Data Collection of Season 2021
on Marine Mammals and Marine Debris
Writtten By Liam van Walsum
Project Manaia’s 2021 season was very eventful with 24 dolphin sightings, 1 whale sighting and 459 garbage and debris sightings in 158 hours of travelling over 1250nm.
Research Vessel Independence travelled irregularly from the Northern tip of the Adriatic to the Southern Sicilian coast beginning on 3rd of May and ending on 07 September 2021.
In total this equates to a marine mammal encounter rate of 0.16 per hour travelled, and a garbage encounter rate 2.91 per hour. This final data point is significant, it means on average along the route of the Independence, visible garbage and debris was sighted once every 20 minutes at sea. This is just visible garbage, with garbage and debris below the surface, and microplastics were not spotted and therefore not counted, implicating a far greater problem.
Marine Debris Observations
The map below shows each garbage and debris sighting in 2021 while underway, with sightings closely following the boat route. However some large gaps in sightings occur between Korčula Island (Southeast of Split) and just Northwest of Dubrovnik, Dubrovnik and Brindisi (Southeast of Bari), and the north eastern half of the gulf of Taranto.
The circles shown are hotspots of garbage where the density of garbage sightings was 50% higher than the rest of the route. Unsurprisingly these hotspots occurred around major cities such as Palermo, Zadar, and Šibenik, the latter of which is a smaller city but sits at the mouth of a channel flowing into lake Prokljan on the shores of which sit more cities that contribute to this pollution.
Marine Mammal Observations
Finally, let’s revisit the dolphins and whales spotted this year. Project Manaia has been lucky enough to sight and acoustically record Risso’s dolphins, a distinct but rare deep-diving species in the Mediterranean, on the crossing of the Adriatic. The single whale sighting was most likely a Fin whale, given its location in the Southern Adriatic and other species common to the area are smaller and do not commonly raise their tail flukes above the water when diving.
The map below shows the locations of sightings in the 2021 season, as well as hotspots of cetacean sightings. The colour of each bubble represents the species of the sighting, and the size of the bubble represents the amount of animals counted in each sighted pod.
The hotspots were calculated using the same method as the above map, however they were weighted for the amount of animals in each pod sighted. For example only 2 pods of dolphins were sighted West of Palermo, but both pods 6 and 10 individual dolphins within them, the 2 highest of the season, resulting in a hotspot being circled around this area.