Anne Murray: The alien species invasion
Asian carp invading the Great Lakes, lethal reptiles lurking in B.C., a snakehead fish on the loose in Burnaby: recent headlines have been pretty sensational when it comes to wildlife. Yet it is the less spectacular animal escapees that have the largest impact on our local habitats. Non-indigenous molluscs, fish, frogs, turtles, rabbits, and squirrels have all been released into the environment. Despite the problems caused by such animals, public and government responses have been patchy. People need to be more aware of the cost to our local wildlife of these strangers in our midst, if we are to retain any semblance of specialized West Coast habitats for the future.
While some animals escape by accident, many more have been deliberately released into the wild, whether for commercial interest, sport, or to get rid of an unwanted pet. Problems with aquatic animals arise because the Lower Mainland is a vast, inter-connected wetland, so fish, frogs, and turtles can move very easily throughout the whole area. American bullfrogs were introduced to B.C. as live food items and then escaped. They are much larger than native frogs, which they out-compete. They will even eat ducklings. Non-native fish are regularly and illegally introduced into B.C. waters. For example, largemouth bass and crappie deliberately released into lakes for sport fishing opportunities made their way to more remote watersheds, home to endangered and specialized native species. Pacific oysters were introduced into Boundary Bay by commercial growers in the early 1900s. They soon proliferated and out-competed the native oyster. In the course of industry operations, a host of oyster pests and other non-indigenous shellfish were also introduced. The combined effect that these snails, clams, and oysters have had on the ecology of the mudflats and migratory birds has never been studied. In more recent times, other shellfish have arrived in ballast water or on the hulls of ships, and non-native fish and shellfish are regularly grown in aquaculture operations along the coast.
Bought on a whim, many animals that start out as small pets, such as turtles, fish, snakes, rabbits, and even cats, end up relocated to “the wild” as owners get bored of looking after them. Lower Mainland parks and green spaces are not really wild, so they lack predators. Tolerant of local climate conditions, introduced animals may survive and breed, becoming invasive species. They then start spreading further afield. Eastern grey squirrels originally released in Stanley Park eventually made the transition to the suburbs and within a few years had covered the Lower Mainland. Feral cats suffer from poor health; if they survive, they will kill many native birds and small mammals.
Baby red-eared sliders look like a reasonable pet, as they are small and cheap. However, the average life span of a turtle is 20 to 30 years, during which time they need care, food, and housing. Some owners get bored or are unable to look after their pet. Unfortunately, instead of returning the turtle to a pet store, they release it into the nearest pond. This is a very bad idea. Red-eared sliders consume ducklings, insects, larvae, and tadpoles that are part of the ecological food chain. Surrey has banned their sale, due to concerns around salmonella poisoning, but in places like False Creek, people actively feed them which allows them to breed.
Introduced fish are a huge issue for the Lower Mainland and one that provokes quite divided opinions. There seems to be a curiously laissez faire attitude among regulators to largemouth bass, a species that is hugely popular with sport fishers, while the discovery of one snakehead fish in Burnaby Lake created an uproar. Largemouth bass, crappie, goldfish, pumpkinseeds, bluegills, and other sunfish, are all introduced species that are now found in rivers, tributaries, and lakes from the mouth of the Fraser to Chilliwack. While some spread is the natural consequence of wetland connections, they are also notoriously and illegally helped along by a few anglers (the so-called “bucket brigade”). Largemouth bass are carnivorous and, despite beliefs to the contrary, are known to consume salmonids. Crowded together in lakes, where many anglers gather, bass subsist on insects, which maybe gives rise to the misconception.
Over the years, the composition of fish in the lower Fraser valley has changed enormously. There must be an impact on native fish, but it has not been comprehensively assessed. Other than recognizing that fish farms can introduce diseases, the Cohen Commission inquiry did not look at other introduced fish as a factor in the decline of salmon stocks, although so many compete for food in the same areas as young salmonid fry are rearing.
Snakehead fish are valued by Asian owners who grow them to large, valuable specimens. They are also one of many Eurasian fish that are sold in Asian food stores, often as live fish for customers and restaurants. A snakehead that had been released or escaped was spotted at Burnaby Park in 2012 and DFO staff drained the lake to capture it. It took 300 hours of staff time and attracted a lot of media attention, particularly as the fish looked so ferocious. It was originally believed to be a northern snakehead, a species that would have had a good chance of surviving a B.C. winter, but subsequent study determined it to be likely a blotched snakehead.
As a result of the snakehead scare, the provincial Wildlife Act’s Controlled Alien Species Regulation was amended to prevent the possession, release or escape of “aquatic invasives”. This included any species of the snakehead, carp, goby, and bullhead families, or of any mussels. This added to the original regulation of 2009 that made it illegal for individual owners to acquire any listed alien animal that constitutes a threat to human health or safety, or to the environment, including tigers, alligators, boa constrictors, and about 1,200 other exotic animals.
Vigilance is a good deterrent to illegality, but there is probably little funding for enforcement. Many more proactive inspections are required, at live fish markets and retailers, points of entry, and in pet stores. One pet store employee I spoke with said he had only seen one Ministry of Environment inspector and never anyone from DFO, and he felt there was a need to be much more visible in enforcing the regulations.
Fewer red-eared sliders turtles are being sold but other rarer species are sought after by collectors. It is illegal to bring Fly River turtles from Indonesia and Papua New Guinea, where wild populations are declining drastically. Yet every one of these turtles in Canada must have been smuggled in, either as an egg or a hatchling. According to B.C. Aquaria there are no licensed breeders and they do not breed well in captivity. Customs officials are probably not trained on turtle identification, and may not know much about the pet industry.
Non-native turtles and bullfrogs out-eating native critters, once wild rivers full of alien fish, and hordes of pet rabbits running around parks: the problem of introduced animals is huge. It seems almost impossible to stem the tide and move back in time. Only much greater education, awareness-building, and a comprehensive approach across all levels of society could have any effect on curbing the numbers. Unfortunately, many people do not understand why releasing fish or pets is detrimental and continue to do it.
Western painted turtles are at the northern limit of their range in B.C., and the only native pond turtle still living in the Lower Mainland. Much of their habitat is occupied by red-eared sliders and to the non-discerning eye they look very similar. Life is tough for native animals where urbanization has changed so much of the natural habitat. Competition with introduced species is yet one more challenge for them. Yet a small population of painted turtles was living in Burnaby, quietly hibernating in the lake mud through the winter. Then a coal train spilled its load on a nearby rail line. A rain storm washed piles of coal into the lake and turtle habitat was smothered. Divers were at the scene this week, assessing the damage. Life is perilous when you are on the brink of survival.