Roman Dolphins

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All the available information on marine mammals inhabiting the Fiumicino - Torvajanica area and in particular the Tor Paterno shoals, are considerably fragmented and limited to some occasional sightings of bottlenose dolphin, Tursiops truncatus (Report on the Status of the Environment of the Marine Protected Area “Secche di Tor Paterno”, Roma Natura, 2004).

 This cetacean species, frequently surveyed in particularly interesting geomorphological areas, typically leads its life cycle mainly in the coastal shoreline. This type of environment is the most subjected to anthropogenic alteration and degradation.

Currently, the bottlenose dolphin is one of the most commonly sighted cetacean species. However, it is listed as not sufficiently known in the Red Data Book of IUCN.

The species is protected by the Bern, Barcelona and Washington Conventions, by the EU Habitat Directive and by the 157/’92 Italian law, resulting the only species, among those under the protection of the MPA “Secche di Tor Paterno”, profiting of a very high degree of consideration in terms of conservation measures.

Thanks to the support of OceanCare (2011 – 2012) and of Unicredit Carta Etica (2014 – 2015), Oceanomare Delphis has carried out the project “Roman Dolphins” with the objective of ensuring a greater knowledge on the presence and ecology of the bottlenose dolphin in the waters of Roman coastline (and on its interactions with human activities) and of obtaining useful information for the conservation of the species in the area.

 The Area of Study

The study area includes the waters off Fiumicino, Ostia and Torvajanica and includes the Marine Protected Area “Secche di Tor Paterno “. It covers a total area of about 300 km2 and it extends to the 100-m isobath.

The Marine Protected Area “Secche di Tor Paterno”, for its ecological peculiarities, was established with a decree on November 29th, 2000 and it covers a total area of 1.387 ha within the study area.

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Scopes and Objectives

The study and monitoring programme started in 2008 and was designed to gather useful information to:

  • identify the presence of the bottlenose dolphin in the area
  • study the distribution, the abundance, the use of the habitat and behavior of the    species
  • analyse population structure and dynamics and evaluate potential cases of individual dispersion
  • identify the impact of local maritime traffic on the presence, distribution, feeding and social behaviors of the species
  • determine the links between the species’ feeding behaviour and fishing activities in the area
  • evaluate the by-catch phenomenon, where applicable

 

Results

Observations conducted by ODO researchers have determined that the bottlenose dolphin is regularly present in the area all months of the year and interacts with trawling activities.

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By photo-id data in 2001-2012-2015, 76 adults inhabit the area, of which 3 are female (identified thanks to photos of the genital area, the presence of a newborn calf swimming tightly by their side, and by the support and transport behaviour of a dead calf - video: ODO piccolo tursiope morto 17 07 2015 1) and 5 are probable female (as individuals sighted closely to younger ones).

The preliminary comparison between the two photo-id catalogues of ODO’s main projects – “Roman Dolphins” and “Ischia Dolphin Project” – has produced an extremely interesting result: two bottlenose dolphins travel in length and inhabit both the waters of the roman coastline and those off Ischia Island. “Gaio” and “Claudio” were in fact sighted together on 8 July 2015 in Ostia, 6 September in Sperlonga, 18 September in Ischia and 30 September back in Ostia, around the shoals of Tor Paterno, travelling about 189 nautical miles.

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This dispersion phenomenon observed in some of the studied individuals, though preliminary and limited to two animals, opens space for hypothesis, including the fact that these dolphins could be part of a meta-population (population of populations) which is a mosaic of temporary populations, linked by the dispersion of individuals that move from one to the other.

Fishing Activities in the Area

About 263 small motorboats are operating in the Roman compartment and are involved in small-scale artisanal fishery, typically using set and fix gear.

The fishing activities in the area are mostly performed using some types of gillnets which are traditionally deployed in coastal areas (trammel nets, set surface longlines, bottom longlines, monofilament fishing nets, bivalve dredges). 

Trawlers are instead much bigger (about 20-25m long, about 45 operating boats) and operate with a trawling net generally of conic shape; its terminal part, which can be opened to release the caught fish, is called sack, the opening part is called mouth, and the central is called belly.

Often, at each sides of the mouth there is a triangular net that functions as invitation and is called wing. The net is kept opened by structures that go by the name of divergent. 

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The mouth and the wings that trawl the seabed are armed with lead weights and chains to dismantle the surface of the bottom in order to push out in the water fish and other animals hidden underneath. The higher part of the net instead has got floatation devices to keep “the mouth open”.

Trawlers have a “plow” effect on the bottom causing the impoverishment of the fish resources and the corruption of the natural environment. This fishing method is now forbidden by the institutional decree of the MPA (DM 29/11/2000) within the shoals of Tor Paterno.

Interactions between bottlenose dolphins and fishing activities

It is well known that in different parts of the world bottlenose dolphins show different feeding strategies depending on the specific environment.

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Amongst the most peculiar ones, there is the active following of the prey in shallow waters and their subsequent stranding on the shore in order to catch it, as well as the creation of mud nets with their flukes striking the seabed, and also, the collaboration with humans during artisanal fishing (dolphins help fishermen pushing fish in the nets and receiving back some of that as a prize). Another strategy is the active feeding on gillnets and trawlers.

This last technique – known as “opportunistic’ – is however very dangerous for dolphins. Often in fact dolphins are found dying or already dead entangled in the nets (phenomenon known as by-catch, which is the accidental catch of non-targeted animals like dolphins), or have deep scars or mutilations on their body. Moreover, this behaviour of interaction with fishing equipment has caused in time a negative attitude of fishermen towards dolphins, which are considered competitors for fish, as well as cause of damage to nets.

Currently, data on a potential direct competition between dolphins and fishing activities in the study area of “Roman Dolphin” project isn’t available, even though often events of conflict have been reported.