This area does not yet contain any content.
Get Updates! and Search
No RSS feeds have been linked to this section.

 

 

 

 

 

 


 

 

 


 

 

Entries in gobies (4)

Tuesday
Nov122013

Round Goby Expansion Continues

 

U.S. Fish and Wildlife Service photo of round goby.Since first discovered in 1990, the round goby has prospered in the Great Lakes, but that doesn’t mean the bottom-dwelling fish is content to stay there.

More and more in recent years, it has expanded its range. For example, it’s now established in about 170 miles of Wisconsin rivers and streams that feed Lake Michigan. The native of Eastern Europe also has moved into Ontario’s Trent River, Rice Lake, and Simcoe Lake, one of the province’s most famous smallmouth fisheries.

Most recently, it has been found in Cayuga Lake, the longest of New York’s Finger Lakes, and it also is suspected in Oneida. That expansion likely will be a mixed blessing, as it has been in the Great Lakes.

In Cayuga and Oneida, gobies may prey on eggs of lake trout, sculpin, and darters, according to the Cornell Cooperative Extension Invasive Species Program. Additionally, they make crowd out native species, including bass, from prime, nearshore spawning areas.

“The biggest concern for anglers is that when gobies get to high density, the prey fish will have plenty of food to eat, and it might be harder to catch fish,” said Cornell biologist Randy Jackson.

For smallmouth bass anglers, however, that hasn’t been the case in waters where gobies have long been established.

“They’ve been a huge plus in Lake Ontario and the St. Lawrence River, where (zebra) mussels came in first and then gobies came in to eat the mussels,” said guide Dean Meckes, who fishes those waters, as well as Cayuga and Oneida.

“Smallmouths are getting way bigger now,” he added, pointing out that 11 pounds often won a one-day tournament in the 1990s.

“Now you need 20 to 24 pounds (five fish) to win,” he continued. “In a tournament last weekend, I had 21-4 on the first day and was in fourth place. First place had 26 pounds.”

Research on Lake Erie, meanwhile, shows that young smallmouths are growing faster. Ohio biologist Kevin Kayle theorizes that is because gobies spawn late into the summer, allowing young-of-the-year bass to move more quickly to a fish diet.

On the negative side, Kayle said, “We’ve seen a decline in sculpins and darters because of gobies.”

Another concern is that toxins bio-accumulate in gobies as they feed on zebra mussels. The exotic fish then are eaten by birds and larger fish. Researchers believe that loons and other fish-eating birds have died of botulism because of this. The invaders, which grow to 6 or 8 inches, also are considered a nuisance by some anglers because they are such proficient bait stealers.

And This Just in . . .

After I wrote the above article for B.A.S.S. Times, I received this additional information from Randy Jackson, a fisheries scientist at Cornell University Biological Field Station on the shores of Lake Oneida:

“In general, we hate to see any new invasives enter our inland lakes because impacts are never predictable.”

The major threat that the goby poses is to bass reproduction, he said.

“Most people focus on impacts on bass nests where guarding males have been removed. While no doubt individual nests would be at risk if males were removed, we certainly haven't seen any reduction in bass production in Lake Erie with the combination of spring fishing and gobies.

“I suspect it is the classic question of individual nest threats and lakewide production risk. I'm inclined to think that except under circumstances of extreme spring fishing pressure that we would not likely see any system wide reductions in bass production with gobies.

“Many of the other likely goby activities would very likely be positive to sport fish. Where they occur, both walleye and bass seem to make great use of them, so they would likely represent an additional prey resource that could result in faster growth rates.

“They spawn throughout the summer so there will potentially be a steady supply of small fish prey for young bass and walleye. We know in Oneida that young walleye have had some difficulty remaining piscivorous through the summer due to poor yellow perch production, so gobies might be a benefit to them.

“Double-crested cormorants also like gobies, so gobies could represent an additional buffer for sport fish to cormorant predation. And gobies eat zebra and quagga mussels, which we have plenty of.

“I suppose my primary concern is how gobies might impact angler catch rates. While we don't have great data for bass, we have seen that in Oneida, walleye catch rates are very tightly linked to the abundance of forage for adult walleye, not the numbers of adult walleye. In years when yellow perch produce large year classes, small perch are readily available to walleye and angler catch rates go down.

“In years when perch are rare, walleye catch rates are high. Gizzard shad play a similar role. When they are abundant, walleye can be hard to catch.

