Chronic stress of rainbow trout Oncorhynchus mykiss at high altitude: a field study

Multi-Approach Assessment for Stress Evaluation in Rainbow Trout Females, Oncorhynchus mykiss (Walbaum, 1792) from Three Different Farms during the Summer Season

Blood biochemistry parameters are valuable tools for monitoring fish health. Their baseline values are still undefined for a multitude of farmed fish species. In this study, changes in the blood profile of rainbow trout females (Oncorhynchus mykiss) from three farms were investigated using different biomarkers during the summer season. In the given context, the main water physicochemical parameters were investigated and twelve biochemical parameters were measured from blood samples of rainbow trout reared in the Fiad, Șoimul de Jos, and Strâmba farms. We selected these farms because the genetic background of the rainbow trout is the same, with all studied specimens coming from the Fiad farm, which has an incubation station. Forty-five samples were collected monthly (May to August) throughout summer to observe the changes in the blood profile of rainbow trout. Principal component analysis showed a clear separation both among the studied farms and months. Furthermore, significant correlations (p < 0.05) between the majority of the biochemical parameters were found, indicating that the environmental parameters can influence several blood parameters at the same time. The present study provides several useful norms for assessing the welfare of rainbow trout, indicating that the relationships among different parameters are important factors in interpreting the blood biochemical profiles.

Fish biomarker responses to perturbation by drought in streams

ABSTRACT Drought can be viewd as a perturbation in running waters and fish are often trapped in isolated pools, where deterioration of water quality may be stressful. We investigated how this extreme condition influences response of oxidative stress biomarkers. The response of the characid Astyanax elachylepis was assessed during the dry and rainy seasons in intermittent and perennial (control) sites in streams from Brazilian savannah (Cerrado). We predicted that the biomarkers would be enhanced in the dry season in intermittent streams only due the environmentally harsh conditions in the few isolated pools that remain filled with water. As predicted, fish from the intermittent stream in the dry season presented higher gill MDA values, indicating greater stress. In the liver, MDA values were higher in the dry season for both intermittent and perennial streams, suggesting a generalized seasonal response. As expected, some antioxidant response enzymes changed in the intermittent sites during the dry season. Therefore, oxidative stress biomarkers vary seasonally, with greater increase in intermittent sites. These evidences contribute for the understanding of the spatio-temporal variation of the fish responses and fish resistance to perturbations by drought in tropical environments.