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- Ship-mediated introductions
- Shipping activities in Canadian waters
Canada has one of the longest navigable coastlines in the world, bordering the Atlantic, Arctic and Pacific Oceans, as well as the St. Lawrence Seaway as the gateway to the Laurentian Great Lakes. An exponential increase in worldwide shipping traffic and the corresponding amount of ballast water discharged by them, have resulted in an increase in alien species introductions.
An exponential increase in worldwide shipping traffic has resulted in a corresponding increase in ship-mediated introductions of alien invasive species. There are four main categories of ship-mediated introductions: ship-borne water, ship-borne sediments, fouling and bio-films. However, given the magnitude of ballast water issues, the focus remains on developing strategies to minimize the impact of ballast water discharges.
Modern commercial shipping cannot operate without ballast water, which provides balance and stability to un-laden ships. Water is pumped into the ballast tanks when the vessel is departing a port of origin and released when it takes on cargo at another port.
Over the past 30 years, there has been growing international recognition of potential problems associated with the discharge of ships' ballast water. Scientific evidence suggests that ballast water carried on board a ship, and the suspended matter in the water, can be a vector by which harmful aquatic organisms and pathogens are unintentionally transported around the world.
Technicians sampling from a ballast water sounding tube.
Processing of sampled ballast water. (Photos courtesy of the ASI Group Limited)
Hull fouling occurs when organisms attach themselves to the hulls, sea chest or internal piping of ships and are then transferred from one port to the next. Live organisms, ranging from tunicates to aquatic plants, can be found on the hulls of ships and barges moving among the different water bodies in Canada.
Hull fouling may be a more important vector of invasions in marine and estuarine waters. Currently, there are no regulatory initiatives in Canada to reduce dispersal by means of hull fouling. Factors that may increase the potential for the introduction of alien invasive species through hull fouling include oil and gas exploration that would result in increased ship traffic and the presence of oil rigs. Presumably most of the ships would be arriving in ballast.
Oil drilling rigs are another vector for alien species introduction. The rigs often remain anchored in one location for extended periods of time, becoming colonized by hull foulers as a sort of artificial reef, before being moved to the next drilling site.
While global shipping may be an important vector of long-distance dispersal, it is likely that local movement of smaller commercial fishing vessels contributes to secondary dispersal or range expansion of invaders from the point of initial introduction. There are many such vessels potentially moving between hundreds of harbours. Fishing vessels and gears (e.g., lobster traps) may be shared among several owners and be moved among different ports according to the fishing season and species for which the owners hold fishing licenses.
Recreational boating presents a similar challenge. Boats, motors, trailers, and boating equipment such as anchors and fishing gear, centreboards, rollers, and axles can transmit alien species from one body of freshwater to another. Some aquatic species can survive more than two weeks out of water, which adds to the management challenge. Select this link for tips on preventing transmission.
Terrestrial invertebrates, such as wood-boring insects, have been transported overseas in ships' cargo, including wooden pallets, cable spools, and dunnage — the logs and other rough-cut wood used to contain cargo, as well as to secure it to prevent damage during transport. Most of this type of wood is poor quality and, despite regulations to the contrary, often still has the bark attached, providing an ideal hiding place for a variety of insects and their larvae.
Numerous quarantine and potential quarantine pests have been intercepted in dunnage on ships from Asia, Europe and South America.
The brown spruce long-horned beetle (Tetropium fuscum [Fabricius]) — a wood-boring insect that attacks dead and dying trees — is an example of an invasive species, introduced into the Port of Halifax, Nova Scotia in the 1980s, most likely in dunnage from Europe or Asia. Efforts to contain an infestation of this beetle in Nova Scotia's Point Pleasant Park resulted in the destruction of over 10,000 red, white and Norway spruce.
Wooden cable spools, and other rough cut wood used to contain cargo on ships, have been known to contain various life stages of wood-boring insects.
Canadian Plant Protection officials are working with their counterparts from the United States and Mexico to take a continent-wide approach to harmonize regulations in an attempt to prevent the introduction of quarantine pests from wooden articles and packing material into North America.
Regions of Atlantic Canada that are receiving bulk carrier and tanker traffic may be at greater risk to the introduction of alien invasive species, given the large volumes of ballast water being discharged. The Bras d'Or Lakes area (Little Narrows), with its estuarine conditions, may also be more vulnerable to invasions by brackish-water taxa from United States ports.
The club tunicate Styela clava was present in Boston in the 1980s, but only recently arrived in Prince Edward Island. These species have settled on the mussel ropes where they out-compete the shellfish resulting in fewer and smaller mussels, creating economic losses for the mussel industry.
Shipping activities in Atlantic coastal waters is a good example of how ships are transferring ballast water and species between different ecosystems. The possibility of using the Gulf of St. Lawrence as an alternate zone for ballast water exchange has the potential to increase the risk of species introductions in the area.
Foreign shipping activity on the St. Lawrence River is extensive. The number of transoceanic ships bound for the three major freshwater ports on the river is four times greater than those entering the Great Lakes and the estimated volume of ballast water discharged in the ports is ten times that released into the Great Lakes.
In September 2004 a Chinese mitten crab (Eriocheir sinensis) was caught in a fishing trap on the south shore of the St. Lawrence River, opposite Quebec City.
The presence of the species represents a major concern because the St. Lawrence Estuary may provide suitable habitats and environmental conditions that could lead to established populations.
Between 1810 and 1959 there were 90 species recorded as introduced into the Great Lakes basin, and 43 in the 30-year period between 1960 and 1990. The Laurentian Great Lakes now have over 170 established aquatic alien invasive species (PDF file, 38 KB).
The sea lamprey (Petromyzon marinus), zebra mussel (Dreissena polymorpha), Eurasian ruffe (Gymnocephalus cernuus) and spiny water flea (Bythotrephes cederstroemi) have proven to be Canada's most significant invasive species challenges on the Great Lakes to date.
The Strait of Georgia on the west coast of Canada is an important for seafood production, recreational activity, and maritime industry. It has been estimated that over 117 alien invasive species have established populations in the Strait or along its shoreline. There is uncertainty about when most of the alien species arrived or their modes of introduction, however it is suspected that many arrived in ballast water, or through ship fouling.
For example some species of the dinoflagellate genus Alexandrium may have arrived with ballast water in Vancouver Harbour.
The European green crab (Carcinus maenas) was recently found in Esquimalt Harbour, near Victoria, and on the west coast of Vancouver Island. It is likely that the green crab will extend its range into the Strait of Georgia. It will become the first large intertidal predator introduced into the region and will compete with native crab species. The green crab is recognized having the potential to significantly alter any ecosystem it invades.
Ships in ballast are heading to Churchill but additional research is needed regarding the origin and nature of the ballast being carried to undertake an assessment of the potential threat of alien invasive species to the Arctic.
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