Mexican Sardine Run in Baja California: The Complete Guide

Last year, at 6:30 in the morning, we left Puerto San Carlos with the sun still hidden behind the dunes of Magdalena Island. We returned to port after sunset. We spent the entire day at sea, getting in and out of the water, and not once did anyone in the group ask to head back early.

That day ended with a Bryde’s whale cutting through a bait ball just a few metres away from us. But let me start at the beginning.

The Sardine Run in Magdalena Bay is, for me, one of the most intense wildlife encounters you can experience with just a mask and snorkel. In this guide, I’ll explain what the Mexican Sardine Run is, when and where it happens, the best time to go, why striped marlin gather here, how a bait ball works, and what it actually feels like to experience it from the water.

Quick answer: The Mexican Sardine Run takes place roughly between October and January off Magdalena Bay, on the Pacific coast of Baja California Sur. November and December usually fall within the main window of activity. Striped marlin hunt sardines, mackerel and other small pelagic fish, concentrating them into bait balls near the surface. California sea lions, dolphins and seabirds may join the hunt, and occasionally whales appear too. The experience is primarily done by snorkeling and ocean safari, not scuba diving. As with any wild-animal encounter, sightings are never guaranteed.

Is the Mexican Sardine Run the same as the South African Sardine Run?

No. They are different phenomena that share a popular name.

I know both well because at Mind the Seas we run expeditions in both Baja California Sur and South Africa.

The South African Sardine Run is associated with the seasonal movement of huge numbers of sardines (Sardinops sagax) along the eastern coast of South Africa.

The phenomenon we look for off Magdalena Bay is more localized and revolves around open-ocean feeding events, with striped marlin as one of its most characteristic predators.

When does the Mexican Sardine Run happen?

The window we use as a reference runs approximately from October to January, with November and December normally falling within the main period of activity.

In October, activity may only be starting to develop. By January, it can begin to lose intensity.

However, there is no exact date on which the Sardine Run starts or finishes each year.

Water temperature, ocean fronts, prey distribution and large-scale oceanographic conditions can all affect what we find from one season to the next.

Choosing a historically favorable period therefore increases your chances, but never guarantees an encounter.

Is November or December better for the Mexican Sardine Run?

Both months fall within the window we look for.

If I had to choose for an expedition combining the Sardine Run with other wildlife experiences across Baja California Sur, I would personally choose November.

Not because the ocean follows a calendar, but because November allows us to build an exceptionally complete journey between the Pacific Ocean and the Sea of Cortez.

That is why our Best of Baja expedition takes place in November.

Where does the Mexican Sardine Run happen? Magdalena Bay

Magdalena Bay lies on the Pacific coast of Baja California Sur.

Expeditions depart from places such as Puerto San Carlos or Puerto Adolfo López Mateos, and from there boats head out in search of activity. There is no single “Sardine Run spot” that you can simply navigate to every morning. That is precisely the challenge. You have to find it. Captains and guides look for seabirds, disturbances on the surface, groups of predators and other signs that may indicate feeding activity below.

Magdalena Bay is worth the journey in its own right. It is a vast lagoon system protected by barrier islands, with enormous dunes falling directly into the ocean and kilometres of mangroves on the inside.

Last year, as we were returning to port in the last light of the day, someone in the group pointed towards the crest of a dune. There was a coyote standing still, watching us pass. It was one of those moments that reminds you that here, the desert and the ocean literally meet.

Why do striped marlin gather in Magdalena Bay?

The productivity of Baja California’s Pacific coast is influenced by oceanographic processes such as upwelling, which can bring cold, nutrient-rich deep water towards the surface.

Those nutrients support plankton and, from there, an enormous marine food web.

The Magdalena Bay region is highly productive, and research conducted in these waters has documented seasonal concentrations of striped marlin feeding on sardines, mackerel, anchovies and other pelagic fish. The striped marlin (Kajikia audax) moves in response to favorable oceanographic conditions and prey availability. When large concentrations of prey develop off Magdalena Bay, the marlin find an extraordinary feeding opportunity. And when they hunt, something remarkable happens. Their stripes can intensify seconds before an attack.

