What are they?

They are amongst the largest marine life in our oceans. They feed on plankton and small fish which they filter from the water like a sieve, and even though whale sharks have upwards of 300 tiny teeth, they are completely harmless to humans. They have been encountered in several parts of the world. Research projects have provided some understanding and insight into the different species and their behaviours.

Image: WildLife Risk.

Through electronic tagging, tissue sampling and photo identification, a lot can be discovered of the behaviours of Ocean Giants. Whale sharks can dive up to a mile deep, and routinely swim over 6000 miles each year. Giant manta rays can also travel long distances. Whale sharks need approximately 25 years to mature, and routinely live for 100 years. There is still only very limited knowledge of their reproductive habits, but manta rays are known to have annual ovulating cycles, but have the slowest reproductive rate of all elasmobranch species.

Whale sharks and manta rays each have their own unique spot pattern like humans have a finger print. For whale sharks this is on their flank above their pectoral fin, and on manta rays it is on their underbelly. They can all be individually identified by these distinctive patterns, as well as by scars they may have acquired from encounters with boats, nets or sharks. Anyone can add pictures to the online databases to help track species through whaleshark.org and mantamatcher.org

Why are they in need of saving?

Capture for trade

Ocean Giants are hunted by both large scale fisheries and local fishermen. They are slaughtered in large numbers for the fins of whale sharks and the gill rakers of manta rays to supply the Traditional Medicine Trade or for perceived culinary delicacies demanded in Asia. Populations of both species continue to be decimated.

Image: WildLife Risk.

Changes in fishing methods

There is a vicious circle of overfishing leading to reduced populations, which then force fishermen to employ ever more aggressive methods to enable them to sustain their catch and livelihoods. Traditional rods and lines have been replaced with gill nets, which can run for miles, and indiscriminately catch any and all fish species. Ocean Giants get caught in these gill nets which often results in their death.

Habitat decline

Ocean pollution is an increasingly alarming problem. As Ocean Giants suck in large volumes of water to feed, it often contains plastic and other ocean debris. The plastic can get lodged internally and cause serious damage, even death. The decline in ecosystem health also adversely impacts the food chain. The more unhealthy our oceans, the smaller the fish and plankton populations that this sensitive environment can support. Less food, fewer Ocean Giants.