Migration of the Hawaiian Tiger Shark

Tiger sharks are one of the ocean's most iconic and feared predators. With their massive size and fearsome reputation, they can be found in many areas of the world, including the waters surrounding the Hawaiian Islands. These sharks are known to migrate long distances, which has been studied extensively by scientists over the years.

Tiger sharks in Hawai'i are known to migrate between the main Hawaiian Islands and the nearby atolls and seamounts, such as French Frigate Shoals and the Northwestern Hawaiian Islands. These migrations occur seasonally, with the sharks traveling to different locations during different times of the year.

One study conducted by scientists from the University of Hawai'i at Manoa used satellite tagging to track the movements of tiger sharks in the Northwestern Hawaiian Islands. The study found that the sharks traveled long distances, with some traveling over 2,500 kilometers in just a few months. The researchers also noted that the sharks tended to stay in deeper waters during the day and move into shallower waters at night.

Another study conducted by researchers from the University of Tokyo found that tiger sharks in Hawai'i tend to migrate toward the main Hawaiian Islands during the winter months. The study used acoustic tagging to track the movements of the sharks and found that they were more likely to be found in the waters surrounding the main Hawaiian Islands during the winter.

So why do Hawaiian tiger sharks migrate, and what factors influence their behavior? The exact reasons for these migrations are still not fully understood, but ongoing research is helping to shed light on this fascinating behavior.

One factor that may influence the migration patterns of tiger sharks in Hawai'i is changes in water temperature. Like many other shark species, tiger sharks are ectothermic, meaning their body temperature is regulated by the temperature of the surrounding water. Changes in water temperature may prompt the sharks to move to different locations in search of more favorable conditions.

The availability of prey is another factor that may influence the migration patterns of tiger sharks in Hawai'i. Tiger sharks are opportunistic feeders that will eat a wide variety of prey, including fish, turtles, seabirds, and even other sharks. As the availability of different prey species changes throughout the year, the sharks may move to different locations in search of food.

Breeding behaviors may also play a role in the migration patterns of tiger sharks in Hawai'i. While little is known about the mating habits of these sharks, it is thought that they may mate in deeper waters and then move to shallower waters to give birth to their pups. This could explain why the sharks tend to stay in deeper waters during the day and move into shallower waters at night.

Despite their fearsome reputation, tiger sharks are an important part of the marine ecosystem in Hawai'i. They help to maintain a healthy balance of predator and prey species, and their migration patterns are an important area of study for scientists interested in understanding the behavior of these powerful predators. By tracking their movements, researchers can gain valuable insights into the factors that influence their behavior and help to inform efforts to protect these important species.

Overall, the migration patterns of Hawaiian tiger sharks are a fascinating subject of study for scientists and laypeople alike. By continuing to study these magnificent creatures, we can better understand the complex interactions between predator and prey species in the ocean, and work to protect these important and iconic animals for generations to come.

References:

• Papastamatiou, Y. P., et al. "Telemetry and random walk models reveal complex patterns of partial migration in a large marine predator." Ecology 94.11 (2013): 2595-2606.

• Watanabe, Yusuke Y., et al. "Seasonal and ontogenetic changes in depth distribution

Happy World Reef Day & World Ocean Day! (June 1, 2023)

The world’s reef systems provide sustainable food items and medicines for both marine life and humans. They protect coastlines from storms and erosion, provide economic benefits to tour guides, fishers, and divers. Of course, they also hold a readily apparent beauty.

Taking swift action against pollution and bleaching to restore these systems became the goal of World Reef Awareness Day, June 1, in 2019.

June 1, 2023 was a warm, breezy day on O‘ahu’s North Shore, where the coconut palms of Pua‘ena Point provided shady canopy near its small, coarse beach and scattered tide pools. On this Thursday morning, One Ocean Conservation set up their booth, sorted rubbish bags, and provided gloves, bags, and tools—a beacon to like-minded folks who wished to make a small difference in conservation’s name.

