Tiger Shrimp gulf
Nearly 100 sightings of the giant tiger prawn have been reported in Louisiana waters in 2011, according to Houma Today, a big jump from the 25 to 30 reported in past years. Considering that some of the sightings numbered close to 100 individuals, there seems to be a growing population of the nonnative shrimp prowling Gulf waters.
This year, the U.S. Geological Survey received increasing reports of the species in Mississippi, Florida, Louisiana and Texas, marking the Lone Star State's first taste of the tiger prawn, reported the Houston Chronicle.
The invasive crustaceans can offer up to 13 inches and 11 ounces of deliciousness, which is why U.. farmers brought the prawns here from their home waters on the coasts of Australia, South East Asia, South Asia and East Africa.
The black and yellow striped prawns may have started their invasion after escaping from a aquaculture operation in South Carolina in 1988, noted the Houston Chronicle. Or they could have made their break after hurricanes Katrina and Rita in 2005.
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“There’s a certain unknown about what ecological impacts that something nonindigenous like this can have on the local environment,” said Marty Bourgeois, a biologist with the Louisiana Department of Wildlife and Fisheries, in Houma Today.
Tiger prawn are voracious predators and are known to harbor numerous diseases that could spread to white and brown shrimp, oysters, and crabs in the Gulf.There may be one way to lick this problem, literally. The Louisiana Department of Wildlife and Fisheries has advised fisherman that the prawns should not be thrown back into any waters other than a boiling soup pot.
“I haven’t had them myself, but I’ve been told they have a sweet flavor,” Bourgeois said.
Tiger prawns could join the list of invasive species humans seek to control by eating, like wild pigs, lionfish and nutria, noted Mother Nature Network.
The tiger prawn also fetches a higher price than many other shrimp. But Leslie Hartman, of the Texas Parks and Wildlife Department, is skeptical the economic value will outweigh the damage to the native shrimp population.
"It could be another crop, but at the expense of our native crop," Hartman said in the Houston Chronicle.
For right now, researchers are trying to track down the source of the prawns using genetic evidence.
“We’re collecting them, and we’ve got some researchers looking at the genetics,” Bourgeois said. “It may help explain if they’re spawning here or if they’re riding the current into the area somehow.”
Only adults have been found in Louisiana waters, so researchers hope they may be breeding farther south and migrating north.
Lionfish and black tiger shrimp are only two of more than 40 species of non-indigenous sea life known to be spreading through the Gulf of Mexico from their native waters, but they are seen by many resource experts as the most threatening. Lionfish have been a growing problem in the South Atlantic Ocean and Caribbean Oceans Sea for most of a decade, but black tiger shrimp are a relatively new phenomenon. A few were captured in the Gulf of Mexico each year beginning in 2006, but the numbers rose significantly in 2011. During this year, more than 60 of the shrimp were brought by shrimp boats to one dock alone in Louisiana and the first captures off Texas' coast were reported to the federal government. Three black tiger shrimp were caught in Aransas Bay, one was caught in Sabine Lake and one was caught in federal waters about 70 miles offshore from FreeportLionfish are strikingly colored, brightly striped and venomous fish that can quickly populate an area and decrease native populations through either eating them or chasing them away. Black tigers are the largest species of shrimp in the world. Females are slightly larger than males and can grow to an average of about a foot in length and weigh close to three-fourths of a pound. Black tiger shrimp eat the same types of food as native shrimp species, but as they grow they also eat their smaller cousins.
"The biggest concern we have is what are the ecological impacts of these invasive species?" says Dr. James Morris, an ecologist with the National Oceanic and Atmospheric Administration (NOAA) who has been working with lionfish for about 10 years and is now taking the lead in NOAA's efforts to study black tiger shrimp. "When you look across the history of invasive species, there have been some very extreme impacts that have resulted from invasions."
Invasive species often find themselves in foreign ecosystems devoid of the natural predators and diseases that kept their populations under control in their native ranges. Free of these challenges that plague native wildlife, invasive species can turn all of their energy toward feeding and reproducing. In some cases, the manner in which invasive species live can physically damage their adopted ecosystems to the point where it becomes poor habitat for native species.
Lionfish and black tiger shrimp, both native to the Indian and western Pacific Oceans, are noted for their aggressive feeding behaviors and hardiness — they can live in a wide range of water temperatures and salinities. These traits make them perfect, and dangerous, invaders.
