River-Dredging Could Impact Sportfishing

November 17, 2010

RIO SAN JUAN – The Sandinista government’s efforts to dredge the last 22 kilometers of the Río San Juan could have a serious impact on the local sportfishing industry, according to local fisherman.

In the 1950s, Costa Rica dredged the Río Colorado, diverting the strength of water flow from Nicaragua’s Río San Juan into Costa Rican territory. As a result, the final stretch of the Río San Juan has clogged with silt over the years, drying it to a trickle during the summer months.

“In the summer, the bigger fish – the 60 to 80 kilo tarpon – can’t pass many parts of the San Juan River,” said Yaro Ch-Praslin of the Sabalos Lodge, 20 kms downriver from San Carlos. “That’s especially true for the larger pregnant fish. So they are nesting in the Río Colorado.”

The deeper waters of the Río Colorado, meanwhile, provide a natural channel for fish migrating from the San Juan River to the lagoons and sea.

Not coincidently, Costa Rica has developed a thriving sportfishing industry at the mouth of the Río Colorado, while Nicaragua’s smaller sportfishing industry is limited to upriver action on the Río San Juan.

But once Nicaragua finishes dredging the Río San Juan and reestablishes the historic flow of its delta, the fish will suddenly have residency options. And Nicaraguan waters might start to appear a lot more attractive – both to the tarpon and also to investors.

Some fisherman predict that when Nicaragua cleans the mouth of the San Juan, more fish will again start entering the river and Lake Cocibolca, and the volume of fish in the Colorado will become more disperse.

“I think this will have a negative effect on Costa Rica’s sportfishing, without a doubt,” Ch-Praslin said. “The fish will have another route.”

On the Costa Rican side, however, there is concern that dredging operation will destroy delicate fish-nesting sites, potentially harming the fishing industry for everyone.

“My main concern is that the marshes and lagoons in the area are nursing areas for baby tarpon and if [the Nicaraguan government] starts to dredge that rivermouth, the river will flood that saltwater marsh and destroy the breeding grounds of the saltwater fish,” said Dan Wise, owner of the Río Colorado Lodge.

Wise added, “Currently, the marshes around the river mouth of the Río San Juan stay salty because the curves of Río San Juan keep the water flowing slowly. If they dredge the river and open up the flow, it could potentially change all fish breeding that is happening in the area.”

Since many tarpon are thought to live 30 to 50 years, the impact on sportfishing might not be felt immediately. But if nesting sites are eradicated, there will be a long-term effect since it’s believed the fish return to their birthplace to spawn later in life.

There is also concern about what the dredging might mean for other fish-nesting sites, as well as the populations of guapote, corvina and snook that provide a key food source in the subsistence diets of the people who live along the banks of the river.

The dredging, according to RoseAnne Cody, general manager of the nearby Silver King Lodge, could “destroy the tarpon fishing industry and the livelihoods of many of the people in the village.”

“We will see what this Spring brings,” she said.

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