 Hello, my name's Mike Stier. I'm the acting research director of Sadi Aquatic Sciences, which is the research arm of Persa. Today I'm gonna be talking about the science behind the giant Australian cuttlefish. Now there's a place up in northern Spencer Gulf called Point Lowly around Waila that has an extensive rocky reef. This reef plays host to an amazing spectacle. Each winter, tens of thousands of giant Australian cuttlefish aggregate on this rocky reef to spawn. They are attracted to this reef because they lay their eggs or attach their eggs to the underside of that reef. This is an incredible natural phenomenon. It's the only place we know of in the world where you get huge numbers of cuttlefish aggregate on a particular site. And as such, it draws the attention of quite a number of visitors, tourists, documentary filmmakers, scientists, and it's along a stretch of coastline that also has a fair bit of coastal industrialization. Over the years, cuttlefish has been approaching iconic status in South Australia. As I said, it's the only place in the world where you get this massive aggregation. And it's starting to achieve an iconic status up there with South Australia's farmers' union ice coffee, frog cakes, and custard tarts. So a really important population. Now, if you look at this cuttlefish population through time and have a look at how it has developed, the first thing we need to consider is the commercial catches because initially this species was, and still is, permitted to be caught by commercial marine scallfish fishes. So you can see back in the early 1980s through to the 90s, there wasn't much of the statewide catch. This has catch landed in all of South Australia. See, it's around about five to 10 tons per year. But in the mid-90s, we saw this really big increase right up to about 250 tons in 1997. Now, the reason why it increased so quickly is because the fishes found the aggregation in a round point lowly and were able to catch quite a lot of cuttlefish in a relatively short time because these species had aggregated. They were using cuttlefish at that stage as bait for snapper. So commercial fishes would come in, catch a heap of cuttlefish and then use them for bait to then go on target snapper later on. Now, clearly this was indicated as a bit of a concern because of fishing on a spawning aggregation. And in the following year, an exclusion zone was put in in 1998, about halfway through the spawning aggregation, which occurs around May, June and July or in peaks in May, June and July. That exclusion zone eventually covered most of that False Bay area from the BHP Jetty all the way across Point Benyton Jetty to the Lighthouse. Around the same time, there was some work done by a PhD student here in South Australia that started to look at the cuttlefish abundance in that area. And she found that around, or in that year, approximately 100,000 cuttlefish were aggregating on that particular spawning area. Now, you can see once that closure was put in place, then the majority of the catch dropped out because most of this catch was coming from that False Bay area. And you can see that that population, well, that catch has rather dropped down to about 10, 15, 20 ton per year and has not really exceeded since then. Now, the corresponding surveys of the cuttlefish abundance were relatively stable in those subsequent years straight after the imposition of that closure. Around about 150 plus thousand animals. So it seemed like that closure was really good in arresting those commercial catches and maintaining that population through time. A couple of years went past and we were asked, well, Sadi was asked to do another survey in 2005 then the Department for Environment and Heritage because there was anecdotal information that that population had declined. We went out and did the survey and it had declined a little bit but it was still relatively high. And you can see in the corresponding time so that the statewide catch was relatively low as well. In 2008, nine and 10, there was some work done with BHP at the time using the same methodology that was described back in the early days here. So we know that all these data are comparable. And then we saw this precipitous decline down to very low levels, around about 13 and a half thousand animals in 2013 which raised quite a lot of concern because that's a pretty considerable decline. As a consequence of that, a broader temporary fishing closure was put in place for Northern Spencer Gulf because that was the only thing at the time that was considered to be able that the government could control. For us to at least have some time to work out what had caused that decline. And it was a fair amount of funding that was given to the state government and Sadi Aquatic Sciences to undertake some research to try and identify the cause of that decline. Since 2013, we've seen that the population has rebounded quite significantly, really identifying how quickly this fishery can respond. And in recent years, it's although fluctuated on an inter-annual basis, it's been relatively stable. Okay, so there was three hypotheses that we wanted to look at with regards to the decline from the peak of 1999 down to that real low level in 2013. Now, the biggest problem that we had is we had no information of the history of this population. So there's one of three things that could have occurred through time. The first one is, well, perhaps the population has maintained a relatively high level