Pathological findings in bycaught harbour porpoises (Phocoena phocoena) from the coast of Northern Norway

Abstract

Due to little prior knowledge, the present study aims to investigate the health status of bycaught harbour porpoises from the northernmost Arctic Norwegian coastline. Gross, histopathological and parasitological investigations were conducted on 61 harbour porpoises (Phocoena phocoena phocoena) accidentally captured in fishing gear from February to April 2017 along the coast of Northern Norway. Most animals displayed a good nutritional status, none were emaciated. Pulmonary nematodiasis (Pseudalius inflexus, Halocercus invaginatus and Torynurus convolutus) was found in 77% and associated with severe bronchopneumonia in 33% of the animals. The majority (92%) had parasites in the stomach and intestine (Anisakis simplex sensu stricto (s. s.), Pholeter gastrophilus, Diphyllobothrium stemmacephalum, Hysterothylacium aduncum and Pseudoterranova decipiens s. s.). The prevalence of gastric nematodiasis was 69%. In the 1st stomach compartment A. simplex s. s. was found in 30% of the animals, causing severe chronic ulcerative gastritis in 23%. Campula oblonga infected the liver and pancreas of 90% and 10% of the animals, respectively, causing severe cholangitis/pericholangitis/hepatitis in 67% and moderate pancreatitis in 10% of the animals. Mesenteric and pulmonary lymphadenitis was detected in 82% and 7% of the animals, respectively. In conclusion, the major pathological findings in the investigated Arctic porpoises were parasitoses in multiple organs with associated severe lesions, particularly in the lung, liver and stomach. The animals were generally well nourished and most showed freshly ingested prey in their stomachs. The present study indicates that the harbour porpoises were able to tolerate the detected parasitic burden and associated lesions without significant health problems.

Causes of Death and Pathological Findings in Stranded Harbour Porpoises (Phocoena phocoena) from Swedish Waters

“…Six porpoises in this study were collected from the overlapping area of suggested population management borders for the Belt Sea and Baltic Sea porpoise populations (Figure 1) and genetic analyses are ongoing to determine the origin of these animals. While results from this study originate primarily from animals the North Sea and Belt Sea populations, findings are also similar to previous findings in porpoises from other parts of the Baltic Sea [25]. Our findings therefore likely give indications of the causes of morbidity and death for the Baltic Sea population, but comparisons should be carried out cautiously as habitats and conditions differ between regions.…”

“…Although 36% of porpoises examined for presence of biliary trematodes had at least a mild burden, infections were generally considered incidental findings. These findings are similar to the 42.2% prevalence reported from porpoises from British waters [42] but differ from bycaught porpoises examined in northern Norway where 90% of animals examined were parasitized with Campula oblonga and two thirds exhibited severe associated cholangitis and hepatitis [25].…”

“…While a small proportion of animals may have been mistakenly assigned to this diagnosis class if cause of death was missed during post-mortem examination, our conservative definition of 'probable bycatch' likely led to the incorrect exclusion of a number of animals from this category. Recent studies of bycaught animals show that these porpoises often have concurrent morbidities and/or are in compromised nutritional condition [25,27]. Thus, even cases of probable bycatch reported here are likely an underestimate of the true number in our sample.…”

Evolutionary history and seascape genomics of Harbour porpoises (Phocoena phocoena) across environmental gradients in the North Atlantic and adjacent waters

“…It belongs to the Phocoenidae family, a group of seven species (Ben Chehida et al, 2020) containing some of the most threatened cetaceans (Carlén, Nunny & Simmonds, 2021): the Vaquita (Phocoena sinus ), one of the most endangered mammals on planet earth, with a population size of ~10 individuals (Jaramillo- Legorreta et al, 2019), and the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis), with only ~1,000 individuals extant (Zhao et al, 2008). Porpoises are mainly affected by incidental bycatch (Brownell et al, 2019), pollutants such as PCBs (Berggren et al, 1999;Karlson et al, 2000), parasites (Dzido et al, 2021;Reckendorf et al, 2021;Ryeng et al, 2022), and noise pollution issued from offshore infrastructure developments, shipping routes and underwater explosions (Siebert et al, 2022). Harbour porpoises inhabit coastal and shelf waters across the Northern hemisphere and at least three subspecies have been described:P.p.…”

Evolutionary history and seascape genomics of Harbour porpoises (Phocoena phocoena) across environmental gradients in the North Atlantic and adjacent waters

“…It belongs to the Phocoenidae family, a group of seven species (Ben Chehida et al, 2020) containing some of the most threatened cetaceans (Carlén, Nunny & Simmonds, 2021): the Vaquita (Phocoena sinus ), one of the most endangered mammals on planet earth, with a population size of ~10 individuals (Jaramillo- Legorreta et al, 2019), and the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis), with only ~1,000 individuals extant (Zhao et al, 2008). Porpoises are mainly affected by incidental bycatch (Brownell et al, 2019), pollutants such as PCBs (Berggren et al, 1999;Karlson et al, 2000), parasites (Dzido et al, 2021;Reckendorf et al, 2021;Ryeng et al, 2022), and noise pollution issued from offshore infrastructure developments, shipping routes and underwater explosions (Siebert et al, 2022). Harbour porpoises inhabit coastal and shelf waters across the Northern hemisphere and at least three subspecies have been described:P.p.…”