The Collaborative International Dictionary of English v.0.48:

Upokororo \U`po*ko*ro"ro\, n. [From the native Maori name.]
   (Zool.)
   An edible fresh-water New Zealand fish (Prototroctes
   oxyrhynchus) of the family Haplochitonidae. In general
   appearance and habits, it resembles the northern lake
   whitefishes and trout. Called also grayling.
   [1913 Webster]