The Silent Sentinels of Shetland
How Citizens Are Unlocking Harbour Porpoise Secrets
In the cold, rich waters of Shetland, a quiet revolution in marine conservation is underway, powered by the watchful eyes of local residents.
Beneath the shimmering surface of Shetland's coastal waters, a mysterious drama unfolds. The harbour porpoise, one of the UK's smallest and most elusive marine mammals, glides silently through the waves. For years, their secretive lives were largely hidden from science, with historical reports of large "mega-pods" remaining anecdotal curiosities6 . Today, a transformative force is changing that: the power of community watchfulness. Across the islands, a network of trained volunteers is piecing together the puzzle of porpoise behaviour, providing critical data to safeguard the future of these enigmatic creatures.
The Shetland Porpoise: A Closer Look at a Coastal Citizen
Harbour Porpoise Facts
- Scientific Name: Phocoena phocoena
- Length: 1.4 to 1.9 meters
- Weight: 45-70 kg
- Lifespan: Up to 20 years
- Echolocation Range: 40 Hz to 150 kHz
- Group Size in Shetland: Up to 200 individuals2
The harbour porpoise (Phocoena phocoena) is a creature of understated beauty. Often overlooked in favour of more acrobatic dolphins, these animals are perfectly adapted to their cold temperate coastal homes. They typically reach 1.4 to 1.9 meters in length—small enough to make them the shy ghosts of the cetacean world.
Their surface appearances are subtle—a gentle, rolling motion distinct from the boisterous breaching of other species. They surface with a quiet efficiency, barely disturbing the water before submerging again. This elusive nature, combined with their tendency to avoid boats, has long made them challenging subjects for study.
What harbour porpoises lack in flashiness, they make up for with sophisticated biological tools. They navigate and hunt using advanced echolocation, emitting a broad range of clicks and sounds from 40 Hz to 150 kHz—far beyond human hearing. In Shetland's waters, these remarkable animals sometimes gather in spectacular numbers, with aggregations of up to 200 individuals recorded in autumn months2 .
The Citizen Science Revolution
Community Network
Trained volunteers conduct standardized surveys from seven designated sites around Shetland2 9 .
Structured Observation
10-minute sea watching surveys with systematic scanning of predetermined ocean sections2 .
Scientific Rigor
Standardized data collection including species, numbers, behavior, and environmental conditions2 .
Recognizing the critical data gap around harbour porpoises, researchers have embraced an innovative approach: citizen science. The Shetland Porpoise Survey represents a concerted effort to understand these animals through shore-based surveys, drone filming, and acoustic monitoring9 .
Simultaneously, the Whale and Dolphin Conservation's Shorewatch program has created a network of dedicated volunteers who conduct standardized 10-minute sea watching surveys from seven designated sites around Shetland, from Unst to Sumburgh2 9 . The process is meticulously designed for scientific rigour:
Structured Observation
Volunteers survey set locations for exactly 10 minutes, systematically scanning predetermined sections of ocean2 .
Standardized Data Collection
They record species, numbers, behaviour, and environmental conditions using specialized equipment stored in locked boxes at watch sites2 .
Consistent Reporting
Crucially, volunteers report every survey—even when no animals are seen—to build a complete picture of occurrence patterns2 .
This community-gathered data has already made a significant impact. Information from Shetland volunteers contributed to the area being designated an Important Marine Mammal Area (IMMA), recognizing the global significance of these waters for marine mammals2 .
"When life is busy and there seems to always be more tasks than time allows, taking a small break to look out to sea can be very relaxing. While you might not always see a whale, it is an opportunity to feel wind and weather, to notice the changing seasons... Each survey is a small part of a larger picture, a contribution to greater understanding of the beautiful and varied lives around us."
A Scientific Toolkit for Porpoise Monitoring
The effort to understand harbour porpoises employs a diverse array of research methods, each providing a different piece of the puzzle.
