The effects of acute crude oil exposure on growth and competition in red drum, Sciaenops ocellatus

Highlights: • Oil exposed fish had similar specific growth rates as control fish when resources were abundant, and competition was low • Oil exposed fish had lower specific growth rates weeks after exposure when resources were limited and competition was high • Reduced specific growth rate was accompanied by lower standard metabolic rate Crude oil is a well-known toxicant that reduces cardiorespiratory performance in acutely exposed fishes. While toxic effects can manifest in death in severe cases, the ecological consequences of sub-lethal exposure remain uncertain. This study investigated the impact of crude oil exposure on long-term social competition, growth, and metabolic performance in a coastal species, the red drum (Sciaenops ocellatus). Fish were acutely exposed to either control or one of two environmentally relevant oil concentrations and reared together in groups of 15 (5 from each exposure concentration) for eight weeks under resource-rich or resource-limited scenarios. Relative to controls, a 41.3% and 45.9% reduction in the specific growth rate was-observed following exposure to 25.3 and 53.4 μg l⁻¹ ΣPAH respectively under resource-limited conditions. These fish were subsequently sampled for metabolic performance and common indicators of social subordination including reduced glucocorticoid receptors in the gill and caudal fin damage. The reduction in specific growth rate coincided with a 15.1% and 17.3% reduction in standard metabolic rate; however, maximum metabolic rate and aerobic scope were unaffected. Additionally, measures of social subordination showed no differences between oil-exposed and control fish. These results reinforce the hypothesis that acute oil exposure can have prolonged sub-lethal effects that compromise the ability of exposed individuals to perform effectively in their environment, including gathering and/or metabolizing food. Furthermore, this work highlights the premise that oil spills can be more detrimental in already at-risk ecosystems.