Morphological and behavioral responses of female red tilapia (Oreochromis sp.) exposed to different salinity concentrations [manuscript]
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Date
2018
Authors
Princess Joy P. Santacera
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Abstract
The study evaluated the morphologcal and behavioral response of female red tilapia (Oreochromis sp.) exposed to different salinity concentrations. The objective of the study was to determine if ECP and VR can be an effective stress indicators in juvenile stage of female red tilapia exposed to different salinity concentrations. Also the salinity tolerance of female red tilapia was assessed. Juvenile female red tilapia of size 12 were used in the study. The salinity concentration was gradually raised every hour (within 8 hours) until they reached their respective levels and monitored 24 hours. The salinity concentrations used were 0 (Control), 5 ppt, 10 ppt, 15 ppt, 20 ppt and 25 ppt. Mean ECP at 5 ppt (2.28±0.61) and 10 ppt (2.01±0.24) were comparable but both were significantly higher compared to those in the other treatments. The mean ECP at 0 ppt (1.95±0.30) and 20 ppt (1.95±0.12) were also comparable but both were significantly higher than those at 25 ppt (1.90±0.06) and 15 ppt (1.55±0.16). The latter two means were not significantly different from each other. There exist an insignificant weak negative relationship between mean ECP and salinity concentration (r=-0.388;n=6;P<0.05). Mean VR at 10 ppt (1.47±0.05) and 0 ppt (1.46±0.05) were comparable but both were significantly higher compared to those in the other treatments. The mean VR at 5 ppt (1.42±0.57) and 15 ppt (1.42±0.05) and 0 ppt (1.46±0.05) were comparable but both were significantly higher compared to those in the other treatments. The mean VR at 5 ppt (1.42±0.57) and 15 ppt (1.42±0.05) were also comparable but both were significantly higher than those at 25 ppt (1.37±0.03) and 20 ppt (1.37±0.06). The latter two means were not significantly different from each other. There exist is significant weak negative relationship between the mean VR and salinity concentration (r=-0.815; n=6; P<0.05). The mortality recorded were from 20 and 25 ppt salinity level concentrations. In the first eight hours, 25 ppt treatment had recorded one fish died on the seventh hour in replicate 3 and another one died on the eight hour in replicate 4. While on the twenty-fourth (24th) hours, two fish died on replicates 3 and 4 on the 20 ppt treatment and another two fish died on replicates 1 and 2 of the 25 ppt treatment. Another one has been recorded on the thirty-sixth (36th) hour - in replicate 5 of 25 ppt treatment. And the last recorded was on the study forty-eight (48th) hour - in replicate 1 of the 20 ppt treatment. Results of the study indicate that ECP and VR are not reliable tools for the assessment of stress in red tilapia exposed to different salinity levels because of varying results. However, gradual increase of salinity concentration up to 15 ppt can be tolerated by the fish.