At low tide on Scotland’s west coast, Sgiath paddles along the shoreline and searches boat hulls, fishing gear and ropes. Her target is a small fragment of Didemnum vexillum, an invasive marine organism known as “sea vomit” that can be difficult and costly to manage once established.
Marine ecologist Dr Texa Sim developed the idea while working on a native oyster restoration project. Identifying D. vexillum commonly involves specialist laboratory analysis and DNA testing, and Sim wanted to determine whether a trained dog could provide a rapid, practical way to screen coastal sites.
The project began with no assurance that scent detection would translate to a marine environment. When I first started this project, I genuinely didn’t know whether it would work, Sim said.
Sgiath, a black Labrador, became what is believed to be the first dog trained to detect D. vexillum. Sim reported that the dog selected the target immediately when first asked to distinguish it from numerous similar scents. Sgiath has since detected the organism when concealed among other marine life and located small fragments attached to coastal equipment.
Her indication is deliberately restrained: a stillness, seated stare or frozen stare rather than the more conspicuous behavior used in her mountain-rescue work. That distinction matters for a detection dog operating around sensitive samples and crowded marine growth. Training must produce not merely interest in a general marine odor, but a consistent response to one target among closely related or co-occurring organisms.
From proof of concept to monitoring tool
Uisge, a three-year-old Labrador originally intended for ecology detection work, later joined the project. The two dogs have distinguished D. vexillum from other sea squirts and marine organisms, and they have identified traces of its scent in water samples. Those results establish a promising proof of concept, but they do not yet supply standardized measures of canine sensitivity, specificity or error rates under varying field conditions.
That distinction separates a successful trained behavior from a validated monitoring system. Operational trials would need to establish how reliably dogs perform across different sites, target concentrations, tides and mixtures of marine material. Standardized protocols would also be necessary before results could be compared across surveys or used confidently in regulatory work.
Sgiath and Sim were scheduled to be recognized at IFAW’s Animal Action Awards at BAFTA London on Thursday, October 15. IFAW Director of Marine Conservation Sharon Livermore called the work a trailblazing contribution to conservation science.
The ecological stakes are substantial. D. vexillum can spread across harbours, oyster farms and other marine infrastructure, smother native wildlife and cause losses for aquaculture. An official Scottish environmental-DNA study identifies established presence in parts of the Firth of Clyde, Loch Creran and Loch Fyne. It also found the organism’s DNA at Dunstaffnage Marina before colonies were later confirmed there during an assessment of marina pontoons.
Dogs and DNA answer different questions
Environmental DNA, or eDNA, detects genetic material shed into water or sediment. A peer-reviewed Scottish study validated a species-specific test for D. vexillum and found no amplification among 21 non-target tunicate species tested. Its results agreed completely with historical presence-or-absence records at the sampled Scottish sites.
Yet eDNA also illustrates why no surveillance method should be treated as infallible. Detection became less consistent where the organism was scarce or under management, creating a risk of false negatives. The researchers recommended using eDNA to direct traditional surveys rather than replace them, with unexpected detections confirmed through visual examination and DNA sequencing.
A dog could occupy a similarly complementary role. Sgiath can search equipment and shoreline material directly, while the dogs’ work with water samples suggests another possible screening route. Laboratory testing, however, provides measurable detection limits and a pathway for confirming identity. The canine approach still needs comparable validation before scientists can define where it is reliable and how a dog’s indication should trigger follow-up work.
Warmer waters may assist the organism’s expansion, adding urgency to surveillance around vulnerable wildlife, marinas and aquaculture sites. Sgiath’s work does not replace laboratory diagnostics, but it demonstrates that a trained nose may help marine ecologists decide where to look sooner before a small, concealed fragment becomes a widespread colony.
What’s your dog’s job, official or self-appointed? Tell us in the comments.
By Tom Whitaker — Outdoor magazine editor who has reported on search-and-rescue, herding, field dogs, and working-dog handlers.
