Action F7. Tracking the population of Tusiops truncatus.
Partner: Fundació Bosch i Gimpera

The goal of this study was to develop an Action Plan for the Conservation of the Bottlenose Dolphin (Tursiops truncates) in the Balearic Islands. To this end three main specific priorities were identified in the proposal. (1) to determine the number of Bottlenose dolphins present in each area, (2) to establish the degree of isolation and the demographic evolution of the different groups, and (3) to evaluate the impact of fishing and other threatening factors in the main areas.

Methods applied:
Two different methodologies were used: aerial census count and photo-identification.
Establishing number of animals.
Aerial census count.
In order to evaluate the populations of common dolphin (Action F7) and of Loggerhead turtle (Action F6), three different flight campaigns were carried out during which the whole of the continental seaboard of the Balearic Archipelago was covered. An area of 2,780.54 nautical miles was covered which yielded sightings of a total of 18 Bottlenose dolphins , although other species of cetaceans were also sighted. During the sightings which occurred in the photo-identification campaign, the duration of immersions and the breathing rhythms of the dolphin groups were recorded in order to carry out any necessary corrections of the aerial census counts.

Figure 7.1:

Photo-identification (marking/re-capture)
Photo-identification is a process in which an animal is photographed and identified in order to differentiate it from other individuals of its species by examining the photographs and detecting the presence of marks (generally natural) on its body. In the case of dolphins, the body marks used to identify and differentiate individuals are situated on the dorsal fin.
Four sighting and photo-identification campaigns were carried out in the Balearic Archipelago: during the months of June, July and September 2002, from the middle of March to the middle of July of 2003, from the middle of March to the end of June 2004 and in March 2005. In order to estimate the size of the population by means of photo-identification we used the MARK v.4.1 programme for the application of marking-recapturing, developed in 1999 by White and Burnham (Colorado State University).

Figure 7.2:
Figure 7.3:

Degree of isolation and demographic evolution.
Establishing local movements and the degree of isolation of the various sub-populations in the Balearic Islands was done by analysing the data obtained by means of photo-identification. Furthermore skin and fat samples from both live and beached dolphins were analysed in order to determine their content and profile of organochloride compounds, stable isotopes and genetic profile. The results obtained were compared to those existing on other populations of Bottlenose dolphins in both the Atlantic and Mediterranean, in order to establish the degree of isolation of the Balearic population of this animal.

The effects of fishing and other threatening factors.
Fishing poses a serious threat in terms of incidental mortality / capture, and in terms of direct attacks by fishermen who view dolphins as direct competitors that damage their nets and reduce the volume of their catch of fish. Three hundred questionnaires were filled by fishermen and ships were boarded and travelled on in 200 instances in order to evaluate the problems derived from the interaction of fishing activities and dolphins.
Further to this, an acoustic detection device was used (Porpoise Detector or POD). This is a small submersible computer attached to a hydrophone which detects the presence of dolphins and their interaction with the nets. The POD used was built by Chelonia-Marine Conservation Research, UK, and was used to evaluate the interaction in those fishing activities which the first studies revealed were the most endangering for cetaceans : the trammel nets employed for fishing red-mullet (Mullus surmuletus) and cuttlefish (Sepia officinalis). The evaluation was carried out in the Bay of Alcudia in September and October 2001 in relation to the fishing of red-mullet and in Ciudadela in the months of February and March 2002 in relation to the fishing of cuttlefish.

The level of contaminating organochloride compounds found in the tissues of Bottlenose dolphins was also determined by means of analysing the biopsies obtained from live animals as well as the tissues obtained from dead beached dolphins. The samples were analysed by gas chromatography and detection of electronic capture.
Involvement of sports clubs and environmental education.
ANADE , the Association of Nautical Sport Installation in the Balearics (Asociación de Instalaciones Náutico Deportivas de Baleares), and the General Port Authority of the Balearics (Dirección General de Puertos de las Islas Baleares) offered their collaboration in order to organize educational lectures on the environment, related to the project.
Thus, a series of lectures were planned and given at major yacht clubs and marinas round the Archipelago in order to publicize the aims of the project, informing seafarers on the various species of cetaceans that are found round the Balearic Archipelago, so as to get people involved and encourage seafarers to participate in collecting data on sightings by means of photography. These lectures were supplemented with sighting files issued to seafarers so that they could fill them in thereby facilitating the collection of data and the identification of the species that could be present in the area. The file is available in *pdf. Format to all interested parties at the project website. Thanks to this initiative the written press took notice and this helped to further publicize the project.

