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Secrets of the Stomach

By: Melissa Schneider / Published: Sep 16,  2014

DNA analysis to reveal what lionfish eat 

Invasive lionfish in the Gulf of Mexico grow quickly and have voracious appetites. A research team out of Dauphin Island Sea Lab is using Sea Grant funding to determine exactly what they are eating on artificial and natural reefs.

The lionfish invasion in the northern Gulf of Mexico is in its early stages. However, research is already showing observed shifts in reef fish community, size and trophic (feeding/nutrition) structure. A team of scientists at the Dauphin Island Sea Lab is studying how lionfish are affecting reef fish communities.

In this Sea Grant study, Kristen Dahl, a University of South Alabama (USA) Ph.D. student at Dauphin Island Sea Lab, is using DNA barcoding to identify unidentifiable stomach contents of lionfish captured on both artificial and natural reefs.

Determining what lionfish eat will allow researchers to learn more about how they are affecting the food web, according to USA Professor Will Patterson, who is leading the grant.

Lionfish may be affecting reef systems in one of three ways. They may be directly consuming native reef fishes; they may be competing with native fish for food; or their presence on reefs may be changing what species are found on the reefs, he said. How lionfish affect populations of other fish may be important factors in fisheries and ecosystem management decisions.

This project continues earlier research that looked at stomach contents of lionfish. In that study, scientists worked to identify visible and identifiable prey found in the stomachs of lionfish. In their very early stages, lionfish eat small fish and invertebrates, such as small crab and shrimp. As they get bigger, they almost exclusively eat fish. But, researchers have found that lionfish on artificial reefs eat more invertebrates than those on natural reefs. They were surprised to find that lionfish ate fish that are not found on reefs, Patterson said. The discovery of bottom-dwelling searobins, flounders and lizardfishes in lionfish stomachs may indicate that lionfish are traveling off the reefs to find food.

Dahl is extracting DNA from unidentifiable prey items found in lionfish stomach samples that were collected by divers with spears in the northern Gulf of Mexico in 2013 and 2014. Forty-three percent of prey items were too digested to identify by eye. She is preparing these 762 samples for DNA barcoding analysis, thus species identification. Additional samples will be collected, prepared and analyzed this winter.

The technique Dahl is using to identify the muscle tissue of prey items is known as cytochrome C oxidase subunit I (COI) barcoding.

The barcode, once read in a genetics lab, will identify the species of the stomach contents of the fish.

“There’s a gene that is unique to species,” Patterson said. “There is a short region in the DNA that is called a barcode. This is the species’ signature.”

The study is part of ongoing research on the non-native species whose population is growing in the Gulf of Mexico.

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