Harmful Exotic Species

Ontario 's fish and the waters that support them are threatened by several exotic species that can be spread unknowingly by anglers and boaters. Some harmful exotic species that have been discovered in Ontario waters and ways of preventing their spread are described below. Whenever you move your boat from one waterbody to another, exotic species may tag along for the ride. There are some important things you can do to prevent the transport of harmful exotic species from one lake or river to another:

Zebra Mussels

Zebra mussels are freshwater mollusks that often attach in large numbers to hard objects in the water. They are normally brown in colour, with yellow or white stripes, and are very small - about the size of a fingernail. In the Great Lakes , zebra mussel colonies have clogged municipal and industrial water intake lines, covered boat hulls, fouled beaches, killed native clams, and disrupted the lake ecosystems.

Zebra mussels have spread rapidly in Ontario . Since their initial discovery in 1988 in Lake St. Clair , they have spread throughout the Great Lakes/St. Lawrence River system, and into some inland lakes. Zebra mussels have invaded the Trent-Severn and Rideau systems, and have been found in some Muskoka Lakes . They probably entered these inland systems through recreational boating traffic. Zebra mussels are invisible to the naked eye in their early life stage (called a veliger), when they can be transferred unknowingly in live wells, bilge water and baitfish buckets. In their adult stage they can attach to boat hulls.

Help slow the spread of zebra mussels by thoroughly cleaning your boat and angling gear before moving between bodies of water.

Ruffe

The ruffe is a small European relative of the walleye and yellow perch. It was introduced into the Duluth-Superior Harbour of Lake Superior from the ballast water of ocean-going ships in the early 1980s. Within a few years it became the most abundant fish in the harbour. Ruffe are established in the Kaministiquia River in Thunder Bay , Ontario . Ruffe may displace native Ontario fish species through competition for food and habitat. Help slow the spread of ruffe. Do not collect baitfish from the Great Lakes for use in inland waters. Learn how to identify ruffe. If you think you have caught one, kill it and contact your local MNR office.

It is illegal to possess ruffe except when transporting a dead specimen to a Ministry of Natural Resources office

Round Goby

The round goby is a small, bottom-dwelling fish from eastern Europe that was introduced to the St. Clair River via ballast water in the late 1980s. It is now found in all of the Great Lakes except Lake Ontario . The round goby is an aggressive fish that can spawn several times per year, grow up to 25 cm (9.8 in.) in length, and compete with native bottom-dwelling fish species. Round gobies are expected to be harmful to Great Lakes and inland fisheries.

Although gobies are not legal baitfish, they look very similar to our native sculpins which can be used as bait.

Donna Francis, Univ. of Michigan

Do not collect baitfish from the Great Lakes for use in inland waters.

Smelt

Smelt is a species of small fish that reproduces and grows rapidly. Releasing smelt eggs or spawn into waters other than those they came from can upset the delicate ecological balance in many water-bodies. The smelt take a large portion of the food supply, posing a serious threat to other fish species and populations.

MNR asks smelt fishers in Ontario to take care when rinsing dressing equipment or dumping entrails. Dumping fish waste into lakes and streams may put fertilized smelt eggs into the water system. This is against fishery laws, which prohibit the transfer of live fish or spawn from one body of water to another. It can create great problems for both commercial and recreational fisheries. For the sake of Ontario 's fish populations, do not transfer smelt, and pass the word along to other fishers.

Live smelt may not be used for bait. It is also illegal to possess live or dead smelt while recreational fishing in Divs. 22, 22A, 24, 30, 31 and 32 in northwestern Ontario

Crayfish

The rusty crayfish, originating from the midwestern United States , was probably introduced into Ontario through bait-bucket transfers. This crayfish is now found in Lake Superior and in several lakes in northwestern and central Ontario . The rusty crayfish replaces native crayfish species, can consume large amounts of aquatic vegetation, and could affect fish habitat.

If you are using crayfish for bait, do not release them into a lake or river.

Bell Museum , Univ. of Minnesota

It is illegal to release crayfish, and other baitfish, except into the body of water from which they were taken.

Grass Carp

What are they?

Grass carp is one of the largest members of the family Cyprinidae, the carps and minnows family. It is one of several species in a group of fishes known as Asian carp. Also known as White Amur, the grass carp (Ctenopharyngodon idella) is native to Eastern Asia .

This species can survive a range of habitat conditions and tolerate water temperatures ranging from 0 to 33ºC. Adult grass carp generally prefer densely vegetated inshore areas of rivers and lakes.

In their native range, grass carp can live up to 15 years or more, weigh up to 50 kg, and grow over one metre in length. Grass carp reach sexual maturity at a young age and exhibit high rates of reproduction. Their scales are a silver/pale grey colour with a prominently dark-edge, giving a unique characteristic cross-hatched effect.

Photo courtesy of Toronto and Region Conservation Authority

Where Are They?

