Estimating the selectivity of unpaired trawl data: a case study with a pelagic gear
DOI:
https://doi.org/10.3989/scimar.04409.26BKeywords:
trawl selectivity, pelagic fisheries, unpaired data, codAbstract
Most selectivity experiments employ either the covered codend or paired gear methods. It is not always possible, however, to use these methods. Owing to operational, biological and/or environmental considerations, there may be no obvious way or it may be inappropriate to pair the test and control data. Hence, it will not be possible to estimate the selectivity of the gear and its uncertainty using standard statistical methods. This study presents a methodology for analysing the selectivity of fishing gears from unpaired test and control data. The uncertainty in the control and test population structures is accounted for by using a double bootstrapping procedure that takes into account both between-haul and within-haul variation. This bootstrapping approach is used to assess the selectivity of two different devices, a 139.5 mm T90 codend and a 135.9 mm codend with 140.9 mm lateral exit windows, in the Barents Sea pelagic cod trawl fishery. The purpose of the experiment was to test and compare the performance of the two devices in pelagic trawl fisheries, where high densities of fish can be encountered. Significant differences were detected between the T90 codend and the codend with the exit windows but only for sizes of cod between 55 and 76 cm.
Downloads
References
Akaike H. 1974. A new look at the statistical model identification. IEEE Trans. Auto. Control 19: 716-722. http://dx.doi.org/10.1109/TAC.1974.1100705
Brcic J., Herrmann B., Sala A. 2015. Selective characteristics of a shark-excluding grid device in a Mediterranean trawl. Fish. Res. 172, 352-360. http://dx.doi.org/10.1016/j.fishres.2015.07.035
Council Regulation (Ec) No 517/2008, of 10 June 2008 laying down detailed rules for the implementation of Council Regulation (EC) No. 850/98 as regards the determination of the mesh size and assessing the thickness of twine of fishing nets. Official Journal of the European Union L 151.
Eigaard O., Herrmann B., Nielsen J.R. 2012. Influence of grid orientation and time of day on grid sorting in a small-meshed trawl fishery for Norway pout (Trisopterus esmarkii). Aquat. Living Resour. 25: 15-26. http://dx.doi.org/10.1051/alr/2011152
Fryer R.J. 1991. A model of between-haul variation in selectivity. ICES J. Mar. Sci. 48: 281-290. http://dx.doi.org/10.1093/icesjms/48.3.281
Grimaldo E., Larsen R.B., Holst R. 2007. Exit Windows as an alternative selective system for the Barents Sea Demersal Fishery for cod and haddock. Fish. Res. 85: 295-305. http://dx.doi.org/10.1016/j.fishres.2007.03.005
Grimaldo E., Sistiaga M., Larsen R.B. 2008. Evaluation of codends with sorting grids, exit windows and diamond meshes: Size selectivity and fish behaviour. Fish. Res. 91: 271-280. http://dx.doi.org/10.1016/j.fishres.2007.12.003
Herrmann B., Priour D., Krag L.A. 2006. Theoretical study of the effect of round straps on the selectivity in a diamond mesh cod-end. Fish. Res. 80: 148-157. http://dx.doi.org/10.1016/j.fishres.2006.04.018
Herrmann B., Sistiaga M., Nielsen K.N., et al. 2012. Understanding the size selectivity of red fish (Sebastes spp.) in North Atlantic trawl codends. J. Northw. Atl. Fish. Sci. 44: 1-13. http://dx.doi.org/10.2960/J.v44.m680
Herrmann B., Sistiaga M., Larsen R.B., et al. 2013a. Size selectivity of redfish (Sebastes spp.) in the Northeast Atlantic using grid-based selection systems for trawls. Aquat. Living Resour. 26: 109-120. http://dx.doi.org/10.1051/alr/2013051
Herrmann B., Wienbeck H., Moderhak V., et al. 2013b. The influence of twine thickness, twine number and netting orientation on codend selectivity. Fish. Res. 145: 22-36. http://dx.doi.org/10.1016/j.fishres.2013.03.002
Herrmann B., Larsen R.B., Sistiaga M., et al. 2015. Predicting Size Selection of Cod (Gadus morhua) in Square Mesh Codends for Demersal Seining: a Simulation-based Approach. Fish. Res.