Research published in Current Biology in 2024 documented rapid changes in the contrast of striped marlin body patterns during hunting. The stripes became more pronounced immediately before an attack and faded again afterwards.

Researchers proposed that these rapid colour changes could play a communication role during group hunting, although that function has not yet been conclusively demonstrated. Underwater, those stripes can become an almost fluorescent electric blue. It is one of the most beautiful things I have ever seen in the ocean, and no photograph really does it justice.

How does a bait ball work?

A bait ball forms when a school of small fish responds to predatory pressure by grouping together very tightly. From the outside, it can look like an enormous silver sphere turning in on itself. The marlin take advantage of that concentration.

Research on striped marlin hunting schooling fish in Baja California has observed several individuals maintaining positions around a school while one marlin performs a rapid attack. Another individual may then attack.

So although underwater it can look like a perfectly choreographed hunt, scientifically it is more accurate to describe it as group hunting with alternating individual attacks rather than assuming a complex cooperative strategy.

Seabirds attack from above. Sea lions may cut through the school. Other predators can join the hunt. The bait ball can move, split apart, disappear or form again. Experiencing the Sardine Run is therefore about constantly reading what is happening both above and below the surface.

What animals can you see during the Mexican Sardine Run?

The most characteristic predator is the striped marlin, alongside the schools of small pelagic fish that drive the entire phenomenon. But an ocean safari can bring much more.

You may encounter California sea lions, dolphins and several species of seabirds. Studies of these feeding aggregations have also documented interactions between marlin, sea lions and seabirds around concentrations of prey. And occasionally, whales appear.

Last year, it happened to us with a Bryde’s whale. We had been watching a bait ball with three marlin for a while when I noticed the sardines tightening even further and the marlin moving away. I lifted my head and saw a blow about fifty metres away. I put my face back underwater just in time to see an enormous shadow rising from below with its mouth open. It lasted seconds. When we surfaced, nobody spoke. Then everybody started talking at once.

What is it actually like to experience the Sardine Run?

A typical day starts early. The captain and guide search for clues: concentrations of seabirds, surface activity or movement that might indicate predators feeding below. The birds are one of the best radars you have out here.

Once activity is located, the boat approaches and the guide evaluates the situation before the group enters the water. Once you are in, the goal is not to chase the animals. It is to position yourself correctly and allow the action to happen around you. If the bait ball moves, you get back onto the boat, reposition and enter the water again. And that can happen many times throughout the day.

What I remember most from last year is the colour.

When clean oceanic water moves into Magdalena, the blue can be so intense that it feels like you are floating in the sky. Sunlight cuts through the surface, the sardines glitter like a ball of mirrors and there is no bottom beneath you.

Just blue.

That day, we ate lunch on the boat between bait balls and made our final entry with the sun already low over the horizon.

Can you scuba dive the Mexican Sardine Run?

Scuba diving is not the practical way to experience this phenomenon. It is mainly done by snorkeling.

Bait balls and predators can move quickly through the open ocean. To follow the action, you need to be able to enter and exit the boat and reposition repeatedly.

A mask, snorkel and fins give you that mobility.

You do not need to be a freediver.

But you should be comfortable swimming over deep water, repeatedly getting in and out of a small boat, and dealing with some swell.

Being able to make short freedives can help you enjoy the encounter even more, but it is not a requirement.

How many days do you need for the Mexican Sardine Run?

I would not travel all the way to Magdalena Bay to try it for a single day. Not because one day cannot be extraordinary, but because we are dealing with wild animals and ocean conditions that can change constantly. You can have an incredible day followed by a quiet one.

Or exactly the opposite.

That is why we prefer to dedicate several full ocean-safari days to searching for activity. The larger your window, the more opportunities you have to experience one of those days when everything comes together. If you are organizing the trip independently, I would plan for at least two or three days of searching, whenever your schedule and conditions allow.

Are striped marlin sightings guaranteed?

No.

These are wild animals in the open ocean, and no operator can control where wildlife will be on any particular day.

What we can control is when we travel, how much time we dedicate to searching, who we work with and how we respond to the conditions we find.

That is why we choose a historically favorable window, work with experienced local captains and dedicate several days to the phenomenon.

