Crossing boundaries for cetacean conservation: Setting research priorities to guide management of harbour porpoises

Effective management of natural resources involves a multidisciplinary perspective to address complex issues in data poor-environments. With mobile species that do not conform to human-defined borders a cross-boundary approach is essential. There is a continuing concern of ecological sustainability of marine environments, which demands monitoring of ecosystem indicators. Such indicators are increasingly derived from monitoring sentinel species. Harbour porpoises (Phocoena phocoena) are included as indicator species in several national and international agreements. Increasing exposure to anthropogenic stressors may impact harbour porpoise populations. To investigate these risks, a better understanding of threats and their effect is required. This study aimed to identify current knowledge gaps, to predict future pressures or threats, and to define useful conservation indicators to facilitate future research on harbour porpoises in the North Sea, through expert elicitation gained in a two-round Delphi approach. The three most important knowledge gaps addressed were bycatch, population dynamics, and the cumulative effects of multiple stressors. Bycatch was predicted as the highest concern for porpoises in the next 20 years, followed by chemical and noise pollution, respectively. A list of essential indicators aiming to increase understanding of harbour porpoises’ health status was established and studying causes of death, distribution, abundance, habitat use and diet composition were scored as most relevant. These results should guide research focus and management objectives of harbour porpoise populations and the study design could be translated to serve managers in other geographical areas aiming to identify knowledge gaps and defining research priorities for other wildlife species

Spatiotemporal analysis in white-beaked dolphin strandings along the North Sea coast from 1991-2017

The white-beaked dolphin (Lagenorhynchus albirostris) is an endemic species in the North Sea with an estimated population of around 36,000 individuals. Recently, concerns have been raised among conservationists regarding increasing water temperatures as a result of climate change, which could result in a decline in population numbers in certain areas of the white-beaked dolphin’s range. Here we use stranding frequencies of white-beaked dolphins as an indicator of distribution and investigate whether there have been spatiotemporal patterns and changes in stranding frequencies in the south western North Sea in the last 27 years (1991-2017). A total of 407 strandings was recorded and the distribution of stranded animals throughout this period revealed a higher density of animals in the southern countries in earlier years, with slightly increased densities in the north western area more recently. This could be a first indication of a change in habitat use and population distribution from southern to northern regions. A potential explanation for the observed shift is climate change and its effect on prey distribution and availability. This study highlights the potential of using stranding records as a way to collect high resolution spatiotemporal data, making this a valuable addition to surveys of live animals assessing species distribution and abundance. Additional research into metrics such as causes of mortality, life history and diet parameters (all of which are currently largely unknown for this species) would provide a welcome contribution to assess more detailed measures of the status of the population

Spatiotemporal analysis in white-beaked dolphin strandings along the North Sea coast from 1991-2017

The white-beaked dolphin (Lagenorhynchus albirostris) is an endemic species in the North Sea with an estimated population of around 36,000 individuals. Recently, concerns have been raised among conservationists regarding increasing water temperatures as a result of climate change, which could result in a decline in population numbers in certain areas of the white-beaked dolphin’s range. Here we use stranding frequencies of white-beaked dolphins as an indicator of distribution and investigate whether there have been spatiotemporal patterns and changes in stranding frequencies in the south western North Sea in the last 27 years (1991-2017). A total of 407 strandings was recorded and the distribution of stranded animals throughout this period revealed a higher density of animals in the southern countries in earlier years, with slightly increased densities in the north western area more recently. This could be a first indication of a change in habitat use and population distribution from southern to northern regions. A potential explanation for the observed shift is climate change and its effect on prey distribution and availability. This study highlights the potential of using stranding records as a way to collect high resolution spatiotemporal data, making this a valuable addition to surveys of live animals assessing species distribution and abundance. Additional research into metrics such as causes of mortality, life history and diet parameters (all of which are currently largely unknown for this species) would provide a welcome contribution to assess more detailed measures of the status of the population

