Range Extension

Australian fish moving south as climate changes The University of Tasmania has found that 35 species face shifts in their ranges and egg-laying patterns as the oceans warm Per redmap.org.au Snapper stocks may climb in Tasmanian waters due to climate change, but decline off the coast of South Australia. International research published in 2013 found that fish species were being pushed towards the poles at a rate of 7kms every year as they chase the climates they can survive in. The global sea surface temperature has increased by around 0.1C per decade since the 1970s. As well as warming waters, marine creatures have to deal with increasing acidification as excess carbon dioxide is absorbed and lowers the pH level of the oceans. The south-east coast of Australia is one of more than a dozen global ocean “hotspots” – others include off Brazil, in the Indian Ocean and the North Sea – where the water is warming much faster than the global average for the world’s oceans. Australian scientists have assessed how 35 common fish species are coping with climate change. The 35 species had a varied response to increasing sea temperatures and changing levels of nutrients and plankton. Species such as abalone, blue swimmer crab, southern calamari, southern rock lobster and western king prawns will experience a high impact from changing temperatures. Australian salmon will face similarly large changes due to altering winds and currents, while black bream will have to cope with changed freshwater flows. Scallops and blue grenadier were also found to be highly sensitive. Researchers stressed that not all of these changes would be disastrous for fish, but that most of the studied species will have to alter their habits or range of habitat in some way. “We found a mixed bag – some positive and some negative,” said Dr Gretta Pecl, lead author of the study. “Some species are shifting south and increasing their range, while others are already at their tolerance for temperature and as it warms, their range will shrink. “In Tasmania, there’s been an increase in snapper and yellow-tailed kingfish, which is great for the fishing industry. But in South Australia, there may be parts of the gulf regions unsuitable for snapper and it may decline there. “Temperature will be the major factor and off the coast of Tasmania the rate of warming is four times the global average. For species that are highly sensitive to temperature, it will affect the rate of growth, the amount of energy it needs and its oxygen consumption. Almost no aspect will be unaffected.” Dr Pecl said fish species were being increasingly sighted outside their traditional ranges.