[MARMAM] New papers on harbor porpoises from the southern North Sea

IJsseldijk, L.L. (Lonneke) L.L.IJsseldijk at uu.nl
Mon Dec 7 04:37:00 PST 2020


Dear colleagues,

We are pleased to announce the two recent publications as part of the stranding research on harbor porpoises in the Netherlands:

IJsseldijk, L.L., Scheidat, M., Siemensma, M., Couperus, B., Leopold, M., Morell, M., Gröne, A., and Kik, M.J.L. (2020) Challenges in the Assessment of Bycatch: Postmortem Findings in Harbor Porpoises (Phocoena phocoena) Retrieved From Gillnets. Veterinary Pathology

Available at: https://journals.sagepub.com/doi/full/10.1177/0300985820972454

Abstract: Bycatch is considered one of the most significant threats affecting cetaceans worldwide. In the North Sea, bottom-set gillnets are a specific risk for harbor porpoises (Phocoena phocoena). Methods to estimate bycatch rates include on-board observers, remote electronic monitoring, and fishermen voluntarily reporting; none of these are systematically conducted. Additionally, necropsies of stranded animals can provide insights into bycatch occurrence and health status of individuals. There are, however, uncertainties when it comes to the assessment of bycatch in stranded animals, mainly due to the lack of diagnostic tools specific for underwater entrapment. We conducted a literature review to establish criteria that aid in the assessment of bycatch in small cetaceans, and we tested which of these criteria applied to harbor porpoises retrieved from gillnets in the Netherlands (n ¼ 12). Twenty-five criteria were gathered from literature. Of these, "superficial incisions," "encircling imprints," and "recent ingestion of prey" were observed in the vast majority of our confirmed bycatch cases. Criteria like "pulmonary edema," "pulmonary emphysema," and "organ congestion" were also frequently observed, although considered unspecific as an indicator of bycatch. Notably, previously mentioned criteria as "favorable health status," "absence of disease," or "good nutritional condition" did not apply to the majority of our bycaught porpoises. This may reflect an overall reduced fitness of harbor porpoises inhabiting the southern North Sea or a higher chance of a debilitated porpoise being bycaught, and could result in an underestimation of bycatch rates when assessing stranded animals.


Willems, D., IJsseldijk, L.L., van den Broek, H., and Veraa, S. (2020) Vertebral pattern variation in the North Sea harbor porpoise (Phocoena phocoena) by computed tomography. The Anatomical Record

Available at: https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.24524

Abstract: Vertebral series in the harbor porpoise (Phocoena phocoena) include cervical, thoracic, lumbar, and caudal. In contrast to studying skeletons from museums, in which small bones can be missed, evaluation of full body computed tomography (CT) scans provides an overview of the vertebral column, while maintaining interrelationship of all structures. The aim of this study was to document variations in vertebral patterning of the harbor porpoise via evaluation of CT images of intact stranded harbor porpoises. The harbor porpoises were divided into age classes, based on developmental stage of reproductive organs on postmortem examination and closure of proximal humeral physis on CT. Numbers of vertebrae per series, fusion state of the syncervical, type of first hemal arch, number of double articulating ribs, and floating ribs were recorded based on CT images. Included in the study were 48 harbor porpoises (27 males and 21 females), which were divided in two age classes (27 immatures and 21 adults). Total vertebral count varied from 63 to 68 with vertebral formula range C7T12‐14L12‐16Cd29‐33. Twenty‐five different vertebral formulas were found, of which C7T13L14Ca30 was the most common (n = 8, 17%). Thoracic vertebrae with six, seven, or eight double articulating ribs and zero, one, or two vertebrae with floating ribs were seen. Four different fusion states of the syncervical and four types of hemal arches were recognized. This study showed a great variation in vertebral patterning in the harbor porpoise, with homeotic and meristic variation in the thoracic, lumbar, and caudal vertebral series.

Best wishes,
Lonneke IJsseldijk


Lonneke L. IJsseldijk<https://www.uu.nl/medewerkers/LLIJsseldijk> | Project Manager Cetacean Research | Utrecht University | Veterinary<https://www.uu.nl/organisatie/faculteit-diergeneeskunde> Medicine | Biomolecular Health Sciences | Pathology | Yalelaan 1, 3584 CL Utrecht | room O.170 | (+3130) 253 5312 | (+316) 244 556 98 | l.l.ijsseldijk at uu.nl<mailto:l.l.ijsseldijk at uu.nl>| Follow us @ | Instagram<https://www.instagram.com/strandingresearch> | LinkedIn<https://www.linkedin.com/in/lonneke-ijsseldijk-64014226/> | Online<http://www.uu.nl/strandingsonderzoek>



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