Giant Cuttlefish: Undetermined decline
In the late 1990s, more than 180,000 giant cuttlefish gathered to breed in South Australian waters. Since then, their numbers have dwindled by 93 per cent and no-one is sure why
AT FIRST GLANCE, the Lowly peninsula near Whyalla in South Australia appears unspectacular. Its most obvious feature is a rusted, 2.4km-long jetty at Port Bonython that vanishes into the horizon. From the rocky shore, few could imagine that, just 100m away, a pulsating, iridescent mass of 180,000-plus giant cuttlefish once thronged beneath the waves. Discovered in the late 1990s, this aggregation of the world’s largest cuttlefish was a magnificent wildlife spectacle and attracted international filmmakers in their droves.
But for reasons that aren’t clear, despite much research, numbers congregating here have dive-bombed, collapsing by a massive 93 per cent to just 13,500 in 2013. Whether the crash was caused by industry, over-predation by marine mammals or simply natural population fluctuations are all questions to be answered. Some experts even speculate the aggregation itself represented an unusual spike that has now passed, but the population here has been studied by scientists for less than 20 years, so nobody is yet sure.
Divers lucky enough to have witnessed the aggregation at its most spectacular describe it as a great rainbow-coloured swarm that blankets every rocky surface. Cuttlefish could be found at an average density of one per square metre over a 60ha area of the Spencer Gulf. Although the numbers have fallen, during the May–June mating season males still outnumber females four to one and their jostling often breaks out into bold physical displays and rapidly throbbing patterns, their bodies glowing as if lit by LEDs. Just as impressive as their burlesque-style outfits is the ability of these masters of disguise to rapidly alter their colour and shape to hide in plain sight: moulding and positioning their tentacles to appear like the yellow, crimped curls of algal fronds, or mimic the darker patterning and texture of mottled rock shelves.
That’s not where their strangeness ends. “They have three hearts, this doughnut-shaped brain, blue blood, a beak, eight arms and two [retractable] feeding tentacles,” says Alex Schnell, a marine ecologist studying cuttlefish at Macquarie University in Sydney. “It’s pretty much the closest thing you can get to studying an alien without leaving our atmosphere.”
The giant Sepia apama is the largest of the world’s 120-odd cuttlefish and part of the cephalopod group, which includes all squid and octopuses. Male giant Australian cuttlefish can reach 1m in length and weigh up to 16kg, about the size of a small dog. Females are slightly smaller, and they lack the two broad banner-like outer arms that males use in mating displays. One of 26 Australian species of cuttlefish, they are found across our southern coast, where they typically travel the sea floor alone. Only at Point Lowly, 230km north-west of Adelaide, do they aggregate en masse, and the reasons are mysterious.
After a few weeks, just as abruptly as they arrive, they disappear, the females having glued batches of their large eggs under rocks. And it’s for good, because the cuttlefish only live for 12–18 months and mating is the final act of their short lives. All their energy goes into reproduction and they often fail to feed during the mating season, says Alex. “It’s strange to watch, but they just begin to look really haggard and eventually die.” Come September, cuttlebones begin to wash up on South Australian beaches.
Mating strategies of the cuttlefish
ONE OF ALEX’S PhD supervisors is Dr Roger Hanlon, a world expert on cuttlefish at the Woods Hole Marine Biological Laboratory in Massachusetts, USA. In January 1998 Roger was drinking beer at a pub in Port Lincoln 250km south of Whyalla. He’d been studying cuttlefish off the coast there, but knew nothing of the aggregation.
“Playing darts one night…I met one of the young researchers on the team from Adelaide, Karina Hall. I said I was studying cuttlefish and looking around the world for a good breeding site to study sexual selection and she says, ‘Oh, we’ve got one of those just up the road here. In fact I’m starting to do my PhD on them.’”
When studying cuttlefish elsewhere, it’s typical to find just a single animal. “I’ve been searching for 40 years and working with cuttlefish in Turkey, the Mediterranean, Spain, Micronesia, Indonesia and Egypt,” Roger says. “Nobody’s found a place with cuttlefish aggregating with more than, say, 10 individuals.”
Karina told him there were tens of thousands at the site near Whyalla. Roger didn’t really believe her, but flew out again in June to look anyway. On his first dive he was astounded by the numbers.
