As the 115-foot Research Vessel Weatherbird II rolled in 4-foot seas 120 miles west of Tampa Bay, the call went out:

“Fish on.”

Excitement was tangible; scientists hauled the 300-pound monofilament line, working the fish to the surface of the startlingly blue Gulf of Mexico.

Suddenly, it was visible, gray and white with vertical bars: tiger shark, the first fish caught on a six-day cruise, during which a team of 12 scientists would take samples from a variety of fish species to be tested for contaminants from the BP oil spill, which lasted from April 20 to Aug. 4, 2010.

A lot of research has been done on the immediate effects of the spill, data from this cruise will be used to examine the long-term effects.