Final answer:
Trawlers contribute to overharvesting and bycatch, which threaten marine ecosystems and fish populations, exemplified by the tragedy of the commons. This unsustainable practice can lead to the collapse of fisheries, as seen with the western Atlantic cod.
Step-by-step explanation:
Trawlers are a type of fishing vessel that drag or pull large nets through the water, often leading to the unintentional catch of non-target species, known as bycatch. Trawlers can also be very harmful to various ecosystems due to practices like bottom trawling, which can damage the sea floor and disrupt marine habitats. The use of these vessels has contributed to the phenomenon of overharvesting, driving many fish populations to critically low levels. This situation is exemplified by the collapse of the western Atlantic cod fishery due to the introduction of modern factory trawlers. The idea of the tragedy of the commons reflects the economic and political challenges in managing these shared resources sustainably. The tragedy of the commons occurs when individual users, acting independently according to their own self-interest, behave contrary to the common good of all users by depleting that resource. This has been the case with large, unregulated fishing fleets that receive government subsidies, which then encourage continual fishing, even when fish stocks are declining. Overfishing and bycatch by trawlers not only threaten the sustainability of fish populations but also have indirect effects such as carbon emissions from the trawlers themselves, which contributes to climate change.