LAUSR

This study characterised selected peripheral blood (PB) haematological parameters, liver, serum and muscle metabolic features in three- and five-year old male and female giant kokopu (Galaxias argenteus) broodstock reared indoor at 16°C. Sex and age did not affect PB total cell count, and haematocrit values. However, higher erythrocytes in five-year old fish, elevated thrombocyte and lymphocyte counts in three-year old fish indicate age-specific cellular regulation. Higher thrombocyte counts in female fish suggest sex-specific regulation. At a metabolic level, liver abundance for long chain saturated fatty acids were higher in males, while females had elevated levels of polyunsaturated fatty acids. Essential and non-essential amino acids in liver and serum were also elevated in females compared to males. These findings suggest differential allocation of fatty acids and amino acids to reflect requirements for gonadal, development and provisioning. Similarly, age significantly resulted in higher liver and serum abundances of some non-essential amino acids in three-year olds compared to five-year old fish, suggesting higher metabolism in younger fish. Overall, results enhance our understanding of sex- and age-based differences in fish haematology, muscle, liver, and serum metabolite profiles in healthy G. argenteus. Future studies should carefully consider potential age- and sex-specific differences in metabolic responses. This article is protected by copyright. All rights reserved.