Common Dolphins Research Articles

Fishers’ Perception on the Interaction between Dolphins and Fishing Activities in Italian and Croatian Waters

Interactions between fishing and dolphins can be detrimental, since on one hand dolphins can be lethally entangled by nets and trawls, and on the other dolphins can predate fish caught by nets. For dolphins, this interaction can be dangerous as they can be wounded or accidentally killed; for fishers, the predation of their catch results in economic losses due to reduced quantity and/or quality of catches and damage to fishing gear. During July and November 2020, we surveyed the “dolphin–fisheries conflict” through compiling 209 fisher interviews from nine locations in Italy and Croatia. Fishers mentioned the common bottlenose dolphin (Tursiops truncatus) as the species primarily interacting with fishing, with the major issue being catch damage by predation. The interaction probability varied among gears and seasons, with some fishing activities (e.g., passive nets) more affected than others (e.g., bottom trawls), especially in terms of economic loss (1000–10,000 €/year on average). More than 70% of the fishers claimed that dolphin populations have increased over the last 10 years, in different degrees and based on different areas. Dolphin bycatch rates are generally low; however, 34.6% of respondents reported having captured at least one dolphin during their career. The fishers’ attitude towards acoustic deterrents (“pingers”) as a mitigation measure revealed that few of them were aware of these devices or were using them.

Spatial and temporal partitioning of the Western Mediterranean Sea by resident dolphin species

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.

Evaluating the Use of Diazepam in Stranded Dolphins and Porpoises for Husbandry and Veterinary Purposes

We evaluated the use of diazepam (Valium®) during the rehabilitation of odontocetes (dolphins and porpoises) to facilitate husbandry and for veterinary purposes, by analyzing detailed records from a period of 14 years of the treatment of 16 stranded individuals: harbor porpoises (Phocoena phocoena), white-beaked dolphins (Lagenorhynchus albirostris), a common dolphin (Delphinus delphis), and a striped dolphin (Stenella coeruleoalba). Diazepam was used occasionally (once per case or for a few days at a time) to facilitate husbandry, including for managing stressful and transitional circumstances and during transport. It was also used occasionally (once per case) for veterinary purposes, such as to reduce stress or to facilitate x-ray scanning, gastroscopy, blood sampling, or wound treatment. Diazepam was found to be effective as an anti-anxiety drug, to cause drowsiness (i.e., reduce activity levels), as a muscle relaxant, and as an appetite stimulant. The doses used were similar for husbandry and veterinary purposes (0.03 to 0.44 mg/kg body weight), and the drug was administered almost exclusively orally (via fish) or via intramuscular injection.

Recent occurrence of marine mammals and sea turtles off Angola and first report of right whales since the whaling era

AbstractMarine megafauna occurrence was recorded in the deep-sea region bordering the abyssal plain ~400 km north-west of Luanda, Angola. The survey took place during an Environmental Baseline Study (EBS), prior to drilling exploration activities, with the goal of characterizing the habitat and biodiversity of the region. Offshore shipboard surveys were conducted during September 2018 in water depths ranging from 2350–3850 m. We recorded daytime sightings of marine mammals and sea turtles and at night made audio recordings using passive acoustic monitoring (PAM) methods focused on capturing the sounds of vocalizing marine mammals. A variety of species were visually detected, including the humpback whale (Megaptera novaeangliae), sperm whale (Physeter macrocephalus), common dolphin (Delphinusspp.), striped dolphin (Stenella coeruleoalba), Atlantic spotted dolphin (S. frontalis), and olive ridley turtle (Lepidochelys olivacea). Acoustic click bouts similar to those made by several odontocete species, possibly including beaked whales, were recorded within the 25–48 kHz range. The humpback whale was the most frequently sighted species, accounting for 56% of mammal sightings, indicating a potential far offshore migratory habitat in this region. Most notably, right whales (probableEubalaena australis) were visually observed. This is the first confirmed record of right whales in Angolan waters since the early 1900s. As development expands in this offshore region, these data can usefully inform future monitoring and mitigation strategies focused on minimizing impacts to wildlife.

Tension pneumothorax in small odontocetes.

