The world’s largest living fish!

Along the Coral Coast, on Australia's most accessible coral reef system, the Ningaloo Reef is one of the most reliable places on the planet to encounter the world's largest extant fish; the majestic WHALE SHARK (Rhincodon typus).

A whale shark with particularly striking pattern morphology, Coral Bay, Ningaloo Reef - Migration Media 2014

The whale shark (Rhincodon typus) is the sole member of its genus and the family, Rhincodontidae.

The reason for their possibly confusing title is because this species of shark, like many whales, are filter-feeders, and so along with their large size, they have been so-called ‘whale sharks’. These "large, dopey, spotty fish" (as I affectionately call them) are harmless, unless you are a tiny piece of plankton, or get in the way of their powerful caudal fin (tail). Their diet comprises mostly of tiny krill and plankton which they sift out of the water through their gills. 

Whale sharks are large migratory marine filter-feeders that aggregate in the Ningaloo waters annually from February/March to June/July. Their arrival of whale sharks to the waters of the Ningaloo Reef coincides with the cascading biomass production that follows the coral spawning events.

Coral Spawn - Migration Media 2014

A whale shark cruising the outer Ningaloo Reef - Migration Media 2014

Check out the footage of this interesting behaviour. 

Plankton, it seems, is not the only food for a whale shark...

Whale Shark - BBC Planet Earth

They are the largest extant shark (hence the largest fish) species in the world!

Of this largest known extant fish species, the largest confirmed individual was 12.65 m with a weight of more than 21.5 metric tons (unconfirmed reports of considerably larger whale sharks exist). Claims of individuals over 14 m long and weighing at least 30 mt are not uncommon (they really are HUGE; the biggest that I have swum with were as big as our 12m charter vessel!). The whale shark boasts many titles for sheer size in the animal kingdom, most notably being by far the largest living non-mammalian vertebrate, rivalling many of the largest dinosaurs in weight, owing to its aquatic life. Whale sharks are found in warm tropical waters and live in the open ocean, reaching sexual maturity at around 30 years with a lifespan estimated to be 70-100 years (there is much unknown!).

What is the purpose of their distinctive spotty patterns?

Like many species that frequent the ocean’s surface, whale sharks are counter-shaded. They have white bellies (which makes them hard to see if a potential predator is underwater and looking up at them) and dark backs (which makes them difficult to see if the predator is looking down on them). It has been suggested that the pale spots and lines on their backs act as camouflage. Each whale shark has its own unique pattern of spots (behind its gills and above its pectoral fin) that can be used, along with size, sex and scar marks, to identify individual whale sharks.

Interesting fact! – The whale shark has the thickest Dermal layer (skin) in the animal kingdom, up to 14cm thick!  – which is fortunate, as the increased shipping and boating traffic across the ocean poses a serious threat to any marine life in their direct path. Deep scars, gouges and even missing fins are often noted while encountering these docile creatures.

Remarkably, neither mating nor pupping of the world’s largest fish has been observed!… although, she’s a “mega-mumma”!

It has been found that they are ovoviviparous (producing eggs that are hatched within the body, so that the offspring are born alive but without placental attachment), with the females giving birth to live young 40 to 60 cm long. Evidence has suggested that around 300 embryos are at different stages of development and so the ‘pups’ are not all born at once, but rather the female retains sperm from one mating and produces a steady stream of pups over a prolonged period.

A young whale shark, Ningaloo Reef - Blue Media 2014

Sharks have existed for over 350 million years, evolving over 100 million years before the dinosaurs did. It has been suggested that the whale shark has been around for the past 60 million years, yet there is much that is unknown of the world’s largest shark. Their filter-feeding system is likely to be the greatest evolutionary element for them, since only three species of shark are actually filter-feeding organisms.

Recent studies have relied almost exclusively on mark–recapture data from photo-identification to estimate population size, age structure and survival rates of this mysterious creature.

Some individuals do return semi-regularly to the same aggregation site over time, but where they go and what they do in between is largely unknown. It is believed that they tend to stay within equatorial waters, possibly following currents and patterns of food production (such as coral spawnings). Information collected by tracking devices and satellite telemetry has provided some insights on short-term movements. However, a major issue with some of the radio-transmitting tracking devices that are used is that they only transmit a signal when at the surface. The issue is, that whale sharks are fish – they do not require to come to the surface to breathe, and so may not transmit reliable data.

Their large size and apparently slow reproductive rates suggest a particular vulnerability to overexploitation and rapid environmental change. Whale sharks appear to have a high dispersal capacity, and so an ocean-wide approach is necessary for the understanding and management of these ecologically important species.

 Watch:

Ocean Wanderers - Whale Shark Documentary

- The Documentary Network 

This documentary goes for ~28mins: to cut it down a bit for you, I suggest at least watching: 0:52–3:15; 9:30-10:10, 13:52–18.15, 19:45-(feeding)-20:37; 24:50-(breeding)-26:58. I was very pleased to see the emphasis made on education for future generations to “protect and nurture”.

This documentary follows the story of the Research trip off the coast of Qatar undertaken by the Maersk Oil Research and Technology Centre (MO-RTC) in partnership with the Ministry of the Environment's Whale Shark Research Project. Amongst the towering structures beneath the oil rigs is a gathering place for giant fish, a wonder of the world's oceans: Whale sharks, the largest known extant fish species. All the footage was captured on the Red Epic and, as such, has captured the majestic nature of these mysterious ocean wanderers.

A previous “job” of mine for a few years was to help deliver the “experience of a lifetime” in encountering and swimming with these majestic creatures in the wild. I have been blessed with uncountable

I have also been fortunate enough to guide for, assist and work alongside some of the world’s leading experts on whale sharks on a few research expeditions.

Whale shark and Encounter II - 2014 season, Coral Bay - Migration Media

It was really hard for me to sort through my own ‘references’ of images and footage (I have personal permission to share). These short films, made by (and featuring) my friends and colleagues on the Ningaloo Reef, will hopefully provide insight and enjoyment.

Watch: 

Ningaloo Reef Dive - Whale Shark Adventure | Swim with Whale Sharks Ningaloo Reef - migration media

Watch:

Ningaloo Reef Whale Sharks, Exmouth, Western Australia - westernaustralia

Another short video to give you a taste of a ‘Coral Coast’ experience which also features a few other Coral Coast crew members, including some fury ones! (I also used to work with this charter company featured: Ocean Eco Adventures J)

BIBLIOGRAPHY

Bradshaw CJA, Mollet HF, Meekan MG (2007) Inferring population trends for the world’s largest fish from mark–recapture estimates of survival. Journal of Animal Ecology, 76, 480–489.

Colman, J. (1997). A review of the biology and ecology of the whale shark. Journal of Fish Biology, 51(6), 1219-1234.

Joung, S., Chen, C., Clark, E., Uchida, S., & Huang, W. (1996). The whale shark, rhincodon typus, is a livebearer: 300 embryos found in one 'megamamma' supreme. Environmental Biology of Fishes, 46(3), 219-223.

Stewart, B. S., & Wilson, S. G. (2005). Threatened fishes of the world: Rhincodon typus (smith 1828) (rhincodontidae). Environmental Biology of Fishes, 74(2), 184-185.

Wilson SG, Polovina JJ, Stewart BS, Meekan MG (2006) Movements of whale sharks (Rhincodon typus) tagged at Ningaloo Reef, Western Australia. Marine Biology, 148, 1157–1166.

http://www.migrationmedia.com.au/