Jellyfish in groups?

Question

DO Jellyfish travel in groups?? Also, if jellyfish are near the shore, are there other jellyfish that traveled with it.

Answer 1

Many species of jellyfish are capable of congregating into large swarms or "blooms", consisting of hundreds of individuals. The formation of these blooms is a complex process that depends on ocean currents, nutrients, temperature and ambient oxygen concentrations. Jellyfish sometimes mass breed during blooms. During such times of rapid population expansion, some people will raise ecological concerns about the potential noxious effects of a jellyfish "outbreak".

According to Claudia Mills of the University of Washington, the frequency of jellyfish blooms may be attributed to humans' impact on marine systems. She says that the breeding jellyfish may merely be filling ecological niches formerly occupied by overfished creatures. Jellyfish researcher Marsh Youngbluth further clarifies that "jellyfish feed on the same kinds of prey as adult and young fishes, so if fish are removed from the equation, jellyfish are likely to move in."



Aurelia aurita, commonly known as moon jellyfish.Increased nutrients in the water, ascribed to agricultural runoff, have also been cited as an antecedent to the proliferation of jellyfish. Monty Graham, of the Dauphin Island Sea Lab in Alabama, says that "ecosystems in which there are high levels of nutrients ... provide nourishment for the small organisms on which jellyfish feed. In waters where there is eutrophication, low oxygen levels often result, favoring jellyfish as they thrive in less oxygen-rich water than fish can tolerate. The fact that jellyfish are increasing is a symptom of something happening in the ecosystem."

By sampling sea life in a heavily fished region off the coast of Namibia, researchers found that jellyfish have overtaken fish in terms of biomass. The findings represent a careful, quantitative analysis of what has been called a "jellyfish explosion" following intense fishing in the area in the last few decades. The findings were reported by Andrew Brierley of the University of St. Andrews and his colleagues in the July 12, 2006 issue of the journal Current Biology.

Areas which have been seriously affected by jellyfish blooms include the northern Gulf of Mexico. In that case, Graham states, "Moon jellies have formed a kind of gelatinous net that stretches from end to end across the gulf."