A new study has revealed that shortfin mako shark catches in the western North Atlantic have been under-reported by fishermen, and this species may be more threatened than previously thought.
A team of researchers, using satellite tracking, have discovered that the number of shortfin mako sharks caught by fishermen in the western North Atlantic is much higher than previously reported.
The results of their study, published in the journal Proceedings of the Royal Society B, have cast concerns about the sustainability of this species if the fishery catches continue at its current level.
The study has been undertaken by researchers from Nova Southeastern University's Guy Harvey Research Institute (NSU's GHRI), the University of Rhode Island and other colleagues. It compares the data of mako shark catches obtained by satellite tracking and the data submitted by fishermen.
“Traditionally, the data obtained to determine the rate of fishing mortality, a key parameter used to help gauge the health of shark stocks, has depended largely on fishermen self-reporting any mako sharks they may have caught,” said senior author Mahmood Shivji, Ph.D., director of the NSU's GHRI. He added that the reliability of such data is questionable, as some fishermen may under-report or not report their mako shark captures at all.
In fact, the researchers were startled at the results of their study. They discovered that 30 percent of the 40 tagged sharks had been captured in fisheries. Upon further calculation, they concluded that shortfin mako sharks were killed in fisheries at a rate that was 10 times higher than previously believed.
Another finding of the study was that mako shark entered the management zones of 19 countries, demonstrating the importance of countries to work together to manage and conserve the species.
Bradley Wetherbee, Ph.D., a research scientist from the University of Rhode Island's Department of Biological Sciences and a member of NSU's GHRI, said, “It's vital that we have the most accurate data possible to aid decision-makers in managing marine life populations sustainably. If they have inaccurate information, it's much more difficult to make the correct decisions for properly managing populations. Everyone wants the populations managed in a sustainable way.”