Fish hematology analysis as an important tool of aquaculture: A review

Aquaculture is the fastest-growing food-production sector in the world. Aquaculture supplies 50% of all fish consumed globally today, and it is predicted that by 2030 it will be the prime source of fish. The use and validation of fish health monitoring tools have become increasingly evident due to the expansion of aquaculture. The complete blood cell count (CBC) is an important and powerful diagnostic tool as well as a component of a minimum database. It can be used to monitor the health status of fish in response to changes related to nutrition, water quality and disease an in response to therapy. The assessment of blood parameters in fish has thus far been performed manually, using a Neubauer and Burker haemocytometer, because the automatic techniques used for mammals are generally not applicable for fishes (because of the presence of nucleated erythrocytes). Manual blood count has multiple sources of error (such as inadequate mixing or dilution of blood and stains and incorrect charging of the haemocytometer chamber), which can lead to misinterpretation of the blood cell count. Automatic blood cell count has been performed in fish, but only few researchers have described this specific method. Automated instruments offer a major economic advantage because of their savings in labor costs and because of their speed, which is frequently significantly greater than that of manual devices. Automatic analyzers for blood cells of fish can usually produce more reproducible results over a long period than can an operator employing a manual instrument and, therefore, can help optimize the early diagnosis of a disorder. They enable the appropriately-timed treatment of fish and greatly improve efficiency of applied therapy. Automated analysis methods for the assessment of hematological parameters, as an alternative to manual methods, are a valid diagnostic aid for the future of aquaculture.