00000ctm a22000004a 4500 UP-8027390931313939625 Buklod 20150824093037.0 m |o d | ta 150824s2015 xx d r |||| u| (iLib)UPVIS-00038539473 LG 995 2015 F5 J86 Jumah, Yashier Upling Influence of salinity and stocking density on the stress response of Nile tilapia Oreochromis niloticus Linnaeus, 1758 by Yashier U. Jumah. Miagao, Iloilo University of the Philippines Visayas 2015. 151 leaves Thesis (M. S. Fisheries-Aquaculture) -- Miagao, Iloilo : U. P. in the Visayas, May 2015. Tilapia culture in less saline environment is a new development intended to expand the production of this commercially important fish species. This culture system is at its infancy stage and several factors affected the favorable tilapia productions are needed to be elucidated. Thus, a study was conducted to investigate the physiological stress responses of Nile tilapia Oreochromis niloticus exposed in brackish and seawater conditions. A 2 x 3 factorial experiment in completely randomized design (CRD) were conducted to assess the influence of salinity and density on the physiological response of Nile tilapia. Results revealed salinity or stocking density independently throughout the experiment. Initially, blood glucose was significantly higher at elevated salinity while increased plasma cortisol and decreased percentage survival were caused by synergistic effect of both stressors. During the second sampling, percentage survival has consistently decreased in higher salinity until the end of the end of the study while plasma cortisol and aspartate transaminase (AST) had significantly increased at higher salinity and stocking density until the third sampling period. However, interaction effect of both factors caused higher AST values on the last sampling. Blood glucose and plasma alanine transaminase (ALT) were both influenced by the interaction of salinity and density. During third sampling, higher blood glucose was observed at increasing stocking densities. At this point, chloride cells size and density were continuously regulated with increasing salinity. Synergisticc effects of both factors on Na+/K+- -ATPase (NKA) were imminent on the third and last sampling period. Also, elevated plasma ALT was significant in interaction on the third sampling but later responded to stocking density. Thus tilapia reared at lower salinity (15%) is less stressful as compared to higher salinity (30%0) while decreasing stress level was observed towards lower stocking density. This manifests that salinity and stocking density caused stress to the tilapia despite of their being hardy in nature. However based on the results, interaction of lower salinity and stocking density condition promotes better survival and improves the overall physiological condition of fish against stress. Nile Tilapia. Salinity and stocking density. UPVIS UPV-CFOS LG 995 2015 F5 J86 UPVIS UPV-GL LG 995 2015 F5 J86 Thesis