1. To investigate geographical, seasonal and inter-annual variation in abundance of long-finned pilot whales
2. To assess habitat use of this species with respect to environmental features and to biological parameters (presence of calves, behaviour, etc.), including site specificity of animals/social groups
3. To investigate the potential effect of human activities on distribution and abundance
4. To estimate reproductive and survival rates
5. To investigate the viability of the population and to propose a conservation plan
6. As data and time permit, to explore the above for other deep-water species in the area

Abstract.

In recent years, beaked whales have received much attention by the public due to mass stranding events that were associated with military activities. One of the possible mitigation measures is to identify and protect their habitat. With this objective in mind, line-transect data collected by the non-profit organisation Alnitak between 1992 and 2007 was used to reveal habitat preferences of beaked whales in the northern Alboran Sea and adjacent Gulf of Vera. Methods employed included multiple covariate distance sampling for estimating a detection function. This function models the decreasing detectability of animals with increasing distances from the transect-line. To estimate the number of beaked whales on the trackline that were missed by the observers due to the whales being submerged, time-depth records from a dtag attached to a Cuvier’s beaked whale in the Ligurian Sea were analysed (courtesy Peter Tyack, Woods Hole Oceanogr. Instn., MA, USA). Generalized additive models were used to identify species-habitat correlations and make predictions on abundance and distribution of beaked whales in the study area. Two species of beaked whales were identified during the study including Cuvier’s beaked whale Ziphius cavirostris and northern bottlenose whale Hyperoodon ampullatus. Due to the small sample size of detections both species were modelled together. It is likely that this did not increase the noise around the species-habitat correlations as it is believed that they occupy similar ecological niches and follow similar prey patterns. Difficulties in fitting models were the predominance of zeros in the response variable. Results indicated that beaked whales preferred areas at least 600m deep with little variations in depth. Highest abundances were predicted near the 1000m isobath north of Alboran Island. Variance estimates generated by jackknifing were low, possibly due to the non-independence of resampling units.

Abstract.

The Risso's dolphin (Grampus griseus) is a delphinid usually found in the waters of Murcia and Andalucia, but its status is of "Data Defficient" for the IUCN. Therefore, this study has been done as a contribution to the knowledge of the population inhabiting the Alboran Sea and the Gulf of Vera. Over the years that Alnitak has been sailing through the SoOuth-Eastern waters of Spain (1992-2007), many sightings have been done of this species, during which a few thusand pictures were taken for photo-identification. From these, 1317 were of sufficient quality for analysis (Q=2 y Q=3). The method od photo-identification was used to identify the animals and build the catalogue of animals, with 440 records. Mark-recapture methods, applied to the photo-identification data, were used to estiamte abundance with the data from 1992 to 1995. The estimated number of animals with recognisible marks was 267 from the left side and 355 from the right side. Once corrected by the proportion of marked animals int he population (thetha=0,765), combining both sides, we obtained an abundance estiamte of 621 animals (95% I.C. = 362-1065).

To compare the behaviour and habitat use of two populations of bottlensoe dolphin in the Mediterranean

Specific aims.

1. Comparison of the behaviour of the two populations and its effect on the selection of habitats
2. Comparison of the potential impact of human activities on the populations

Abstract.

The Mediterranean sub-population of striped dolphins has been proposed as “Vulnerable” during the recent IUCN Red List assessment of Mediterranean cetacean subpopulations, especially due to its susceptibility to morbillivirus epizootics.

