Growth and immune system performance to assess the effect of dispersed oil on juvenile sea bass (Dicentrarchus labrax)

•To assess the impact on a commercially important species, sea bass (Dicentrarchus labrax), of crude oil dispersed mechanically and chemically.•To focus on two integrative parameters: growth and the immune system.•At the end of experimentation, growth and immunity performances were not affected by the chemically or mechanically dispersed oil.

The potential impact of chemically and mechanically dispersed oil was assessed in a model fish of European coastal waters, the sea bass Dicentrarchus labrax. Juvenile sea bass were exposed for 48 h to dispersed oil (mechanically and chemically) or dispersants alone. The impact of these exposure conditions was assessed using growth and immunity. The increase observed in polycyclic aromatic hydrocarbon metabolites in bile indicated oil contamination in the fish exposed to chemical and mechanical dispersion of oil without any significant difference between these two groups. After 28 days of exposure, no significant differences were observed in specific growth rate,apparent food conversion efficiency and daily feeding). Following the oil exposure, fish immunity was assessed by a challenge with Viral Nervous Necrosis Virus (VNNV). Fish mortality was observed over a 42 day period. After 12 days post-infection, cumulative mortality was significantly different between the control group (16% p≤0.05) and the group exposed to chemical dispersion of oil (30% p≤0.05). However, at the end of the experiment, no significant difference was recorded in cumulative mortality or in VNNV antibodies secreted in fish in responses to the treatments. These data suggested that in our experimental condition, following the oil exposure, sea bass growth was not affected whereas an impact on immunity was observed during the first days. However, this effect on the immune system did not persist over time.