The species was imported to North America in the 1960s for research on control of aquatic vegetation. The first release into open waters occurred accidentally when fish escaped the research ponds. The first intentional release of the species was in Arkansas in 1971. The species is widespread in the United States , occurring in 45 states through accidental and intentional release.

Grass carp was introduced to Alberta in 1987 for research on the control of aquatic vegetation in irrigation canals. Since that time they have escaped to the wild.

In Ontario , a grass carp was captured in 1985 in Lake Erie . Three more were captured in commercial fishing nets on separate occasions during 1989 and 1998 in southern Lake Huron . In the fall of 2003, a single grass carp was caught at the mouth of the Don River, Lake Ontario . It is believed that each capture was an isolated occurrence and there is no established population of grass carp in the Great Lakes .

What Are The Impacts of Introduced Grass Carp?

Where they have become established in the U.S. , grass carp have had a negative effect on the ecosystem, as well as on the commercial and recreational fishery. Grass carp feed extensively on aquatic vegetation, often uprooting large areas of vegetation leading to increased turbidity and poorer water quality. Impacts to wetland habitat and species have also been documented.

Many U.S. states and Alberta require grass carp eggs to undergo treatment that results in the production of fish that are unable to reproduce. These fish are referred to as sterile or triploid. Despite this precaution, breeding populations of grass carp do exist in the U.S.

Live grass carp can be purchased from fish markets, supermarkets and restaurants in large urban centres. It may be possible to obtain live grass carp through the aquarium and water garden trade and over the Internet.

You Can Help!

Please take the following precautions to help prevent the spread of grass carp and other exotic species.

      Never release live fish purchased at a market, restaurant or from an aquarium into a lake, river, pond or stream. It is illegal and harmful to aquatic ecosystems.

Spiny Water Flea ("BC")

The spiny water flea is a small (less than 1 cm long) planktonic crustacean that was introduced into the Great Lakes from Europe in the early 1980s. It has spread throughout the Great Lakes, and has invaded the Muskoka Lakes , Lake Simcoe, the Kawartha Lakes, Lake Temagami , and several smaller lakes in central Ontario . The spiny water flea was probably introduced into these inland lakes through recreational boating traffic. The impacts of this invader are unknown, but it might impact fish by disrupting the food chain. Spiny water fleas collect on fishing lines and downrigger cables, and can be transported in bait-buckets and live wells. It only takes one adult or egg to begin an infestation.

Bell Museum , Univ. of Minnesota

Please ensure that you thoroughly clean your fishing equipment and boat if you have been in an infested waterbody.

Aquatic Vegetation

There are several species of exotic aquatic plants found in Ontario which can cause ecological problems if spread into new waterbodies. Eurasian water-milfoil, purple loosestrife, European frog-bit, and flowering rush are just a few examples of these types of plants. They can displace native vegetation, affect fish and wildlife habitat, and interfere with human uses of our waterways. Aquatic plants can also harbour zebra mussels and other species.

Bell Museum , Univ. of Minnesota

When leaving any waterbody please remove all vegetation from your boat, trailer and other equipment.

Extensive Fish Kills

A number of causes, natural or unnatural, may lead to large numbers of fish dying. Most fish kills happen in the summer, but winter fish kills are not uncommon. Fish may die from natural changes in water quality caused by temperature changes, lack of oxygen (from decomposition), algae toxins, high turbidity ("murky" water) or too much gas trapped in water. Other natural causes include epidemics (of bacteria, viruses or parasites) or spawning problems. Unnatural fish kills are usually the result of releasing heated waste or toxic chemicals. The sources may be industrial, agricultural, municipal, or residential. Pesticides used for farming and to control water weeds are another cause. Some kills result from tampering with water levels or flow. The Ministry of Environment and Energy and the Ministry of Natural Resources investigate fish kills to find their causes, suggest responses, set up preventive programs and collect evidence for possible court action. Speed is of vital importance in these investigations. Since fish decompose rapidly, especially in warm weather, evidence may be lost within hours.

It is important, therefore, to report any fish kills immediately.

In river systems, toxins and fish carcasses may travel downstream from where the kill occurred. If you see evidence of a fish kill, contact the nearest office of the Ministry of Environment and Energy or the Ministry of Natural Resources right away.

Aquarium Fish

Many people release unwanted aquarium pets into natural waters. Not only is this activity illegal, it can harm the environment. Several exotic species of plants and animals have been introduced to the Great Lakes region by this practice. If you have an unwanted aquarium pet, return it to a local pet store, or donate to a school or other institution - it will be better for your pet and the environment.

Moving Live Fish

Many new populations of bass and other fish species have been established in Ontario through unauthorized stocking. These introductions are often conducted by individuals with good intentions of creating new recreational fisheries. However, this practice is illegal and can cause great harm to existing recreational, commercial and bait fisheries. The negative impacts of these stocking activities often become widespread as the introduced species spreads to other lakes through connected waterways.