Blood Biochemical Biomarkers in Fish Toxicology—A Review

Blood-based biochemical assays are used as predictive and diagnostic methods to evaluate fish welfare in aquaculture and research. The variations of blood biochemical parameters in fish are commonly used as biomarkers of exposure to toxic agents. Blood biochemical parameters can help identify the magnitude of toxicity and the mechanisms by which particular toxic agents act on the organisms. Some parameters typically measured in the blood can also be evaluated in the whole body in the early developmental stages of fish (embryos and larvae) that are often used in toxicological studies. This review assessed the usefulness of various blood biochemical indices as toxicity biomarkers. Analysis of multiple studies showed that toxicity-induced changes in most blood biochemical parameters in fish often depend on toxic agent concentration and exposure duration. Also, various parameters manifest different sensitivity to intoxication, and diverse directions of changes may occur. Among biochemical parameters, some are biomarkers of general physiological stress, while others indicate dysfunctions of particular organs. Moreover, hormonal endpoints seem to be sensitive but nonspecific biomarkers of intoxication in fish.