ENVIRONMENTAL-INFLUENCES ON CARDIOVASCULAR VARIABLES IN RAINBOW-TROUT, ONCORHYNCHUS-MYKISS (WALBAUM)

Two groups of wild (lakedwelling and anadromous), and a group of hatchery‐reared Oncorhynchus mykiss (Walbaum) (rainbow trout) were sampled in order to measure cardiac morphometrics, haemoglobin concentration, and the DNA and protein concentration in cardiac muscle. A combination of these variables was used to distinguish wild fish from domestic ones. The wild fish had significantly higher levels of haemoglobin (for male fish, 10.10 and 10.07 g 100 ml−1 vs. 7.69 g d−1) and larger relative ventricle mass (females, 0.091 and 0.099% ofbody mass vs. 0.073%; males, 0.108 and 0.134% vs. 0.102%; immatures, 0.086 and 0.094% vs. 0, 072%, respectively) than the domestic fish. The anadromous and domestic fish had significantly higher amounts of compact tissue when compared with lake fish (females, 43 and 47% of ventricle mass vs. 34%, respectively). Ventricle size distinguished wild fish from domestic fish, except male anadromous and male domestic fish which were distinguished only by haemoglobin and compact tissue values. Immature fishes from all groups had lower total protein levels in the ventricle, lower compact tissue levels, and less haemoglobin. Points regarding the potential environmental influences in determining these cardiovascular trends are discussed. Copyright © 1992, Wiley Blackwell. All rights reserved