NEW YORK ( TheStreet) -- Oil tanker stocks set a raft of new 52-week highs Monday as investors continued to pour into the sector on optimism about economic recovery and the resulting need for OPEC to hike crude production.

Those ideas were reinforced by Jeffries & Co. analyst Douglas Mavrinac, who upgraded the tanker sector of the shipping industry to buy from hold on Monday -- his first sector-wide buy rating since 2006. The upgrade follows a similar call last week by Omar Nokta, an analyst at Dahlman Rose in New York.

Over the last month, a shift in sentiment on tanker stocks appears to have overtaken the market. One hedge fund trader who had been short tanker shares as late as December gradually shifted his position until he went maximum long only a week ago. The northward trend in shares of those companies that haul crude oil across the oceans has probably also caused a fair amount of short covering: as of Dec. 15, almost 25% of Overseas Shipholding's ( OSG) float was in the hands of short sellers, for example.

Even as Mavrinac made his call, spot rates for Arabian Gulf Very Large Crude Carriers, or VLCCs, shot as high as $70,000 a day Monday, almost twice as much as a week ago.

Mavrinac was a bit more discerning than his general bullish call would otherwise imply. He favors the shares of tanker companies with more than 50% of their fleets on the spot market. Those companies with fewer ships tied up in long-term charter contracts will benefit that much more from the rising rates expected by Mavrinac over the next 12 months.

"This is a longer term call," Mavrinac said in a phone conversation. "This is for guys that can afford to look through that trough." He noted that tanker rates (and tanker share prices) will likely remain choppy over the next few months as the Northern Hemisphere's uncommonly frigid winter eases into spring and as ongoing contango trades eventually unwind, turning loose onto the market those ships that traders had used as floating storage for their crude-oil positions. Both circumstances would lead to weaker rates over the short term.

But, according to Mavrinac and others, the longer-term fundamentals look strong, with global economic recovery leading to decreased crude inventories, leading to an OPEC decision to open the spigots, leading to increased demand for tanker transport, leading to climbing tanker shipping rates.

"The sell side still hates" tanker stocks, Mavrinac said. "But when OPEC increases production, people are gonna herd up to buy them."

He foresees a series of "outsized gains" as tanker companies post strong quarterly profits. "It'll be a beat-and-raise type of environment."

For the analyst, three names stood out among those companies highly leveraged to the spot market : Nordic American Tanker ( NAT), Overseas Shipholding and Frontline ( FRO), all of which he upgraded to buy from underperform. Nordic, for example, has 12 of its 13 vessels on the spot market, while Overseas Shipholding and Frontline have two-thirds of their fleets exposed there.

Shares of Teekay Corp. ( TK) led the advancers Monday, gaining 7.7% to $26.87. The stock touched a new 52-week high of $27.14 intraday.

Frontline rose 5.6% to $33.98, Overseas Shipholding was up 5.5% to $51.39, and Ship Financial ( SFL) added 3.5% to $15.48. All three stocks set fresh 52-week highs during Monday's session.

Elsewhere, Nordic American rose 4% to $33.98; General Maritime ( GMR) gained 2.7% to $8.41, and Tsakos Energy ( TNP) jumped 6.3% to $17.62.

-- Written by Scott Eden in New York

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Scott Eden has covered business -- both large and small -- for more than a decade. Prior to joining TheStreet.com, he worked as a features reporter for Dealmaker and Trader Monthly magazines. Before that, he wrote for the Chicago Reader, that city's weekly paper. Early in his career, he was a staff reporter at the Dow Jones News Service. His reporting has appeared in The Wall Street Journal, Men's Journal, the St. Petersburg (Fla.) Times, and the Believer magazine, among other publications. He's also the author of Touchdown Jesus (Simon & Schuster, 2005), a nonfiction book about Notre Dame football fans and the business and politics of big-time college sports. He has degrees from Notre Dame and Washington University in St. Louis.