The Texas Sea Grant College Program's Tony Reisinger spoke to the Brownsville-Port Isabel Shrimp Producers Association in early December about the growing number of black tiger captures in the Gulf of Mexico — perhaps as many as 1,000 this year including five that represent the first ever caught off the Texas coast.
Association members, who represent a fleet of 135 vessels that fish off Louisiana, Florida and Texas, were "extremely concerned to the point where they want to find out what the federal government will do about the black tiger shrimp," says Reisinger, Cameron County Coastal and Marine Resources Agent. "They are concerned about whether it will affect their livelihood."
Thus far, black tiger shrimp have left experts scratching their heads. No one seems to know where the shrimp came from, or what affect they will have on the three species of shrimp native to the Gulf of Mexico and, by extension, the $700 million shrimp fishing industry.
"We just don't know what the long term impacts are going to be," says Gary Graham, Texas Sea Grant's Fisheries Specialist. "I don't know whether these shrimp will establish themselves in the Gulf of Mexico or play themselves out, but I think they could become a more serious problem than anyone originally thought."
Black tiger shrimp are an aquacultured species in various places around the world, but their route to the Gulf remains uncertain pending genetic testing. There was an accidental release of black tigers from a research facility in South Carolina in 1988, but most of those animals were thought to have been caught by local fisherman by the early 1990s. No more tiger shrimp were reported caught until 2006. No aquaculture operation in the U.S. grows black tiger shrimp, but there have been reports of them being raised at sites in the Caribbean Sea. One popular theory holds that black tiger shrimp escaped into the sea from an aquaculture pond in the Caribbean that was breached by a hurricane in 2005. Others speculate that the shrimp hitched a ride from Asian to U.S. waters in the ballast tanks of ships.
Leslie Hartman, Matagorda Bay Ecosystem Leader with the Texas Parks and Wildlife Department, is part of a casually organized group of people from various resource management agencies around the Gulf and South Atlantic who have banded together to perform genetic testing on the black tiger shrimp being caught around the nation's coastline. She says the group has genetic material from the population of animals that escaped from the South Carolina facility in 1988 and will use it to determine if the growing U.S. population owes its lineage to the South Carolina escapees.
"We're trying to figure out where these animals came from," says Hartman. "If these are all genetically related back to the South Carolina shrimp, that tells us something about invasive species – that they will go into sort of a hiatus and then can re-surge. If the genetics show they are from different and unrelated populations, that tells us something else, like there was a second or third or fourth introduction. The more we understand about how invasive species spread, the more likely we are to intervene appropriately the next time."
Black tiger shrimp are a paradox among invasive species. On one hand they present the same problems as any other non-indigenous species. One of the biggest problems they pose is that they are susceptible to about 16 diseases — not all of them fatal — that can be transmitted to native shrimp and crabs, says Hartman.
"The potential impact is roughly similar to We just don't know what the long term impacts," she says. "They can put a hurt on the domestic shrimping and crabbing industries."
On the flip side, black tiger shrimp are susceptible to catching diseases carried by native shrimp. "Tiger shrimp are also active predators," she continues. "Our native shrimp are active scavengers. As an active predator that is twice the size of its compatriots, its favorite foods are shrimp, crab and small bivalves. The most commonly collected small bivalve in Texas waters is the oyster. So between the diseases it carries and it being an active predator, the black tiger prawn can be a big issue."
On the other hand, black tiger shrimp are a highly valuable commodity, although Reisinger said he has heard anecdotal reports that some shrimpers have thrown captured black tiger shrimp back into the Gulf of Mexico because they did not think they were a marketable species. The shrimp fetch a market price similar to native white shrimp and slightly more than native brown shrimp. As of early December, the largest black tiger shrimp were going for about $8.35 per pound on the New York Market.
One of the five black tiger shrimp caught in Texas waters was found in the net of a boat operated by Western Seafood fishing near the Clay Pile Bank, about 70 miles east southeast of Freeport, in about 180 feet of water in mid-November.
Western Seafood's general manager, Patrick Riley, says it appears black tiger shrimp are poised to become a fourth harvestable species in the Gulf, but he is not counting on them becoming a cash crop any time soon.
"I don't know how long it will take before the population grows enough to be economically viable," Riley says. "Picking up one to two shrimp a year on a couple of boats will not help."
Lionfish, too, are a marketable fish, but on a much smaller scale. They are best caught using traps or by spear gun and are considered a delicacy in Asia, but they have yet to gain popularity in the U.S.
