transcript
- Matt Smith
I'm Matt Smith, and welcome to a La Trobe University podcast. In Australia we take our wildlife pretty seriously and there’s one little fish that has a big problem, and that’s the Murray-Darling Hardyhead. Now this fish is only surviving by being bred in captive populations, so I talked to Iain Ellis, from the Murray-Darling Freshwater Research Centre at the Mildura Campus of La Trobe University, to see how the fish is going.
- Iain Ellis
What we’ve got here is a series of aquaria, which are housing Murray Hardyhead, one of the most threatened fish in the Murray-Darling Basin. They now survive in just about eight wetlands in Victoria and South Australia and that’s about it. So during the drought we rescued fish from a number of these locations, put them in fish tanks here in the lab where we induce them to breed and raise their young for later release back into the wild.
- Matt Smith
How many fish do you have here? They’re about 25mm long. Is that about the average size?
- Iain Ellis
Yeah, an adult fish gets between 40 and 80 mil. At the moment we’ve got about a thousand fish from just a couple of populations, but six months ago we had fish from eight different populations in the Basin, in the Murray-Darling Basin, and we had up to 3,000 fish, including adults and larvae at any one time.
- Matt Smith
Why are these fish important to the environment then?
- Iain Ellis
Murray Hardyhead are a fairly specialised fish in the Murray River system, because they have a preference for salty or saline water bodies, which that type of wetland used to exist all the way along the Murray Valley on the fringes of the valley, where water would evaporate and become ... the wetland would become salty and in the next flood these guys would re-disperse. So they pretty much dominate those salty wetlands, and the fact that we don’t have those habitats any more, indicated by the threatened nature of this species, suggests that there’s something fundamentally wrong with the health of the system. So they’re an indicator species, a bit like a canary in a coal mine, but in addition to that, in those habitats where they are the dominant small-bodied fish, they’re an important food source to a lot of bird species and any larger fish that are there. So some of the migratory birds that may themselves be rare, probably depend on these guys as a food source in those sorts of off-channel habitats.
- Matt Smith
As I understand it, some of the fish that you have here are from water systems that no longer exist. Is that right?
- Iain Ellis
That’s true. The systems exist, but they dried out during the drought, particularly some of the South Australian sites and a couple of Victorian sites. We’re hoping to release these fish back to those locations when the conditions are suitable, but that would depend on a co-operation between us and a whole bunch of other stakeholders, to get the legal permission to do that.
- Matt Smith
What’s the point of preserving a fish like this, that’s just going to die out anyway. Are they breeding in the wild? Are they going to be self-sustainable?
- Iain Ellis
Yes, they are self-sustainable in locations where their suitable habitats still exist, the problem being that those habitats are becoming fewer and fewer because of the regulation of the river system by us, for irrigation purposes. Those isolated wetlands no longer join to each other in a flood event. Although you could argue that individually the species is not particularly important, it is a very important part of the food web in those isolated systems, and as I said before, it’s an indicator that there’s fundamental issues with the health of our river and wetland system.
- Matt Smith
So, we’ve got an amazing amount of background noise here, with pumps and filters and everything going. Just before I came in, you had that unit on. Could you turn it on just so get a sense of what is this here. It’s a heater did you say?
- Iain Ellis
It’s a temperature control system, the idea being that we can maintain a temperature in this room which is ideal for breeding of this species. They tend to start breeding at above 24° in the wild, so we can raise the temperature in here to sort of 28 to 30° and induce spawning of these fish early in spring or late in winter, which is earlier than they would normally do in the wild. So we can extend their breeding season for an extra month or two each year to increase the production of eggs in the lab.
- Matt Smith
OK.
- Iain Ellis
Do you want me to switch it on?
- Matt Smith
Yeah. Flick it on. It sounds like the room’s going to take off any second. So that’s on. Leave it on. We’ll step outside. Just close this here? So that’s one species of fish that you’re working on here. What other sort of work are you doing up here in Mildura?
- Iain Ellis
As a fish ecologist, I do a lot of what we call base line fishery surveys in the region. Surveys of fish communities in river reaches and the Murray River or its associated creeks, or billabongs and wetlands in the Murray and Darling River systems in the region. Generally these are to determine which species exist in which wetland, or which river and which creek, and over time if we repeat these surveys, we can monitor whether a population of a certain species is increasing or decreasing, or how those fish communities respond to either managed intervention, so environmental watering projects or installation of regulators or weirs, or alternatively, things like the recent flooding that we had, we can determine whether native species respond positively to that. We can also keep a handle on pest fish like carp and mosquito fish. So in Kings Billabong, which is a local wetland in Mildura, we’ve been monitoring the fish community now for three or four years. That’s a billabong that’s going to, in the next few years, receive some attention in terms of management. It will have a regulator installed to allow local resource managers to lower the wetland water level by up to a metre each year. And the implications of that may be significant for the billabong as it holds a fairly important population of freshwater catfish, which are another listed threatened species in Victoria, so we’ll be monitoring the impact of that managed intervention on the catfish but also on the other species and including the pest species that already exist in that billabong.
