Op-Ed: Sharks almost became extinct 19 million years ago: why?


Research on bighead sharks has revealed that sharks can obtain their position and orientation using the magnetic field generated deep on our planet – Copyright AFP –

Sharks are survivors of 5 mass extinctions. So how did 90% disappear 19 million years ago? This near extinction is also grimly related to a drastically changing global environment.

Researchers from the Atlantic College dhe discovered the event while researching ancient populations of fish and sharks. The near extinction was applied to the “ancient sharks.” These sharks are not the same things as our current forms. There are still a few survivors of ancient sharks, but not many.

Some things to understand here:

  • The extinction event was discovered by measuring the proportion of shark and fish scale fossils. Before the event, there were 1 in 5 before the extinction. After extinction, it was 1 in 100 fossils. This is a massive fall almost unthinkable.
  • Ancient sharks were much more numerous than modern sharks. This means that they were part of a huge ecology that could withstand a large number of major predators. Predators need a lot of protein. Obviously there were a lot of fish and other prey.
  • The number of sharks fell rapidly. 90% of the population and 70% of shark species literally disappeared.
  • These sharks include the famous ones Megalodon, the “big white” monster of the past. Megalodon survived this extinction event, but obviously many other sharks did not.
  • Shark populations have not yet recovered from this extinction event.

Umm … ah … We don’t know

The net carry of this information is likely to be an “event.” Predator populations are not disappearing for no reason. They usually fade due to lack of food. It is one of the advantages of being at the top of the food chain. However, there are no signs of falling prey populations in this case.

(There could be qualifiers for this extinction if there are data indicating fluctuations in prey populations that could mean that oceanic food deserts have existed there for any period of time, which would have decimated the number of sharks and populations. players.)

Researchers think that some of the world’s major populations even triggered this fall in the number of sharks. Global populations are not just disappearing at the same time. Sharks are also very hardy. They survived the Permian and Cretaceous extinctions, and the ice age. They can and eat anything they can bite.

Against this: Megalodon was around during this time. A super predator needs big prey. This tends to confirm the fact that the rest of the marine ecology was in good condition. Megalodon could also eat other sharks, which would not help much if there was hunger A limited number of a large predator simply could not kill so many fish of any species. (True, having superpredators eating anything around would not help the other sharks much.)

Sharks are very mobile and can be wide. Local fluctuations in prey populations would not have a large impact. Sharks could easily follow moving populations. If ocean food were scarce, they could move to shore, as they have done for millions of years.

Some options:

  • Ocean conditions can play a role, but what kind of conditions? What would affect predators, but not everything else?
  • Invasive species? Researchers do not believe the sharks were out of competition. These species should also have faced monster sharks.
  • Obsolescence? Did the new prey species outnumber the old sharks? It seems unlikely. Sharks hunt with prey bandwidths; they are seldom specialists and are not lost if some species of prey are inaccessible.

May be…?

A possible problem not yet mentioned is the vulnerability of the playback cycle. If there were a large number of sharks, there would also be a large number of sharks. An influx of new predators would inevitably target the abundant shark fry and perhaps the eggs.

It is possible that these new predators did not compete directly, but indirectly. Shark fry have a pretty good time anyway. Sharks and anything else that can eat them routinely eat them. An invasion of large numbers of something as large, voracious, and rapid as tuna, for example, would be a major success for any fry population. A good established breeding cycle, without discomfort for millions of years, would be highly exposed to a major catastrophic dislocation.

The scenario is that the prey was plentiful, but the sharks, being so numerous, became targets themselves. Reducing the number of fry, in sufficient numbers, would naturally eliminate future breeding populations.

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To prove it, you should find:

  • A smaller number of shark scale fossils
  • Numbers of credible active predators have been added
  • A clear statistical relationship between fry populations and subsequent breeding populations.

This mystery must be solved. The possible ecological problems and risks of invasive marine populations are obvious research objectives.

  • What happens when major marine predators disappear?
  • Do you have different predators or is there a thaw in the ocean food chain due to the rise of other types of fish?
  • What if you suddenly come across oceans full of a large number of ecologically “unfiltered” bottom feeders that absorb pollutants?
  • Are caught fish eaten without food?
  • What if predators in the anoxic zone, safe in low-oxygen areas, suddenly explode and cause fish populations to crash? (Only jellyfish could do that, exterminating fish).

The number of sharks is declining sharply due to overfishing and the shark fin trade. These are the main survivors of the ocean. Anything that has caused this could happen again. The possible results are to make it slightly dubious for humans who receive so much food from the seas.

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