OMETEPE – A territorial, omnivorous African fish that scientists say is pushing other native species out of their habitats in Lake Cocibolca has the National Assembly debating a bill to prohibit the introduction of exotic species into Nicaraguan waters.
Known commonly as tilapia, the nonnative fish species was introduced into the hemisphere’s biggest tropical lake as early as the 1970s. Still, critics blame a tilapia export farm on OmetepeIsland for making matters worse by cultivating 3,000 tons of tilapia annually in the unique freshwater ecosystem.
Alex Gutiérrez, production manager of the tilapia farm NICANOR, says scientists and politicians are exaggerating the environmental impact that the fish have on the lake.
“Environmentalism is a trend right now,” Gutiérrez told The Nica Times during a recent visit to Ometepe, where NICANOR manages 26 floating tilapia production cages off the volcanic island’s southern shore.
“We get blamed for a lot of what happens to the lake,” he said.
Environmentalists have successfully blocked the company’s plans for a fish processing plant on the island, and warn they will also block any future plans for expansion. But despite the image problem of the 7-year-old company, its manager says business has only been getting better in recent months.
With nearly a decade of selective breeding and an intensive fattening process, the company has managed to nearly double the rate by which tilapia become fat enough to turn into an exportable filet. NICANOR cultivates the fish from birth at an incubation project in the Tipitapa river, and recently began processing filets at a fish plant in Rivas, where it then ships to clients in the United States, Mexico and Costa Rica, who pay top dollar for the taste of nutrient-rich Cocibolca tilapia.
NICANOR’s exports are calculated to reach $1.5 million this year.
Environmentalists, however, claim the environmental costs outweigh the business profits.
“We want legislation that regulates (the introduction of foreign species) starting today, not only in Cocibolca, but in all the lakes,” said Carlos García, president of the National Assembly’s Environmental Commission.
Nicaragua’s Water Law, approved last year, calls for the “prohibition and introduction of exotic invasive species” in Lake Cocibolca. But, García said, the legislation likely wouldn’t apply to tilapia, which NICANOR says is now part of the ecosystem, even if they are originally from the Nile River.
“We don’t want to put the company’s investment at risk. We don’t want to change the rules of the game,” said García, adding environmental authorities should keep a watchful eye on the project.
“We’re not going to allow (NICANOR) to expand,” said Rigoberto López, coordinator of the Lake Nicaragua Basin at the Environment Ministry (MARENA).
The company’s 20-year concession allows for the production of 5,000 tons of tilapia annually. They currently produce 3,000 tons.
A Third World Experiment
Tilapia were first introduced in Latin America as early as the 1950s as part of efforts by international aid organizations such as the United Nations to bring a fastreproducing, highly adaptable, high-protein fish to countries with poor production and high malnutrition.
Exactly when and how tilapia entered Lake Cocibolca is unclear, though there’s a general consensus that the fish – which was being cultivated by small producers in other Nicaraguan lakes – was inadvertently washed into the great lake during flooding as early as the 1970s.
Most small-scale social development tilapia projects have since dissolved due to a lack of technical capacity and training, Gutiérrez said. But over the last decade, tilapia has become a booming export industry throughout the region, with large-scale projects in countries like Brazil, Costa Rica and Honduras.
Gutiérrez says tilapia critics are overstating environmental impacts caused by the ubiquitous fish.
Even if the omnivores eat the eggs of other fish, as scientists allege, in a “solid ecosystem” such as the 8,600-square-kilometer reach of Lake Cocibolca, the effect would be minimal, he said.
Still, he admits that tilapia escape in large numbers and on a regular basis from NICANOR’s floating cages. Last year, he said, 2,500 tilapia escaped because of problems with the nets.
“But local fisherman came and fished them day and night for weeks,” Gutiérrez said. Plus, he added, accidental introductions aren’t such a big deal at this point because tilapia already inhabit the lake.
He also plays down the effect that the waste produced by 3,000 tons of fish has on the lake.
“Not all of that food ends up in the lake as poop,” he said of the 4,500 tons of fish food that NICANOR feeds its tilapia each year.
