Sarah Stewart-Clark, a researcher at Charlottetown's Atlantic Veterinary College, works on a tunicate in her lab. (Maggie Brown/CBC)

Maritime fishermen will soon be able to test harbours and bays for the presence of tunicate at an early stage, helping them battle an invasive species and major pest for the mussel industry.

Invasive tunicates are slimy creatures that attach themselves to mussels and either rob the shellfish of nutrients, or literally rip the mussels off the socks with their sheer weight.

Sarah Stewart-Clark, a researcher at Charlottetown's Atlantic Veterinary College, has developed a test that detects the tunicates' DNA as early as the egg stage, when their presence is still invisible to the naked eye.

"Historically invasions have been discovered when populations have reached such a high level, that an aquaculture grower or a member of the general public or scientist or government employee can visually see this huge fouling species," said Stewart-Clark.

"By then the population is so large it's very difficult to control and mitigate."

Tunicate, pictured here surrounding a sea anemone, can completely cover a mussel sock, robbing the shellfish of nutrients and making processing difficult and expensive. (CBC)

Jarrod Gunn-McQuillan, executive director of the P.E.I. Aquaculture Alliance, said knowing exactly which of the four species of tunicates currently in the Maritimes are in a body of water can help with important decisions, such as when to restrict the movement of mussels between bays that have a particular species of tunicate and those that don't.

"It's a benefit for industry in that we can have that confirmation," said Gunn-McQuillan.

"We can try and see if there's an opportunity to mitigate or try and slow down the spread of that species in the area."

Stewart-Clark said the test will also help identify new species of tunicate that might be on its way to the region from other parts of the world.

"We're hoping to develop tests to identify those invasive species so that we can detect them at the earliest stage of the invasion, instead of waiting to find them when they're a huge population," she said.

Catching the invasion early may give those battling the pests a chance to prevent them from getting a foothold in Maritime waters.