Foraging habits and levels of mercury in a resident population of bottlenose dolphins (Tursiops truncatus) in Bocas del Toro Archipelago, Caribbean Sea, Panama

Abstract

A small and genetically isolated bottlenose dolphin (Tursiops truncatus) population that resides year-round in the Bocas del Toro Archipelago-Panama (BDT). Photoidentification and genetic data showed that this dolphin population is highly phylopatric and is formed exclusively by individuals of the "inshore form". This study aimed to investigate the trophic ecology and mercury concentrations of bottlenose dolphin in BDT to assess their coastal habits. We collected muscle samples (n=175) of 11 potential fish prey species, and skin samples from free-ranging dolphins in BDT (n=37) and La Guajira-Colombia (n=7) to compare isotopic niche width. Results showed that BDT dolphins have a coastal feeding habit, belong to the "inshore form" (δ 13 C=-13.05±1.89‰), and have low mercury concentrations (mean=1,637±1,387 ng g-1 dw). However, this element is biomagnified in the BDT food chain, showing a marginal dolphins health risk (RQ=1.00). These results call for preventive dolphin conservation measures and continue monitoring the pollutant levels.

Tour boats affect the activity patterns of bottlenose dolphins (Tursiops truncatus) in Bocas del Toro, Panama

“…Foraging was the dominant activity for dolphins in this study, therefore, it is reasonable to assume that Dolphin Bay represents an important feeding habitat for dolphins. Barragán-Barrera et al (2019) found that despite the wide availability of other prey species found throughout the archipelago, the dolphins of Bocas del Toro primarily feed on dwarf round herring (Jenkinsia lamprotaenia), a small and low-calorie prey. Repeated disruption to a critical activity like foraging can result in fewer feeding events, which could lead to reduced energy acquisition for individuals.…”

Sex‐specific mercury levels in skin samples of southern elephant seals (Mirounga leonina) at Isla 25 de Mayo (King George Island), Antarctic Peninsula

“…Ten of the samples showed analytical differences above 10%. Because each sample mass was too small to conduct more than two analyses, they could not be considered (Barragán‐Barrera et al, 2019; Seco et al, 2019; Vélez et al, 2021). We suspect this was due to the samples not being well homogenized.…”

“…In the lab and following Vélez et al (2021), skin samples were left to alcohol evaporate and then were homogenized and freeze‐dried for later analysis. Total‐mercury (THg) concentrations of skin were measured using a solid sample atomic absorption spectrometer AMA‐254 (Advanced Altec Mercury Analyzer) as described in Barragán‐Barrera et al (2019). At least two replicates of 1–2 g dry weight (dw) were analyzed for each homogenized and lyophilized sample.…”

“…The reproducibility for duplicate samples was approved when the relative standard deviation (RSD) was below 10%, so the mean value for the two measurements was used for subsequent statistical analyses. However, when RSD was above 10%, a third replicate was analyzed (Barragán-Barrera et al, 2019;Seco et al, 2019;Vélez et al, 2021). To ensure analytical quality of THg measurements, blanks were run at the beginning of each analytical session and certified reference material (CRM) DOLT-3 (Dogfish Liver Certified Reference Material, National T A B L E 1 Total mercury (THg in ng/g dw) concentration in molted skin samples (without attached hair) of southern elephant seals (Mirounga leonina) in the Antarctic Specially Protected Area (ASPA) 132, Isla 25 de Mayo/ King George Island, South Shetland Islands (western Antarctic Peninsula).…”

Peer Review #1 of "Tour boats affect the activity patterns of bottlenose dolphins (Tursiops truncatus) in Bocas del Toro, Panama (v0.1)"

“…Additionally, nuclear and mitochondrial DNA analyses indicate this population is isolated from others in the Caribbean, including the neighboring population of bottlenose dolphins in Costa Rica located 35 km away from the Bocas del Toro archipelago (Barragán- Barrera et al, 2017). Because the small dolphin community of Dolphin Bay shows such high site fidelity, they have become the main target for dolphin watching activities in the area, resulting in the largest dolphin watching fleet in Panama (May-Collado et al, 2012, 2019.…”