Toxic Algae Bloom in San Diego: Surf Fishing and Seafood Safety

A toxic algae bloom is currently impacting the San Diego coastline, raising serious concerns for marine life, beachgoers, and the local fishing community. This bloom is caused by a microscopic algae called Pseudo-nitzschia, which produces a potent neurotoxin known as domoic acid. When conditions are just right—like warmer ocean temperatures and an abundance of nutrients—this algae can multiply rapidly, creating harmful blooms that pose serious ecological and public health risks.

In recent weeks, the effects have become painfully visible. Sea lions and pelicans have been found disoriented, sick, or dead along San Diego’s beaches, likely due to domoic acid poisoning. The toxin works its way through the food chain, accumulating in fish and shellfish, which in turn affects the predators that eat them. Even some fish species may be impacted by the shifting ecosystem and toxin exposure.

In this article, we’ll dive into what this toxic bloom means for surf fishing—how it’s affecting the bite, whether it’s still safe to fish, and if it’s safe to keep your catch for eating.

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What Are Harmful Algal Blooms (HABs)?

Harmful algal blooms, often referred to as HABs, occur when colonies of algae—simple plants that live in the sea and freshwater—grow out of control and produce toxic or otherwise harmful effects on people, marine life, and coastal environments. Not all algal blooms are dangerous, but when certain species proliferate, they can release potent toxins, deplete oxygen levels in the water, and disrupt entire marine ecosystems.

HABs form under a combination of favorable environmental conditions. Rising ocean temperatures—often driven by seasonal changes, El Niño events, or long-term climate trends—are a major trigger. Nutrient runoff from agricultural areas and urban stormwater, rich in nitrogen and phosphorus, can also supercharge algae growth. Additionally, upwelling events—where deep, nutrient-rich water is pulled to the surface—can bring a sudden influx of nutrients that fuel blooms.

One particular group of algae, Pseudo-nitzschia, is especially concerning. This genus of diatoms is naturally present in many coastal waters, but under certain conditions it can rapidly multiply and produce domoic acid, a powerful neurotoxin. Domoic acid accumulates in filter-feeding organisms like anchovies, sardines, and shellfish, and then moves up the food chain, affecting birds, marine mammals, and potentially humans.

In the current San Diego bloom, Pseudo-nitzschia is the primary culprit, with high levels of domoic acid being detected along the coast. This not only endangers wildlife but also raises important questions about seafood safety and the broader impacts on local ecosystems—including the surf fishing experience.

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Impact on Marine Life

The ongoing toxic algae bloom off the coast of San Diego is having a devastating impact on local marine wildlife. Sea lions, dolphins, and seabirds have been found stranded along beaches in increasing numbers, many exhibiting symptoms of domoic acid poisoning. These symptoms include disorientation, confusion, seizures, and in severe cases, death. Wildlife rescue centers throughout San Diego County have reported a surge in calls and intakes related to domoic acid toxicity, overwhelming resources and staff.

SeaWorld San Diego’s Rescue Team and the SeaWorld & Busch Gardens Conservation Fund have been actively responding to these events, rescuing dozens of affected sea lions and seabirds. According to CBS8, the San Diego Humane Society’s Project Wildlife program has also seen an uptick in seabirds suffering from domoic acid poisoning, particularly brown pelicans.

This neurotoxin, produced by Pseudo-nitzschia algae during harmful algal blooms, enters the food chain at the lowest levels—typically in plankton-feeding fish like anchovies and sardines. These small forage fish accumulate domoic acid in their tissues without showing symptoms themselves. However, when predators such as sea lions, dolphins, or seabirds consume large quantities of these contaminated fish, the toxin builds up in their systems—a process known as biomagnification. Because domoic acid affects the brain, these animals often exhibit neurological distress, which can be fatal if not treated quickly.

The current bloom is a stark reminder of how interconnected ocean life is—and how a microscopic organism can trigger a chain reaction that ripples through the entire coastal ecosystem.

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Public Safety Concerns

The toxic algae bloom currently affecting San Diego’s coastline isn’t just a threat to marine wildlife—it also poses safety concerns for the public, especially for beachgoers, anglers, and anyone spending time near the ocean.

