Analysis on the body size selectivity for multi-species of discarding juvenile fishes in the bottom trawl

  • KIM, Yonghae (Institute of Marine Industry, Department of Marine Production Technology, Graduate School, Gyeongsang National University)
  • Received : 2019.07.05
  • Accepted : 2019.08.13
  • Published : 2019.08.31


Discarding juvenile fishes under girth 16 cm nearly equal to inner perimeter of codend mesh size collected by a cover net method in bottom trawl. The body size of the main five species (mackerel, horse mackerel, sea bream, melon seed and black throat seaperch) was measured for their body length, girth, weight, height and width and analyzed size selectivity. Frequency of penetrating fish as retention in a cover net was less than 40% of total number of juvenile discarding fish. The most of body length or girth of five species were significantly different between in the codend and in the cover net. The 50% selection girth in the cover net ranged 8-11 cm were smaller than those in the codend ranged 9-13 cm by the species respectively. The 50% selection body length was significantly related with the ratio of body height (H) by body width (W) both for in the codend or in the cover net while 50% selection girth was not significantly related with H/W. Furthermore 50% selection fish size by fish species between in the codend and in the cover net was not significantly different both in body length or girth. Therefore, the girth selectivity represented possibly as one unique value regarding fish body shape was considered as more useful method for multi-species catch in trawl.


