Leopard Sharks in San Francisco Bay

Leopard sharks are one of the most common shark species in the San Francisco Bay. They are year-round residents, but around 10% of the population moves out into coastal waters in the fall and winter. Leopard sharks are shallow-water coastal species with a range extending from southern Oregon to southern Baja California. They are generally harmless to humans and can be observed by divers and snorkelers in the bay.

Despite the urban landscape surrounding the bay, the shark populations remain healthy. Leopard sharks have found a new haven in the San Francisco Bay, where they are abundant and thriving. The bay is also home to other shark species such as the sevengill shark, Pacific angel shark, brown smoothhound, and soupfin shark. These sharks play an important role in the bay’s ecosystem and are a testament to the resilience of nature in the face of urbanization.

Leopard Sharks in San Francisco Bay

Habitat and Distribution

Leopard sharks are commonly found in the San Francisco Bay and are the most abundant shark species in the area. They are shallow-water coastal species and can be found from southern Oregon to southern Baja California. The leopard sharks in San Francisco Bay are usually year-round residents, but about 10 percent of the population moves out into coastal waters in the fall and winter.

Physical Characteristics

Leopard sharks are easily identifiable by their distinctive pattern of black spots and saddle-like markings. They have a streamlined body and can grow up to 7 feet in length. They are not considered dangerous to humans and are often sought after by recreational fishermen.

Behavior and Diet

Leopard sharks are bottom-dwellers and are often found in shallow waters near the shore. They are known to form large schools during the summer months and are often seen basking in the sun near the surface of the water. Leopard sharks are opportunistic feeders and their diet consists of a variety of prey including fish, crustaceans, and mollusks.

In the San Francisco Bay, leopard sharks have predators such as sea lions and the Bay’s largest species, sevengill sharks. Sevengill sharks are named for the seven sets of gills on each side of their body. They are black and gray, grow as long as 10 feet, and can weigh over 300 pounds.

Leopard shark populations in the San Francisco Bay have been studied extensively due to their abundance and accessibility. They are an important part of the Bay’s ecosystem and provide valuable information for researchers and conservationists.

Threats to Leopard Sharks

Leopard sharks are facing several threats in the San Francisco Bay, including toxins, die-offs, infection, mercury, predators, parasites, heavy metals, and pesticides.

The Bay’s toxic pollution is one of the primary threats to leopard sharks. The high levels of toxins in the water can cause serious health issues and even death. These toxins can enter the sharks’ bodies through their gills and skin, leading to various health problems.

Another significant threat to leopard sharks is die-offs. Scientists have documented massive leopard shark die-offs in the San Francisco Bay for the past few years. The die-offs appear to be centered around Redwood City in San Mateo County. Biologists are trying to identify the reasons for this massive die-off.

Infection is another threat to leopard sharks. A California Fish and Wildlife pathologist has identified a microbial pathogen that he thinks is responsible for killing thousands of sharks and rays in the San Francisco Bay between February and April 2023. The pathogen is a protozoan parasite that can cause severe infections in sharks.

Heavy metals and pesticides are also posing a threat to leopard sharks. These pollutants can accumulate in the sharks’ bodies and cause various health problems, including reproductive issues and behavioral changes.

Predators are also a significant threat to leopard sharks. Larger sharks, such as great white sharks, can prey on leopard sharks. Additionally, sea lions and harbor seals can also prey on juvenile leopard sharks.

Finally, a parasite called Miamiensis avidus is a significant threat to leopard sharks in the San Francisco Bay. This parasite killed large numbers of Bay leopard sharks in 2011, 2017, and 2019, after rainier-than-usual winters when leopard sharks migrated to the Bay’s shallow waters to mate and give birth.

Overall, leopard sharks in the San Francisco Bay face many threats, and it is crucial to identify and address these threats to ensure the survival of this species.

Die-Offs and Infections

Leopard sharks in San Francisco Bay have been experiencing die-offs and infections for several years. Researchers from the California Department of Fish and Wildlife have been investigating the cause of these die-offs, which have been occurring in increasing numbers since 2011.

Fish pathologist Mark Okihiro has been studying the brains of dead leopard sharks to determine the cause of the die-offs. He has found that many of the sharks have a brain infection caused by a microscopic organism called Miamiensis avidus. This fungal pathogen can cause inflammation in the cerebrospinal fluid, leading to neurological symptoms and eventually death.

Stagnant water in the bay may be contributing to the spread of the infection. Health authorities have warned people to avoid swimming in stagnant water and to wash their hands thoroughly after handling dead fish.

While the cause of the die-offs has been identified, there is still much to learn about how to prevent them from occurring in the future. Researchers are continuing to study the effects of Miamiensis avidus on leopard sharks and other marine life in San Francisco Bay.

Research and Conservation Efforts

Efforts to study and conserve leopard sharks in San Francisco Bay have been ongoing for several years. The Pelagic Shark Research Foundation (PSRF) has been conducting research on the shark populations in the bay since 1990. They have been studying the movements, behavior, and ecology of these sharks to better understand their role in the ecosystem.

