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Entries in invasive species (192)

Friday
Oct242014

Finding Ways to Tame Lionfish

Years ago, Missouri wildlife managers decided to reduce an exploding deer population in a St. Louis suburb. But instead of culling the herd humanely, they bowed to pressure from animal lovers, and, at great expense, trapped and moved deer to a more rural area.

Follow-up research revealed that those deer died of starvation. They had grown so accustomed to eating tulips, roses, and other domesticated plants that they did not recognize wild forage.

Besides showing the folly of trying to manage wildlife by emotion instead of science, this example reveals one of the reasons that exotic species can become so prolific and troublesome in their new habitats. Native species do not see them as food, and, consequently, their populations are free to grow unchecked by predation.

Down in the Caribbean, divers are trying to do something about that by teaching sharks to eat invasive lionfish. The latter are gobbling up native species, especially reef fish.

“From a scientific point of view, we don't know how successful the project is. But, apparently, recent videos show native top predators are starting to eat lionfish without them being previously speared by divers,” says a marine biologist. (Go here to see some great photos of sharks eating lionfish.)

Meanwhile, lionfish populations have declined around Jamaica because another species is eating the invaders --- man.

Dayne Buddo, a Jamaican marine ecologist who focuses on marine invaders at the Caribbean island's University of the West Indies, attributes much of the local decrease in sightings to a growing appetite for their fillets. He says that Jamaican fishermen are now selling lionfish briskly at markets. In contrast, a few years ago island fishermen "didn't want to mess" with the exotic fish with spines that can deliver a very painful sting.

The same strategy eventually may help us control Asian carp in the nation’s rivers and impoundments. Go here to check out my post about that.

Friday
Oct172014

Ground Zero for Asian Carp Invasion

Havana, Ill., is Ground Zero for the Asian carp invasion, according to the Illinois Department of Natural Resources. On the Illinois River, it’s about 200 miles south of Lake Michigan and 120 miles north of the Mississippi.

“You find more carp per acre, per mile of river, tan nearly anyplace else in the world,” says Kevin Irons, DNR’s Asian carp program director.

If you doubt that, check out this video.

Based on electrofishing surveys, bighead and silver carp now account for about 60 percent of the fish biomass in that stretch of the river. That means native species have declined dramatically because the exotics outcompete them for food and habitat.

And peaceful boat rides are a thing of the past because of silver carp, which go airborne when startled.

“People have been hit and seriously injured,” says DNR’s Matt O’Hara. “I know there have been some cases of broken noses and jaws.

“Pretty distressing when you come out here and you’re looking for native fish, and all you see is invasive Asian carp,” he adds.

Wednesday
Oct012014

Commercial Fishing Is Ally for Anglers in Battle Against Asian Carp

Kentucky Lake Asian carp. Photo by Steve McCadams

A recent study by University of Notre Dame researchers suggests that  consequences of an Asian carp invasion into the Great Lakes may not be as catastrophic as many fear.

“If bighead and silver carp were to establish in Lake Erie, local fish biomass is not likely to change beyond observations recorded in the last three decades,” the university said in a press release about the findings.

Scientists pointed out, however, that the study mainly highlights the uncertainty, adding that the walleye population could decrease by as little as 10 percent or as much as 40.

“The range of possibilities concerning walleye biomass shows that the potential effect to this species is highly uncertain,” said Roger Cooke, one of the study’s authors.

But what’s happening right now in Kentucky Lake and many more of the nation’s bass fisheries along major rivers is not theory. It’s reality.  The exotic fish are there in massive numbers. For example, a first-of-its kind commercial tournament on Barkley and Kentucky Lakes last year netted 82,953 pounds of bighead and silver carp --- that’s more than 40 tons--- in just two days.

And this reality does not bode well for the future of sport fishing.

“If we don’t do something, bass fishing will be over with in five to ten years. You won’t be able to run a bass boat on many of these waters,” said J.D. Johnson, owner of Gulf Pride Seafood.

“If people don’t wake up, we might as well hang it up.”

Working with Carp Management Group of America LLC, Johnson is at the forefront of an effort to garner both angler and financial support for commercial harvest of carp. And he’s not alone.