Pneumothorax, the accumulation of air in the pleural cavity, occurs when air enters the pleural space by the pleuro-cutaneous, pleuro-pulmonary, or pleuro-oesophageal-mediastinal route. Tension pneumothorax is an infrequent and severe form of pneumothorax where a positive pressure in the pleural space is built up during at least part of the respiratory cycle, with compression of both lungs and mediastinal vessels, and, if unilateral, with midline deviation towards the unaffected hemithorax. We describe 9 cases of tension pneumothorax in 3 species of small cetaceans (striped dolphin Stenella coeruleoalba, common dolphin Delphinus delphis, and common bottlenose dolphin Tursiops truncatus) from the western Mediterranean coast of Spain, and one case from a dolphinarium. Computed tomography (CT) imaging performed in 2 carcasses before necropsy showed lung compression, midline deviation, and pressure on the diaphragm, which was caudally displaced. Tension pneumothorax was recognized at necropsy by the presence of pressurized air in one of the hemithoraces. Seven of the pneumothorax cases were spontaneous (2 primary and 5 secondary to previous lung pathology). In the other 2 dolphins, the pneumothorax was traumatic, due to oesophageal-pleural perforation or rib fractures. We hypothesize that pneumothorax in dolphins is predominantly tensional because of their specific anatomical and physiological adaptations to marine life and the obligate exposure to extreme pressure changes as diving mammals.

Helicobacter delphinicola infection and the risk of gastric disease in common bottlenose dolphin.

Gastritis and gastric ulcers are well-recognized conditions in cetaceans; bacteria of the genus Helicobacter are considered the primary cause of these diseases. Dolphins have been shown to be susceptible to infection by at least 2 gastric species of Helicobacter, H. cetorum and H. delphinicola, both of which are closely related to the human pathogen H. pylori. In the present study, we evaluated the carriage rate and relationship to gastric disease of H. cetorum and H. delphinicola, based on a study population of 82 dolphins maintained at 21 facilities in Japan. Of these 82 dolphins, 79 (96.3%) and 45 (54.9%) were positive for H. cetorum and H. delphinicola, respectively; H. delphinicola infection was significantly associated with chronic gastric diseases (odds rate: 5.9; 95% CI: 2.1-16.9), but no such association was detected for H. cetorum. Of the 21 facilities, 20 (95%) and 11 (55%) housed H. cetorum- and H. delphinicola-positive dolphins, respectively, and our study suggested that the transmission between dolphins occurs quickly within pools. These findings indicate that methods will need to be established to prevent the transmission of Helicobacter infections within facilities housing dolphins.

The “Social-Friendly Learning-Instructional Theory”

The advanced “Social-Friendly Learning-Instructional Theory” (ST) is based on (and employs use of): 1) the Mebir innate response, and on 2) “The Peaceful Composure Theorem” (PCT) that shows humans to be loving, non-competitive and non-aggressive. (PCT) is derived from a) two new theories of evolution, b) the study of the egalitarianism of nomadic hunters and gatherer society, and c) the common bottlenose dolphins peaceful composure between conspecifics and unique exceptional evolutionary freedom.

Characterising injuries and pathologies of common dolphin Delphinus delphis mortalities in the South Australian Sardine Fishery

Mortality of dolphins in fishing operations is often under-estimated, as shown by studies of beach-washed carcasses. Linking evidence obtained during necropsies with fishing method is fundamental to understanding the extent of mortality and the manner in which animals die. The South Australian Sardine Fishery (SASF) has operated a purse-seine industry since 1991. This study characterised injuries, pathological changes and life history of 49 dead dolphins collected from SASF during 2006-2019. Histology examination was conducted on 25 animals. Neonates, calves and juveniles accounted for 63% of the sample. Of mature females (n = 14), 11 were pregnant or lactating, with cryptic mortality estimated to be 20% of dolphins studied. Body condition was robust in 48 dolphins. Net marks were seen on 82%, mostly on the head, trunk and peduncle. Broken/missing teeth were noted in 63%. All dolphins had subdermal haemorrhage (moderate to severe in 96%), particularly around the head. Deep haemorrhage was common, including around occipital and flipper condyles, and organs. Copious fluid was present in the thoracic (pleural) and abdominal (ascites) cavities of half of the dolphins. Within the lungs, watery fluid and froth were observed in 100 and 39%, respectively. Recent bone fractures were documented in 43% of dolphins, mostly associated with haemorrhage. Severe blunt trauma appeared to be the primary cause of death, and 10 dolphins also had other significant pathologies. Visceral organ congestion and mild cardiomyopathy were observed. Stomachs contained prey remains in 75% of cases. The results of this study may help identify unreported purse-seine mortalities washed up in South Australia and elsewhere.

