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Quantifying causes of discard variability: an indispensable assistance to discard estimation and a paramount need for policy measures

(2011) ICES JOURNAL OF MARINE SCIENCE. 68(8). p.1719-1725
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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.
Keywords
highgrading, fishery management, discards, beam trawl, market price, minimum landing size, North Sea, quota, NORTH-SEA PLAICE, PLEURONECTES-PLATESSA L., TRAWL FISHERY, SEXUAL-MATURATION, COMMERCIAL CATCH, OBSERVER SURVEYS, SELECTIVITY, MANAGEMENT, RATES, FLEET

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Chicago
Depestele, Jochen, Sofie Vandemaele, Willy Vanhee, Hans Polet, Els Torreele, Herwig Leirs, and Magda Vincx. 2011. “Quantifying Causes of Discard Variability: An Indispensable Assistance to Discard Estimation and a Paramount Need for Policy Measures.” Ices Journal of Marine Science 68 (8): 1719–1725.
APA
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 JOURNAL OF MARINE SCIENCE, 68(8), 1719–1725.
Vancouver
1.
Depestele J, Vandemaele S, Vanhee W, Polet H, Torreele E, Leirs H, et al. Quantifying causes of discard variability: an indispensable assistance to discard estimation and a paramount need for policy measures. ICES JOURNAL OF MARINE SCIENCE. 2011;68(8):1719–25.
MLA
Depestele, Jochen, Sofie Vandemaele, Willy Vanhee, et al. “Quantifying Causes of Discard Variability: An Indispensable Assistance to Discard Estimation and a Paramount Need for Policy Measures.” ICES JOURNAL OF MARINE SCIENCE 68.8 (2011): 1719–1725. Print.
@article{2997783,
  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.},
  author       = {Depestele, Jochen and Vandemaele, Sofie and Vanhee, Willy and Polet, Hans and Torreele, Els and Leirs, Herwig and Vincx, Magda},
  issn         = {1054-3139},
  journal      = {ICES JOURNAL OF MARINE SCIENCE},
  keywords     = {highgrading,fishery management,discards,beam trawl,market price,minimum landing size,North Sea,quota,NORTH-SEA PLAICE,PLEURONECTES-PLATESSA L.,TRAWL FISHERY,SEXUAL-MATURATION,COMMERCIAL CATCH,OBSERVER SURVEYS,SELECTIVITY,MANAGEMENT,RATES,FLEET},
  language     = {eng},
  number       = {8},
  pages        = {1719--1725},
  title        = {Quantifying causes of discard variability: an indispensable assistance to discard estimation and a paramount need for policy measures},
  url          = {http://dx.doi.org/10.1093/icesjms/fsr030},
  volume       = {68},
  year         = {2011},
}

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