6 Stocks Rising on Unusual Volume

NEW YORK (Stockpickr) -- Professional traders don't just look at a stock's price moves; they also look for big changes in volume.

Major moves in volume can signal unusual activity, such as insider buying or selling -- or buying or selling by "superinvestors."

Let's take a look at several stocks rising on unusual volume today. They are all recording volume in midday trading that is already at least 50% above their average trading volume for a full day.

>>5 Stocks Under $10 With Big Upside Potential

Rio Tinto

Rio Tinto is an international business involved in each stage of metal and mineral production. The stocks is trading up 22 cents, or 0.5%, at $48.29 in recent trading.

Volume:6.8 million

Average Volume: 3.8 million

Volume % Change: 78%

Rio, a holding in Ken Fisher's portfolio, shows up on a recent list of 6 Large-Cap Stocks to Consider.

Comtech Telecommunications

Comtech Telecommunications designs, develops, produces and markets innovative products, systems and services for advanced communications solutions. The stocks is trading up 65 cents, or 2.1%, to $31.55 in recent trading.

Volume: 708,300

Average Volume: 375,100

Volume % Change: 88.8%

Comtech, which has a C+ hold rating from TheStreet Ratings, was featured recently in "5 Heavily Shorted Stocks to Squeeze the Bears."

Stamps.com

Stamps.com is a provider of Internet-based postage solutions. Its customers use its service to mail and ship a number of mail pieces, including postcards, envelopes, flats and packages.. The stocks is trading up $1.96, or 8.2%, at $25.75 in recent trading.

Volume: 676,121

Average Volume: 274,000

Volume % Change: 146.8%

Scott Rothbort featured Stamps.com, which has a B buy rating from TheStreet Ratings, in "7 Top Stocks That Should Continue to Outperform."

GeoEye

GeoEye is a provider of imagery, imagery information products and image processing services. The stocks is up $1.82, or 6.1%, at $31.56 in recent trading.

Volume: 551,250

Average Volume: 230,600

Volume % Change: 139%

GeoEye is rated a C+ hold by TheStreet Ratings.

Golar LNG Partners

Golar LNG Partners is a limited partnership that owns and operates floating storage and regasification units and LNG carriers under long-term charters. The stock is trading up 29 cents, or 1.2%, at $24.28 in recent trading.

Volume: 222,066

Average Volume: 92,000

Volume % Change: 141.4%

Golar LNG is one of the top holdings of George Soros' Soros Fund Management, which initiated a new 1.2 million-share position in the most-recently reported quarter.

Servicesource International

Servicesource International provides service revenue management solutions that drive renewals of maintenance, support, and subscription agreements for technology companies. The stocks was up 90 cents, or 6.7%, at $14.25 in recent trading.

Volume: 2 million

Average Volume: 726,100

Volume % Change: 176.8%

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