This project investigates the adaptability and specificity of antibodies in estuarine fish, focusing on how their immune systems respond to the unique environmental challenges of fluctuating salinity, temperature, and diverse pathogens. Key objectives include analyzing how estuarine fish adjust antibody production to rapidly counter pathogens, identifying different antibody types (IgM, IgD, IgT/Z) and their roles in targeting specific threats, and exploring genetic diversity and evolutionary adaptations in immune genes. The study also examines the impact of immune responses on fish health and ecosystem resilience, with practical implications for conservation and sustainable aquaculture practices. Findings will offer valuable insights into supporting the immune resilience of fish in dynamic, sometimes stressed, estuarine environments.