Sardine Run and the Interaction of Predators

Time to read
15 minutes
Read so far

Sardine Run and the Interaction of Predators

January 13, 2020 - 13:34

This natural spectacle takes place almost every year on the eastern coasts of South Africa and Mozambique—the so-called “Sardine Run.” To this day, the reason why it occurs cannot be precisely defined. There are various scientific theories, but some of them contradict each other. Factors involved in this, the world’s largest migration of South African sardines (Sardinops ocellatus), include the two major ocean currents—the Agulhas and the Benguela—plus wind speed and rain as well as air and water temperatures.

Contributed by

Tags & Taxonomy

Factfile

The gossip press said: “Diver Swallowed by Whale”
— Here's what really happened…

The story of how a diver was swallowed by a whale at Sardine Run showed up in all the media—worldwide. However, I was there, and I can tell you, no, the diver was not swallowed! And, no, we could not see the whale coming. And, yes, all precautions had been taken—and, no, it was not intended!

To read the whole story, scroll down...

In some years, however, the Sardine Run is not observed. During these years, it was thought that the Sardine Run did not take place due to climatic conditions. But just because one cannot see it on the surface does not mean that the sardines are not migrating. It is quite possible that this migration then takes place at greater depths and/or farther away from the coast.

“Normal case” scenario

Here is a rough summary of what happens during a normal year: The Agulhas Current brings warm water from the Indian Ocean along the eastern coast of Africa. The Benguela Current, which pushes cold water northwards from the Antarctic to the Cape, is averted by the warm water of the Agulhas Current at the Cape and thus flows along the western coast of South Africa. Towards the end of the summer in the Southern Hemisphere, the speed and strength of the Agulhas Current decreases. This gives the Benguela Current the opportunity to transport cold water in a narrow strip along the continental shelf on the eastern coast of Africa to the KwaZulu-Natal coast and to push off the Agulhas Current. The sardines, which prefer the colder water, follow this cold and nutritious current in huge masses to the KwaZulu-Natal coast and Mozambique.

These swarms of sardines can be several kilometres long and are clearly visible from an airplane as long as they are not too deep below the surface of the water. Such a large source of prey attracts a huge number of predators, which benefit from this wealth of food. These predators include dolphins, whales, sharks, seals, penguins and various seabird species such as Cape gannets and Cape cormorants.

However, depending on environmental factors, there are different variants in the Sardine Run’s usual scenario. Researchers who observe this natural event can therefore only make limited scientific statements about it. Years of studies at several locations would have to be carried out simultaneously to get a better overview. And what happens at greater depths in the water column is sometimes hidden from the viewer.

Migration timeline and characteristics

When we speak of the Sardine Run, we are mostly referring to the events that take place off the KwaZulu-Natal coast from June to July. But that is actually the end of this animal migration. The sardines begin to move towards the KwaZulu-Natal coast and Mozambique in January, beginning at the Cape and passing along the entire southeastern coast. Already in January, one can see the sardines in the region around the Cape and False Bay; from February to May, they are in the region of Algoa Bay and Coffee Bay; and only from May to July are they off the KwaZulu-Natal coast. Sardine spawning has also been observed in the water, which has led scientists to believe that the main objective of the Sardine Run is probably only sardine reproduction, because not all sardines take part in the migration.

The predators

Long-beaked common dolphins (Delphinus capensis) make up the largest number of predators. These dolphins reach a maximum length of 2.5m and are very agile, which gives them a big advantage in the Sardine Run. Bottlenose dolphins are rarely observed, and resident groups do not participate here; however, bottlenose dolphins passing by can sometimes be found at bait balls.

In the early months of the year, Bryde’s whales (Balaenoptera brydei) are the largest predators in the southern coastal regions. Occasionally, one can also find the somewhat smaller Antarctic minke whales (Balaenoptera bonaerensis).

