On Jan. 8, a magnitude 6.2 earthquake hit an area in Costa Rica near the volcano Poas. Assistant professor for the department of biological sciences Ronald M. Coleman was staying there, at the La Selva field station, between the Puerto Viejo and Sarapiqui rivers.

Coleman was in Costa Rica to study the fish in the river when the quake hit. He has been studying cichlid fish and their reproductive cycle off and on since 1989 and continuously since 1996.

Coleman explained that most tropical biologists work in that part of Costa Rica because it is where the Puerto Viejo and Sarapiqui rivers come together; at the base of a central mountain range.

It is not unusual for this area to experience earthquakes, since this part of the world is considered an active seismic zone, where plates located under the ground often shift and touch.

That day, however, was unusual. The Sarapiqui River, which is about the size of the American River, filled with mud shortly after the quake hit, solidifying the river. It stopped the flow of the water and killed all the fish.

“When the mud hit the water, it was like adding a bag of flour to a bowl of water,” Coleman said.

It appears that all of the oxygen was sucked out of the river, leaving the fauna, which are small tropical insects that live on the bottom of the river, and the fish to die, said Coleman.

When the Costa Ricans went to him to ask when and how the fish population would return to normal, Coleman explained that it would take years for the fish to repopulate. He will be going back to Costa Rica again this June to do further research.

Sally King can be reached at [email protected]