Fish behaving badly
Thank you everyone for coming this evening. I see a lot of familiar faces in the audience. When Lisa from the Faculty of Science approached us about doing one of these talks I thought well, why don't I just come along and introduce two stellar young postdoctoral fellows in my lab, and I'll just sit down and enjoy it. Unfortunately they're a little more savvy than that and they insisted that I actually produced some goods as well.
So I'm going to start off by talking a little bit about - generally about fish behaviour and the way humans affect that, and unapologetically looking at some of the examples that we've been looking at in our lab. Now having seen the faces here, I see a lot of experts in this area. So I'm sure I'll disappoint some people with my detail and others will start yawning. So I'm going to try and tread the middle ground. We'll see how we go anyway. All right, so just generally - and this is not an extensive review but scientists love boxes and arrows and things. I'm no exception.
Fish behaviour is a thing near and dear to our hearts. I hope by the end of this talk, you'll understand why it matters a little bit to humans. But it can be affected in a number of ways. Here is just a couple of categories. In no particular order, fishing obviously can have a direct, or maybe an indirect effect on the fish that are caught.
Pollution, which being in Sydney you can't avoid doing a little bit of research into the effects of pollution on fish. The stuff we put out there - artificial habitats for enhancing fishing or for oil surveying, et cetera. What have I left out? Climate change, I had to throw that in there. It's very pertinent at the moment.
All these things have the potential to affect the way fishes behave. That in some cases can affect the way we catch them or enjoy them. So there is a bit of a 'so what' there, we sometimes get fishes behaving very badly, leaping into sewer pipes, but maybe we're not talking about such extreme things in general.
So I am going to go through a few of these now and I can expand later, or maybe some of my colleagues here can talk about some of their work. Then leave it up to the others to give you some in-depth examples.
So climate change - we probably don't have too many climate sceptics in here so hopefully I don't have to battle that. But certainly we're in a very good spot to study this, it turns out. A famous map that some of you will know it and be familiar with that we based some of our justification for doing the work here.
Australia it turns out has one of the ocean climate hotspots. Pardon the pun. That southeast Australian region aka just off the coast here, is an area where the ocean is expected to change quite rapidly over the next century, and already has. We have some evidence that it already has in a number of ways, including temperature. So we have been in our lab, in conjunction with others and people working through the Sydney Institute of Marine Science, looked into different ways in which temperature and other climate changing factors might affect the behaviour of our little fish friends.
So just very simply, there are three main areas that we are interested in. They are all linked together to let us know what's going to happen to fish off our coast.
It's esoteric and interesting to biologists. But also it's interesting to people who like a feed of fish et cetera, et cetera - what's going to happen.
So the main areas are changes in the ocean currents that we have around here; changes in the temperature which probably most people know about; and also probably a more new and a little bit more unknown one is how the pH - the acidity of the ocean is changing. Ever so slightly but it turns out, the ocean is a very stable entity and even a slight change, the animals and plants there have not evolved to accept that change. So these particular areas.
So ocean currents - just very quickly. We have a lovely south flowing - poleward flowing current called the East Australian Current. Someone gazumped us on this one with a movie. But in any case this current brings tropical waters down to southern - way down into Tasmania even, on a seasonal basis, mainly over the summer. Well it just so happens that that’s a very good timing if you're a baby fish, or bad timing if you don't want to go down there. It's when a lot of these fishes spawn on the Barrier Reef, hatch and some of them are not great swimmers at first and they can head on down the coast of southeast Australia.
So they can disperse. Half the people here will be aware of this; the other half it might be a surprise. These little animals which may be the size of my thumbnail, can disperse thousands of kilometres down the coast. A lot of it through drifting with the currents but they also have an amazing ability to swim.
I won't go into all the interesting relationships between water temperature and swimming, but there are some. So with the fact, the well-known demonstration that this East Australian Current is going to get stronger, we might expect more of this warm water and more of these little baby fish to come down the coast. It appears that that is what's happening.
So, I suppose the good news is we mightn't have to go to the Barrier Reef to see our little fish in future, but the bad news is we’re seeing some evidence starting of some of these temperate fish, some of the southern fish, not coming as far north, heading south. Sadly, if you like eating fish, many of these species are ones that are good for the table.
So New South Wales already was fairly marginal as a highly productive fish area, might get a little bit worse. So that's not very good for us humans. That’s an affect for us.
These are some data that we plotted up in a paper and it's - Sydney's here, Merimbula down on the south coast here and here's up on the reef. You can see way back in time, there was even perhaps - potentially a decrease of maybe a degree in ocean temperature. But there's a consistent increase in temperature over the last few - over the last decades, especially down south. You'll see the little tiny squiggly line there is year to year variation in winter temperature.