Harvesting lionfish for the restaurant trade appears to be to be an effective method for controlling local population densities in the South Atlantic and Mexico, says Morris.
Lionfish were most likely introduced to the Gulf through the aquarium trade — either as an accidental or intentional release from an aquarium. They have established themselves in the south Atlantic and Caribbean, and they were reported for the first time near Texas in mid-2011 at the Flower Garden Banks National Marine Sanctuary, located about 100 miles off the Texas-Louisiana border. Another was reported about 19 miles off South Padre Island in September 2011.
Although they are known for pillaging coral reefs, lionfish can live just about anywhere except where there is barren sand beneath them.
"The Gulf of Mexico comprises a wide array of habitats and anywhere you find structure you will find lionfish," says Morris. "Oil rigs provide high relief piling structures and I believe lionfish will recruit to these habitats in high densities. We have already seen high densities of lionfish around bridge pilings along the East Coast."
People visiting the coast generally play in the surf zones, which usually have barren sandy bottom, so lionfish-human interactions are not likely. Most interaction happen when people snorkel or dive around reefs or other structures. There are some reports that lionfish have acted aggressively toward humans, but Morris downplays these stories saying they are isolated. Lionfish are "curious animals," he says. The lionfish carries an impressive arsenal of venomous spines but uses them almost exclusively as defensive weapons. In humans, a lionfish sting can cause vomiting, fever, sweating and, in a few cases, even death.
Lionfish, which can grow to the size of a small football, are relentless predators that feed on recreationally and economically important reef fish like juvenile red snapper and grouper, and algae-eating species like parrotfish that keep reefs clean and healthy.
"This is an example of a cascading impact," explains Morris. "Some people think this is happening in the Bahamas. An increase in algae leads to a decrease in coral biomass."
Lionfish are not the sole reason coral reefs are declining, adds Morris. The lionfish invasion comes on the heels of coral bleaching, increased pollution, overfishing and climate change, he says.
"The difference is the lionfish invasion is happening much more quickly than the other stressors," says Morris. " In less than a decade, we've had a fish that has colonized basically the entire temperate and tropical Atlantic."
Once invasive species establish themselves, they are very difficult if not impossible to eradicate. As Hartman notes, "Prevention is the first defense to invasive species. Early detection is the second defense, and then you have to go into control and maintenance mode."
Pockrus, the owner of a 13-vessel shrimp fleet operating out of Brownsville, caught the 12-inch, 13-ounce specimen last week.
Pockrus said he’s been aware of the species for about three years but hadn’t seen one. Now, he has turned in two to marine and wildlife officials this season.
“I have another boat coming in with one on it now,” Pockrus said. “That makes the third one we’ve picked up.”
The Black Tiger shrimp is indigenous to the eastern coast of Africa. Its ranges to the Indo-Pacific region and south to Australia.
Black Tigers can grow to 13 inches and weigh as much as a pound. They are raised as a food source in many Asian countries.
The problem, said Tony Reisinger, a Texas AgriLife Extension Service agent for coastal and marine resources in South Texas, is the Black Tiger is extremely destructive toward native species and could have disastrous effects on the Gulf shrimp ecosystem.
“We are studying them now, and we think they have the ability to take over the feeding grounds and habitats of our native species,” Reisinger said. “They are very aggressive, and when their food source is extinguished, they feed off smaller shrimp and oysters as well.”
Since Hurricane Ike, the number of Galveston shrimpers has declined. That may explain why there hasn’t been a documented catch of the Black Tiger off Galveston Island.
But shrimpers have reported hauling them up in southern Texas for the first time this season. The Black Tigers also are being caught along the northern Gulf as close as western Louisiana.
Reisinger said he didn’t know how the species found its way into the Gulf, but the Nonindigenous Aquatic Species Division of the U.S. Geological Survey said it might have been by an accidental release from an aquaculture facility in South Carolina almost 25 years ago.
In 1988, an unknown number of Black Tiger shrimp got into the ocean off the Carolina coast. About a thousand of the shrimp were recovered, some as far away as St. Augustine, Fla.
Reisinger said that was one of several theories.
“After 1991, they just stopped showing up,” Reisinger said. “Then we started seeing them again in 2006. I believe it could be from ballast release (from ship’s tanks coming through the Gulf) or a release from a Caribbean facility during a hurricane or storm. That’s why it’s imperative we recover as many of these as possible to do genetic testing.”
