Is it permissible to fish and leave the fish to die, and is eating canned fish permissible or forbidden, and how can we ensure that it has been slaughtered according to Islamic law?

Fish do not require ritual slaughter (dhakāt) or the pronouncement of Allah's name (tasmiyah), whether they die in the sea or are taken out and die in the air. This is based on the Prophet Muhammad's (peace be upon him) saying about seawater: "It is pure and its dead are lawful." Therefore, eating canned fish is Islamically permissible.