Under the law of the United Kingdom, the monarch owns all sturgeon and whales as part of the royal prerogative.
The law was enacted in the 13th century under Edward II. It was decreed that the king owns the head and the queen owns the tail of every such sea creature. The Receiver of Wreck is appointed to take possession on behalf of the monarch.
Lest one think this is an antiquated law that has fallen from memory, it was enforced as recently as 2004 when a fisherman got in trouble for selling a sturgeon without first offering it to the Queen.