Anesthetic Driven Hematological Dynamics in Farmed Fish: What Do We Know?

Anesthetic agents are widely used in aquaculture to facilitate handling, transport, surgery, vaccination, tagging, and other husbandry procedures. However, most previous reviews have primarily focused on induction time, recovery duration, and welfare outcomes, with comparatively limited emphasis on blood physiology as an indicator of systemic anesthetic safety. The present review synthesizes current evidence regarding hematological, hemato-biochemical, blood gas, and immunohematological alterations induced by major anesthetic classes in aquaculture species. Literature published between 2000 and 2026 was retrieved from Scopus, Web of Science, Google Scholar, PubMed, ScienceDirect, and Springer Nature databases, with approximately 150 studies included following structured screening. Available evidence indicates that anesthetic exposure frequently alters erythrocyte and leukocyte profiles, cortisol secretion, glucose and lactate metabolism, hepatic enzyme activity, electrolyte balance, acid–base regulation, and blood oxygen transport. Respiratory depression, hypercapnia, hypoxemia, and transient metabolic acidosis were recurrent consequences of deep anesthesia, particularly during prolonged exposure or unfavorable environmental conditions. Several anesthetics also modulated innate immune responses through alterations in complement activity, respiratory burst function, cytokine signaling, and leukocyte redistribution. Collectively, the review highlights blood physiology as an essential framework for evaluating anesthetic safety and improving welfare-oriented aquaculture practices.