April 9, 2014 — Pulsating gelatinous sea creatures, which float through the water like alien life-forms, appear to be on the increase in portions of Puget Sound.
Jellyfish are not welcomed by most biologists, who have learned that these translucent creatures tend to show up when the ecosystem is troubled. They’ll take a bite out of the lower portion of the food web, gobbling up plankton that could otherwise feed herring and other forage fish — which, in turn, are important prey for salmon, birds and marine mammals.
Casey Rice of NOAA’s Northwest Fisheries Science Center said there is a lot to learn about jellyfish, but one thing seems clear. When the number of jellyfish is high, the number of forage fish, such as herring, is low.
The cause and effect are not well understood. Some say humans have inadvertently invited the jellyfish into local waters by releasing excess nutrients from sewage into the water. The nutrients produce tons of algae, which feed larger plankton, which are eaten by jellyfish in competition with forage fish.
In some cases, overfishing has reduced forage fish, which leaves the food supply wide open for jellies. Ironically, jellyfish are caught in fishing nets, creating a major nuisance for fishermen.
Since they have few predators, jellyfish tend to stick around too long, maintaining their troublesome ways. They seem to survive better than fish in low-oxygen conditions. And when food supplies run low, they may out-survive fish by drifting about and using very little energy.
Read the full story at the Everett, Washington Herald