What do you get when you combine overfishing with large-scale nutrient runoff from industrial farms into rivers and the sea? Plagues of jellyfish:
The Namibian coast, for instance, used to be “hugely productive in fish,” [UBC fisheries graduate student Lucas Brotz] says, “and now it is entirely dominated by jellyfish. Things appear to be going that way in the Middle East, South Pacific, the Gulf of Mexico and the Mediterranean.”
This is what unlimited fishing with ever-better gear inevitably produces – short term profits for a few years followed by severely degraded ecosystems indefinitely.