of abundance through time. And what we've seen since that peak in the late nineties of 2000s is a true decline of concern. The other alternative is that perhaps the population just bubbles along at a relatively low level. And then in the late nineties, we saw an ephemeral population explosion and it now subsiding back to those baseline levels. And the third hypothesis is, well, maybe we've got this variation through time with these peaks and troughs in high and low levels of abundance. And we're just conforming to that natural population cycling. So we set out to work to try and identify what was driving this decline. So looking at that first scenario, where we've got a, what we consider a real decline from a large population assessment historically, there's a whole suite of things that we looked at. We tried to pull as much information as we could that was available to us. Information around weather patterns, rain, wind events, coastal pollution, shipping traffic, shipping noise. And then a whole range of biotic effects as well, like the abundance of key predators like dolphins and seals, the impacts of trawling offshore, the catches of cuttlefish from the commercial and recreational fishery. The amount of dive is on site, undertaking tours and snorkeling investigations through that peak spawning area. The prey, cuttlefish tend to predominantly feed upon crustaceans. So we looked at pats and prawns and crabs, the impacts of snapper, which is a key predator for cuttlefish as well. Local aquaculture ventures, disease, changes in the environment, or other cephalopods in the area. So we did a whole suite of analyses and all these analyses are in a report that can be freely accessed by the public and is available on the personal website. And through all of those, there wasn't a real strong signal. We found a signal in rain, so we're at rain in one year. If you had heavy downpours in one year, the subsequent trajectory or the next year's cuttlefish population appeared to decline. So we had this inverse relationship with a lag of about a year. Not too sure whether that was through freshwater inflow, whether it was changes in salinity or whether it was changes in water temperature or turbidity. So there was a whole range of questions that this opened up to us as well. We also saw a positive relationship with prawn trawling activity and effort offshore. We measured the number of cuttlefish in the prawn trawling shots and we found that in periods of high abundance, then you'd get more cuttlefish in those prawn trawlers. So it meant that if they were there, they would catch them. If they weren't, they didn't. We also saw inverse relationships with crabs and calamari. Now, it may be the fact that once the cuttlefish population declines, then the crabs, which are a key diet, key prey item would increase as a function of being predators to control them. And similarly with calamari, if the cuttlefish weren't there, then perhaps that gave the opportunity for calamari to come in and use that area to lay their eggs. So in all, we did quite a lot of investigation and not a lot did stick out at that stage. We clearly saw that fishing didn't have a negative impact or any sort of detectable impact. Diving visitors to the site didn't. And like I said, all that information is in a report that you can freely access. Then we thought, okay, well, if there's a decline here, what is the evidence of that population enduring through history? We looked at some historical information. In 1982, there was a survey done and point lowly looking at, I don't take an environmental impact assessment in relation to the construction of the jetty. Now, this team were looking at indicator species that they could measure in the unlikely event of an oil spill. They went out in the areas that we'd expect to see a large amount of cuttlefish, where the jetty is now. And during winter, when we expect to see high densities of cuttlefish around that time. And the report did not identify large quantities of cuttlefish. I think from memory, only a handful were actually documented. In 1984, there was another survey done in the same area around the same time. And they actually took some video footage and were fortunate enough to get hold of that footage. And we did actually find that there were cuttlefish in those surveys. And we know them to be the right spots because of our understanding of that area, we've actually been able to identify some of the rocks in the footage to verify that they were in an area and time where we would expect large populations or large densities of cuttlefish. They were indeed there, but not in the densities that we would have observed back in the late 90s and early 2000s. And then in about 1986, there was another group that came over from Griffith. They did some work, I think in front of the Santos tanks area and they identified that they saw cuttlefish in those areas, but not at the large densities that were recorded in those late 90s, early 2000s. So it seems like there has been some activity and some cuttlefish in that area through time. However, we can't get a gauge on the relative densities. Although we've spoken to locals that have been there for many years that used to fish from the rocks and have told us that they did indeed catch large quantities of cuttlefish around that point lowly, Fitzgerald Bay, Backey Point area. Okay, so the second hypothesis is, well, was that peak in the late 90s, early 2000s, a population explosion? So did