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					                                                MariFish Work Package 7 Meeting
                                                         Norwich, UK
Sea Fisheries Institute                                June 12 - 13, 2008
   Gdynia, Poland




          The turned through 90° (T90)
          meshes cod-end construction

       - the best way for substantial reduction of bycatch and
                              discards -




                                                             Waldemar Moderhak
                                                          MariFish Work Package 7 Meeting
                                                                   Norwich, UK
                                                                 June 12 - 13, 2008


Sea Fisheries Institute
   Gdynia, Poland




                              Introduction
            The idea of such a codend construction was first presented in
  1993 at the Annual Science Conference of the ICES in Dublin and then
  published. The investigations on characteristics of selective cod-ends with
  meshes turned 90 (T90) have been carried out by Sea Fisheries Institute,
  Gdynia, Poland since 1996 and then in close co-operation with vTI
  Institute of Baltic Sea Fisheries, Rostock, Germany (former Institute for
  Fishery Technology and Fish Quality, Hamburg). From year 2006, T90
  codend is a legal design in the Baltic Sea cod fishery.


                                                                            Waldemar Moderhak
                                                                     MariFish Work Package 7 Meeting
                                                                              Norwich, UK
                                                                            June 12 - 13, 2008

Sea Fisheries Institute
   Gdynia, Poland




                COUNCIL REGULATION (EC) No 2187/2005
                                   of 21 December 2005
       for the conservation of fishery resources through technical measures in the
       Baltic Sea, the Belts and the Sound, amending Regulation (EC) No 1434/98
       and repealing Regulation (EC) No 88/98




                                                                               Waldemar Moderhak
                                                              MariFish Work Package 7 Meeting
                                                                       Norwich, UK
                                                                     June 12 - 13, 2008


  Sea Fisheries Institute
     Gdynia, Poland


                            Construction
       The construction of the turned meshes (T90) is based on typical diamond
netting but that has to be turned through 90. Therefore, the production of
netting for cod-ends with meshes turned does not require any changes in
machinery or production technology in net factories. The shapes of diamond
and turned through 90 meshes are presented (a - diamond, b - T90).




                                                                             Waldemar Moderhak
                                                                                                MariFish Work Package 7 Meeting
                                                                                                         Norwich, UK
                                             T90 mesh opening calculation                              June 12 - 13, 2008

                                                       model
Sea Fisheries Institute
   Gdynia, Poland
                                             P
                                      q                              x            f ( l ,q , P , x )
                                                               y                                             dx
                x
                                                    M                0
                                                                         2  E  J    f ( l , q , P , x )
                                                                                       2                         2



                                  l

    where:
                                                                               Flexural
    y – mesh bar bend,
                                                                                rigidity
    l – mesh bar length,
    q – continuous load from hydrodynamic pressure acting on
        the mesh bar,
                           2
                                                           p
             p                   l d c    and       q
                          2                                l
    p – hydrodynamic resistance force on the mesh bar,
    ρ – water density,
    ν – water velocity,
    d – mesh bar thickness (diameter),
    c – hydrodynamic force coefficient,
    P – concentrated force acting on the end of the mesh bar,
    x – current coordinate,
    E – modulus of elasticity (Young’s modulus),
    J – moment of inertia of the mesh cross-section,
    f (l, q, P, x) – functions dependent on bending forces and moments set acting on the mesh bar
                                                                                                          Waldemar Moderhak
                                                                                                                                   MariFish Work Package 7 Meeting
                                                                     T90 mesh bar shape                                                     Norwich, UK
                                                                                                                                          June 12 - 13, 2008
                                                                   for three different twines
Sea Fisheries Institute
   Gdynia, Poland                                                                                             Deviation [m]
                                                          0,000   0,005   0,010   0,015       0,020   0,025
                                                  0,000



                                                 0,005



                                                 0,010



                                                 0,015



                                                 0,020



                                                 0,025



                                                 0,030


                                                                                                                       Twine "a"
                                                 0,035
                                                                                                                       Twine "c"
                                                                                                                       Twine "b'

