Depredation by cetaceans and sharks on longline fisheries is a global issue that can have negative impacts on both animals and fisheries and has concerned researchers, managers and the fishing industry. Nevertheless, detailed information on depredation is only available for a few regions where the problem exists. With the purpose of evaluating killer whale depredation on longline-caught tuna (Thunnus spp.) and swordfish (Xiphias gladius) in the waters off southern and south-eastern Brazil and comparing it to shark depredation, data sheets were distributed to the captains of tuna vessels in Santos, south-eastern Brazil, between 1993 and 1995. Data on the catch per unit effort (CPUE) of tuna and swordfish and some records of interactions were also obtained from fishing vessel logbooks. Dockside interviews with fishermen and with researchers on board tuna vessels provided additional information. Killer whale and shark interactions were analysed per longline set and per trip. Killer whale interactions occurred from June to February, mainly between June and October, while shark interactions occurred year round. The number of sets and trips involving shark interactions was significantly higher than the number of sets and trips involving killer whale interactions. However, when depredation occurred, the proportion of fish damaged by killer whales was significantly higher than by sharks. Furthermore, killer whales removed or damaged significantly more hooked swordfish than hooked tuna, whereas sharks damaged significantly more hooked tuna than swordfish. This study also shows that cetacean by-catch is experienced by the tuna and swordfish longline fishery in Brazilian waters.

Local dive shop operators and fishermen report that rough-toothed dolphins (Steno bredanensis) are frequently encountered off the coast of Utila, Honduras, (16°05'46.5"N 86°55'47.8"W). Our observations suggest that at least some of these animals may constitute a resident population, although the extent of the resident group's home range has not been determined. Twenty-eight rough-toothed dolphins were identified using photo-identification techniques, 15 of which were re-sighted on two or more occasions. The 12 animals that were re-sighted four or more times were typically seen together, suggesting that they constitute a stable social group. At least one of these dolphins is an adult male, and his continued presence in this social group may reflect a social structure for rough-toothed dolphins that differs from that described for other dolphin species. Social interactions often involved tactile behaviours such as pectoral fin rubbing and side rubbing. The observed dolphins sometimes expressed interest in the research vessel and other boats by approaching, and on separate occasions examined a hydrophone and slow moving propeller visually and echoically. Overall, our behavioural observations suggest: (1) synchronous behaviours and ‘tight’ groupings are common while rough-toothed dolphins are travelling; (2) tactile contact is an important aspect of social interactions for rough-toothed dolphins; (3) cooperative behaviour occurs during play; and (4) rough-toothed dolphins are curious.

We collected data on the distribution of fin whales (Balaenoptera physalus) and minke whales (Balaenoptera acutorostrata) in the Bay of Fundy, Canada from a whale-watching vessel during commercial tours between July and September 2002. A single observer recorded the positions, species, numbers and surface activity of whales encountered during boat tours. We controlled for biased search effort by calculating sightings rates for both species in cells measuring 2′ latitude by 2′ longitude throughout the study area. Sightings rates were calculated by dividing the number of sightings of fin and minke whales in each cell by the number of visits by the tour boat to that cell. We used generalized additive models and generalized linear models to examine the influence of benthic topography on whale distribution patterns. Models showed a non-linear relationship for minke whale sighting rates with increasing benthic slopes and a linear relationship for minke and fin whale sightings rates with increasing water depth. Sightings of minkes were concentrated in areas subject to tidal wakes near the northern tips of Grand Manan and Campobello Island. Fin whales were also found off the northern tip of Grand Manan but sighting rates for this species were highest in areas with less benthic sloping topography adjacent to the relatively deep Owen Basin. Foraging was recorded during 87% of all whale encounters and our results indicate that whale distribution in this area is likely to be influenced by depth, bottom topography and fine scale oceanographic features that facilitate foraging.

