In an unprecedented event on November 21 , 2007 , a 10-square-mile ( 26 km2 ) swarm of P. noctiluca wiped out a 100,000-fish salmon farm in Northern Ireland , causing around # 1 million worth of damage .
In an unprecedented event on November 21 , 2007 , a 10-square-mile ( 26 km2 ) swarm of jellyfish wiped out a 100,000-fish salmon farm in Northern Ireland , causing around # 1 million worth of damage .