White Sharks - Carcharodon carcharias

Photo: Pelagic Shark Research Foundation

Photo: Pelagic Shark Research Foundation

The great white shark is the worlds largest known predatory fish, reaching 21 feet in length and weighing up to 4800 lb. Average size is around 15-16 feet, but there have been unconfirmed reports of sharks as large as 25 feet. Color ranges from a dark blue grey to bronze to a light grey dorsally, fading to snow white ventrally. The white shark belongs to the Lamnidae (mackerel sharks), which include mako and salmon sharks as well. Along the California coastline, adult white sharks are an important predator of marine mammals, focusing mostly on elephant seals. Juveniles feed mostly on fish, switching to marine mammals once they reach approximately 1000 lbs. The upper teeth are triangular and sharply serrated, and are used for cutting large pieces out of prey items. Bottom teeth are narrower and not serrated, and are used for holding prey items. An interesting note is that white sharks actually maintain parts of their body (swimming muscles and stomach) at temperatures well above that of the surrounding water, which classifies them as endothermic, like mammals.

DISTRIBUTION

White sharks are found in the temperate coastal waters of both the Pacific and Atlantic oceans. Along the California coast, they can be found hunting near elephant seal haul-out areas from October through March. Though considered an open-ocean dweller, it frequently wanders into shallow waters, and even into surf zones. In North American Waters, it has been reported from Newfoundland to Florida, and from Southeast Alaska to southern California. Nowhere in its range is it very common.

REPRODUCTION

Very little is known about the reproductive process of the white shark. Development is ovoviviparous. The smallest known free swimming white shark measured 51 in. and 36 lbs. Along the West coast of North America, it is believed that white sharks give birth to their live young in the warmer southern California waters. They young may then slowly migrate northward as they grow larger.

BEHAVIOR

Recent research on interactions between white sharks and elephant seals suggests that white sharks hunt their prey mainly visually. Using their dark dorsal colors to help them blend in while cruising near rocky bottoms, they watch for unsuspecting seals on the surface above. When an acceptable animal is sighted, they accelerate quickly and ram into the seal, stunning it, and at the same time take a large bite from the animal. They can then return after a time to leisurely feed on the carcass. It should be noted that white sharks can take considerable damage from their prey items, and many animals we have seen have deep scarring on the head from the teeth and claws of elephant seals. It is still undetermined whether white sharks are territorial towards one another, though based on current observations most seem to possess a home range. After one white shark makes a kill, often others will come and feed off the same kill, with no apparent aggressive interactions. We hope to study interactions between individual white sharks further, and also to find out whether they always return to the same feeding areas every year.

CONSERVATION

While of little commercial value, fishing for white sharks had become an increasingly popular sport with big game fish anglers. The fearsome reputation of the white shark has given it almost legendary status. However, this relatively uncommon predator is much more likely to be killed by humans for sport than the other way around. In fact, most attacks by white sharks on humans are not fatal. Realizing the importance of this species as a key predator in many ecosystems, the white shark was granted protected status in 1994 in California, and soon after in South Africa and Australia. Protected status for white shark in California is due to expire in 1999.

