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Resource Ecology & Ecosystem Modeling (REEM) Program

Seabird Interactions

In the 2003 Biological Opinion on the total allowable catch setting process for short-tailed albatross, Phoebastria albatrus, NMFS was required to “…work on a safe and reliable means of assessing short-tailed albatross interactions/collisions with trawl vessel gear to 1) document whether take occurs, and if so, 2) estimate the rate of such take…” To date, no observers have reported collisions between short-tailed albatross and trawl gear. Observers do not, however, directly monitor trawl gear during the towing process.

We initiated several collaborative studies to look at the possibility of these interactions through fishery characterization, risk assessments, and decision analysis. One such study was recently completed by Stephanie Zador, Andre Punt, and Julia Parrish of the University of Washington. They conducted a decision analysis that explores the effects of trawl-related fisheries mortality on achieving the population recovery goals for the short-tailed albatross. In their study, “Bayesian inference was used to assign probabilities to alternative plausible rates of fishing mortality and to conduct population projections with different levels of trawl mortality to determine their effects on achieving the population recovery goals.

The analyses of the impact of trawl mortality on the Torishima short-tailed albatross population suggests that exceeding the current expected incidental take in the Alaska groundfish trawl fishery, two in any five year period, by as much as a factor of 10 would have little impact on when the proposed recovery goals for the species are achieved.” An example of their findings is noted in Table 1 (below) excerpted from their paper.

By Shannon Fitzgerald
 

Table 1.  The year in which the recovery goal of 750 pairs (1,500 breeding birds) is reached with 0.75 probability given assumptions regarding fishing mortality from all sources of mortality, S’, and the fraction of the mortality due to trawling in Alaska, z. Population projections (n = 1,000) were conducted for each.
  S’ = 0.93   S’ = 0.95   S’ = 0.97   S’ = 0.99
  z = 0.01 z = 0.05 z = 0.01 z = 0.05 z = 0.01 z = 0.05 z = 0.01 z = 0.05
 0 albatross taken;
 closure of trawl fishery
2022 2022 2019 2019 2017 2017 2016 2016
 1 albatross taken 2022 2022 2019 2019 2017 2017 2016 2016
 5 albatross taken 2023 2022 2019 2019 2018 2017 2016 2016
 10 albatross taken 2023 2023 2020 2019 2018 2018 2016 2016
 20 albatross taken 2025 2024 2021 2020 2018 2018 2017 2017
 50 albatross taken 2032 2030 2024 2024 2021 2020 2019 2019

 

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