Sharks & Rays
Great White Shark
Carcharodon carcharias
ALSO KNOWN AS
Great white, white shark, white pointer
DISTRIBUTION
Worldwide in sub-polar to tropical waters
ECOSYSTEM/HABITAT
Coastal to open ocean
FEEDING HABITS
Active predator
TAXONOMY
Order Lamniformes (mackerel sharks & relatives), Family Lamnidae (mackerel sharks)
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Great white sharks are an apex predator in the ocean best known for their power, speed and strength. They are the largest predatory fish in the world and are also the only shark that regularly feeds on marine mammals, often hunting whales, seals and sea lions. Their only known predators are certain populations of orcas and humans. White sharks are thought to have evolved 16 million years ago and are descendants from the megalodon shark, the largest shark to have ever existed. White sharks have a nearly global distribution and extended oceanic migrations that allow them to live in almost all coastal to offshore waters. They have even been observed at great depths of up to 1,200 metres! They are adapted to temperate to tropical waters and are a frequent visitor to both Canada’s Pacific and Atlantic oceans.
Great white sharks are an apex predator in the ocean best known for their power, speed and strength. They are the largest predatory fish in the world and are also the only shark that regularly feeds on marine mammals, often hunting whales, seals and sea lions. Their only known predators are certain populations of orcas and humans. White sharks are thought to have evolved 16 million years ago and are descendants from the megalodon shark, the largest shark to have ever existed. White sharks have a nearly global distribution and extended oceanic migrations that allow them to live in almost all coastal to offshore waters. They have even been observed at great depths of up to 1,200 metres! They are adapted to temperate to tropical waters and are a frequent visitor to both Canada’s Pacific and Atlantic oceans.
The great white shark is known for its large torpedo-shaped body. They have a conical snout, and the upper and lower lobes on their tail fin are approximately the same size – a common trait of other mackerel sharks. Great whites have countershading, meaning they have a grey topside and white underside, allowing them to ‘blend in’ to the ocean environment when viewed from either above or below. They also have large, deep blue eyes, pointed fins and large triangular teeth. The species is sexually dimorphic which in this case means females are larger than males. The average body length for a male is three to four metres, while females average four to five metres in length. The largest white shark ever recorded was a female just over six metres long, caught in the Gulf of St Lawrence off the coast of Prince Edward Island! These large females can weigh anywhere between 1,900 to 2,300 kilograms at maturity.
FUN FACT: A great white shark tooth was found in a Mi’kmaq oyster midden in Atlantic Canada dating back almost 2,000 years ago.
Most fish are considered “cold blooded”, but great whites have an adaptation to keep warm in colder waters. This adaptation is called counter-current circulation, which we also see in some marine mammals, and it allows great whites to keep their body temperature warmer than the surrounding waters.
Despite the white shark being so prominent in popular culture, little is known about their reproduction and life history. It is believed that these sharks can live to be 50 to 70 years or older, making them one of the longest-lived cartilaginous fishes, and it is estimated that they reach sexual maturity at the age of eight to 10 years for males and 12 to 18 years for females. They also reproduce via internal fertilization and give birth to live young after a gestation period of 11 to 14 months. It is still unknown where great whites give birth, although it is thought to be along the west and east coasts of North America. It is also thought that females have a three-year gap between birthing events. Given the shark’s late sexual maturity and low reproductive rate, they are considered a slow-growing species and are therefore vulnerable to human pressures, like overfishing and climate change.
Great white sharks are not directly targeted by any fisheries in Canada; however, they are caught in various gillnet, longline, and weir fisheries as bycatch. Unfortunately, other places in the world target great white sharks, particularly for their fins, teeth, and jaws. Oceana Canada successfully worked to ban the import and export of shark fins in Canada in 2019.
The International Union for the Conservation of Nature (IUCN) notes that very little is known about the actual population size of great whites, but it is generally agreed that their species is considered vulnerable to extinction worldwide. While shark populations can be difficult to determine, the great white shark population in the North Atlantic is estimated to have declined 80 per cent over the last 14 years. Efforts have been made to increase international research and cooperation for the protection of the species. In Canada, great white sharks were listed by Committee on the Status of Endangered Wildlife in Canada (COSEWIC) as Endangered in 2006 and listed under the Species At Risk Act (SARA) as Endangered five years later.
As great whites are one of the top predators in the ocean, their main threats come from human activities. From directed sport fishing and harvesting of body parts like jaws and fins, indirect fishing through bycatch, marine pollution, overharvesting of prey species and habitat destruction, there are many threats facing them today. There is a lot of effort currently underway to tag and study great white sharks in order to learn more about their habitat preferences, population distribution and other potential threats in order to enact strong evidence-based conservation measures.
