Identifying features: The Giant Cuttlefish are hard to mistake with a thick solid mantle and a short stout head and tentacles. Like calamari, these Cuttlefish have control of their chromataphores (colour bearing pigment cells) and can subsequently change colour in less than a second. Most often these cuttlefish will be seen as a maroon colour however, during breeding season the males with adopt changing bright colours and striking patterns to dazzles the female cuttlefish.Size and lifecycle: The Giant Australian cuttlefish is the largest cuttlefish in the world!!!! The largest recorded cuttlefish had a mantle length of 520mm, a total length of over 1 metre and weighed over 10kg!

The Giant cuttlefish live between a depth of 1.5m- 100m and spend most of their time resting, camouflaged against the sea floor or hiding under a rock ledge. Research suggests that they spending as little as 3.7% of their time foraging, suggesting that they are incredible hunters using a combination of stealth and camouflage to capture their prey.
These cuttlefish have a relatively short lifecycle of between 1-2 years where they live a relatively solitary existence coming together only for breeding. This breeding can be quite spectacular with a density of 1 cuttlefish per cubic metre during the mass aggregations.
After spawning these cuttlefish lay eggs and then die which is why we see quite often see cuttles on the beaches around southern Australia.

Diet: The main diet of cuttlefish consists of small fish and crustaceans (such as prawns and small crabs). When they feed, the cuttlefish shoot out two tentacles, which are usually tucked away in pouches under their eyes. This is done in a rapid whip-like action to seize their prey, then holding their prey within their arms while they consume it. If they are feeding on a hard-shelled animal, they use their strong beaks to crack open the shell and their tooth lined tongue for rasping away at the food.
These cuttlefish are in-turn eaten by Indo-Pacific bottlenose dolphins who have developed a technique of removing the ink and cuttle before eating the cuttlefish.
Distribution: The Australian Giant Cuttlefish is endemic to Australian waters and its distribution extends from Southern Queensland to Port Cloates in Western Australia including northern Tasmania.

Fishing Qualities: Cuttlefish do make quite good bait. In South Australia a small commercial fishery exists which harvest them to be used as Snapper bait. If caught in the harbour they can be used as kingfish bait in particular the belly and also the tentacles. However, I do not suggest this as they are very cool creatures and squid make a much better bait.
Fishing techniques: These cuttlefish are often caught whilst squidding using the typical squid jig in a variety of colours. Whilst they do inhabit Sydney Harbour I would not suggest targeting them specifically as they can be few and far between.