FunNature & AnimalThe largest fish in the world is the whale...

The largest fish in the world is the whale shark.

The largest fish in the world is a shark . And when talking about great sharks, the first image that comes to mind is that of the great white shark ( Carcharodon carcharias ), sadly famous from the Spielberg movie, which is also called ‘jaquetón’. It is, without a doubt, a huge shark, between 5 and 6 meters long. Although there are records of a silky shark of more than 11 meters in length, trapped on the Canadian coast, in the 30s of the last 20th century, apparently it was a mistake in the identification of the species, and it could actually be a basking shark ( Cetorhinus maximus ), which is much larger.

And it is that, indeed, the great white is far from being the largest fish in the world. At least five species outnumber the silky shark: the Greenland shark ( Somniosus microcephlus ) and the giant oarfish ( Regalecus glesne ), which can exceed 7 meters; the giant manta ( Mobula birostris ), which can reach 8; the aforementioned basking shark, which is the second largest fish in the world, and of course, the whale shark .

Specimens of whale sharks ( Rhincodon typhus ) of up to 17 meters in length have been observed. They are ovoviviparous, the eggs hatch inside the mother’s body, and give birth to live young, which can be more than 300 in each clutch.

What does it feed on?

It is one of the few species of shark that is a filter feeder , on any small-sized organism that floats in front of it. Most of their diet consists of plankton —microscopic organisms that float in the water—, algae and krill , a type of tiny crustaceans, similar to small shrimps, which are the food base of many marine animals. However, it can also feed on other crustaceans, small squid or small fish, such as sardines, anchovies, mackerel, and even juvenile tuna and bonito.

To feed, it opens its mouth and turns its head from side to side, with part of it above the water. Then it opens and closes its mouth repeatedly, every 2 to 10 seconds, synchronized with the opening and closing of its gills that generate a strong current . In this way, all the small creatures that float in the nearby waters are sucked up by the shark.

Is the whale shark dangerous?

Whale sharks are peaceful animals that pose no risk to humans. In fact, they are perceived as friendly. In some areas they are used as a tourist attraction, and visitors are encouraged to dive among them.

However, the interaction of tourists with whale sharks can have serious impacts , not on people, but on sharks, which can modify their behavior. It has been observed that whale sharks tend to stop feeding when visited by divers, and after contact, they take longer to resume activity and eat less.

In certain regions, such as the Seychelles Islands, there are programs that combine conservation and monitoring of whale shark populations with their use in ecotourism , following firm codes of conduct to minimize the impact on their behavior. The prior training of tourists as well as strict compliance with the rules of conduct help raise social awareness in the preservation of this emblematic and fascinating species, and the economic benefits obtained result in both research and actions that improve their status. conservation.

How many are left in the world?

Although it is a species whose individuals are easy to identify —the pattern of points on its back is unique to each individual, like human fingerprints—, there is no exact data on how many specimens exist through simple observation. According to the latest report from the International Union for the Conservation of Nature (IUCN), genetic studies can give approximate values, but with very low precision . An analysis using mitochondrial DNA yielded an estimated population of 178,500 sharks, but with an error range of up to 33%. Using microsatellites, the estimated size was 103,572, but the error range shot up to almost 74%.

What we can know is that, whatever their numbers, whale shark populations are declining, sightings are becoming rarer, and when they do happen, fewer individuals are seen. For that reason, Rhincodon typhus is a threatened species, considered endangered .

References:

Colman, J. G. 1997. A review of the biology and ecology of the whale shark. Journal of Fish Biology, 51(6), 1219-1234. DOI: 10.1111/j.1095-8649.1997.tb01138.x

IUCN. 2016. Rhincodon typus (e. T19488A2365291) [Data set]. International Union for Conservation of Nature. DOI: 10.2305/IUCN.UK.2016-1.RLTS.T19488A2365291.en

Montero-Quintana, A. N. et al. 2020. Ecotourism impacts on the behaviour of whale sharks: an experimental approach. Oryx, 54(2), 270-275. DOI: 10.1017/S0030605318000017

Rowat, D. et al. 2007. Seychelles: A case study of community involvement in the development of whale shark ecotourism and its socio-economic impact.

Fisheries Research, 84(1), 109-113. DOI: 10.1016/j.fishres.2006.11.018

Pyrophytic plants, lovers of fire

There are plants that are capable of surviving different types of fire, or that produce seeds capable of withstanding fire; even some that depend on fires to complete their life cycle.

Rare multicolored sea slug found off the coast of England

The rainbow creature is just 2 centimeters long and has never been seen in British waters.

What is diatomaceous earth used for?

In addition to its function as a fertilizer, insecticide and acaricide, this product whose origin is fossil algae has multiple practical applications.

Welwitschia, the potentially immortal plant

This huge gymnosporm plant from the Namib Desert in Namibia has only two leaves, which it retains throughout its millennia-old life.

Rainwater contains permanent chemical contaminants

It's raining PFAS. Chemicals that can cause cancer are falling in the form of rain across the planet, a new study concludes.

More