Round Goby, Tench, Snakehead and Rudd

Table of contents:

• Aquatic invaders
• Pathways of invasion
• Threats to the environment, the economy and society
• Focus on an invader
• What you can do

• What to do if you find aquatic invasive species?

Round Goby

(Neogobius melanostomus)

Characteristics

• between 6 cm and 16 cm, up to 25 cm
• bulging and prominent eyes
• pelvic fins welded in the shape of a suction disk
• noticeable black spot on the first dorsal fin
• brown, olive green, or slate grey, with dark brown spots

Origin

The Round Goby is a fish native to the seas of central Europe and Asia. Disseminated by ballast waters from ocean-going vessels, it was first seen in North America in 1990 in the St. Clair River, Ontario. It quickly spread to the Great Lakes and the St. Lawrence River. Captured near Québec City in 1997, it was found in the St. Lawrence Estuary, near Rivière-Ouelle in 2009.

Habitat

The Round Goby is a bottom-dwelling fish that lives mainly in rivers and lakes but can also be found in brackish waters. It generally lives near shores, particularly in rocky bottoms which offer shelter, but it can also be found on sandy bottoms.

Similar species

The Round Goby resembles several other fish found in Canadian waters, including the Deepwater Sculpin (Myoxocephalus thompsonii), a native species at risk. However, unlike the Round Goby, sculpins have a smooth skin (no scale), no black spot on their first dorsal fin, and have 2 distinct pelvic fins. The Round Goby also looks like the Western Tubenose Goby (Proteorhinus semilunaris), another invasive species which can be found in Ontario and Quebec. It can be distinguished from the Round Goby by the lack of a black spot on its first dorsal fin and by its tube-shaped nostrils.

Western Tubenose Goby

Tench

(Tinca tinca)

Characteristics

• average of 20 cm to 40 cm, up to 70 cm
• body covered with small scales embedded in slimy skin
• single, short barbel on each side of the mouth
• rounded, dark coloured fins without spines
• back is olive green or black, with golden sides and a white or yellowish belly

Origin

The Tench is a fish native to Europe and Asia. In Quebec, the Tench was illegally imported from Germany in 1986 to a fish farm near the Richelieu River. Some of them escaped from the breeding ponds in the fish farm in 1991 during a heavy flood. It was then found in Lake Champlain in 2001, and in the St. Lawrence River in 2005. The Tench is also present near the Ontario-Quebec border, between Cornwall and Lake Ontario. As of spring 2021, the Tench is also located in the Ottawa River.

Habitat

The Tench can live in a variety of aquatic environments, including areas with low levels of oxygen and still waters. It often lives in areas where the bottom is muddy and covered with aquatic vegetation and therefore is found in marshes, ponds, lakes, and rivers where the current is weak. This tolerance to these kinds of conditions allows it to colonize places that are too hostile for most other species.

Similar species

The Tench is similar to the Brown Bullhead (Ameiurus nebulosus). The difference between them is that the Brown Bullhead has no scale and four pairs of barbels rather than a single barbel on the Tench. The Common Carp (Cyprinus carpio) also looks very similar to the Tench, except it has larger scales, 2 pairs of barbels and a very long dorsal fin (2/3 of the back) preceded by a single spine.

Common Carp

Brown Bullhead

Snakehead

(Channa sp., Parachanna sp.)

Characteristics

• between 17 cm and 180 cm, depending on the species
• elongated and cylindrical body
• very long dorsal and anal fins, round caudal fin, pelvic fin near the head
• small head covered with large scales
• large mouth with many sharp teeth
• colour ranges in different shades of brown with camouflage patterns

Origin

There are 29 different species of snakeheads, and the vast majority of them are native to southern and eastern Asia. None of these species are present in Canada. The species that is most likely to adapt to Canadian waters is the Northern Snakehead (Channa argus), due to its ability to thrive in colder temperatures. Their 2 most likely pathways of propagation are food markets and the aquarium trade.

Habitat

Snakeheads are found in shallow bodies of water (ponds and marshes) with weak currents, low oxygen levels, and muddy bottoms covered with aquatic vegetation. Most species can withstand temperatures ranging from 0°C to 30°C.

Similar species

The Northern Snakehead can be confused with 2 native fish: the Bowfin (Amia calva) and the Burbot (Lota lota), also known as the Eelpout. The Bowfin does not have scales on its large head, but it has 2 outer nostrils shaped like small tubes, and a short anal fin. The Burbot has an elongated body, scales that are nearly undetectable, 2 dorsal fins (one short and one long), and a barbel under the jaw.

Bowfin

Burbot

Rudd

(Scardinius erythrophthalmus)

Characteristics

• between 15 cm and 25 cm, up to 50 cm
• small upturned mouth
• red brown to bright red fins
• golden-greenish back, golden-yellow sides and whitish belly completely covered with scales

Origin

The Rudd, also known as Pearl Roach or Redeye, is native to the seas in central Europe. It was first observed in the United States in the late 1880s, and is believed to have been accidentally disseminated in North America through live bait and aquaculture. In Canada, it was first observed in 1990 in the St. Lawrence River in Ontario. In the following years, it was reported in Lakes Saint-Pierre, Champlain, Ontario, Erie, and Michigan.

Habitat

The Rudd lives in calm waters with bottoms covered with thick aquatic vegetation such as ponds, lakes, and rivers. It is able to adapt to various environmental conditions by changing its diet according to available resources. Since it only tolerates temperatures between 10°C and 22°C, the cold temperatures of our winters are probably a limiting factor for its establishment in our waters.

Similar species

The Rudd closely resembles the Golden Shiner (Notemigonus crysoleucas) at first glance. However, the Golden Shiner is much smaller (between 8 cm and 12 cm, sometimes up to 23 cm). It has no scales on its belly and its fins are usually greenish yellow, possibly turning bright orange during breeding season (May to August). The possible hybridization between these 2 species worries biologists.

Golden Shiner