Australia’s Giant Cuttlefish Mating Event Plummets to Lowest Count in Decades

Sun Sep 06 2026 01:22:15 GMT+0000 (Coordinated Universal Time)

A record drop in cuttlefish mating numbers sparks fears of catastrophic decline amid a toxic algal bloom along South Australia's coast.

Every winter the South Australian coast hosts the world’s biggest cuttlefish mating event, drawing hundreds of thousands of the remarkable creatures. This year, however, only 1,811 cuttlefish were recorded—a 97% fall from the previous 63,000. Officials blame a 18‑month toxic algal bloom. Dive teams found just 440 eggs versus the usual millions, leading experts to call for the species be listed as endangered. Despite natural population swings, the unprecedented low figures raise serious alarms about the species’ future.

Every winter along the South Australian coast, the world’s largest cuttlefish mating event attracts hundreds of thousands of these magnificent cephalopods and daring divers. This year, however, the turnout was the lowest on record, with only 1,811 cuttlefish—down from 63,000 last year, a 97% drop.

The state government points to a toxic algal bloom that has plagued the coastline for over 18 months as a likely culprit.

The decline has spurred calls to list the species as endangered, as adult cuttlefish typically die after breeding, making each season critical for replenishing the population.

Dive teams led by diver Manny Katz conducted weekly surveys, finding only 440 eggs—a far cry from the millions usually laid.

“Under our current circumstances, with so few eggs along the coastline, we don’t know if the population is ever going to recover,” said Katz.

Experts note that the harmful algal bloom is likely a major factor but definitive cause remains to be proved.

Despite data showing natural fluctuations in numbers, the unprecedented low count raises serious alarms for future generations of cuttlefish.

Marine ecosystems in ’real big trouble’

The algal bloom, driven by warming waters and nutrient pollution, has been wiping marine habitats for the past year‑and‑a‑half, Katz says, making cuttlefish and other cephalopods especially vulnerable.

Last year’s mating season was unaffected by the bloom, but recent months have seen toxic algae detected along the coast.

“This is an indicator that our marine ecosystems are in real big trouble—our canary in the coal mine,” Katz added.

Co‑founder of the Great Southern Reef Foundation, Stefan Andrews, is pushing for the cuttlefish to be listed as threatened, citing inadequate breeding evidence as proof of a catastrophic decline.

The Department of Primary Industries and Regions notes that cuttlefish populations naturally fluctuate, citing record lows and highs from past surveys.

Professor Mike Steer remains cautiously optimistic, noting that while the 2026 numbers are disheartening, past resilience suggests the species may rebound once conditions improve.