Migración de la sardina Astyanax fasciatus (Characidae) en el río Tempisque, Guanacaste, Costa Rica

Resumen

Massive migration of Astyanax fasciatus in the Rio Tempisque, Costa Rica, is reported roc the first time. Upstream movements begin about two weeks after the end of the rainy season, and continue for approximately one month. Observations were made in the Rio Tempisque proper, but the phenomenon also occurs in several rivers on the Nicoya Peninsula. Migratory individuals were young, with undeveloped gonads. Population pressure and a consequent increase in competition roc road due to the reduction of aquatic habitat is proposed as the cause for migration.