Whale Sharks
By: Arabella
Whale or Shark?
Whale sharks (Rhincodon typus), are gigantic but harmless sharks. Or is it a whale? The whale shark is often mistaken for a whale because of its size, yet it is actually a species of shark, the carpet shark. This is based on their physical features, such as their spotted skin pattern, gill slits, and gill rakers that are used for filter feeding, we’ll get to that later. Whale sharks are the largest known species of fish, sizing from 18 to 55 feet, the size of a bus. They weigh up to 20 tons, the same as a small jet! Despite their whale-like appearance and the “whale” in their name, whale sharks are a distinctive species of shark, and not a whale.
Habitat and Migration
Whale sharks are found in the warm, tropical and subtropical waters of the world’s oceans. Whale sharks prefer waters with temperatures between 21-30°C and can be spotted swimming near the surface of coastlines, coral reefs and atolls. I have been fortunate enough to observe whale sharks in two remarkable locations – the coastal waters around the Las Perlas Islands of Panama, as well as within the atolls of the Maldives. However, these fascinating creatures don’t just stay in these areas. Every year, whale sharks have remarkable migration patterns. They can be observed moving along the Gulf of Mexico and the Caribbean, between the months of May and September. But their movements don’t stop there. These extraordinary animals also venture north to Mexico, south to Ecuador, and even west into the big blue ocean. This journey can get up to distances of over 20,000 kilometers, halfway around the world! Why do they undertake these impressive migrations you may ask? Well scientists believe these migrations serve many important purposes, such as optimizing with their growth, helping with their breeding activities, and providing them access to potential birthing grounds. The migratory patterns and behaviors of whale sharks continue to fascinate scientists, showing a glimpse into the remarkable adaptations and capabilities of these intelligent sharks.
Filter Feeding
Whale sharks diet consists mainly of plankton, tiny crustaceans like krill, and small schools of fish. But how does the world’s largest fish manage to survive by consuming some of the ocean’s smallest inhabitants?
They can because they are filter feeders. To eat, whale sharks open their humungous mouth, and scoop up everything in its path, the water along with their tiny prey. As the water and beings enter the whale sharks mouth, it passes over the whale shark’s gill rakers. These comb-like structures, made of cartilage and keratin, act as a sieve, trapping the tiny plants and animals inside, while allowing the water to flow back out through the shark’s gill slits which are located on the sides of its head. The small prey items that have been trapped by the gill rakers are then swallowed by the whale shark, providing it with much nutrition. This filter-feeding process allows whale sharks to efficiently eat energy-rich plankton and small fish from massive volumes of water.
Reproduction and Life Cycle
Birth: Whale sharks are ovoviviparous, which means the eggs hatch inside the female’s body and the young are born live. fun fact: A female whale shark can give birth to as many as 300 pups at a time!
Growth: When they are first born, whale shark pups are only about 40-60 cm long. They grow very slowly, only adding about 30-60 cm per year. It takes them around 30 years to reach full adult size, which is about 12 meters long.
Reproduction: Whale sharks start reproducing at around 30 years old. The mating process involves the female releasing her eggs, which are then fertilized internally by the male. This leads to an incubation period of about 12 months before the offspring are born.
Dangers and Threats
Bycatch: Unfortunately, whale sharks are sometimes accidentally caught in commercial fishing nets and lines that are intended to capture other marine species. This unintentional bycatch can be extremely harmful to the whale sharks, often leading to serious injuries and death. The large size and slow-moving nature of whale sharks makes them particularly vulnerable to becoming entangled in fishing gear. Protecting whale sharks from unintentional capture is crucial to ensuring the survival of this unique species.
Boat Strikes: Whale sharks face numerous threats to their survival, one of the most significant being collisions with marine vessels. As these enormous fish often feed and swim near the surface, they are highly vulnerable to being struck by ships, boats, and jet skis. These collisions can cause severe injuries or even death for the whale sharks. Some areas with high concentrations of whale sharks have put speed limits and routing measures for vessels to help reduce the risk of hitting a whale shark.
Climate Change: The warming of the world’s oceans due to climate change has had significant impacts on the natural migration and feeding behaviors of whale sharks. As global temperatures have risen, ocean current patterns have shifted. Because of these changes, the time and locations of these plankton blooms have become less predictable. This forces whale sharks to spend more energy searching for food, which can be particularly challenging for juveniles and pregnant females that require more. As their environments conditions are changing, whale sharks must adapt new migration patterns to continue finding the right nourishment, which can be incredibly challenging.
Habitat Decline: Coastal development, pollution, and other human-caused changes to the environment pose significant threats to the wellbeing of whale sharks. In addition, pollution, oil spills, and marine plastics can contaminate the waters where whale sharks feed, potentially poisoning them. As these gentle giants roam the open ocean, They rely on healthy marine ecosystems to find the plankton and small fish. When human impacts damage or destroy their feeding areas, it can disrupt their ability to find food and thrive. It is our job to do all we can to help them.
Poaching and Illegal Trade: Whale sharks face a major threat from poaching and the illegal wildlife trade. Despite protections in many countries, there is an ongoing demand for whale shark meat, fins, and other products, particularly in Asia where whale shark fins are used in shark fin soup. This illegal hunting and trafficking continues to be a major challenge to the conservation of this vulnerable species. Poaching and the illegal wildlife trade pose a serious threat to the long-term survival of whale shark populations globally.
Although massive, whale sharks are docile fish who do nothing to us, yet they are currently listed as a vulnerable and endangered species. We must do all we can to protect these gentle giants.
My Encounters
In Las Perlas, a group of islands on the pacific side of Panama, we encountered our first ever whale shark! We had already seen half a dozen whales around us, and hundreds of dolphins splashing around, but the best thing that happened was spotting a whale sharks fin peak out through the waters surface. Everybody was running around, trying to get their masks on. Some changed into their bathing suits, and some just jumped in fully clothed. We jumped into the water as fast as we could and swam over to it. The whale shark was just relaxing on the oceans surface and didn’t mind us oohing and awing at it. Just when we thought we’d lost the whale shark, another appeared! It was the most memorable experience i’ve ever had with a whale shark.