we have low levels of cuttlefish through time and then we saw an event and it's now subsiding back to its natural levels? So concentrating more on the increase rather, the decrease. Now the interesting thing about cuttlefish and other cephalopods including calamari and octopus is they live fast and die young. They typically have what's called a sub annual lifespan and for giant Australian cuttlefish, their maximum age is around about 12, 18 months. So they grow from an embryo in an egg. That egg undertakes embryonic development for a number of months. The animal hatches out as a miniature version of an adult. So there's no vulnerable planktonic phase. It grows relatively quickly, feeds copious amounts of crustaceans, gets to a size of reproductive age and then comes back to mate and spawn and the whole cycle continues. So the interesting thing here is that the population that we see in one year, the spawning population in one year does not endure for two spawning years. So once they've spawned, then they may spawn multiple times over a short spawning season, they tend to die. And in a couple of months after the peak spawning, that's when you start to see large amounts of dead cuttlefish wash up on the shore, particularly in northern Spencer Gulf. There's large washups of dead cuttlefish as they've just expired from spawning. They've then successfully laid all those eggs and those eggs then hatch and then contribute to the next population. And we've seen booms and busts of cephalopods around the world. And there's a good example off the coast of California where the jumbo Humboldt squid, they tend to boom and bust on the result of good environmental or favorable environmental conditions. And from this article it says what's behind the territorial expansion has yet to be determined, but through some observation, they believe a gradual warming of the ocean pollution and overfishing of large predators could be contributing factors. So the key things I want to pull out there is the gradual warming of water and the overfishing of large predators. Because these guys live so fast, their growth trajectory is highly, highly governed by environmental temperature. The warmer the temperature, the faster they grow. And of course, if there's no large predators through removal of fishing, for example, in the case of the Humboldt squid, it creates a situation for that species to proliferate. So what came out of that too was that perhaps cephalopods in general could be the key beneficiaries of global warming. And we've seen that in multiple species around the world. But another interesting thing that was mentioned here was that the Californian Humboldt squid appeared to expand its territory or shift its territory. We thought maybe the same thing was happening with giant Australian cuttlefish. Now we know in Northern Spencer Gulf the giant Australian cuttlefish is pretty much a separate species or separate subspecies or subpopulation to the rest of the state. There's very little mixing of the Southern Spencer Gulf cuttlefish and the Northern Spencer Gulf cuttlefish, even though giant Australian cuttlefish do occur throughout the entire Southern Australian range. But anyway, we know that the population that we are interested in is confined to that Northern Spencer Gulf. We also know that the region up around Waila is where we see large densities of cuttlefish, okay? So what we thought we'd do is look at other areas in and around Spencer Gulf that had similar habitat, similar rocks, similar substrate to allow the female cuttlefish to lay their eggs. And we undertook an extensive survey in these four zones and we found nothing actually. Now granted, we were looking at a time around 2013 when the population was really low. But we didn't see a shift in that population. And what that did tell us, however, is that population up in Northern Spencer Gulf, around the Point Lola, that Point Lola spawning aggregation is incredibly important to the overall population of the Northern Spencer Gulf cuttlefish. Then if you look at the third scenario where we have this fluctuation where you go in peaks and troughs and booms and busts and population abundance through time. And that's something that's consistently seen in the cephalopod literature. You see these big peaks and troughs in a range of cuttlefish, squid and octopus species. Now, like I said before, it's really driven by a number of environmental processes. One could be related to the amount of prey or predators that are available or in the area at that time. If there's not very many predators, then cuttlefish, for example, would increase. And then vice versa, if the predators, the levels of predation increases, then it tends to cap the abundance of prey. And the other thing we've seen with cephalopods in general is that temperature is a real key driver in the rate of how these species grow and proliferate. Now, the trophic web of cuttlefish or where it fits in is quite complex. We understand that seals and dolphins and snapper and other large fish, salmon, kingfish, et cetera, natural predators of cuttlefish. And we also know that cuttlefish prefer to eat small crustaceans and small fish and even other cephalopods and each other. So we can see very complex relationships there. So we may be seeing some changes in that population on the basis of shifts in predator and prey availability. So when we weighed up all that information, we seemed to take a weight of evidence approach that indicated