Download FAR 2026/16 Annual survey of the Foveaux Strait oyster (Ostrea chilensis) fishery (OYU 5) and Bonamia exitiosa prevalence, intensity, and disease mortality in February 2025

• The Foveaux Strait oyster fishery (OYU 5) is a high value, nationally important fishery.
• A defining feature of the OYU 5 fishery is the recurrent infection by the parasite Bonamia exitiosa (Bonamia)
• Annual research surveys monitor both oyster abundance within the fishery and the prevalence of Bonamia infection annually.
• A dredge survey was undertaken in February 2025, in collaboration with the Bluff Oyster Management Company Ltd on FV Golden Harvest.
• Oyster densities have declined since 2021.
• In 2025, 1752 oysters were tested from 71 stations, with 20.7% testing positive for Bonamia.
• Disease mortality caused by B. exitiosa is between 12.1 and 12.3%, an increase from 2024 (between 10.2 and 10.6%), and its highest since 2015.
• The increased disease mortality is expected to affect the number of recruited oysters in the population.