From June to July, humpback whales (Megaptera novaeangliae) and southern right whales (Eubalaena australis) are present in the northern coastal areas. But the humpback whales are on a completely different migration, namely towards warmer waters, where they will mate and give birth to their calves. But when the opportunity arises, the sardines are a nice find for them.

Three shark species can also be found in the Sardine Run: copper sharks, mako sharks and dusky sharks. Great white sharks can also be spotted; however, they are not interested in the sardines, but in the dolphins and seals.

Sometimes, small groups of orcas appear, usually during a full moon phase. How these two things are related is still unclear. Orcas also only come because of the dolphins. It has been observed though, how orcas hunt the dolphins by isolating individuals from their pods. Other marine mammals that prey on the sardines include Cape fur seals, which only appear in small groups near bait balls, shooting through the swarm with great speed and underwater acrobatics.

As for seabirds, Cape gannets and Cape cormorants should be mentioned first among the avian predators. While a larger variety of seabirds can be observed at the sardine swarms, the large brown boobies and Cape cormorants are the predominant species represented.

The sardines themselves measure approximately 25 to 30cm in length. They are too big and too heavy for smaller seabirds to catch, since the birds would then have to fly several kilometres back to their young with the prey. This leaves the sardines almost exclusively reserved for large birds. Gannets are able to dive down to 15m to catch the sardines.

The African penguin (Spheniscus demersus)—also known as the “jackass penguin” because of its donkey-like cry—also takes part. They can reach a speed of 25km/h underwater. Unfortunately, they are now endangered as a species. One hundred years ago, their eggs were sold as a delicacy, and their manure was removed from the islands and shipped to England. The nests of the penguin colonies on St. Croix Island were completely destroyed. Today, there are several stations on the South African coast that take care of injured penguins.

Observing the Sardine Run

And now a bit about the adventure: It is pure madness for the observer—a feeding frenzy! You go out on a rubber boat for a few kilometres and you do not see much at first—sometimes even nothing—perhaps just a few birds flying somewhere or waiting on the surface of the water. It may be quite disappointing at first, but it is actually a good sign. Because when nothing is going on, the event is at this point probably concentrated somewhere else. And now it is time to follow the signs and find this place!

The gannets and cormorants are a good indicator. Are they still sitting on the water in groups or are they flying in a certain direction? And is there dolphin activity somewhere on the water’s surface? It is hard to see when the waves are coming at you. From the boat, you can see for about 3km. It means looking out on all sides and identifying and interpreting the variations on the water’s surface. The search can sometimes take several hours!

The adventure begins when you see all the gannets flying in the same direction in large numbers. Now it starts, because this means that the dolphins have started to drive the sardines. It is the long-beaked common dolphins that come together, coordinated from all directions to drive and hunt the huge swarm of sardines.

We were able to follow a pod of approximately 100 to 200 dolphins, which were heading towards the open sea at a rapid pace, followed by seabirds that plunged into the water again and again, catching individual fish. And more and more dolphins came from all directions—all in all, about 1,000 dolphins were involved in the chase, swimming at great speeds even farther out in open sea.

The water seemed to be boiling. The dolphins appeared in waves to breathe at the surface and thus generated their own waves. Some jumped out of the water, but most saved their energy for spurts of speed. Dolphin babies stayed close to their mothers’ sides, which were now in dire need of food. The group stayed close together; it was easier for these dolphins to keep up their speed by swimming in the wake of other dolphins. The dolphins coordinated their movements with whistling sounds underwater—a remarkable communication system that worked for miles underwater, thus reaching all the dolphins in the area.

Our boat positioned itself several times in front of the dolphins and we snorkelled in the middle of the stream of dolphins for a few minutes. The dolphins shot past—beside us, below us, all around us! They did not have time to really notice us; foraging was their priority. With just a quick glance at us, the marine mammals moved on at breath-taking speed. The sardines were still too deep—only individual fish that got lost had no chance of survival with all the predators on the hunt in the area.

