Hylen, Arvid

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Discarding of fish in North-East Atlantic

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International Council for the Exploration of the Sea c • M. 1 967 IF: J ,,S ~ Demersal Fish (W.~rthern) Committee Introduction Discarding of fish in North-East Atlantic by Arvid Hylen Institute of Harine Research, Bergen Discarding of cod and haddock have been given for Norwegian trawlers fishing in North-East Atlantic on an experimental basis with slightly different chafers (Hylen 1965 and 1967). An ag]ceement with NOr\\Tegian trawler companies made it possible to study the discarding in Nowember \ 1965, and 1966, and in June - July 1967. The method for estimating discard described by Hylen (1967), '\Tas usedl The trawler was fishing from 28 November to 6 Dece~ber 1965 at the Skolpen Bank with a double ulstron cOG-end of mesh size 121.6 mm. An old cod-end of the same material with mesh size 124.8 mm ,.,ras used as chafer. The length of the cod-eno was 46 meshes, while the chafer covered 25t meshes of the posterior part of the cod-end. It was tightly laced knot by knot to the cod-end along the anterior and posterior sides. Alltogether 29 haul were made during the trip, while cod and haddock were measured from 22 hauls. About 64 and 76 percent of the total cat,ch of cod and hadcock were measured respectively. Few cod and haddock smaller than 35 cm were caught and no fish were discarded. Discarding of fish were studied 12-19 November 1966 onbord the same trawler. At this time the trawler was fishing on the Kildin Bar~ and East Bank. The trawler made alltogether 30 hauls with a small Granton trawl made of Courlene fitted with a double cod-end made of twaine. The mesh size of the cod-end and the chafer ... ,rere about 130 nun. Half a basket of small cod and hadc:,ock were discarded at sea during this trip, and the discarGing rate in weight was less than half a percent for both cod and haddock (Table 1). Trawler B were fishing the 4-12 November 1966 in the same area, and this trawler made 46 hauls 1-vi th a small Granton trawl of ulstron fitted with double cod-end made of ulstron. The mesh size was about 130 mm, both in t'he cod-end and in the chafer. The number of cod and haddock discarded, were recorded for 18 hauls, and the discarding rate in numbers for cod and haddock were estimated to 1.2 and 1.8 percent respectively (Table 2A). - 2 -The discarding rate in weight could not be estimated for the same hauls, since discarded fish were or~y recorded in numbers.--Discarding in weight -', were recorded for some other hauls, and th~te of d;iscarded cod and . ----haddock for these hauls were estima±ed to 1.7 and 5.5 percent respectively. (Table 2 p). The discarding practise were studied in June 1967 onbord trawler C fishing albng the East- and West-Coast of Finnmark. Nineteen hauls were made in the East-Finnmark area, but the discarding were studied in 16 hauls. This trawler used a single ulstron cod-end with mesh size about 130 mm. Cod discarded from this trawler was estimated to 25 percent in number and 10 percent in weight, while the discarding rates of haddock 'l.