Chronic Sub-lethal Effects Observed in Wild-Caught Fishes Following Two Major Oil Spills in the Gulf of Mexico: \u3cem\u3eDeepwater Horizon\u3c/em\u3e and Ixtoc 1

During and subsequent to major oil spill events, considerable attention focuses on charismatic and economic megafauna – and especially fishes – and visual manifestations of impacts upon them. Beginning with a series of tanker accidents occurring in Europe and the USA in the 1970s–1990s, greater awareness of the potential for both acute and chronic sub-lethal impacts on fish populations has focused on exposure to polycyclic aromatic hydrocarbons (PAHs). The ambiguity of acute impacts observed during the Deepwater Horizon and Ixtoc 1 incidents has promoted considerable new research on alternative toxic endpoints that portend short- and long-term sub-lethal outcomes that influence the overall fitness of exposed populations. Laboratory-based exposure studies have traditionally focused on acute mortality-based endpoints (e.g., lethal concentrations at which 50% of the population dies = LC50) and observed at test concentrations normally exceeding environmentally relevant concentrations in real-world spills. Consequently, using laboratory-based toxicity experiments can be problematic inferring impacts on wild fish populations. In this chapter we review historical and more recent information documenting changes in abundance, recruitment, habitat use, population dynamics, trophic changes, and various physiologically based sub-lethal effects on oil-exposed fishes and especially consider research undertaken following the Deepwater Horizon and Ixtoc 1 spills in the Gulf of Mexico