Shark Below Zero Full Episode 🦈 | @natgeokids

Key Concepts

White shark migration, acoustic tagging, satellite tagging, shark behavior, diet, habitat, water temperature, Canadian waters, Cape Cod, juvenile sharks, adult sharks, territoriality, marine ecosystems, climate change, listening stations, camera tagging.

Shark Attack in Canada and Initial Investigation

In August 2021, a 21-year-old woman was attacked by a shark in Cape Breton, marking the first confirmed shark bite in Canadian waters in over 150 years. Shark experts Megan Winton and Greg Skomal investigated the incident, noting that unprovoked attacks this far north are rare. They considered potential shark species, ruling out basking sharks (plankton eaters), porbeagle sharks (small and rarely implicated in attacks), and blue sharks (relatively harmless). They concluded that the most likely culprit was a great white shark.

White shark sightings in Canadian waters have increased in recent years. Up to 2006, there were only 32 recorded sightings, but the numbers have been growing. Megan and Greg aimed to tag a white shark in Canadian waters to understand why they are moving north.

Using a drone, Megan surveyed the attack site and observed a large number of gray seals, an ideal prey for white sharks. White sharks are ambush predators, using their gray backs to blend into the deep water. They have highly sensitive eyes that can detect contrasts between light and dark, making seals or swimmers silhouetted against the surface easy to spot. The attack was likely carried out by a juvenile, inexperienced shark that made a "bad decision."

Tagging Sharks in South Carolina

In February, Greg and Megan traveled to Hilton Head, South Carolina, to tag white sharks and track their movements north. They teamed up with Chip Michalove, who has been tagging sharks for Greg's Atlantic white shark study for six years. They fished 60 miles offshore in deep water, where white sharks ambush prey like dolphins.

Megan prepared acoustic and satellite tags. Acoustic transmitters "ping" every minute, and the data is collected by acoustic receivers along the US and Canadian Atlantic coasts. Satellite tags record light level, temperature, and depth data for a year, providing information on the shark's broad-scale movements.

The team successfully tagged a 9-foot juvenile female shark named Reese, the 283rd shark in the Atlantic white shark study. Reese's acoustic pinger will track her movements for 10 years, while her satellite tag will detach after a year. Over the next few weeks, Chip tagged seven more white sharks, bringing the total number of Carolina sharks tagged that winter to eight.

Shark Migration and Cape Cod

Over the next three months, all eight tagged sharks headed north, their signals logged by a network of listening stations. White sharks are lamnids, a family of sharks that can keep their bodies warmer than the surrounding water, allowing them to thrive in colder waters.

By June, sharks Josiah and Barnacle Ben reached Cape Cod, Massachusetts, the "white shark capital of the Atlantic." Hundreds of white sharks gather there to feed on the large seal colonies, estimated to number up to 50,000 seals in the summertime. Greg has studied white sharks in Cape Cod for a decade, discovering that they hunt close to shore in shallow water. He uses aerial spotting to locate sharks and tag them without using hooks.

By the end of July, 12 more sharks were tagged, bringing the total in the Atlantic white shark database to 560. However, some tagged sharks left Cape Cod and headed north, including Reese, Pavll, Sicklefin, and Eddie, bypassing Cape Cod altogether.

Return to Canada and Initial Tagging Attempts

Greg and Megan followed the sharks back to Canada, aiming to deploy the first-ever camera tag on a white shark in Canadian waters. They noted that finding sharks in Canada would be more challenging than in Cape Cod due to the larger area and deeper water.

Their first destination was the southern tip of the Nova Scotian Peninsula, near the site of the previous year's shark attack. Over 20 white sharks were detected on listening stations in the area, and local fishermen reported increased sightings. They met with Canadian shark experts Heather Bowlby and Warren Joyce, who have been investigating Canadian white shark sightings for over five years.

Warren and skipper Eric Jackard decided to start their hunt based on recent sightings. Megan prepared a camera tag with sensors that record movement and navigation data 20 times per second. The camera would provide insights into how sharks use Canadian waters.

The team used baited lines to attract sharks, relying on their sensitive noses. After eight hours, a white shark took the bait. The team attempted to pull the shark closer for tagging, but it moved off into the deep. Footage from cameras on the bait lines revealed that the shark was a juvenile female, estimated to be 9-10 feet long.

