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Quantifying causes of discard variability: an indispensable assistance to discard estimation and a paramount need for policy measures
Depestele, J.; Vandemaele, S.; Vanhee, W.; Polet, H.; Torreele, E.; Leirs, H.; Vincx, M. (2011). Quantifying causes of discard variability: an indispensable assistance to discard estimation and a paramount need for policy measures. ICES J. Mar. Sci./J. Cons. int. Explor. Mer 68(8): 1719-1725. dx.doi.org/10.1093/icesjms/fsr030
In: ICES Journal of Marine Science. Academic Press: London. ISSN 1054-3139; e-ISSN 1095-9289
Peer reviewed article  
Available in  Authors 
    Vlaams Instituut voor de Zee: Open access 220961 [ download pdf ]
Keywords
    Beam trawlers
    Legislation > Fishery regulations > Quota regulations
    Management > Resource management > Fishery management
    Market prices
    ANE, North Sea [Marine Regions]
    Marine/Coastal
Author keywords
    beam trawl; discards; fishery management; highgrading; market price; minimum landing size; North Sea; quota
Authors  Top 
  • Depestele, J.
  • Vandemaele, S.
  • Vanhee, W.
  • Polet, H.
  • Torreele, E.
  • Leirs, H.
  • Vincx, M.
Abstract
    Fishery-dependent data underpin the scientific advice given to fishery managers. However, discard estimates are often imprecise as a result of limited sampling coverage. Estimating discard rates from length frequency distributions (LFDs) in commercial catches may complement information from observer trips. The accuracy of estimates depends greatly on careful investigation of the discard variability. Here, the impact of three essential factors was quantified for beam-trawl fisheries in the southern North Sea: (i) market prices, (ii) landings per trip (LPT) limitations, and (iii) selectivity of the commercial fishing gear. Observed discard rates for cod, plaice, sole, and whiting were compared with estimates based on length frequency data, taking account of the variability attributable to LPT limitations and market price. Observed discard estimates of cod and whiting differed significantly from LFD-derived estimates because of highgrading. The results indicate that LFD-derived discard estimates are only reliable if the crucial driving factors are quantified. LFDs can be collected from research vessels or by fishers in partnership with scientists. Based upon many of these LFDs and the discard-variability factors identified in observer programmes, discard rates can be estimated better.
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