Asian tiger prawn watch continues in Louisiana

Like a science fiction mutation of a normal shrimp, the Asian tiger prawn dwarfs its Gulf of Mexico brown and white shrimp cousins in size and appetite.

That’s why the state Department of Wildlife and Fisheries is once again reminding fishermen to report any sightings of this invasive species, which was first caught in Louisiana waters in 2007. Typically, these larger prawns start showing up in nets during the fall while the white shrimp are being caught along the coast.

The Asian tiger prawn has been showing along the East Coast before inching toward Louisiana.

In Louisiana, a single prawn was caught by a fisherman in Vermilion Bay in 2007, and for the next couple of years, the state got a handful of reports each year. That changed in 2011 when the state started getting 70 to 100 reports annually of the prawns from all of the state’s estuaries.

“Really, over the last few years, it’s been about static,” said Rob Bourgeois, biologist and invasive species coordinator with the state Department of Wildlife and Fisheries.

Other than the fact that it’s in Louisiana waters now, there isn’t a lot known about just how large the prawn population is, where they breed, if the population is growing or things seem to be stabilizing.

“It’s hard to separate if that’s better reporting or it’s a bigger population,” he said of the increase in reports the department started getting three years ago.

Most of the prawns that have been caught in Louisiana, and around the Gulf Coast, have been in the 7- to 8-inch size, he said. One thing fishermen haven’t been catching or reporting is juvenile Asian tiger prawns, which leaves open the question of where do all the small prawns spend their time while they’re growing, he said.

“We’ve never caught any small ones,” Bourgeois said. “So we’re not really sure where they go or what they do.”

A concern is that, if the population of this prawn starts to explode, it will compete with native brown and white shrimp for food and habitat.

“Tiger shrimp grow fast,” he said. “And because they grow so fast and so large they need more food.”

So far, it doesn’t appear that has happened, and it may never happen, Bourgeois said.

“We don’t know yet,” he said. “We really don’t know what the impact will be, if any.”

How the prawn, which is native to the waters around Indonesia, got introduced into United States water is still being investigated, whether it was from released ship ballast waters or the result of a release from an aquaculture industry.

“We don’t know. It’s probably a mixture of all of those,” he said.

What is known is that the Asian tiger prawn is out there in the water somewhere and there’s little that people can do about it.

“Being a marine species, the only thing you can do is catch them and eat them,” Bourgeois said.

Asian tiger prawn sightings should be reported to Bourgeois at rbourgeois@wlf.la.gov or (225) 765-0765, or Martin Bourgeois at mbourgeois@wlf.la.gov or (985) 594-4130, with the date, location, size of capture and photos, if possible.

Follow Amy Wold on Twitter, @awold10.