The Collaborative International Dictionary
sea partridge
Gilthead \Gilt"head`\, n. (Zo["o]l.) A marine fish. The name is applied to two species:
The Pagrus auratus (syn. Chrysophrys auratus), a valuable food fish common in the Mediterranean (so named from its golden-colored head); -- called also giltpoll.
The Crenilabrus melops, of the British coasts; -- called also golden maid, conner, sea partridge.
Wiktionary
sea partridge
n. The gilthead ((taxlink Symphodus melops species noshow=1)), a fish of the British coasts.