The world\\\'s fastest-expanding industry for producing food is aquaculture. Fish diseases, however, are a significant issue for the industry. The new restrictions on the use of antibiotics and other chemicals in fish due to human and environmental health concerns have made the fight against diseases more challenging. Given the present limitations on the use of antibiotics, consideration of other potential alternatives is imperative. In aquaculture, the use of functional feed additives has the potential to replace antibiotics. Additionally, changes in fish\\\'s hematological parameters are recognized as a general indicator of fish health and these characteristics offer crucial details regarding fish health. Additionally, variations in blood parameters offer hints for a thorough comprehension of pathological and normal processes. This paper provides an in-depth analysis and update of the literature on the hematological effects of various feed additives on fish.

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