By Nicole Rojas | n.rojas@latinospost.com | @nrojas0131 (staff@latinospost.com) | First Posted: Jan 03, 2013 01:35 PM EST

Jellyfish swim in a fish tank at Palma aquarium in Palma de Mallorca on the Spanish island of Mallorca July 16, 2007. (Photo : Reuters)

Despite international concerns that the jellyfish population is overtaking the world's oceans, a new study of long-term data has revealed that populations have largely remained the same throughout the years. The research, conducted by the Global Jellyfish Group, also discovered almost 20-year cycles in the population of jellies, LiveScience reported.

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According to the group of international researchers, the recent rise-and-fall cycle could have led to the misconceptions over increased jellyfish populations. LiveScience reported that the rising phase, which began in 1993 and peaked in 2004, could be the source of the concerns.

Humans have been blamed for the supposed rise in jellyfish blooms due to changes in the oceans that favor the gelatinous animals, LiveScience reported. Jellyfish blooms are large groups of jellyfish in a concentrated area. However, some scientists have contended that there isn't sufficient data to corroborate those conclusions.

Rob Condon, Dauphin Island Sea Lab scientist and lead researcher of the project, said, "Recurrent jellyfish blooms are a consequence of global oscillations."

AL.com reported that before this knowledge came to light, scientist believed that the jellyfish populations were rising and could threaten the balance of the marine ecosystem.

"We submitted a proposal in 2009 to fund a working group to address this question of whether jellyfish are increasingly globally," Condon told AL.com. "Up to that time, there was no data to support this hypothesis that jellies were increasing in abundance."

So Condon and his group of researchers collected all previous research data, dating as far back as 1874, and analyzed the information, AL.com reported. According to LiveScience, the team included data from all oceans, although most of the data represented the Northern Hemisphere.

"There is a rising phase, and a falling phase," Condon said. "If you look beginning at 1990, you see a rising phase. That's when people were seeing this increase in jellies that lasted for ten years. Then there was a falling phase."

The researcher added, "These cycles are actually quite common. The question now is to understand how human influences on a particular ecosystem may be influencing the natural system."

Condon told LiveScience that researchers will need at least 10 more years of jellyfish data, including data from the Southern Hemisphere, to reach solid conclusions about the worldwide rises and falls of jellyfish populations.

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