Assessment of the Selective Properties and Optimization of Mesh Size of Pelagic Trawl Codends, Used for Fishing Mackerel (Trachurus Spp) in the Gulf of Guinea
- 1 Department of Fisheries, Faculty of Industrial Engineering, University of Douala, Douala, Cameroon
- 2 Department of Fisheries, Faculty of Industrial Engineering, University of Douala, Douala, Cameroon
- 3 Department of Fisheries, Faculty of Industrial Engineering, University of Douala, Douala, Cameroon
Abstract
Over the past few decades, it has become widely recognized that the management strategies of world fisheries must ensure sustainability of target species. The intervening years have seen many improvements to the concept of gear se lectivity and methods for measuring the selectivity of fishing towed gears. Improved understanding of the principles of the selection of fish by gears has changed the list of parameters which are known to have a significant effect upon se lection. The recent development of new mathematical models and the increased availability of powerful computers have resulted in improvements in the analysis procedures for the data produced to measure a gear ’ s selectivity. The catch of mackerel in the gulfofGuineahas steeply declined during the last two decades, and resource management is clearly required. Therefore, the need for evaluation of trawl codends used in this fishery and the potential improvements to their selectivit y are of prime importance. In this paper, we use semi-empirical models to define selective properties of pelagic trawl codends targeting black mackerel (Trachurus spp) in theGulfofGuinea. These properties are determined using the experimental and theoretical methods of assessing the parameters of the selectivity curve, and by plotting the curve. Selection parameters were obtained by fitting a logistic equation using a maximum likelihood method. Trawl codend selectivity is estimated for 17 internal diamond mesh sizes in the range 47 - 79 mm . Using the basic selectivity equations, we determine the needed mesh size A = 58 mm for fishing mackerel in the gulf of Guinea. This nominal mesh size gives room for n j = 0 . 1 catch of juveniles, which not exceeds the allowable proportion [ n j ] = 0 . 1. To provide resource conservation, there is the need to make amendments in the fishery regulations for more rational exploitation of mackerel stoks, because the currently use nominal mesh size A = 56 mm is rather unselective.
- FAO, “The State of World Fisheries and Aquaculture,” FAO Fisheries and Aquaculture Department, Rome, 2009.
- P. N. Meke, “The Sustainable Management of the Marine Fish Resources in Cameroon: A Bioeconomic Analysis of the Trawl Fishery,” Ph.D. Thesis, University of Douala, Douala, 2012.
- M. K. Broadhurst, R. B. Millar, S. J. Kennelly, W. G. Macbeth, D. J. Young and C. A. Gray, “Selectivity of Conventional Diamond and Novel Square Mesh Codends in an Australian Estuarine Peneid Trawl Fishery,” Fisheries Research, Vol. 67, No. 2, 2004, pp. 183-194. doi:10.1016/j.fishres.2003.09.043
- R. B. Millar and R. J. Fryer, “Estimating the Size Selection Curves of Towed Gears, Traps, Nets, and Hooks,” Review in Fish Biology and Fishery, Vol. 9, No. 1, 1999, pp. 89-116. doi:10.1023/A:1008838220001
- C. Kvamme and B. Isaksen, “Total Selectivity of a Commercial Cod Trawl with and without a Grid Mounted and Codend Selectivity of North-East Artic Cod,” Fisheries Research, Vol. 68, No. 1-3, 2004, pp. 305-318. doi:10.1016/j.fishres.2003.11.011
- A. V. Melnikov and V. N. Melnikov, “Fishery Selectivity,” ASTU, Astrakhan, 2005.
- P. G. He, “Selectivity of Large Mesh Trawl Codends in the Gulf of Maine: I Comparison of Square and Diamond Mesh,” Fisheries Research, Vol. 83, No. 1, 2007, pp. 44-59. doi:10.1016/j.fishres.2006.08.019
- A. P. Njomoue, “Improvement of Pelagic Trawl Fishing in the Gulf of Guinea,” Ph.D. Thesis, VNIRO, Moscow, 2002.
- A. V. Melnikov, “Calculation-Experimental Research Methods on Selective Properties and Justification of Mesh Size on the Concentrating Parts of Entangling Fishing Gears,” Research on the Industrial Fishing Techniques, Collection of VNIRO Scientific Papers, 1983.
- R. P. Frandsen, N. Madsen and L. A. Krag, “Selectivity and Escapement of Five Commercial Fishery Species in Standard Square and Diamond-Mesh Codends,” ICES Journal of Marine Science, Vol. 67, No. 8, 2010, pp. 1721-1731. doi:10.1093/icesjms/fsq050
- F. G. O’Neill and R. J. Kynoch, “The Effect of Cover Mesh Size and Codend Catch Size on Codend Selectivity,” Fisheries Research, Vol. 28, No. 3, 1996, pp. 291-303. doi:10.1016/0165-7836(96)00501-2
- A. I. Chevchenko, “Rational Trawl Fishing Technology of Pollock,” Food Indutry, Moscow, 2004.
- D. A. Wileman, R. S. T. Ferro, R. Fonteyne and R. B. Millar, “Manuel of Methods of Measuring the Selectivity of Towed Gear,” ICES Cooperative Research Report, Vol. 215, 1996, p. 126.