Remember all those discussions in the last couple of years about how fishing out all the top predators in the sea would let jellyfish blooms take over and perhaps keep the fish from coming back by killing more young fish? It’s happening—and not from predation, but by sheer numbers. A flock (school, quiver, bowlful?) of jellyfish covering about 10 square miles and up to 11m deep engulfed the cages of the only salmon farm in Northern Ireland. The fish were smothered and the owners lost more than a million pounds sterling overnight.
The billions of jellyfish, piled densely in a 35-foot-deep layer, did in the fish through stings and stress, according to John Russell, managing director of Northern Salmon.
The Pelagia nocticula species, or “mauve stinger,” is normally found in warmer waters such as the Mediterranean Sea. Scientists pointed to the presence of the jellyfish, rarely seen that far north, as evidence of global warming.
Another reason for the swelling population of jellyfish is human elimination of predators such as fishes and turtles that would eat them.
This will be reported in Nature.