June 19, 2018 — Australia’s management of its fisheries and marine ecosystems is widely considered among the best in the world. But the first independent peer-reviewed study of targeted fish stocks in Australian waters has found alarming population declines.
“Regardless of its reputation for sustainable fishery management, overfishing has apparently contributed to … declining biomass of large fishes on Australian reefs,” wrote Graham J. Edgar and Rick D. Stuart-Smith of the Institute for Marine and Antarctic Studies at the University of Tasmania, and Trevor J. Ward of the University of Technology Sydney, in a paper published in the journal Aquatic Conservation.
The study found a 36 percent decline over the past 10 years in the total biomass of fish 20cm (8in) or more in length in zones where fishing is unrestricted. Where fishing is regulated, the decline was 18 percent. No-fishing areas, in contrast, saw a 4 percent increase in biomass. To test whether the fall was a function of environmental pressures other than fishing, the scientists looked at species that are not fished and found their drop in biomass was “non-significant.”
“Populations of exploited fishes generally rose within marine reserves and declined outside the reserves, whereas unexploited species showed little difference in population trends within or outside reserves,” the researchers wrote.
They reached those conclusions by analyzing a decade’s worth of fish counts conducted by the Reef Life Survey, an independent visual census that does not rely on fisheries data or involvement. Australian fisheries authorities, on the other hand, evaluate fishery stocks by looking at “catch per unit effort.”