It was almost impossible to take photos at the speed of the animals, especially because we were in a cold current with a lot of plankton. Nevertheless, the experience was indescribable! At approximately 45km from the coast, we unfortunately had to stop the pursuit; the way back would be against the wind and the waves were high. The dolphins raced towards the open sea at an insane pace—always in pursuit of the sardines.

However, our Sardine Run experience did not end here. The next day was a new day, with a new game plan and new luck! Birds could be seen far off in the distance. After a 45-minute rubber-boat ride into the middle of Algoa Bay, we could see lots of birds, and big splashes of water could be seen in the distance. As we got closer, the water seemed to be boiling with dolphins.

We arrived at just the right time. The dolphins had isolated some of the sardines and pushed them just under the water’s surface. Now, the dolphins circled the sardines and kept the swarm under control, forming a “bait ball.” The sardines diverged in all directions to escape the dolphins. About 200 dolphins worked together in a coordinated manner to get the best out of the situation. While some of the animals circled the sardines, others shot through the shoal of fish from below, to be followed soon after by even larger predators—Bryde’s whales.

With their mouths wide open, four to five of these whales alternated in pushing through the mass of fish, always behind the quick dolphins. The sardines kept jumping out of the water to escape. The whole spectacle was picking up speed. We watched the goings-on from a distance, amazed and overwhelmed. None of us had expected just how overwhelming it was to watch, and this was just the beginning of the spectacle!

Again and again, the dolphins coordinated their attacks with whistling sounds, circling the sardines, sometimes on the left and sometimes on the right. The Bryde’s whales kept pushing the sardines to the surface. Now, the seals also came to hunt at the edge of the swarm.

Cape gannets shot into the water from the air. These birds can dive and hunt down to 15m, but now that the fish were at the surface, it became easier for other seabirds to partake in this excess of food, and the amount of birds hovering over the event got denser. The water was foaming white due to the predator activity. An almost circular area of about 200m in diameter seemed to be bubbling.

Over and over, the dolphins shot through the water at high speeds, and the whales catapulted half of their bodies out of the water with their mouths open or slid along the surface to swallow large numbers of sardines. Sometimes, the sardines jumped out again—but there was no escape.

Underwater photography

We attempted to take underwater photos of the action, but the water was cold and thick with the silvery scales of the sardines floating around like confetti. In addition, the water was full of tiny air bubbles due to the frantic activity of the animals. Meanwhile, dolphins shot past, ignoring us. Seals took a quick look at us and disappeared immediately. What is called a “feeding frenzy” was in full swing, and we snorkelers were right in the middle of it—it was pure adrenaline!

It was difficult to take pictures, but the action-cam was better able to capture what we were witnessing. The feeling was indescribable. We were shoved around by dolphins, which were only focused on hunting. Their whistling sounds could be heard as well.

The whole event found its own rhythm and produced a strange swell in which we swam. The visibility in the water was so bad, however, we could hardly see anything. Not so for the dolphins and whales though, which could perceive every movement and every energy field in the water with their fine senses. They coordinated themselves again and again, and circled the school of fish. Over and over, the sardines shot towards us, followed by a group of dolphins, and after them, a whale with its mouth open. This process repeated itself continuously at a frenetic speed, which increased over time.

Suddenly, a Bryde’s whale below us grazed our fins. It was very close; we only noticed it at the last minute, but the whale knew exactly where we were. Perhaps it also thought we were lame dolphins. It moved past us with its mouth open and its eyes closed. At 15m long and 15 tons in weight, its bow wave lifted us up like a ship’s.

The circle drew ever tighter as the sardines huddled together and jumped out of the water. The birds plunged into the water from above, so a sardine’s jump into the air was no solution to escape its certain fate. Like vultures, the birds circled in the air, screeching loudly, while the dolphins circled in the water—their speeds increasing, like a whirlwind.