There were no documented cases of a Black Tiger catch from 1999 to 2005.
Since 2006, there have been more than 180 documented cases from every coastal state from North Carolina south to Louisiana. This year, there have been eight cases from Texas.
The species no longer is raised commercially in the United States, although aquaculture facilities once operated in South Carolina, Alabama, Florida and Texas.
Reisinger said he believes the numbers were low because so many shrimpers might have hauled them in and released them because they thought they weren’t a marketable catch.
“I’ve had several tell me that was the case,” Reisinger said. “We’re spreading the word that we need them to freeze them and get them to us for study. Maybe we will trace them back to the South Carolina release. That will tell us a lot about this species.”
Reisinger said the biggest danger to the native species might not be predation but disease.
Pockrus said he didn’t know if the giant Black Tiger shrimp might someday replace the indigenous Gulf shrimp as a cash crop for fishermen.
“Maybe they could — I’m not sure what to think,” Pockrus said. “All I know is I believe they have the potential to forever change (the shrimp fishing industry) in the Gulf.”
Researchers from the U.S. Geological Survey and National Oceanic and Atmospheric Administration are working with state agencies from North Carolina to Texas to look into how this transplanted species from Indo-Pacific, Asian and Australian waters reached U.S. waters, and what the increase in sightings means for native species.
“We can confirm there was nearly a tenfold jump in reports of Asian tiger shrimp in 2011,” explained Pam Fuller, the USGS biologist who runs the agency’s Nonindigenous Aquatic Species database. “And they are probably even more prevalent than reports suggest, because the more fisherman and other locals become accustomed to seeing them, the less likely they are to report them.”
NOAA scientists are launching a research effort to understand more about the biology of these shrimp and how they may affect the ecology of native fisheries and coastal ecosystems. As with all non-native species, there are concerns over the potential for novel avenues of disease transmission and competition with native shrimp stocks, especially given the high growth rates and spawning rates compared with other species.
“The Asian tiger shrimp represents yet another potential marine invader capable of altering fragile marine ecosystems,” said NOAA marine ecologist James Morris. “Our efforts will include assessments of the biology and ecology of this non-native species and attempts to predict impacts to economically and ecologically important species of the Atlantic and Gulf of Mexico.”
Fuller’s team at USGS has been tracking reports of Asian tiger shrimp since they first came to the attention of marine scientists and resource managers in 1988, when nearly 300 of them were collected off the coasts of South Carolina, Georgia and Florida within three months. Scientists tracked the cause back to an isolated incident that accidentally caused an estimated 2,000 animals to be released from an aquaculture facility operating at that time in South Carolina.
It was not until 18 years later that reports of the non-native shrimp resurfaced. In 2006, a commercial shrimp fisherman caught a single adult male in Mississippi Sound near Dauphin Island, Ala. Within months, additional specimens were noted in North Carolina’s Pamlico Sound, Louisiana’s Vermilion Bay and other parts of Florida and the Carolinas. The species was later reported off the coasts of Georgia, Mississippi and Texas in 2008, 2009 and 2011, respectively.
Scientists have not yet officially deemed the Asian tiger shrimp “established” in U.S. waters, and no one is certain what triggered the recent round of sightings. With so many alternative theories about where these shrimp are coming from and only a handful of juveniles reported, it is hard for scientists to conclude whether they are breeding or simply being carried in by currents.To look for answers, USGS and NOAA scientists are examining shrimp collected from the Gulf and Atlantic coasts to look for subtle differences in their DNA, information that could offer valuable clues to their origins. This is the first look at the genetics of wild caught Asian tiger shrimp populations found in this part of the U.S., and may shed light on whether there are multiple sources.
“We’re going to start by searching for subtle differences in the DNA of Asian tiger shrimp found here – outside their native range –to see if we can learn more about how they got here,” said USGS geneticist Margaret Hunter, “If we find differences, the next step will be to fine-tune the analysis to determine whether they are breeding here, have multiple populations, or are carried in from outside areas.”
Anyone who sees one or more shrimp suspected to be an Asian tiger shrimp is asked to note the location and report the sighting to the USGS NAS database at http://nas.er.usgs.gov/SightingReport.aspx.
If possible, freeze a specimen to help confirm the identity and contribute to a tissue repository maintained by NOAA.
The USGS serves the nation by providing reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life.
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