Comparison of the Condition Factor of Five Fish Species of the Araguaia River Basin, Central Brazil

This study aims to assess the condition factor (K) of five fish species (Serrasalmus rhombeus, Psectrogaster amazonica, Loricaria cataphracta, Panaque nigrolineatus and Squaliforma emarginata). Samplings were conducted during the low-water period of 2007 and 2008 using gillnets and minnow traps. All equipments were placed along a stretch of 1000 m at 5 pm and retrieved at 7 am. Collected fish were taxonomically identified, weighed (g) and measured (standard length; mm). The fish fitness was assessed by the condition factor (K=W/L³) and compared among groups of tributaries by a Kruskal-Wallis test. From the five species considered, two (S. emarginata and P. amazonica) displayed significant differences of the condition factor among the groups of tributaries. The highest values of K correspond to fish located in the headwaters, while lowest values are observed in tributaries located in the floodplain.