- Matt Smith
The Hardyhead is essentially on life support almost. Is that something that you find is common throughout this particular local fish species
- Iain Ellis
Not yet. Hardyhead are right up near the top of the threatened list for the freshwater fish in this part of the world. There’s two or three other species which are probably equally rare. They’re suffering a similar fate. They tend to be confined to captive systems in other parts of research labs or organisations. But the fact that this many species are threatened sort of suggests that down the track we may see more and more native species will become essentially museum fish on life support, as you suggest. So our work, and other people’s work, is essentially to stop that happening, to try and work out solutions to the reasons why these things are so threatened in the first place, so that we don’t get to this stage. This is the last resort for a fish species.
- Matt Smith
Aren’t the solutions rather large-scale changes that need to happen?
- Iain Ellis
In many cases they are, but we can also reduce our impact through smaller management solutions such as environmental watering of specific locations, where we know threatened species or threatened communities live. We can direct environmental flows to specific river catchments or areas of catchments, for example the Living Murray Initiative is a big program which is returning water to six icon sites. Now an icon site is for example, the Hatter Lakes system, which is a huge area of a number of lakes, so returning water to that system will benefit a whole range of habitats, including the water birds and the trees in that eco-system. So that’s closer to the landscape style of environmental management you’re suggesting. These guys are currently, they’re a reactive type of management strategy, to keep them alive while we work out a better way of returning them to their former glory, essentially.
- Matt Smith
How many have you returned to the wild?
- Iain Ellis
We’ve returned about 700 in Victoria, and about a thousand to South Australian sites. Just last week we released another bunch. And at those locations, the released fish within months had demonstrated some breeding, and some recruitment, which means good news. So they weren’t kept alive here in the lab for nothing. Once we’ve released them they’ve bred, which is exactly what we want them to do. And they’re released to sites that have generally benefited from the recent flooding, so the flood provided a lot more habitat that would formerly be available to these fish.
- Matt Smith
How much are you doing in, say, intervention, where you’ve got introduced species of fish then?
- Iain Ellis
It is definitely an issue. Not so much with the Murray Hardyheads, so some of the saltier wetlands, the bigger problem would be carp, in terms of introduced fish. When it gets to a certain level of saltiness, around about 20,000 EC units, carp tend not to do very well, and the few locations where Murray Hardyheads survive are generally up around that level. So carp aren't as big an issue but mosquito fish pest species can survive that level of salt and they can be quite aggressive towards Murray Hardyhead. So we’re starting to look at methods of manipulating water levels to benefit Hardyhead, that may dis-benefit the mosquito fish and potentially the carp.
Some of the other projects – so the Kings Billabong project I mentioned earlier, we’re monitoring the fish community, looking specifically at the catfish but we’re also keeping a close eye on carp numbers and we’re investigating some methods of tracking individual carp around that wetland when it is managed, and the water level is drawn down, and then when it is re-filled, if we can actually determine where the carp are going to be, when that managed intervention occurs, we may be able to get carp to accumulate in certain areas of the billabong and therefore direct some targeted removal in those areas.
- Matt Smith
Are you tagging carp?
- Iain Ellis
Yeah, we’ll put some acoustic trackers in carp hopefully. This is technology which is being done worldwide, predominantly in marine systems but more and more in freshwater systems. It essentially looks like a tiny microchip you put in your cat or your dog but it can send out an acoustic signal to listening stations which you put at appropriate locations either in your wetland or along a river system, and it will locate your fish as it swims past, so you can actually track fish movement up and down river systems and throughout particular wetlands.
- Matt Smith
So how many are you tracking now?
- Iain Ellis
We’re not yet. This is a project we’re trying to procure some funding.
- Matt Smith
- Iain Ellis
Yeah, it would be a good excuse for fishing. And in particular we’ll learn a bit about the behaviour of carp and catfish in that project if we can get it up and running, but there are similar projects being done, particularly on Murray Cod, and they’ve determined Murray Cod response to increased river flows, where a flow will come down a river system, the cod will start to move upstream or downstream a lot quicker than it did before the flow came along. So we’re definitely learning a lot more about fish behaviour, which is important to know, because then we can better direct where we put environmental water, and when.
It sounds like a good excuse for fishing.