“I looked at 20 cuttlefish mating nearby and thought, ‘I’m definitely coming back.’” He later told The New York Times that he thought he’d “died and gone to cuttlefish heaven”.
Following that first 1998 season, Roger has commuted almost annually from his Massachusetts lab to Point Lowly, collecting a huge library of footage. “For sexual selection studies, it’s the best field site ever discovered,” he says. Roger’s lab is full of cuttlefish that can mimic just about any background, from sand and pebbles to stripes and even chequerboard patterns. Although much of his work on how the cuttlefish camouflage themselves is done here, some behavioural research can’t be done in a lab, he says.
Of the many papers Roger and his colleagues have published, he is proudest of one in the journal Nature. It was an observation of five Whyalla cuttlefish that mimic females. These small males squeeze their arms up tight to their face and colour themselves like females in the invertebrate version of ‘dragging up’. Instead of fighting, they simply sneak past bigger suitors and mate
with the females.
Mimicry is common says Roger, but their paper got attention because they had DNA proving that two of the five mimics impregnated their targets. It was the first published proof that this strategy is effective. Roger reasons that the females are probably trying to get a mix of skills into the gene pool of their offspring. And the mimics “have increased, if not doubled, their chances of fertilisation success by being crafty little guys”, Roger says.
Declining population of the giant cuttlefish
Fishers first noticed great numbers of giant cuttlefish in the Spencer Gulf in the 1990s and began hoisting them out to freeze and export to Asia, where they are used in dishes in the same way as squid. At that time, Dr Karina Hall was a student working for the South Australian Research and Development Institute (SARDI), and she started investigating cuttlefish biology to underpin management of the fishery. But she found almost no research, she says. “All of the information you need to manage a population was missing.”
In 1998 Karina persuaded the Fisheries Research & Development Corporation to fund her PhD on the aggregation. Her research showed that 244 tonnes of cuttlefish – perhaps 30,000 individuals – were caught by fishers in 1997 alone. Despite the dearth of data, it was clear that the population was vulnerable.
Following lobbying by local divers led by Tony Bramley, a total ban on harvesting them around the Lowly Peninsula was negotiated, and has now been renewed 14 years in a row. Despite the moratorium, SARDI figures show a steep decline in numbers. From an estimated 183,000 in 1999, numbers were down to 125,000 in 2005, 80,000 in 2011 and just 13,500 in 2013. Researchers are now looking for answers to this seeming catastrophe. Dr Mike Steer at SARDI and Professor Bronwyn Gillanders at the University of Adelaide are heading projects funded by $715,000 from state and federal governments.
Mike says there are three potential explanations for the decline. It may have been caused by new environmental pressures, such as pollution, changes in water temperature or a decline in a food source. Another idea is that it may just be part of a normal long-term cycle. The final possibility is that it’s not a real decline at all, and that the huge numbers found at Point Lowly in the late 1990s represented an unusual boom.
“It could be that there was a cephalopod population bubbling at a low level and then…there was a population explosion,” Mike says.
Karina isn’t so sure about this and says demographic features of the population “suggested that it had been at that density for quite some time”. Some experts list environmental factors that may have put pressure on the population, including pollution from local industry (such as the Whyalla steelworks, the Port Bonython gas fractionation plant and kingfish and snapper farming), and shipping traffic in the Spencer Gulf.
Other possible pressures include climate change and population booms in predators, such as fur seals and dolphins.
“I just don’t really know,” Karina says. “Because they only breed once and have a short life span, anything affecting them shows up quickly in population numbers.”
Mike agrees that the speed of their life cycle complicates matters: “They hatch as tiny, fully formed cuttlefish, about the size of your fingernail, and grow really fast… It’s hard to get a handle on what’s going on.”
In the course of his research, Mike has uncovered a jumble of conflicting stories about the history. Local folklore suggests that nearby Black Point was named for the ink in the water after snapper hunted huge numbers of cuttlefish. Some fishers said they were catching cuttlefish back in the 1970s but Alan Hall, a veteran of the local fishing industry, says numbers only rose when snapper were “cleaned out” by heavy catches in the late ’90s. Another scientist at Whyalla in 1982 says she didn’t see any cuttlefish at all. “This was a surprise,” Mike says.
