July 13, 2018 10:25:31
Climate change could be a good thing for a species of fish that farms its own food, according to a university study.
The herbivorous damselfish maintains an algae garden that it weeds and defends from other animals.
A University of Adelaide study looked at damselfish waters containing a lot of carbon dioxide and found climate change would actually help damselfish grow more food.
Project leader Professor Ivan Nagelkerken said algae crops would be “fertilised” by the increased carbon dioxide [CO2] the ocean would absorb from the atmosphere.
“They grow little gardens, they defend these gardens, and they take out weeds that are not nutritional and essentially they crop their own farms,” Dr Nagelkerken said.
“It’s like they use human cropping practices.
“In a future ocean, whenthe excess of CO2 we’re emitting into the atmosphere is absorbed by the ocean, it acts as a fertiliser for these crops.
“As such,these fish can grow crops at a faster rate and that’s why they need a smaller space, so the ocean floor can handle more farming damselfish in a future ocean.”
However, Dr Nagelkerken said the research also provided a glimpse of what the world’s oceans could look like due to climate change.
He said while many species may struggle to survive as the oceans got warmer, the damselfish was likely continue to thrive.
“While the overall number of animals in the world might not decrease, the number of unique species might decrease,” he said.
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Dr Nagelkerken said as climate change progressed, ecosystems would become less diverse because species more suited to climate change would take over from those less suited.
He said on land that could include species such as mice and rabbits while the world’s oceans may become home to a lot more damselfish farms.
Climate change winners and losers
Up to 70 per cent of Australian sea species could be affected by climate change, but that is not bad news for every species, according to CSIRO scientist Beth Fulton.
The United Nations recently released report on the future of the world’s fisheries.
The Australian chapter of the reportdrew on Dr Fulton’s research.
Dr Fulton said species such as lobsters and abalone would feel the effects of climate change before more mobile species.
“Over the next 10 to 20 years there will be nowhere in Australia that doesn’t see some change driven by, or helped along by, climate change,” she said.
“In the short term it’s likely to be shallow in-shore species that are likely to feel the strongest changes.
“It’s the animals that can’t move fast, can’t move far, and therefore can’t escape the negative consequences that will suffer.”
More than 100 Australian marine species have already started migrating south to reach cooler waters, according to the CSIRO.
However, Dr Fulton said species such as mackerel, sardines, and anchovies would most likely benefit from climate change.
She said certain species benefitted from climate change because they preferred warmer climates, were able to breed for longer, and because changing temperatures eliminated predators and competitors.
Crabs on the move
Wildcatch Fisheries SA president and fisher of more than 30 years Dennis Holder said, over his career, he had noticed a change in the distribution of blue swimmer crabs and wondered if that could be attributed to climate change.
Mr Holder started fishing for blue swimmer crabs in 1986 off Ceduna before moving to Adelaide in 1989.
He said he had noticed that the larger and more valuable crabs in St Vincent Gulf have moved about 40km south.
“We’ve caught them as far south as Port Noarlunga, so it’s quite a substantial increase in their range,” he said.
Meanwhile, according to Mr Holder, crabs in the northern fishing spots tended to be smaller.
“The further you have to travel,there’s always more cost but [at] a lot of our traditional grounds north of Adelaide, the crabs seem to be far smaller and more undersized,” he said.
“As the population grows, the bigger ones go further so we go further south for the bigger crabs.”
Mr Holder said garfish could be affected negatively by climate change but he expected to see growth in crabs and Balmain bugs.