Yes, that is a small Sturgeon by just about any standard. When you can see them from 150+ feet above the water near the outflow of a Dam in South Dakota, you know they can get huge!
By my estimation, the Sturgeon I have seen at Dam sites were at least 10 feet long, if not bigger on average.
They can get as big as 20 feet long and ~1800 pounds!
The all-freshwater lake sturgeon is much smaller. US record is about 240 pounds.
The Fraser River is home to one of the largest populations of sturgeon in the world. For those of you that are not familiar with this species of fish, here are some quick facts:
Length: in excess of 14 feet
Weight: in excess of 1000lbs.
Life span: in excess of 100 years
Average annual growth: a couple of inches
Length of existence: over two hundred million years