The event took place a week before World Ocean Day, a campaign since its 1992 proposal to organize youth leaders, zoos, aquariums, museums, organizations, and businesses to create events, educate, and advocate for policy change.

The people of O‘ahu have a long tradition of World Ocean Day participation. During the 2021 campaign, Hawai‘i’s then-governor David Ige signed the Hawai‘i Shark Protection Act into law, banning all persons from intentionally or knowingly capturing, entangling, or killing any shark within state marine waters.

Hawai‘i is the first state in the nation to provide sharks with these essential protections, and needless to say the folks at One Ocean Conservation were loud and prominent voices in creating this change.

Half of those who answered One Ocean’s call on Thursday came with sunhats and screen, gloves, and shovels. The other half came equipped with masks, snorkels, fins, and knives. With crashing waves splitting reef from beach, volunteers took to their terrain accordingly.

While the walkway up to Pua‘ena was littered with cigarette butts and bottle caps, the crew was able to pull quite the haul from the area’s nooks, including paint cans, metal poles, glass bottles, beer cans, plastic odds and ends, fishing equipment, and more.

Similar scraps were found pinched in the reef itself—anything from line, hooks, and weights to scissors and other random scraps. Many honu perused the area with the divers (at least five were spotted just from the beach), revealing the unfortunate reality that it isn’t just the coral that gets hung up in this debris, but megafauna too.

The small but mighty crew left with fun giveaways like Freestyle watches, Cressi masks, and One Ocean bikinis as well as an equally small but mighty improvement to Pua‘ena and the surrounding area.

To get involved in One Ocean’s monthly beach and reef clean-ups or otherwise contribute to the healthiness of our ocean systems, stay up to date @oneoceanconservation on Instagram.

The Ecological Importance of Sharks

Sharks are often portrayed as fearsome predators, but they play a vital role in maintaining healthy marine ecosystems. As apex predators, sharks are at the top of the food chain and help to regulate the populations of other marine species.

One of the most important roles that sharks play in marine ecosystems is controlling the populations of other predators, such as smaller sharks and marine mammals. By preying on these animals, sharks help to prevent them from overexploiting their own prey species, which can have cascading effects on entire marine ecosystems.

Sharks also play a crucial role in regulating the populations of mesopredators, which are smaller predators that feed on smaller prey species. By controlling the populations of mesopredators, sharks help to prevent these species from becoming too abundant and causing imbalances in the ecosystem.

In addition to their role as predators, sharks also help to maintain healthy marine ecosystems through their role as scavengers. By feeding on dead and dying animals, sharks help to remove these carcasses from the ecosystem, which can help to prevent the spread of disease and other negative impacts on the ecosystem.

Sharks also play a role in nutrient cycling in marine ecosystems. By consuming prey species and excreting waste products, sharks help to recycle nutrients back into the ecosystem, which can help to support the growth of other marine organisms.

Finally, sharks play a crucial role in maintaining the health of coral reefs, which are one of the most important ecosystems in the world. By controlling the populations of herbivorous fish that graze on coral, sharks help to prevent these fish from overgrazing and damaging the coral. This, in turn, helps to maintain the structural integrity of the reef and the diverse ecosystem it supports.

In conclusion, sharks play a vital role in maintaining healthy marine ecosystems. As apex predators, they help to control the populations of other predators and mesopredators, regulate nutrient cycling, and maintain the health of important ecosystems such as coral reefs. By recognizing the ecological importance of sharks and working to protect them, we can help to ensure the long-term health of our oceans and the many species that rely on them.

References:

Ferretti, F., et al. "Ecological role of sharks in a changing world." Advances in Marine Biology 78 (2017): 201-257.

Heithaus, M. R., et al. "Top predators as ecological engineers: effects of mesopredator control on coral reef structural dynamics." Ecology 87.12 (2006): 3460-3468.

Worm, B., et al. "Global patterns of predator diversity in the open oceans." Science 309.5739 (2005): 1365-1369.