Juvenile Sharks and Territoriality

The size of the shark was an important clue, as Greg and Megan typically see larger, adult males in Cape Cod. They speculated that territorial adult males might be pushing smaller sharks north into Canadian waters. Scars and bite marks on sharks indicate social interactions and potential territorial disputes.

Canada's Atlantic waters have rich fishing grounds, and the cold Labrador Current mixing with the Gulf Stream creates nutrient-rich conditions. Combined with warming waters, this could be attracting white sharks north.

Newfoundland and Water Temperature

With strong winds hindering their search, the team split up to check listening stations. Greg traveled to Conception Bay, Newfoundland, the furthest north white sharks have ever been found. He joined Mike Pierac from Fisheries and Oceans Canada to check the listening stations.

The bay is a deep fjord with abundant food sources, attracting cod, tuna, and potentially white sharks. However, no new sightings were recorded. Greg noted that they were at the northern limit of the shark's range, a dangerous place for the species.

White sharks prefer water temperatures between 52 and 80°F and can die if exposed to temperatures as low as 39°F for too long. Greg had seen thresher sharks cold-shocked and washed ashore frozen in Cape Cod after a rapid temperature drop.

Nova Scotia Detections and Tagging Success

Back in Nova Scotia, Megan and Warren checked local listening stations and found that Shark 9142, a South Carolina shark named Asheville, had arrived. She was tagged by Chip in 2019 and had spent the spring moving up the eastern seaboard, arriving in Cape Cod on June 23rd. This was the third time Asheville had been detected in Canadian waters.

Three more sharks were detected, including a large male called Mr. Frisky, but the rest were juveniles. The team returned to Wedgeport, Nova Scotia, to attempt to tag a shark with a camera tag. A shark checked out the baited lines, but the tagging attempt failed as the shark remained too deep.

With only four days left, the team decided to try a new location in the Bay of Fundy, known for its high tidal surges. They baited the water, and a white shark appeared. After a tense moment, Greg successfully deployed the camera tag on the shark, nicknamed Quatti, marking the first time a camera tag had been deployed on a white shark in Canada.

Camera Tag Data and Shark Behavior

The team tracked Quatti using a hydrophone, recording its depth, speed, acceleration, and direction. Quatti stayed close to the shoreline at a depth of 75 feet, then moved into deeper water, staying in the top 200 feet. After 30 minutes, it sped up and headed south, and the signal was lost.

The next day, the tag was recovered. Footage revealed that Quatti went straight to the bottom, where it was dark. It then moved into deeper water before returning to shallower, warmer waters. The footage also showed Quatti turning and grabbing something in its mouth, indicating that it had fed. The prey could have been dogfish, skates, or halibut.

The camera tag data provided the first glimpse into what white sharks are doing in Canadian waters, revealing that they operate differently than in Cape Cod. They are opportunistic predators with a diverse diet, taking advantage of the unique habitats in the area.

Climate Change and Shark Distribution

On September 3rd, Greg traveled to Newfoundland to meet Frederick Seir at Memorial University to discuss sea temperatures. Seir's monitoring program has shown a warming trend in surface waters over the past 30 years.

Warming surface waters could be allowing white sharks to penetrate further into Canadian territory. Data showed that the isotherm was moving up, indicating that white sharks are likely to arrive earlier, spend more time there, and leave later. However, below 50 meters, the water remains cold, even in summer.

This explains why white sharks spend most of their time in the warm surface layer, only diving briefly to deeper depths. The dive pattern of the camera-tagged shark confirmed this behavior.

Conclusion and Future Outlook

The team's review of the year's listening station data revealed that many sharks normally seen off Cape Cod were in Canada, including Broken Tail, Scary Shark, and Mr. Frisky. Additionally, many South Carolina sharks were detected, but not many large adults.

In total, 78 individual white sharks were detected in Canadian waters, the most since monitoring began. This is compared to 120 off of Cape Cod. This evidence suggests that Canada is a white shark hotspot, particularly for inexperienced juvenile sharks, which may explain the first shark bite in 150 years.

The research showed that white sharks are spreading out throughout Canadian waters and adapting to the environment. It is likely that white sharks will continue to be seen off Canada, and possibly in greater numbers.