CUTTLEFISH CHAOS AT WHYALLA
Giant cuttlefish are
only found in the waters of southern
Whyalla is a small desert town in
Arriving in Whyalla in mid May we had timed our visit for the start of the breeding season, which runs from May to August. Our first stop was Whyalla Diving Adventures to pickup dive gear and chat to owner Shane Grant. Shane informed us that the cuttlefish had arrived and dozens were already being seen. One of the best things about this cuttlefish gathering is that they are accessible from shore, and even snorkellers can view the breeding cuttlefish.
As soon as we entered the water we could see giant cuttlefish in only 2m of water. The visibility was around 8m and for the next hour we were to see over a hundred cuttlefish in depths from 2m to 6m. The cuttlefish gather in this small area because of the rocky bottom, which gives the females somewhere safe to deposit their eggs.
We were keen to see some cuttlefish behaviour and it didn’t take long. Almost immediately we found two large males sizing each other up, arranged side by side, they were flattening their bodies and pulsating dark bands across their bodies as they determined who was the strongest. This continued for a few minutes before one of them buckled and swam off. He was obviously the challenger, as we then noticed that the other male was guarding a smaller female hidden below him in a crevasse. Not all these displays ended so calmly, as we saw other males grab each other, with quite a few displaying bit marks. Being the beginning of the breeding season many of the cuttlefish were establishing their territory, so we were to see many standoffs between large males.
As we swam around the seaweed and algae we were amazed by the number of giant cuttlefish, they were everywhere we looked, it has been estimated there is one every square metre over an area of several kilometres. We found quite a few females already laying eggs, squeezing under ledges to deposit their eggs, which take several months to hatch.
We were then lucky enough to find a pair getting amorous, with the larger male suddenly turned towards the female, shooting out his tentacles and engulf her head. What we couldn’t see was him passing a package of sperm with a modified tentacle into her body cavity so she could fertiliser her eggs. These two were locked together for several minutes, allowing us to shoot plenty of photos of this rarely seen intermit act.
We enjoyed two days of diving with the giant cuttlefish, which allowed us plenty of time to see one of the most unique behaviours of this species, cross dressing males! The biggest cuttlefish generally get the girl, but if you watch carefully you will notice smaller males are constantly trying to sneak up on the big guys. But researchers have found that some of these smaller males will pretend to be females, changing their colouration and behaviour to sneak pass the big males and get close to his girl, before changing back to normal male colouration and mating with the female, right under the nose of the big male!
We observed this behaviour on many occasions, but most of the time the larger male realised it was an impostor and chased him off. But on the second day we saw two of these cross dressing males sneak in under the guard of a larger male and mate with his female. Both times the smaller male got to mate for several minutes before the larger male woke up to what was happening and chased them off. Research has recently shown that these cross dressing males have a higher mating success rate than the large males, cunning outwitting muscle!
We had a fantastic couple of days diving with the giant cuttlefish, seeing more cephalopod behaviour in two days than you would normally see in a lifetime. We were glad we had come at the beginning of the season as it would have been heart breaking to see dead and dying cuttlefish later in the season, as these cuttlefish live fast and die young, with most of them dying after breeding, having only lived for one or two years.
The area where the cuttlefish aggregate is fully protected during the breeding season, thanks to the efforts of local diver Tony Bramley. He lobbied to get the area protected after fishing pressures almost saw this unique gathering wiped out in the 1990s. With divers coming from across
Right in the middle of the cuttlefish breeding site is the Santos Port Bonython hydrocarbon processing plant, including a 2.4km long jetty for loading ships. This facility has been there since 1984 and the cuttlefish have survived,
But that is not all, as several mining companies also want to build facilities and another jetty at Point Lowly for the loading of iron ore and possibly copper concentrate and uranium, plus a petrochemical and diesel refinery. One spill from any of these materials would also spell the end of the cuttlefish.
Local action group the Cuttlefish Coast Coalition are fighting these proposed developments. We can only hope that the Federal or State Government blocks these developments and protects the most unique gathering of cuttlefish in the world for future generations to enjoy.
Article appeared in Dive Pacific No.116 Feb/Mar 2010