Fisheries Ecology of the Dawhenya Impoundment

The fisheries ecology of the Dawhenya impoundment with special reference to the freshwater prawn, Macrobrachium vollenhovenii was studied for a period of 12 months. The analysis of the population parameters of M. vollenhovenii was done using the routines in the FAO-ICLARM Stock Assessment Tools (FiSAT). The length-weight relationship showed that the species exhibited a positive allometric growth pattern. The estimation of the von Bertalanffy growth parameters gave, L¿ = 14.2 cm, K = 1.0 yr-1, and to = -0.195 yr-1 with the growth performance index, ¿' of 2.303. From the mortality estimations, the present rate of exploitation, E was 0.59 indicating that the species was being over-exploited in the impoundment. The relative yield-per-recruit from the selection ogive option gave maximum exploitation rate of 0.525 which is lower than the computed exploitation rate, confirming the high fishing pressure on M. vollenhovenii. Using the estimated value of the growth coefficient, K, the longevity was found to be 3 years. The estimations from the probability of capture routines gave the length-at-first capture, Lc as 3.07 cm.