Sharks join the party

The shoal got smaller and smaller, and after a while, the fish crowded into a compact ball. Copper sharks joined the spectacle. With poor visibility, we chose not to stay in the water. From the boat, we got a better overview of the action and could follow the event more easily and more safely. We saw sharks heading into the bait ball again and again. The sardines sought shelter under our boat, as the sharks’ dorsal fins cut through the water’s surface next to us.

Normally, in good visibility, this would be an opportunity to go into the water with dive gear and observe what is known as a bait ball—a compact ball of densely packed fish—through which the sharks, dolphins, seals and birds darted, hunted and ate. Depending on the situation, these bait balls can reach a diameter of up to 15m.

For safety reasons, we stayed on the boat; the water was cloudy, with poor visibility—it was too dangerous to be underwater. In this situation, one may also see sharks with fresh bite injuries. As a snorkeler or diver in this environment, you would always be at the short end of the stick, even if a shark bites you accidentally. The conditions were not ideal for photography anyway. But watching the events from the boat was also an impressive experience.

Last chance for birds

The bait ball was getting smaller. After so many predators joined the feast, injured sardines could be seen swimming around everywhere. The gannets still plunged into the swarm—always 10 to 15 gannets in quick succession, like a fighter squadron in an air raid. They sighted their prey, folded their wings into a streamlined triangle and plunged at high speeds into the water.

In the meantime, some of the big Cape cormorants also arrived and participated in the battle at this cold buffet. Even seagulls and small seabirds now had a chance to get something out of the remains left by the larger predators. But while boobies and cormorants could actively dive and chase the fish, the remaining seabirds only pecked bits off the surface of the water.

During the whole event, there was a constant rotation of birds. The boobies, which had already caught enough fish, flew in small groups in a chain formation back to Bird Island, where their hungry offspring waited in their nests. As new groups of birds came to hunt, previous groups flew back to the island—a constant coming and going.

One last time, a Bryde’s whale rushed through the swarm, suddenly swallowing the sardine ball, which was now quite small, while dolphins circled the whale and snatched the last escaping sardines. There was almost nothing left of the huge mass of sardines that we came across four hours earlier! What a spectacle! What a day!

On the way back to the harbour, we were tired, hungry and thirsty. Nobody had had time to eat or drink during the eventful day, but our cameras’ memory cards were full of impressive photos and videos. However, our impressions had not yet been properly processed, as it had been an overwhelming day.

After six days on the water, all the photographers and filmmakers in our group had gotten their money’s worth. However, the weather had not always played along. Strong winds and the associated high waves had not always permitted safe passage. Sometimes, we were able to enjoy an alternate option—diving on the wonderful colourful coral reefs along the coast, which supported breath-taking biodiversity.

Visiting penguin and bird reserves, as well as observing seals dozing and warming up on rocky outcrops, were also nice alternative excursions, when the sardines were not “running.” In addition, the game parks on land also offered a nice change and opportunities to get photos of big game. We ended our trip to South Africa with full memory cards and hard drives—our wonderful impressions preserved for a lifetime! ■

For more impressions of this adventure, go to the following video link on YouTube: .

The next adventure is waiting, so if you want to join me on the next Sardine Run trip, do not hesitate to get in contact with me and I will send you all the details. I will accompany only small groups of six to seven photographers max. The next trip will take place in late June/early July 2020 or later, in 2021. Just email me for all the information and conditions involved in the Sardine Run trips: weber-gebert@design-buero.org. You can also contact me via Facebook at: .

The gossip press said: “Diver Swallowed by Whale”
— Here's what really happened…

The story of how a diver was swallowed by a whale at Sardine Run showed up in all the media—worldwide. However, I was there, and I can tell you, no, the diver was not swallowed! And, no, we could not see the whale coming. And, yes, all precautions had been taken—and, no, it was not intended!