This study used classification and regression trees (CART) to investigate and compare the habitat preferences of marine mammals in this area. Data were collected in early summer (June/July) in 2004 and 2005 and the distribution of marine mammal species was compared to 10 ecogeographic variables (EGVs). Of 13 species of marine mammals sighted during the study, there were sufficient sightings to examine the habitat preferences of seven. For all species a measure of ‘shelf tendency’ (distance to coast or water depth) was an important variable and the species could be separated into two groups, the deep-water species and the shelf species, with little overlap between them. The occurrence of both deep-water species (long-finned pilot whales and Atlantic white-sided dolphins) was also related to dynamic variables such as sea surface temperature (SST) or primary productivity. Two of the shelf species (northern minke whales and grey seals) were only linked to topographic variables and were limited to quite specific habitats. A third species (harbour porpoise) was primarily related to topographic variables, but in the shallowest waters was also related to local variation in SST. The occurrence of the final two species (common and white-beaked dolphins) was linked to SST and local primary productivity. However, while both species preferentially occurred in areas with higher productivity, the two species differed in their preference for SST, with common dolphins preferentially occurring in warmer waters and white-beaked dolphins in colder waters.

The harbour porpoise is the only resident cetacean species in the German Baltic Sea. Within the last several decades this harbour porpoise stock declined drastically, causing deep concern about its status. Plans of the German government for proposing Marine Protected Areas (MPAs) to implement Natura 2000 and for assessing the impact of offshore windmill constructions on the marine environment led to an increased research effort on the harbour porpoise in German waters. For the first time, long-term passive acoustic monitoring has been conducted in the German Baltic Sea from the Kiel Bight to the Pomeranian Bay from August 2002 to December 2005. Porpoise detectors (T-PODs) have been installed five to seven metres below the water surface at up to 42 measuring positions throughout the investigated area, registering the exact times of echolocation signals of passing harbour porpoises. The proportion of monitored days with porpoise detection in each quarter of the years has been analysed. A correlation of the results with the longitude of the measuring position revealed a significant decrease from west to east in the percentage of days with porpoise detections. Comparison of data gathered in the first quarters with the third quarters of the monitoring years displayed a seasonal variation with fewer days of porpoise detections in winter time than in summer time. Nevertheless, harbour porpoises have been detected year-round at most of the measuring positions in the German Baltic Sea. The present study clearly indicates a regular use of the German Baltic Sea by harbour porpoises with a geographical and seasonal variation in the usage of the German Baltic Sea. The larger numbers of harbour porpoise detections in spring to autumn compared with winter suggests that the German Baltic Sea is an important breeding and mating area for these animals.

Cuvier's beaked whale is a poorly-known species. It has been considered common since 1980 in the Pelagos Sanctuary (north-western Mediterranean Sea), but it has hardly been studied, chiefly due to difficulties in sighting. Stranding data indicates that the beaked whale is present all along the Ligurian coast. As with any deep-diving odontocete, Cuvier's beaked whale feeds mostly on deep-sea squid, but also on some fish and a small number of crustaceans. As a consequence, it is thought to be found mainly in waters deeper than 1000 m, where the sea bed has a particular slope. The aim of this work is to analyse a large quantity of sightings in order to define the favoured habitat of the beaked whale. Topographic features such as depth, depth gradient and bathymetric anomaly were analysed due to their direct influence on the prey of Cuvier's beaked whales. Data were registered between Genova and Imperia, from 2000 to 2006. Two hundred and forty-seven sightings were recorded, a total of 532 whales. The mean herd size observed was 2.3±1.5 (range=1–11). For 40 sightings, the group composition was divided into maturity categories, using results obtained by photo-identification. Seventeen groups consisted of purely immature animals, and 4 groups consisted of only mature animals. The 19 mixed herds were composed mainly of 4.0±2.2 individuals (range=2–8) and consisted of 58% mature individuals. The 17 immature groups consisted of 2.1±0.9 individuals. Mature animals were usually found alone. Forty-eight per cent of beaked whales were seen where the depth was between 756 and 1389 m but the encounter rate was higher between depths of 1389 and 2021 m. The sightings were more frequent (34%) where the sea floor slope was between 31 and 51 m/km but the encounter rate was higher where the sea floor slope was between 11 and 31 m/km. The encounter rate for Cuvier's beaked whales was higher where the depth anomaly was positive with values between 342 and 586 m.

