Sample sites location of Dorosoma anale and D. petenense in the Grijalva and Usumacinta basins: 1 = Lacantún River, 2 = Lacanjá River, 3 = San Leandro Lagoon, 4 = Miramar Lagoon, 5 = Canitzán Lagoon, 6 = Chacamax River, 7 = Nueva Esperanza Lagoon, 8 = San Pedro River, 9 = Usumacinta River, 10 = San Isidro Lagoon, 11 = Pom Lagoon, 12 = Palancares Lagoon, 13 = Vapor Lagoon, 14 = Boca Chica estuary, 15 = Malpaso dam, 16 = Chicoasén dam, 17 = Peñitas dam, 18 = Tzendales River. Black triangles indicate the dams.