Freshwater fish faunas, habitats and conservation challenges in the Caribbean river basins of north-western South America.

The remarkable fish diversity in the Caribbean rivers of north-western South America evolved under the influences of the dramatic environmental changes of neogene northern South America, including the Quechua Orogeny and Pleistocene climate oscillations. Although this region is not the richest in South America, endemism is very high. Fish assemblage structure is unique to each of the four aquatic systems identified (rivers, streams, floodplain lakes and reservoirs) and community dynamics are highly synchronized with the mono-modal or bi-modal flooding pulse of the rainy seasons. The highly seasonal multispecies fishery is based on migratory species. Freshwater fish conservation is a challenge for Colombian environmental institutions because the Caribbean trans-Andean basins are the focus of the economic development of Colombian society, so management measures must be directed to protect aquatic habitat and their connectivity. These two management strategies are the only way for helping fish species conservation and sustainable fisheries.

Potamodromous migrations in the Magdalena River basin: bimodal reproductive patterns in neotropical rivers.

Magdalena River basin potamodromous fishes have two annual reproductive seasons: the subienda in the first half of the year and the mitaca in the second. Both upstream migrations are c. 30-45 days long; after that, with the onset of the rainy season, fishes spawn and remain in the river (resident individuals) or start a downstream movement (the bajanza) to return to the Magdalena floodplain lakes (nursery, shelter and feeding grounds). Due to their particular gonad development the bocachico Prochilodus magdalenae and probably the comelón Leporinus muyscorum are physiologically able to undertake two annual basin migrations. In the presence of dams or hydropower structures, fishes are able to find alternative migration routes. Some species should be re-classified in their migratory behaviour.