Underwatertimes.com News Service - January 18, 2006 00:00 EST

Nicaragua banned freshwater fishing of bull sharks and sawfish on Tuesday because of alarming population declines, and said it wants neighboring Costa Rica to impose a similar prohibition.

Overfishing in the San Juan River that forms much of the border with Costa Rica has reduced the number of both marine animals to dangerously low levels, Nicaraguan agriculture officials said.

The Nicaraguan ban on harvesting of the two types of fish, which can survive in both salt and fresh water, applies in the river and in its massive Lake Cocibolca.

Sawfish, named for their long snouts lined with sharp teeth, and the sometimes aggressive bull sharks enter the San Juan River in the Caribbean and swim upriver to Nicaragua's Lake Cocibolca, which covers more than 8,000 square kilometers (3,000 square miles).

"Costa Rican fishermen have nets and a series of traps that impede the traditional migration toward the (Cocibolca)," said Miguel Marenco, head of Nicaragua's agriculture department.

Bull sharks, which have also been found in the Amazon and Mississippi Rivers, attack people more often than other do sharks because they tend to frequent shallow waters.

In recent years, Costa Rica and Nicaragua have traded barbs over the San Juan River, which runs for almost 200 km (124 miles) from Lake Cocibolca to the Caribbean.

"We have taken up this migration problem of both of these species with our colleagues in Costa Rica," Marenco said.

Last September, Nicaragua recalled its ambassador to Costa Rica, after Costa Rica filed papers with the International Court of Justice in The Hague to fight for unlimited navigation rights on part of the San Juan River.