Do you ever wonder if there's something we could do to make sure an animal doesn't become endangered? I'm Daniela Calcagnotto, and that's exactly what I'm trying to figure out.

I study a species of fish called the pacu. These fish are close vegetarian relatives of the meat-eating piranha. They are found in several rivers in South America. They can grow to be as heavy as a human kid - that's about 50 pounds! The pacu is very important to the economy of many communities. Recently the wild populations have been overfished and their numbers are decreasing.

The Brazilian government approved a project to study the pacu populations to see how the fish vary from river to river. As a first step, I took little pieces of fin from various fish and removed DNA. Now, I am comparing the DNA to see how genetically different, or diverse, the populations are. Scientists need this information to breed fish in fish farms. They want the farm populations to have the same genetic diversity as the wild populations. If the fish become endangered, we can then help the populations grow again. We can gradually move the fish from the breeding place to the rivers.