Seas getting too warm for morwong
Over the past 60 years, surface water temperatures in the Tasman Sea have risen by nearly 2°C as a result of general ocean warming, as well as local effects caused by
the southward extension of the East Australian Current. Like other cold-blooded animals, fish typically respond to increasing water temperatures by increasing growth rates, but as temperatures rise beyond physiological limits, they can cause stress and, eventually, death.
A team led by Anna Neuheimer of the CSIRO, the Australian government’s science organisation, looked at the effect that rising temperatures in the Tasman Sea are having on the banded morwong, a long-lived inshore species. By measuring the distances between growth rings in bony structures known as otoliths – which the fish use for orientation and the detection of movement – the team was able to determine annual growth rates. These were then compared to temperature trends across the species’ distribution.
The results showed that in areas where temperatures have risen, but are still relatively cool, growth rates have increased significantly since 1910. But at the warmer northern edge of the species’ range in New Zealand waters, growth has slowed.
‘Preliminary field and laboratory studies suggested that this decline in growth may be related to temperature-induced physiological stress, resulting in increased oxygen consumption and reduced ability to sustain swimming activity,’ said one of the study’s authors, Jeremy Lyle of the University of Tasmania.
July 2011
the southward extension of the East Australian Current. Like other cold-blooded animals, fish typically respond to increasing water temperatures by increasing growth rates, but as temperatures rise beyond physiological limits, they can cause stress and, eventually, death.
A team led by Anna Neuheimer of the CSIRO, the Australian government’s science organisation, looked at the effect that rising temperatures in the Tasman Sea are having on the banded morwong, a long-lived inshore species. By measuring the distances between growth rings in bony structures known as otoliths – which the fish use for orientation and the detection of movement – the team was able to determine annual growth rates. These were then compared to temperature trends across the species’ distribution.
The results showed that in areas where temperatures have risen, but are still relatively cool, growth rates have increased significantly since 1910. But at the warmer northern edge of the species’ range in New Zealand waters, growth has slowed.
‘Preliminary field and laboratory studies suggested that this decline in growth may be related to temperature-induced physiological stress, resulting in increased oxygen consumption and reduced ability to sustain swimming activity,’ said one of the study’s authors, Jeremy Lyle of the University of Tasmania.
July 2011
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