Sampling locations the extent of the lake and

2. Methods
2.1. Study Site
Fig. 1. Research site location. The map to the left indicates the approximate location in Mexico where the work was conducted. The detail map on the right of the Lake Zapotlán Basin shows physiographic features, and the sampling locations for sediments, surface waters, wastewater treatment plants, runoff, and wastewater.Figure optionsDownload full-size imageDownload as PowerPoint slide
The lake supports CAY10650 local fishing economy for African tilapia (Oreochromis spp.) and the Asian common carp (C. carpio). Both species were introduced to Mexico in the 1960–80s as an inexpensive source of protein ( Fitzsimmons, 2000 and Tapia and Zambrano, 2003). Tilapia and carp fished from Lake Zapotlán are sold locally and regionally in Guadalajara, Michoacán, Toluca, and Puebla states. Tilapia and carp make up an estimated 68% and 32% of the total catch respectively ( Ortiz-Jiménez et al., 2005).
2.2. Sampling and analyses