Aquatic invasive species – Data Information

Sessile AIS, particularly invasive tunicates (sea squirts), are detected and followed using settlement collectors. Collectors are made of three, 10 x 10 cm PVC plates, and a plastic plate to which three petri dishes are attached, all of which are threaded onto a rope. Sampling efforts are concentrated in sites with the highest risk of introduction of AIS, such as marinas, commercial and fishing harbors, and aquaculture sites. From June to October, in collaboration with Merinov and aquaculture farmers, a minimum of six collectors is installed at various sampling sites, attached to port infrastructures or anchorages, about one meter below the water surface.

Monitoring is carried out for three different periods:

  • Spring-summer: collector installed in June and removed in August;
  • Spring-autumn: collector installed in June and removed in October;
  • Summer-autumn: collector installed in August and removed in October.

When possible, temperature and salinity are measured during collector installation and recovery. At each collector recovery date, the percent cover of each AIS present on collectors is evaluated and assigned into one of six coverage categories:

Coverage class used for data collection Percent cover
(plate and petri dish)
Quantitative value retained for display
(median of class)
0 0 % 0 %
1 0-25 % 12,5 %
2 25-50 % 37,5 %
3 50-75 % 62,5 %
4 75-100 % 87,5 %
5 100 % 100 %

The display on the map, for each cell or point, corresponds to the average value of all the data contained therein. For example, if for a given station there are 12 recorded, the mapped value will be equal to the average of these 12 values.