So we have some extremely warm winters coming along in the last few years. In those warm winters, surprise, surprise, we see more of these little tropical babies surviving. So not only are they coming down more - probably more often with the current, once they're here they often don't survive. Most of them don't. The last few years on especially warm winters, we are seeing that happen.
So in this - these two little Butterflyfish - very cute and very commonly occurring in summer - mostly die off. But if the sea temperature gets above 18 degrees, we get more and more surviving. They can handle it. They can behave in such a way that they can survive, and it turns out that Sydney is right up the cusp of all of this. Some - mostly our winters are less than 18. Any surfers out there will know that.
Occasionally we get these lovely warm winters like 2001 and 2006. I well remember them, nice for diving in the winter. In those winters, we had more overwinter survival. So we've projected, based on those climate projections, that in a few years we'll get more and more of those fish potentially eventually reaching breeding proportions.
Another thing with temperature is fish have a temperature relationship with their ability to swim. It turns out that these little tropicals that come down have a really strong relationship between the temperature of the water they're in, and their ability to swim fast and furious, and get away from predators.
So in this particular example, this is one of our little tropicals. This is a local little Damselfish that is related to it. It acts quite similarly. In lab experiments - which I won't explain, they're a little bit gruesome - we find that at the normal temperature in and around Sydney, a cooler temperature, these particular fish do not swim away from predators as fast as their little locals.
However when you elevate the temperature, there is a strong - there begins to be a strong temperature relationship. These guys get faster and faster. Above this temperature, it's likely that these little fish will be better able to escape predators than those ones. So as the temperature rises, we may well see a sort of a shift in competitive dominance amongst these fish.
Give up on that, I think. Okay, also and just to show that we’re not just highlighting our own work, the other area of interest that is gaining in importance, is this idea of ocean acidification. Increased CO2 in the atmosphere; absorbed into the ocean; more CO2 in there plus a slight drop in pH. It's been well demonstrated that things with shells, calcium carbonate shells, are not going to do to well because that calcium carbonate may well dissolve at that lower pH.
But really new information from our colleagues at James Cook that we're doing parallel experiments with right now for temperate fish, show that both the predators and prey on the reef - these fish behave badly, if we want to get back to the title I suppose.
In this particular example, what they’ve shown is that at low - at normal CO2 concentrations, there is a certain response time for a predator to a prey. As you increase that concentration, it goes up significantly. So the poor old predator - in this case a Dottyback, a very common predator of the coral reef, is slower to catch its prey and it seems to be an ocean acidification effect. The mechanisms I can go into later but they are not simple and they're neurological that they're working on at the moment. Old Nemo, a potential prey right there, doesn’t do too well either.
In this case, these laboratory experiments have shown that if you arrange a tank that there is the smell of a predator over here and no predator over here, you'd expect a smart little fish to spend most of its time away from the smell of a predator. We know they’re very good at smelling and avoiding them normally. It turns out, what happen is - and you can't even see the little bars that talk about the amount of time that little Nemo spent near the predator. Zero. Once you start adding or dropping the pH and that’s these bars you'll see here, the fish starts making some very bad choices.
It seems to hang out, not only 50- 50 - it seems to hang out more often in the predator part of the tank. A very bad choice that seems to be linked to a slight drop in ocean pH and an increase in CO2. So who knows how these guys are going to fare in the next 80 years, hopefully we will.
Okay, so just switching gears slightly. Another way in which fishes can interact with humans in a not so good sense I suppose, is through our water pollution. There are many aspects to this. Obviously I'm not going to go through everything. There is sedimentation; there are heavy metals; there is even thermal pollution and all these things can affect the way little fishes behave. In fact what I briefly want to talk about is some of our work on some very interesting class of chemicals called endocrine disruptors.
Now these are chemicals - I can't even read that up there, but they were some of the other options. So endocrine disruptors are a whole cocktail of chemicals, or a suite of chemicals. Everything from birth control pills and the like to domestic and industrial by-products and other components in sewage, which of course we dump straight into water ways around Sydney in some sort of treatment form.
It turns out that these chemicals, make male fish put on lipstick, which is a bit difficult in water but in any case. So one of the phenomena that happens, appears to be feminisation of males. This has been recorded all around the world, it’s a bit of a pop science topic for many years. Alligators, fish, et cetera, and of course there's even some human examples of this sort of thing.
What we’ve done around Sydney - and what a lot of the work's been done on, is fresh water fish. So it's been well known in fresh water fish - and of course part of the reason for that is fresh water concentrates our pollutants very much. The ocean and estuaries it kind of dilutes a bit but obviously not enough. Some of these chemicals that do this, like oestrogens from the birth control pill - even in tiny, tiny quantities, almost impossible to measure, it can affect fish reproduction. This particular example I think is the only or one of the first ones that on an estuarine fish. Not a very sexy fish in the first place, but it got worse.
