Answer: sturgeon

AnswerCrossword Clue
STURGEONCaviar source
STURGEONOrigin of Russian caviar.
STURGEONSource of isinglass.
STURGEONSource of caviar.
STURGEON"Needs no urgin'" according to Nash.
STURGEONMedical specialist catching true fish (8)
STURGEONFish that's a source of caviar
sturgeonan edible fish