Contains a table with the values of eight fish fitness traits. Furthermore, the fish ID number (Fish_ID), the species name (Species), the fish family (Family_ID), the year of dissection (Year), treatment (Treatment) and fish sex (Sex) are given. The fitness traits measured include the length in mm and weight in g of fish, the body condition estimated using the residuals of the linear regression of log10-transformed weight against log10-transformed body length, the head-kidney weight in g, liver weigth in g, the weight of testes in g, the respiratory burst activity and the concetration of sperm motility (number of spermatozoa/µL) (Sperm concentration).