The tropical zone contains the highest diversity of fish species on the planet. Many of these species are being continuously exposed to pollutants that pose serious hazards to fish health thereby posing serious risks for entire fish populations. This book presents information about the different responses of fish to pollutants from the molecular levels to changes in behaviour, with emphasis on tropical species. It also discusses current topics such as the adverse effects of emerging compounds like nanoparticles and endocrine disruptor chemicals.