They call it 'Cajun coral.' Louisiana anglers may soon call it a fishing spot.

Four and a half miles north of Grand Isle, large cranes dropped bulbous gray blobs of concrete into Barataria Bay on Wednesday morning. The lumpy structures will become a new habitat for sport fish and smaller organisms, after the removal of a decommissioned oil rig last year disrupted the wildlife habitat and the local fishing economy. The new artificial coral reef will cover 10,000 square feet, spanning four areas in a 10-acre region and consisting of more than 500 individual structures. Dubbed “Cajun coral,” the reef was the result of...