Are jellyfish taking over the oceans?

Beach-goers will want to be on high alert when they wade into the water this summer, as populations of stinging jellyfish are booming in almost every ocean around the world. What's worse is that the pesky invertebrates seem to be most prevalent in areas where human activity is heavily concentrated. Here, a guide to the sticky situation:

What's the evidence that jellyfish populations are growing?

Since the mid-20th century, researchers have suspected that jellyfish populations were climbing. Those worries were confirmed recently when marine biologists from the University of British Columbia examined 45 of the world's 66 large marine ecosystems — including ocean regions in East Asia, the Mediterranean, Hawaii, and the northeast United States — scouring existing data and anecdotal evidence dating back 60 years. In 62 percent of those areas, jellyfish populations were confirmed to be on the rise.

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Why are jellyfish populations booming?

"Global warming, pollution, and human activity in marine habitats are not generally regarded as good things," says Gerry Bellet at the Vancouver Sun — "unless you're a jellyfish." Overfishing is one reason the jellies are having their day: When less fish are present, there's less competition when it comes to finding food like plankton. It also means that "jellyfish have fewer encounters with the ocean-dwelling predators that deign to eat them, such as salmon," says Canada's National Post.

Other than painful stings, why are jellyfish problematic?

Well, jellyfish stings shouldn't be underestimated. There are a couple of reasons no one likes the "undulating, translucent creatures," says the National Post. Not only are their stings incredibly painful, but they can also be lethal. Jellyfish stings claim around 40 lives a year; in contrast, sharks kill about eight people annually. And the tentacled creatures do "wreak" havoc in other ways: They can clog valves and drainpipes in power plants, ruin fishing nets, and, in some rare cases, even capsize small vessels.

Is there anything we can do to thwart them?

Not really. There aren't a whole lot of reasons to fish for jellies. Out of the 2,000 known species, only a few are fit for human consumption; those that are edible are highly valued in certain Asian cuisines. Other jellyfish uses: Russian scientists recently discovered that mixing the jellies' undesirables with concrete makes for stronger buildings, and grinding up the animals for pet food may be another way to keep the population down. But even then, says the National Post, there are still far too many jellyfish out there, and our efforts are "not large enough to stem the rising tide."

Sources: National Post, Red Orbit, Vancouver Sun, Yahoo