Many views were shared. Some admiring, others shaking their heads. Critics said all of these activities to see the whales and other animals at Sardine Run should be forbidden; they disturb the animals too much. But according to my observations, this is not the case. If you keep calm, you do not disturb the animals. It is a little like watching cows graze in a pasture. Nobody claims that this disturbs the cows. While the animals at Sardine Run might perceive the boat and the people, they are so busy eating that they do not care who is there, observing.

On the previous day, our tour operator, Rainer, pointed out that it could happen—that a snorkeler would end up in a whale’s mouth—but that it had never happened before, and the probability that it would happen was quite low. Nobody knew exactly what would happen then, because no one has ever reported it. However, everyone had been instructed about it and all precautions had been taken.

Unexpected

The next morning, we found a bait ball. The boat stopped, and we first checked conditions and accessed the situation—finding dolphins, sharks, boobies and a lot of sardines. The opportunity was good now to take some beautiful photos of the sharks at the bait ball. So, four of us went into the water.

We were barely in the water five minutes, checking the conditions, when it happened. I was about five metres away from Rainer and two safety snorkelers. The visibility underwater was poor, at a maximum of 3 to 4m. I checked the settings on my camera underwater, looked up and saw a Bryde’s whale shoot up exactly where the others were in the water—and then I saw two legs in its half-opened mouth!

I saw a green weight belt—it was Rainer, who just the evening before had said that it was highly unlikely that something like this would happen. The whale lifted the snorkeler out of the water, about 2m high. Then I saw the whale dive down, and it passed underneath me. I could not see Rainer; either he was completely in its mouth or out again. I could not tell from my position, with the slight waves on the water’s surface obscuring my downward view. Then I looked across the surface of the water again and saw Rainer—all was well!

How it happened

What had happened was this: The whale noticed its mistake and immediately spat a mass of water out of its mouth, including Rainer. The second snorkeler, Gehard, had been pushed to the side by the whale when it shot upward, and Viktoria, who was to the right of Rainer, was briefly pressed underwater—the whole scenario took exactly 1.8 seconds—as one could later see in the series of photos taken by Heinz Toperczer. Heinz was a few meters away on the boat and just happened to be able to take pictures of it all.

Fortunately, nothing happened to either the whale or the snorkeler. The question remains though, as to who was more scared—the man or the whale?

Whale behavior and bad viz

In all my photos from the trip, I could see that the whales closed their eyes while their mouths were open. The whale could not have seen the man in the water anyway because of the murky water conditions. Of course, the whale was aware of the man, just maybe not that he was a human being, but perhaps thought he was a dolphin or seal, which is quite possible due to his size. The whale was probably familiar with the behaviour of the animals around it—that they jumped aside quickly enough when it approached. This was our observation too: First, the dolphins jumped out of the water in an arc, then the whale followed. The strange object in its mouth was spit out immediately. As I have heard since then, this behaviour has been observed several times—dolphins, seals and birds have also been seen spit out by whales.

But at no time would there have been a risk that a human would be swallowed. The throat of a Bryde’s whale is only about the size of a fist, so that fish or maybe a bird might pass through it, but never a human being. The only danger would have come in the form of broken bones and bruises, or if the whale had submerged with a human in its mouth. We prefer not to imagine that.

In any case, this was never the whale’s intention—baleen whales are not man-eaters! And it was not our intention that one of the groups in the water would end up in a whale’s mouth. We all kept a proper distance from the action. However, the sardine mass was in constant motion, back and forth, drawing predators with it. This could better be seen in clear water, but not in conditions with poor water visibility.

Afterthoughts

My personal impression: It was a wonderful, unique experience to be so close to a whale and to experience just how careful and sensitive these 15-ton colossi really are. Just think: A person who finds a fly in his or her soup might squash it. In the case of the whale, it would have been easy for it to flatten us four relatively tiny snorkelers with one slash of its fluke, but it did not. On the contrary, it was more eager to dive away from us as carefully as possible. These animals are indeed gentle, unique and admirable. ■

Originally published

on page 17

News in images