The ecology and life history of the Mexican tetra, Astyanax mexicanus, (Teleostei: Characidae) in the lower Rio Grande Valley, Texas

The Mexican tetra has been found to migrate from shallow waters in the spring and summer months into deeper waters during the winter months when temperatures are too cold for their survival. This fish is omnivorous with insect material being the major source of food. Its food types include green algae, nematoceran larvae, hemipterans, coleopterans, hymenopterans, dipterans, ostracods, fish eggs and amphipods. Furthermore, size classes showed that the Mexican tetras reached their largest size at the River site and smaller sizes at the Bridge and Gate sites and apparently breed year round. They are capable of producing from 300 to just over 7000 eggs per female. The diameter of Mexican tetra eggs range in size from 0.5mm to 1.0mm, and the mean egg size was found to be 0.7mm $\pm$ 0.11mm. In addition, analysis of the relative abundances at the tree sites showed the Mexican tetra to have an overall ranking of six at the Gate site, two at the Bridge site and eight at the River site