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Testing the Waters for Invasive Species: Non-native Shrimp Threaten Local Ecosystems

By: James M. O'Neill/The Record
06/25/2014, 11:12 AM

College students stood on a floating dock in the Hackensack River recently and used long-handled nets to scoop shrimp out of the murky water. The shrimp were not for grilling.

These were small Grass shrimp, an inch or two long, native to the Hackensack. The students want to see how many live in the water here, and whether the river has been invaded by several non-native species of shrimp that have started to appear in coastal waters from Boston to the Chesapeake.

On this day, their nets collected only native shrimp.

The students are working with James T. Carlton, a marine sciences professor at Williams College and director of the Williams-Mystic Program, a maritime studies program run by Williams and Mystic Seaport in Connecticut.

Carlton will spend early summer collecting shrimp samples at coastal sites from New Jersey to Maine. He will repeat the process in late summer, then continue each year at the same locations to produce a timeline of data. He is hoping to map the proliferation and range of the Japanese shrimp and the Baltic prawn, two invasive species that have been observed on the East Coast.

"We want to see how abundant the invasive shrimp are here and what impact they might have on the native shrimp," Carlton said. "Depending on how abundant they are, they could depress the native shrimp populations."

In some cases, invasive species can defeat native shrimp in the competition for food, disrupting the local ecosystem. "It can create a cascade effect," Carlton said.

The native species are a key food source for local fish and other marine life, but the invasive species might not be as appealing to fish – leaving the invasives with no natural predator to keep their numbers in check.

"Climate change will also play a role," Carlton said. "As the coastal waters warm up, it will facilitate more abundant populations of the invasives, since they originate in warmer water climates."

His students took shrimp samples in Tuckerton, along Little Egg Harbor in Ocean County; Red Bank, on the Navesink River in Monmouth County; Liberty State Park in Jersey City; and on the Hackensack at River Barge Park in Carlstadt. Carlton's research is funded by the National Sea Grant Program.

Japanese shrimp can grow to 3 inches – a third longer than native Grass shrimp. They were first identified on the East Coast in 2001, in the Bronx River. They have since spread north to Boston and south to Chesapeake Bay.

Lauren Bergey, a marine biologist at Centenary College in Hackettstown, first spotted some of the invasive Japanese shrimp in Red Bank in 2012. She had heard Carlton speak about the invasives during an academic conference the previous year and decided to see if they had invaded New Jersey. She and some students checked a dozen locations along the coast and found Japanese shrimp in the dark water around boat dock pilings in Red Bank and Keyport.

Bergey said the invasive shrimp were likely introduced by ship ballast water released in one of the ports in New York Harbor or Newark Bay.

Bergey has since studied the behavior of the Japanese shrimp in lab tests. They don't appear to be any faster than native shrimp at avoiding predators such as blue crab and killifish. But Bergey found that the invasives can produce more offspring – they reproduce from May through August, while the native shrimp peak for about a month.

Carlton and his team are also looking for an invasive species from Europe, called Baltic prawn, which appeared near Boston in 2010 and were found a few weeks ago in Rhode Island's Narragansett Bay.

Carlton's students were precise in their collection method. They laid a measuring tape out on the dock and held the net about a foot and a half deep at a 45-degree angle as they dragged it through the water. Once the students lifted the net out of the water, they dumped the captured shrimp in clear plastic tubs of water. The translucent shrimp zipped around inside. Carlton said he could tell from their coloring – stripes along the body – and morphology that they were the native variety.

Once they had enough samples, the students placed the shrimp in sandwich-sized plastic bags. Later they would pour ethanol in the bags, to kill and preserve the shrimp so they could be studied at the lab back in Connecticut.

Andrea Dunchus, a Williams College senior from Kinnelon and a history major, took the one-semester Williams-Mystic program and liked it so much she signed on as a summer intern. "It's great – you get to work outside, and I row crew, so I love the water," Dunchus said. "It's cool to come back to New Jersey to do this."

Invasive shrimp species are a growing issue in United States. The Asian tiger shrimp, native to Pacific, Asian and Australian waters, are now found along the southeastern and Gulf coasts of the United States. Federal researchers are studying whether they can carry diseases that might affect native species, compete for the same food source, and even prey directly on native shrimp.

Carlton first grew interested in invasive species when he was 14 and lived near San Francisco Bay, which he discovered has all forms of invasive marine life – up to 300 different species of crabs, mollusks, worms and other species.

