BOSTON (AP) – After U.S. Navy SEALs killed three men holding an American captain hostage in the Gulf of Aden, some Somali pirates vowed retaliation, saying they would target U.S. ships in the area.

But roughly a month after pirates seized the Maersk Alabama, there have been no further attacks against American boats or their crews.

And maritime experts believe it’s unlikely pirates will succeed again anytime soon because there are so few U.S. ships in the Gulf of Aden – as few as one out of the 70-80 ships in the Gulf of Aden each day – and because increased attention by the United States makes any attack especially risky.

Still, the threat of pirates is a constant for any ship in the gulf, which links the Suez Canal and the Red Sea to the Indian Ocean.

There were at least 84 pirate attacks in the first quarter this year, according to the International Maritime Bureau, and about 250 crew members remain in Somali captivity aboard 19 hijacked vessels.

American ships make up a small percentage of the world’s fleets. Even U.S. companies that rely on trade in the Gulf of Aden often use ships under foreign flags, in part because foreign regulations can be less restrictive than U.S. rules and because it’s less expensive to hire non-American crews and to build the ships outside of the United States.

“The biggest reason is it’s much more economical to operate those ships with other crews than U.S. citizens,” said Douglas J. Mavrinac, head of maritime research at investment firm Jefferies & Co.

U.S. laws require companies receiving government contracts to mostly use domestic crews and ships, so of the few American ships in the waters off the African coast, most carry either military or humanitarian goods. Both the Maersk Alabama and the Liberty Sun, which was violently attacked April 14 by pirates who fled before the U.S. Navy arrived to help, were carrying aid to African countries.

The Liberty Sun is operated by Liberty Maritime Corp., based in Lake Success, N.Y.; the Maersk Alabama is managed by Norfolk, Va.-based Maersk Lines Limited.

Maersk Alabama Capt. Richard Murphy, of Underhill, Vt., was held hostage on a lifeboat for five days and was freed when U.S. Navy snipers killed three of his captors. His second-in-command and fellow Massachusetts Maritime Academy graduate, Capt. Shane Murphy, of Seekonk, Mass., then took control of the ship.

After the rescue, some Somali pirates vowed retaliation. A pirate whose gang went after the Liberty Sun said the group was targeting U.S. ships and would “slaughter” Americans.

But such threats only make future attacks more difficult because of increased awareness and action from the U.S. military and government, said Donald Frost, publications editor for Connecticut Maritime Association, the country’s largest shipping trade association.

“To my mind, if you want to clean up the piracy issue, the best thing they can do is do something stupid, like declare open bounty on American ships,” Frost said.

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