This study summarizes nearly 20 years (1997-2015) of tracking strandings of sea turtles along the Andalusian coast. In this period 2495 specimens were recorded, most of them loggerhead turtles Caretta caretta (92.6%) and leatherback turtles Demochelys coriacea (7.1%). Two other species were almost insinificant, green turtle Chelonia mydas (0.2%) and Kemp’s ridley Lepidochelys kempi (0.1%). Significant part of the turtles were recorded in the Atlantic coast, although in this area the incidence of alive specimens was low. Spring and summer were the seasons with more specimens stranded, probably related to warmer and more productive waters. The size of the loggerhead turtles observed highlights an important presence of inmature specimens in Andalusian waters, although mature individuals were not rare. In the case of leatherback turtles, adult stage is the only detected in the specimens recorded.These results, combined with the fact that the Atlantic coast has a large continental shelf and a high primary productivity near the coast, suggesting that the gulf of Cádiz may represent a neritic habitat used by the sea turtles. In this case, new and more effective politics of conservation are needed in order to protect sea turtles in this area.

The fin whale (Balaenoptera physalus) is a cosmopolitan species with a resident population in the Mediterranean Sea. Due to its habitat, open seas often far from ports and airfields, and its long-distance migratory behaviour, studying and monitoring its distribution is costly. Currently, many opportunistic sightings (OS) reports are available, which provide a source of potentially useful, low-cost information about the spatio-temporal distribution of this species. Since 1993, the Spanish Institute of Oceanography has compiled a dataset comprising 874 records of OS of nine species of cetaceans in the western Mediterranean Sea and adjacent waters. The aim of this study was to use this dataset to investigate the differential use of these waters by the fin whale when compared with other cetaceans. We compared the presence of fin whales with the presence of any other cetacean species in the dataset. Binary logistic regression was then used to model these occurrences according to several spatio-temporal variables expected to reflect their habitat use. Several significant models reveal that fin whales are more prone than other cetaceans to use the waters over the slope of the Gulf of Lion in summer. This finding confirms that the Gulf of Lion is an area of importance for this species and suggests that the slope of the continental shelf could be particularly important. Our study shows how OS can be a source of useful information when appropriately analyzed.

Deep-habitat cetaceans are generally difficult to study, leading to a limited knowledge of their population. This paper assesses the differential distribution patterns of three deep-habitat cetaceans (Sperm whale—Physeter macrocephalus, Risso’s dolphin—Grampus griseus & Cuvier’s beaked whale—Ziphius cavirostris). We used data of 842 opportunistic sightings of cetaceans in the western Mediterranean sea. We inferred environmental and spatio-temporal factors that affect their distribution. Binary logistic regression models were generated to compare the presence of deep-habitat cetaceans with the presence of other cetacean species in the dataset. Then, the favourability function was applied, allowing for comparison between all the models. Sperm whale and Risso’s dolphin presence was differentially favoured by the distance to towns in the eastern part of the western Mediterranean sea. The differential distribution of sperm whale was also influenced by the stability of SST, and that of the Risso’s dolphin by lower mean salinity and higher mean Chlorophyll A concentration. When modelling the three deep-habitat cetaceans (including Cuvier’s beaked whale), the variable distance to towns had a negative influence on the presence of any of them more than it did to other cetaceans, being more favourable far from towns, so this issue should be further investigated.

No abstract

A classic issue in ecology is to understand how similar species coexist in a given area (i.e., sympatry). The situation of dolphins in the Western Mediterranean Sea may represent a special case of sympatry in that three similar species (the short-beaked common dolphin [Delphinus delphis], the striped dolphin [Stenella coeruleoalba], and the bottlenose dolphin [Tursiops truncatus) are under strong human impacts in the same area. From the viewpoint of ecology and conservation biology, it is challenging to determine how these three dolphin species live together and avoid competitive exclusion in the setting of such impacts. The Spanish Institute of Oceanography has a dataset of dolphin species opportunistic sightings. Using these data, we constructed three binary variables, comprising the sighting of one species versus the sighting of either of the other two species. We obtained three significant probability models after performing logistic regression of these binary variables on a set of spatio-temporal explanatory variables. We analysed these models from the perspective of fuzzy set theory by applying the favourability function to the probability models, fuzzy operations overlap, and entropy. The results show that common dolphins are differentially favoured in the eastern part of the study area and far away from main shipping routes. The striped dolphin was differentially favoured in the western part of the study area, above deep waters, near main shipping routes, and in summer and spring. Finally, bottlenose dolphins were differentially favoured in the mid-western part of the study area, in winter, and over shallow waters.