| The introduction of exotic species is a growing
concern, particularly as we move increasingly towards a global economy.
Unfortunately, there seems to be little that can be done to curb what is
seen as an growing trend. Take, for example, the mode of introduction of
this goby. Effectively controlling the intake and discharge of ballast
water is probably beyond the means of most governents today.
 For
an article on another introduced species that has become a threat to the
local biota .
[to
an interesting statement by a senior Canadian fisheries researcher about
the significance of exotic introductions to the world's native fish populations.]
|
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.
``We are concerned about any invading exotic,''
he said. ``It will compete with and displace other fish species and that
will create instability.''
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.
REUTERS@
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