Cameco (CCJ) traded roughly three times average volume, close to 4 million shares, during the October 21st session. On the 20th it moved over 6 million shares. What triggered the large volume spike?
Most point to a recommendation by Jon Najarian on CNBC. He claims that the option activity on Cameco represents a ‘tell’ and that the stock should be moving higher based on in-the-know institutional investors.

Note the large price and volume movement on the 20th and 21st.
At least short-term options movement supports Najarian’s claim, as the call to put ratio is close to 4-1 for the front month November contract.