UTS scientists reveal human impact on marine ecosystems

Groundbreaking research by UTS marine scientists is providing invaluable insights into the world's marine ecosystems and the impact that humans are having on them.

UTS marine scientist Professor David Booth has investigated the impact of climate change on tropical fish on Australia's East Coast; while a Postdoctoral Fellow in of Booth's group Dr Peter Biro has investigated the effects commercial fishing is having on fish behaviour.

Professor David Booth

Professor Booth and his fish ecology group had followed the journey of a number of tropical fish species from Queensland's Coral Sea down the NSW coast, a journey enhanced by a 2°C rise in temperature of the East Australian Current (EAC).

He said tropical fish migrate south and dwell in the temperate waters of NSW during the warmer months; however the mortality rate was almost 100% during winter months. Recently though, tropical fish have been found surviving longer and further south due to increased over-winter water temperatures.

"In the past six years we have had the two warmest winters since 1848, resulting in very high levels of survival of tropical fish species," Professor Booth said. "The warming ocean is permitting tropical fishes to survive into the cooler winter months.

"Eventually we may see breeding populations of previously-tropical reef fish species in Sydney and its surrounds, which means we will get a general shift of tropical fish populations southwards. On the flip-side, the predicted rise in ocean temperatures of 1-3°C is likely to severely stress many southern species, around which major fisheries revolve,  which may already be at, or near, their thermal maximum.

"There is increasing evidence that humans are a major factor in recent climate change. While we know we have other cycles going on in nature, climate change is happening, that’s indisputable, whether its all due to human influence is not 100% certain.

"Tropical fish larvae in SE Australia don’t  themselves have a hige impact on humans, but what they tell us about movement and temperature of the ocean's water is important." 

Professor Booth said he had been engaged in this study for nine years; however monitoring will continue  in the face of variability in marine environments to determine long-term trends in tropical fish numbers.

Dr Peter Biro

Meanwhile, research undertaken by UTS marine scientist Dr Peter Biro is showing that humans are unintentionally changing fish behaviour or "personalities."

Dr Biro's studies have shown that fish consistently differ in their individual behaviour, and that bold/active fish are more easily harvested by fishing than shy/inactive fish. "Humans are inadvertently but directly altering the behaviour of fish through their actions," Dr Biro said.

Dr Biro has shown most fish caught are the bold adventurous type, which raises the question of whether bold genotypes may become extinct from overfishing. This would then lower fishing productivity as the remaining fish would be the shy types that grow and reproduce more slowly.

"Animal behavioural variation in the context of commercial fisheries could cause evolution towards less productive types." he said. "The real impact is that the fish that remain are not very productive in terms of growth or reproduction.”

"An example of where this has already occurred is the cod fisheries of North America, which due to overfishing of bold, fast growing and active cod, have collapsed and have not recovered despite a ban on fishing for the last 15 years."

Mr Biro said he had also recently discovered the surprising effect that tiny water temperature increases are having on personalities of coral reef fish.

"We knew temperature affected fish activity but what was unusual was the fact that just 2-3°C increase in temperatures that fish normally experience on a daily, or day to day basis, increased levels of activity and boldness by six times," he said.

"This has potentially important implications in the context of climate change. It suggests that fish will potentially become excessively active and bold and be at greater risk of capture by humans and greater risk of being eaten by their natural predators."

The research of Professor Booth and Dr Biro has been recently published in journals including: Global change Biology; Proceedings of the National Academy of ScienceProceedings of the Royal Society of London Series B and Marine Ecology Progress Series.


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