"Invasives have been a lifelong research endeavor," he said. "And they keep coming."College students stood on a floating dock in the Hackensack River recently and used long-handled nets to scoop shrimp out of the murky water. The shrimp were not for grilling.

These were small Grass shrimp, an inch or two long, native to the Hackensack. The students want to see how many live in the water here, and whether the river has been invaded by several non-native species of shrimp that have started to appear in coastal waters from Boston to the Chesapeake.

On this day, their nets collected only native shrimp.

The students are working with James T. Carlton, a marine sciences professor at Williams College and director of the Williams-Mystic Program, a maritime studies program run by Williams and Mystic Seaport in Connecticut.

Carlton will spend early summer collecting shrimp samples at coastal sites from New Jersey to Maine. He will repeat the process in late summer, then continue each year at the same locations to produce a timeline of data. He is hoping to map the proliferation and range of the Japanese shrimp and the Baltic prawn, two invasive species that have been observed on the East Coast.

"We want to see how abundant the invasive shrimp are here and what impact they might have on the native shrimp," Carlton said. "Depending on how abundant they are, they could depress the native shrimp populations."

In some cases, invasive species can defeat native shrimp in the competition for food, disrupting the local ecosystem. "It can create a cascade effect," Carlton said.

The native species are a key food source for local fish and other marine life, but the invasive species might not be as appealing to fish – leaving the invasives with no natural predator to keep their numbers in check.

"Climate change will also play a role," Carlton said. "As the coastal waters warm up, it will facilitate more abundant populations of the invasives, since they originate in warmer water climates."

His students took shrimp samples in Tuckerton, along Little Egg Harbor in Ocean County; Red Bank, on the Navesink River in Monmouth County; Liberty State Park in Jersey City; and on the Hackensack at River Barge Park in Carlstadt. Carlton's research is funded by the National Sea Grant Program.

Japanese shrimp can grow to 3 inches – a third longer than native Grass shrimp. They were first identified on the East Coast in 2001, in the Bronx River. They have since spread north to Boston and south to Chesapeake Bay.

Lauren Bergey, a marine biologist at Centenary College in Hackettstown, first spotted some of the invasive Japanese shrimp in Red Bank in 2012. She had heard Carlton speak about the invasives during an academic conference the previous year and decided to see if they had invaded New Jersey. She and some students checked a dozen locations along the coast and found Japanese shrimp in the dark water around boat dock pilings in Red Bank and Keyport.

Bergey said the invasive shrimp were likely introduced by ship ballast water released in one of the ports in New York Harbor or Newark Bay.

Bergey has since studied the behavior of the Japanese shrimp in lab tests. They don't appear to be any faster than native shrimp at avoiding predators such as blue crab and killifish. But Bergey found that the invasives can produce more offspring – they reproduce from May through August, while the native shrimp peak for about a month.

Carlton and his team are also looking for an invasive species from Europe, called Baltic prawn, which appeared near Boston in 2010 and were found a few weeks ago in Rhode Island's Narragansett Bay.

Carlton's students were precise in their collection method. They laid a measuring tape out on the dock and held the net about a foot and a half deep at a 45-degree angle as they dragged it through the water. Once the students lifted the net out of the water, they dumped the captured shrimp in clear plastic tubs of water. The translucent shrimp zipped around inside. Carlton said he could tell from their coloring – stripes along the body – and morphology that they were the native variety.

Once they had enough samples, the students placed the shrimp in sandwich-sized plastic bags. Later they would pour ethanol in the bags, to kill and preserve the shrimp so they could be studied at the lab back in Connecticut.

Andrea Dunchus, a Williams College senior from Kinnelon and a history major, took the one-semester Williams-Mystic program and liked it so much she signed on as a summer intern. "It's great – you get to work outside, and I row crew, so I love the water," Dunchus said. "It's cool to come back to New Jersey to do this."

Invasive shrimp species are a growing issue in United States. The Asian tiger shrimp, native to Pacific, Asian and Australian waters, are now found along the southeastern and Gulf coasts of the United States. Federal researchers are studying whether they can carry diseases that might affect native species, compete for the same food source, and even prey directly on native shrimp.

Carlton first grew interested in invasive species when he was 14 and lived near San Francisco Bay, which he discovered has all forms of invasive marine life – up to 300 different species of crabs, mollusks, worms and other species.

"Invasives have been a lifelong research endeavor," he said. "And they keep coming."