While great white sharks are protected from targeted fishing, their greatest threat is incidental capture (bycatch) in commercial fisheries that use entangling nets.
Set and drift gillnets — which together target California halibut, white seabass, yellowtail, thresher sharks and swordfish — are responsible for more than 80 percent of the reported young great white sharks caught in nursery grounds off Southern California. Reported bycatch in these fisheries from fishery logbooks has averaged more than 10 sharks per year since the 1980s, and has increased in recent years, but because observer coverage on these vessels is so low, the full extent of this bycatch remains unknown.
Young great white sharks off Southern California are also faced with contamination. These young sharks are found to have the second highest mercury level on record for any sharks worldwide and PCB and DDT levels in liver tissue that are the highest observed in any shark species reported to date globally. These mercury levels exceed six fold the established thresholds where harmful physiological effects have been documented in other marine fish.
The cumulative impacts of multiple stressors, including contamination, bycatch, coastal development, pollution, ocean acidification, and climate change, put West Coast great white sharks at great risk of extinction.