Red Tide In Southern California

Red Tide in Southern California: 2021

Normal red tides that occur here in San Diego tend to last only 1-2 weeks and the concentration is usually minimal. Sometimes, it remains offshore and dies off before it can even reach the crashing waves in high density. The red tide that took place in 2020 was one of the longest-lasting and densest red tides San Doiego has ever experienced.

While much of the general population is attracted to this phenomenon, the red tide of 2020 was most definitely detrimental to the marine ecosystem. In more stagnant areas up and down our coastline, carcasses were washing up and many animals died. But, it’s all part of nature’s course and in the end, we pulled through with a burst of seafoam to clean the waters.

Red Tide

What is a red tide?

You’ve likely heard about or seen some of the spectacular events like glowing waves and even glowing dolphins! It really is a spectacular sight to see, but what is a red tide?

A red tide is caused by an excessive amount of phytoplankton in high concentrations within the ocean waters (1). Commonly referred to as a “bloom”, this phenomenon takes place all around the world with California just being one of many places. Phytoplankton (single-celled) are technically classified as a type of algae. So when you hear the term “algae bloom”, this is why (2).

The red tides that Southern California typically experiencines are caused by a specific type of phytoplankton called Lingulodinium polyedra also referred to as L. Poly. L. Poly is the usual offender when it comes to determining the root of an algae bloom on the west coast.


Before you get too freaked out, it’s worth mentioning that the red tides that occur in Southern California usually don’t pose a significant direct threat to the marine ecosystem and pose minimal threat to human health in the event of consumption. But, it certainly can. In places like Florida, red tides have the potential to wipe out thousands and thousands of marine animals. Luckily, Southern California usually isn’t at any such risk.

It’s important to note that L. Poly can produce yessotoxin which can build up in crustaceans causing health risks all around (3). A basic understanding of the danger is the concept of sand crabs as a food source for common surf species. Phytoplakton are the basic food source for the animals of the sea. As we move up the food chain from plankton, to sand crabs, fish, and eventually to birds of prey and even humans.

Why do the waves glow?

Perhaps the most mysterious aspect of the red tide, “why do the waves glow?” can be answered in very simple terms. The answer is bioluminescence. More specifically, bioluminescence upon agitation. These specific phytoplankton produce bioluminescent light when they are so called “agitated”. Meaning that when a wave crashes, or a fish or dolphin breaks the surface of the water, the phytoplankton are thrown about and will produce their “glow” causing the waves to appear as so.

Depending at which beach or bay you find yourself, you may even be able to see your footprints begin to glow. This will be determined by how close the phytoplankton have come to shore.

When do red tides occur?

The “when” and the “why” are closely related (at least for the reason it occurs on the West Coast). The phytoplankton, L. Poly thrives upon the transition to warmer waters, as is the case with many different types of algae. The 2020 red tide occurred just after our water temps rose by 2-3 degrees in a very short period of time.

Given this information, red tides in So Cal can usually be seen as a good sign for surf anglers. It shows that the waters are warming and that peak season surf fishing is just around the corner. Usually, as the waters warm, species like the California Corbina, Spotfin Croaker, Leopard Shark, and other common species begin to repopulate the shallows along Southern California’s beaches.

What happened in the 2020 red tide?
leopard shark
June 3, 2019: I believe leopard sharks may be arriving in numbers much earlier this year.

Warming Waters

According to Surfline, the water temperature in La Jolla jumped from 60 degrees to a “61-63 degree range”. According to Magic Seawead, the water temperature has jumped from 61 to 65 degrees! This was in a span of about two weeks!

In my experience, the 64 degree mark is the metaphorical “hump”. So when the water hits 64, potential for every surf species of fish and shark in Southern California increases dramatically. And when the temp rises over and above the hump, we’re in full summertime surf slaying mode. That being said, you may want to check out some recommended rods and reels for the upcoming season.

bat ray
90 lb Bat Ray
Summertime Bite

Now, whether we’re at 63 degrees or 65 (or somewhere in between), there is no denying that the water is warming. The last few days have been scorching here in So Cal, and the trend is set to continue for at least the next week and a half. What does this mean? I think the next couple weeks could signify the beginnings of the summertime bite.

While May is still a little early for full-blown summertime surf fishing, the extreme heat we’re experiencing should certainly result in more Corbina, Croaker, Guitarfish, and even Leopard Sharks!

Here’s the gear and tackle I like to use for big fish in So Cal:


(1) Langlois, G. (n.d.). Red Tides in California. Retrieved from

(2) Fondriest Environmental, Inc. “Algae, Phytoplankton and Chlorophyll.” Fundamentals of Environmental Measurements. 22 Oct. 2014. Web. <>.

(3) Paz, B., Daranas, A. H., Norte, M., Riobó, P., Franco, J. M., & Fernández, J. J. (2008, May 7). Yessotoxins, a group of marine polyether toxins: an overview. Retrieved from


Leave a Reply