“What’s not eaten by crabs and other fish is converted into nutrients in a matter of days.”
Tilapia continue to be blamed for problems they have nothing to do with, he said, pointing to fish kills in recent years, which he blames on climactic change resulting in a drop in oxygen levels in the lake.
NICANOR’s manager in Managua, David Senna argues that tilapia – now a fact of life in Cocibolca – can actually benefit the lake’s ecosystem.
“They are a filter for some of these contaminants,” he said. They also serve as a large pool of fish that can counter over fishing problems, he said.
Politics of Environmentalism
At the height of the tilapia controversy, the Central American Water Tribunal, a nongovernmental court that hears water issues but whose verdicts are non-binding, ruled in 2004 that the Ometepe tilapia farm was polluting the lake and violating environmental laws by depleting oxygen levels (NT, July 2, 2004).
Gutiérrez said the attack on the tilapia in Nicaragua came not just from environmentalists, but from politically influential people with stakes in the island. NICANOR, he noted, had no problem getting environmental permits until the former owner of the company moved the floating cages into deeper waters – and closer to lake views of influential neighbors.
But Gutiérrez said the “waters have calmed” since he took over the company’s marketing three years ago. The company recently signed on a major Mexican buyer. “Business is improving,” he said, weaving his panga between circular floating tilapia nets that hold 60,000 fish each.
Biologists argue that tilapia, which have the benefit of millions of years of evolution in Africa, are a more advanced species than the fish native to Nicaragua, such as the much younger cichlids, which represent half of the lake’s 40 fish species and have only evolved for a fraction of time.
One of tilapia’s evolutional advantages is that the female hides her eggs in her mouth, boosting the rate of birth success. Tilapia also has no natural predator in the lake here.
“The ironic thing is that its major enemy would be the shark,” said marine ecologist Joe Ryan, referring to the bull sharks that enter the lake via the San Juan River from the Caribbean. Shark populations, along with sawfish, have dwindled in the last three decades due to heavy over fishing and finning (NT, Feb. 3, 2006).
Ryan, a U.S.-trained marine ecologist living in Granada, co-published a recent article in the academic journal Bioscience arguing that the more tilapia found in any given part of the lake, the less native fish will be found.
Bio-invasion can be the least predictable and most difficult, and thus expensive, environmental disturbance to fix, scientists say.
Eradicating tilapia from Nicaragua would cost millions or even billions, Senna said. “It’s part of the lake’s ecosystem,” he said. “Nobody’s going to eliminate it. They are always going to be there.”
Study: Algae Levels Hurting Lake
Recent findings regarding Lake Cocibolca’s algae make-up suggest a “severe ecological imbalance” that threatens the lake’s biodiversity, says leading marine ecologist Salvador Montenegro.
In all but one of 42 sample points around the lake, UNAN scientists found in a study last year that an invasive form of phytoplankton called Cyanophyta is the dominant algae species. The blue-green Cyanophyta feeds on high nitrogen and phosphorous levels that are a result of farming and ranching fertilizers that are draining into the lake – a flow increased by deforestation.
Not only does the algae tend to behave monopolistically – pushing other species of plankton out of business – but they degrade the aesthetic quality of a lake by producing a foul smell and taste in the water, according to the study. Blue-green algae hogs the oxygen in the water, leaving less to go around for other aquatic life; it produces toxins that can be harmful to aquatic life and make it unfit for human consumption and eventually even human contact, according to the UNAN report.
Montenegro, who has been studying algae trends in the lake for the last 12 years, said other types of “healthy” algae have been steadily dwindling.
“You can tell how ill an environment is by looking at species composition,” he said, “Different algae fuel an ecosystem. If algae mass is toxic, then everything changes in the food chain. Animal numbers are reduced. Whole ecosystems are reduced to simplicity. Many niches go empty,” he said.
Some are skeptical of the conclusiveness of the report, however.
“It’s a little unfair to conclude that bluegreen algae are predominating from one sample. They come and go seasonally.
They’re not present all year,” said Alex Gutiérrez, production manager of the NICANOR tilapia farm on Ometepe Island.