Over the past year, by gathering information resulting from the hundreds of observations that have been submitted by citizens to NEMA, as well as the field work that we have been carrying out, some aspects of the population dynamics of the blue crab (Callinectes sapidus) are beginning to become evident in the Algarve.
During the summer months there were several reports of females with egg masses in the coastal zone. The migration of females from the estuaries to the more saline coastal areas to spawn, is well documented in the native zone of the species (West Atlantic), and the same seems to occur in the Algarve, at least in the months of August to October.
Female carrying a egg mass registered on September 10, 2019 in Ria Formosa.
Observation and photography by Duarte Barragão.
During the first months of 2021, we have already collected a significant number of juvenile individuals already in the middle estuary of the Guadiana, in areas with very low salinity.
In this case, it is also described in studies carried out in North America that the juveniles, after re-entering the estuaries soon after the larval phase, also begin migrations in the estuaries where they prefer the low salinity zones to grow. Later in adulthood, they eventually spread to areas closer to the mouth of the estuaries, as well as coastal areas.
We count on everyone so that whenever you capture or spot a blue crab, to send us a photograph, location, date of sighting, so that we can continue to get to know this species better! All observations already validated can be consulted at: https://www.biodiversity4all.org/projects/nemalgarve