Environment & Climate
Giant cuttlefish numbers drop 97% during South Australia mating season
Official surveys recorded a record low turnout for the annual breeding event, with experts pointing to an ongoing toxic algal bloom.
The short version
- An estimated 1,811 giant cuttlefish attended the annual mating event in South Australia this year, a 97% decline from 63,000 last year.
- Divers counted around 440 eggs along eight kilometers of coastline, far below the millions typically deposited.
- Officials and scientists suspect an ongoing toxic algal bloom is responsible, though population fluctuations have occurred in past years.
- Conservation advocates are pushing to list the species as threatened, while researchers assess whether the population can recover next season.
Key facts
- Official estimates indicate only 1,811 giant cuttlefish arrived along South Australia's Cuttlefish Coast to breed this year, down from 63,000 in 2025.[BBC News]
- A Department of Environment and Water survey found approximately 440 eggs along an eight-kilometer stretch of coastline, compared to millions normally recorded.[BBC News]
- A toxic algal bloom affecting the South Australian coastline for over 18 months has been cited by state authorities and researchers as a primary potential driver of the drop.[BBC News]
- The Great Southern Reef Foundation co-founder Stefan Andrews is seeking to list the giant Australian cuttlefish as a threatened species.[BBC News]
- Historical records show giant cuttlefish numbers naturally fluctuate, previously dropping to 13,500 in 2013 before rising to 247,000 in 2020.[BBC News]
What remains uncertain
- It is not definitively proven whether the toxic algal bloom caused the entire population collapse or if other natural environmental variables contributed.[BBC News]
- Because giant cuttlefish live only 12 to 18 months, scientists do not yet know if the severely low egg count will prevent the species from recovering in upcoming breeding cycles.[BBC News]