22 October 2011

Lone common dolphin travels

While common dolphins are often regarded as highly mobile animals, their movements and ranging patterns are poorly known. No long-distance movements have been documented through photo-identification of individually identifiable animals.

A recent paper by Tilen Genov and colleagues reports the long-distance movement of a naturally marked individual, encompassing 1000+ km across the Ionian and the Adriatic Seas. It also describes the subsequent behaviour and site fidelity of the same individual, in association with a calf, in and around the commercial port of Monfalcone, northern Adriatic Sea.

The article can be downloaded HERE.

15 June 2011

Common dolphins are becoming rare in the Mediterranean

The time has come to turn good intentions into actual conservation action

Once one of the most abundant cetacean species in the Mediterranean Sea, the short-beaked common dolphin (Delphinus delphis) has declined throughout the region since the 1960s. The primary causes of this decline include prey depletion caused by overfishing and incidental mortality in fishing gear. Today, common dolphins survive only in small portions of their former Mediterranean range, while in most areas they have become rare or are completely absent.

18 May 2011

Bottlenose dolphin depredation in Sardinia

Perhaps as a consequence of prey scarcity caused by overfishing, in some Mediterranean Sea areas coastal communities of bottlenose dolphins have specialised in the depredation of fishing nets. While the problem is relatively widespread, it is particularly acute within a Marine Protected Area in western Sardinia, Italy, where angry fishermen blame dolphins for damaging gear and reducing landings.

08 May 2011

Monk seals in the Northern Gulf of Evia

On March 18th, 2011 we were following a group of 20 bottlenose dolphins moving away from a polluted bay in the Northern Gulf of Evia, Greece. The dolphins had been feeding around the cages of fish farms located in the bay, in waters contaminated by the discards of a large smelting plant.

The sun had set and light was dim. However, we wanted to take a few more photos of the dolphin's dorsal fins, to allow for individual identification based on natural markings. Much to our surprise, a monk seal head suddenly appeared amidst the dolphin backs.

The animal came close to our inflatable and stopped at about 3 m, staring at us with inquisitive large eyes. This odd situation lasted for what felt like a relatively long time — possibly 10 seconds — giving to Silvia an opportunity of taking close-up photos of her head and range of expressions. The seal seemed unconcerned by the dolphins surfacing all around, but she was very interested in our boat and especially in Silvia, who was carefully inspected.

Then the animal swam away, and it was then that we spotted another monk seal: a juvenile. This one was apparently looking for the adult animal — possibly her mother — elevating her head above the dark-blue waters. A few surfacings and both seals had gone.

The dolphins did not seem to bother and they kept swimming away. We returned to them to take a few more photos before it was completely dark.

Back at the field station, while looking at the beautiful monk seal portraits, we recalled a recent report of an animal being shot in that same area, as well as similar stories told by local fishermen and fish farm workers.

Because Mediterranean monk seals Monachus monachus occasionally depredate fishing gear they get killed by angry fishermen who regard them as vermin. Few shelters exist where a monk seal mother can hide undisturbed and raise her offspring. Their prey is being increasingly depleted by overfishing. Their habitat and food polluted by manmade toxic contaminants. Yet, these two animals had managed to survive under adverse circumstances: an assertion of the species' resilience to eradication.

We were lucky to experience such a close encounter with two of these rare and elusive marine mammals, classified as 'Critically Endangered' in the IUCN Red List. Two monk seals approached our boat and got a few shots — but happily this time it wasn't bullets.

(Photo by S. Bonizzoni)

Studying bottlenose dolphins in a semi-closed basin exposed to acute anthropogenic impacts

When we started our work in the Northern Evoikos Gulf, central Greece, all we knew came from a 2003 scientific article written by the late Dimitris Zafiropoulos — a pioneer of dolphin research in Greece — together with his wife Livia Merlini (1). Dimitris and Livia reported an extremely high density of bottlenose dolphins in these waters.

As of 2010, we had been studying dolphins in the several areas of Greece, as well as in Italy and Croatia. The Northern Evoikos Gulf was a portion of Greece that had long stimulated our interest. We wanted to describe the present conservation status of dolphins in an area of high human impact and compare it with situations found in other places. Such approach can ultimately increase our understanding of cetacean ecology as well as of their responses to human pressures.