Whale Sharks

This incredible animal (Rhincodon typus), a member of the shark family known for its ability to filter-feed and as the world’s largest living fish, has a lot going for it.

A few notable facts about whale sharks include:

• Average Length: 5.5-9.8 meters
• Longest recorded whale shark: Longer than 12 meters
• Weight: Can weigh up to 20 tons
• Estimated lifespan: 80-130 years.

Whale sharks move slowly through the water and keep their mouths wide open, allowing them to act as natural nets that filter out small marine organisms. The massive size, combined with their extremely non-aggressive behaviour, has led to some misconceptions about this incredibly gentle ocean creature.

This type of shark poses an extremely low risk to human safety, and as such, they exhibit many characteristics that illustrate how dangerous it would be to fear all sharks.

• There is no evidence that whale sharks actively seek out large prey.
• Whale sharks do not use their small teeth for capturing food.

It is common for whale sharks to swim slowly near scuba divers and boat operators with little to no hesitation. The lack of documented attacks from a whale shark on a human (and no documented fatalities) is an excellent example for marine biologists and students about why not all sharks should be feared.

These sharks are part of a tiny group of shark species that use filter-feeding methods (like baleen whales).

Typically, the main foods for whale sharks are:

– Plankton

– Krill

– Fish eggs

– Small schooling fish

– Tiny Crustaceans

How they eat

– The whale shark swims forward while keeping its mouth open.

– Water rushes into the shark’s mouth, containing food particles.

– Specialised filtering pads catch food.

– Excess water exits through the gills.

As such, this feeding strategy allows whale sharks to rank among the most efficient feeders in the ocean, even though they can grow to huge sizes.

These giant fish roam warm tropical and subtropical oceans worldwide. The majority of whale shark sightings occur within the global range of 30 degrees north and 35 degrees south latitudes. These areas have a high volume of nutrients for their diet due to warmer water.

Some of the common places that they live are:

• Pelagic zones of open ocean
• Reef coasts
• Seasonal plankton bloom areas
• Shelf regions near island or coastline

These animals travel large distances to find food and many migrate long distance, often hundreds and sometimes thousands of miles per year.

Although whale shark sightings are rare in South African waters, they can still occur. Their sightings are much more likely in warmer parts of the Indian Ocean than in other areas.

These include Mozambique, Tanzania, and Seychelles.

While they do not occur frequently off the KwaZulu-Natal coastline, their presence in proximity to these waters illustrates the remarkable biodiversity of the Indian Ocean System and its impact on Durban’s marine ecosystem.

Reproduction and Life Cycle

One of the least understood reproductive methods of a large animal (in terms of marine biology) is that of the whale shark.

Scientists know this about their reproduction:

• Ovoviviparous: The egg develops within the mother’s body; the young will be born alive (as opposed to being laid)
• Live births occur from the female; documented counts of females with over 300 developing embryos have been reported
• At birth, young whale sharks are approximately 40-60 cm in length

As slow-growing animals that mature late in life and have lives that span many decades, recovery of population levels takes an equally long time (i.e., they take a long time to recover if their numbers decline). Therefore, it is even more critical to protect and conserve them for the long-term for their continued existence.

One of the most apparent characteristics of these gentle giants is their distinctive spot patterns.

The spots on whale sharks:

• Serve as a unique identifier for each individual (similar to human fingerprints)
• Help the whale shark camouflage itself when viewed from above

Researchers studying marine whales can utilise software that recognises spot patterns to track the migration routes of whale sharks without invasive tagging.

To obtain information about whale sharks without harming them, researchers are using non-harmful methods of study.

Some of these non-invasive methods include:

• Spot pattern photo-identification
• Satellite tagging
• Environmental DNA (eDNA) sampling
• Airborne studies and underwater observations

To find an in-depth view of research being done globally regarding whale sharks, you can visit the NOAA Fisheries whale shark research webpage. The NOAA Fisheries whale shark research webpage is a reliable, scientifically based resource for marine scientists worldwide studying whale sharks.

What Can We Do to Protect Whale Sharks?

Even though you may never get to see these sharks personally, it still makes a difference in what you do.

Here’s how you can help:

• Reduce your plastic use
• Support marine conservation education
• Respect wildlife regulations
• Learn and share accurate information about whale sharks
• Protection begins with knowledge of the subject.

These sharks teach us that the oceans are full of creatures which don’t have preconceived notions or expectations based on their size, age, or appearance. Large and gentle, old and vulnerable; these characteristics challenge the fear of sharks as aggressive creatures.

If whale sharks have inspired your interest in learning about sharks and marine ecosystems, then learning about the diverse ocean life around Durban could be a decisive next step. At Durban Shark Diving, education and respect for marine life go hand in hand. Visit our blog page to learn more about the diverse ocean life in and around Durban.