This is an Estuarine Toadfish. It turns out that they are very, very common, which is very nice if you want a sample in all sorts of places. So we've done a fair bit of work with them. One of the pieces of work was to look at the blood of these things. Now a female worth its salt will have yolk protein in its blood, that’s fine. In these particular examples, this is a reference creek and a polluted creek. The females - the little stripy ones - just about all had this vitellogenin, this yolk protein. I don't know what happened with this one but in any case. The males, it turned out in the reference creek - in the nice clean areas - none of them had any of this yolk protein.
But nearly all the males in the more polluted areas - and this was a mix of sites in Sydney Harbour, around Homebush Bay and next to a sewage treatment plant up on the Hawkesbury - just about all had this yolk protein in their blood, indicating that there was some endocrine disruption. We don't know the source, probably sewage, who knows.
Now a whole lot of consequences happened there, potentially. It's been shown in other species. We’ve got to follow up this up with this fish. Reduced courtship; reduced aggression, especially for fish that have to have some sort of dominance hierarchy to breed in - competition, all those nasty things that you can imagine could disrupt its reproduction. So these all seemed to occur because of chemicals in the water.
Finally on my little example is artificial habitat. Now artificial habitat could have a positive or negative effect on fishes. So I'm going to talk about some of the potential roles. So obviously there is a lot of artificial habitat out there. Dams and weirs are a major factor. New South Wales of course is one of them. But all around the world, we like to stop water for various reasons whether for fresh water or for turbines, electricity. So all of our rivers just about are dammed or have weirs in them to some degree. It’s a real issue for fish passage. Now some of the species the anglers like to catch like the Australian Bass. These things have a life cycle that involves an estuarine and a freshwater component. Those little suckers move up and down.
Eels, which we’ve done a lot of work with and most people go, eww eel. But they’re an amazing creature, with an incredible life history. They can be almost totally derailed by a dam, because the females in this case come from the open ocean, spend some time and a lot of them move right up the river. So we did work in Georges River, where they put a little fishway at Liverpool and we’ve tracked the fish with telemetry. Those females will go up the fishway. But without a fishway, we'd have some problems.
Ships of course are an issue. So that’s an artificial habitat floating around there. There's lots of interesting studies including in our lab, of them as vectors for exotic pest fish that come into Sydney Harbour, Melbourne, et cetera, and can really decimate things.
But I want to talk mostly about artificial reefs in my final little bit here. Sea walls and artificial reefs obviously could well be habitat for fishes and food for fishes as well. You're probably all familiar with an artificial reef or a seawall attracting fish, or appearing to attract fish. Indeed these things have been either dumped in, or very carefully put in, all around the world. It's becoming a very, very - a major industry. There is some really good science starting to happen in this area.
Obviously some of the reasons for doing this are listed there. Recreational fishing; to enhance fishing opportunities; and some people say to boost fish stocks. That’s the little bit I want to talk about.
They can be barriers to fishing. So for instance in - off Spain in the seagrass, they actually put artificial reefs there to stop the trawlers going through and decimating the sea grass beds. Storm protection - rows of these are all over the show. I think there's - as reefs off the Gold Coast too. In some cases reefs to increase the surfing potential and as diving opportunities, like the HMAS Adelaide which has recently sunk.
I think that’s a whole bunch of trains being dumped too, which is kind of interesting. A good way to get rid of stuff but also potentially if done correctly, a good way to enhance fish production. In theory, that’s a movie and it might be a movie.
In any case, we have as Ruben mentioned, engaged in a lot of recent work looking at the role of artificial structures in the deep sea. Now we've been working with the oil industry for lots of reasons. But one of them at least is they have access to the deep sea. We don't have the capacity in Australia to get down there; maybe tow a net or something. To actually look down there, we've really benefited by working with them and using their remote operated vehicles. So that’s not very deep, that's 135 meters out off the northwest shelf. One thing that you immediately notice is the huge build up of fish. Now others in the audience will notice the huge build up of invertebrates and they're there as well. But certainly the fish appear to be attracted to the rig.
Since it is fish behaving badly, I thought I'd put this one on.
Unfortunately not all fish react in an appropriate way to a deep sea structure and if you look carefully - it's not a great video - there's a marlin who didn’t quite do it right. He is behaving badly so at least I've got one in. That particular animal was actually expertly removed with a remote operated vehicle. If I had an hour I would show you and it swam right back in three times. So I don't know what happened to - so it's not all beer and skittles for a fish that comes near a reef, let's just say.
Now one of the important things that people don't know and probably should, is the value of these reefs to increasing the production of fish or the welfare of fish. So the standard thing you see is a bunch of little fishies around an artificial structure.