The relative distribution of sperm whales (Physeter macrocephalus) and sea surface temperature (SST) fronts have been studied in summer in the north-western Mediterranean Sea. We used passive acoustic data (778 samples) obtained offshore during dedicated surveys between 1999 and 2004 and Pathfinder/Modis remote sensing data to compute front maps and to calculate mean distances from sperm whale detections (N=132) to SST-fronts. Mean distances from sperm whale acoustic detections to SST-fronts were significantly lower (10.4 km) than from other acoustic samples to those fronts (17.0 km). The same result was obtained when calculating distances from sperm whales to the North Balearic Front surface signature. If sperm whales are commonly observed along the continental slope, we showed that offshore individuals were located close to SST-fronts. This bimodal distribution in the north-western Mediterranean is linked to sperm whale feeding strategy, demonstrating ecological opportunistic behaviour in this high level predator.

Sperm whale residency and movements within the Mediterranean Sea were investigated using photo-identification data collected in summer over a 15 year period (1991–2005). Surveys were conducted from a 12 m motor sailing boat. Although dedicated to cetaceans, surveys did not solely focus on sperm whale photo-identification, so time to track and photograph all individuals forming a group was not always available. From good quality photographs, 44 individuals were identified in the western Mediterranean, including the Ligurian Sea, the Gulf of Lions and waters off the Balearics. Eleven identified whales were photographically re-captures. Within-year re-sightings occurred from 1 to 29 d apart, while five identified whales were re-sighted over several summer seasons, from 1 to 7 y apart. Four whales were seen in more than one year in the northern part of the basin, indicating site fidelity to this feeding area. The combination of photo-identification and acoustic data (size estimation from inter-pulse interval measurements) enabled us to demonstrate a north–south movement of some sexually mature males (around 13 m in length), feeding in the northern regions and joining groups of females off the Balearics for around 20 d. These displacements ranged over ~500 km, with travelling time of seven days or less.

Data on habitat use by marine tucuxis (Sotalia guianensis) were collected in Guanabara Bay (GB), south-eastern Brazil, over a two-year period. Diurnal activities of marine tucuxis were dominated by behaviour related to feeding/foraging (58% of all recorded time). Dolphins spent more time in feeding/foraging activities in the morning with a secondary peak in late afternoon. Dolphins were seen in waters of 2 to 35 m (11.63±6.05; median=12.0). Depths used by S. guianensis groups significantly differed from depths available in GB (Kolmogorov–Smirnov test; Z=5.72; P<0.001). Most groups (69.8%) were sighted in depths between 5.1 and 15.0 m. Dolphins occupied an area of 136.9 km2, which represents about 42% of the entire water surface of GB. Individuals selected areas within GB and avoided the most degraded ones, which suggests that habitat degradation may affect S. guianensis distribution. Diurnal distances travelled by individuals ranged from 3.3 to 27.2 km in a same day. Dolphins found in main channel and adjacent waters moved along the north–south axis of GB throughout the day and covered distances three times greater than dolphins which concentrated their activities in north-eastern areas.

Between April 2002 and April 2005, 210 estuarine dolphin groups were sighted, with 58 animals individually identified. Fifteen dolphins were photo-identified just once, while only two animals were sighted in 15 different months. Some individuals showed long-term residence (more than 3 y). Residence rates showed heterogeneity in the dolphin's permanence of the estuary, with 60% of the individuals with low numbers (<10) and only 7% showing high values for residence (maximum=45.9). Continued resightings of some dolphins support the regular use of the study area by the animals, despite some individuals that, after a long time without resightings were registered again. Individual range analysis showed that dolphins shared the same common area, the Caravelas River Estuary. A marked fluctuation in the number of photo-identified dolphins was observed in the study area, revealed by the high number of individuals with just a few resightings. The majority of the dolphins (60%) present a yearly residence pattern, as observed in other areas, suggesting that a few individuals show high fidelity for the area, while many other dolphins move constantly between different areas for unknown reasons.

