TORONTO (Reuters) - The round goby with its large mouth and oversized, bulbous eyes, has reared its ugly head in Lake Ontario, much to the horror of fishermen who believe it could spell disaster for native fish populations.
The Ontario Federation of Anglers and Hunters raised the alarm this week when it predicted in a news release that the round goby ``will wreak havoc on the aquatic ecosystem.''
``This fish will upset the delicate balance of the ecosystem,'' angler federation spokesman Mark Holmes told Reuters. ``It's a very prolific fish that spawns several times during the year, so a very small number can become a very large number very rapidly.''
The goby probably made its way from Europe in the ballast tanks of ocean-going ships that traveled to Lake Ontario through the St. Lawrence Seaway.
The impact of the round goby's arrival could be felt on several different levels. For example, the round goby feeds on zebra mussels, which filter contaminants out of the water. By eating the mussels, the goby itself becomes contaminated and contaminates the larger fish that prey on it.
Also, said Holmes, the goby is such an aggressive feeder that it will strip the bait right off a hook, which could have a long-term impact on sport fishing and tourism.
But the most likely consequence of the round goby's moving in, said Dr. John Casselman, a senior research scientist at the Ontario Ministry of Natural Resources, is the displacement of native fish populations.
Casselman said that, worldwide, 38 percent of fish populations have been eliminated by exotics, compared with only 17 percent by overfishing.
And while he can't address the goby situation specifically, Casselman explains that when the rock bass arrived in Lake Ontario, in some areas the number of species dwindled from 14 to four, two of those four being the rock bass and the small-mouth bass.
``And since the lake trout won't feed on rock bass, we saw a 20 to 30 percent reduction in lake trout production,'' he said.
Furthermore, an ``exotic invader'' like the goby is ill-equipped to survive any climatic extreme and a severe winter, for example, could wipe it out. You then have a situation where the goby invades an area before dying off, which leaves a vacuum that allows other populations to explode.
``To lose a native species or to have an exotic come in can only result in permanent changes,'' said Casselman.
This news comes at a time where some of Lake Ontario's native species -- the deepwater sculpin, the emerald shiner and the threespined stickleback -- seem to be on the comeback trail.
The sculpin's reappearance, most notably, has scientists very optimistic about the lake's health. Since the sculpin is a bottom feeder, and since most contaminants will sink and gather on the bottom, its resurgence after an absence of almost 50 years had led scientists to conclude Lake Ontario's health was improving significantly.