Human exclusion zones the best for shark populations

NEW research from a Deakin University ecologist has found no-take marine reserves are failing to restore the Great Barrier Reef’s shark populations back to natural levels.

Published on Friday February 1 in the journal, “Frontiers in Ecology and the Environment”, the study revealed that after decades of protection, shark populations on the Great Barrier Reef were only recovering in human exclusion zones.

Researcher Dr Justin Rizzari, a lecturer in fisheries science at Deakin’s School of Life and Environmental Sciences, said although fishing is illegal in both areas, shark numbers were more than double in human exclusion zones compared to traditional no-take marine reserves.

“The results indicate that restoration of nearnatural shark populations requires several decades, but more importantly these results demonstrate the superior performance of human exclusion zones at rebuilding shark populations,” Dr Rizzari said.

“This is important as no-take reserves are firmly advocated as an effective tool to rebuild overexploited fish and shark populations and to restore natural ecosystems.”

Dr Rizzari also said the sharks found around the Great Barrier Reef, including grey reef sharks, blacktip reef sharks and whitetip reef sharks, were an important part of the food web and a key indicator of a healthy ecosystem.

With recent research showing significant poaching levels within the Great Barrier Reef Marine Park, Dr Rizzari said illegal fishing was the most “plausible explanation” for the difference in populations.

Co-researcher Dr Ashley Frisch, from James Cook University’s ARC Centre of Excellent for Coral Reef Studies, said new research estimated between three and 18 per cent of recreational fishers participated in illegal fishing.

“Poaching doesn’t have to be at a high level for shark populations to decline, as these species are slow growing and reproduce at a low rate,” he said.

“With better compliance, no-take reserves may yield even better conservation results than previously seen, but full recovery, including of reef sharks, will likely take at least two or three decades.