Pathology of short-term dorsal fin tag-attachments in tagged and re-stranded short-beaked common dolphins Delphinus delphis on Cape Cod, MA

Odontocetes are difficult to study in the wild, making tagging and remote tracking a valuable practice. However, evaluations of host responses at tagging sites have been primarily limited to visual observations in the field. Here we explore the macro- and microscopic pathology of dorsal fin tag attachments in 13 stranded and released short-beaked common dolphins Delphinus delphis from Cape Cod, MA that later re-stranded and died or were euthanized 1-28 d post-tagging. Tags were attached to stranded dolphins’ dorsal fins using 2 methods: core biopsy or piercing. Grossly, the piercing method resulted in epidermal compression into the dermis. One tag site had a necrotic border 28 d after application. Grossly, the biopsy method resulted in minimal to no tissue reaction. Two tag sites had granulation tissue accumulation 4 and 12 d after tagging. Histopathologic findings for all tag types and animals consisted of focal epithelial loss, dermal edema, perivascular edema, inflammation and hyperplasia, and inter- and extracellular edema in the adjacent epidermis. Minor expected pathological changes given the procedure were also observed: superficial epidermal necrosis in 3 cases, and superficial bacterial colonization in 2 cases. There was no evidence of sepsis and tagging was not related to cause of re-stranding or death in any case. These gross and histopathologic findings support previous observational conclusions in small delphinids that with appropriate sterile technique, the impacts of single pin dorsal fin tagging on the animal can be minimal and localized. Of the 2 methods, core biopsy may be a better tagging method.

Occurrence, site fidelity, and abundance of bottlenose dolphins (Tursiops truncatus) in the Western Ligurian Sea

This study represents the first complete assessment of the population dynamics and residency of common bottlenose dolphins in the Western Ligurian Sea, an area where bottlenose dolphin sightings have been rare in the past. Despite being greatly affected by human pressure, information about this population is poor and sporadic. The study took place from April 2018 to December 2020. One hundred and seventy‐one dedicated boat surveys were performed year‐round resulting in 95 sightings, and 123 individuals were identified through mark‐recapture photo‐identification techniques. Dolphins were found to be present year‐round. Most of the animals (79) used the area sporadically and only 19.5% of the dolphins (24) were seen regularly. Bottlenose dolphin abundance was estimated at 248 using open POPAN population models (CI 95% = 217–284). These results help fill a knowledge gap by highlighting the regular presence of bottlenose dolphins in the study area. Moreover, they represent a baseline for future studies investigating abundance trends and the conservation status of this population

Audiograms and click spectra of seven novel and seldom-tested odontocetes

The use of auditory evoked potentials has been promoted as a means by which to collect audiometric information from odontocete cetaceans that are rarely encountered in stranding situations. This article presents the results of auditory evoked potential hearing tests collected from stranded odontocetes over nearly a decade. For six species, no audiograms previously existed – the dwarf sperm whale (Kogia sima), pygmy sperm whale (Kogia breviceps), northern right whale dolphin (Lissodelphis borealis), melon-headed whale (Peponocephala electra), long-beaked common dolphin (Delphinus capensis), and Atlantic spotted dolphin (Stenella frontalis). Additional hearing information was gathered for the pygmy killer whale (Feresa attenuata), a species for which only two prior audiograms had been collected. Audiograms for the delphinids demonstrated a typical dolphin-like form with upper-frequency limits of hearing > 149 kHz, except for the pygmy killer whales whose upper-frequency limit was between 103-107 kHz. The kogiid audiograms had a narrower region of increased sensitivity (80-128 kHz) closely aligned with their narrowband, high-frequency echolocation signals. Distinctions between kogiids and delphinids existed in the latencies of peaks of click-evoked auditory brainstem responses, with longer interwave intervals between P4 and N5 in the kogiids (mean of 0.60 ms vs. a mean of 0.37 ms in the delphinids). Modulation rate transfer functions collected in three of the species, suggested group-wide similarities in temporal processing capabilities.