                                                 0,040
                          Bend of mesh bar [m]




                                                 0,045                                                P


                                                                                  P       P
                                                 0,050
                                                                                                              M

                                                 0,055                                M
                                                                                                M
                                                                                                                                             Waldemar Moderhak
                                                                           MariFish Work Package 7 Meeting
                                                                                    Norwich, UK
                                                                                  June 12 - 13, 2008
 Sea Fisheries Institute          Force acting on the section of netting
    Gdynia, Poland
                                     with meshes turned 90 – T90




 P  P p
                      i

    i         0            i
                      1



 i  1,2 ,3 ,.....n  1, n

where:
Pi – concentrated force acting
on the end of the mesh bar
of i-th row of meshes
P0 – initial concentrated force
pi – hydrodynamic force acting
on the mesh bar of i-th row of
meshes




                                                                                 Waldemar Moderhak
                                                                                                MariFish Work Package7Meeting
                                              The mesh shapes                                            Norwich, UK
                                                                                                       June 12 - 13, 2008
                                   of the codend, extension and belly end
Sea Fisheries Institute
   Gdynia, Poland




                                                                        thickness d = 4.6 mm
                          codend
                                                    Codend
                                                    last row




                                                     Extension
                                                      first row




                          extension
                                                                            thickness d = 4,43 mm




                                                  Extension
                                                   last row




                                                  Belly
                                                first row
                                                                        thickness d = 3,55 mm
                          belly


                                                                                                             Waldemar Moderhak
                                                                                     MariFish Work Package7Meeting
                                                                                              Norwich, UK
                                                                                            June 12 - 13, 2008

Sea Fisheries Institute
   Gdynia, Poland                        Shapes of codend and extension T90
                                              made of the same netting




                          mesh opening   109,9 mm,   twine thickness   5,0/4,35 mm




                                                                                              Waldemar Moderhak
                                                                                    MariFish Work Package7Meeting
                                                                                             Norwich, UK
                                                                                           June 12 - 13, 2008
Sea Fisheries Institute
   Gdynia, Poland

                                 Shapes of codend and extension T90 made
                                             of different netting:


                 mesh opening  109,9 mm,                  mesh opening   107,3 mm,
              twine thickness 5,0/4,35 mm         twine thickness 3,5/3,30 mm –double twine




                                                                                            Waldemar Moderhak
                                                                                                              MariFish Work Package 7 Meeting
                                                                                                                       Norwich, UK
                                                                                                                     June 12 - 13, 2008

Sea Fisheries Institute
   Gdynia, Poland
                                                                      Selection curves
                                                             for L50 =38 cm and four different SR


                                      1

                                                                                  MLS
            Retention coefficient




                                    0,75


                                                                                                                 SR = 12 cm
                                     0,5                                                                         SR = 9 cm
                                                                                                                 SR = 6 cm
                                                                                                                 SR = 3 cm

                                    0,25



                                                              100%         77% 53% 30%
                                      0
                                           0   5   10   15      20    25     30   35     40   45    50   55    60      65      70

                                                                                                                      Length [cm]




                                                                                                                         Waldemar Moderhak
                                                                                                                          MariFish Work Package 7 Meeting
                                                                                                                                   Norwich, UK
                                                                                                                                 June 12 - 13, 2008
                                                               Selectivity investigation
Sea Fisheries Institute
   Gdynia, Poland                                          of the T90 codend 08 – 09.2006
                                                                       Polish investigations


                          0,11
              Frequency




                                                MLS
                          0,10




                          0,09




                          0,08
                                                                      Cover


                          0,07




                          0,06




                          0,05                                                 T90 codend


                          0,04




                          0,03




                          0,02




                          0,01




                          0,00
                                 20




                                      25




                                           30




                                                 35




                                                      40




                                                            45




                                                                 50




                                                                          55




                                                                                60




                                                                                       65




                                                                                            70




                                                                                                 75




                                                                                                      80




                                                                                                           85




                                                                                                                90




                                                                                                                     95




                                                                                                                              100




                                                                                                                                       105




                                                                                                                                                  110
                                                                                                                                    Length [cm]