New estimates of abundance and habitat preferences of striped dolphins (Stenella coeruleolba) were determined based on a large dataset collected over 16 years, 1992 to 2007. 61001km of effort were covered with non-systematic line transect sampling yielding 1249 sightings in the northern part of the highly productive Alborán Sea, western Mediterranean. Observed group sizes ranged from 1-800 individuals (mean=55, median=30, standard deviation=78.75). Multiple factors affecting the detection probability of striped dolphins were obtained using Multiple Covariate Distance Sampling. Spatial modelling using generalized additive models (GAMs) was applied to generate both abundance of groups and group size independently. The best model of each was combined to predict abundance for the northern Alborán Sea. The covariates depth and latitude/longitude significantly influenced the abundance of groups with explained deviance of 15.7%. The model with the most deviance explained by 10.3% on group size contained depth, latitude/longitude, variation coefficient of depth and dense scattering layer. The absolute abundance for the Northern Alborán Sea was estimated to be 25728 individuals (95%Ci= 23297.20- 29802.50). In subareas, relative abundance was highest in Western Alborán Sea and became less to the East. No trend in abundance over years could be ascertained because comparable abundance estimates were lacking. Habitat preferences were towards deeper water and bigger group sizes occurred at smaller variability of the sea floor. Group size was large where biomass was dense, suggesting an important feeding area for striped dolphins along the gyres in the Alborán Sea. The results from this thesis will contribute to the assessment of the present situation of the striped dolphin in the Western Mediterranean. Therefore it will be useful in informing conservation actions for striped dolphins in the Mediterranean.

Abstract.

Bottlenose dolphins (T. truncatus) are widely distributed in the Mediterranean Sea and are a priority species listed under Annex II of the EU Habitats Directive. Three Special Areas of Conservation (SACs) have been proposed for bottlenose dolphins in the western Mediterranean. In order to monitor the effectiveness of the SACs, baseline abundance estimates and distribution patterns are required. In 2006, Cañadas et al. published model-based estimates and density maps of bottlenose dolphin abundance using data between 1992-2003. It is important to use newly collected sightings data to assess (a) if there have been any further changes in bottlenose dolphin abundance and (b) whether or not the originally identified core areas (areas of high abundance) for bottlenose dolphins have changed.

This project used sightings data from 2004-2006 to produce model-based abundance estimates and density maps, for a study area including the northern Alborán Sea and the Gulf of Vera. 6272.5 n.miles of non-systematic line transects were surveyed and divided into 3215 segments (average length: 1.95 n.miles). The point estimate for the entire study area was 1030 animals. The study area was also divided into 4 subregions, and abundance estimates were calculated for each of these sub-regions. Animals were concentrated in the northern Alborán Sea (point estimate: 880), particularly around the Seco de los Olivos, an underwater sea mount and an area of high productivity. The high abundance estimate for the northern Alborán Sea (in comparison to previously published estimates) may be explained by the arrival of immigrant animals in 2004, previously seen in 2000. The results presented here continue to demonstrate the importance of long-term studies for identifying natural fluctuations in animal population sizes. No firmer conclusions can be made until measures of variance are added to the point estimates.

Abstract.

Little is known about pilot whales in the Mediterranean Sea, a species which was proposed as “Data deficient” in the recent IUCN Red List assessment of Mediterranean cetacean subpopulations. An extensive dataset collected over 15 years (1992-2006) in the Alborán Sea (western Mediterranean) was used to model habitat preferences and estimate absolute abundance of long-finned pilot whales in the area during the study period. Shipboard line transect sampling was conducted along nonsystematically designed line transects that provided good overall coverage of the study area, covering over 56,649km on effort and resulting in 394 sightings of pilot whales. Observed group size ranged from 1 to 350 individuals (mean = 30.34, standard deviation = 40.85, median = 16). Data on physical and environmental covariates were obtained from various sources including satellite images. Multiple Covariate Distance Sampling analysis was used to model the detection function. The abundance of groups and group size were then modelled independently using Generalised Additive Models, and the results of the best-fitting models combined to predict density across a grid covering the whole study area. The best abundance of groups and group size models explained 23.1 and 27.8% of the deviance, respectively. Depth and distance from the Seco de los Olivos sea mount were found to significantly influence the abundance of groups, while depth, longitude, year and sea floor topography were the covariates that best explained variation in pilot whale group size. The absolute abundance of pilot whales in the Strait of Gibraltar, northern Alboran Sea and Gulf of Vera was estimated to be 1890 individuals (95% CI= 1483, 1915, CV=0.07). The relative density of pilot whales was highest in the northern Alborán Sea, while predicted group sizes were largest in the Gulf of Vera, suggesting both are important feeding and breeding areas for the species. The results from this study provide the first estimates of absolute abundance and will be useful in informing conservation actions for pilot whales in the Mediterranean, under the Agreement on the Conservation of Cetaceans of the Black and Mediterranean Seas (ACCOBAMS).