The question is there's at least two alternatives. One is, it’s a better deal than somewhere else - a natural reef and all these fish just go over there. The other potential is, there is a bit of seeding from other reefs but then it produces its own stuff. It's sort of self-sufficient if you like.
So you would think there would be really - a lot of demonstrations of which of these two were happening on reefs, but it turns out not very much at all. So my little cartoon suggests a fatal attraction could happen. A natural reef - a nearby artificial reef could attract fish off a natural reef and potentially into the basket there. So what happens is natural - artificial reefs could be easier to capture fish and in fact that’s one of the goals of putting in some artificial reefs.
So I guess the point I make is that I think a lot more science needs to be done. I say that because we're starting to do that science, on the behaviour of fish around reefs - are they being attracted? There's ways of doing this. We are addressing this in the deep sea to a certain degree. We - by a number of methods - and one of the things we've been lucky enough is to be around when they're actually removing structure from the deep sea. So they slap it up on the deck and we can sample it and see exactly what's there. One of the things you look for is, are all size classes of fish present or is it just the big ones? If it's just the big ones, we're pretty sure they’re not breeding.
But when you get a whole size range of little guys and you examine their reproduction, you can start to get an idea about whether that particular structure is actually a fish producer or just a fish sucker-inner, if you like. So that is ongoing.
It's interesting to see the different states and their attitude towards the reefs. In New South Wales, there is a heavy emphasis on the ability of reefs to foster fish stocks and improve scuba experiences. They may well do that. There is a huge off shore artificial reef infrastructure going in, and ostensibly to increase fishing opportunities. But I think the unwritten assumption is that it will improve fish stocks. So I just think the science needs to be completed and continued on that.
As opposed to the government of South Australia, which doesn’t seem quite as enamoured by artificial structures. So obviously there is some debate. Science can step in. Fish behaviour is at the core of the whole issue and more needs to be done.
Finally, [ecosystem] interactions; this is just a way to spin a little story on sharks actually. My final simple example concerns White Sharks. I have a student working on those now but I had a student for five years doing her PhD on sharks in South Australia.
Now that’s a very famous ecotourism hot spot for sharks. Rodney Fox, a crazy man who was attacked by a shark in the 70's and now makes a living out of them. She worked with him to do her shark biology work. She asked two questions. One was about where the males and females go in the winter; and the other one was about whether by feeding these animals, you were increasing their chance of coming back and attacking other people. It's very controversial in South Australia if you ever go there. So yes, these lovely opportunities happen because they bait the reefs. This is just quite a poor promotional video from Rodney Fox.
Basically they bring the sharks in, or we brought the sharks in with lots of bits of tuna. It seems fairly logical that sharks aren't stupid and they would come back for more. So one of her simple questions, which of course is much more difficult when you're working with White Sharks, was to ask the question, do sharks hang around for more? So one of the ways she did this was to do some tagging. Tagging individuals and also using the fin shapes to decide whether they were the same individuals. It was all at the same time that a - every now and again an Abalone diver gets eaten or whoever. You get these sorts of headlines - diver feared dead in horror shark attack.
So these are incredibly strong headlines and this idea that baiting leads to a rise in Great White Shark attacks. Well just to cut a long story short, a little graph belies a lot of hard work. The fish were tagged individually and most of these fish were only ever seen once. So they had their bait, they went and they ate a seal somewhere else or whatever. There's plenty of other food out there.
So on this you'd say bait conditioning is not really a big deal until Johnny came along. There's Johnny down there, and Johnny came back 38 times, so yeah. You may well say it only takes one to be afraid - to be a concern. So in general, you'd say bait conditioning is not a big deal except for that guy. So I think he still looms around there. I don't know if he's been responsible for shark attacks but it wouldn’t surprise me.
So that’s enough from me. So what I want to do now is introduce you to my two colleagues, who are doing postdoctoral fellowships here and will tell you some really interesting, in-depth examples about the way humans and fish interact and what that means. So thanks.
Dr David Feary:So yeah, in terms of what we're trying to talk about today, is really the role of how we're affecting fishes. Dave touched on the idea of overfishing. But it's a really - it’s a global problem. It's one of the things that we're really interested in looking at, and we're really trying to figure out the ways of helping a lot of places deal with their overfishing.
The stuff I'm going to talk about today is some of the work I did just before I came here, really looking at tropical regions and the idea of these communities that are intricately associated with their coastal resources. So these are small tropical communities that really need those fishing resources and rely on it.
So a lot of the problems in these kinds of places are due to the fact that it's such an important resource for them. We are talking about small communities of 2-3,000 people on a small atoll in the middle of the Pacific. When you're in the middle of the Pacific and you don't know where else to go, you're obviously going to make the most of the resource that is close to you.
