While land farmers have used seasonal forecasting for nearly a decade, marine farmers in south-east Australia have sought the technology for a region identified as a climate change hotspot, with rates of ocean warming up to four times the global average.
The project, funded by CSIRO and the Fisheries Research and Development Corporation, is a response to requests by Tasmania's four major salmon companies for short-term ocean forecasts for their farm sites.
In this podcast, CSIRO Climate Adaptation Flagship scientist Dr Alistair Hobday explains the projected impact of climate change on aquaculture and how accurate seasonal forecasts are helping farms adapting to rising ocean temperatures.
Interviewer: G’day, and welcome to CSIROPod. I’m Glen Paul. Many of Australia’s economically important industries, such as Agriculture and Tourism, depend on long-term meteorological forecasting, otherwise known as seasonal forecasting.
Land farmers and other weather sensitive industries have used seasonal forecasting for nearly a decade, and now marine farmers operating in the climate change hot spots of Southeast Australia are seeking the technology.
In a joint effort with the Fisheries Research and Development Corporation, CSIRO Scientists are trialling the first near shore water temperature forecast to assist Australia’s Agricultural Farm Managers contend with rising oceans temperatures.
CSIRO Climate Adaptation Flagship Scientist, Dr Alistair Hobday, is working on the project, and joins me on the line. Now, Alistair is this more a precautionary measure by Fisheries against climate change, or are warming waters already making an impact in the region?
Dr Hobday: Yeah, we’ve had some summers in recent years where the temperatures have increased to such a level that the salmon have been challenged by those warmer temperatures. They go off their feed, they suffer a little bit more disease outbreak, and also the farms tend to get more growth on the outside of the cages, which requires more cleaning.
Interviewer: Right. So then how do you undertake a near shore seasonal forecast for ocean temperatures?
Dr Hobday: Oh, salmon farmers have relied on atmospheric forecasts, just like land farmers, but by us providing information on what’s happening in the ocean we think these forecasts are going to be much more relevant to their businesses.
The salmon farmers themselves have been recording local temperatures at their own farms for a number of years, and have used those to compare whether today was warmer than the same time last year. However we’re now able to use their own temperature records and statistically project those up to three or four months ahead of time to indicate whether or not the coming months are going to be warmer than average.
Interviewer: OK. Now, of course I understand it’s a trial, but just how accurate do we expect the forecast to be?
Dr Hobday: We began delivering forecasts in October of 2010, and we projected up to four months ahead at that time. We’ve just reached that four month projection time if you like, so now we’re able to compare what’s really being observed with what we projected four months ago.
We’re finding that for the four locations we’ve trialled around Tasmania we do particularly well for sites that are more exposed to open ocean conditions, and we expect our accuracy there is somewhere close to 98 per cent. That is, the temperature that we project is within two per cent of the final value that is observed four months later.
For another site, for example Macquarie Harbour on the West Coast, that’s exposed to a lot more freshwater influences. And so rainfall becomes increasingly important, and we’re having less success at that particular site. So in the coming year we’ll really try and work out, well what other information do we need to improve those forecasts for that region, which is responsible for about five to ten percent of salmon production?
Interviewer: Hmm, OK. Well, obviously there, there’s a variety of changes that can be brought on and can impact on the salmon through the change in water temperature. But is it only if it heats up? What if it goes the other way?
Dr Hobday: Projections of temperature that show that the coming months are going to be colder than usual are also of interest to the farmers. In particular fish can go off their feed when the water gets too cold, and so the farm might decide to give them a higher protein diet for example, or put in more fat to make the fish able to handle those cooler temperatures.
Other things that happen when the temperatures are too warm, is you can get outbreaks of jellyfish, the waters can stratify and oxygen content can go down. And all of those things, as well temperature, stress the fish.
Interviewer: Right. So what then happens once the marine farmer gets the forecast and it says well, waters are going to increase in temperature? What can they do? I mean obviously they can’t go around pouring bags of ice into the water to cool things down. What’s the plan?
Dr Hobday: The salmon farmers have a range of options if they’ve got information that the coming season is going to be warmer than usual and that can include changing the location where they’re putting the pens. They have variation in their local site where they house these salmon, and they can choose a particular area they know to be a little bit cooler. They can also reduce the stocking density of their animals, so that there’s less demand for oxygen. And as you know, warm water carries less oxygen than cold water. So by reducing the number of fish in a cage you can reduce the stress on the fish.
They can begin to think about how much disease treatment they might choose to do in the upcoming months, and also how much labour might be required in order to service the cages. In warmer water the cages receive more fouling organisms settling on them, and so to maintain water flow you have to increase the frequency with which cages are cleaned. And so farmers can work out how much labour they might need in those coming months.
Interviewer: Hmm. And valued at A$380 million annually, salmon production is Australia’s major seafood industry, and I know we’re talking short-term forecasts here, but how will that value be maintained into the future under climate change?
Dr Hobday: Yes, salmon’s a very valuable industry in Tasmania, and supplies over 90 per cent of the Australian salmon market, so it’s a very valuable industry that’s not going away. So us providing these seasonal forecasts help make these businesses more profitable in the short-term, and that will really equip them for handling longer term changes in climate that we’re expecting over the next 20 to 50 years.
Interviewer: Right. And what are these longer term changes that you expect to see?
Dr Hobday: In South-east Australia waters will continue to warm, and that’s going to mean that there are more months in the year where salmon are going to be challenged. However the industry’s got a range of options. You know, the ocean is not warming uniformly, and so we can help them select sites that are going to be cooler, and there are also technical things that you can do. For example cages can be moored below the surface where the water is a little bit cooler; you can do mechanical mixing of the water which can also cool it down; and there is also breeding attempts underway that can help to produce salmon that will cope with warm waters more easily.
Interviewer: OK. So just as aside to that then, what happens to the person who makes their income out on the open ocean in a trawler, in a big commercial fishing venture? Climate change will impact on the fish there, but obviously they can’t enhance the fish to deal with it. So what can they expect under climate change into the future?
Dr Hobday: In the open ocean we’re seeing responses to warming temperatures that include changes in fish distribution. So, for example, species that are tropical in origin are being found further south along the Australian coastline. For fish that are already found in southern regions, we’re seeing their range is being compressed even further south.
That means that wild fisheries catches for many species is not likely to increase in future, and that means that Agriculture has got to continue to play a large role in providing seafood for Australia.
Interviewer: Hmm, that’s actually an interesting point. I hadn’t really thought of it along those lines. So with that in mind, what more needs to be done by industry and Government to address what’s happening in our oceans under climate change?
Dr Hobday: Yeah, rather than Scientists just putting out information and hoping that the industry would be willing and able to use that information, I think there’s got to be a greater interaction between the industry and the Scientists in order to produce research that’s immediately useful to the industry.
Interviewer: Possibly easier said than done, but certainly a great strategy Alistair, and a very important project. Thank you for talking to us about it today.
Dr Hobday: Great. Thank you very much, Glen.
Interviewer: Dr Alistair Hobday from CSIRO Climate Adaptation Flagship. For more information go to www.csiro.au.