Something fishy about river Grass Carp

A grass carp was pulled out of the Hudson River earlier this summer.

What is most worrisome to Ward Stone about that is that the female fish was fertile.

Stone, the state wildlife pathologist for the Department of Environmental Conservation, was shocked to see a 70.3-pound female grass carp that was full of eggs.

The fish was found at the Henry Hudson Park in the town of Bethlehem.

Grass carp are native to Siberia and northern China.
"I was halted by its size," Stone said. "I looked at the chromosomes and it was diploid. It was shocking because the fish is supposed to be triploid, which means it’s not fertile. It was full of eggs. And that is not normal."

The process for producing triploid fish involves shocking eggs with rapid change in temperature. The young are supposed to be tested before being sold.

What is worrisome about the finding is that there could possibly be a male fish that is also fertile and spawning could be taking place.

Grass carp fish eat a lot of the vegetation that a lot of native fish in this area hide in and also use for food.
"There is a good chance there is a male," Stone said. "We’ll have to check for little ones. We’ll watch the river for any small-size grass carp. If they are successfully spawning, that is not a good thing."

It also presents other dangers.
"Like any amphibians or reptiles that come into places," he added, "they can take hold and introduce new diseases.
"It was an invasive species," Stone said. "As we keep becoming a global economy, a lot of things arrive alive and become invasive species. That has big ecological ramifications. There are a lot of species that we can get globally."

Stone said that the fish that he looked at had been in the Hudson River for a long time to be the size that it was.

Grass carp, Stone said, are mostly used locally for people who own ponds.
"People buy them locally and put them in their ponds," he said. "They eat the vegetation in the pond. The ones that are for sale are sterile, in theory anyway.
"This fish could have escaped from some pond into a stream and gotten to the river," Stone said. "And then it grew to that size."

Stone said that the fish could have been bought at a market without the person knowing it was fertile or not. Buyers have to be careful to make sure a fish like that is infertile.
"You can go to a store and get a wide variety of fish," Stone said, "including grass carp."

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