Prior to mid-1990s, the aggregation was fished at sustainable levels for snapper bait. However, in the mid 90’s, fishers actively targeted cuttlefish, and large numbers of the breeding aggregation were removed from the system. The life cycle of many cephalopods (squid, cuttlefish and octopus) is very short, and their lives end after laying eggs. This means if you fish out one cohort of breeders, the following generation is going to be severely impacted. To avoid long-term population decline, even local extinction, a renewable moratorium preventing fishing was introduced. In subsequent years, the cuttlefish numbers increased again, and ecotourism in the area began to thrive. Since 2010 the population however has begun to dramatically decline with the lowest numbers recorded in 2013. The numbers have increased again over the last few years.

 

Why are the cuttlefish so popular?

The sheer number of animals makes the breeding aggregation unique, not just in Australia, but the world. Together with the ability to watch their amazing mating displays and quirky behaviours, the Whyalla cuttlefish have become a global phenomenon, with scientists, naturalists, recreational divers and snorkelers wanting to document their activities.

 

Cuttlefish mating occurs in pairs. With such an enormous population, you can imagine the competition between males to mate with a female is quite intense. This is where the behaviour becomes quite interesting: large males are bigger and easily outcompete other males for female attention. Smaller males, not wanting to miss out on the opportunity to mate, change colours and body patterns to look like a female (hence 'cross-dressing' cuttlefish!). The large male that has paired up with a female allows this extra 'female' to get quite close. When he is distracted, the cross-dressing male quickly reverts back to normal male patterns and colours, mates with the female, and quickly swims away from the unsuspecting large male before a potentially fatal fight.

 

In summary, even on snorkel, you can see a range of cuttlefish antics: instant and dramatic colour changes, cross dressing and 'sneaky sex', guarding and fighting, mating and egg laying.

 

Research we have been involved in

 

We have undertaken a range of research projects on giant Australian cuttlefish.

 

The Gillanders lab have been researching giant Australian cuttlefish since the early 2000s. Our initial research was on population structure (funded via the Australian Research Council). Several Honours (Jackie Dupavillon, Leanne Trott) and PhD (Nicholas Payne, Sarah Catalano) students have studied cuttlefish - Jackie investigated the effects of desalination brine on embryo development and Leanne investigated the effects of temperature and seawater trace element concentration on statolith chemistry of embryos and juveniles. Nick studied population dynamics and behaviour of giant Australian cuttlefish on the breeding aggregation at Point Lowly. Sarah investigated the dycemid parasite fauna of cephalopods including the giant Australian cuttlefish - dycemids are a poorly known group of organisms found within the renal appendages of benthic cephalopods.

 

We have been using population genomics to determine the systematic status of the giant Australian cuttlefish. Our earlier research suggested that two populations of cuttlefish occur in South Australian waters with the boundary between the two species occurring in the upper Spencer Gulf. Besides examining genetic evidence we also investigated eco-phenotypic variation in traits (feeding ecology) and physiological tolerances to the salinity/temperature gradients. We analysed statoliths and cuttlebones to determine movement of cuttlefish throughout their life history and potentially natal origins. We developed a population model that can be used to examine different management interventions. This work was part of an FRDC report (see below) and we are currently writing up aspects of it for publication.

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Our current research is focused around global trends in cephalopods. Because of the short time series of abundance data available for giant Australian cuttlefish we were unable to ascertain long-term trends in abundance and whether cyclical patterns were observed. We collated time series of data from around the world to investigate trends. Rather than finding cyclical patterns we found evidence for an increase in cephalopod abundance over the last 60 years. This research is published in Current Biology.

 

Outputs

 

Our publications and reports include:

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Gillanders BM. 2018. Why we're watching the giant Australian cuttlefish. The Conversation, August 15 2018.

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Doubleday ZA, TAA Prowse, A Arkhipkin, GJ Pierce, J Semmens, M Steer, SC Leporati, S Lourenço, A Quetglas, W Sauer, BM Gillanders. 2016. Global proliferation of cephalopods. Current Biology 26: R387-R407.

 

Gillanders, BM, SC Donnellan, TAAC Prowse, D Fordham, C Izzo, S Myers, K Rowling, M Steer, SH Woodcock. 2016. Giant Australian cuttlefish in South Australian waters. Final report to the Fisheries Research and Development Corporation. University of Adelaide, Adelaide. 91 pages.

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Prowse TAA, BM Gillanders, BW Brook, AJ Fowler, KC Hall, MA Steer, C Mellin, N Clisby, JA Tanner, TM Ward, DA Fordham. 2015. Evidence for a broad-scale decline in giant Australian cuttlefish (Sepia apama) abundance from non-targeted survey data. Marine and Freshwater Research 66: 692-700.

 

Catalano, SR, ID Whittington, SC Donnellan, BM Gillanders. 2014. Dicyemid fauna composition and infection patterns in relation to cephalopod host biology and ecology. Folia Parasitologica 61: 301-310.

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Gillanders, BM and NL Payne.  2014. Giant Australian cuttlefish. In: Natural History of Spencer Gulf. (Eds SA Shepherd, SM Madigan, BM Gillanders, S Murray-Jones, DJ Wiltshire). Royal Society of South Australia, Adelaide. Pp 288-30.

 

Woodcock, SH, JL Johansen, MA Steer, SG Gaylard, TAA Prowe, BM Gillanders. 2014. Regional sustainability planning in Upper Spencer Gulf. Investigating potential impacts of shipping on giant Australian cuttlefish. Final report to the Department of the Environment. 54 pp.

 

Catalano SR, ID Whittington, SC Donnellan, BM Gillanders. 2013. Using the giant Australian cuttlefish (Sepia apama) mass breeding aggregation to explore the life cycle of dicyemid parasites. Acta Parasitolgica 58: 599-602.

 

Gillanders BM, LM Wilkinson, AR Munro, MC de Vries. 2013. Statolith chemistry of two life history stages of cuttlefish: effects of temperature and seawater trace element concentration. Geochimica et Cosmochimica Acta 101: 12-23.

 

Payne NL, EP Snelling, JM Semmens, BM Gillanders. 2013. Mechanisms of population structuring in giant Australian cuttlefish Sepia apama. Plos One 8(3): e58694.

 

Payne, NL, BM Gillanders, JM Semmens. 2011. Breeding durations as estimators of adult sex ratios and population size. Oecologia 165: 341-347.

 

Payne, NL, BM Gillanders, RS Seymour, DM Webber, EP Snelling, JM Semmens. 2011. Accelerometry estimates field metabolic rate of giant Australian cuttlefish Sepia apama during breeding. Journal of Animal Ecology 80: 422-430.

 

Payne, NL, JM Semmens, BM Gillanders. 2011. Elemental uptake via immersion: a mass marking technique for the early life-history stages of cephalopods. Marine Ecology Progress Series 436: 169-176.

 

Dupavillon, JL and BM Gillanders. 2009. Impacts of seawater desalination on the giant Australian cuttlefish Sepia apama in the upper Spencer Gulf, South Australia.  Marine Environmental Research 67: 207-218.

 

Wheaton, L, SC Donnellan, MC de Vries, MG Gardner, and BM Gillanders. 2007. Isolation of additional polymorphic tri- and tetra-nucleotide microsatellite loci for the giant Australian cuttlefish (Sepia apama). Molecular Ecology Notes 7: 893-895.