>vere estimated to 8Ii- 8.n'~" 5;,) ;:·~rcent respectively (Table J). The discarding rates of' cod for the sane trawler fishing at West-Finnmark were about 8 percent in number, which are similar to the discarding rata estimated for trawler B fishing in the same area (Table 3). The discarding rate in weight could not be estimated for the trawler; because the discarded fish were only recorded in numbers. However; when using the same average weight as for cod Giscardedat East-FinnmarkJ the rates are estimated to 1-2 percent. The discarding rates of hadc,ock for trawler C fishing in June at the llTest-Finnmark Coast 1;-rere estimated to 82 percent in number and 61 percent in weight, while the rates estimated for the trawler D fishing in July in the same area are J percent in number and 1 percent in weight. The discarding of boalfish from the two trawlers studied in 1967 were negligible. (Table 2). Good catches of redfish were only taken by trawler C at the vlest Coast of Finnmark (Table 3). The d:iscarding rate for this tbmvler is estimated to 14 percent in weight, while trawler D discarded 92 percent in the same area. Trawler C fishing in June at the East-Finnmark Coast discarded 28 percent of the catch in w-eight. Discussion The 50 percent retaining length for landing of cod taken in June 1967 by trawl at the East-Fip~mark Coast is estimated to 43 cm, and the 25-75 percent selection range for landing is 6 cm. Corresponding figures for trawlers fishing in May 1965 in the same area were 45 cm and 3 cm respectively (Hylen 1967). Differences in discarding rates for trawlers fishing in 1967 at the West-Finnmark Coast might have been caused by differences in size composition of the populations in the 2r;ea fished. ~~ile tra~ler D was fishing near the coast, trawler C was fishing some distance away. lFnfortunately the size composition of the catches could not be given. - 3 -Differences in the prises paid for the fish, might have affected the discarding rates too (Hylen 1967). vllien smaller fish are paid less than the bigger, the latter are preferred for landing. Hylen, A. " " References Utkast av torsk fra tralfangster. Fiskets Gang 51: 433-435 On the estimation of cod and hadcock discarded by trawlers using different chafers. Coop.Res.Rep. CoperJi. 1966: 65~77 Table 1. Fish landed and discarded by trawler A fishing 12 - 19 November 1966 on Kildin Bank and East Banki Species Landings T kg Cod 1 19593 I Haddock i 2531 Digcards kg 10 10 Percent discarded 0~05 0.04 ---r-! I I I I Table 2 A. Fish landed and discarded by _ trawler B fishing 4 - 12 November 1966 . on Kilding Bank and ~ast Bank~ 1------- Species \ --l,-a~~gs--·1 I Cod '\' 11703 \ t'iscai-ds NO : Percent . discarded ! 143 132 \ Haddock 7047 ! ~-------________ I_________ --.-JI ___ ~ ______ ----1 __ 1.2 11 1 .. 8 _________ 1Table 2 B. Species I Landin<l'S 1 kg: 8 Cod \ 4980 . ____ Haddo~.~ __ l_~~_~~ ______ ._. __  Discards kg 85 85 Percent NO 1.7 5 0 5 , ,---. ~ --_ .. _----- ----_._-----.---Table 3~ Fish landed and discarded by traw"lers fishi:1.g in 1967. r--, I Trawler Cod I 'C l,c ID I I ! Haddock C C D I Coalfish le Ig jRedfish le IC ID Locality I Date I , I Landings j Discards I Percent discarded 11 NO 1 Kg I NO ; Kg j NO i Kg I .----!-- -r------r------, --....,---------~-------·----i I I ! I I I 1 East-Finmark110-13 June 1 West-lfinmarlG 14-21 June If If ! 7 -13 July East-Finmarkil0-13 June West-Finmark/14-21 June If f1 ! 7-13 July ! j East-FinmarkllO-13 June "West-Finmark!14-21 June " If /17-13 July i i East-Finmark)10-13 June West-Finmark!14-21 Jtily 11 tl ! 7-13 July i 111831 18899\ 36701 2129 i 24.7 I 10.1 ( 54601 11521i 447! 259! 7.6 \1 2.2 , 4794\ 1351912811 16315.5 I 1.2 i I ! I,'. J I I 165 770 3795 1364 43522 31770 ! ; 1 ! -' - I i 1 Ill. " j ! r251; 861'! 362183.9 ! 59.1 i 1170 :11 3501j 18551 82.0 i 61.3 I 5768 1161 6111 3.0! 1.1 i I I I j ! I' 1590 1 8730 177 I I I l ,; i 0 I I ! 25, 0.06 ! i t 16! U,05 I I \ I 1 I J I j I I I 3~{~11 III i!: i I ! I ! i 1992: 91.8 /1 ! } I ----'-----------'----------'-----______ --..c- , .+-___ . __ ; 

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Discarding of fish in North-East Atlantic

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