A canola protein isolate useful in aquaculture is formed by a procedure in which canola oil seed meal is extracted to cause solubilization of protein in the canola oil seed meal to form an aqueous protein solution having a protein content of about 5 to about 40 g/L and a pH of about 5 to about 6.8. After separation of the aqueous protein solution from the residual canola oil seed meal, the protein concentration is increased to at least about 50 g/L while maintaining the ionic strength substantially constant by using a selective membrane technique. The concentrated protein solution is dried to provide a canola protein isolate having a protein content of at least about 90 wt % (N.times.6.25) d.b.