“If gobies establish at high densities, they could negatively impact angler catches. So adult game fish may grow faster but anglers won't have as much luck catching them. There is some irony in that gobies could potentially benefit many dynamics of our sport fish but at the same time create conditions where it is more difficult for anglers to benefit from that.”

Tuesday
May072013

Lake Erie Smallmouth Fishery Remains Strong Despite Goby Invasion

 As the population of invasive round gobies exploded in the mid to late 1990s in Lake Erie, resource managers feared trouble ahead for the smallmouth bass population.

“Agencies (all around the lake) went into protective mode for smallmouth bass,” said Kevin Kayle, a biologist with the Ohio Department of Natural Resources at the Fairport Harbor Fisheries Research Station.

They did so by implementing restrictive harvest regulations during spring. By reducing angler effort, they hoped, aggressive male bass wouldn’t be as likely to be pulled off nests, leaving eggs vulnerable to goby predation.

Fortunately, those fears have proven unfounded. Gobies have not damaged the smallmouth population, and likely they wouldn’t have even without protective spring regulations. Instead, bass have benefitted, as the small, exotic fish is now a dietary staple.

“Where we see the change is in growth of young smallmouth,” said Kayle. “They still top out at about 20 inches. But for the first three years, we’re seeing advanced growth.”

Why is this happening?

Gobies spawn late, while smallmouths spawn early. Thus, young-of-the-year bass can eat nutrient-rich fish --- larval and juvenile gobies --- during their first summer and fall.

But the goby invasion has damaged forage species that bass traditionally depended upon. “We’ve seen a decline in sculpins and darters because of gobies,” Kayle said.

For bass, meanwhile, spring storms seem to be the biggest limiting factor for abundance, the biologist added. Especially with a northeast or northwest wind, waves up to 15 feet go crashing into the near-shore areas, where bass spawn in waters of 20 feet or less.

“That storm surge jostles around the eggs and can force adults to abandon their nests,” Kayle explained.

Upwellings in the Central Basin during late summer and early fall also can harm bass, as well as most other species. Several days of wind out of the north or south pushes the surface water in one direction, while bottom water moves in the other. This churning action forces oxygen-depleted water to the top.

“When this anoxic water comes close to shore, we can see fish kills,” the biologist said. “Some years, it’s drum. But in the worst years, we see smallmouth too.”

Blooms of blue-green algae that die and then decay in deeper water feed the problem. “Bacteria down there decomposes the dead algae and uses up oxygen,” he said. “And no oxygen can come in (from above) because of the thermocline.”

Despite these naturally limiting factors, though, the smallmouth population of Lake Erie is doing well. “Long-term catch rates are relatively good, while total effort has gone down to what we saw in the 1990s,” Kayle said. “We’ve had more young fish in the last few years, after a dry spell in the mid to late 2000s.”

(This article appeared originally in B.A.S.S. Times.)

 

 

Monday
Apr012013

Exotic Species Are Killing Loons --- Not Lead

As preservationists --- many with an anti-fishing agenda --- continue to press for bans on lead fishing tackle to protect loons, read the following story to see what is really killing the birds. This is a real danger, not one manufactured to support an ideology, with little basis in science and fact.

And it provides a tragic example of how introductions of exotics can have unforeseen consequences.

Chain of Environmental Consequences Slaughtering Birds

 

Wednesday
Feb082012

Everglades Devastation a Warning for Fisheries?

Python swallowing an alligator.

Pythons are wiping out wildlife in the Florida Everglades.

Here’s an excerpt from an article in the Tampa Bay Times:

“In a report published Monday, a team of scientists said they found that between 2003 and 2011, the areas where pythons had proliferated saw a 99 percent decrease in raccoons, a 98 percent drop in opossums, a 94 percent drop in white-tailed deer and an 87 percent falloff for bobcats. And that's not the worst of it.

“‘We observed no rabbits or foxes,’ the report noted.

“The bottom line: ‘In areas where pythons have been established the longest … mammal populations appear to have been severely reduced.’"

Of course, pythons are an exotic species that should not be in the Everglades. They are present because of the federal government’s failure to competently regulate the exotic pet industry.

Just add water and you get an idea of what could happen to our fish and other aquatic species because of exotic carp, snakeheads, gobies, and other invaders.

Granted, the snakehead is the only top-level aquatic predator so far --- as is the python on land --- but exotics can wipe out natives through means other than eating them. They can take over habitat and gobble up all of the food. They can introduce disease. In rare cases, they even can interbreed, weakening the genetic integrity of natives.

The truth is that established populations of invasives can have consequences that we can’t even contemplate until it’s already too late.