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Published: 5/14/2006

Bigmouth gobies vs. smallmouth bass

The problem with smallmouth bass in Lake Erie is that they are just too good and too popular a gamefish.

The problem with smallmouth bass in Lake Erie is the round goby.

Take your pick of the foregoing statements, but they will take you to the same place, for they are intertwined.

Gobies are the olive-green, bug-eyed, pesky little pest-fish that were carelessly, thoughtlessly dumped in Lake Erie by international shipping's ballast water, thanks to continuing federal laxity in regard to Great Lakes protection. Their populations have exploded.

It is well established that

gobies, an invasive forage

species from Eurasia, are

egg-eaters extraordinaire which will devour the spawn in unguarded smallmouth nests in short order. Which is why the Ohio Division of Wildlife, wary about wavering smallmouth production and rising sport-fishing pressure, opted for the catch-and-release-only rules during spawning time, May 1 through late June, two years ago.

The reasoning is that allowing a smallmouth guard-male to return quickly to its territory after being caught, will help protect the nest. The release-rule, along with reduced daily creel limits, five instead of eight, and a higher minimum keeper length, 14 inches instead of 12, have helped.

So has the growing voluntary no-keep practice of many sport-anglers. Many fishermen call it CPR - catch, photograph, release - and they do so always, not just in May and June.

But fisheries researchers still struggle with finding a viable method to sample a given year's production in a more timely way. As it stands now, biologists do not know how well a given smallmouth year-class really is doing until four, five years down the road. This stands in contrast to easier-to-sample walleye and yellow perch, spawning success of which can be told by fairly straightforward annual trawling surveys in open water. It is a management dilemma.

Now comes research from a Bowling Green State University doctoral candidate that shows gobies are worse than just nest-robbers. They are bullies with young-of-year smallmouth.

Chris Winslow, a BGSU biology instructor working on a Ph.D. in aquatic ecology, has spent the last two summers measuring the impact on the growth rates and survival of young smallmouth - less than two inches - in work partly funded by the Ohio Sea Grant program.

Both young gobies and young smallmouth prefer rock, rubble, gravel, and sandy bottoms over open water. But the goby's aggressive, competitive nature intimidates young smallmouth, Winslow found.

Using scuba gear, he placed mesh cages at the bottom of the lake to observe goby-smallmouth interaction.

When young smallies are left alone they preferred the bottom of the cage, close to food and cover. When gobies were present they drove the young smallmouth to the top of the cage. As a result, smallmouth in cages with gobies were just half the size of those in cages with no gobies.

Not only did gobies force young smallmouth to feed in the higher, less food-rich water column, their aggression exposed the young bass to greater predation.

"I'm showing a lot of stress when you're a little bass," said Winslow. "But Jeff Steinhart is showing that you can grow well [as a bass] if you can make it to 45 mm [about two inches]."

At two inches, young smallmouth switch from small bottom creatures called macroinvertbrates - larval insects - to small fish. Like gobies. "As soon as you can switch to fish, life is grand," says Winslow.

Steinhart, now at Cornell University, conducted his smallmouth-goby research while at Ohio State University. His work showed that smallmouth growth rates took off once they reach 1 1/2 to two inches.

So early on smallmouth must make it past two goby hurdles - egg predation on the nest, and territorial intimidation until they grow big enough to turn the tables.

The story is muddled as it often is with exotics,'' said Jeff Tyson, Lake Erie fisheries research supervisor for the state. "Gobies may have a negative impact early and a positive impact later.''

But from the standpoint of a fisheries manager, Tyson adds, "any exotic is going to have a negative impact because of the uncertainty it introduces into the system.''

He added that biologists will not be able to fully assess the impact of the catch-and-release season for another two years. He noted that the fishery "still has a lot of older, bigger fish,'' and creel surveys in 2005 indicated that a lot of anglers released "throwbacks,'' that is, bass under the 14-inch keep length.

The presence of such sub-legal fish is a good sign, looking backward at previous hatches. Last year some young-of-year bass turned up incidentally in yellow perch survey-trawls. But Tyson points out that those simply are anecdotal, not scientifically grounded, indicators of good things.

Winslow at the same time notes: "You could potentially see some huge trophy bass because of gobies [as a food-source]. Insects are just not as energy-rewarding as fish. The question is going to be whether you see the numbers [of bass].''

Another concern surrounds contamination of smallmouth bass by gobies when bass are used as food for human consumption. That is because gobies are "bio-concentrators " of nasty chemical contaminants.

Another infamous character in the Rogues Gallery of invasive species, the zebra mussel, concentrates PCBs from the water and sediments by their filter-feeding. In turn, gobies eat zebra mussels and further concentrate PCB levels in their flesh. Smallmouth feeding on gobies thus get a megadose of PCBs that eventually could put some of them into the do-not-eat category for humans.

That will mean nothing to catch-and-release anglers. But it will to catch-and-eat folks. (An aside to anglers: Find baits that mimic gobies in size and color and make them "swim'' like gobies to boost your success.)

Gobies, of course, are not the be-all and end-all of smallmouth production considerations. Prolonged storm events at the wrong time (during spawning and nesting) can wreak their own havoc, for example.

But a big remaining question for more goby research is how well young smallmouth survive beyond that critical two-inch size. Sums Winslow: "There is still a whole can of worms to be opened."

Contact Steve Pollick at:

spollick@theblade.com

or 419-724-6068.



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