This article presents an automatic system for assessing water quality based on fish gills microscopic images. As fish gills are a
good biomarker for assessing water quality, the proposed system uses fish gills microscopic images in order to detect water
pollution. The proposed system consists of three phases; namely pre-processing, feature extraction, and classification phases.
Since the shape is the main characteristic of fish gills microscopic images, the proposed system uses shape feature based on edge
detection and wavelets transform for classifying the water-quality degree. Furthermore, it implemented Principal Components
Analysis (PCA) along with Support Vector Machines (SVMs) algorithms for feature extraction and water quality degree
classification. The datasets used for experiments were constructed based on real sample images for fish gills. Training dataset is
divided into four classes representing the different histopathological changes and the corresponding water quality degrees.
Experimental results showed that the proposed classification system has obtained water quality classification accuracy of
95.41%, using the SVMs linear kernel function and 10-fold cross validation with 37 images per class for training.