New Years Point and its associated island were first discovered by westerners on New Year's day 1603. Spanish Naval Captain Sebastian Viscaino named the point "Punta Del Ano Nuevo" and noted that the low rocky point was infested with wild sea creatures. Centuries later the site has become a state park and wildlife refuge. The often-treacherous channel between the island and the mainland is nearly a mile wide and must be traversed by researchers and rangers in an inflatable zodiac w/ outboard. The island is off limits to the public because of its sensitivity. In 1906 the United States Coast Guard established a lighthouse and station in hopes of remedying the numerous shipwrecks that became peculiar to the area. During the Second World War the island was modestly fortified and was used as a naval observations post. Some years after the war a new lighthouse was established at Pigeon Point and the facility on Ano Nuevo Island was abandoned as too costly to maintain. There had been nearly a dozen fatalities in and around the island's channel through the course of the facilities 50 or so years of operations. In the early 1970's UCSC Professor Burney Le Boeuf established a research station among the ruins of the old Coast Guard facility. Long known as an area frequented by large sharks the white shark research project began in earnest during the fall of 1992. Van Sommeran/PSRF	Photo by PSRF
Shark Station Zebra Ano Nuevo Island is the base of operations for the white shark study. Shark researchers share the island with marine bird and mammal researchers. Professor Le Boeuf established a research station among the ruins of the old abandoned U.S. Coast Guard facility in the early 1970's. The white shark project began in 1992 and coordinates efforts between island and vessel-borne operations. The island is an extremely sensitive site as many elusive species of marine birds and pinnipeds have returned to the island. Because of this sensitivity and abundance the island is off limits to the public. The island presents an ideal field lab. Van Sommeran/PSRF	Photo by PSRF
Another aerial recon photo of Ano Nuevo Island. Van Sommeran/PSRF	Photo by PSRF
Looking west from Point Ano Nuevo across the channel to the abandoned Coast Guard mansion on Ano Nuevo Island's southern point. The area is a wildlife reserve and state park. Casper/PSRF	Photo by PSRF
An adult bull northern elephant seal of about 2 tons catches some sleep in between bouts of brawling with rival males. The bull elephant seals fight for dominance over the harems of females that cover the islands small beaches. The northern elephant seal is the deepest diving of all marine mammals, rivaled only by the massive sperm whale both species can dive down to depths of 5000 feet. Elephant seals live most of their lives on the open ocean often feeding on deepwater squid. It is unknown whether or not white sharks follow the elephant seal migrations or rather intercept them at the rookeries and haul-outs like Ano Nuevo Island and the Farallons. Casper/PSRF	Photo by PSRF
Looking east at Ano Nuevo Island's western seaward shore. The channel is on the other side of the island. This is the view of the island that the research boat has much of the time while awaiting predatory events. The dark colored mansion is on the right of the island, The fog horn building is the light colored building in the right center of the island and the light tan colored bunker can be seen to the left of the fog horn building. Van Sommeran/PSRF	Photo by PSRF
An inflatable UCSC zodiac w/ a 15 horse outboard is used to transfer supplies and personnel to and from the island. The channel can be treacherous during the winter months and skiffs have been over-turned. Wet suits are required on even calm days. In the foreground a sub adult bull carries the scars of an encounter with T-Rex. While bull elephant seals are extremely tough and do not go quietly when attacked, even alpha bulls are a potential target for the worlds largest known predatory shark, the white shark, C. carcharias. (T-Rex). Part of the island based shark researcher's daily routine is to survey all the island's beaches and haul outs for evidence of shark bites on pinnipeds. Casper/PSRF	Photo by PSRF
At the change of every tide a member of the island crew surveys all the islands beaches and haul-outs for bitten and dead pinnipeds or other evidence of shark activity. This unfortunate California sealion was badly bitten by a white shark. The sealion's body cavity was breached and its vital organs were exposed when it worked its self up the beach where it expired after 5 days. It is not unusual to find parts of partially consumed pinnipeds washed ashore during periods of heavy shark predation. Kochly/PSRF	Photo by PSRF
This fortunate California sealion was able to escape an attacking white shark and live to bark about it. While its rudders and tail section were badly shot up, the sealion had no major structural damage and was able to recover from his wounds. Van Sommeran/PSRF	Photo by PSRF
The abandoned Coast Guard mansion. On the island, facing to the northeast one can view the island's southwestern shore. The lighthouse keeper's mansion was abandoned to the sealions and marine birds after a new lighthouse was built at Pigeon Point during the late 50's. A research station has been established within the old USCG facility's fog-horn building and cement bunker which was more able to withstand the rigors exposure. A well-weathered study blind can be seen on the cliff ledge to the left. Form this blind researchers can observe the behaviors of the islands marine birds and pinnipeds. Casper/PSRF	Photo by PSRF
