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Published: 26 September 2011

Is Tilapia the new cane toad?

Matt Bradford

Northern Australian waterways are facing a new environmental threat. Tilapia mariae, a highly invasive fish that can tolerate and adapt to a range of environmental conditions, is rapidly expanding its range.

A typical late-juvenile <i>Tilapia mariae</i> showing 6–7 stripes; adult specimens have 2–6 dark spots. Originally from Africa, the species thrives in disturbed waterways.
A typical late-juvenile Tilapia mariae showing 6–7 stripes; adult specimens have 2–6 dark spots. Originally from Africa, the species thrives in disturbed waterways.
Credit: Noel Burkead

Australia has a history of highly invasive plant and animal species that cause massive environmental damage and cost millions of dollars to control or eradicate. Just think of the rabbit, cane toad, prickly pear or lantana.

Exotic and invasive fish are less in the spotlight, although the carp (Cyprinus carpio) is now a much despised species in more southern areas of Australia after first being imported around 1900

However, a group of mainly freshwater fish from Africa, the tilapiines, are emerging as new threats to Australia’s river systems.

In a recent study published in the journal Marine and Freshwater Research,1 I teamed with North Queensland-based staff from CSIRO and the Department of Employment Economic Development and Innovation (DEEDI) to document the introduction and biology of one tilapiine species, Tilapia mariae.

T. mariae is a freshwater and estuarine species that grows to a length of approximately 300 mm in its native range in coastal western Africa. Due to its hardiness and high fecundity, it is a sought-after aquarium species around the world.

However, these features also make T. mariae a perfect invasive species. It can tolerate a wide range of temperatures, salinity and oxygen concentrations. Importantly, it can adapt its diet and reproductive strategies according to environmental conditions, increasing its ability to spread rapidly. Unlike many Australian native species, it thrives in highly disturbed and poorly vegetated watercourses.

Watercourses in their natural state allow native species to compete better with invasive species.
Watercourses in their natural state allow native species to compete better with invasive species.
Credit: Matt Bradford CSIRO

The species was first recorded near Cairns in the early 1980s and has since been a commonly occurring inhabitant of eastern-flowing rivers within 100 km of that first record. More recently, a population has been discovered in a tributary of the western-flowing Mitchell River, which runs into the Gulf of Carpentaria. This is of great concern to biologists and land managers, as the species has the potential to spread over much of northern Australia via overland water flow and movement through saltwater reaches.

In the United States, T. mariae is already a huge environmental concern. In Florida, the species contributes to more than 50 per cent of fish catches. A density of more than one breeding pair per metre has been recorded along disturbed canal edges. Densities of this magnitude cause disruption of breeding and localised extinction of native species.

The species’ impacts are poorly documented in Australia due its comparatively recent introduction. However, we know that its reproductive strategies, diet and habitat overlap with many of our freshwater species, including freshwater catfish, gar and bream.

We hope that the information in our recent paper will stimulate further research into the species that will eventually lead to effective control or eradication measures. At the moment, control is limited to education and awareness, and spot eradication using chemicals and electro-fishing.

Localised tilapia populations have recently been successfully eradicated using the chemical rotenone in small areas of northern Queensland, but this approach is not an option for entire catchments.

Management strategies focusing on controlling the characteristics that give T. mariae a competitive advantage may provide the best chance to reduce its abundance and distribution. These may include the species’ variety of diet and substrate for egg deposition, as well as reducing extremes in water temperature, salinity and oxygen

One way of controlling the T. mariae invasion is by maintaining and rehabilitating the integrity and resilience of native aquatic ecosystems.

Matt Bradford is a research projects officer at CSIRO Sustainable Ecosystems’ Tropical Forest Research Centre in Atherton, Queensland.


1 M Bradford, F. Kroon and J. Russell (2011) The biology and management of Tilapia mariae (Pisces : Cichlidae) as a native and invasive species: a review. Marine and Freshwater Research 62 (8) 902-917





Published: 26 September 2011

Renewable energy sector to benefit from wind-speed research

Craig Macaulay

While some recent international studies have shown a decrease in wind speeds in several parts of the globe, including Australia, more recent results from CSIRO show that Australia’s average wind speed is actually increasing.

The ability to accurately quantify long-term variations in wind speeds is essential to the viability of Australia’s wind power sector.
The ability to accurately quantify long-term variations in wind speeds is essential to the viability of Australia’s wind power sector.
Credit: Gregory Heath

CSIRO scientists have analysed wind speed observations to understand the causes of variations in near-ground-level wind and explore long-term wind speed trends.

Accurate estimates of long-term trends provide a useful indicator for circulation changes in the atmosphere and are invaluable for the planning and financing of sectors such as wind energy, which need to map risk management under a changing climate.

‘We have a good picture of wind energy availability across Australia from previous CSIRO wind mapping and, with the growth of wind farms, there is an emerging need to understand how climate change can affect the wind resource,’ says Dr Alberto Troccoli, lead author of a recent paper published in Journal of Climate. 1

‘Wind power production is expected to increase greatly over the coming years and the associated electricity system will be subject to variations of several hundred megawatts – depending on wind availability.

‘The ability to quantify with accuracy these long-term variations is essential to the sector from an economic point of view.’

Dr Troccoli said that, averaged across Australia over 1989–2006, wind speeds measured at a height of 10 metres had increased by 0.69 per cent per annum, compared to a decline of 0.36 per cent per annum for wind speeds measured at 2m height.

‘The potential for increasing the efficiency of energy operations by using quality weather and climate information is therefore apparent and one of the first steps is the standardisation of wind recording stations.

‘Wind observations, like other meteorological variables, are sensitive to the conditions in which they are observed – for example, where the instrumentation sits relative to topographical features, vegetation and urban developments.’

The team found that the wind speed trends over Australia are sensitive to the height of the station, with winds measured at 10m displaying an opposite and positive trend to those reported by a previous study, which analysed only winds measured at 2m.

Light winds measured at 10m, a height that represents better the free atmospheric flow, tend to increase more rapidly than the average, whereas strong winds increase less rapidly than the average winds. Light and strong wind measured at a height of 2m tend to vary in line with the average winds.

‘Our work shows a number of challenges with the consistency of the observations during their period of operation and between sites across Australia,’ adds Dr Troccoli.

‘The quality of future wind observational datasets will depend on having consistency between sites, particularly with respect to measurement procedure, maintenance of instrumentation, and detailed records of the site history.’

He said the work has implications for a variety of sectors beyond wind energy including building construction, coastal erosion, and evaporation rates.

The conjunction of energy and meteorology is the central theme of the International Conference Energy & Meteorology on the Gold Coast in November.

Read Dr Troccoli’s thoughts on What’s the energy forecast? Bringing meteorology and generation together in the online forum, The Conversation.


1 A. Troccoli, K. Muller, P. Coppin, R. Davy, C. Russell and A. Hirsch (2011) Long-term wind speed trends over Australia. Journal of Climate, doi: 10.1175/2011JCLI4198.1




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