When catching a carp it bled from its gills why?

When a fish is caught, it experiences stress and fear, which can cause their blood pressure to increase. This can lead to ruptured blood vessels and bleeding from the gills. Additionally, Carp have two pairs of pharyngeal bones in the back of their throat that grind down food. Carp often swallow the hook when feeding and their struggle after being hooked, damages delicate parts of their mouth like blood vessels, tissues and gill filaments causing them to bleed from their gills.