Determining the number of individuals
Aerial census count
From the data collected it can be inferred that the population is probably open permitting the interchange of island groups with groups of the mainland coast; and that the abundance of Bottlenose dolphins varied between 727 (CV=0,47) in spring and 1,333 (CV=0,44) in autumn.
In total 12,478 km. were covered, which yielded 142 sightings of the following species:
Fin Whale--Balaenoptera physalus-(2), Sperm Whale--Physeter macrocephalus-(1), Long-finned Pilot Whale--Globicephala melas-(1), Risso’s Dolphin--Grampus griseus-(8), Striped Dolphin--Stenella coeruleoalba-(17), and Bottlenose Dolphin--Tursiops truncates-(113). (See Figure F-7.2 and Table F-7.3, annex F7.doc).
After discarding low-quality or repetitive images, the photo-identification effort yielded a total of 5,208 slides which were catalogued. The detailed analysis of all these images was added to a catalogue which includes 252 individuals identified thanks to their natural markings. Of these individuals, 100 were re-captured (identified on different days). Intense interaction with trawlers has been detected, and a total of 95 dolphins were identified interacting with trawling ships, on at least one occasion. For the whole of the areas covered during the three photo-identification campaigns carried out, an estimation was obtained of Ntotal=700 dolphins (Var Ntotal=490).

Figure 7.4

Degree of isolation and demographic evolution
The analysis of the images taken during the photo-identification campaigns shows that the composition and size of the various groups is not stable but rather changes frequently which indicates that this population is characterised by a fission-fusion model, in exactly the same way as happens in other populations of this species round the globe. Besides this, evidence has been found indicating that individuals are highly faithful to the areas they inhabit although in some cases movement between Majorca and Minorca was detected. The analysis of organochloride compounds and stable isotopes confirmed the differences between Iberian, Atlantic and Mediterranean populations. In contrast we were not able to establish a clear difference between animals in the archipelago and those along the mainland coast in terms of stable isotopes. Only slight differences in terms of organochloride compounds were found, and we therefore deduce there is light segregation between both communities with a probable degree of interchange of individuals. It has, however, been established that the population in the Mediterranean is in fact isolated from that in the Atlantic, where two sub-populations have been identified: one along the coastline and the other pelagic, the latter being nearer in evolutionary terms to the Mediterranean population.

Figure 7.5

Effect of fishing and other threatening factors.
It has been determined that the most intense interaction takes place with trammel nets, specially during the cuttlefish and red-mullet seasons, and that dolphins seriously damage the nets thereby causing loss of income for the fishermen, and on occasion there are incidental captures when a dolphin is trapped in the nets. A high degree of interaction with trawlers was also observed, although in this case the nets are not damaged and there are no incidental captures.
The analysis of organochloride compounds indicated that the concentration of fat in the Bottlenose dolphin is very high and exceeds the limits generally considered as safe. The explanation of this can be found in the high levels of pollution in the western Mediterranean, which in the case of the Bottlenose dolphin is even worse given that these animals tend to swim near the coastline and are predators. It is a known fact that some of the contaminants alter the reproductive and growth mechanisms of marine mammals and depress their immune system. Because of this it is strongly recommended that efforts should be undertaken to reduce the emission of persistent contaminating products.

Overall results of the Action:
An Action Plan for the Conservation of the Bottlenose dolphin in the Balearic Islands has been drawn up, thus fulfilling the aim of this action. Questions posed at the beginning of this Action have been answered: (1) the size of the population has been estimated using two different methodologies (aerial sectioning and photo-identification); (2) the differences between the Iberian, the Atlantic and the Mediterranean populations have been determined on the basis of the analysis of organochloride compounds and stable isotopes, thereby establishing that there is slight segregation between animals inhabiting the Balearic Archipelago and those inhabiting coastal waters along the mainland; (3) it has been established that the composition and size of the groups changes frequently, and that this population is characterised by a fission-fusion model; (4) evidence has been found indicating that the animals are highly faithful to the areas they inhabit, although on occasion movement between Majorca and Minorca has been detected. (5) it has been shown that the most intense interaction with fishing activity is in relation to trammel nets, specially during the cuttlefish and
red-mullet seasons, and that this interaction seriously damages the nets, causes loss of income to the fishermen and on occasion there are incidental captures; (6) for this species , in Mediterranean waters, high levels of organochloride compounds and heavy metals have been found, over and above the level considered as safe; finally, (7) Educational lectures on environmental matters have been given and the project has been publicized, furthermore, sighting files have been issued at all main yacht clubs and marinas in order to involve yachts in the project.

Benefits for SCI areas and/or the species.
The study carried out has furnished us with knowledge on the state of the population of Bottlenose dolphin that we previously did not have. It has also made it possible to develop an Action Plan for the conservation of this species, which includes specific recommendations to be included in future actions.
Due to that fact that areas marked out as SCI are not very extensive they are not very useful in terms of dolphin conservation, for as it has been explained above, although these animals prefer to remain faithful to their accustomed habitat, they do in fact travel over large areas. Nevertheless, in some places, as is the case of the Archipelago of Cabrera and the Bays of Alcudia and Pollensa, the existence of SCI areas is fundamental for the conservation of the species.
The results of the present project have provided us with hitherto unknown data which will be useful as reference for future studies that should be periodically carried out in order to correctly monitor how the population of Bottlenose dolphin is evolving in the Balearic Archipelago. The Action Plan for the Conservation of this species in Balearic waters included the diverse action that should be taken into account in future initiatives.