Disoriented or sick marine animals, particularly sea lions, have been observed behaving erratically on beaches and in shallow waters. Some have become unusually aggressive or confused due to the neurotoxic effects of domoic acid. There have been multiple reports of beachgoers encountering sea lions acting unpredictably, including animals that appear lethargic one moment and suddenly lunge or bark aggressively the next.

For your safety and the safety of the animals, it’s critical to keep a safe distance if you see a marine mammal acting strangely—this includes sea lions, seals, dolphins, or seabirds. Do not attempt to feed, touch, or assist the animal yourself. Instead, contact a local wildlife rescue organization. In San Diego, the San Diego Humane Society’s Project Wildlife program and SeaWorld San Diego’s Rescue Team are among the groups actively responding to such incidents.

To report a stranded or distressed marine animal in San Diego County:

• Call SeaWorld’s Rescue Hotline at (800) 541-SEAL.
• Or contact the San Diego Humane Society’s Wildlife Department at (619) 299-7012.

Public awareness efforts are ongoing, with organizations urging residents and visitors to be cautious and informed. Beaches may post warning signs or provide guidance if unusual wildlife activity is observed. By staying alert and informed, you can help ensure both your safety and the wellbeing of San Diego’s marine animals during this challenging event.

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Is It Safe to Eat Fish Caught During an Algae Bloom?

Consuming fish caught during a toxic algae bloom poses significant health risks due to the presence of domoic acid, a potent neurotoxin produced by certain algal species. This toxin can accumulate in various marine organisms, including those commonly targeted by surf anglers, such as surfperch, corbina, halibut, and croaker.​

Understanding Domoic Acid Accumulation

Domoic acid is produced by harmful algal blooms (HABs) involving species like Pseudo-nitzschia. This toxin enters the marine food web when filter-feeding organisms, (anchovies, sardines, shellfish, sand crabs, etc.) consume the algae. Predatory fish that feed on these smaller fish can then accumulate domoic acid in their tissues. Importantly, domoic acid is heat-stable, meaning that cooking does not eliminate the toxin from contaminated seafood .​UCSC News+2MDPI+2Marine Mammal Center+2

Risks Associated with Common Surf Catches

While bivalve shellfish like mussels and clams are often the focus of domoic acid advisories, finfish such as surfperch, corbina, halibut, and croaker can also pose risks. These species may accumulate domoic acid by consuming contaminated prey. The California Department of Public Health (CDPH) monitors toxin levels and issues advisories when necessary. For instance, recent advisories have warned against consuming certain shellfish due to elevated domoic acid levels .​KSBY News+1CDPH+1WDFW+1CDPH+1CDPH+5California Fish and Wildlife+5NOAA+5

Recommendations for Surf Anglers

• Stay Informed: Regularly check for updates from the CDPH and the Office of Environmental Health Hazard Assessment (OEHHA) regarding seafood safety advisories.​
• Be Cautious with Filter Feeders: Avoid consuming filter-feeding species during or shortly after algal blooms, as they are more likely to accumulate domoic acid.​
• Observe Fish Behavior: Discard any fish that exhibit unusual behavior or signs of illness, such as disorientation or lethargy.​
• Consider Catch-and-Release: During active algal blooms, it may be safer to practice catch-and-release fishing to minimize health risks.​

By staying informed and exercising caution, surf anglers can enjoy their activities while safeguarding their health and that of others.

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Connection to Red Tides

Toxic algae blooms and red tides are closely related phenomena—both fall under the umbrella of harmful algal blooms (HABs)—but they’re not always caused by the same species, nor do they have identical effects on the marine environment.

Red Tides vs. Toxic Algae Blooms

Red tides in Southern California are most commonly caused by blooms of Lingulodinium polyedra. These events often discolor the water, sometimes turning it a deep rust color, and are known for creating dramatic, bioluminescent waves at night. Red tides can produce toxins that affect marine life and can even cause respiratory irritation in humans when onshore winds blow aerosolized toxins inland.

