Effects of environmental factors on reproductive seasonality of Magdalena River basin fish: need for answers in the ecophysiology

Magdalena River basin is the core of development and economy of Colombia, with about 80% o f the country's population (32 million) depending on it. This basin is drained by the Magdalena River and 3 main tributary rivers: Cauca, Sogamoso, and San Jorge, covering an area of 257 438 km (nearly a quarter ofColombia's territory) (GALVIS & MoncA 2007). According to its geomorphologic features, this basin has been divided in 3 main sectors: Upper, Middle, and Lower. Flood plain areas appear in Middle basin and grow in the Lower. The number o f fish species reported for this basin i s 167, some migratory and important for artisanal fisheries. Although fishery captures were nearly 80 000 tons in the 1970s, only one-fifth that amount is produced now (GALVIS & MoncA 2007). Studies on reproductive biology ofMagdalena River basin fishes are crucial for fisheries management and environmental protection programs. Based on some information on environmental factors and fish reproduction from different places in Magdalena River, we list some possible physiological pathways induced by environmental cues and recommend some experimental approaches that would help clarify such relationships.