San Francisco’s KGO-TV (ABC 7) reports that a recently published study on great white shark counts off of California’s central coast indicates that the number of white sharks is “surprisingly low.”
The study was published in The Royal Society’s Biology Letters. Researchers used photographs of dorsal fins to identify 130 unique white sharks at the Farallon Islands off Central California. An algorithm was then used to determine an estimate of 219 mature and sub-adult white sharks in Central California. The study notes that this number is “substantially smaller than populations of other large marine predators.”
Other researchers have pointed out that since this is the first study of its kind in the region that there is no baseline figure to compare the estimated count to.
Chris Lowe of CSULB’s SharkLab , quoted in a Discovery News, suggests that “using traditional marine mammal survey methods on a non-air breathing species” could result in lower numbers, since there could be a lower chance of seeing white sharks on the surface, as opposed to counting marine mammals who must surface to breathe.
Sean R. van Sommeran, of the Pelagic Shark Research Foundation, also chimed in on the topic in the comments section of the Discovery News article and stated that “the figure of 200-300 hundred adults has been conventional wisdom among California Field Researchers since the late 1990s.” He also went on to note that his research team has not seen “more or fewer” sharks since 1990 at the Farallones.
On a related note, the Shark Diver blog weighs in on the estimated numbers at the Farallon Islands, as well as count estimates at Isla de Guadalupe.