The alien rabbitfish population has “exploded” in numbers, as Malta’s waters warm up rapidly, reaching temperatures of more than 30°C by mid-July.

The fish, which has venomous spines, is now so common that local fishermen have named it ‘qawsalla’ (rainbow) due to its variable colouration, according to marine biologist Alan Deidun.

Also called the dusky spinefoot, the rabbitfish is a native of the Red Sea and has been present in Maltese waters for about 15 years.

Previously, the population was controlled by the weather. They could not survive the winter due to low winter sea temperatures.

But now that Maltese waters are warming up, this alien species has made itself at home.

“Over the past two years the numbers have exploded,” Deidun said.

In fact, he said, the Spot the Alien Fish citizen science campaign is working with Ambjent Malta to create a cookbook on how to cook alien species, including the rabbitfish, as a means of controlling their population growth.

The Red Sea native has been present in Maltese waters for about 15 years.

The rabbitfish, he said, can be cooked and eaten but its venomous spines must first be removed.

Deidun explained that the Mediterranean is warming up at a much faster rate than the global oceans.

Maltese waters reached temperatures of 31.2°C last week, quoting data collected by his colleague Adam Gauci, from the Oceanography Malta Research Group, who manages the marine monitoring network.

Usually, such temperatures are reached in August. 

In 2022, the waters reached 30°C by the end of July.

“It is happening earlier and earlier.  These warmer waters are attracting species from the Eastern Mediterranean to the West and North,” he said.

These new species compete with local ones

“Any fast change in the natural system is cause for concern as indigenous species do not have time to adapt,” he said.

The rabbitfish is not the only species making its way to Maltese waters: another is the invasive blue swimmer crab that eats practically everything, including fishing nets.

“These new species compete with local ones,” Deidun said, adding that the recent spotting of a monk seal might also be due to warmer sea temperatures that could also increase the turtle nests on the island.

The increasing population of the rabbitfish is a threat to the local salema, or xilpa fish, he said. Other alien species, like the lionfish, are predicted to enter Maltese waters as they have already been spotted in Tunisia and Sicily.