More than 900 non-indigenous species have already been identified in the Mediterranean Sea. And the number is only expected to increase.

Climate change is helping non-native species move further north in the Mediterranean as water temperatures rise.

As they spread, so does concern about their effect on marine ecosystems and the local fishing communities whose livelihoods depend on them.

"The majority of these species may have a negative impact on the ecosystem since they could occupy the ecological niche of the indigenous species," said Marouene Bdioui, a researcher at Tunisia's National Institute of Marine Sciences and Technologies.