 732 17 779 20 812 54 885 46 820 105 843 16 859 21 . 941.17 944 136 952 80 1 011 103 1 004 29 1 005 44 1 007 27 . 1 077 188 1 042 73 1 107 106 1 071 41 1 098 62 1 171 32 1 206 35

50 1 127 69 1 188109 . 1 213 81 1 19676 1 364 39 1 375 342 1 279 46 1 333 110 1 305 83 1 364 51 1 511 34 1 486 304 1 384 36 1 462 102 1 444 82 1 472 47 1 613 31 1 732 226 '1 574 44 1 619 98 1 569 81 1 578 50 1 743 22 1 792 168 1 677 32 1 763 77 1 704 75 1 697 36 . 1 907 26 1 992 12

60 1 888 22 1934' .71 1 875 77 1 937 24 1 996 14 2 238 10'2 2 094 16 2 145 40 2 028 50 2 078 24 2 203 16 ,2 616 9

4 ·2 232 11 2 308 22 2 303 41 2 181 '23 2 326 16 2 543 196 '2 509 12 2 569 46 2 551 33 .2 564 15 2627 14 2 567 13'8 2 634 11 2 700 36 2 754 38 2 583 10 2 947 7 3 128 11

70 3 054. 9 2 916 41 . 2 863 37 2 929 12 3 267 11 3 203 162 3 397 6 3 270 45 3 202 31 3 070 8 3 635 12 3 400 154 . 3 716 7 3 233 38 3 478 30 3 348 8 3 794 8 3 726 56 3 977 2 3 725 28' 3 800 27· ,3 959 6 4 305 13 .4 320 158 3 659 2 4 184 49 4 262 29 4 403' 4 4 527 9 5 032 16

80 4 529 4 4 611 31 4 560 28 5 470 1 . 5 453 4 5 051 222 4 562 1 4 641 28 4 603 18 4 696 4 5 472 10 5 589 17!J,. ,5 754 1 . 5 221 22 5 063 16 5' 000 1 . 5 823 6 6 119 66 :' 5 202 1 5 455, 24 5 470 15 6 190 1 6 018 4 6181 148 ·6 777 2 5 753 16 5 825 15 5 310 2 7'166 4 6 902 22

90 6 050 1 6 379 17 6285 11 7 302 5 7 231 142 6 072 1 7 023 10 7 006 5 6 564 3 8 201 1 .. 8 060 134 7 506 ' 8 8 208 6 ' . 9 381 2 8 543 96 ·7 576 2 7·844· 5 7 295 '10 .. 7 180 1 9 019 16,8 7 871

.6 7 519 3 . ' 9 516 12

100 9: 441 4 8 686 2 . 10 096 1 10 362 . 92 ' . 9 383 3 9 282 2 . 10502 2 10 167 9'.4 8. 396 .: 2 10 524 '2 '10 000 1 9 962 4 9 822 46 ; 9 622, 4 9· 227 '1 12 182 2 12 423 58 10 787 .. 3 10 518 5 11149 6

110 10 951 1 12 254 12 11 323 1 13 118 446 12 243 1 15 091 18

'.120

•

Table 6: Weight-Length relationships,log Wr = b log L - log k, for cod of Kiel Bay

I

MONTH!iI(log L) (logW) n b log k k

I

fraction of Ilr at length . ;aver. yield 1970/80 30 100 "" I"

FR Germany cm cm

255 9 5642100912 04063 0108281I "I I 1 7637 3 2696I . . • - . • .I 11 1.7983 3.3773 737 2.9445 -1.9179 .0121 .14 271 9 388I 111 1.7709 3.2993 188 3.0283 -2.0635 .0086 .12 256 9 797I IV 1.6490 " 2.8913 629 3.0761 '72.1810 .0066 .05 231 9 370

V 1.7109 3.1057 628 2.9685 -1.9730 .0106 .04 257 9 169lVI 1 ~ 6552 2.9467 " 911 2.9404 -1.9204 .0120 .04 265 9 120

VII 1.6459 2.9129 799 2.8472 -1.7733 .0169 .04 271 8 362IVIII 1.7209 3.1350 1816 2.8167 -1.7122 .0194 .05 281 8 341, IX 1.6767 2.9857 1402 2.9885 -2.0250 .0094 .05 244 8 915I X 1.7255 3.1488 604 2.7021 -1.5137 .0306 .07 300 7 761

XI 1.6844 3.0536 524 3.0141 -2.0233 .0095 .09 269 10 137XII 1.7360 3.2073 626 3.0739 -2.1291 .0074 .10 257 10 400

band log k 2.9283 -1.9035 .0125 and therefrom 264 8 985weighted acc. to n

band log k 2.9700 -1.9682 .0108 "and therefrom 263 9 406weighted acc. to yield

(log L) and (lo~W) are averages in the sampIes

•

- 19 -

( 5 )

1.2

•

1.1

Wr- li)WQ

1.2

1.1

Figure 1: Round weight/gutted weight ratio of cod for whichboth measures have been ascertained from identicalfish (i) versus the same ratio from seperate fish(s)

- 20 -

o • ·0·••1.18 •

0

0C

• WHOLE•• SIZE..

RANGE• 0

i •1.10

1.409 0

•

•

Wr0

'Na • •• 00 ••

1.16 • 0 • 8

• SIZES• • 0 ~40cm

1.12 i ••

1.409 •0

1.08

•

•

•o • 0 ••

• 0 A1.12 0 • ••• 0• 0 SIZES• ~32cm

1.08•

2 4 6 8 10 12 MONTHS

Figure 2 : Seasonal course of round weight / gutted weight quotient• monthly, 0 bimonthly averages, 15 months 1970/71

6

MON Tti

4212

- 21 -

J

10

Figure 4: Intercept, a, of round weightjgutted weightregression versus month, from Table 2

9

o

Q

10

- 60

- 40

- 20

- 22 -

WrKG

..

10.0

8.0

0. oe

o G)

WrATLEN GTH100 em

0.4

<:> G e e Wr ATG) <:> G e G) Q LENGTH(j) 0

0.2 30 cm

MONTHS

2 4 & 8 10 12

Figure 5 : Seasonal variation of weight at length 30 cm and 100 cmas calculated from relationsh1ps in Table 5

'. ;'" '~l ",",' .