Count Asian tiger prawns as the latest invasive species posing a threat to U.S. commercial species. The non-native shellfish's presence is growing in Louisiana waters.

So far little is known how tiger prawns — which can get as long as 14 inches and weigh as much as 23 ounces — will affect the native brown, white and pink shrimp species, the Louisiana Department of Wildlife and Fisheries says. At present there is no evidence that the tiger prawns feed on the native shrimp, the department says, but it also notes it's unknown whether the tiger prawns would outcompete the native shrimp for food.

Tiger prawns were first noticed in Louisiana waters in August 2007 when a shrimper caught one in Vermilion Bay, the department says. Before the start of the 2011 fall inshore season, tiger prawn catches numbered fewer than 25, with none seen west of Vermilion Bay.

But reports of catches of the invasive species have grown since then, and the department says they've been spotted west of the bay, too. Hence, Louisiana shrimpers are being asked to report catches of tiger prawns to the department. (See contact info below.)

According to the department, it's not known exactly when and how the tiger prawns were introduced into Gulf of Mexico waters. Louisiana is a long way from the Indo-Pacific rim that the tiger prawns call home. They're caught in the wild, and many countries have tiger prawn aquaculture operations. A number of farm-raised tiger prawns escaped from an East Coast operation in 1988. Some 1,000 adult tiger prawns were later recaptured as far south as Cape Canaveral, Fla., the department says.

In September 2006, a shrimper caught a single adult male tiger prawn in Mississippi Sound near Dauphin Island, Ala., the department says. Reports of the shellfish's presence in Alabama and Mississippi waters have been increasing ever since.

Reports can help department biologists monitor tiger prawn distribution and relative abundance, and determine the possible presence of spawning populations.

Shrimpers are asked to contact Robert Bourgeois at [email protected] or (225) 765-0765 or Martin Bourgeois at [email protected] or (985) 594-4130 to report the date, location and size of Asian tiger prawns caught. They're encouraged to send photos of the non-native shrimp, too.

Photo: Louisiana Department of Wildlife and Fisheries. Tiger prawns have a dark body color and white banding along their heads and between segments of their tails. Yellow or red stripes are seen occasionally, too.