The harbour porpoise (Phocoena phocoena) is one of the common small cetaceans of European waters. This discreet and undemonstrative species is strongly represented throughout the cold waters of the northern hemisphere, and is the most abundant cetacean in the North Sea. In the last few years, some observations and studies indicate a shift of harbour porpoise distribution in European waters, from northern regions of the North Sea to the southern North Sea, English Channel and Celtic Sea. This shift may include a comeback around the coasts of France. Harbour porpoises inhabit shelf-waters and are often observed in shallow waters, conditions offered for instance by the coasts of Brittany in north-western France. We used opportunistic sightings, aerial survey and a ten-year strandings database to study the presence of harbour porpoises along the coasts of Brittany. Opportunistic sightings made by non-specialists did not confirm a strong presence of harbour porpoises along the Brittany coasts, most probably because of the undemonstrative behaviour of this cetacean. However, aerial survey and stranding analysis indicate that harbour porpoises have become natural inhabitants of the Brittany coasts once more: 68.6% of cetacean school sightings made during a 1578 km aerial survey of the Brittany coasts concerned harbour porpoises, with an encounter rate of 1.5 individuals per 100 km that peaked to 5.8 per 100 km to the top of the shallow waters of the south-western Western English Channel. The number of harbour porpoise strandings increased each year from 1997 to 2007, making a total of 135 along the coasts of Brittany. Other cetaceans did not show such an increase during the same period. Strandings of harbour porpoises were also characterized by an apparent increase as a proportion in relation to all the cetacean strandings during the months of September to January, by a marked impact of by-catch during winter, and by an almost total absence of stranded calves. The comeback of the harbour porpoise along Brittany coasts is clearly confirmed by our data, and a stable population seems to be established again along the coasts of Brittany. This tends to confirm the shift of the distribution of the species in certain European waters. Long term monitoring, diet and genetic studies are now planned for a better understanding of this shift, and for the effective implementation of a conservation plan.

A three year study was undertaken during 2002 to 2004 from May to September to estimate abundance and density of harbour porpoises on the north coast of Anglesey, Wales, UK. There were no ecological data regarding the harbour porpoises in Anglesey waters so the ability to influence conservation measures was highly constrained.

Boat based transects using distance sampling techniques were applied so a robust estimate of density and abundance could be attained. The study area consisted of a block approximately 489 km2 extending from the east of Point Lynas to the west of South Stack on north coast of Anglesey. The study area was divided into 5 blocks consisting of 31 perpendicular transect lines to the shore. Each of the transect lines were surveyed 1–5 times by the end of the three year study.

Based on the assumption that g(0) = 1 the density of harbour porpoises for the 489 km2 study site was estimated to be 0.630 individuals/km2 (CV = 0.20) and the abundance is estimated to be 309 individuals (CV = 0.20). Heterogeneity in density and abundance was observed across the 5 blocks which showed Point Lynas and South Stack to have the highest densities. This distribution was closely associated to fine-scale oceanographic features which cause prey to be concentrated and may facilitate foraging for harbour porpoises. The study showed that Anglesey provides coastal habitats for the harbour porpoise and was the first study of this kind in North Wales, UK.

Regular monitoring of the status of cetacean populations is essential for conservation, policy and management. By using a passenger ferry as a scientific research platform, this study provides information on seasonal, annual and longer-term changes in the occurrence of three cetacean species along a relatively fixed transect through the English Channel and the Bay of Biscay. Data were collected over an 11 year period through the Biscay Dolphin Research Programme (BDRP). Surveys were conducted every month from 1996–2006 between Portsmouth, England and Bilbao, Spain by a team of experienced observers using standard techniques. From a 0.125° by 0.125° grid, cells were surveyed in each year and where each species was recorded they were identified using a geographical information system (GIS). A rapid analytical method—species occupancy (defined as the proportion of surveyed cells that a species was detected in)—was used to assess whether there were any trends in occurrence over time for three cetacean species. From this analysis, a significant trend to increasing occurrence of harbour porpoises in summer months in the English Channel was identified. There were also increases in the occurrence of common dolphins in the English Channel in winter months and striped dolphins in the Bay of Biscay in winter months corresponding with a decrease in summer occurrence, across the study period. However, while consistent, these trends were not significant.