Cover net;Discarding fishes;Multi-species;Body length and girth selectivity


  1. Beutel D, Skrobea L, Castroa K, Ruhle Sr P, Ruhle Jr. P, O'Gradyd J and Knight J. 2008. Bycatch reduction in the Northeast USA directed haddock bottom trawl fishery. Fish Res 94, 190-198. (DOI:10.1016/j.fishres.2008.08.008).
  2. Carol J and Garcia-Berthou E. 2007. Gillnet selectivity and its relationship with body shape for eight freshwater fish species. J Appl Ichthyol 23, 654-660. (DOI:10.1111/j.1439-0426.2007.00871.x).
  3. Chopin F and Suuronen P. 2009. The development of international guidelines on bycatch management and reduction of discards. ICES CM 2009/M:01.
  4. Cho SK, An HC, Shin JK, Yang YS and Park CD. 2005. Study on the development of trawl escapement device. J Korean Soc Fish Technol 41, 241-247. (DOI:10.3796/KSFT.2005.41.4.241).
  5. Daliri M. Paighambari, SY. Shabani MJ, Pouladi M and Davoodi R. 2012. Length-weight and length-girth relationships, relative weight and relative condition factor of four Commercial fish species of northern Persian Gulf. Ann Rev & Res Biol 2, 15-26.
  6. Glass CW and Wardle CS. 1995. Studies on the use of visual stimuli to control fish escape from codend. II. The effect of a black tunnel on the reaction behaviour of fish in otter trawl codends. Fish Res 23, 165-174.
  7. Herrmann B, Wienbeck H, Moderhak W, Stepputtis D and AhmKrag L. 2013. The influence of twine thickness, twine number and netting orientation on codend selectivity. Fish Res 145, 22-36. (DOI:10.1016/j.fishres.2013.03.002).
  8. Jawad LA, McKenzie A and Al-Noor SS. 2009. Relationship between opercular girth, maximum girth and total length of fishes caught in gillnets in the estuarine and lower river sections of Shatt al-Arab River (Basrah Province, Iraq). J Appl Ichthyol 25, 470-473. (DOI:10.1111/j.1439-0426.2009.01254.x).
  9. Jones EG, Summerbell K and O'Neill F. 2008. The influence of towing speed and fish density on the behaviour of haddock in a trawl cod-end. Fish Res 94, 166-174. (DOI:10.1016/j.fishres.2008.06.010).
  10. Kim YH. 2015a. Bycatch reduction by experimental shaking codend attached with canvas in a bottom trawl. Fish Aquat Sci 18, 325-332. (DOI:10.5657/FAS.2015.0325).
  11. Kim YH. 2015b. Analysis of body size selectivity of bycatch using the cover net method for a shrimp beam trawl. J Korean Soc Fsh Technol 51, 171-178. (DOI:10.3796/FSFT.2015.51.2.171).
  12. Kim YH, Wardle CS and An YS. 2008. Herding and escaping responses of juvenile roundfish to square mesh window in a trawl cod end. Fish Sci 74, 1-7. (DOI:10.1111/j.1444-2906.2007.01490.x).
  13. MacLennan D.N. 1992. Fishing gear selectivity: an overview. Fish Res 13, 201-204.
  14. Mendes B, Fonseca P and Campos A. 2006. Relationships between opercula girth, maximum girth and total length of fish species caught in gillnet and trammel net selectivity surveys off the Portuguese coast. J Appl Icthyol 22, 209-213.
  15. Miler RB and Fryer RJ. 1999. Estimating the size-selection curves of towed gears, traps, nets and hooks. Rev Fish Biol Fish 9, 89-116.
  16. Mituhasi T, Tokai T, Ercoli R, Garcia JC, Salvini L, Bartozzetti J and Roth R. 2000. Estimating codend selectivity and fish escapement from a cover net of an insufficiently small mesh size. Fish Sci 66, 327-333.
  17. O'Neill FG and Herrmann B. 2007. PRESEMO-a predictive model of codend selectivity - a tool for fishery managers. ICES J Mar Sci 64, 1558-1568. (DOI:10.1093/icesjms/fsm101).
  18. O'Neill FG and Kynoch RJ. 1996. The effect of cover mesh size and cod-end catch size on cod-end selectivity. Fish Res 28, 291-303.
  19. Ozekinci U. 2005. Determination of the Selectivity of Monofilament Gillnets Used for Catching the Annular Sea Bream (Diplodus annularis L., 1758) by Length-Girth Relationships in Izmir Bay (Aegean Sea). Turk J Vet Anim Sci 29, 375-380.
  20. Ozbilgin H. 1998. The seasonal variation of trawl cod-end selectivity and the role of learning in mesh penetration behaviour of fish. PhD thesis, University of Aberdeen, Scotland, UK. 206.
  21. Ozbilgin H and Tosunoglu Z. 2003. Comparison of the selectivities of double and single codends. Fish Res 63, 143-147. (DOI:10.1016/S0165-7836(03)00005-5).
  22. Pol MV, Herrmann B, Rillahan C and He P. 2016. Selectivity and retention of pollock Pollachius virens in a Gulf of Maine trawl fishery. Fish Res 184, 47-53. (DOI:10.1016/j.fishres.2015.07.029).
  23. Sala A, Lucchettia A, Perdichizzi A, Herrmann B and Rinelli P. 2015. Is square-mesh better selective than larger mesh? A perspective on the management for Mediterranean trawl fisheries Fisheries Research 161, 182-190. (DOI:10.1016/j.fishres.2014.07.011).
  24. Sala A, Lucchetti A and Buglioni G. 2007. The influence of twine thickness on the ize selectivity of polyamide codends in a Mediterranean bottom trawl. Fish Res 83, 192-203. (DOI:10.1016/j.fishres.2006.09.013).
  25. Santos MN, Canas A, Lino PG, Monteiro CC. 2006. Length-girth relationships for 30 marine fish species. Fish Res 78, 368-373. (DOI:10.1016/j.fishres.2006.01.008).
  26. Sea Grant. 2014. Fisheries Bycatch- Global issues and creative solutions. 29th Lowell Program and Abstracts, pp.106.
  27. Stergiou KI and Karpouzi VS. 2003. Length-girth relationships for several marine fishes. Fish Res 60, 161-168. (DOI:10.1016/S0165-7836(02)00077-2).
  28. Wardle CS. 1993. Fish behaviour and fishing gear. In: Behaviour of Teleost Fishes. 2nd Ed., Pitcher T.J. ed. Chapman & Hall, London, UK, 609-644.
  29. Wileman DA, Ferro RST, Fonteyne R and Millar RB. 1996. Manual of methods of measuring the selectivity of towed fishing gears. Copenhagen, ICES Coop Res Rep 215, 126.