Mahathir gesa jalin hubungan erat di Tahun Baru Cina

Harbour porpoises are often found to be infected by endoparasites in several organs including the lungs and stomach as well as the heart, liver and ears. Nevertheless there is still little knowledge about the impact, ecology, transmission, and virulence of these parasitic infections. Here, we profile the presence of parasites in 4 frequently infected organs (lungs, stomach, liver and ears) in relation to biological parameters of harbour porpoises stranded along the Dutch coastline between December 2008 and December 2013. We found that parasites were common, with prevalence of 68% in lungs, 74.4% in ears, 26% in stomach and 23.5% in liver. We used generalised linear models to further quantify parasite presence in relation to biological data gathered during necropsy (sex, body length and nutritive condition). Body length (used as a proxy for age) was significant in explaining parasite presence for all organs with increasing probability of having the parasite with increasing body length. For the parasitic infections in the ears and stomach the nutritive condition was an additional significant factor, with a higher probability of parasite presence in porpoises in a poorer nutritive condition. The results of this study can be used as a baseline for assessing parasite presence in harbour porpoises and are a first step towards linking parasite infections to basic biological data gathered during necropsy

Fatal attraction: The death of a solitary-sociable bottlenose dolphin due to anthropogenic trauma in the Netherlands

The death and behaviour prior to death of a bottlenose dolphin (Tursiops truncatus) known by the name of “Zafar” created significant national and international public interest. The animal was first observed in the Netherlands on the 2nd of May 2020, closely following a boat from Brittany, France, all the way into the port of Amsterdam after passing the locks at IJmuiden. After a day of residency in the industrial port of Amsterdam, the animal was successfully lured back into the North Sea. The dolphin was observed lastly on the 5th of May following a fishing vessel heading north in coastal waters near Callantsoog. Seven days later, a dead bottlenose dolphin stranded at Wijk aan Zee and through photo-identification, the animal was identified to be Zafar. A post-mortem investigation was carried out with the aim of determining the animal’s most likely cause of death, its health status, and an attempt was made to unravel the animals approximate whereabouts prior to death through stomach content analysis. The post-mortem investigation revealed that this subadult, 14 year old male had a moderate to good body condition, no sign of significant disease, and had been feeding shortly prior to death. Injuries on the animal fit with an anthropogenic source causing mortality, and the nature and severity of the lesions were most consistent with vessel collision. Based on the sightings and stranding location and the stomach content, the animal probably died within the Dutch coastal waters of Noord-Holland. This animal was first sighted in 2017 as a solitary-sociable dolphin. Such individuals have particular home-ranges, typically interact with people and little with conspecifics. It has been reported that solitary-sociable dolphins have a higher chance of suffering from human interference, and the case of Zafar clearly demonstrates this risk

Fatal attraction: The death of a solitary-sociable bottlenose dolphin due to anthropogenic trauma in the Netherlands

The death and behaviour prior to death of a bottlenose dolphin (Tursiops truncatus) known by the name of “Zafar” created significant national and international public interest. The animal was first observed in the Netherlands on the 2nd of May 2020, closely following a boat from Brittany, France, all the way into the port of Amsterdam after passing the locks at IJmuiden. After a day of residency in the industrial port of Amsterdam, the animal was successfully lured back into the North Sea. The dolphin was observed lastly on the 5th of May following a fishing vessel heading north in coastal waters near Callantsoog. Seven days later, a dead bottlenose dolphin stranded at Wijk aan Zee and through photo-identification, the animal was identified to be Zafar. A post-mortem investigation was carried out with the aim of determining the animal’s most likely cause of death, its health status, and an attempt was made to unravel the animals approximate whereabouts prior to death through stomach content analysis. The post-mortem investigation revealed that this subadult, 14 year old male had a moderate to good body condition, no sign of significant disease, and had been feeding shortly prior to death. Injuries on the animal fit with an anthropogenic source causing mortality, and the nature and severity of the lesions were most consistent with vessel collision. Based on the sightings and stranding location and the stomach content, the animal probably died within the Dutch coastal waters of Noord-Holland. This animal was first sighted in 2017 as a solitary-sociable dolphin. Such individuals have particular home-ranges, typically interact with people and little with conspecifics. It has been reported that solitary-sociable dolphins have a higher chance of suffering from human interference, and the case of Zafar clearly demonstrates this risk