B.A.S.S. National Conservation Director Gene Gilliland also supports the effort, as do fisheries chiefs in Kentucky and Tennessee.

“Fishermen need to get behind this idea of commercial netting,” Gilliland said. “It’s the only viable solution until someone develops a magic pill.”

“We have to do something now before our lakes and rivers become so over-populated with Asian carp that our native fish never will be able to make a comeback,” said Tennessee’s Bobby Wilson.

“We may not be able to eliminate Asian carp by this method. But the goal is to reduce their numbers so that they will not have a significant impact on our native species of fish.”

Kentucky’s Ron Brooks added that the carp pose a dire threat to “the very base of the aquatic food pyramid” because they feed on phytoplankton and zooplankton, primary forage for newborn bass, crappie, and other sport fish.

The invaders pose that threat because of their massive appetites and huge numbers. A carp eats 5 to 20 percent of its body weight each day as it grows to an average weight of 30 to 40 pounds. A female can lay hundreds of thousands of eggs at a time, and she can do so multiple times annually.

Even knowing all this, however, some bass anglers likely are shaking their heads and saying that they don’t want nets in their waters. But Gilliland said commercial harvest does not harm sport fisheries --- even when gillnets are used.

Most significantly, however, gillnets aren’t the best way to harvest Asian carp, according to Johnson. “We call it ‘strike fishing’ and we’ve done it for years with mullet,” he said.

Schooling fish are encircled by net, driven inward, and quickly harvested. No nets are left unattended to snag whatever swims by.

“I can put 900 feet of net down to 200 feet in less than a minute,” Johnson said.

He added that he could send 575 metric tons of carp to Asian each year, if only the facilities were available to process them. Right now, though, harvested carp are used mostly for fertilizer and silage, and that’s not profitable enough to sustain an aggressive commercial fishery.

“In Tennessee, things are moving at a snail’s pace regarding commercial harvest, processing, and marketing of Asian carp,” Wilson said.

“Funding is the major issue, as it is with almost every venture.

“We know that commercial fishermen can catch them, and we know that there is a market for them overseas, as well as within the United States. The missing pieces are the processing plants and the price per pound for commercial fishermen.”

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

Friday
Sep262014

Battling --- And Besting --- The Big One

Once again the huge fish bulled for deeper water. And once again I pumped and reeled to regain line.

If frogs croaked or birds sang on this cool evening in early fall, I didn’t hear them. The only sounds that I remember are the “Whap! Whap! Whap!” of the monster’s broad tail as it slapped the surface of the still, shallow water, and the “Zsst! Zsst! Zsst!” of the drag on my spinning reel as it protected my 12-pound line from breaking.

The fight lasted 15 minutes at least, probably more. I knew that I had to weaken the grass carp to have any chance of wrestling it ashore, but I also realized how perilous our connection, with light line and small hook. That’s why I eased off on the drag each time I brought it close to my dock. At close range, one hard headshake from a fish that size, even a tired one, would part the line.

Finally, I judged it ready to be landed, knelt on one knee, held the rod with my right hand and scooped with my left. Only my net was far too small to get much more than its head in it. And as I belatedly realized that, a barb on the little treble snagged in the mesh. Now, a foot or so below the side of the dock,  I had the huge carp half in and half out of the net, and there was no way I could lift the fish with one hand, even if it all did fit.

Suddenly, the once tired fish became manic, thrashing wildly, and I all but acknowledged that I had lost the fight.  I was certain that the line would break as the carp jerked against the resistance of the hook embedded in the net.

Hook on right is the one that I removed from carp and net.

But I pushed the net as deep as I could, and the fish bolted farther into it instead of away from it. Nearly simultaneously, I dropped the rod, grabbed the handle with both hands and heaved.

And finally there it was, a 40-pound-plus grass carp half in and half out of the net on my dock. Somehow, someway, I had managed to land the beast with a net that likely was better suited for butterflies than fish of this size.

I know that it was 40 plus because it was far heavier than my previous best, which had bottomed out a 30-pound scale.

During the nine years that I’ve lived on this 10-acre semi-private lake, I’ve caught about 20 of the illegally stocked grass carp, which have suppressed the bass, bluegill, and catfish populations and degraded the water quality.

