The Invasion of the Gobyfish(Family Gobiidae)

By Carmelo “Mel” Russo

In very recent times, an exotic fish, new to the Finger Lakes has made headlines. The nuisance newcomer is the round goby (Neogobius melanostomus). The species, which is native to the Black and Caspian Seas, was mistakenly introduced to the Great Lakes by the emptying of the ballasts of cargo ships from eastern Europe. In the early 90’s the zebra and quagga mussels were introduced in the same manner, from the same origin.

The round goby can be as long as 6 inches but most are about 3-4 inches. They can be positively identified by their silvery/mottled color, the absence of a lateral line on the side, and a large dark spot at the posterior base of the anterior dorsal fin. In addition, there is a dark spot at the base of the pectoral fins. The pelvic fins are circularly connected and located towards the front bottom of the fish rather than towards the rear.

As common with most species when introduced to an ecosystem, the gobies have reproduced in great numbers. This is due to a lack of stronger competition for food and reproductive space as well as low natural predator populations. Most recently, the goby has made the news in Cayuga Lake because of the large spring die off due to a fungal infection affecting it and some of the indigenous species of pan fish. Although this appears to have knocked out thousands of gobies, the most fit and resistant individuals survive and pass on their favorable genes to the next generation, which can be termed in some circles as a subtle example of evolution.

Not only will the round goby survive, it will do so with great proliferation. They are masters of reproduction. Each female can produce more than five thousand eggs at a time and can spawn up to six times a year. The eggs are deposited in crevices between the rocks of the shallows. After the male fertilizes them, he guards the nest and provides continual, highly oxygenated water by fanning the eggs with his pectoral fins. It is said that there is a hatch rate of 95% which is excellent in the fish world.

Gobies push aside the native, beneficial inhabitants of the shoals of a lake such as sculpins, darters, and troutperch by taking over the habitat as well as feeding and/or breeding areas. In addition, they can eat the eggs of shallow water breeding species as well as aquatic insects, crustaceans and small fishes that desirable fish would eat.

On the other hand, gobies may serve as food for bass, pike, perch and walleyes (although not many walleyes are in Cayuga or Seneca Lakes). Other good news is that a single goby can eat up to 100 zebra mussels per day and can process them very efficiently. This is because gobies have a set of molar teeth in their throat (pharyngeal teeth) which grinds the shells of the bivalves and then extracts the meat nutrients lower in the digestive tract. The pulverized shells are separated and then eliminated.

Since the goby is a benthic (bottom dwelling) organism, mussels on posts and the hulls of boats are unaffected.

Watch for the culprits as well as another alien, the tubenose goby (Proterohinus marmaratus) in the shallows of Cayuga and Seneca Lakes. The tubenose, so named because of the protruding tubes it has for nostrils, inhabits more weedy environments. The two species look similar except P. marmaratus lacks the dark spots at the base of the dorsal and pectoral fins and of course, there are those tubular nostrils! Although they’re apt to cause some disruption at first, somehow and hopefully, the Gobiidae will fit into the 10,000 year ecosystems of Cayuga and Seneca Lakes.

Resource: Hubbs 2004

Post thoughts:

Zebra mussels filter tons of plankton food organisms from the water thereby concentrating any toxins contained in the plankton into their own, zebra mussel tissue many times over. In turn, while gobies ingest scores of zebra mussels per day; they too are concentrating the toxins even more and so on up the food chain to top level consumers like bass, pike, trout, and humans. Perhaps a study should be done in a few years to determine the levels of various materials such as PCB’S, DDT, heavy metals, and other accumulating contaminants in the now, edible fish of our lakes.

Gobies will readily take the bait of perch fisherman. Since the invaders are mainly benthic in their habitat, it may help to keep the bait further up from the bottom of the lake to avoid them. Both species of gobies are said to be edible (commonly in eastern Europe) with or without the bones but the author can’t bring himself to recommend them for consumption.

~ M. R.