In the tropics, really it's such an important resource. Around 6 million tonnes is kind of taken out each year, just within the tropical regions. A lot of our ideas on trying to restore areas or at least reduce the amount of use of the resource is to use what we would call a marine reserve - some sort of nature reserve, a non-take area - another word that they use.
These can be extremely successful. In terms of the tropics, there's not a huge amount of examples. The Great Barrier Reef is obviously a really good example. But I wanted to use one in the Philippines. It's called Apo Island. It’s a very small island, off the main belt of the Philippines. In the 70's, one of the Filipino researchers, went and had a chat with the locals and got them to stop fishing in a particular area of their island.
Now the Philippines is quite an interesting area in that they have had overfishing for a long, long time. But they also have these fantastic ways of fishing that involve dynamite and blowing up things. They have also unfortunately figured out cyanide as well, which is a fantastic way of destroying fish communities but also a fantastic way of getting a bite to eat that night.
So what was happening was that a lot of these destructive techniques were being used around the Philippines and Apo Island was a major one. So in the 70's, this Filipino researcher came in and asked them to stop fishing in a particular area. Apo Island - really that’s only about a 4-500 metre distance. So it's not a huge amount of area that they were asked to not fish. It took about 10 years but they went from absolutely decimated coral reef, through to an ecotourism that brings in hundreds of thousands of dollars every year.
So it really is the success story for small traditional areas. However these kind of ideas of stopping people from getting to the resource, for a lot of places in the tropics, aren't really the most - aren't really the best way of conserving resources.
For a lot of these places, if they can't get to the reef, then they can't feed their families. So there's a lot more - a lot of other ways people can conserve resources. These are actually just a couple of pictures. This is a Papua New Guinea guy on the right, and a market in Madagascar. So in a lot of these places, if people can't get to the resource, then their family will pretty much starve.
So what a lot of these places do is have a restriction on gear. So instead of saying to people, you cannot fish there full stop - like the western idea of a non-take area - what they do is say, well you can't use spear guns. Or you can't use a particular size of net, or you can only fish it at a particular time.
So in other words, what they’re really doing is fisheries management. You can imagine that it's more like a bank account so they’ll have a celebration and they'll say, okay in a year's time we will open this area to fishing. We'll use that area for a week and then we'll close it again for another year - and in a range of places.
So a lot of the work we've been doing throughout the Pacific, throughout East Africa, there is a lot of these kind of gear restrictions that are occurring. A lot of things - a lot of these places are really focused on spear fishing. Spear fishing is a very easy and very cheap way of getting the food that you want. A lot of these places - the spear gun that we’re used to - the western style spear gun that’s large and very expensive - is not what you find in a lot of these places.
Really what you find are a piece of wire and a bit of rubber from a tyre. People will go out and will spear quite well. This was a group of kids in Papua New Guinea that - where we were diving and doing some work. They absolutely love getting their photo taken in Papua New Guinea, any excuse to get in front of the camera. This guy on the right was particularly enthusiastic, amazing how much he could hold his breath. But he was very - very excited about having his photo taken.
Interestingly, one of the things that we found when we were working in this Papua New Guinea village was that they had the idea of closing their areas when they found that the fish were too scared to be shot at.
So in other words, they would make the decision on when to close the area when they said the fish were too scared. They would run away too far. So this is what the fish were doing. They were saying, no way. You’ve scared us so often we’re not going to come close to you. So really, what we wanted to do was use this idea and really examine whether this kind of scaredness or this behavioural response in the fishes were actually due to human behaviour.
So what we wanted to do was we wanted to basically look at the distance we could get to a fish inside a marine protected area versus outside a marine protected area, in these places.
What we call it is flight initiation distance. I've also got a very exciting movie. No, it's actually quite a boring movie but it shows what I mean and hopefully - so all we do is swim towards the fish and as soon as it moves, we can measure the distance that we get to a fish.
Now this is really interesting in that, if you go out and look around Sydney - we do a lot of our work at Shelly Beach over in Manly. It's amazing how close you can actually get to a fish in those areas. You go to other places where there's quite a bit of spear fishing and it's - the distance that you can actually get to a fish is much higher. So we’re in this little place called Karkar Island. In Karkar Island, they’ve had two - they've had one protected area and they've also got - we also went to a place close to it that was a none protected area.
This had been protected for about three years. This was the kind of thing where they would protect it for three years and then they would fish it for a couple of weeks, then protect it again.
Just to show that they were using a range of techniques in these villages. But the spear gun - the spear gun was the main kind of gear that they were using. So it was the most important for getting food.
So what we found - I've just got a few graphs of the main results of our work and all this is the flight response. In other words, how close we could get to a fish in centimetres, and the dotted line is the distance that an actual gun would work. In other words, how close do you actually have to be to be able to shoot a fish? That was just over three metres. So anything that was further away than three meters, it was likely that you weren't going to get your fish.
