Tuesday, 23 August 2016

Mix of marine zones matters most for prey fish


August 17, 2016

In a first-of-its-kind study, James Cook University scientists have discovered a mosaic mix of marine zones could benefit populations of prey fishes.

The research, conducted by JCU's Dr April Hall and Professor Michael Kingsford, looked at whether fishing of predators on the Great Barrier Reef had effects on the reproductive dynamics of their prey.

Dr Hall said it was the first study to demonstrate that the depletion of predators can cause cascading ecological effects, and impact prey species at a biological level.

The scientists collected a prey species - the bridled monocle bream - from two management zones in the Palm Island group: marine reserves, which are protected from fishing, and open zones, which are heavily fished.

Predators such as coral trout, snapper, and emperor fish are popular fishing targets on the Great Barrier Reef, and play a vital role in coral reef food webs.

"We predicted that in marine reserves, where predators were abundant, prey would allocate more energy to predator avoidance compared to fished zones with fewer predators, and that this would affect their growth and reproduction," said Dr Hall.

The team found that in the predator-rich marine reserves, the bream had reduced growth, poorer body condition, and a reduced capacity to reproduce compared to fished areas.

In fished areas, depletion of predators meant prey species grew faster, and had a greater reproductive capacity.

Dr Hall said that the study emphasises the importance of long-term protection of predators in marine reserves.

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