Food abundance influences the distribution of living organisms and is essential to their vital activities, including reproduction (Costa, 2009). Global climate variation has influenced prey availability, through changes in environmen- tal factors, with cascading effects in marine ecosystems (Doney et al., 2012). Some effects of climate variability have been observed in the western Antarctic Peninsula (WAP) region. Changes in species composition at the base of the food web, with an increase in the abundance of the small cryptophytes to the detriment of the larger diatoms, have been observed in tandem with warming in the region and consequent changes in ice coverage area and timing of the seasonal cycle (e.g., Mendes et al., 2018; Moline et al., 2004; Schofield et al., 2017). These changes may cascade up the food web and negatively affect the recruit ment and abundance of Antarctic krill (Euphausia superba, hereafter krill) as it does not have the capacity to feed on the small cell size cryptophytes (e.g., Moline et al., 2004). Krill has a vital role in the Southern Ocean ecosystem (e.g., Laws, 1985), as it is the main prey item of many species of penguins, seals, and whales in the region (e.g., Botta et al., 2017; Herr et al., 2016; Nowacek et al., 2011; Reid et al., 2005). Therefore, it is expected that variations in the food web, and particularly in krill abundance, will have consequences for many predator species and the ecosystem as a whole (e.g., Doney et al., 2012; Loeb et al., 2009; Montes-Hugo et al., 2009; Schofield et al., 2017; Seyboth et al., 2017).

Extensive seasonal migrations by humpback whales (Megaptera novaeangliae) have been well documented for decades (Kellogg, 1929; Dawbin, 1966; Clapham & Mead, 1999). Unlike other more oceanic whales with complex seasonal patterns, such as blue (Balaenoptera musculus), sei (B. borealis), and even Bryde’s (B. edeni) whales (Jefferson et al., 2015), the presence of humpback whales in destination areas in high and low latitudes are predominantly regular and predictable. Based on their breeding areas, the International Whaling Commission (IWC) recognizes seven different stocks of humpback whales in the Southern Hemisphere, assigned as Breeding Stocks A to G (IWC, 1998). Genetic studies largely support this separation, although a certain level of gene flow between the different stocks exists (Olavarría et al., 2007; Rosenbaum et al., 2017).

A long-term study of a common bottlenose dolphin (Tursiops truncatus) population inhabiting the Gulf of Guayaquil, Ecuador (2°33′ S, 79°20′W), has been carried out for almost 30 years. Similarly, as in other parts of the world, this population is structured socially and spatially in well-defined subunits or communities. Two of these communities, referred to as Posorja and El Morro, have been studied with major intensity in the last 10 years in the western inner estuary, among others to calculate population parameters that allow assessing their viability in time. Calculated parameters include annual abundance, age and sex composition, annual crude birth rate, calf survival, calf production interval, and average annual mortality/emigration. With these parameters and others derived from other better-studied populations, the trend of both subunits was modeled using the software Vortex. Results show that even under an optimistic scenery both communities will be extinct in the short (Posorja) and mid-term (El Morro), if current stressors continue. Most population parameters calculated in both communities show similar values as in populations elsewhere, but a very low calf survival in Posorja and high mortality/emigration ratios in adults, and probably in juveniles in both communities, contribute to this trend. Population deterioration seems to be the result of different human-induced threats such as fisheries, maritime traffic and others still not well assessed, as well as stochastic demographic events. We recommend taking actions in the short term to halt population decline addressing the major causes of mortality affecting these dolphin communities.

The prevalence of scars and wounds of anthropogenic origin was assessed in seven different coastal bottlenose dolphin communities (Tursiops truncatus) on the south-western coast of Ecuador. Between 2011 and 2017 a total of 117 trips were conducted representing a total sampled distance of 6281 km. Twenty-five of the 189 (13.2%) free-ranging photo-identified dolphins were recorded with dorsal fin damage, V-shaped wounds, sawed edges and deformities in the caudal region. The scarring prevalence ranged from 0 to 44.4% and was associated with either fishing interactions or vessel strikes. Dolphin scarring increased five times in the last 25 years from 2.2 to 11.1% and was correlated with a decrease in population in the inner estuary of the Gulf of Guayaquil. Damaged dorsal fins are associated mainly with fishing gear. V-shaped wounds were recorded in three different communities, Posorja, Estero Salado and Salinas, and given their severity associated with either fishing gear or vessel strikes. During the study period three dolphins were found entangled in fishing gears, two in gillnets and one in a long-line, emphasizing the threats posed by current fishing practice to the species. More effective management measures are urgently needed to reverse the observed population decline. This may include reduction of fishing effort, implementation of area-based approaches to coastal planning (including Marine Protected Area designations) and support for further research to understand the problem. Given the difficulty in taking direct observations, scarring prevalence is proposed as a proxy for estimating boat traffic and fishing gear impacts upon cetaceans.

Lobomycosis-like disease (LLD) is a chronic granulomatous skin disorder that affects Delphinidae worldwide. LLD has been observed in common bottlenose dolphins Tursiops truncatus from the Gulf of Guayaquil, Ecuador, since 1990. Although exogenous factors such as salinity and pollution may play a role in the pathogenesis of this disease in estuarine and coastal dolphin communities, we hypothesized that demography and social behaviour may also influence its epidemiology. To address this issue, the role of social behaviour in the distribution and prevalence of LLD was assessed through hierarchical cluster analysis and spatial distribution analysis in 7 dolphin communities inhabiting the inner estuary. Individuals with LLD lesions were observed in 5 of the 7 dolphin communities, with 13 of the 163 (8%) animals being positive, all adults. Among 8 dolphins of known sex, LLD affected mostly males (86%), who usually were found in pairs. Prevalence was low to moderate (5.1-13%) in dolphin communities where low-rank males had LLD. Conversely, it was high (44.4%, n = 9) in a small community where a high-rank male was infected. LLD affected both dolphins in 2 of the 4 male pairs for which large time series data were available, suggesting horizontal transmission due to contact. Thus, association with LLD-positive males seems to be an important risk factor for infections. Additionally, low-rank males had larger home ranges than high-rank males, indicating that low-status LLD-affected dolphins are likely responsible for the geographic dissemination of the disease in this population.

Spatial distribution, social structure and conservation threats of a small community of bottle[1]nose dolphins, Tursiops truncatus (Odontoceti: Delphinidae) in Ecuador. A resident community of bottle[1]nose dolphins (Tursiops truncatus) was studied irregularly between 2005 and 2018 around the tip of the Santa Elena Peninsula, Ecuador (2°11’ S & 81°0.7’ W). Opportunistic sightings and systematic surveys from the beach and at sea were carried out along 40 km of coast, accounting for 917.2 km of tracking by car from land and 707.4 km of boat tracking by sea. Average group size was 5.31 dolphins/group (SD = 1.97, range 1-10), with no sig[1]nificant changes throughout the study period. From land, however, the group size was underestimated 32 % on the average. This small bottlenose dolphin community currently has only nine individuals, including six adults, one immature and two calves, and is the smallest community within the Gulf of Guayaquil. The encounter rate ranged between 0.03 dolphins/km in the northwestern part and 0.32 dolphins/km in the South, where dolphins concentrate their activities, possibly because human activities are less intense there. Dolphins were generally distributed in the first 200 m from the shore, reaching up to 1 200 m in the Northern shallower part and where port and tourist activities concentrate.