So outside of these protected areas, the majority of species we looked at, really you couldn’t get anywhere close to them. Except for this one species, Ctenochaetus striatus and that’s a fish probably about that size, so not a lot to put on your plate.
So the majority of the fishes we were looking at outside of this marine protected area - and this protected area had only been there three years so it wasn't - it hadn’t been there for decades. So the majority we couldn’t get to. Now inside this protected area - all of a sudden, we could get close to pretty much all of the fish. So really the majority of species inside this reserve were much more what would they call tame, or less scared.
So you could actually go up to them and potentially shoot them if you wanted to annoy all the villagers. In fact one of the things that - what happened is one of my colleagues that was there a year before. They'd been doing work and hadn’t really talked to the villagers a lot. They'd come in to some work. One day they were walking through the forest and a couple of young boys came up to them and said you're going to have to leave because the villagers are coming to kill you. They think what you're doing is trying to find diamonds and oil on their reefs. It took quite a bit of negotiation and a pig on a spit to get them through that one.
So there was a lot of respect after we had found the results. We are showing that a lot of these, what we call co-management ideas. So your restrictions on fishing and the ability of the villagers to understand the behaviour of the fish were shown in our research. We went in there going on, well we’re actually going to show it because we know these guys know what they're talking about.
Interestingly - and this is just my last slide and I'll let Liz talk about her interesting stuff after this. The four - I'll just go back. The four species I've got circled there are four species of Parrotfish. Now Parrotfish are one of the most important species on a coral reef - (1) is that they get rid of a lot of algae so they will feed on the algae. But (2) they actually - that kind of eating of the algae, allows areas to - for coral recruits to come in.
One of the main problems within the Pacifics is that people are spear fishing and they're spear fishing at night. They are killing a lot of the Parrotfish. What's happening is that in a lot of these places where you get rid of those Parrotfish, you get this very quick shift in the benthic communities from a coral dominated system to an algal dominated system. It kind of affects the whole - the makeup of the reef. So these areas where people weren't fishing, where they'd managed their gear and where they were actively looking after their reef, we were finding all of these species were out of spear fishing distance, outside.
But inside the reef, they were close to it. Then when we looked at the actual - this isn't the abundance. But when we looked at the actual abundance within the marine protected areas, they were orders of magnitude higher. So really being able to go into these areas and show that their idea of co-management that was not shutting up an area to fishing but actually working with the animals - working with the reef - was vital in keeping their resources sustainable. I'll leave it at that. Thank you very much.
Dr Elizabeth Madin:Okay. So from what we've heard so far, there's been a bit about all kinds of threats that humans impose upon fishes. I'm going to talk also some more about overfishing but from a different angle.
So what I'm going to talk about is that, unlike what Dave was just saying, in a different way, human fishing creates fearless fish by killing their predators. So what Dave was saying is that when fishing targets a particular species, that species tends to become more fearful. So for example, if you’ve got a little coral head here and a little prey fish that’s going out to eat some food, some algae, it's less likely to want to go far from that - it's more like - sorry, we'll [unclear].
But it's more - it wants to get away from the things that are going to kill it, right? But what I'm going to talk about is when people kill the predators of potential small fish like that, the fish want to stay close to some sort of shelter. So like I said, a coral here, a little fish going out to eat. Bit more scared. When the predators are there, they're scared. When the predators are gone because of fishing, they're a little bit bolder, that's what we thought. So what we did is we went out to see, does this create fearless fish?
So some colleagues and I over the last few years have gone and worked in a set of islands - the [Lion Islands] which are, as you can see here, pretty much in the middle of nowhere.
That’s Hawaii there, that’s California, there's little New Zealand and there's Australia. So they’re right out in the middle of nowhere and because of being so far away, historically none of these islands have been fished. That’s still the case for the top island here [Palmyra], which is - for the last number of years has been protected as a complete no take marine protected area.
But the islands to the south - so [Tabuaeran] and Christmas which are part of the Republic of [Kirabas], have experienced increasing human populations because over the last say 30 to 40 years, the main islands of Kirabas which are about 2000 miles to the west, have become extremely over populated and they don't have many resources on land. Now they don't have many resources in the water because they’ve been overfished. So the government came up with this idea to send some - to basically give people land if they wanted to move out to these remote uninhabited islands.
So you can imagine, a lot of people put up their hands and went out there. So what's been happening though is because of that, these islands, as you can see, there is very little land. This is just a little ring of land, they're little atolls. This is a big salty lagoon. There is not a lot on land. So they basically, as Dave was saying, rely - like many island communities - on the resources from the ocean.
