Round goby
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| Neogobius melanostomus (Pallas, 1814) |
The round goby, Neogobius 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
Round gobies are small, soft-bodied fish, characterized by a distinctive black spot on the first dorsal fin. Their eyes are large and protrude slightly from the top of the head and, like most gobiids, round gobies have pelvic fins which are fused into a single pelvic suction disc on the belly of the fish. Round gobies range in length from 4 to 10 inches (maximum of 9.7 inches (24.6 cm), and in weight from .176 ounces to 2.816 ounces, increasing as they age. Male round gobies are larger than females. Juvenile round gobies (less than one year old) are grey. Upon maturation, round gobies become mottled with gray, black, brown, and olive green markings. Adult male round gobies turn inky black during the spawning season and develop swollen cheeks. Male and female round gobies are easily differentiated through the shape of their urogenital papilla, which is white to grey, long and pointed in males, and brown, short and blunt-tipped in females.
[edit] Feeding/Habitat
Round gobies are benthic (bottom-dwelling) fish, and lack swimbladders. They usually feed nocturnally (but have been observed to feed diurnally as well, and are believed to detect prey only while stationary. The primary diet of round gobies includes mollusks, crustaceans, worms, fish eggs, small fish, and insect larvae. Round gobies are native to the Ponto-Caspian region of Europe, but are now considered an invasive species in the North American Great Lakes (where the first round goby was detected, in the St. Clair River, in 1990) and newly colonized regions of Europe such as the Gulf of Gdansk.
Round gobies are euryhaline (salt-tolerant) and are found in both freshwater and marine ecosystems.
[edit] Reproduction
Round gobies exhibit male parental care. Females can spawn up to six times during the spawning season, which spans April to September. Males will migrate from the deeper water, where overwintering occurs, into shallower breeding grounds during the beginning of the mating season. The males are territoral and will guard nests of eggs and newly hatched young, resulting in successful hatch rates of up to 95%. Its eggs are 4 mm by 2.2 mm in size. Female round gobies reach sexual 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 in Europe. The male releases a steroid sex pheromone that attracts females to their territory. The male may also use visual displays, such as changing color and its posture, along with sounds, during courtship. The females deposit their eggs in male-guarded crevices between rocks. Egg clutches can contain up to 5,000 eggs. Males defend these eggs from predators, and continuously fan them to provide the developing embryos with oxygenated water.
[edit] Invasive species
The species was accidentally introduced into the North American Great Lakes by way of ballast water transfer in cargo ships. First discovered in North America 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 outcompetes native species such as the sculpin and logperch for food (such as snails and mussels), shelter and nesting sites, substantially reducing their numbers. Round gobies are also voracious predators of eggs of native fish, many important to the angling industry. The goby's robust ability to survive in degraded environmental conditions has helped to increase its competitive advantage compared to native species. Many native predatory fish such as smallmouth bass, largemouth bass and walleye have begun to prey on round gobies. These game fish feed so heavily on the abundant gobies that a bait company, called Culprit, has created a soft plastic bait called the "Great Lakes Goby" to exploit this behavior. The incorporation of the round goby into native foodwebs, coupuled with the goby's ability to consume large numbers of invasive mussels (zebra and quagga), may result in greater bioaccumulation of toxins such as PCBs higher in the food chain, since these mussels filter-feed and are known to accumulate persistent contaminants.
An unintended benefit of the round goby's introduction is that the Lake Erie Watersnake, an endangered species, has found it to be a tasty addition to its diet. A recent study found the introduced fish 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 melanostomus, 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.
Alpena National Fish and Wildlife Conservation Office. <http://www.fws.gov/midwest/alpena/roundgoby.htm>
American Fisheries Society. <http://afs.allenpress.com/perlserv/?request=get-document&doi=10.1577%2F1548-8659(2000)129%3C0852%3AAAGORG%3E2.3.CO%3B2>
Aquatic Invasive Species-Minnesota Sea Grant. <http://www.seagrant.umn.edu/ais/roundgoby>
Global Invasive Species Database. <http://www.issg.org/database/species/ecology.asp?si=657&fr=1&sts>
“Goby.” The New Encyclopedia Britannica. 15th ed. Vol 5. pg 319. Chicago:
Encyclopedia Britannica, Inc, 2007.
“Goby.” The World Book Encyclopedia. 2006 ed. Vol 8. pg 243. Chicago: World Book,
Inc, 2006.
Harmful Aquatic Hitchhikers. <http://www.protectyourwaters.net/hitchhikers/fish_round_goby.php>
Minnesota DNR. <http://www.dnr.state.mn.us/invasives/aquaticanimals/roundgoby/index.html>
Round Goby/Fish of the Great Lakes by Wisconsin Sea Grant. <http://www.seagrant.wisc.edu/greatlakesfish/roundgoby.html>
U.S. Fish and Wildlife Service. <http://www.fws.gov/midwest/alpena/roundgoby.htm>