For wildlife expeditions, I think that distinction is fundamental:

maximizing opportunities does not mean guaranteeing encounters.

What is the water temperature during the Mexican Sardine Run?

In our experience during expeditions, we can encounter water temperatures of approximately 18–24°C (64–75°F) across the season, depending on the month and oceanographic conditions.

We use this as an operational reference rather than a guaranteed temperature range.

But water temperature is only part of the story.

You can spend many hours on a small boat, repeatedly getting in and out of the water and dealing with wind during longer crossings.

That is why we generally recommend a 5 mm wetsuit, or additional thermal protection if you get cold easily, as well as a windproof layer for the boat.

What should you bring?

You do not need technical equipment.

You need to be prepared to spend a lot of time searching.

Because a huge part of the Sardine Run is exactly that.

Waiting.

Watching.

And being ready when the ocean suddenly changes.

Is the Mexican Sardine Run suitable for beginners?

You do not need to be a certified scuba diver or freediver to experience the Sardine Run.

However, I would not consider it suitable for someone who is uncomfortable in the open ocean.

You may be far from shore, swimming over deep water, dealing with swell and making repeated entries and exits from the boat throughout the day.

The more comfortable you are swimming with a mask, snorkel and fins, the more attention you can give to what is happening in front of you.

How can you experience the Sardine Run responsibly?

The goal should be to observe a natural hunt without turning our own presence into another source of pressure around the bait ball.

We work with small groups and follow the instructions of local guides and captains.

In the water, we avoid chasing animals, deliberately swimming through bait balls or positioning ourselves in the path of hunting predators.

We also pay attention to what is happening around us.

If we believe the number of boats or people is putting too much pressure on a bait ball, we would rather move away.

The encounter should never happen at any cost.

What is the water temperature during mobula season?

During our spring expeditions around La Ventana, we generally experience increasingly warm water as the season progresses, although local conditions and upwelling can create considerable variation.

For planning purposes, we normally recommend a 3–5 mm wetsuit, with more thermal protection early in the season or for anyone who gets cold easily.

I would treat exact temperature ranges as operational observations rather than guarantees.

Ocean conditions can change quickly here.

How we experience the Sardine Run at Mind the Seas

The Sardine Run is the crown jewel of our Best of Baja expedition.

But we do not travel all the way to Baja California Sur for a single phenomenon.

We combine several full days searching for the Sardine Run in the Pacific with the Sea of Cortez and some of the encounters that make this region so extraordinary.

It is precisely that combination of two seas that interests us.

We travel in small groups, work with local captains and design our itineraries around spending meaningful time searching for wildlife rather than trying to force wild encounters into rigid schedules.

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My personal take

If I could choose only one wildlife experience in Baja California Sur, it would be this one.

Not because of the adrenaline.

Because of the feeling of being inside something that would be happening exactly the same way if you were not there.

A bait ball does not exist for you to photograph it. The marlin is not hunting for you. The whale has no idea you have spent years waiting to see it.

You were simply lucky enough to arrive at the right moment.

The best thing you can do is come with patience, warm clothes for the boat and no fixed expectations.

The waters of Magdalena always find a way to surprise you.

Scientific sources and further reading

In addition to our own experience in the field, the information on striped marlin hunting behaviour, feeding aggregations and the comparison with South Africa is supported by peer-reviewed scientific literature:

Herbert-Read et al. — Mechanisms of prey division in striped marlin, a marine group hunting predator. Communications Biology (2022).
Research examining striped marlin hunting schooling prey in Baja California and how individuals alternate attacks during group hunting.

Herbert-Read et al. — Rapid color change in a group-hunting pelagic predator attacking schooling prey. Current Biology (2024).
Research documenting how the contrast of striped marlin body patterns increases immediately before an attack and decreases afterwards.

Research on striped marlin and California sea lion feeding aggregations off Magdalena Bay.
Research documenting the productivity of the region and the involvement of different predators around concentrations of pelagic prey.

Teske et al. — The sardine run in southeastern Africa is a mass migration into an ecological trap. Science Advances (2021).
A useful reference for understanding the dynamics of the South African Sardine Run and why it should not be considered the same phenomenon as the feeding events off Magdalena Bay.