                                                                                                                                        Waldemar Moderhak
                                                                                                                                        MariFish Work Package 7 Meeting
                                                                                                                                                 Norwich, UK
                                                                                                                                               June 12 - 13, 2008

Sea Fisheries Institute
   Gdynia, Poland                                              Length distribution
                                                    of cod caught with a T90 codend – 12.2006
                                                                               Polish investigations


                                 75
                Number of fish




                                                                    MLS
                                 70
                                 65
                                 60
                                 55
                                                cover
                                 50
                                 45
                                                                                                     codend
                                 40
                                 35
                                                                                                     Marketable cod escaped
                                 30
                                 25
                                 20
                                 15             Undersized cod retained
                                 10
                                 5
                                 0
                                      15   20      25        30           35     40      45     50         55        60       65   70        75       80
                                                                                                                                            Length [cm ]




                                                                                                                                                   Waldemar Moderhak
                                                                                                                                                            MariFish Work Package 7 Meeting
                                                                                                                                                                     Norwich, UK
                                                                                                                                                                   June 12 - 13, 2008

Sea Fisheries Institute
                                                                   Selectivity investigation (total)
   Gdynia, Poland                                                   – CODENDS and COVER –
                                                                                 German investigations



                                0,07
                                                            MLS
                    Frequency




                                0,06
                                                                                                      r.v. SOLEA - Apr. 2008
                                0,05

                                                                                                                                       Bacoma - 112,4 mm
                                0,04
                                                                                                                                       T90PAD - 112,9 mm
                                                                                                                                       T90PED - 109,0 mm
                                0,03
                                                                                                                                       T90PES - 112,9 mm

                                0,02


                                0,01


                                0,00
                                       15,5

                                              20,5

                                                     25,5

                                                            30,5

                                                                   35,5

                                                                          40,5

                                                                                 45,5

                                                                                        50,5

                                                                                               55,5

                                                                                                        60,5

                                                                                                               65,5

                                                                                                                      70,5

                                                                                                                             75,5

                                                                                                                                    80,5

                                                                                                                                           85,5

                                                                                                                                                  90,5

                                                                                                                                                         95,5

                                                                                                                                                                  101

                                                                                                                                                                        106
                                                                                                                                                                Length [cm ]
                                                                                                                               MariFish Work Package 7 Meeting
                                                                                                                                        Norwich, UK
                                                                                                                                      June 12 - 13, 2008
                                                            Selectivity investigation
Sea Fisheries Institute
   Gdynia, Poland                                               – CODENDS -
                                                                    German investigations



                                0,10
                    Frequency




                                0,09                               MLS

                                0,08                                                           r.v. SOLEA - Apr. 2008

                                0,07

                                0,06

                                0,05                                                                         Bacoma - 112,4 mm
                                                                                                             T90PAD - 112,9 mm
                                0,04
                                                                                                             T90PED - 109,0 mm
                                0,03                                                                         T90PES - 112,9 mm

                                0,02

                                0,01

                                0,00
                                       15,5


                                              20,5


                                                     25,5


                                                            30,5


                                                                         35,5


                                                                                40,5


                                                                                       45,5


                                                                                              50,5


                                                                                                     55,5


                                                                                                            60,5


                                                                                                                   65,5


                                                                                                                            70,5


                                                                                                                                     75,5
                                                                                                                          Length [cm ]
                                                                                                                               MariFish Work Package 7 Meeting
                                                                                                                                        Norwich, UK
                                                                                                                                      June 12 - 13, 2008

Sea Fisheries Institute
   Gdynia, Poland
                                                           Selectivity investigation
                                                                 - COVER –
                                                                   German investigations




                                      0,10
                                                                               MLS
                          Frequency




                                      0,09                                                        r.v. SOLEA - Apr. 2008
                                      0,08

                                      0,07

                                      0,06                                                                   Bacoma - 112,4 mm

                                      0,05                                                                   T90PAD - 112,9 mm
                                                                                                             T90PED - 109,0 mm
                                      0,04
                                                                                                             T90PES - 112,9 mm
                                      0,03

