Length-weight relationships and condition factor of giant freshwater prawn, Macrobrachium rosenbergii (De Man, 1879) in five perennial reservoirs in Northern Province, Sri Lanka

Abstract

Present study was mainly investigated length-weight relationships and condition factor of M. rosenbergii stocked in two large (Vavunikulam, Muthayankattu) and three small (Puthumurippu, Kalmadu, Muhathankulam) perennial reservoirs in Northern Province of Sri Lanka as culture-based fisheries. Randomly selected 300 Macrobrachium rosenbergii caught by multi mesh gillnets between January to December 2017 were analyzed. Non-linear regression analysis was conducted for total length (L) and body weight (W) of M. rosenbergii as power function W= aLb. Fulton’s condition factor (K) was calculated by using the formula: K = (W * 100)/L3. One-way ANOVA and Tukey comparison was conducted for significance of condition factor among reservoirs. Allometric growth coefficient (b) ranged between 2.1295 – 4.2068. Highest b value was observed in both Kalmadu (b=4.2068) and Puthumurippu (b=4.1132), while the lowest from Vavunikulam (b=2.1295). Mean condition factor (K value) of M. rosenbergii ranged from 1.3928 – 1.9505 and overall K value was 1.6130. K values were higher in Puthumurippu (1.9505) and lower in Vavunikulam (1.3928). Smaller reservoirs had higher condition factor values than larger perennial tanks and M. rosenbergii were in a good health condition in these five reservoirs.