In recent years, there has been concern over the decline in leopard shark populations in the bay. The PSRF, along with other organizations, has been working on conservation efforts to protect these sharks. One such effort has been focused on reducing the number of shark strandings in the bay. Sean Van Sommeran, the executive director of the PSRF, has been working on this effort by responding to shark strandings and working to release them back into the bay.

In addition to conservation efforts, research has also been conducted on the causes of shark die-offs in the bay. A study conducted by Nicholas I. found that the increase in fishing pressure on shark populations in California has been a major cause of concern. Protective measures for leopard sharks might have been too little too late, as the species is vulnerable to outside pressures.

Despite these challenges, there is hope for the future of leopard sharks in San Francisco Bay. Abundant populations of these sharks have been found in the bay, and efforts are being made to protect them. The PSRF, along with other organizations, will continue to conduct research and conservation efforts to ensure the survival of these important sharks in the bay ecosystem.

Leopard Sharks and Other Species

Leopard sharks are the most common shark species found in the San Francisco Bay. They are year-round residents, with some individuals moving out into coastal waters during the fall and winter months. These sharks are typically found in shallow waters of bays and estuaries, and nearshore in both kelp forest and sandy environments, usually staying near the bottom. They are rarely found in water deeper than 65 feet.

Other shark species found in the San Francisco Bay include the broadnose sevengill, soupfin shark, and spiny dogfish. The broadnose sevengill is the largest shark species in the Bay, growing up to 10 feet long and weighing over 300 pounds. The soupfin shark is a migratory species that can be found in the Bay during the summer months. The spiny dogfish is a small shark species that is commonly found swimming on the bottom of the Bay.

In addition to sharks, the San Francisco Bay is home to a variety of other fish species, including the white seabass, striped bass, and salmon. The Bay is also a primary nursery ground for bat rays and thornback rays. These rays are typically found in shallow waters and can grow up to 3 feet in diameter.

Great white sharks are occasionally spotted in the Bay, but they are not common residents. Other shark species that have been observed in the Bay include the basking shark, thresher sharks, and the rare and elusive salmon shark.

The San Francisco Bay is also home to the Pacific angel shark, a species of shark that is well-camouflaged and typically found on sandy or muddy bottoms. This shark species is not aggressive and is known to bury itself in the sand to avoid detection.

Overall, the San Francisco Bay is a diverse and dynamic ecosystem that supports a variety of shark and fish species. While some shark species may pose a risk to humans, they are an important part of the Bay’s ecosystem and should be respected and protected.

Public Awareness and Education

Public awareness and education are essential for the conservation and protection of leopard sharks in San Francisco Bay. Efforts to educate the public about the importance of these sharks in the marine ecosystem can help reduce human impact on their populations.

One way to increase public awareness is through organized events such as Sharktober, an annual celebration of sharks that takes place in October in the Bay Area. The event features educational programs, shark-themed activities, and guided shark tours, providing an opportunity for people to learn about leopard sharks and their role in the ecosystem.

Bay Nature, a local publication focused on the natural history of the San Francisco Bay Area, also plays a crucial role in educating the public about leopard sharks. Articles and features on leopard sharks in the magazine help to inform readers about the biology, behavior, and conservation status of these sharks.

In addition to public events and media, individual efforts can also make a difference in raising awareness about leopard sharks. For example, Ron Russo, a local photographer, has taken stunning photos of leopard sharks in their natural habitat, which have been widely shared on social media. These photos help to showcase the beauty and importance of these sharks to a wider audience.

Overall, public awareness and education are critical for the conservation of leopard sharks in San Francisco Bay. By increasing knowledge and understanding of these sharks, we can work towards protecting their populations and ensuring a healthy marine ecosystem for future generations.


Leopard sharks are an abundant and important species in the San Francisco Bay, serving as a key component of the local food web. However, their presence in the Bay also poses potential risks to human health due to the accumulation of toxins in their bodies from consuming contaminated sediment.

Efforts to restore the Bay’s salt-water estuary and wetlands could have a positive impact on the health of the local marine ecosystem, including the leopard shark population. Additionally, measures to reduce pollution and contaminants in the Bay could help mitigate the risks associated with consuming leopard sharks.

While leopard sharks are generally year-round residents of the San Francisco Bay, approximately 10% of the population moves out into coastal waters in the fall and winter. These sharks may travel as far north as Southern Oregon and as far south as Baja California along the Pacific coast.

The Bay’s leopard shark population also interacts with other local species, including sea lions, which have been known to prey on juvenile sharks. Leopard sharks have unique adaptations, such as gill slits that allow them to breathe while resting on the seafloor, and they are also commonly raised in hatcheries for research and conservation purposes.

Overall, leopard sharks are a fascinating and important species in the San Francisco Bay ecosystem, and continued efforts to monitor and protect their population are crucial for maintaining a healthy and balanced marine environment.