Spatial variations of the water quality parameters of the Merbok estuary were interpreted by multivariate statistical techniques, such as cluster analysis (CA), principal component analysis (PCA), and factor analysis (FA). Data from January to December 2011 were collected to monitor 13 parameters at six sampling stations along the river stretch (two stations at each river section: upstream, midstream, and downstream). Cluster analysis results revealed two different groups between the sampling stations, reflecting different physicochemical properties and pollution levels in the study area. Factor analysis was used for the parameters of the surface and bottom water quality, yielding four factors that were responsible for 72.93 and 68.90 % of the total variance of data sets. PCA also found conductivity, salinity, dissolved oxygen, chlorophyll a, and NO 3 -to be the most important parameters contributing to the fluctuations of surface water and bottom water quality in the Merbok estuary. This study presents the usefulness of multivariate statistical techniques for assessing water quality data sets and for understanding spatial variations in water quality parameters to effectively manage water quality in estuaries.

The present study was conducted to identify the type of food taken by mullet fish. To study the food and feeding habits, a total of 80 fish samples were collected from upper zone of Merbok estuary. Two methods were followed, namely occurrence and numerical for the analysis of gut contents. The observation identified algae, diatoms, desmids, plant materials, annelids, crustaceans, fishes, detritus and sand grains as major food items. Plant materials were the most abundant food items by numerical and occurrence methods in the gut of both fish species.

This study was carried out to observe effects of tidal events on the water quality parameters at Merbok estuary, Kedah, Malaysia. Twenty four hours sampling were conducted at Station 1, 2 and 3 from 12 th November (spring tide) to 3 rd December (neap tide) 2011 on weekly interval. Results showed that water quality parameters varied with the following ranges: temperature (26.10 -30.7°C), pH (6.29 -7.22), dissolved oxygen (0.65 -5.48 mgL -1 ), salinity (0.50 -35PSU), nitrate (0.037 -0.647mgL -1 ), nitrite (0.09 -0.36 mgL -1 ), ammonia -N (0.03 -3.05 mgL -1 ), phosphate (0.03 -0.10mgL -1 ). Kruskal Wallis H test showed that water quality parameters were significantly different among sampling stations (p<0.01). Mann-Whitney U test result showed that water quality parameters were significantly different between spring and neap tides (p<0.01) except temperature and nitrate. Parameters such as temperature, salinity, nitrate, ammonia -N and phosphate recorded higher in spring tide while, DO, pH and nitrite were higher in neap tide.

The importance of terrestrial insects as food items for freshwater fish was studied by examining stomach contents of Devario regina (Fowler 1934)

This study was conducted in Merbok estuary, Kedah, Malaysia during January to December 2011 to assess monthly and seasonal variation in food items in the stomach of Chelon subviridis and Valamugil buchanani. A total of 341 fish samples (225 for Chelon subviridis and 116 for Valamugil buchanani) were collected from upper zone (Lalang and Sameling Rivers) of Merbok estuary. Among the stomach contents plant materials, diatom, cyanobacteria and detritus were the main food items in both fish species. In both fishes the highest numbers of food items were found in the month of November. Chelon subviridis consumed plant materials 65.84% by number and 8.55% by frequency of occurrence in the dry season whereas 66.25% by number and 9.73% by frequency of occurrence in the wet season. On the other hand, Valamugil buchanani consumed plant materials 59.54% by number and 12.28% by frequency of occurrence in the dry season whereas 72.89% by number and 11.96% by frequency of occurrence in the wet season respectively. Monthly variations of diatom as food item between C. subviridis and V. buchanani were found to be statistically significant (p<0.05). Both of the fish species consumed more food (by numerical method) in wet season than dry season.