Of all the alien species found in Maltese seas in a century, half have been spotted in the last 14 years, according to a recent stocktaking exercise.

But the expansion of the Suez Canal to increase sea traffic could double the extent of this problem, according to Patrick J. Schembri, professor of biology at the University of Malta.

Prof. Schembri has just concluded a review of non-native marine species in Maltese waters. Between 1900 and 2014, there were 61 confirmed alien species around the islands. It is probable that most arrived through boating or shipping.

Molluscs and seaweed also attach themselves to the hulls of boats or ships, or are ripped off the bottom and carried by their anchors.

In other cases, the eggs and larvae of fish and other marine organisms are trapped in the vessels’ ballast water and discharged in Maltese seas when the water is drained.

According to the updated survey of alien species, 30 of the records were made since the turn of the millennium – an all-time high

When more ships arrive, more species are brought over.

Since the vessels travel faster, as they now have ample space in the Suez Canal, these species will have a bigger chance of surviving the trip, Prof. Schembri said. The Suez Canal expansion was inaugurated yesterday by the Egyptian government.

Prof. Schembri is one of 200 scientists from 25 countries who last December wrote an open letter to bring to the public’s and politicians’ attention the threat of invasion by alien species being posed by the expansion of the canal.

A Sphoeroides pachygaster, one of the many species of alien fish finding a new home in the Mediterranean.

Today, the number of signa­tories has reached over 500 scientists from 40 countries.

According to the updated survey of alien species, 30 of the records were made since the turn of the millennium – an all-time high.

Prof. Schembri said the increase in alien species is a symptom of changes in the sea, in particular the warming trend of the Mediterranean.

The higher the temperature of the sea, the higher the likelihood of survival of tropical and sub-tropical species.

Often, the colonisation of alien species is a threat to indigenous marine life, as it can modify their habitat, introduce new parasites and the new species can compete with the native species for resources.

One such example could be the threat of some alien seaweed replacing the local seagrass that provides refuge to indigenous fish. A change in the fish’s habitat could lead to a reduction in indigenous marine species.

The introduction of alien species could also have a direct impact on the human species, as some of these new marine species are toxic.

For over a decade, the Marine Ecology Research Group, at the Department of Biology of the University of Malta, has been at the forefront in documenting the arrival of newcomers and monitoring these populations.

While some species have been spotted only once or twice and do not represent an ecological threat, others have settled in our waters and their population has grown rapidly.

Julian Evans, Jacqueline Barbara and Prof. Schembri, from the Marine Ecology Research Group, carried out an extensive survey of published records, unpublished reports and their own sightings.