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Project H.8.c - Cow-calf separation study

01 May 2022 - 31 May 2023

Program(s) in charge: Stock Assessment Program
Evaluate whether permanent separation of dolphin mothers and their calves occurs during purse-seine fishing operations on dolphin-associated tuna.
  • With the drastic decrease in dolphin mortality due to entanglement in tuna purse-seine nets during the 1990s, more attention was paid to other possible sources of mortality.
  • Some studies have shown that in the 1980s and 1990s there were cases of orphaned nursing calves due to maternal mortality.
  • Based on analysis of biological samples collected by fisheries observers, it has also been suggested that mothers and calves may be separated during chases leading to purse-seine sets.
  • However, it remains an open question whether current fishing operations lead to permanent separation of cows and calves.
  • The objective of this study is to resolve this question by determining, through direct observation, whether dolphin mothers and calves are indeed separated during chase and/or backdown.
Relevance for management
Improve the management of dolphin stocks in the ETP.
12 months
Workplan and status
  • May 2022: obtain commitment from one or more purse-seiners to participate in the study.
  • June – August 2022: hold workshop on development of a detailed field protocol; consultation with drone team on project details; hire graduate students and an observer to assist with project.
  • September – November 2022: preparation for study.
  • December 2022 – January 2023: Conduct field study.
  • January – May 2023: data analysis; report preparation.
External collaborators
  • Michael Scott;
  • Workshop participants: Drs. Karin Forney and Eric Archer (NMFS); Drs. Lisa Balance and John Durban (Oregon State University).
  • Drone company; several graduate students, one or more purse-seine vessels.
  • Pacific Alliance for Sustainable Tuna
  • Presentation of results at SAC-14 (May 2023).