Picturesque Croatia is one of Europe's many tourism hotspots. It's where Game of Thrones was filmed, known for its beautiful mountains, gorgeous Mediterranean beaches, old towns, seafood.But there's an unwelcome addition to the seafood that hasn't gone down well there: blue crabs. Atlantic blue crabs, which are an iconic food item across the American eastern seaboard, cropped up in Croatia as an invasive species about 20 years ago.And now, the locals say the crabs are wiping out their own food delicacy: a type of eel.Branko Glamuzina is a professor of aquaculture at Croatia's Dubrovnik University."The blue crab showed up sporadically, but around 2016 they appeared in big numbers. And then a need arose to catch them commercially, and a need to control them, because they do huge damage to the fish and shellfish population. They're omnivores and eat everything. In 2016 there were the first serious catches of them. We caught around ten to 20,000."The Neretva river eel was already in decline due to loss of their habitat, but the crabs have dealt a major blow, if not the final blow. The crabs have upset the food chain for the eels.Glamuzina says about 50 years ago the local fishermen would catch about 150 tons of eels annually. Now it's only 10 tons.Making matters worse: Croatians simply don't want to eat the crabs, either. Pavo Jerkovic is a restaurant owner on the river."It will never become part of our cuisine because it's too alien of a species to us.""As far as I know, no restaurant or tavern in the Neretva area has offered it yet."Glamuzina, the professor, says some crabs might be sold to the big luxury hotels for foreign tourists, but there isn't enough to make exporting it financially viable.