Several stocks are making big moves this morning on very heavy volume. The big movers include Pacific Ethanol, Inc. (NASDAQ: PEIX), Western Digital Corp. (NYSE: WDC), Rubicon Minerals Corp. (AMEX: RBY), Research in Motion Ltd. (NASDAQ: RIMM), Big Lots Inc. (NYSE: BIG), and Enbridge Energy Partners L.P. (NYSE: EEP).

Pacific Ethanol shares have traded more than half their average daily volume in the first 30 minutes of trading this morning. Shares are up more than 15%, at $1.56 in a 52-week range of $0.25-$7.98. The company has regained compliance with Nasdaq listing requirements and has increased ownership of its four ethanol production plants to 27%.

Western Digital shares are up more than 13%, at $33.08 in a 52-week range of $22.64-$41.87. Volume in the first half-hour of trading is already more than half the daily average. The disk drive maker said this morning that it has re-started production at one of its Thailand plants that had been shuttered by the massive October flooding. More coverage here.

Rubicon Minerals is up more than 12.5%, at $4.11 in a 52-week range of $2.87-$6.09. Volume is already more than double the daily average. The junior gold miner has been considered a good takeover candidate ever since Agnico-Eagle Mines Ltd. (NYSE: AEM) pumped $70 million into Rubicon last summer. The price of gold has risen since then, and Rubicon continues to look good.

Research in Motion is down nearly -9%, at $16.97 in a 52-week range of $15.98-$70.54. Volume has already surpassed the daily average of 22.7 million shares. The smartphone maker announced this morning that it would take a $485 million writedown on its inventory of PlayBook tablets. RIM also lowered quarterly and full-year guidance. More details here.

Big Lots’ shares are down nearly -9%, at $36.20, in a 52-week range of $27.82-$44.44. Volume is already nearly double the daily average of about 1.4 million shares. The discounter reported disappointing third-quarter earnings this morning.

Enbridge Energy Partners’ shares are down about -4.5%, at $30.55 in a 52-week range of $19.01-$34.58. Volume is already five times the daily average. The oil & gas midstream company has priced an offering of 8.5 million common units at $30.85, about -4% below yesterday’s closing price.