Mitigating Slipping-Related Mortality from Purse Seine Fisheries for Small Pelagic Fish: Case Studies from European Atlantic Waters

  • Ana MarçaloEmail author
  • Mike BreenEmail author
  • Maria Tenningen
  • Iñigo Onandia
  • Luis Arregi
  • Jorge M. S. Gonçalves


The release of unwanted catches (UWC) from purse seines, while the catch is still in the water, is known as “slipping”. Once thought to be a benign process, compared to discarding UWC overboard from the fishing vessel, it is now recognised that “slipping” can lead to significant mortality in the released fish if done inappropriately. In this chapter, we examine purse seining and slipping operations, and discuss what drives slipping and potential mitigation measures to reduce slipping mortality. We use three examples of purse seine fisheries for small pelagic species in the North-east Atlantic; from Norway, Portugal and Spain. The ideal solution (identifying and avoiding UWC before the net is set) requires the development of tools to enable fishers to better characterise target schools in terms of key selection criteria, e.g., with respect to species, individual size and catch biomass. Such tools are being developed, based primarily on hydro-acoustic technology. However, some UWC in purse seine catches are inevitable, and operational improvements in slipping practices have been shown to significantly reduce stress and mortality in the released UWC. We conclude with a discussion on the challenges currently facing the implementation of the European Union (EU) Landing Obligation with regards to minimising slipping related mortality.


Bycatch and slipping mitigation Delayed mortality Pelagic fish Purse seine 


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Authors and Affiliations

  • Ana Marçalo
    • 1
    Email author
  • Mike Breen
    • 2
    Email author
  • Maria Tenningen
    • 2
  • Iñigo Onandia
    • 3
  • Luis Arregi
    • 3
  • Jorge M. S. Gonçalves
    • 1
  1. 1.Centro de Ciências do Mar-CCMARUniversidade do AlgarveFaroPortugal
  2. 2.Institute of Marine Research (IMR)BergenNorway
  3. 3.AZTI, Txatxarramendi ugartea z/gSukarrietaSpain

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