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Sea sense: log 3 Cuttlefish PDF Print E-mail

READING FROM THE CUTTLEBONEScuttlebone study

Walking the winter beach, I collected these two cuttlebones; one slim and the other more round, both about 70mm in length. Cuttlebones are buoyancy devices found inside cuttlefish. (Here’s a great diagram of their internal anatomy.) These are likely to be from two species of cuttlefish, marine animals, relatives of the squid (who don’t have cuttlebones) and the octopus. They’re members of a lively and intelligent clan in the larger group known as Molluscs, which include snails and bivalves such as mussels and clams.

IDENTIFICATION

On the reverse of the slim cuttlebone are three long ridges, which are a characteristic of the Rosecone Cuttlefish (Sepia rozella).
Could the round one be from the Reaper Cuttlefish (Sepia mestus)? Although they are both known to be found along the NSW coast, I can’t positively identify Rosecone or Reaper based on these sources.  Does anyone reading this know more? (Please post a comment or link below)

Among cuttlefish bones, there can be found differences not only between species but between males and females, the sizes of the adults and even clues about its death.

None of information about any species comes easily. If we’re lucky, what’s known locally is further developed with scientific skills. Wouldn't it be great to know every species at all five levels: the individual names and classification, its life cycle, population (details such as whereabouts and numbers), ecology (relationships with other species and processes in the world) and history. Which of the millions of species that exist do we know this well? Which ones do we include in our arts and culture?

LIFE CYCLE

But back to the cuttlefish. Whatever the size of the cuttlebone you find on a beach, it’s generally the remains of an animal that only lives for one or two years. The young hatch, looking like miniature adults and begin feeding and growing a body which is almost entirely pure muscle, all protein.

In contrast to the many marine animals who change sexes with age or size, cuttlefish have separate males and females, who stay that way for their entire lives. The population comes together in pairs to mate during the months of May through August. The females lay their small eggs on hard surfaces of reefs and then they die. The males die at the end of their breeding effort.

Most of the mating grounds are unknown, but at least two places in identified as important ones in Australia.  A species known as Giant Cuttlefish (Sepia apama) come inshore at a bay between Wyalla and Lowly Pt, in South Australia and at Wollongong, NSW.  (Here's the Australian Museum record for Sepia apama.) This cuttlefish can be up to a metre in size.

The Wyalla breeding grounds are of international significance. Winter dives, snorkeling trips and film expeditions are popular. (Here is a BBC clip on YouTube) On average, there is a mating pair for every square metre. Heavy fishing nearly broke up this population but since 1998, a moratorium on harvesting the cuttlefish guards the breeding grounds.

Oddly enough the new marine park proposal doesn’t include this area. The cuttlefish are threatened by a new BHP desalination plant for the Olympic Mine. There are supporters worldwide calling on State and Federal government to ensure this area is protected.

(You can send a letter of support through the Australian Marine Conservation Society SA marine campaign. You can also spread the word about the new Alliance on behalf of SA marine conservation)

POPULATION & ECOLOGY

Recent studies of these giant Sepia apama find there are five populations from Ningaloo to Moreton Bay.  They may have the whole ocean to roam, but they don’t. Two populations are along NSW, which has me wondering if the ones that breed and die around Wollongong are all one population. This could mean that there is another population in northern NSW. Where would they be mating? Has anyone noticed anything?

Perhaps the answer lies in watching seabirds. The Wollongong area is also known for all the albatross that come at this time to feed on the recently dead cuttlefish. What signs are there of giant Sepia apama or any other species aggregating and breeding anywhere around Northern NSW? Some say cuttlefish in general can be generally found on reefs near headlands. How true is that for the which species?

After these dramatic lovemaking sessions, the fate of every cuttlefish population rests entirely with the little eggs. If the eggs do not hatch in bulk, with large healthy babies, the next season’s population is down in numbers. This will then cut into the success of the next season’s mating and egg laying. Already we know that the eggs are very sensitive to changes in the water quality.