There are still so many unknowns. Nobody knows how, or why, the cuttlefish navigate to Point Lowly, or even where they migrate from. Bronwyn says it’s the only place in the upper Spencer Gulf with the appropriate rocky substrate onto which they can glue their eggs. “So that could be why they find their way there, but we don’t know how they get there,” she says.
The new research projects are attempting to fill these gaps in our knowledge. Mike’s team is monitoring numbers caught as bycatch and is looking into creating artificial spawning grounds in alternative locations with concrete blocks. They are also testing the idea that the cuttlefish have simply moved elsewhere by dropping video cameras beneath the waves at 37 Spencer Gulf sites that have rocky habitats.
In the marine sciences building at the University of Adelaide, Bronwyn’s group is studying the effects of noise and water quality on cuttlefish eggs and also analysing DNA to see if the Point Lowly population is a distinct subspecies. If so, she says, it may be possible to list them as endangered or vulnerable, with implications for conservation.
Attempts to address the population decline
IN THE BBC’S 2009 natural history series Life, Sir David Attenborough talked millions of viewers through a scene in which a male giant cuttlefish mimics a female as he tries to have a secret tryst with another male’s mate. The film crew behind this footage was one of many, from as far afield as Chile and France, who made the pilgrimage to Whyalla to film the spectacle before the steepest decline in numbers kicked in.
Roger’s footage was also the highlight of a TED.com talk that has been watched online more than 10 million times. “It’s pretty evident,” Roger says, “that the rest of the world knows more about the giant Australian cuttlefish than Australians do.”
In July 2013, AUSTRALIAN GEOGRAPHIC photographer Ralph Alphonso was one of very few who braved the frigid waters off Point Lowly and he emerged with shots of half-a-dozen cuttlefish after several hours. Whyalla dive-shop owner Tony Bramley says Ralph was lucky to shoot even six. He laments that, as the cuttlefish have declined, so has the local tourism industry.
It used to be very different, says Tony, who goes as far as speculating that increases in shipping may have played a role. “Last week we had the biggest cape [class] vessel that’s ever been here – it took on 200,000t of ore,” he says. “We were out there [diving] the other day and one of them took off. You could see the water at the back of the vessel thrashing, frothing and a huge wake developing… All we could see for hundreds of metres was this silt plume. Those vessels are 17m deep and the seabed is only 20m, so you can imagine when those massive turbines get going, the disruption out there is tremendous.”
Despite experts not yet having a good handle on how environmental threats have played a role in the decline, there are plans for new industrial projects at Point Lowly.
BHP Billiton is hoping to extend its Olympic Dam mine – making it one of the world’s largest gold and uranium mines – but the expansion hinges on a desalination plant to be situated at Point Lowly. Water would be piped from there to the mine, 290km to the north-west, and, although scientists have concerns, BHP argues that brine emissions will be minimal.
There are also plans for a deepwater port for iron-ore exports, but a group of local steelworks engineers is lobbying to get this moved further south away from the aggregation, says Sid Wilson, spokesperson for the Alternative Port Working Party. He has been a Whyalla resident for 60 years and was once the engineering manager for the area’s largest employer, OneSteel. “We’d like to find a solution that works for everyone,” Sid adds, one that allows industry to continue without hurting the cuttlefish.
Creating awareness for the cuttlefish’s plight
IN MARCH 2014, 230km from Point Lowly, a 13m float in the design of a brightly coloured flashing cuttlefish paraded down Adelaide’s main street. This float, named Stobie, was the mascot of the city’s annual Fringe Festival. Dancers shimmied around it to the insistent disco beat of the Bee Gees’ Stayin’ Alive. The people dancing and clapping along to the rhythm may have had little idea about the plight of Whyalla’s cuttlefish aggregation, but Stobie’s appearance as a mainstay at this popular arts festival signals that awareness of the special connection of the species to South Australia is on the rise.
Organisers of the Fringe, however, were later criticised for failing to grasp the opportunity to add an environmental message to Stobie’s weekly extravaganza. Filmmaker Dan Monceaux told local newspaper the Whyalla News, “The northern Spencer Gulf population is at its lowest ever recorded. I’m concerned that the disco cuttlefish will trivialise what is potentially our state’s greatest environmental shame.” But, who knows, perhaps the bitter irony of the disco-dancing cuttlefish’s theme song may yet prove a wake-up call for us all.
The full story can be found in Australian Geographic #120.