The study was a collaborative project between Neil Hammerschlag of the at the and of Apex Shark Expeditions, a company that conducts cage diving and shark viewing trips. A white shark off the coast of Mexico. The study covers more than 8000 hours of shark observations in South Africa's spread out over the past 18 years. The great white shark population remained relatively stable until 2015, at which point their numbers went into sharp decline, sometimes reaching zero during 2017–2018. At those times, another predator, the sevengill shark, previously unknown in the study area, began to appear. The sevengill is sometimes called a living fossil because it closely resembles similar sharks from prehistoric times. The study itself outlines the tight correlation between the absence of white sharks and the presence of sevengills: "[S]evengill sharks [...] were only detected during the prolonged periods of complete white shark absence, disappearing from our surveys during the intermittent short periods when white sharks temporarily returned to Seal Island, albeit in very low numbers, only to reappear when the white sharks were again absent from surveys[.]" Two orcas, also called killer whales, off the coast of Alaska. The sevengill shark usually lives in areas where the sea floor is thick with kelp, as opposed to the relatively clear-bottomed study area. The sevengill and great white are both ordinarily apex predators and seek some of the same food, such as , but great whites can also prey directly on sevengills. The great white shark and are the only species known to eat adult sevengills. The sevengill has seven gills, whereas most species of shark have only five gills on each side of their bodies. A sevengill shark in False Bay. The scientists behind the present study only note various hypotheses about the cause of the disappearance of great white sharks from this area, though Dr. Alison Kock of the has reported a correlation with the entry of orcas into False Bay, possibly because human activity has rendered prey hard to find elsewhere. These orcas, she suggests , specialize in hunting sharks.
The study was a collaborative project between Neil Hammerschlag of the at the and of Apex Shark Expeditions, a company that conducts cage diving and shark viewing trips. A white shark off the coast of Mexico. The study covered more than 8000 hours of shark observations in South Africa's spread out over the past 18 years. The great white shark population remained relatively stable until 2015, at which point their numbers went into sharp decline, sometimes reaching zero during 2017–2018. At those times, another predator, the sevengill shark, previously unknown in the study area, began to appear. The sevengill is sometimes called a living fossil because it closely resembles similar sharks from prehistoric times. The study itself outlined the tight correlation between the absence of white sharks and the presence of sevengills: "[S]evengill sharks [...] were only detected during the prolonged periods of complete white shark absence, disappearing from our surveys during the intermittent short periods when white sharks temporarily returned to Seal Island, albeit in very low numbers, only to reappear when the white sharks were again absent from surveys[.]" Two orcas, also called killer whales, off the coast of Alaska. The sevengill shark usually lives in areas where the sea floor is thick with kelp, as opposed to the relatively clear-bottomed study area. The sevengill and great white are both ordinarily apex predators and seek some of the same food, such as , but great whites can also prey directly on sevengills. The great white shark and are the only species known to eat adult sevengills. The sevengill has seven gills, whereas most species of shark have only five gills on each side of their bodies. A sevengill shark in False Bay. The scientists behind the present study only noted various hypotheses about the cause of the disappearance of great white sharks from this area, though Dr. Alison Kock of the has reported a correlation with the entry of orcas into False Bay, possibly because human activity has rendered prey hard to find elsewhere. These orcas, she suggested , specialize in hunting sharks.
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