We use a bootstrap simulation framework to evaluate the relative importance of different sources of random and systematic error when estimating diet or food consumption of cetaceans, using a data set on harbour porpoise diet in Scottish (UK) waters from 1992–2003 (N=180) as a model. We also evaluate the consequences of applying explicit weightings to individual samples and/or sub-sets (‘strata’) of samples. In terms of the precision of estimates of diet composition, sampling error was the most important source of error, to the extent that overall 95% confidence limits changed only very slightly when sub-sampling error and regression errors were taken into account. On the other hand, for estimates of total food consumption by the porpoise population in Scottish waters, uncertainties about population size and energetic requirements were more important than uncertainty about diet composition. In relation to the accuracy of estimates of diet composition, the study also highlighted the importance of selecting regressions appropriate to prey in the study area (as opposed to ones constructed for the same prey species in another area) and demonstrated that applying equal weighting to individual samples or sample strata can substantially alter the resulting picture of diet. Therefore, the rationale for applying such weightings needs to be carefully considered.

Fatty acid profiles were used to investigate aspects of bottlenose dolphin populations around the Azores archipelago. Biopsy samples were obtained from 70 dolphins during the period 2002–2004. No statistically significant differences in profiles were found between different island groups, between sexes or between year of sampling. Thus no evidence was seen for island group fidelity, in contrast to bottlenose dolphins found around similar island groups such as the Hawaiian archipelago or the Bahamas. The findings are consistent with concurrent genetic and photo-identification studies on dolphins in the Azores.

We describe the diet of bottlenose dolphins Tursiops truncatus in Galician waters, north-western Spain, based on 82 non-empty stomachs recovered and analysed from stranded animals between 1990 and 2005, quantifying interannual and seasonal variation in the diet, as well as dietary variation related to sex and size. The most important prey species (in terms of numerical importance and biomass) were blue whiting (Micromesistius poutassou) and hake (Merluccius merluccius), both of high commercial importance in Galician waters. Most blue whiting eaten by dolphins were mature fish but the estimated total consumption was relatively low (around 10%) compared to Spanish fishery landings of this species. In contrast, most hake eaten by dolphins were probably immature but the estimated total consumption is more than 20% of current annual fishery landings. The diet of by-caught animals, which made up around one third of the sample, was very similar to that in the overall sample. Although bottlenose dolphins are often seen close inshore, evidence from the diet suggests that they feed at the shelf edge. Evidence was found of ontogenetic dietary shifts and differences between diets of male and female dolphins. There were also clear changes in average diet over the 16-year study period, although there was no evidence that they were in response to changes in fish abundance. The amount of hake in the diet remained stable against a background of falling local abundance while the amount of blue whiting declined despite an increase in spawning stock size.

Stomach contents were analysed from three species of beaked whales which mass-stranded shortly after a naval exercise conducted in the Canary Islands in September 2002. Animals from such mass strandings often contain freshly ingested food in their stomachs and can provide a more reliable guide to feeding habits than other strandings. Food remains recovered from seven Cuvier's beaked whales (Ziphius cavirostris) consisted mainly of oceanic cephalopods, the most numerous being Taonius pavo, Histioteuthis sp., Mastigoteuthis schmidti and Octopoteuthis sicula. Many of the cephalopod species found in the diet appear to undertake daily vertical migrations, being found in shallower waters during the night and moving to deeper waters during the day. Single specimens of Blainville's beaked whale (Mesoplodon densirostris) and Gervais' beaked whale (Mesoplodon europaeus) had eaten both fish and cephalopod prey. The most numerous prey remains belonged to gadid fish and viperfish (Chauliodus sp.) respectively. These results are consistent with the limited published data on diet in these species, with Mesoplodon species having a relatively higher proportion of fish in the diet whereas Ziphius specialises on cephalopods.