So when you go to these places, this is what you'll see in the water. Palmyra, lots of big hungry predators. What you'll see there is the few hungry predators that were there, are now on the dinner table. This is actually a local - in fact, he is the police chief of one of the islands. This is his collection of shark fins, which once a year a boat comes around and collects them and pays him some money. So you can imagine where all the sharks go, right?
Anyway, so what we saw is that - oh everything's gone crazy - basically what you see is that the predator - I mean, the human population density here in grey, it increases - or sorry, decreases as you go this way. The opposite pattern happens for predator biomass. A piscivore is just a predator, a fish eating predator.
So it's pretty clear that what's happening is that the more people fish, the fewer predators there are. Well that’s not rocket science. But what we wanted to do was see what are the effects of this predator loss on the fish that they would otherwise eat?
So we looked at four different species. The Bicolor chromis, which is a little, bitty damsel fish about this big. The Blackbar Damsel, also a small damsel fish. The Whitecheek surgeonfish and the Bullethead parrotfish. Now the last three of these are primarily herbivorous so they mostly eat seaweed. The first one eats plankton.
So one way to measure how scared or how bold a fish is, is by what we call excursions. Basically excursions are just looking at how far a fish moves over the reef during a certain period. So in our case, it was five minute observations. What we did is we thought right, we'll go out and measure over these different islands how far these things are moving. What we found was pretty striking.
Is that - so the little red sites here correspond to Palmyra, which is the very predator rich, unfished site. The blue and the green points, represent Tabuaeran and Christmas Islands, which have been heavily fished. So on the Y axis here, you have excursion size which is basically a measure of boldness. On the X axis, you have predation risk - and some word has disappeared there - but predation risk where the more - the higher it is, the more risky it is for these little fish.
So what we saw is that at the high risk, high predator, no fishing site. These little fish were very scared. They weren't going very far. Generally they were all staying, even the ones at the fairly low predator sites at the island, were staying very close to their home.
Whereas at the other two islands, they were moving all over the place. Some moved farther than others. But what it indicates is that they can be bold if they want to, and they are being bold.
So then we looked at the other - another few species, as I said. We saw basically the same pattern for each of these. They are very different in their behavioural styles, and just their functional groups. We thought, well what does this tell us? It says that at predator rich sites - sorry, at fished, low predator sites that these fish can basically swim wherever they like. At unfished, predator rich sites, fish tend to restrict their movement, which as you can imagine has consequences for the fish in terms of the food or the baits that they can acquire.
So basically we concluded that the more humans fish for predators, the bolder their little prey get.
So okay, we know that there are some ways humans are creating basically fearless fish. The next question was, what does that mean for their food resources? You might think, well why do you care really where seaweeds going to grow?
But as Dave said, seaweed's important because it competes with corals for space on the reef and corals, as you probably all know, are the building blocks of reefs. So we're not going to talk about that part because we haven’t done that work yet. But what we are going to talk about is what happens to the seaweed distribution? How are these behavioural changes that humans are indirectly causing - how is that then also indirectly causing changes in the seaweed distribution?
So this is just to illustrate the point really that, if given the choice - over here this is a big open area where predators could lurk. This is a safe haven so to speak where little fish - well, these are medium to big fish but they can hide from predators. That the predators - they are much safer around these coral heads.
So again here's our little pretend coral head here. We developed - my colleagues and I developed a model to show us what would be predicted given these behavioural changes. So what we did is we just created a very simple diffusion model in which a little fish in a one-dimensional reef landscape is treated as a particle, and it just diffuses outward from this coral head because this is how fish behave. Some of these fish in real life, they go out from a coral to get food and they come back when they are scared by a predator.
So in the model then, we put a number of predators in some - lots of predators in some sites and not very many in others, and we looked at what happened. What we found of course is that there is a distribution of basically time that they are spending around this corral head, suggesting that they're eating more closer to the coral and less further away.
So then if you plop these down on a pretend one-dimensional landscape, you get these little safe zones around the corals. That's supposed to be risky in the middle because that's where the fish would have a hard time getting back to their shelter, if a predator were to come by.
Then what you see - what the model predicts is that around the coral heads, you get very little, if any, seaweed. Whereas in the risky areas in between, you get an abundance of seaweed growing up because there is nothing really going there to eat it.
So the prediction as I say is less seaweed surrounding the reefs and adjacent areas. So what we did then - well what we could do, is take these model predictions and put it on a two-dimensional landscape that looks more like what you'd see in the real world. What it shows is that you get these little circles surrounding coral heads or patch reefs. This can work in a variety of scales, where it's safe and in between you get these risky areas where seaweed can potentially grow.
So then - the model basically predicts, and we would predict as well, that if you have less fishing and more predators, you're going to have smaller safe zones. Whereas if you take out all the predators and there is more fishing, you get these zones that are basically expanding and sometimes, potentially overlapping to the point where you get no areas. You don't even see the pattern anymore because all the circles have overlapped.
