Invasive Species in USA Waterways - Part 63
The Round Goby is an invasive species of euryhaline bottom-dwelling goby in the Gobiidea family. Native to Central Eurasia including the Black Sea, the Caspian Sea and the Sea of Azov and tributaries.
Invasive Species Definition
The definition of an invasive species is any species that is not native to our ecosystems and cause harm when introduced to the ecosystems. Furthermore, these may include amphibians, plants, insects, fish, fungus, bacteria and more. Impacts on the environment may cause economic loss or affect human health.
While, Invasive species tend to grow and reproduce quickly and spread aggressively with the potential to cause harm on the environment, economy or even human health. Therefore, given the label “invasive”.
Description of the Round Goby
Small, soft bodied fish with a black spot on the first dorsal fin at the posterior base. Juvenile gobies are grey in color. While, they become mottled with grey, black, brown and olive-green markings. Meanwhile, adult males turn inky black during the spawning season and develop swollen cheeks.
Furthermore, they range in length from 4 to 10 inches. Average in weight from 0.176 pounds to 2.816 ounces. They have large eyes that slightly protrude from the top of their heads.
The pelvic fins are fused to form a single disc on the belly of the fish shaped like a suction cup. They have 7 – 8 dorsal spines and 12 – 17 soft dorsal rays. Further, have 1 anal spine and 9 – 14 soft anal rays. Generally, they have 31 – 34 vertebrae.
Furthermore, the first branched ray of the second dorsal fin is about the length of the penultimate ray. While, they have no scales on the mid-line of the nape or in front of the preoperculum.
Generally, the male goby is larger than the female. Males and females are easily differentiated through the shape of their urogenital papilla. In the male these are white to grey, long and pointed. While, in females they are brown, short and blunt tipped.
Biology of the Round Goby
A salt tolerant species that inhabit freshwater and marine ecosystem. However, they prefer brackish waters. Widespread in rivers, basins, coastal lakes, lagoons, lakes, harbors and continental shelves with sandy and rocky bottoms with low silting.
Generally, occur at depths from 1 to 17 meters and temperatures from 39.2°F to 86°F. Mostly found in well vegetated areas that are warm. While, they can tolerate low oxygen content waters for several days.
Predators and Parasites
There are approximately 52 species of parasite registered in the Round Goby in their native area. While, the most abundant parasites are trematodes and cestodes. While, there is a long list of parasites, only some of these may infest humans. Parasites include.
Distribution of the Round Goby
The Round Goby occurs in Eurasia, Black Sea, Caspian Sea, Baltic Sea and other major Eurasian rivers and basins. As well as, Sea of Marmara, Sea of Azov, Crimea, Caucasus, North American Great Lakes and some states in the United States. Namely, New York, Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania and Wisconsin.
Effect on the Ecosystem
There are various effects that the Round Goby has on ecosystems. Including widespread occupation of inshore habitats with cover especially plants or rocky rubble. Causing declines in native fish species as the Round Goby have become abundant and prey on eggs and fry of Darters, Lake Trout, Sculpins and Logperch. Further, there are dietary overlaps between native fish species like the Rainbow Darter (Etheostoma caeruleum) and Logperch (Percina caprodes) and the Round Goby.
While, spawning sites are limited with competition between the Sculpins, especially the Mottled Sculpin (Cottus bairdi) and Round Goby. Furthermore, the Round Goby is extremely aggressive when defending their spawning sites and therefore occupy prime spawning areas keeping the native fish out and even evicting native fish from their breeding grounds. While, the Round Goby feeds mainly on Zebra Mussels, which other fish do not eat, they uniquely exploit a resource that could fuel a population explosion.
The Round Goby have caused economic impacts since 2004. Smallmouth Bass fisheries closed due to high predation rates by the Round Gobies on fish nests eating up to 4000 eggs in 15 minutes. Therefore, causing considerable loss in funds generated by recreational angling. While, the Round Goby is a vector for the spread of avian botulism detected in Double-Crested Cormorants (Phalacrocorax auritus).
However, there are some positive impacts that the Round Gobies have had on the ecosystem. They are the main diet of water snakes (Nerodia sipedon). Therefore, the water snakes’ populations have increased, with high growth rates and larger body sizes enabling the water snake to be removed from the Endangered Species List. Furthermore, the Round Goby have become an abundant food source for several sport fishes including Walleye, Yellow Perch, Largemouth Bass, Smallmouth Bass and Lake Sturgeon.
Introduction to the USA
Introduced to the Great Lakes via ballasts on a freighter. While, distribution to the Baltic Seas was determined by shipping activity. Further, in some cases egg clutches have been transported attached to hulls of ships, farther facilitating introductions to other areas. While, first discovered in Norther America in the St Clair River in 1990.
Has become a food source to many predatory fish such as Smallmouth Bass, Largemouth Bass, Walleye, Whitefish, Burbot, Salmon, Cutthroat Trout and Rainbow Trout. While, also having negative effects on the ecosystems and causing economic losses. Further, the Round Goby feeds on Zebra and Quagga Mussels therefore reducing the populations of these unwanted pests.
While, being a food source to other endangered species such as the water snake, encouraging a strong come back in this species. While, non-native occurrences have been made in Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania and Wisconsin.
Management of the Round Goby
Once established there is very little that can be done to eliminate the Round Goby. Therefore, it is important to educate the public not farther spread this invasive species. Never throw unwanted live bait into the water, place it in the trash and never dump fish from one water source into another water source. Furthermore, do not used Round Gobies as live bait. Moreover, a very good habit to follow is to always drain water out of your boat, live well and bilge before leaving a water source. Therefore, preventing farther spread of the species.