I have always deeply disliked cold water, and by cold I mean anything below 22 degrees Celsius. This is why, even after 10 years in Australia, the underwater world of South Australia was still ranking low on my “to dive” list.

That was until I heard that the giant cuttlefish migration was in trouble. Every year, between May and August, the cold waters of the South Australian town of Whyalla in the Upper Spencer Gulf region used to attract an estimated population of over two hundred thousand Giant Australian Cuttlefish in a mass breeding aggregation.

The Giant Australian Cuttlefish (Sepia Apama) is the largest species of cuttlefish known in the world. It can reach up to 50cm in body length and up to 5kg. The rocky coastline of Whyalla provides a good spawning environment for the cuttlefish as the female can attach her eggs to the underside of the rocky ledges. Each female will mate with and collect sperm from multiple partners. The adults then die, while the next generation develop in their eggs. They hatch within three to five months, depending on the water temperature.

A fascinating mating ritual can be witnessed during the breeding season, as males compete for the outnumbered females. There are two distinct groups of males attending this annual congregation: Smaller males which reached maturity within 7 to 8 months of hatching, and much larger males which fail to mature quickly enough to mate during the previous breeding season and which are a year older than their smaller competitors. Bigger males have without doubt a physical advantage, but smaller males have mastered the art of trickery. They will change patterns and colour to look like a female and approach a mating pair under the unsuspecting eye of the bigger male. Given the chance, the “cross-dressing” male will quickly reverts to his usual male patterns and mate with the female.

This canvas of changing colour and fascinating behaviour explain why the cuttlefish mating season arguably ranks among the most amazing of marine wildlife spectacles. However, what made this breeding migration truly unique, (not just in Australia, but in the world) was the sheer number of attendees. I had heard that there had been so many cuttlefish in Whyalla in the past that it would look like an underwater carpet of changing colors as those “chameleons of the sea” would court and breed.

Unfortunately the numbers have declined steadily for a decade, to an estimated number of less than 20,000. A sense of urgency took over my aversion for cold water and I flew to Whyalla in June 2012.

The knowledgeable team at the local dive shop put me into the good hands of a local diver/photographer who kindly took me on his boat. This allowed me to get to more secluded areas and to access some areas that in the past had proven ideal for cuttlefish viewing. Everything was lining up for me: good weather, great logistics and an experienced dive buddy.

Unfortunately this wasn’t enough. Over the 3 days I spent in Whyalla, I only saw about 25 individuals. I knew their number had plummeted, but I wasn’t prepared for that. No doubt I missed a few as they have an amazing ability to mimic their surroundings by altering their colour, patterns, texture and shape. Still, those waters that once used to be home to one of nature's most spectacular breeding migration, felt terribly empty.

The exact reason for this drop in numbers is unknown. Locals mentioned a combination of factors, including overfishing in the late 1990s when the cephalopods were used as pet food and bait. There were concerns that the cuttlefish were being taken as they arrived at the breeding site, with no time to mate and spawn. Cuttlefish live fast and die young. They only ever breed once, and they have a short life cycle (generally no more than 18 months) since exhausted male and female adults die after mating and laying. Therefore overfishing of the breeding animals seriously impacts the overall population.

Thankfully, in 1998 the state government introduced a giant cuttlefish fishing closure to protect the spawning area and in March 2013, the South Australian State Government extended the protected area to cover all of Northern Spencer Gulf – the population’s entire known range. Funding was also allocated to research that will help to determine the movement patterns and population structure of the population in the area.

This is a positive conservation move, even though some might argue that, in view of the collapse in numbers and the fact that little spawning was witnessed last year, it might already be too late.

Furthermore, there are other possible risks as the Upper Spencer Gulf region receives proposals for major industrial developments including port development projects and desalination plants. Declining water quality in the area is already a concern and new pollution sources and local increases in the salinity could further harm or kill cuttlefish or their eggs.

This region is still mostly isolated from bigger cities, and industry brings jobs and money, therefore making it attractive to residents and the government. However it is essential that proper research and risks assessment are done to ensure the suitability of the proposed developments and identify their impact on the local wildlife.

I truly hope this will be the case and that the unique Australian giant cuttlefish migration will soon be back to its full glory.

For more information on the Giant Australian cuttlefish and to help protect it:

1) Read and share cuttlefishcountry.com

2) Sign the petition: thepetitionsite.com/7/save-the-giant-australian-cuttlefish-upper-spencer-gulf/

_Based in Sydney, Australia, Vanessa Mignon is a full-time business analyst who travels to remote locations and photograph amazing wildlife encounters, including mantas feeding feeding in the Maldives, whale sharks feeding in West Papua and humpback whales courting in the Kingdom of Tonga. To see more of her work, visit Vanessa Mignon Photography. _