Tissue and plasma enzyme activities and chemical analytes in golden trevally Gnathanodon speciosus (Forsskål, 1775) from a public aquarium.

Veterinary care of aquatic species, particularly fish, is limited by a lack of knowledge regarding their unique physiology. Tissue enzyme activities measured in plasma are used for assessing function and potential damage to specific organs and tracking disease progression in live animals. The objective of this study was to identify tissue(s) of origin and plasma concentrations for specific enzymes in healthy golden trevally (Gnathanodon speciosus). We hypothesized enzymes would exhibit tissue specific tropisms with higher activities in one or more tissues compared to others. Six fish were randomly selected from a public aquarium population to obtain antemortem blood samples. The fish were then euthanized and tissue samples were collected via gross necropsy. Six enzyme activities and two chemical analytes were examined across samples of plasma and ten tissues from each fish. Enzyme activities exhibited significant organ specificities. Aspartate aminotransferase, lactate dehydrogenase, and creatine kinase levels were highest in skeletal muscle with variably high levels in gonads. Alkaline phosphatase levels were highest in the kidney, spleen, and liver. Alanine aminotransferase levels had high specificity for the liver. Gamma-glutamyltransferase was only detectable in the kidney and plasma. This work establishes baseline tissue enzyme origins for golden trevally, which will aid clinicians in diagnostic interpretation of blood chemistries and improve veterinary care for this understudied fish species.