BY-CATCH AND DISCARDS OF THE EUROPEAN PURSE SEINE

TUNA FISHERY IN THE INDIAN OCEAN.

CHARACTERISTICS AND ESTIMATION FOR THE 2003-2007 PERIOD

AMANDE Justin Monin(1), ARIZ Javier (2), CHASSOT Emmanuel(3), CHAVANCE Pierre(3), DELGADO de Molina

Alicia (2), GAERTNER Daniel(3), MUROA Hilario (4), PIANET Renaud (5), RUIZ Jon (4)

1) Centre de Recherches Océanologiques (CRO), Abidjan, Ivory Coast2) Instituto Espanol de Oceanografia (IEO), Tenerife-Canary Island,

Spain3) Institut de Recherches pour le Développement (IRD), Centre de

Recherche Halieutique Méditerranéenne et Tropicale (CRH), Sète, France

4) AZTI Tecnalia, Herrera Kaia, Portualde z :g, 20110, Pasaia (Gipuzkoa), Spain

5) Institut de Recherche pour le Développement (IRD) at Seychelles Fishing Authority (SFA), Victoria, Seychelles

Introduction

Importance of bycatch and discards issuesTerminology

Tuna discards (major tunas and small tunas)Bycatch (associated species discarded or

valorized)Objectives :

EstimationMain characteritsics

• Species composition• Length and sex structure• Utilisation

Data and Methods (1 of 4)

Data Collection Regulation (Reg. 1543/2000 and 1639/2001)

France (IRD), Spain (AZTI, IEO)10 % coverage targetedMethods (Observer programs)

Route and environment Fishing operation Tuna length structure tuna Associated species biological and length characteristics Floating device

Data and Methods (2 of 2)

Spain started in 2003 and France in 2005Preparation of data. FAD, FSC, Msm (5 miles)Extrapolation

Stratification• Quarter• Fishing mode (FAD, FSC, MSM)• Zone ET (“Echantillonnage thonier”)• Estimation for large groups of species (discarded

tunas, billfishes, fishes, sharks, rays)

Confidence interval by re sampling method

Results• Data coverage

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Sets in the fishery (FR+SP)

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Fig 1 : Number of observed sets in the Spanish and French observer program by year and percent coverage of the total fishing effort

Results• Data coverage

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Figure 2 : Observed sets by quarters and percent coverage

• Data coverage

Figure 3: Number of observed sets by type (free set BL, log set BO and submarines mounts Msm)

Figure 4: Number of sets by quarters and by zone ET

Data coverage

YearFishing mode 1 2 3 4

Total observed

setsSets in the

fishery (FR+SP)Coverage

(%)

BL 37 1 5 43 4116 1.042003 BO 15 14 34 63 3550 1.77

MsM 6 6 89 6.74Tot 58 15 39 112 7755 1.44BL 4 28 32 5156 0.62

2004 BO 1 28 101 31 161 3463 4.65MsM 9 1 10 86 11.63tot 5 28 138 32 203 8705 2.33BL 13 65 65 143 6005 2.38

2005 BO 29 49 44 114 236 4498 5.25MsM 2 2 4 85 4.71Tot 29 62 111 181 383 10588 3.62BL 79 42 9 12 142 5825 2.44

2006 BO 10 53 79 151 293 5326 5.50MsM 6 6 146 4.11Tot 89 95 88 169 441 11297 3.90BL 59 126 86 131 402 4856 8.28

2007 BO 42 52 130 185 409 5136 7.96MsM 1 7 8 84 9.52Tot 101 179 223 316 819 10076 8.13BL 142 218 189 213 762 25958 2.94

2003-2007 BO 82 197 368 515 1162 21973 5.29MsM 0 7 18 9 34 490 6.94Tot 224 422 575 737 1958 48421 4.04

Sets in the fishery (FR+SP) BL 9119 7631 3718 5490 25958

BO 4233 3870 7255 6615 21973MsM 133 110 92 155 490Tot 13485 11611 11065 12260 48421

Coverage % 1.66 3.63 5.20 6.01 4.04%BO 31.39 33.33 65.57 53.96 45.38

Observed sets/quarter

ExtrapolationTable II : By-catch estimation by species group in terms of tons, percentage and tuna production ratios

Table IISpecies group

Tuna discards

Fishes Sharks Billfishes RaysTotal

observedTotal

fishery

  tons 3 115 1 954 586 108 20 5 783 173 373

FAD % 53,9% 33,8% 10,1% 1,9% 0,3% 100,0% 

  t/1000 t 18,0 11,3 3,4 0,6 0,1 33,4 

  tons 4 352 91 48 45 41 4 577 117 293

FSC % 95,1% 2,0% 1,0% 1,0% 0,9% 100,0% 

  t/1000 t 37,1 0,8 0,4 0,4 0,3 39,0 

  tons 122 1 1 2 3 129 2 734

MsM % 94,6% 0,8% 0,8% 1,6% 2,3% 100,0% 

  t/1000 t 44,6 0,4 0,4 0,7 1,1 47,2 

  tons 7 589 2 046 635 155 64 10 489 293 401

Total % 72,4% 19,5% 6,1% 1,5% 0,6% 100,0% 

  t/1000 t 25,9 7,0 2,2 0,5 0,2 35,7 

Total bycatch by species groups

Extrapolation

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Tuna discards

Figure 7: Estimates of tuna discards and other by-catch by quarters for the European purse seine fishery

Extrapolation

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FSC FAD MsM FSC FAD MsM FSC FAD MsM FSC FAD MsM FSC FAD MsM

Tuna discards Billfishes Finfishes Sharks Rays

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Figure 6: Mean by-catch (tons) and 97 % confidence intervals by species group and fishing mode

Extrapolation

Figure 8: By-catch and discards estimation for the European purse seine fishery (raising factor based on tuna production) by zone ET

Total PS billfishes catch (tm)

Species composition according to the fishing mode

Total PS billfishes catch by species

Black marlin size distribution

Striped marlin size distribution

Sailfishes size distribution

Fate of caught billfishes

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100%

Makaira indica Makairanigricans

Famille desIstiophoridés

Istiophorusplatypterus

Tetrapturusangustirostris

Tetrapturusaudax

Xiphias gladius Total number

Discarded alive

Discarded dead

Indetermined

Valorized

Thank you