So you might be thinking, what is this funny picture? Well, this is exactly what we predicted. We looked at it from satellite images and sure enough what we see here are - in the middle here we've got little reefs - these are patch reefs right here. These are seaweed areas and these are what we call grazing halos.
Now grazing halos are not a new phenomenon, they've been known for years. But what's interesting now, and this is something that we’re working on right now, is can we observe these things from space? Because what we're seeing is that by changing the way fish are behaving through our fishing - indirectly changing little fish behaviour - we're getting these footprints on the landscape of reefs that can actually be seen from space. Just to show you what I mean, this is taken from Google Earth. So anyone can do this, it's freely available.
As we zoom in to Heron Island on the southern Great Barrier Reef here, what we can see is that in shallow coral reefs where the water is very clear, we can see these things from space basically, which is pretty neat. So you don't even have to get in the water maybe, just to look at what's happening to predator populations and fish behaviours.
So here we've got patch reefs here, all these little brown areas and it's very hard - it’s a little hard to see but the green areas here and here and here, that’s all seaweed. These are what we call the grazing halos. So last year, we went out and look and swam around and tried to figure out, is what we’re seeing from these satellite images, is that really what's going on? Sure enough, that’s exactly it.
We even did some tests, which I'm not going to bore you with the details but to show you that - to show people that in fact yes, these little fish are scared, for example in this marine protected area, to go too far from the reef. That’s what's creating these patterns.
So generally why this is kind of interesting I think, is that in the world as I said, these reefs for example are just a really good example of very, very isolated reefs. In particular they are part of a country - well at least the southern two are - where the resources are fairly limited for monitoring the health of coral reefs. But most of the world's coral reefs occur in developing nations where they are quite limited, resource wise.
So what we're hoping is that this may be something that we can use as a remote tool for resource tool for resource management and conservation. So hopefully, down the line you might be able to go to a place like Indonesia or - the government say of Indonesia who's charged with monitoring these reefs, might be able to use this as a technique to say, okay well at a place like this where it's very, very heavily populated. I don't know if you can tell but these are little roofs. So this is a coral island that’s been completely populated. You can imagine there's a lot of fishing pressure there. I would assume you would not see grazing halos there because all the predators have probably been taken out.
So - but what we're hoping is this might serve as a way for places like that to be able to monitor changes in fish behaviour and predator populations, by looking at these footprints over the landscape.
It may have other potential applications, this technique of - even things like wildlife monitoring on land, where predators have been introduced. Say wolves in North America, cheetahs in India have been reintroduced recently. You might assume that they would change the behaviour of their prey, which is what people have actually seen. So we're hoping that maybe this - depending on how it goes, this might be something where you could actually monitor those kinds of patterns from space.
Again, the same with meat and livestock grazing patterns which, in a country like Australia, is no small undertaking on such big scales. So this may allow things - monitoring for these kinds of things to be done less - for less money and over bigger scales. So with that I just want to say thanks very much for listening, and I'm sure we'd be happy to take any questions.
22 September 2011 50:00
Tags: environmental science, marine ecology, fish behaviour, anthropogenic impacts
How human interactions are changing the way fishes function
While fishing, pollution and other activities are commonly known to directly affect fish numbers in the ocean, only recently have scientists begun to discover more subtle effects humans are having on the way fishes behave.
New studies of fishing pressure on large, predatory fishes within Pacific coral reefs have exposed that fishing can affect how far fishes are willing to venture from their safe havens, which can in turn affect patterns of seaweed growth on coral reefs.
Dr Elizabeth Madin, Dr David Feary and Professor David Booth examine the developing science on the importance of fish behaviour and human influences in structuring fish assemblages, and reveal the role of humans in driving changes in the structure and function of fish communities globally.
About the speakers
Dr Elizabeth Madin is a US National Science Foundation Postdoctoral Fellow and marine ecologist. Her research interests include behavioural and community ecology, effects of fisheries on marine communities, and marine conservation. Her current research focuses on understanding latitudinal variation in the effects of fisheries on coastal marine systems, as well as how fishing indirectly affects the behaviour of marine organisms.
Dr David Feary is a UTS Chancellors Postdoctoral Fellow whose main research interests lie in understanding the role of anthropogenic and natural disturbances in structuring reef fish communities. David’s current research is focused on investigating the importance of the East Australian Current in determining the structure and diversity of tropical fishes within NSW coastal waters.
Professor David Booth is a marine ecologist whose research has concentrated on the life history of tropical and temperate marine fishes in the light of climate change, particularly on understanding the critical mechanisms important in the establishment of reef fishes.
UTS Science in Focus is a free public lecture series showcasing the latest research from prominent UTS scientists and researchers.
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