Method for Analyzing Fish Assemblage Distribution with Application to Fishery Landings of Tropical Shallow Lake as Songkhla Lake, Thailand

<span style="font-size: 10pt; font-family: ">Fish community structure can provide potentially powerful tools for assessing aquatic environmental health. Monthly catch weights in Songkhla Lake were recorded over the period January 2003 to December 2006 inclusive for each of 127 species: 72 were marine vertebrate; 22 freshwater vertebrate; 21 marine invertebrate; 10 diadromous, and 2 catadromous. Linear regression model base on the log-transformed catch weights classified species and months, using these factors as multiplicative determinants based on principal components were performed, </span><span style="font-size: 10pt; font-family: ">enabling assessment of clustering of species. The </span><span style="font-size: 10pt; font-family: ">model has four such components which correspond to predominant seasonal time series patterns, giving an </span><span style="font-size: 10pt; font-family: ">r-squared value of 87.6%.</span><span style="font-size: 10pt; font-family: "> Purely seasonal patterns were identified for the first two components: estuarine and marine vertebrates showed considerable seasonal fluctuations but otherwise appeared to be steady over the four year period. </span><span style="font-size: 10pt; font-family: ">Trends, mainly confined to the most recent year (2006) were identified for the third and fourth components: </span><span style="font-size: 10pt; font-family: ">freshwater and estuarine fish had increasing catch weights, while the catch weights of marine invertebrates decreased. </span><span style="font-size: 10pt; font-family: ">This model can provide practical lake information and reinforces that migratory fish species in tropical shallow lake need to be managed for sustaining their diversities.</span>