Sulcis: hunting aliens from rivers and swamps

Imported by chance or introduced to be reared, the result does not change: biological invasions are considered among the main threats to the biodiversity of a territory. They are also one of the most serious disturbing factors in aquatic ecosystems, which are particularly vulnerable to the introduction of alien species that can compete with our own species and monitoring is necessary. The Province of Southern Sardinia has recently launched a project that provides for the control of three alien species known to be present on the island: the Louisiana shrimp, the marbled shrimp and the American marsh turtle in order to identify the areas of presence and prepare specific capture plans aimed at eradication. European legislation prohibits in any way the possession, sale and breeding of the forms present in the list of invasive "exotic" species.

Where is it

"In these days, Dr. Daniele Scarselli of the Agrofauna Srls company is on the field to start monitoring with the use of traps along some waterways in the area, where alien species have been reported", says Gianroberto Cani, manager of the environmental area of the Province. The activity is underway in the network of irrigation systems of Sanluri Stato, and in Furtei, in the Flumini Mannu area, where the American marsh turtle has recently been reported. Then we will proceed with the other basins: Sulcis and Sarrabus. In June, monitoring is planned in Carloforte, also in this case for the reporting of the “alien” turtle.

The species

The "killer shrimp" ( p rocambarus clarkii ) reaches 12.5 cm in length. The coloring of the adults is brown-red. Native to North America, it is present almost all over the world, having been introduced for aquaculture and ornamental purposes (the meat is good, but it can accumulate a series of toxic substances from the environment). In Sardinia it was reported for the first time in the Coghinas, in 2005. "The shrimp is one of the 100 most invasive species in the world - explains Stefania Peddio, biologist at the Department of Biomedical Sciences of the University of Cagliari - for its general eating behavior and opportunistic and for its resistance to changes in environmental parameters such as temperature, oxygen, salinity ».

Another shrimp, procambarus fallax f. virginalis , is recognizable because its body has a marbled design, has very small claws and reaches 13 cm in length. In 2019 the first report in Sardinia, in the Rio Mogoro in Morimenta. Later also in Sardara and Sanluri. It has ease of movement in the dense irrigation network that is present in that portion of Campidano. "The possibility of reproducing by parthenogenesis (the female generates new individuals without the male) contributes to its diffusion in the environment," says the scholar. Both shrimps cause a weakening of the riverbanks due to the deep excavation they carry out. In Sardinia there are sporadic reports of the European shrimp austropotamobius pallipes , which could therefore be disturbed by the presence of the two alien species.

The American pond turtle ( trachemys scripta elegans ) was intensively commercialized until the 1990s. It is recognized by the two red streaks on the sides of the head. Being difficult to manage, many adult specimens were released into waterways, with serious damage to biodiversity. The trachemys procreate uncontrollably and threaten the survival of our less aggressive European marsh turtle ( emys orbicularis ).

Joint actions

"In addition to the monitoring performed by the company, we have asked all fishermen's associations to report sightings of these species in order to prepare timely interventions and control the territory in areas potentially contaminated by alien species", concludes Cani. The reports of sightings can also be submitted by citizens using the form on the website of the Province or at aliene@agrofauna.it.

Giovanni Scanu