                                      0,02

                                      0,01

                                      0,00
                                             15,5



                                                    20,5



                                                            25,5



                                                                        30,5



                                                                                 35,5




                                                                                           40,5



                                                                                                      45,5



                                                                                                                  50,5



                                                                                                                            55,5



                                                                                                                                       60,5
                                                                                                                            Length [cm ]
                                                                         MariFish Work Package 7 Meeting
                          Selectivity curves of four different codends            Norwich, UK
                                                                                June 12 - 13, 2008
                                  German study - SOLEA April 2008
Sea Fisheries Institute
   Gdynia, Poland




                                 MO = 112,4 mm                                MO = 112,9 mm




                                                                               MO = 112,9 mm
                                MO = 109,0 mm
                               T90 codend shape - lifting strap too short –       MariFish Work Package 7 Meeting
                                                                                           Norwich, UK
                                                                                         June 12 - 13, 2008
                          study of the Academy of Agriculture, Szczecin, Poland
Sea Fisheries Institute
   Gdynia, Poland
                                                  MariFish Work Package 7 Meeting
                          Icelandic commercial             Norwich, UK
                                                         June 12 - 13, 2008
                          T90 codend with catch
Sea Fisheries Institute
   Gdynia, Poland




                                                   Sveinn Hjalmarsson
                                                             MariFish Work Package 7 Meeting
                             T90 codend in action                     Norwich, UK
                                                                    June 12 - 13, 2008
                          - German investigation, CLUPEA -
Sea Fisheries Institute
   Gdynia, Poland
                                                             MariFish Work Package 7 Meeting
                                                                      Norwich, UK
                              T90 codend in action                  June 12 - 13, 2008

Sea Fisheries Institute   - German investigation, CLUPEA -
   Gdynia, Poland
                                                                                                         MariFish Work Package 7 Meeting
                                                                                                                  Norwich, UK
                                                                                                                June 12 - 13, 2008

Sea Fisheries Institute
   Gdynia, Poland
                                           Advantages and disadvantages of
                                                  the T90 codends



                          Advantages:
                          - very good selective and protective properties (sharp selective curve)
                          - retain small number of fish juveniles
                          - small by-catch of other rounded fishes
                          - by-catch of flatfish comparable to that retained by diamond cod-end constructions
                          - better fish condition and thus better survive rate of fishes
                          - better quality of fish caught
                          - environmentally friendly fishing
                          - “clear” fishing, less work for a crew
                          - less fuel consumption and in consequence less air pollution
                          - improved catch abilities
                          - simple construction
                          - low price of turned (T90) cod-end
                          - stability during whole towing
                          - better breaking strength of turned netting
                          - easy netting availability
                          -very difficult to manipulate to reduce selectivity

                          Disadvantages:
                          - not recognised yet
                                                                                                                   Waldemar Moderhak
                                                                              MariFish Work Package 7 Meeting
                                                                                       Norwich, UK
                                                                                     June 12 - 13, 2008

Sea Fisheries Institute
   Gdynia, Poland




                                             Conclusion
                                 It may be stated that cod-end with meshes turned
                     90 (T90) can introduce a new level of selectivity, fish
                     protection and substantial reduction of by-catch and discards
                     in commercial fisheries. General idea of the turned (T90)
                     cod-ends can be applied for designing/constructing other
                     T90 cod-ends, with appropriate mesh sizes for particular fish
                     species for proper protection of these fish species.




                                                                                        Waldemar Moderhak
                                                                         MariFish Work Package 7 Meeting
                                                                                  Norwich, UK
                                 Thousands of herring meshed                    June 12 - 13, 2008

Sea Fisheries Institute
   Gdynia, Poland
                          in diamond belly netting, during cod fishing
                                      - T90 belly demand !! -




                                                                                   Waldemar Moderhak
                                         MariFish Work Package 7 Meeting
                                                  Norwich, UK
                                                June 12 - 13, 2008
Sea Fisheries Institute
   Gdynia, Poland




                              Thank you
                          for your attention



                                                       Waldemar Moderhak

				
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