Along the central coast of Rio de Janeiro State (22°25′S–23°00′S), south-eastern Brazil, the marine tucuxi dolphin (Sotalia guianensis) feeds on neritic prey that are distributed through the water column and are abundant all year round. The most frequently found species were the teleost fish Trichiurus lepturus, Cynoscion guatucupa, Isopisthus parvipinnis and Porichthys porossisimus. Fish species were more important than cephalopod species in the diet of the marine tucuxi. Back calculations of prey sizes indicated that they feed mainly on young specimens. The present study provided additional information on the feeding habits of the marine tucuxi dolphin.

The north-east Atlantic grey seal, Halichoerus grypus, is widely distributed along the European coastline from northern Russia to France, with the core population centred around Scotland. To date, very little is known of the diet of the species at the southern margin of the species range. However, because grey seal numbers have been increasing over the last few decades in France, the issue of their potential interactions with coastal fisheries is frequently raised. The diet of grey seal in the Molène Archipelago was investigated by combining scat, stomach content and fatty acid analyses, since all three approaches have complementary potentials to reveal feeding habits of a predator. A total of 145 scats mostly of moulting adult males, 14 stomach contents of yearlings and 14 blubber samples from animals of all ages were analysed following standard methodologies. Scats revealed a diet mainly constituted of 50.6% by mass (M) of wrasse, Labridae (mostly Labrus bergylta), 20.7%M conger eel, Conger conger, and 11.9%M sea bass, Dicentrarchus labrax. Stomach contents were made up of 52.3%M cuttlefish, Sepia officinalis, 9.5%M sole, Solea solea, and 9.4 %M conger eel. All these prey are different from the diet observed in core areas. Fatty acid analysis from the blubber confirmed that the diet differed between the Molène Archipelago and one of the Scottish breeding sites. It also showed that most of the inter-individual variability was explained by variation in seal body masses, which could be linked to behavioural ontogeny of foraging strategies. Most of the prey species identified in the food of the grey seal in Brittany are also targeted by professional and/or recreational fisheries in the area; additionally, several prey size-ranges also partly overlap with marketed size-ranges for several species.

The patterns of genetic differentiation and levels of genetic diversity among striped dolphin (Stenella coeruleoalba) populations from the North Atlantic Ocean (N=45 individuals) and the central and western Mediterranean Sea (N=78) were investigated using five polymorphic microsatellite loci. A North Pacific sample (N=14) was added as an out-group. Two of the markers were tetranucleotide repeats tested for the first time in this species. The Mediterranean, Atlantic and Pacific samples displayed a mean number of alleles per locus of 11.2, 13.4, and 9.6 respectively, suggesting a high but variable polymorphism across loci. The Mediterranean sample displayed particular characteristics: (i) the lowest allelic richness and expected heterozygosity (HeMediterranean=0.76, while HeAtlantic=0.83 and HePacific=0.85); (ii) a significant departure from Hardy–Weinberg equilibrium (P<0.001; FIS=0.050); and (iii) a significant linkage disequilibrium between two pairs of loci. These last two features, present neither in the Atlantic sample nor in the Pacific one, suggest that the western Mediterranean population might possibly be further subdivided. Significant genetic differentiation was detected between the Mediterranean and Pacific populations, and between the Mediterranean and Atlantic populations. However, pairwise Wright's FST was not significantly different from zero between the two geographically isolated Atlantic and Pacific populations.