Acoustic detection of bottlenose dolphin depredation on nets and implications for conservation

Abstract Understanding the depredation process is pivotal to the management of conflicts between wildlife and human activities. Depredation by marine mammals on fisheries occurs when animals ‘steal’ fish from the fishing gear, causing catch loss and damage to gear and catches. The common bottlenose dolphin is a vulnerable species and is the main depredator of coastal static net fisheries in the Mediterranean Sea. The nature and extent of the phenomenon is still poorly understood since evidence is often incomplete or inconsistent mostly due to the different methods used to measure depredation. Here, passive acoustic monitoring devices were used to estimate the consistency between dolphin acoustic detection in proximity to the net and direct dolphin observations and catch measurements at different sites in Sardinia (north‐western Mediterranean Sea). Further, some factors influencing depredation (fishing duration and fishing net length) and changes in catch amount and composition were evaluated. The frequency of dolphin detection based on direct dolphin observations was significantly lower than that based on acoustic monitoring; the latter was related to the amount of catch. Thus, the measurement of catch was more realistically related to depredation than direct dolphin observations. Further, dolphin depredation was related to the duration of the fishing operation. The measure of depredation and catch loss provided here can be used to realistically estimate the damage suffered by fishers and provide preliminary insights to guide the development of an approach for sustainable coexistence between dolphins and fisheries.

Bottlenose dolphins share fish farm areas while maintaining sexual segregation: Investigating group memberships through spatially and temporally explicit parameters

Abstract Group membership is a key attribute of animal societies and central to the study of social structure in several taxa. However, social structure analyses are sensitive to the way data are collected and associations defined. In this study, a time–space method was used to investigate the social structure of common bottlenose dolphins Tursiops truncatus observed and photographed across 7 years in the semi‐enclosed Gulf of Corinth, Greece. Instead of adopting traditional group definitions, individuals were considered as being members of the same group if photographed within a specific time and space window. This approach can be applied post hoc across studies and can offer advantages under challenging sampling conditions (e.g. when dealing with groups spread over vast areas or when group membership is otherwise hard to assess). Dolphins were mostly found around coastal cage aquaculture facilities farming European sea bass Dicentrarchus labrax and gilthead seabream Sparus aurata. Dolphins formed clusters largely or entirely composed of individuals of the same sex, suggestive of sex‐based homophily. Habitat partitioning was not detected: there was substantial spatial overlap among dolphin clusters, with all individuals using a relatively small area in the northern portion of the Gulf, where most of the productive fish farms were located. Associations between females were stronger than those between males, and daughters tended to stay in the group of their mothers. Sex‐based social clustering may allow females and calves to limit interactions with potentially aggressive males, while individuals of both sexes benefit from prey concentrated around fish farms. Adaptation to foraging around farms can result in trade‐offs between the costs and benefits of nourishment and social interaction. This may have both positive or negative effects on the animals that should be considered in the context of ensuring their favourable conservation status.

An epigenetic DNA methylation clock for age estimates in Indo-Pacific bottlenose dolphins (Tursiops aduncus).

