Round goby
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| Apollonia melanostomus (Pallas, 1814) |
The round goby, Apollonia melanostomus, is a freshwater bottom-dwelling goby of the family Gobiidae, native to central Eurasia including the Black Sea and the Caspian Sea.
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[edit] Characteristics
While young, its coloring is grey with a distinctive black spot on the front dorsal fin. Upon maturation the coloring becomes spotted with gray, black, brown, and olive green markings. The eyes protrude slightly from the top of the head and it has a suction disk on its pelvic fins. It is typically 4 to 10 inches in length with a maximum of 9.7 inches (24.6 cm).
[edit] Feeding
It usually feeds nocturnally (but has been observed to feed diurnally as well) and is believed to detect prey only while stationary. Its primary diet includes mollusks, crustaceans, worms, fish eggs, small fish, and insect larvae. Opportunistic feeding behavior contributes to its threat as an invasive species.
[edit] Reproduction
Females spawn up to six times during the spawning season which spans April to September. The males guard nest eggs and newly hatched young, resulting in hatch rates of up to 95%. Its eggs are 4 mm by 2.2 mm in size. Female round gobies reach maturity in 1 to 2 years while males do so in 3 to 4 years. Gobies in the Laurentian Great Lakes typically mature up to 1 year earlier than in their native habitat.
[edit] Invasive species
The species was accidentally introduced into the North American Great Lakes by way of the ballast water of cargo ships. First discovered in the St. Clair River in 1990, the round goby is considered an invasive species with significant ecological and economic impact.
An aggressive fish, the round goby feeds on competitor fish such as the sculpin and longperch, substantially reducing their population size. It also consumes other aquatic resources such as snails and mussels, thereby reducing the availability of food for native species. In areas where the round goby has become established, the populations of native aquatic life has declined. Its robust ability to survive in degraded environmental conditions has increased its competitive advantage compared to native species. Heavy feeding on invasive mussels (zebra and quagga) may result in greater bioaccumulation of toxins higher in the food chain (i.e. game fish such as smallmouth bass).
An unintended benefit of the introduction is that the Lake Erie Watersnake, an endangered species, has found the round goby to be a tasty addition to its diet. A recent study found the round goby now accounts for up to 90% of the snake's diet. The new food supply means that the water snake is now staging a comeback. [1]
The round goby is also considered invasive in parts of Europe including the Gulf of Gdansk.
[edit] References
- The Round Goby, Neogobius melanostromus, a Fish Invader on both sides of the Atlantic Ocean (2004) in Biological Invasions, Springer Science+Business Media B.V., Volume 6, Number 2, 173-181.
