The Collaborative International Dictionary
Roundfish
Roundfish \Round"fish\, n. (Zo["o]l.)
Any ordinary market fish, exclusive of flounders, sole, halibut, and other flatfishes.
A lake whitefish ( Coregonus quadrilateralis), less compressed than the common species. It is very abundant in British America and Alaska.
Wiktionary
roundfish
n. 1 Any fish that is not a flatfish. 2 (taxlink Prosopium cylindraceum species noshow=1), the (vern round whitefish pedia=1).