The Lake Erie Watersnake: A Rare Success Story Resulting from the Introduction of Round Goby



Invasive species often have rapid and far-reaching negative impacts on populations and ecological communities. These effects are most common when invasive species have few competitors or predators. Although higher level carnivores do consume invasive species, quantitative effects of new and abundant food sources on predators have rarely been documented and, as a consequence, potentially positive effects of invasive species may be under appreciated. There was an investigation on the effects of the invasive round goby on diet composition, growth rate, and body size of the Lake Erie Water Snake which is threatened in the USA and endangered in Ontario, Canada. Water Snakes have shifted their diet, and round gobies now constitute >92% of prey consumed. This shift in diet has occurred in just one or two Water Snake generations, yet has resulted in more rapid growth and attainment of larger body size in Water Snakes. These positive effects may reduce predation, speed reproductive maturity, increase offspring production, and fuel population growth of this threatened species.

Round Goby: How it Got Into the Great Lakes and How to Keep Them from Spreading



http://www.seagrant.umn.edu/ais/roundgoby

 Habitat:

     Round goby are widespread in the Sea of Marmara and in the rivers of its basin.  They can also be found in the Black Sea and the Sea of Azov along all coasts and freshwaters of their basins.  Round gobies also inhabit the rivers of Crimea and Caucasus.  Since the year 1990, the round goby is considered to be an "introduced" or "invasive" species in the Great Lakes region of the United States and in certain regions of Europe.  Round goby were accidentally introduced to the Great Lakes via ballast water transfer in cargo ships.  They were first found in America in the St. Clair River in 1990.  Since their introduction, round gobies have had a profound impact on native ecosystems and on the economy due to their interference with the actions of sport fishing anglers.

How to prevent them from spreading:
-Learn to identify the round goby from the ruffle, another fish species.
-Inspect and remove aquatic plants, animals, and mud from boats, motors and trailers.
-Drain the water from boats, livewell, and bilge before leaving any water access point.
-Dispose of unwanted bait and worms in the trash; don't dump them into the water.
-Never dump live fish into any body of water.
-If you catch a round goby, kill it and freeze it.

List of Native Great Lakes Species Threatened by the Round Goby

Sculpin

Logperch

Trout (eggs and fry)

Sturgeon (eggs)

Native Snails

Native Mussel Species

Impacts of Goby in the Great Lakes



http://el.erdc.usace.army.mil/ansrp/neogobius_melanostomus.pdf

-Populations of native sculpin and logperch have exhibited a substantial decline in the Saint Clair River where the round gobies were first introduced.

-Round Goby eat darters, sculpins, logperch, the eggs and juveniles of trout and the eggs of lake sturgeon.

-Transfer of contaminates in the food cycle.

-Round gobies interfere with the actions of anglers.  For example, gobies eat the bait off hooks and anglers catch gobies instead of coveted sports fish.

-Round gobies interfere with habitat restoration projects in the Great Lakes and other regions.

-They behave aggressively toward other fish and drive native species from prime spawning areas.

-Round gobies tend to out compete native fishes for food partially due to an ability to feed in complete darkness and to the presence of a suctorial disk located on their pelvic fin which allows them to attach to rocks and remain fixed on the bottom in fast currents.

Some positive impacts include:

-Gobies eat zebra mussels, another Great Lakes invader.

-They also serve as a food source for larger predatory fishes and water snakes.

 

General Characteristics of the Round Goby

Juvenile Round Goby

Juvenile round gobies are generally a solid, slate gray in color.  They have a light border around the black spot which is usually present on the frontal dorsal fin.  Juvenile round gobies typically resemble adult gobies.

Adult Round Goby

Adult gobies typically have mottled gray, olive green, and brown markings on the skin.  Their dorsal fins may be greenish in color and it usually lacks spines.  A black spot is sometimes found on the front dorsal fin but the round gobies of the Great Lakes tend to lack this identifying feature.  Round gobies have raised eyes on the top of the head and fused pelvic fins that form suction cups.  They can grow up to 17.8 centimeters in American waters, but can get even larger in their native habitat.  Male gobies guard nests of eggs and newly hatched offspring.  Gobies are able to feed at night and can detect prey only when stationary.

http://el.erdc.usace.army.mil/ansrp/neogobius_melanostomus.pdf