Fish skin for water quality assessment

Pollution and the resulting decline in water quality pose a serious issue for aquatic biodiversity. Therefore, biomonitoring strategies to assess water quality need to be improved. In this study, we evaluated the possible use of fish skin histology as biomarker to monitor the water quality. Five fish species (Salmo trutta, Anguilla anguilla, Leuciscus cephalus, Barbus barbus and Rutilus rubilio) were collected from 32 river sites in the Campania region (Southern Italy), located within/outside Natura 2000 network. Body Condition Factor (BCF), Epidermis Morphological Index (EMI), Mucous Cell Index (MCI), epidermis thickness, and mucous cell size were analyzed in relation to the river site Ecological Quality Class (EQC). Negative correlation between BCF and EQC was found for S. trutta and A. anguilla, while a positive correlation was observed for L. cephalus and B. barbus. Skin histological results highlighted positive correlation between EMI and EQC in S. trutta, A. anguilla, and R. rubilio, while positive correlation between MCI and EQC was observed in S. trutta, L. cephalus, B. barbus, and R. rubilio. Epidermis thickness was negatively correlated with EQC in S. trutta, L. cephalus, and B. barbus, and positively correlated in A. anguilla. Mucous cells size appeared negatively correlated with EQC in L. cephalus and R. rubilio and positively correlated in A. anguilla. The findings of this study indicate that skin histology could be a sensitive and useful biomarker to assess water quality, suggesting its integration in biomonitoring programs. Species-specific responses need to be considered to obtain a more reliable water quality assessment.