Short-Term Pain And Long-Term Gain: Using Phased-In Minimum Size Limits To Rebuild Stocks—The Pacific Bluefin Tuna Example

Details

• Journal Title:
  Transactions of the American Fisheries Society
• Personal Author:
  Ailloud, Lisa E. ; Gedamke, Todd ; Hoenig, John M.
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research) ; Sea Grant ; CIMAS (Cooperative Institute for Marine and Atmospheric Studies)
• Sea Grant Program:
  VSGCP (Virginia Sea Grant)
• Description:
  Like many stocks, the Pacific Bluefin Tuna Thunnus orientalis has been considerably depleted. High exploitation rates on very young fish have reduced the spawning stock biomass (SSB) to 2.6% of the unexploited level. We provide a framework for exploring potential benefits of minimum size regulations as a mechanism for rebuilding stocks, and we illustrate the approach using simulations patterned after Pacific Bluefin Tuna dynamics. We attempt to mitigate short-term losses in yield by considering a phased-in management strategy. With this approach, the minimum size limit (MSL) is gradually increased as biomass rebuilds, giving fishing communities time to adjust to new restrictions. We estimated short- and long-term effects of different MSLs on yield and biomass by using data from the 2016 assessment. A variety of scenarios was considered for growth compensation, discard mortality, and interest rates. The long-term value of the fishery was maximized by setting an MSL of 92 cm FL, which resulted in a 70% loss in yield during the first year (short-term pain). By implementing the MSL in two phases (64 cm FL in year 1; 92 cm FL in subsequent years), the long-term value of the fishery was maintained, and the short-term pain was reduced to a maximum 46% loss in yield during any 1 year. Under a three-phase implementation (55 cm FL in year 1; 77 cm FL in year 2; and 92 cm FL in subsequent years), the short-term pain was further reduced to a maximum loss of 30% during any 1 year. With no discard mortality, long-term yield increased by 165% and SSB increased 13-fold (to 33% of virgin SSB), regardless of the number of phases used. Long-term benefits were quickly diminished with increasing discard mortality. This simulation approach is widely applicable to cases where minimum size changes are contemplated; for Pacific Bluefin Tuna, our simulations demonstrate that size limits should be considered.
• Keywords:
  Bluefin Tuna Fishery Management Bluefin Tuna Fishery Management
• Source:
  Transactions of the American Fisheries Society 147(6): 1015-1029
• DOI:
  https://doi.org/10.1002/tafs.10098
• Sea Grant Document Number:
  VSGCP-R-18-020
• Document Type:
  Journal Article
• Rights Information:
  CC BY
• Compliance:
  Library
• Main Document Checksum:
  urn:sha256:615d0f0dd25af139bf78bb20a7f294464b37848c6a6808538dbe23ea815c1473
• Download URL:
  https://repository.library.noaa.gov/view/noaa/43891/noaa_43891_DS1.pdf
• File Type:
  [PDF - 843.74 KB ]