A mountain-rescue labrador has found hundreds of invasive sea squirt colonies at low tide

Dr Texa Sim, the marine ecologist who works with Sgiath, says the dog is always right when she points out a sea squirt ^[15]. The claim is about false alarms: when the dog freezes, there is a colony. A biosecurity survey depends on the opposite figure. The report does not count how many colonies she walked past, or say how a person searching the same stretch of shore would have fared.

The colonies are hard for people to see. The species looks like slime among seaweed and on structures such as pontoons and oyster cages ^[3], and it comes in shades from orange to cream ^[8]. At low tide Sgiath can, in Dr Sim's words, "dive down under the seaweed" ^[12]. "She just does a survey with her nose, essentially, she can pinpoint exactly where it is, so it's much easier," Dr Sim said ^[18]. Searching under the weed by scent is a real capability, and it is the part of the report we find most convincing.

It is also a beach result. The report puts Sgiath and Dr Sim on beaches ^[6], and names pontoons and oyster cages only as places the animal hides ^[3]. Dr Martyn Kurr, a marine biologist at Bangor University, told BBC News that biofouling species clog aquaculture pens, marine infrastructure, and machinery such as boat propellers ^[10]. A beach survey covers part of that damage.

Dr Sim is candid about the stage the work is at. "When I first started this project, I genuinely didn't know whether it would work," she said ^[16]. She describes it as a proof-of-concept project that "has exceeded every expectation I had" ^[17]. We think the label is right. The next step is a controlled comparison: the dog's finds checked against a visual survey of the same shore, with misses counted.

Scale is the second limit. Getting Sgiath proficient at both mountain rescue and marine conservation took hard work and long hours from dog and owner ^[13]. She was trained as a mountain rescue dog first, then taught the scent of the carpet sea squirt ^[5]. Every additional team would repeat that training.

Dr Kurr went further than the project itself. He said scientists were just starting to realise that dogs "can smell changes in water that signal a marine invasion which otherwise might have gone unnoticed" ^[19]. Sgiath's task, as described, is recognising the scent of the animal on the beach [c9, c10]. Smelling the colony exposed at low tide and smelling a signal in water are different jobs.

The budget line is large. Control and clean-up of marine invaders cost millions of pounds every year across Europe ^[11]. The species reproduces quickly in warmer months, and with warming seas there are fears it could spread further ^[9].