Probing the exposure to environmental stress using fluctuating asymmetry of metric traits in Johnius vogleri, (Bleeker, 1853) from lower Agusan River basin, Butuan City, Agusan del Norte, Philippines.
Fluctuating asymmetry (FA) was used to determine the possible effects on the morphological symmetry of Johnius vogleri sampled in lower Agusan river basin. The river as an aquatic system was known to be contaminated with bacteria and heavy metals. Numerous studies have demonstrated that FA can be used to assess the fish morphology exposed in various environmental conditions. However, no similar study was conducted in the area nor any assessment on fish conditions. There were a total of 100 samples collected (50 males and 50 females) Digital imaging was done and the captured images were loaded into tpsDig2 program. Standard landmarks on fish morphometrics were applied. Using thin plate spline (TPS) series, landmark analysis were attained and subjected to symmetry and asymmetry in geometric data (SAGE) software. Results in Procrustes ANOVA revealed that the factors as individuals, sides and interaction of individuals and sides showed highly significant differences (P<0.0001* Similar results were observed to both male and female samples indicating FA of J. vogleri in lower Agusan river basin. The asymmetry in the morphology of the fish indicated exposure to environmental stress. Asymmetrical appearance was the manifestation in buffering environmental disturbance. Principal component analysis on the symmetry and asymmetry scores was applied to determine the affected landmarks. Ordination of the resulting data was displayed in deformation grids and histograms to both female and male samples. In females, affected landmarks were portion of the head and fins. In males, affected landmarks were largely from the head and caudal fin. The result of the study is highly important in future management actions of lower Agusan river basin.