Long‐term changes in the fish assemblage of the Laja River, Guanajuato, central Mexico

摘要: 1. The structure and composition of fish communities in rivers central Mexico have been altered as a result water over-exploitation, habitat fragmentation, introduction exotic species, pollution. However, the specific pattern degree change are poorly documented. 2. Long-term information from Laja River (Guanajuato, Mexico) Lerma basin was used to explore trends species richness community (species origin, trophic niche, tolerance, preferred habitat) 1960s present both river reservoir sites. 3. Declines native, sensitive, benthic native carnivore ranging 11% 30% per decade, increases number tolerant by 9–20% documented. Repeated measures ANOVA sign tests revealed significant declines benthic, sensitive species. Species richness, exotics, omnivore did not statistically, though statistical power low. Some important changes occurred these variables, such expansion establishment exotics Xiphophorus variatus Micropterus salmoides, which pose serious potential threat species. 4. The for portray how other Mexico, long-term data do exist, changed or could if environmental deterioration continues. Copyright © 2006 John Wiley & Sons, Ltd.