Dear colleagues, On behalf of my co-authors, I am excited to share two recent open-access publications:
Adams, Inge A., Roussouw, Natasha, Reed, Cecile, Ham, Gin S. and Plön, Stephanie. 2025. Long-term host parasite dynamics in eight odontocete species from south-eastern South Africa. *International Journal for Parasitology: Parasites and Wildlife *28: 101133. https://doi.org/10.1016/j.ijppaw.2025.101133 Abstract: Although investigations of stranded and bycaught cetaceans have been conducted since the 1970s, little is known about parasites infecting the 25 species found in the South African subregion. For this study, we retrospectively identified parasites from eight bycaught and stranded odontocete species along the south-eastern coast of South Africa between 1970 and 2015 to produce a list of parasite species affecting southern African odontocetes and examine patterns of infection in host species with regards to age, sex, time intervals and collection method. Parasites were identified in 192 out of the 2599 individuals examined. Previously unreported parasite species were found for several southern African odontocete species, underscoring the importance of museum collections for biological research. Offshore and stranded odontocetes generally had a higher prevalence of parasites, although there were a few exceptions. Binomial logistic regression models showed significantly higher probability of parasitic presence (p < 0.05) in stranded *Delphinus delphis *than bycaught individuals, and significantly lower probability of parasitic presence (p < 0.05) in neonates and calves of stranded *Tursiops aduncus* and *Stenella coeruleoalba *than adult animals. No significant difference (p > 0.05) was detected between the sexes of all odontocete species investigated (p > 0.05). Parasitic prevalence was highest during the most recent years (2000–2015) for half of the odontocete species investigated, in agreement with the models. Accurate morphological identification of parasites affecting marine mammals is essential for comprehending disease epidemiology, assessing the health of cetacean populations, and developing effective conservation and management strategies. And Roussouw, Natasha, Froneman, P. William, Weltz, Kay, Venter, Kirsty, Conry, Danielle, Smale, Malcolm J. and Plön, Stephanie. 2025. Feeding down the food web?! Trophic cascading reflected in the long-term dietary trends of endangered Indian Ocean humpback dolphins *Sousa plumbea *from KwaZulu-Natal, South Africa. *Ecological Indicators* 181: 114442. https://doi.org/10.1016/j.ecolind.2025.114442 Abstract: Approximately 60 % of coastal cetacean species globally are at risk of extinction, despite these organisms role as indicators of Ocean Health. Changing food availability due to overfishing and/or climate change has been identified as one stressor among cumulative impacts on cetacean populations. Using a multi-method approach of analysing stomach contents (n = 107), stable isotopes (n = 30) and blubber thickness (n = 87) data (as a proxy for condition), we investigated long-term dietary trends (1972–2017) of incidentally bycaught Indian Ocean humpback dolphin *Sousa plumbea* off the KwaZulu-Natal coast, South Africa. A total of 64 teleost and three cephalopod species were identified. A diet shift was observed in the stomach contents between 2001 and 2020, with new prey species being recorded, which was validated by the significant difference in prey species diversity over time (p < 0.001). In addition, significant decreases in δ13C signatures between time intervals (p = 0.01), due to differences between the 2011–2020 decade and the 1971–1980 and 1981–1990 intervals, also indicated a change in prey. A significant decrease was found in the mid-dorsal body condition index (calculated using blubber thickness) between the 1981–1990 and 2001–2010 intervals (p = 0.02). Our study provides evidence of a dietary shift in the endangered *S. plumbea* along South Africa’s KwaZulu-Natal coastline from 2001 to 2020, likely driven by declining prey availability resulting from overfishing and/or climate change. This highlights the species’ role as an indicator of environmental change in the coastal zone of the Indian Ocean and the importance of long-term data for assessing Ocean Health in the region. Please reach out if you have any questions: [email protected] Thank you, Stephanie Plön, PhD BioConsult SH, Germany and University of Cape Town, South Africa
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