Northwest Atlantic Fisheries Organization

Serial No. N055 NAFO SCR Doc. 80/11/23 (Corrigendum)

SPECIAL MEETING OF SCIENTIFIC COUNCIL - FEBRUARY 1980

Assessment of the Squid (Illex illecebrosus) Stock in Division 4W by the area-density method

by

M. LipinskiSea Fisheries Institute

Gdynia, Poland

In NAFO SCR Doc. 80/11/23, the area covered by Polish commercial

fishing operations in Div. 4W in 1979 was estimated by splitting the

division into small rectangles (0.5° x 0.5°), and assuming the area of

each rectangle to be 30 Nm x 30 Nm = 900 Nm2 = 3100 km2 . Due to the

effect of the Mercator projection, the area of each rectangle should be

30 Nm X 21 Nm = 630 Nm2 = 2161 km2 . •

This recalculation results in corrected estimates of the area

investigated and the squid biomass in 1979 as follows:

Total area = 11,885.5 km

Total biomass = 107,000 tons

NOT TO BE CITED WITHOUT PRIORREFERENCE TO THE AUTHOR(S)

Northwest Atlantic

Serial No. N055

Fisheries Organization

NAFO SCR Doc. 80/11/23

SPECIAL MEETING OF SCIENTIFIC COUNCIL- FEBRUARY 1980

Assessment of the Squid (INex illecebrosus) Stock inDivision 4W by area-density method

by

M. LipinskiSea Fisheries Institute

Gdynia, Poland

Introduction

The area-density method was previously used by the author/LipiAski, 1978; 1979/ for the assessment of Illex stocks inDiv, 4W. The use of this method as a routine prOcedure in rela-tion to the same Division in the consecutive years could probablyhip -rove our understanding of variations of squid abundance, andwould serve for current management deoisions as Val.

Polish Fleet flalRe4222rations in Div. 4W

The Polish Fleet fishing for squid in the Div. 4W consistedot five stern trawlers working with use of standard Polish mid-whoar trawl /MWT/. The stern trawlers operated also in Div. 3 0.

Fishing oil sqpid started on 4 July and finished o- D - tobez.Th© dotails of the Polish squid fishery in Div. 4W era shownin Fig. 1 and Table 1. These data were taken from logbooksof the vessels and therefore seem to be the best source availablefor further analysis.

The total Polish catch for Div. 4W amounted to 10,399 tons/pela„;ic trawls only/.The brea of Polish squid fishery in 1979 was generally similarto that previously described, but slightly smaller /17,050 km2instead of 18,600 km2 in 1978/. The area was equally fishedand sampled in the different periods of the season and it wasassumed that there was no need to split it into sub-areas A and B.The depth of fishing operations was 140-180 m and 1806-240 m.The mean duration of eaoh haul was slightly below 3 hours, meannumber of hauls per day equaled 4, trawl towing speed - 4.3 knots.The spread between the net wings was 35 m and an area coveredduring a single haul - 0.87 km2.

As it was shown in the previous paper AipiAski, 1979/

the assessment of males and females stocks separately in differentperiods of the season probably does not influence seriously the

2--

final result. Therefore mean length of 21,5 cm and mean weightof 190 g was assumed as appriopriate for the whole analyst.).The data on length and weight obtained in the field at the endof July, corresponded well with data of Lange and Johnson /1979/and Lipinski /1978/.It was found that Polish Fleet equally sampled the whole areawith time, therefore migration could not influente seriouslythe results of the assessment.

The mean catch per day was 31.3 t and remained relativelyconstant during the whole fishing period. This was equal to1.647 x 105 individuals.The mean density of squids per 1 km2 , extracted by net was0.473 x 10 individuals, and the total number of squids inthe area analysed was 8.065 x 108 individuals.

40masRRL1931191EARIPAAEILLEYIELledd

The total Polish catch in Div. 4W totalled 10,399 tons,i.e. 0.547 x 108 individuals. The ratio of this oatch to thetotal number of squids in the area investigated equalled:

-

0,547 x 108as 0.068

8.065 x 10°

Therefore the biomass was estimated at:

10,399 • 152,900 t.0.068

This is a slight increase of the biomass as comparedwith the 1978 estimate.

Discussion

The biomass of squid stooks in Div. 4W was relativelystable during 1977-1979 fishing seasons. It see= thereforethat the direoted squid fishery did not affeot seriouslythese stocks. Some biomass fluotuationa /if any/ oould berather explained by influence of natural faotors, as it wasin 1979 paper /LipiLski, op.oit./ disoussed.

Conclusion

A catch yield of 61,000 tons of Illex in Div. 41 does notseem to be excessive for the existing stook.

Literature Cited

Lange , A.M.T. and Karen. L.Johnson, 1979Doreal Mantle Length — Total Weight Relationships of Squid/Loligo pealei and Illex illeoebrosus/ from the NorthwestAtlantios off the Coast of the United States. =AP Res.Doo.79/11/4:37 pp.

Lipinski, N[.0978Stook assessment of Illex illeoebrosus Aesueur, 1821/in ICNAP Div. 4W determiusd by area.deneit, method. IONAY Res.Doo; 78/11/1087 PP;

1978Length—weight relationship of bile 111eoebrosus/Lesueur, 1821/ from Div. 4W. ICNAP W.P. 78/11/712 PP.

LipiAski,M., 1979Assessment of Illex illeoebrosus /Lesueur, 1821/Stooks in IMP Div. 4W determined b y areso.densit method.ICNAP Res.Doo. 79/11/37.

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Northwest Atlantic Fisheries Organization

Serial No. N055 NAFO SCR Doc. 80/11/23 (Corrigendum)

SPECIAL MEETING OF SCIENTIFIC COUNCIL - FEBRUARY 1980

Assessment of the Squid (INex iZZecebrosus) Stock in Division area-density

by

M. LipinskiSea Fisheries Institute

Gdynia, Poland

In NAFO SCR Doc. 80/11/23, the area covered by Polish commercial

fishing operations in Div. 4W in 1979 was estimated by splitting the

division into small rectangles (0.5° x 0.5°), and assuming the area of

each rectangle to be 30 Nm x 30 Nm = 900 Nm 2 = 3100 km2 . Due to the

effect of the Mercator projection, the area of each rectangle should be

30 Nm X 21 Nm = 630 Nm2 = 2161 km2..

This recalculation results in corrected estimates of the area

investigated and the squid biomass in 1979 as follows:

Total area = 11,885.5 km

Total biomass = 107,000. tons