S. Van Sommeran stands on the island's high ground while standing the morning watch. Researchers on the island communicate via VHF marine radio and cell phone with a research boat that orbits the island's seaward side, drifting lures and keeping a sharp look out for predatory events. At each tide change a survey of the island's beaches and haul-outs are conducted to record the occurrences and locations of bitten pinnipeds. A typical island crew consists of 2 to 4 researchers who stay on the island for 3 to 5 days. The research station has a diesel generator in the old fog horn building that provides electricity to light the compound and support a kitchen facility, which is located in the old concrete bunker. The research boat "Pelagic 1" can be seen on the horizon to the extreme left of the photo just above the crumbling wall. A VHF marine radio antenna can see seen sticking up from the roof of the concrete bunker at the right of the photo. Styllos/PSRF	Photo by PSRF
Ano Nuevo Island is the seasonal home to numerous species of rare and endangered marine birds and pinnipeds. Researchers with UCSC and PRBO study auklets, cormorants, pelicans, and other marine birds, which use the island for nesting or shelter. Hein/PSRF	Photo by PSRF
Harbor seals are relatives of the elephant seal, (Phocids). Like the elephant seal, the harbor seal is a diver propelling itself with its hind flippers whereas sealions like the California and Stellar's sealions propel themselves with powerful strokes of the fore flippers, (Otarids). Harbor seals can out dive sealions and can dive as deep as 1500 feet. White sharks are known to consume them all. Casper/PSRF	Photo by PSRF
Stellar sealions are almost three times the size of California sealions. These female Stellar's are very valuable because they are breeders for an endangered species. Hein/PSRF	Photo by PSRF
California sealions (zalophus) body surf in the channel between the island and the mainland. Hein/PSRF	Photo by PSRF
Research vessel crew, from left to right, Dr. Dave Casper, Sean Van Sommeran and Ross Hein wait out their watch while aboard the "Pelagic 1" (PSRF research boat) during a long uneventful rainy day December of 1995. 1995 was the first year that PSRF began to approach predatory events and during the course of that season they were able to tag 12 white sharks, (a national record). Many an uneventful day is spent by the crew with nothing to do but watch the wind blow. Fall of 1996. Casper/PSRF	Photo by PSRF
Surface lures in the shape of e-seals are used to draw the sharks to the surface in order to photograph and tape the sharks for ID purposes and to attach transmitters and tags. The surface lure, or target, as it is sometimes referred to, is painted brown on the bottom and white on the top. The surface shape is drifted away from the boat at a discrete distance and watched closely. Oct 1997. Scott Davis/PSRF	Photo by PSRF
As the surface target drifts over certain areas, sharks will often make a pass at the lure or may actually strike a target. The average life-span of a white shark surface decoy at Ano Nuevo is not very long and must typically be replaced within a season or two at most, Oct 1997. Scott Davis/PSRF	Photo by PSRF
In this shot a large white shark can be seen as it grabs the lure in its mouth and carries it briefly. Dec 1996. Fritz-Cope/PSRF	Photo by PSRF
In the above photo the view is to the southeast. In the upper left side of the photo the island and the northwest side of the island's base station can be seen. The tan building is the old "fog horn building" where the research team resides. Casper/PSRF December 1995.	Photo by PSRF
A 1200 lb. sub adult female white shark is fended off of the boats outdrive as it makes a fast pass at the stern of "Pelagic 1". January 17, 1997. The shark was drawn to the surface with the surface lure and the shark then took a brief interest in the boats outdrive. Scott Davis/PSRF	Photo by PSRF
A stricken elephant seal struggles at the surface as a large shark bites it below the turbulent surface. Oct 1995. Dave Casper/PSRF	Photo by PSRF
In this shot a large female white shark surfaces and vigorously gorges itself on the carcass of a sub adult male northern elephant seal. Oct 31, 1995. Dave Casper/PSRF	Photo by PSRF
In this simplistic chart we see the two different strategies believed to be employed by white sharks to prey upon seals and sealions. White sharks are known to hunt both types of pinnipeds. Sealions belong to the group of pinnipeds called Otarids and seals to the group called Phocids. Otarids are often referred to as "eared seals" and Phocids as "ear-less seals". Sealions use their fore-flippers to propel themselves through the water and typically travel along the surface, often porpoise'ing. Seals on the other hand, propel themselves with their hind-flippers and typically travel along the bottom while only surfacing to resporate between dives. Elephant seals and harbor seals are both Phocids who are capable of diving to great depths. The harbor seal can dive to over 1500 feet. The northern elephant seal can dive to 5000 feet. Wild California sealions can dive to 350-400 feet tops. Klimely/PSRF	Photo by PSRF