Abstract.

Reports of cetacean by-catch in European pelagic trawl fisheries have indicated need of methods in order to minimize this unwanted interaction. The success with deterrent harbour porpoises from static nets using acoustic deterrent devices have been proposed as a possible solution in the pelagic trawl fishery. This study was done to develop a method to conduct playback experiments on bow riding short-beaked common dolphins. It was carried out in the NECESSITY project with the University of Southern Denmark, Danish Institute for Fisheries Research and the Spanish organisation Alnitak. A method was developed and tested onboard the RS Toftevaag in the Alboran Sea, Spain. The experiments were conducted during June, July and August 2005.

The bow riding dolphins were exposed to a number of acoustic signals (tonal, frequency sweep, noise and control) and their reactions were monitored using both acoustic and video recording. Signals were transmitted using hydrophones attached on a specially designed foam bow fender. The playback signals were of constant amplitude in the signal frequency range.

Forty-one encounters with groups of short-beaked common dolphins were observed. This was less than expected according to the encounters recorded in previous years, but bad weather resulted in only 28 operational days. Ten of the 41 encounters were suitable for conducting experiments, and 77 tests were conducted during 9 encounters.

The signals source levels (SL) were all in the range between 132-154 dB rms re 1 µPa @ 1 m [130 ms duration, 25-150 kHz frequency band]. Because of the absence of strong deterrent reactions from the animals the SL was increased several times which resulted in 16 different SL/signal combinations.

The many SL/signal combinations forced a clustering of the signals in order to analyse the data. A significant difference (p = 0.01) between the CS and the other signals supported the experimental procedure and the study by general. The significant difference (p = 0.01) in deterrent effect between signals below and above 147 dB rms re 1 µPa @ 1 meter indicates the importance of the intensity parameter. GAM modelling indicated stronger response towards higher intensities, repeated number of trials and the noise signal. However the sample size is low and more data is needed before any difference between the stereotyped signals can be stated.

So far no acoustic device has been able to prevent depredation in the medium to long-term run. This study developed a reliable method in conducting playback experiments on short-beaked common dolphins. It is a relative simple way of testing the effect of a possible deterrent signal before initiating tests in a larger scaled in situ study in a commercial pelagic trawl fishery.

The main objective of this work was the evaluation of the degree of overlap in the use of certain areas of the Alboran Sea by dolphins and fisheries, as a first approach to the investigation of the potential competition for resources between both. Three specific objectives were established:

1. Estimation of the presence and density of bottlenose dolphins that use a given area over a given time.
2. Identification of the areas with more fisheries effort.
3. Analysis of the degree of overlap between the most exploited areas by fisheries and those with highest density of bottlenose dolphins.

With this project an interactive CD was developed: "Cetáceos en el Mediterráneo", with information on the various especies of cetaceans of the Mediterranean and conservation issues such as marine protected areas, threats, etc.

The main objective of this work was to analyse the acoustic pollution in the Alboran Sea adn to investigate its possible effect on the cetaceans inhabiting the area, assessing if the habitat is losing quality for them due to the acoustic pollution. Within this framework, the specific objectives established were:

• To describe and quantify the main sources of marine ambient noise in the study area: maritime traffic
• To analyse the acoustic behaviour of the cetaceans in the area and to investigate its elationship with the acoustic pollution
• To obtain a spatial distribution of ships and cetaceans, and their sounds, in order to establish the degree of overlap between the maritime traffic and the marine mammals in the study area
• To provide proposals for the correct management of acoustic pollution