Knowledge of an animal's chronological age is crucial for understanding and predicting population demographics, survival and reproduction, but accurate age determination for many wild animals remains challenging. Previous methods to estimate age require invasive procedures, such as tooth extraction to analyse growth layers, which are difficult to carry out with large, mobile animals such as cetaceans. However, recent advances in epigenetic methods have opened new avenues for precise age determination. These 'epigenetic clocks' present a less invasive alternative and can provide age estimates with unprecedented accuracy. Here, we present a species-specific epigenetic clock based on skin tissue samples for a population of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in Shark Bay, Western Australia. We measured methylation levels at 37,492 cytosine-guanine sites (CpG sites) in 165 samples using the mammalian methylation array. Chronological age estimates with an accuracy of ±1 year were available for 68 animals as part of a long-term behavioral study of this population. Using these samples with known age, we built an elastic net model with Leave-One-Out-Cross-Validation, which retained 43 CpG sites, providing an r= 0.86 and median absolute age error (MAE)=2.1 years (5% of maximum age). This model was more accurate for our data than the previously published methylation clock based on skin samples of common bottlenose dolphins (T. truncatus: r= 0.83, MAE=2.2) and the multi-species odontocete methylation clock (r= 0.68, MAE=6.8), highlighting that species-specific clocks can have superior performance over those of multi-species assemblages. We further developed an epigenetic sex estimator, predicting sex with 100% accuracy. As age and sex are critical parameters for the study of animal populations, this clock and sex estimator will provide a useful tool for extracting life history information from skin samples rather than long-term observational data for free-ranging Indo-Pacific bottlenose dolphins worldwide.

Tursiops truncatus nuuanu, a new subspecies of the common bottlenose dolphin from the eastern tropical Pacific

Tursiops truncatus nuuanu, a new subspecies of the common bottlenose dolphin from the eastern tropical Pacific

Reproductive biology of female common dolphins (Delphinus delphis) in New Zealand waters

Reproductive biology was assessed in 106 female common dolphins (Delphinus delphis) examined post-mortem from stranding and bycatch events along the New Zealand coastline between 1997 and 2019. The average age (ASM) and length (LSM) at sexual maturity was estimated at 7.5 years and 183.5 cm, respectively. The total number of corpora in mature individuals increased with age and appeared to persist throughout life. Ovarian asymmetry was apparent, with the left ovary displaying higher rates of ovulation, and a maximum of 19 corpora recorded for a 24-year-old female. The estimated ovulation and annual pregnancy rates for mature females were 0.39 year−1 and 30%, respectively. Conception and calving occurred year-round, with a weak seasonal increase observed in late austral spring and early austral summer. As these data did not clearly show whether seasonality was present, the gestation, lactation, and resting periods were calculated as either 12.6 or 12.8 months based on the presence/absence of seasonality, respectively. Similarly, calving interval ranged from 3.15 to 3.2 years, depending upon whether seasonality was considered. The estimated LSM of the New Zealand population aligns with other populations globally, although the estimated ASM is younger by approximately 6 months. Other reproductive parameters align with Northern Hemisphere populations, although demonstrate variation, which may reflect adaptations to local conditions such as water temperature and prey availability. As the species is subject to anthropogenic impacts including pollution and bycatch, we suggest our findings be used as a baseline with which to monitor trends in population parameters.

High similarities in dorsal fin ratios of common bottlenose dolphins (Tursiops truncatus) in the Caribbean Sea

AbstractDorsal fins, one of the most notable dolphin's physical features, play important kinematic and hydrodynamic roles and are related to physiological and environmental adaptation processes. Differences in dorsal fin shape have been recently associated with geographic variation, habitat specialization between ecotypes, and ontogenetic factors. We studied dorsal fin variation across several common bottlenose dolphin populations in the Caribbean. A total of 252 dorsal fin photographs from eight coastal regions in the Caribbean were selected for analysis. Dolphin dorsal fin proportions were compared among regions and compared with data previously collected from Holbox, Mexico. Dorsal fin models were constructed for each region. We found that across the Caribbean, coastal bottlenose dolphins exhibit low variation in dorsal fin shape, with the most common dorsal fin pattern having low and triangular shapes, two traits that greatly contrast with the oceanic ecotype. Also, significant differences in overall dorsal fin proportions found among some adjacent groups support the hypothesis that subgroups could be present even within extremely short geographical distances ‐ as has been previously documented. The results of this study can be implemented in population monitoring efforts worldwide, as it uses free software and provides a step‐by‐step guideline to analyze the data.

