Many coastal areas around the world struggle with jellyfish blooms and it appears to be related to our impact on the oceans. In some areas jellyfish are an invasive species, especially in over-fished parts of the world. These blooms usually occur when there is a change in nutrients, prey increase or a reduction in predation. Jellyfish feed on small fish, crustaceans, and plankton and so if there is a decrease in larger fish, the ecosystem will not be maintained at a healthy level. Removing top predators will disrupt the food chain entirely and with no other species to compete for the same food that jellyfish eat; they will start to occupy the area.