39 Questions
What is the primary cause for mass strandings of marine mammals?
Natural environmental factors
Which type of stranding is the most common and why?
Dead strandings - due to natural causes and predatory behavior
Which type of marine animals are mentioned as being prone to strandings?
Porpoises in coastal areas
How many cetacean species are recorded in the UK according to the text?
24
What are the benefits of strandings to conservationists and biologists?
Revealing threats, biology, and lives of marine mammals, and may even discover new species
Why is it a concern when strandings are not observed?
Lower numbers of animals present in the ocean
How does the UK strandings program receive funding?
Funded by DEFRA and the Welsh and Scottish governments
What is the second most prevalent type of stranding mentioned in the text?
Live strandings due to human activities
What makes the UK unique in terms of cetacean species diversity?
Wide range of potential habitats and resulting diverse species
What are some possible reasons for marine mammal strandings?
Changes in ocean currents and geological events
What is the most significant conservation concern for certain species and may be an existential threat for some populations?
PCB exposure
What is the common infectious finding in HP in the UK?
Parasitic pneumonia
What is the primary anthropogenic driver of mortality mentioned in the text?
Ship strike
Which method of sampling is described as a relatively cost-effective means of investigating cetacean threats and wider marine ecosystem health?
Strandings research
What does the text identify as a potential cause of kidney abscesses in porpoises?
Fungal infection
What international collaboration is mentioned in the text as contributing to strandings research?
IWC
What is the approximate number of systematic necropsies conducted as part of the long term strandings monitoring programme?
>18,000
What is the primary focus of the education and outreach efforts mentioned in the text?
Causes of strandings
What type of contamination is mentioned as driving disease-related mortality in cetaceans?
'PCB exposure'
What is a significant issue associated with necrotic tissue around lesion 3?
Debilitation and emaciation in affected animals
What is a common source of infection for cetaceans?
Open wounds leading to septicaemia
Which welfare and conservation issue is particularly concerning for small and enclosed cetacean populations?
Bycatch and entanglement
What is a natural driver of mortality for cetaceans involving inter/intraspecific aggression?
Attacks by bottlenose dolphins or grey seals
How can porpoises present when victims of bottlenose dolphin attacks?
Teeth marks, cavitating blubber tears, depressed regions, and spine fractures
What impact does marine pollution have on cetaceans?
Chemical, acoustic, and physical contaminants affecting cetaceans
What harmful effects can microplastics and nanoplastics have on cetaceans?
Inserting themselves into cell walls and acting as seeds for absorption of chemical contaminants
Which cetacean species are particularly at risk from infectious diseases such as HP and Brucella related meningo-encephalitis?
Harbor porpoises and common dolphins
What is a concern for cetaceans related to Polychlorinated biphenyls (PCBs)?
Bioaccumulation in the food chain
What do strandings of cetaceans inform about?
UK/EU policy and international collaborations
What is the most common cause of death for UK stranded cetaceans?
Starvation
What is the significant factor in approximately two-thirds of mass stranding events?
Manmade noise
Which marine mammal species is more vulnerable to bycatch due to demersal feeding behavior and extended time spent near fishing gear?
Harbor porpoises
What are the most common associated bycatch pathologies for common dolphins?
Wider netmarks
What is the cause of increased persistent foam in harbor porpoises killed in bycatch?
Respiratory response when drowning
What is entanglement most commonly an issue for?
Minke and other baleen whales
How do whales get caught in static gear, such as creels and pots?
Lunge feeding and becoming entangled in the vertical line
What do acute entanglement cases tend to present with?
Linear lesions without remodelling
Where are common dolphins spatially explicit according to the text?
Pelagic waters, originally in the SW region, now moving further north due to climate change.
What are unusual mortality events (UMEs)?
Unexpected strandings involving a significant die-off of a marine mammal population over a longer period of time.
Study Notes
- Stranding events occur when marine mammals, such as whales and dolphins, become stranded on shores. These events can be categorized as dead strandings, entangled/at sea, or live strandings.
- Mass stranding events refer to occurrences with more than two individuals, most of which have not been evaluated to determine causality. Manmade noise is a significant factor in approximately two-thirds of mass stranding events.
- Pilot whales are an example of a species with a higher likelihood of mass stranding events. When one individual strands, the rest often follow due to social behaviors.
- Unusual mortality events (UMEs) are unexpected strandings involving a significant die-off of a marine mammal population over a longer period of time. Examples include Cuvier’s beaked whale UME in Scotland and Ireland (2014-15) and the sperm whale UME in the North Sea (2016).
- Approximately 53% of deaths among UK stranded cetaceans are due to traumatic causes, such as ship strikes, entanglement, and interspecific aggression.
- Bycatch, or the incidental entrapment of non-target species in fishing gear, is a significant issue for marine mammals like harbor porpoises (46%) and common dolphins (17%). Harbor porpoises are more vulnerable to bycatch due to their demersal feeding behavior and extended time spent near fishing gear.
- Common dolphins and harbor porpoises have different spatial distributions in the UK. Harbor porpoises are a coastal species found around the UK coast, while common dolphins are spatially explicit in pelagic waters, originally in the SW region, and are now moving further north due to climate change.
- The most common causes of death for UK stranded cetaceans are bycatch/entanglement, infectious disease, live stranding, starvation, interspecific aggression, physical trauma, and ship strike.
- Harbor porpoises exhibit common bycatch pathologies, such as thin, linear cutaneous lesions, parallel linear lesions and notches, excised fins and/or flukes, penetrating wounds to the body wall, internal haemorrhage/trauma, evidence of recent feeding, and relatively dry airways with persistent foam.
- The causes of increased persistent foam in harbor porpoises killed in bycatch are not fully understood but are believed to be related to the animal's respiratory response when drowning and the different autonomic nervous system response when unconscious.
- Harbor porpoises are more vulnerable to passive fisheries using sink nets because they spend several weeks at the bottom feeding and are demersal feeders. The most common associated bycatch pathologies for common dolphins are wider netmarks, broken teeth/fractured jaws, post-mortem excision fins/evisceration, internal haemorrhage/trauma, evidence of recent feeding, dry airways, and good nutritional condition.
- The spatial distribution of bycatch for harbor porpoises and common dolphins varies in the UK. Cornwall accounts for 29.4% of harbor porpoise bycatch and 62.1% of common dolphin bycatch.
- To prevent bycatch of cetaceans, consider using escape nets, sonifying regions to drive them away from fishing gear, or using PINGERS around the net edge to dissuade them from the fishing gear.
- Entanglement refers to evidence of marine mammals becoming entangled in rope or discarded fishing gear/marine litter. It is most commonly an issue for minke and other baleen whales, such as those in Scotland with creel type fisheries.
- Acute entanglement cases tend to present with healthy individuals, no evidence of anoxia or water aspiration, and a linear lesion without remodelling. Chronic entanglement cases involve tissue and skin remodelling.
- Whales get caught in static gear, such as creels and pots, when they lunge feed and become entangled in the vertical line used in these fishing methods. Acute entanglement can result in death or chronic entanglement, which can cause extensive tissue damage and starvation.
Test your knowledge on the significance of bycatch and entanglement in the context of environmental welfare and conservation. Explore the impact on cetacean populations, mortality rates, and challenges in assessing the true impact on marine ecosystems.
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