We test competing hypotheses from political-economic and neo-liberal theories about the effects of economic growth and urbanization on a neglected, but important, indicator of environmental health: aquatic biodiversity. We analyze cross-national data on the number of threatened fish species within national territorial waters using negative binomial regression. We find that, counter to the expectations of neo-liberal theories, economic growth increases the likelihood of fish species becoming threatened within nations. Urbanization, however, appears to have no additional effect. The "environmental Kuznets curve" does not hold for aquatic biodiversity, suggesting that further economic growth in nations is likely to escalate the biodiversity crisis. (c) 2007 Elsevier Inc. All rights reserved.