Aquatic invaders under high surveillance

Have you heard of the green crab, skeleton shrimp, golden star tunicate or other tunicates? No? Believe it or not, these invasive species have besieged Quebec waters completely unnoticed. Well, nearly. Since 2003, Fisheries and Oceans Canada scientists have monitored these aquatic colonizers closely and are working hard to detect the arrival of other uninvited guests in the Estuary and Gulf of St Lawrence as soon as possible.

But not all new species are invasive... "When an exotic species is found in our waters, we cannot predict the economic and ecological impact it will have. A species is designated as invasive if it causes significant damage to the marine environment or to fishing and aquaculture industries, even though no scientific criteria have been defined to characterize this phenomenon," says Nathalie Simard, Senior Habitat Biologist at Maurice Lamontagne Institute in Mont-Joli, and Invasive Species Monitoring Program Authority for the Quebec region.

Implemented by Fisheries and Oceans Canada in 2006 after the first invasive species (Codium fragile, a Japanese algae) was identified in the Magdalen Islands in 2003, this program covers Quebec's three maritime regions: the North Shore, Gaspé/Lower St. Lawrence and Magdalen Islands. Since then, six aquatic species, including the green crab, have been closely monitored (see Going further section).

Merinov, Québec Fisheries and Aquaculture Innovation Centre, is both an asset and collaborator in detecting aquatic invaders that are establishing themselves in this vast area.

Early detection, close monitoring

Vase tunicate Photo credit: Benedikte Vercaemer, DFO

Vase tunicate Photo credit: Benedikte Vercaemer, DFO

The purpose of the Aquatic Invasive Species Monitoring Program is two-fold: to detect the arrival of new intruders in the monitored area as soon as possible and to monitor how exotic species that are already established are developing. Simple, right? Not really. The area poses challenges for scientists associated with the program, and obstacles are numerous.

"Locating the invasion early on gives us the opportunity to control and eradicate an invasive species, if needed. Locally, at least. On a large scale, it's nearly impossible. Through monitoring, however, we can confirm whether the species has established itself in new infested sectors," Ms. Simard explains.

Above all else, close cooperation is required to monitor the area. Scientists in the Quebec region have regular discussions with their colleagues in other east-coast regions (Maritimes, Gulf and Newfoundland and Labrador) as part of the program. "Our monitoring and sampling methods are identical and standardized from one region to another. Given that our practices are the same, we can create distribution maps for the invader and monitor it regionally and inter-regionally," says the Maurice Lamontagne Institute biologist.

To detect the arrival of an uninvited guest in such a vast monitored area, you need to know where to look. "We target locations where species are most likely to establish themselves, where temperature and salinity conditions, among others, are favourable for the invading species," adds Nathalie Simard.

Knowing the biology of the "enemy" is essential, even though a species' ability to adapt to a new environment is sometimes unpredictable. "Such is the case for a tunicate species on the North Shore. We would have thought that the cold water in that area would prevent such a species from establishing itself," explains Ms. Simard.

In the field: between research and awareness

Locating an invasive species and monitoring how it develops in the marine environment involves implementing scientific techniques, training ocean users and informing the public. It is a delicate combination.

Nathalie Simard explains, "In the Magdalen Islands, we are in the field as of mid-June to place collectors before the breeding season. They are then retrieved in mid-August and replaced by new ones. All the collectors are recuperated in October. The analyses of these collectors indicate whether invaders are present in the sampled sites."

To complete the monitoring program, an experienced diver, who is also an expert in indigenous species around the islands, systematically inspects the area each year to search for exotic species. "Thanks to a scuba-diving campaign begun in 2008, we can determine invasive tunicate distribution on artificial structures, such as posts. After observation and analysis, we try to determine its impact on the indigenous biodiversity," explains the biologist.

The arsenal of tools available to scientists includes species-specific genetic probes that improve detection abilities and allow for faster intervention, if required. "Developed by the University of Prince Edward Island, these probes help detect the presence of invasive tunicates by extracting DNA from an unknown organism or water sample (larval tunicate)," states Nathalie Simard.

Informing marine professionals and the public is of utmost importance to the monitoring program. Together, Merinov/Fisheries and Oceans Canada are therefore devoted to providing information to stakeholders, notably fishers and aquaculturists, who are often the first to notice the arrival of new species.

Awareness campaigns to inform the public in the Gaspé Peninsula and Magdalen Islands took place. The Aquatic Invasive Species Identification Booklet is a vital tool for distinguishing similar intrusive species from indigenous ones in our waters (see link in the Going further section).

Beach seine pulled by two scientists Photo credit: Nathalie Simard, DFO

Beach seine pulled by two scientists Photo credit: Nathalie Simard, DFO

Scientific diver Photo credit: Isabelle Bérubé, DFO

Scientific diver Photo credit: Isabelle Bérubé, DFO

Channels of invasion

Green crab Photo credit: Claude Nozères

Green crab Photo credit: Claude Nozères

How did these species manage to invade our waters? The ways they are brought in vary: ballast water, pleasure or commercial ship hulls or even aquaculture transfer from one region to another.

According to the biologist, "currents, ballast water or aquaculture transfers are all valid hypotheses to explain the introduction of the green crab in the Magdalen Islands."

From an ecological and economic perspective, scientists are closely monitoring this colonizer, which is a high-level predator of shellfish. Although it is currently confined to lagoons, the risk that it may spread to lobster nurseries worries marine professionals. "Remember that the lobster industry represents 80% of fishing revenues in that maritime sector. The impact of such a predator on a lobster population is unknown at this time," says Ms. Simard.

According to the biologist, working on the vehicles of dissemination is essential: eradication is very costly and yields little results if the species is already well-established. This is an exciting challenge for a scientist like Nathalie Simard.

She also works as part of two groups within the International Council for the Exploration of the Sea: one deals with ballast waters and navigation-related vehicles of dissemination, and the other with species introduction and transfer. This is one way that Fisheries and Oceans Canada's voice is heard in the high-priority invader species case (monitoring and research).

Another one of the program's challenges is using available resources to cover the immense area. But that is nowhere near enough to stifle Ms. Simard and her colleagues' determination. Data from the monitoring program is used to formulate better informed scientific opinions on authorization requests for aquaculture transfer. A source of pride? Perhaps. For now, this scientist is sticking to the facts.

Going further

Aquatic invasive species.

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