Skulls of 153 porpoises from the Sea of Azov and the Black Sea were studied. Thirty-seven skull measurements were examined. Skull growth in porpoises can be divided into five periods. The greatest changes in growth patterns occur after the first weeks of life. A ‘relay effect’ in growth of some structures (e.g. rostrum) was observed. Individual variation usually increases when a given structure grows intensively; however, some structures are highly variable over the entire lifespan. Sexual dimorphism is demonstrated in most of the measurements in adult animals. Temporal variation is minor. Skull structures are characterized by six types of allometry; three of them demonstrate drastic changes of allometry during lifespan, thus requiring two allometric equations to describe them. Skull proportions change critically during the first weeks of life. Six groups of correlated measurements differing in the pattern of correlation links during ontogeny were identified. Three factors play the most important roles in forming the definitive skull proportions: correlation between adjacent structures, impact of total skull size and inclusion in a certain functional complex.

This study provides the first compilation on age and growth of some delphinids in south-eastern Brazil (18°25′S–25°45′S). A total of 154 delphinids were reported: 44 Atlantic spotted dolphin Stenella frontalis; 36 bottlenose dolphin Tursiops truncatus; 26 ‘Brazilian’ common dolphin Delphinus sp.; 20 rough-toothed dolphin Steno bredanensis; 16 Fraser's dolphin Lagenodelphis hosei; 3 false killer whale Pseudorca crassidens; 3 unidentified Stenella sp.; 2 pantropical spotted dolphin Stenella attenuata; 2 short-finned pilot whale Globicephala macrorhynchus; 1 spinner dolphin Stenella longirostris; and 1 striped dolphin Stenella coeruleoalba. Age was estimated by counting the number of growth layer groups present in the dentine in 74.5% of the sample. The growth of 92 individuals of the first five species was determined by the Gompertz model to length-at-age data. Stenella frontalis—the oldest specimen was 23 y and the asymptotic length of 224.4 cm predicted by growth curve occurred at about 20 y; T. truncatus—the oldest specimen was 26 y and the asymptotic length of 301.3 cm predicted by growth curve occurred at about 20 y; Delphinus sp.—the oldest dolphin was 18 y and the asymptotic length of 215.9 cm predicted by growth curve occurred at about 5–6 y; S. bredanensis—the oldest specimen was 24 y and the asymptotic length of 258.1 cm predicted by growth curve occurred at about 10 y; L. hosei—the oldest specimen was 19 y and the asymptotic length of 231.2 cm predicted by growth curve occurred at about 7–8 y. Only age was estimated for the other species. The age-at-length data for S. frontalis, Delphinus sp., S. bredanensis and L. hosei were consistent, suggesting a good agreement with previous work on these species. For T. truncatus, the age at asymptotic length obtained in this study might be confirmed by increasing the sample size. The information currently presented will contribute to further life history research of delphinids on the western south Atlantic coast.

Cytokines are important cell mediators involved in immune responses. Their expression can be modulated by numerous factors, including stress. The aim of this study was to compare cytokine mRNA expression from harbour porpoises exposed to different environments. Blood samples were taken from two healthy porpoises living in captivity at the Fjord and Belt Centre Kerteminde, Denmark, and from four wild porpoises accidentally caught in Danish waters. Real-time RT-PCR was used to quantify the transcription of interleukin-(IL)-1β, IL-2, -4, -6, -10, tumour necrosis factor-(TNF)-α, transforming growth factor-(TGF)-β and the acute phase protein haptoglobin. This revealed downregulation of the pro-inflammatory cytokines IL-1β, IL-2, IL-6 and TNFα, and a switch towards the T-helper-cell-(Th)2- and Th3-cytokines, IL-4 and TGFβ, in blood samples of the wild-captured animals. This indicated a shift towards immunomodulatory cytokines. In addition, cortisol levels were increased in the wild-caught porpoises. These results are suggestive of stress-induced modulation of the immune responses in the accidentally caught animals. The current study indicates that the expression pattern of these cytokines and the estimation of the Th1- to Th2- and Th3-cytokine mRNA ratios might be a useful indicator to analyse the influence of stress on the immune system in harbour porpoises.