Drone Observation
Aerial filming of porpoise aggregations9 .
Key Insights:
- Group structure
- Individual size estimates
- Behaviour documentation
Photo-Documentation
High-resolution photography of animals2 .
Key Insights:
- Individual identification
- Health assessment
- Population monitoring
Essential Equipment for Field Research
| Tool | Primary Function | Field Application |
|---|---|---|
| Specialized Binoculars2 | Precise visual tracking and position recording | Accurate species identification and location data |
| Underwater Acoustic Recorders4 | Capturing porpoise echolocation sounds | Detecting presence and activity when animals are submerged |
| Data Logging Sheets/App2 | Standardized recording of observations | Consistent data collection across multiple volunteers |
| Drone Technology9 | Aerial observation of groups | Documenting group size and composition without disturbance |
Mysteries of the Mega-Pods
Harbour Porpoise Group Sizes in Shetland
One of the most fascinating discoveries to emerge from citizen observations is the occurrence of large harbour porpoise aggregations, sometimes numbering up to 200 individuals2 . These "mega-pods" represent a spectacular natural phenomenon that challenges our understanding of porpoise behaviour.
The Shetland Community Acoustic Research Forum (SCARF), a new community-driven project led by the University of Cumbria, is adding another dimension to this research. By deploying small underwater acoustic recorders on salmon cages, mussel farms, and fishing creels, the project creates a detailed picture of Shetland's underwater soundscape4 .
This acoustic research helps scientists understand how porpoises use different habitats throughout the year by detecting their characteristic echolocation clicks4 . The project also demonstrates innovative collaboration by engaging marine industry workers in data collection and involving a sound artist to interpret underwater recordings, bridging science and community engagement4 .
Why Porpoises Matter: The Bigger Picture
The dedicated monitoring of harbour porpoises in Shetland extends beyond simple curiosity. These animals serve as important indicators of marine ecosystem health. As a University of Glasgow study revealed, marine mammal strandings in Scottish waters have increased exponentially—from about 100 to more than 300 annually over 30 years—suggesting potential broader environmental changes7 .
Threats to Harbour Porpoises
Harbour porpoises face multiple threats in Shetland's waters and beyond:
- Entanglement in fishing gear is recognized as a critical threat, particularly as populations recover from historical whaling pressures7 .
- Anthropogenic noise from vessels and industrial activities can disrupt their sensitive echolocation, essential for navigation and finding prey.
- Pollution, including microplastics and chemical contaminants, accumulates in their systems, as evidenced by studies on related species showing alarming contamination levels8 .
Conservation Status and Threats
| Factor | Details | Conservation Significance |
|---|---|---|
| Global Population | Estimated minimum of 700,000 individuals | Data deficiency in specific regions like Shetland |
| Canadian Status | Classified as a species of "Special Concern" | Highlights sensitivity to human activities |
| Shetland Strandings | Harbour porpoises accounted for over half of Scottish strandings (2,676 of 5,140 records)7 | Indicates potential population-level threats |
| Primary Threats | Entanglement, noise pollution, habitat degradation7 | Multiple cumulative impacts require coordinated management |
The data collected by citizen scientists directly informs conservation strategies, helping policymakers make evidence-based decisions about marine protected areas, fisheries management, and development activities in sensitive habitats2 .
Conservation Impact
The community-gathered data contributed to Shetland waters being designated an Important Marine Mammal Area (IMMA), recognizing the global significance of these waters for marine mammals2 .
A Community of Coastal Stewards
The story of harbour porpoise monitoring in Shetland is ultimately a story of connection—between people and their marine environment.
As research continues—combining traditional knowledge, scientific innovation, and community engagement—each piece of data brings us closer to understanding the secret lives of these silent sentinels of the sea. The harbour porpoises of Shetland, once overlooked, now swim at the heart of a remarkable collaboration between humans and the marine world they seek to understand and protect.
Trained Volunteers
Monitoring Sites
Protected Area Status