Hind-casting the quantity and composition of discards by mixed demersal fisheries in the North Sea

Research output: Contribution to journalArticle

8 Citations (Scopus)
218 Downloads (Pure)


Many commercial fisheries seek to maximise the economic value of the catch that they bring ashore and market for human consumption by discarding undersize or low value fish. Information on the quantity, size and species composition of discarded fish is vital for stock assessments and for devising legislation to minimise the practice. However, except for a few major species, data are usually extremely sparse and reliant on observers aboard a small sample of fishing vessels. Expanding these data to estimate total regional discards is highly problematic. Here, we develop a method for utilising additional information from scientific trawl surveys to model the quantities of fish discarded by the commercial fisheries. As a case-study, we apply the model to the North Sea over the period 1978-2011, and show a long-term decline in the overall quantity of fish discarded, but an increase in the proportion of catch which is thrown away. The composition of discarded catch has shifted from predominantly (~80%) undersized roundfish, to >50% flatfish. Undersized plaice constitute the largest single fraction of discards, unchanged from the beginning of the 20th century. Overall, around 60% of discarded fish are rejected on the basis of size rather than for reasons of species value or quota restrictions. The analysis shows that much more information can be gained on discarding by utilising additional sources of data rather than relying solely on information gathered by observers. In addition, it is clear that the reducing fishing intensity and rebuilding stocks is likely to be more effective at reducing discards in the long term, than any technical legislation to outlaw the practice in the short term.
Original languageEnglish
Article numbere0117078
Pages (from-to)1-35
Number of pages35
JournalPLoS One
Issue number3
Publication statusPublished - 16 Mar 2015


  • fisheries management
  • discards
  • North Sea
  • bayesian
  • trawl survey data



StrathE2E marine foodweb model

Heath, M. (Creator), University of Strathclyde, 23 Mar 2016


Research Output

  • 8 Citations
  • 3 Article
  • 1 Commissioned report
Open Access
  • 8 Downloads (Pure)
    Open Access
    6 Citations (Scopus)
    23 Downloads (Pure)

    Cascading ecological effects of eliminating fishery discards

    Heath, M. R., Cook, R. M., Cameron, A. I., Morris, D. J. & Speirs, D. C., 13 May 2014, In : Nature Communications. 5, 8 p., 3893.

    Research output: Contribution to journalArticle

    Open Access
  • 54 Citations (Scopus)
    115 Downloads (Pure)


    • 1 Participation in conference
    • 1 Types of Public engagement and outreach - Media article or participation
    • 1 Invited talk

    Public Hearing of the European Parliament Fisheries Committee

    Mike Heath (Speaker)

    13 Apr 2015

    Activity: Talk or presentation typesInvited talk

    Recorded radio interview on fisheries discarding in the North Sea

    Mike Heath (Interviewee)

    19 Mar 2015

    Activity: Other activity typesTypes of Public engagement and outreach - Media article or participation

    MASTS Annual Science Meeting 2014

    Mike Heath (Participant)

    4 Sep 2014

    Activity: Participating in or organising an event typesParticipation in conference

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