Cnidarian overpopulation

In Japan, jellyfish are compromising fisheries

Jellyfish, animals belonging to the Phylum Cnidaria, are often the terror of some bathers around the world, as they have stinging structures capable of causing serious burns.

Data confirm that, in recent years, these animals have been seen more frequently, and also in greater numbers. In Japan, for example, since 2002, the overpopulation of jellyfish of the Nemopilema nomurai species compromises fishing: one of the main economic activities in the country. With a size that varies between one and two meters in diameter, and over two hundred kilos, they are capable of destroying fishing nets, killing fish and, as expected, injuring human beings. This phenomenon, now of annual frequency, previously occurred at intervals of 40 in 40 years.

In Brazil, the Portuguese caravels of the species Physalia physalis and Olindia sambaquiensis and the jellyfish Tamoya haplonema and Chiropsalmus quadrumanus , are the cnidarians that most cause accidents. They migrate from the Falkland Islands, in the south of the Atlantic, in search of warmer waters to reproduce, favoring their appearance, mainly on the beaches of Santa Catarina, Paraná and the south coast of São Paulo. There are also records that exotic species have appeared in our country, possibly “hitchhiking” on ship hulls or in ballast water. Such information becomes more relevant if we consider that species from other regions can compete and even prey on native species…

It is believed that these events have occurred more frequently due to the increase in water temperature, related to climate change, and also as a result of indiscriminate fishing, since, with the reduction of the fish population, the availability of food becomes be larger, increasing the chances of survival and reproduction of cnidarians. In addition, the hunting of its main predators, the sea turtles, also leads to the lack of control of its population.

Considering that, basically, our species is responsible for overpopulations and species extinctions, this fact can be important in the reflection that our way of life is unsustainable and, obviously, we are not unharmed from its consequences.

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