that this third scenario, third hypothesis was the most likely scenario where we're seeing these peaks and troughs and population abundance through time. But at this stage, we still had very little information to support. But if we look what's happened in subsequent years, so we can see where we've had or no surveys back in the early, or the 80s and early 90s. We've seen our surveys in the late 90s. This one here was where we were impacted by fishing. These ones were after the immediate closure. We've seen that decline down to about 13 and a half thousand animals in 2013. And we've seen this rapid increase. And now a population that's pretty much returned back to historically healthy levels. Now, remember I said that the cuttlefish embryos take a long time to develop. And the reason why cuttlefish aggregate around that point lowly area is because of the rocks. They need to attach these eggs to those rocks. Now it can take a couple of months for these embryos to develop into hatchlings. And what they tend to do is hatch, maintain, live within the rocks until they get a certain age and size and they migrate or disperse out of the area into the Gulf. And once they achieve sexual maturity, they come back. But what we did is we've got some temperature loggers out there and we've just been looking at trends in temperature during that embryonic developmental phase. So we're looking over an 18-week period here. And we can see that during that time, you can get periods of increasing temperature towards the end of their development and periods of decreasing temperature. Now, if you look at both of those, you can see that in the warm years, we've got 2013, 2014, 2015 and 2017. And in the cool years, 2009, 2010, 2011 and 2016. Now if you overlay those temperature years, all those cool years with the population, you can clearly see that while we've seen a decline in that cuttlefish abundance and currently it appears that the temperature or the incubation temperature for these embryos is the best indication that we've got so far for that declining population. And if we look at the warming years, we can see while we're starting to see a population increase. Now, it sort of makes sense because if the animals are accelerating through that embryonic phase, they will grow faster and accelerate through that period of being vulnerable to production. So it suggests that they've got an increase or the hypothesis is they've got an increased probability of survival. And if they survive that earlier phase, then there's a greater chance that they'll contribute to that subsequent spawning population. So we can see the cool years of matching up with the decline and the warming years are matching up with the increase. Now, if you look at 2016, that was a cool year and you can see that the subsequent population had declined. 2017 was relatively warm and well, the population had increased. So there is some signal there worth exploring in more detail in future research. Now, the issue with trying to get a handle on population dynamics on cephalopods and undertaking the appropriate management for them has been very difficult. And there's numerous texts on cephalopod fisheries biology that says that the significance of the effect of stochastic variables on annual species is really extreme. So this means that the populations can bounce around quite largely on an annual basis. And it's the main reason why it has proven difficult to establish a reliable assessment and management procedures for cephalopods. Now, this is a continual challenge for cephalopod fisheries biologists and fishery scientists throughout the world. So in summary of this presentation, point lowly is clearly a very important spawning ground as an essential component of that population. And particularly that area that is permanently closed. In the analysis that we've done to date through looking at all lines of evidence both in the marine scale fish fishery, the prawn fishery, et cetera, we found no clear impact of commercial fishing on the protected spawning population. And of course, we've got a lack of historical information, although there's some information to suggest that the population has been there in various levels of abundance through time. Clearly, as we've seen with the rapid rebound in that population since its low in 2013 that the population is highly responsive and variable. And so far, incubation temperature with the embryo the embryos appears to have the strongest influence. So knowing this information, it's really important that we continue to maintain those annual population surveys so we can track that population through time. And it's equally important that we monitor commercial and recreational catches both within the area and throughout the state to make sure that they're operating in parallel and not having or not providing any sustainability risks to what we consider an iconic population in South Australia. And clearly protecting those known spawning grounds along that Point Lely Stretch, False Bay Area is the most appropriate approach to maximizing the supply of eggs to buffer against that unpredictability of the environment. So hopefully the information I've pulled together today has provided you with a bit more knowledge about the species. And like I said before, there's a whole suite of reports science and literature that is publicly available on the PERSA website. Thanks very much for enduring the time and listening to me for about half an hour. Thank you.