Lövgren J., Herrmann B., Feekings J. 2016. Bell-shaped size selection in a bottom trawl: A case study for Nephrops directed fishery with reduced catches of cod. Fish. Res. http://dx.doi.org/10.1016/j.fishres.2016.03.019
Millar R.B. 1992. Estimating the size-selectivity of fishing gear by conditioning on the total catch. J. Amer. Stat. Assoc. 87: 962-968. http://dx.doi.org/10.1080/01621459.1992.10476250
Millar R.B. 1993. Incorporation of between-haul variation using bootstrapping and nonparametric estimation of selection curves. Fish. Bull. 91: 564-572.
Millar R.B., Fryer R.J. 1999. Estimating size-selection curves of trawls, traps, gillnets and hooks. Rev. Fish Biol. Fish. 9: 89-116. http://dx.doi.org/10.1023/A:1008838220001
Millar R.B., Broadhurst M.K., Macbeth W.G. 2004. Modelling between-haul variability in the size selectivity of trawls. Fish. Res. 67: 171-181. http://dx.doi.org/10.1016/j.fishres.2003.09.040
Norwegian Fisheries Directorate (J-7-2016). 2016. Regulations for fishing practices at sea J-7-2016, Norwegian Fisheries Directorate (www.fiskeridir.no), Bergen, Norway. 57 pp. (In Norwegian).
Notti E., Br?i? J., De Carlo F., et al. 2016. Assessment of the relative catch performance of a surrounding net without the purse line as an alternative to a traditional boat seine in small-scale fisheries. Mar. Coast. Fish. 8: 81-91. http://dx.doi.org/10.1080/19425120.2015.1095827
Özbilgin H., Erya?ar A.R., Gökçe G., et al. 2015. Size selectivity of hand and machine woven codends and short term commercial loss in the northeastern Mediterranean. Fish. Res. 164: 73-85 http://dx.doi.org/10.1016/j.fishres.2014.10.022
Richard S.A. 2008. Dealing with overdispersed count data in applied ecology. J. Appl. Ecol. 45: 218-227. http://dx.doi.org/10.1111/j.1365-2664.2007.01377.x
Sala A., Lucchetti A., Perdichizzi A., et al. 2015. Is square-mesh better selective than larger mesh? A perspective on fisheries management for Mediterranean trawl fisheries. Fish. Res. 161: 182-190. http://dx.doi.org/10.1016/j.fishres.2014.07.011
Sistiaga M., Herrmann B., Grimaldo E., et al. 2010. Assessment of dual selection in grid based selectivity systems. Fish. Res. 105: 187-199. http://dx.doi.org/10.1016/j.fishres.2010.05.006
Sistiaga M., Herrmann B., Grimaldo E., et al. 2015. Effect of lifting the sweeps on bottom trawling catch efficiency: A case study of the Northeast arctic cod (Gadus morhua) trawl fishery. Fish. Res. 167: 164-173. http://dx.doi.org/10.1016/j.fishres.2015.01.015
Sistiaga M., Herrmann B., Grimaldo E., et al. 2016. The effect of sweep bottom contact on the catch efficiency of haddock. Fish. Res. 179: 302-307. http://dx.doi.org/10.1016/j.fishres.2016.03.016
Wienbeck H., Herrmann B., Jordan P.F., et al. 2013. A comparative analysis of legislated and modified Baltic Sea trawl codends for simultaneously improving the size selection of cod (Gadus morhua) and plaice (Pleuronectes platessa). Fish. Res. 150: 28-37. http://dx.doi.org/10.1016/j.fishres.2013.10.007
Wileman D., Ferro R.S.T., Fonteyne R., et al. (eds). 1996. Manual of methods of measuring the selectivity of towed fishing gears. ICES Coop. Res. Rep. No. 215.
Published
How to Cite
Issue
Section
License
Copyright (c) 2016 Consejo Superior de Investigaciones Científicas (CSIC)
This work is licensed under a Creative Commons Attribution 4.0 International License.
© CSIC. Manuscripts published in both the printed and online versions of this Journal are the property of Consejo Superior de Investigaciones Científicas, and quoting this source is a requirement for any partial or full reproduction.All contents of this electronic edition, except where otherwise noted, are distributed under a “Creative Commons Attribution 4.0 International” (CC BY 4.0) License. You may read here the basic information and the legal text of the license. The indication of the CC BY 4.0 License must be expressly stated in this way when necessary.
Self-archiving in repositories, personal webpages or similar, of any version other than the published by the Editor, is not allowed.