Toxic algae blooms, like the one currently affecting San Diego, are typically caused by Pseudo-nitzschia, a type of diatom that doesn’t usually discolor the water. What makes Pseudo-nitzschia especially dangerous is its production of domoic acid, a neurotoxin that accumulates in the food chain and can cause severe illness or death in marine animals and potentially in humans who consume contaminated seafood.

Similarities and Shared Conditions

Despite their differences, both types of blooms often arise from the same environmental triggers:

• Warming ocean temperatures
• Nutrient runoff from land (e.g., fertilizers, stormwater)
• Seasonal upwelling that brings nutrient-rich waters to the surface

Both types of HABs can result in significant ecological disruption, including fish kills, disoriented marine mammals, and massive seabird strandings.

Learn More

To better understand how climate change and warming waters are increasing the frequency and intensity of red tides in Southern California, check out our article:
👉 Red Tide and Warming Waters

And if you’ve ever wondered about the strange, foamy residue that sometimes accompanies these blooms, we dive into that in this piece:
👉 Sea Foam and the Red Tide

Understanding the link between red tides and toxic algae blooms helps paint a clearer picture of the evolving challenges facing our coastal waters—and what that means for marine life, surf anglers, and beachgoers alike.

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How Do Red Tides and Toxic Algae Blooms Affect Surf Fishing?

For surf anglers, harmful algal blooms—whether caused by red tides or toxic algae like Pseudo-nitzschia—can significantly influence fishing conditions, sometimes in unexpected ways.

Potential Short-Term Upsides

An argument could be made that there could be brief windows of opportunity during these events. Sick or disoriented baitfish, such as anchovies and sardines affected by domoic acid, may become easy targets for predators. This can draw in larger species like halibut, leopard sharks, or even big surfperch, which sometimes take advantage of the struggling forage. In the right place and time, these conditions can create a short-lived feeding frenzy nearshore.

But these opportunities are rare and unpredictable, and the risks and downsides usually outweigh any short-term gains.

The Downsides for Anglers

More often, algal blooms cause a noticeable decline in fishing quality:

• Reduced water clarity from red tide discoloration or algae concentration can make lures and bait harder for fish to see.
• Low oxygen levels associated with some blooms can cause fish to become sluggish or vacate the area altogether.
• Foul smells and foamy surf are common signs that conditions have turned poor, which typically leads to soft bites—or no bites at all.

What to Watch For

If you notice:

• Reddish-brown or murky water
• Unusual amounts of sea foam
• Rotten or chemical-like odors
• Dead or dying fish or seabirds onshore

…it’s a good indicator that a bloom may be affecting your area. These are times when it’s not only tough to get bites, but possibly unsafe to be in or around the water—especially if you’re considering keeping your catch.

When to Fish—and When to Stay Off the Beach

The best advice during an active bloom? Err on the side of caution. If you suspect a bloom is underway:

• Stick to catch-and-release only, especially for filter feeders or fish likely to consume affected bait species.
• Avoid fishing in discolored or foamy water, and skip the session entirely if local authorities have issued advisories.
• Pay attention to wildlife behavior—confused sea lions or stranded birds are often a telltale sign something’s off.

When the bloom clears and water clarity improves, fishing usually rebounds quickly. Just be patient, stay safe, and keep an eye on the signs.

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Final Thoughts: Surf Fishing Through a Toxic Bloom

The toxic algae bloom currently impacting San Diego’s coastline is a sobering reminder of how fragile and interconnected our coastal ecosystems really are. From the smallest plankton to the largest sea lions, no creature is left untouched when environmental conditions tip into imbalance.

Domoic acid doesn’t just harm marine life—it can affect people too. So as anglers, we need to fish smart: stay updated on health advisories, avoid harvesting questionable catches, and consider practicing catch-and-release during active blooms.

As ocean temperatures continue to rise and nutrient runoff remains a challenge, harmful algal blooms like this one may become more frequent. But by understanding what’s happening and adapting our practices, we can continue to enjoy the sport we love while helping protect the waters that make it possible.

Stay safe out there, respect the ecosystem, and tight lines—even in tough conditions.