Aquatic vegetation never has been a problem in this normally clear, spring-fed lake, but ignorant property owners stocked the carp, thinking that they were filter feeders that would improve the water quality. One of them actually told me that.  In truth, grass carp are the equivalent of aquatic cows, adding to the nutrient load as they grow to massive size, and contributing to algae blooms as they stir up the bottom.

But they are fun to catch, fighting a lot like big redfish, and I’ve perfected the technique --- at least for my little lake. I fish only for the carp that I can see. Once I’ve spotted one, I toss a bread ball under a bobber in front of it. Sometimes, I have to increase the depth of the bait to get the fish to take. Last night, I had to do that three times.

When I go back out there this evening to look for the three others that saw with the one that I caught, I should have it at the proper depth on the first try.

And I will have a larger net.

To read about the 30-pound carp that I caught and learn more about why grass carp generally are bad news for sport fisheries, go here. I'm not suggesting that grass carp can't be used to manage aquatic vegetation in certain circumstances, but they're tools that only fisheries biologists should consider.

Tuesday
Sep232014

Time to Begin Limited Harvest of Goliath Groupers?

 Photo by Robert Montgomery

Count me as one who favors a limited permit system for harvest of goliath groupers by recreational anglers.

The large, predatory fish have made a remarkable recovery in Florida waters, with fishermen frequently tangling with them as they pursue other species. And sometimes the goliaths eat those other species as they are being reeled in.

A legitimate concern, though, is how an exploding population of exotic lionfish will affect the population. The invaders are notorious predators on juvenile fish of many species, goliaths included.

The Florida Fish and Wildlife Conservation Commission will consider management issues when a new stock assessment is completed next spring.

Overharvest by commercial and recreational fishermen nearly pushed the goliaths to extinction by the mid 1980s. But during the 25 years since harvest was banned, they’ve rebounded in dramatic fashion.

The News-Press reports the following:

In a University of Florida survey, 1,518 recreational hook-and-line fishermen, 574 recreational spear fishermen, 697 commercial fishermen and 352 sightseeing divers answered a series of questions about goliath grouper.

Among the findings:

  • Commercial fishermen: 68 percent were interested in harvesting goliath grouper; 32 percent said goliath grouper encounters were desirable; 42 percent said the goliath grouper is a nuisance species.
  • Recreational hook-and-line and spear fishermen: 78 percent were interested in harvesting goliath grouper; 52 percent said goliath grouper encounters were desirable; 20 percent said the goliath grouper is a nuisance species.
  • Sightseeing divers: 87 percent said goliath grouper encounters were desirable; 9 percent said the goliath grouper is a nuisance species (these divers were not asked about their interest in harvesting goliath grouper but did express support for keeping the fishery closed to harvest). 

Some hook-and-line fishermen and spear fishermen consider goliath grouper a nuisance because they steal hooked and speared fish.

Sightseeing divers, on the other hand, like seeing and photographing goliath grouper, which can grow to 8 feet in length and weigh 800 pounds.

"We learned from the survey and anecdotal information that the difference is the individual's goals," said Florida Sea Grant agent Joy Hazell, co-author of the report on the survey. "If a diver sees a big, giant fish that he's spent money to see, it's a good experience. If a fisherman has a good fish hooked and loses it to a goliath grouper, the perception is he's lost money. As the goliath grouper population has increased, there's a perception for some people that it's becoming a problem,"

Spearfisherman Zachary Francis of Fort Myers is all for a well managed goliath grouper harvest.

"They should have a bag limit, like one per boat per day, and a slot size," he said. "The fact is that they're overpopulated. Any dive you make, you'll see five or six. They can be very aggressive. They're the premier predatory fish on the reef, and they're eating all the other groupers."

While goliath grouper will aggressively go after speared and hooked fish, studies show that its main diet is crabs and other crustaceans and slow-moving fish.

Brent Argabright, owner of Dean's Dive Center in Fort Myers, is also interested in a managed harvest.

"I don't think they should just give people free rein or just have a 10-day season," he said. "If the state wants to raise money as well as clean out a few of them, they could do like they do with alligator and sell permits."