Final answer:
Overfishing is a serious problem that threatens certain fish species. It is caused by fishing techniques like the use of modern factory trawlers, along with unregulated access to fisheries and economic forces driving overfishing.
Step-by-step explanation:
Overfishing is a serious problem that threatens many fish species. Some examples of overfished fish include the western Atlantic cod and certain whale populations. This is primarily caused by fishing techniques that allow for large-scale harvesting, such as the use of modern factory trawlers. These fishing techniques, coupled with unregulated access to fisheries and economic forces driving overfishing, contribute to the decline of fish populations.