Some Biological Aspects of Lanchester’s Freshwater Prawn for Resources Management in Kwan Phayao Wetland, Phayao Province

Abstract

The purpose of this research was to study growth and reproductive biology of Macrobrachium lanchesteri de Man in Kwan Phayao Wetland, Phayao Province. The results were derived from catchment data and field information of 4,128 prawn samples collected monthly during January 2017 to December 2017. The samples were analyzed by FiSATII program (FAO-ICLARM Stock Assessment Tools). The relationship of body weight and total length was W = 0.0107TL^2.7073 (R²= 0.9284, n = 4,128). The sex ratio of males to females was 1:1.21. The maturity study indicated that this species spawned year round with a peak during April to September. The minimum size of gravid females was 2.0 cm in total length and 0.11 g in body weight. The maximum size of gravid females was 6.2 cm in total length and 1.62 g body weight. The rate of exploitation was 0.74. The average length at 50% maturity (Lm) of M. lanchesteri in the Kwan Phayao was 3.33 cm. Forty percent of the catch compositionmeasured less than the average length at 50% maturity. The fishing gears used were prawn traps (Sai Kung), scoop nets with old gillnets (Chon Kung), and tighter net traps (Lhong/E-abb), main fishing gears employed by the fishermen. The average daily prawn catch per fisherman was 2.4±0.7 kg. Lhong/E-abb had the highest catch efficiency followed by Chon Kung and Sai Kung with averages of 3.2±2.0, 2.5±1.3 and 1.5±0.6 kg per day per fisherman, respectively. In conclusion, the most urgent fishery management measure to be taken in this wetland should be controlling the amount of fishing effort based on the stock size of fishery resources.