Definition from Wiktionary, the free dictionary
ウグイ (romaji ugui)
- the Japanese dace, also known as the big-scaled redfin: Tribolodon hakonensis, an edible fish in family Cyprinidae
Usage notes 
Although there are two possible kanji spellings, as with many less-common plant and animal names, this word is more often spelled in katakana.
Alternative forms 
- 丸太 (まるた, maruta)