Decline of coastal apex shark populations over the past half century

• Published in: Communications biology Vol. 1; no. 1; p. 223
• Main Authors: Roff, George, Brown, Christopher J., Priest, Mark A., Mumby, Peter J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13.12.2018; Nature Publishing Group
• Subjects: 631/158; 631/158/1745; 631/158/672; 631/158/853; Biology; Biomedical and Life Sciences; Body size; Carcharodon carcharias; Galeocerdo cuvier; Life Sciences; Oceans; Predators; Protected species; Sharks
• ISSN: 2399-3642; 2399-3642
• DOI: 10.1038/s42003-018-0233-1

Overexploitation of large apex marine predators is widespread in the world’s oceans, yet the timing and extent of declines are poorly understood. Here we reconstruct a unique fisheries-independent dataset from a shark control programme spanning 1760 km of the Australian coastline over the past 55 years. We report substantial declines (74–92%) of catch per unit effort of hammerhead (Sphyrnidae), whaler (Carcharhinidae), tiger shark ( Galeocerdo cuvier ) and white sharks ( Carcharodon carcharias ). Following onset of the program in the 1960s, catch rates in new installations in subsequent decades occurred at a substantially lower rate, indicating regional depletion of shark populations over the past half a century. Concurrent declines in body size and the probability of encountering mature individuals suggests that apex shark populations are more vulnerable to exploitation than previously thought. Ongoing declines and lack of recovery of vulnerable and protected shark species are a cause for concern. George Roff et al. report a 74–92% decline in the catch per unit effort and concurrent declines in body size of large coastal apex sharks near Australia over the past five decades. This study highlights shifting baselines of shark populations in coastal shark assemblages, and indicates that shark populations are highly vulnerable to exploitation.