Comparing blood biochemistry and haematology normal ranges of Chinook salmon (Oncorhynchus tshawytscha) from different production systems

Blood biochemistry and haematological parameters are an integral part of evaluating the health status of fish. Accordingly, these parameters are useful indicators of fish health, welfare and nutritional status. This study examines 33 blood biochemistry and haematological parameters to compare presumed healthy Chinook salmon, Oncorhynchus tshawytscha , reared in commercial pens with research fish reared under controlled conditions in a land based recirculating aquaculture system (RAS). This study also examines the influence of weight and environmental factors, including water type (freshwater and seawater), on these parameters. Significant differences between the aquaculture rearing systems were found for the majority of the parameters, for example triglyceride, cholesterol, and alanine aminotransferase. Subsequently, reference ranges for the parameters were calculated separately for each rearing system. These differences were most likely due to the different stressors experienced by the fish in the open water farms versus the RAS research tanks, particularly the single handling of each on-farm fish versus the cumulative effect of multiple handlings on the trial fish prior to sampling. Significant differences were also identified for the other environmental factors examined. The parameters that exhibited the most significant differences or interactions were calcium, creatinine, and glucose. The parameters that exhibited the least significant differences or interactions were lipase, lactate, and monocytes. The results show that with many significant differences and interactions, it is more appropriate to use multiple reference intervals rather than a single reference interval that does not consider environmental factors, especially for the factors to which the parameters were most sensitive. Careful interpretation is needed in terms of the history of a given fish to provide accurate assessment of blood biomarker values. • Significant differences between on-farm and research trial healthy Chinook salmon. • The calculation of healthy reference ranges for each rearing system separately. • The results show that multiple blood parameter reference intervals should be used. • Identifies parameters less useful diagnostically due to environmental sensitivity.