Rethinking length-based fisheries regulations: The value of protecting old and large fish with harvest slots

  • Gwinn D
  • Allen M
  • Johnston F
 et al. 
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Managing fisheries using length-based harvest regulations is common, but such policies often create trade-offs among conservation (e.g. maintaining natural age- structure or spawning stock biomass) and fishery objectives (e.g. maximizing yield or harvest numbers). By focusing harvest on the larger (older) fish, minimum- length limits are thought to maximize biomass yield, but at the potential cost of severe age and size truncation at high fishing mortality. Harvest-slot-length limits (harvest slots) restrict harvest to intermediate lengths (ages), which may contribute to maintaining high harvest numbers and a more natural age-structure. However, an evaluation of minimum-length limits vs. harvest slots for jointly meeting fisher- ies and conservation objectives across a range of fish life-history strategies is cur- rently lacking. We present a general age- and size-structured population model calibrated to several recreationally important fish species. Harvest slots and mini- mum-length limits were both effective at compromising between yield, numbers harvested and catch of trophy fish while conserving reproductive biomass. How- ever, harvest slots consistently produced greater numbers of fish harvested and greater catches of trophy fish while conserving reproductive biomass and a more natural population age-structure. Additionally, harvest slots resulted in less waste in the presence of hooking mortality. Our results held across a range of exploitation rates, life-history strategies and fisheries objectives. Overall, we found harvest slots to represent a valuable option to meet both conservation and recreational fisheries objectives. Given the ubiquitous benefits of harvest slots across all life histories modelled, rethinking the widespread use of minimum-length limits is warranted

Author-supplied keywords

  • Conservation
  • Longevity overfishing
  • Minimum-size limit
  • Multiple objectives
  • Open slot
  • Recreational fishing
  • Trade-offs

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  • Daniel C. Gwinn

  • Micheal S. Allen

  • Fiona D. Johnston

  • Paul Brown

  • Robert Arlinghaus

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