KOKONOGI, Japan (November 16, 2009)--Increasing invasions of fishing grounds by jellyfish are putting livelihoods at risk and climate change is to blame, scientists say.

In Japan, for example, the Nomura, the world's largest jellyfish, can ruin a whole day's catch by tainting or killing fish stung in the catch nets.

Some of the largest weigh as much as 450 pounds.

Once considered a rarity, the invasions are now an almost annual occurrence.

Scientists believe climate change has allowed jellyfish species to expand their ranges, appear earlier in the year and increase overall numbers.

In addition to industry woes, the National Science Foundation cited estimates of 500,000 stings a year in Chesapeake Bay on the U.S. East Coast.

Twenty to 40 people die each year in the Philippines from jellyfish stings.