Sex differences in ionoregulatory responses to dietary oil exposure in polar cod

Serum osmolalities and chloride concentrations were examined in polar cod. When exposed to oil male and female fish responded differently. Ingestion of food contaminated with oil led to a significant decrease in osmolality (from 503 to 492 mOsm kg⁻1) in males. There was no significant effect of oil ingestion on serum osmolality in females, but chloride concentrations were increased (from 196 to 203 mmol kg⁻1). Gender related responses should, therefore, be considered when assessing the possible effects of environmental pollutants on fish physiology.