What does "sprat" mean?

Sprat: (a) A small European herring (Clupea sprattus) closely allied to the common herring and the pilchard; -- called also garvie. The name is also applied to small herring of different kinds. (b) A California surf-fish (Rhacochilus toxotes); -- called also alfione, and perch. Sprat borer (Zoöl.), the red-throated diver; -- so called from its fondness for sprats. See Diver. -- Sprat loon. (Zoöl.) (a) The young of the great northern diver. [Prov. Eng.] (b) The red-throated diver. See Diver. -- Sprat mew (Zoöl.), the kittiwake gull.