The oxygen minimum zone relative depth is a key driver of dolphin habitats in the northern Humboldt Current System

Highly mobile odontocetes need habitats with environmental conditions with the potential of aggregating enough and high-quality prey, to maximize foraging success. Until now, the characterization of those habitats was in terms of physical and biological indicators of high production, capable of attracting and sustaining prey. Nevertheless, there has been no approach to quantifying the effects of a biophysical characteristic of the ocean with proven effects on the vertical distribution of prey for cetaceans: The oxygen minimum zone (OMZ) depth. In the northern branch of the Humboldt Current System off Peru (~6-18° S), a shallow OMZ (30-50 m) affects the distribution of the Peruvian anchovy (Engraulis ringens), main prey for several marine predators, including dolphins. We hypothesized these predators would aggregate in productive areas, but with preference for places where the relative OMZ depth can constrain prey vertically, making it more accessible and maximizing foraging success. We fitted Bayesian habitat models for three dominant odontocete species in this region, with multiple combinations of environmental covariates, smoothing techniques, and temporal and spatial random effects. Cetacean data came from 23 dedicated surveys spanning 2001-2019. Habitat predictors included the spatial anomalies of sea surface temperature, surface chlorophyl-a, pycnocline depth and OMZ depth. Dusky (Lagenorhynchus obscurus) and common dolphins (Delphinus delphis) preferred productive, cold areas with a very shallow OMZ, regardless of the season, while bottlenose dolphins (Tursiops truncatus) aggregated in both cold and warm waters, also with shallow OMZ. The former two species of higher metabolic demands would maximize energy intake by selecting areas with highly aggregated prey, while the latter, of more moderate metabolic needs and more diverse prey, would exploit less restricted habitats.

Common dolphins (Delphinus delphis) in Israel: Unique dynamics of a critically endangered population

The most eastern population of common dolphins (Delphinus delphis) in the Mediterranean Sea inhabits the southern coastal waters of Israel. They are mainly observed in the shallow waters off Ashdod and Ashkelon, between the 15-30 m isobaths, with no reported observations north or west of this area. These dolphins were observed and studied year-round between 2016-2021 using boat-based surveys and photo identification methods. Common dolphins were encountered and photographed 43 times during the study period, resulting in 2,851 identifications of 25 distinctive mature individuals and 12 calves. Most individuals (62%) were sighted over multiple years, with high yearly and monthly sighting rates, indicating long-term site fidelity and residency. Closed population mark-recapture models estimated a total abundance of 25 (95% CI 24 – 37) individuals in 2016 that declined to only 15 (95% CI 15 – 15) individuals in 2021. Social network analysis described these remaining individuals as one closed and well-associated social unit. Survival probabilities for this population appeared lower than those of other delphinid populations. The decrease in their abundance, coupled with their apparent isolation level, qualifies the local population for a re-assessment of their conservation status. This study first describes the Israeli local population of common dolphins, their dynamics and an assessment of their status based on the IUCN Red List framework.

Microplastics in gastric samples from common bottlenose dolphins (Tursiops truncatus) residing in Sarasota Bay FL (USA)

The oceans contain trillions of plastic particles, mostly microplastics (i.e., particles < 5 mm diameter; 92.4% of plastic particles), which have been detected in organisms at all levels of the marine food web. The ubiquity of marine plastic debris has created a monumental environmental pollution problem with extensive public health consequences, as more than 40% of the world’s population lives near the coast and shares coastal resources. For decades, common bottlenose dolphins (Tursiops truncatus) have been used as sentinels of marine pollution risks for coastal communities that rely on seafood. Recently, prevalent phthalate exposure was documented in bottlenose dolphins residing in Sarasota Bay, FL, at concentrations exceeding those of human reference populations. While the source of their exposure is uncertain, the types of compounds detected suggest a plastic origin. The objective of this study was to screen for plastic ingestion among free-ranging dolphins in Sarasota Bay using gastric samples collected during catch-and-release health assessments. Gastric samples were collected from seven live bottlenose dolphins in 2019, and suspected microplastic particles were detected in all samples. The number of particles per sample ranged from <10 to >100, and the most common types were transparent films and white foams. Similar to other marine mammal studies, fibers were also present. Given that dolphins are likely exposed to microplastics via contaminated prey, findings from this and additional studies will help to evaluate the potential of contaminated seafood as an additional source of microplastic exposure for humans, as well as help to inform intervention and risk communication needs regarding seafood safety.