THEIR RECENT HISTORY & OUR FUTURE

The deep history of cuttlefish goes back millions of years. More recently,  human impact is a major consideration. Around the world, some squid populations have collapsed.  The NSW wild fisheries research programme says that the status of our populations is uncertain. The Australian Sustainable Seafood Guide says cuttlefish, squid and octopus populations are robust but more information is needed. Pollution is also an issue. Who do you know is out there counting eggs and hatchlings?

But most of this cuttlefish story I am telling is only about the species Sepia apama. That’s not the one creating the cuttlebones I found. We’re still building even basic knowledge about these two and the other ten species in total found right here on this coast.

What to add something important into your life? You could keep an eye out for different cuttlebones on your beach. You could help the Southern Ocean Seabird Study Association Inc: a NSW Seabird Group who also study cuttlefish.

Or perhaps you want to tell a story to inspire the kids or the grand kids? Our unsung heroes are the people figuring out the taxonomy of cuttlefish and other species. Among the explorers of the 21st century are those mapping cuttlefish populations and figuring out their secret lives.

And the greatest political leaders? They will be those who understand and act on these ecologics.








 
Comments (6)
reply
6Friday, 03 June 2011 00:41
M Gardner

Excellent! I will follow that up. Thanks so much for that.

Giant cuttlefish at Wollongong
5Thursday, 02 June 2011 09:30
Joy Window

I don't know definitely about an aggregation, but assume there is one - see http://www.abc.net.au/science/articles/2001/07/05/2691952.htm and http://www.seitre.com/www/03_features/albatros_fishermen/pages/albatros_fishermen-03.html



Local dive shops down there (of which there are several) would most likely know. Or perhaps contact Mark Norman of the cuttefish book fame (http://wn.com/Mark_Norman_%28marine_biologist%29) - he’s keen on ‘citizen science’ and would be my first port of call for this.

reply
4Wednesday, 01 June 2011 07:01
M Gardner

Thanks for that. Great little book. Lucky you to see the S apama. Have you any news about any aggregation site in the Wollongong area? Perhaps a local dive centre knows about it?


The S Australia aggregation site seems to be in great trouble. Pass it on. Maybe we can get more letters written and attention focused on this issue.


 

Cuttlefish ID
3Wednesday, 01 June 2011 01:27
Joy Window

 


According to the photographic cuttle bone ID guide at the end of Norman and Reid’s “A Guide to Squid, Cuttlefish and Octopuses of Australasia”, I’d venture that the roundish bone is indeed Sepia mestus. None of the others are so round. Under the photo, it says “14 cm. Eastern Australia and possible elsewhere in the Indo West Pacific”.


I’ve been fortunate to see two giant cuttlefish (Sepia apama) on a July (winter) day, washed up at Waniora Point, Bulli, near Wollongong. One was mostly eaten and still being eaten by silver gulls. The other was mostly intact. Referring to my field notes, I see that it was about 104 cm long (including the tentacles), 60 cm wide across the body, and quite thick. It smelled of fresh calamari (no surprise there). The colour was basically white with brownish purple ‘stripes’, with a trace of iridescence visible around the head. I still have the beak I cut out of the mostly eaten one - it’s about 7 cm long. It was a real thrill to see these animals.

cuttlefish and BHP
2Sunday, 29 May 2011 00:20
M Gardner

There is an urgency to this story of cuttlefish as BHP wants to build a desalination plant on Point Lowly where the giant cuttlefish breed. The dynamics of the waters are such that at times, the changing of the tide does not happen. This means adding discharge waters to this environment is a great hazard. Check out the latest specialist advice here at the website of the Australia Science Media Centre.


 


 


 

CUTTLEFISH BONES
1Thursday, 26 May 2011 20:34
John Warburton

Great to be able to read more into what we see on the beach every day and take so much for granted

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