Evidence from ecosystems around the world suggests that jellyfish blooms are increasing in terms of frequency and severity, most likely due to human activities such as overfishing, habitat modification, and species introductions. Although jellyfish have some positive benefits to humans in terms of pharmaceutical and food production and the aquarium trade, most of their impacts negatively affect human endeavors such as fishing, tourism, and power generation. Ric will discuss the evidence for increasing jellyfish populations and their potential impacts on fish and fisheries, using examples in ecosystems around the world and attempts to control these populations or mitigate against their impacts.