The sperm whale, Physeter macrocephalus, was the most captured great whale in the Azores Archipelago by land-based whaling and nowadays is the most appealing species for whale watching, one of the archipelago's principal sources of tourism. Our objective was to compare number of sightings during whaling and whale watching activities. Our main question to address the possible impact of past whaling in recent whale watching is: does a present-day eco-tourist sight more or fewer sperm whales than a whaler could sight in the past? For that, a compilation of data resulting both from past whaling records and recent whale watching records was conducted. We obtained a total of 727 independent sightings of sperm whales during a total of 280 different days of sperm whaling between 1947 and 1973. A total of 1767 sperm whale sightings were made during 1133 days of whale watching activities, between 1997 and 2008. The sperm whale sighting per unit of effort average was significantly higher in the past (35.68) than in the present (12.06). In the Azores, captures over the decades greatly decreased the number of sperm whales in the region and twenty years after the end of sperm whaling a reduced number of recent sightings were found.

São Tomé and Príncipe is an archipelago located in the Gulf of Guinea. This archipelago seems to be an important area for cetaceans, probably due to large concentrations of prey, as well as the existence of several small bays and shallow water that constitute preferred rest areas. In comparison to other areas of the world, little is known about cetacean communities in this archipelago. Boat-based surveys to record sightings of cetaceans were conducted between 2002 and 2005, which represents the first approach to study the occurrence of whales and dolphins in this tropical region. Sightings of humpback whales (Megaptera novaeangliae), bottlenose dolphins (Tursiops truncatus), pantropical spotted dolphins (Stenella attenuata), killer whales (Orcinus orca), sperm whales (Physeter macrocephalus) and pilot whales (Globicephala melas) were recorded. Cetaceans were found throughout a range of sea surface temperature between 24 and 29°C and a wide range of depths. Significant differences were found regarding the occurrence of some species. Humpback whales showed a preference for shallower waters between 20 and 100 m. Bottlenose dolphins occurred most commonly along the continental shelf (20 to 100 m) and pantropical spotted dolphins occurred in deep slope waters (>1000 m).

Reliable methods to identify and monitor cetacean individuals are important to assess population behaviour and ecology. We describe and evaluate the application of the digital video-identification technique (DVI) for the acquisition and analysis of dorsal fin images in the study of bottlenose dolphins (Tursiops truncatus) in the Cagarras Archipelago, Rio de Janeiro, Brazil. Between August and November 2004, we identified and catalogued 20 individuals; 80% were re-sighted more than twice. The Individual Residence Index varied between 1.0 (N = 1) and 0.2 (N = 4). Compared with traditional photo-identification methods, DVI offers significant advantages in respect to production of sequential images and speed of editing and processing.

This study reviews and updates information on cetacean strandings in the state of Ceará, Brazil (02°30′S 41°15′W– 04°30′S 36°45′W), comprising 573 km of coastline. In the years 1992–2005, there were 252 cetacean stranding events, representing 19 species: three species of Balaenopteridae, three Physeteridae, two Kogiidae, two Ziphiidae and 11 Delphinidae. Three species comprised the majority (78.9%) of stranding events: estuarine dolphin, Sotalia guianensis (61.9%); sperm whale, Physeter macrocephalus (10.3%); and rough-toothed dolphin, Steno bredanensis (6.7%). There was an increasing trend in the number of cases reported in the first five years with a highest frequency achieved in 1996. Stranding events occurred throughout the year, with the lowest frequency occurring in the autumn (March–May). Approximately 4% of the events were attributed to natural causes while 24.6% were human-related, mainly incidental captures. Meat removal for human consumption or bait was recorded in 6.7% of events. In the study area, Sotalia guianensis, P. macrocephalus and Steno bredanensis were the most abundant cetacean species, whereas Lagenodelphis hosei, Pseudorca crassidens, Orcinus orca, Kogia sima, Mesoplodon europaeus, Balaenoptera acutorostrata and Balaenoptera bonaerensis are probably rare in the area.