Meijide-Cameselle, M. (Manuel)

Pérez-Contreras, M.N. (María Nélida)

English

Repositorio Institucional Digital del IEO

Working document to the Northem Pelagic and BIue Whiting Fisheries Working GroupDATA ON BLUE WHITING DlSCARDS IN SOUTHERN FISHERIESByManuel Meixide and Nélida PérezInstituto Español de Oceanografia.Apdo 1552.36280 Vigo. Spain.INTRODUCTIONThe lack of information on discards in the Southem area has been conunented in the past by the ACFM andby the former Blue Whiting Assessment Working Group. The amount of discards in this area was expectedto be high. A sampling program on discards was carried out in 1994, financed by the EU, in whichobservers on board sampled both retained catch and discards This paper presents the preliminary results ondiscards ofblue whiting, from the bottom trawl fleet, i.e. single and pair trawlers.RESULTSDiscards were estimated to be 62 % in weight in the single bottom trawlers and 22 % in the bottom pairtrawlers.As is shown in text table below, discards estimated by age were high in ages Oto 2 in the pair trawlers.(Fig. 1). In single trawlers the decrease of discards estimated in older ages was more smooth.I~,SINGLE TRA WL PAlR TRAWLAGE % D1SCARDED AGE %DISCARDEDo 95.5 o 98,71 74,7 1 94.82 60,0 2 27.83 54,2 3 4,04 45,9 4 1,55 37.2 5 0,86 28.0 6 0,07 21.3 7 0.08 18.3 8 0.09 21.6 9 0.010 15,7 10 0,011 15,9 11 0,012 12,5 12 0,0An exercise was made applying these discarding rates to the age composition of landings from the southemfisheries in 1995 , In this exercise the discarding rates of the Portuguese fleet were assumed to be thesame as estimated for the Spanish bottom trawl. Results are shown in text table below:DISCARDS ESTlMATlON IN 1995 ILANDlNGS SPAlN PORTUGAL:AGE Single Tmw1 Pair Traw1 Long line TrawlO 552 979 30 13511 19022 56859 13 201562 20739 87585 40 145923 10006 41427 134 35484 9143 26763 113 21345 10137 32064 106 17986 3982 13936 64 17547 1607 4086 63 6748 794 2652 18 2809 160 .531 37 6310 101 296 28 6711 120 83 6 12412 51 4 15 21CATCH SPAlN IPORTUGALAGE SingleTraw!JPairTrawllLongline ITrawlO 12193 76433 30 298651 75087 1095542 13 795642 51786 121301 40 364373 21864 43153 134 77534 16896 27161 113 39435 16134 32336 106 28626 5532 13938 64 24377 2043 4086 63 8578 972 2652 18 3439 204 531 37 8010 120 296 28 8011 143 83 6 14712 58 4 15 23DISCARDS SPAIN PORTUGALAGE Single Tmwll Pair Trawl Single TrawlO 11641 75454 285141 56065 1038683 594072 31047 33716 218453 11859 1726 42054 7753 398 18095 5997 272 10646 1550 2 6837 436 O 1838 178 O 639 44 O 1710 19 O 1211 23 O 2312 7 O 3CATCH SOlITHERN FISHERYAGE LANDINGS IDISCARDS ICATCHO 2912 115609 1185211 96049 1154156 12502052 122956 86608 2095643 55114 17790 729044 38153 9961 481145 44105 7333 514386 19737 2234 219727 6430 619 70498 3744 241 39859 791 61 85210 492 31 52311 333 46 37912 89 10 100DlSCUSSION AND CONCLUSIONSLandings of ages 0, 1 and 2 from the southem fisheries are 2% of the total blue whiting catch in numbersused in the assessrnent, and will increase to be 15% if estímated discards are include.í If t!1e sarnecalculation is made comparing landings ofthe same ages from the southem fisheties wirn ihecorresponding ages in the intemational catch in numbers, the obtained value is l3%., and will increase to91% including discards.As there is available only one single estimation of discards in this fleets, the evoluticn of this values in thepast is unknown , and the use of this values to correct the historical series could produce serious bias.In particular, the effects of changes in fisheries policy, market demand and variability of recruitment, canmodify the discarding rates in a way that make unwise to use a single estímate.Discards from Spanish Single Trawlers in1994(%)1008060~o4020OO 1 2 3 4 5 6 7 8 9 10 11 12AgeDiscards from Spanish Pair Trawlers in 1994 (%)100~806040202 3 4 5 6 7 8 9 10 11 12AgeFig. 1. Discards in Spanish bottom fleets. (single and pair trawlers).

Data on blue whiting discards in southern fisheries

Meijide-Cameselle, Manuel

Pérez-Contreras, María Nélida

Digital.CSIC

http://www.repositorio.ieo.es/e-ieo/bitstream/10508/9011/1/Meixide%2c%20M%20et%20al.%20Data.pdf

Data on blue whiting discards in southern fisheries

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