Condition Factor and Length-Weight Relationship of Monsoon River Prawn Macrobrachium malcolmsonii malcolmsonii (H. Milne-Edwards, 1844) (Palaemonidae) in Lower Indus River

Macrobrachium malcolmsonii malcolmsonii is one of the commercially important prawn species in Pakistan and it is second largest and fastest growing among the Macrobrachium species. The present study was conducted in the lower Indus River at Thatta district, Pakistan, from April to June 2011 to document the growth parameters. A total of 109 specimens were collected from commercial catches at the local landing sites for the present analysis and body length (total length, TL) and weight (BW) were taken for all specimens. The TL for males and females ranged from 9.7-26.2 cm and 8.4-21 cm, respectively indicating males were generally larger than females. The coefficient b values of length-weight relationships (LWR) were 2.74 for males and 3.04 for females indicating isometric growth in females but negative allometric for males suggesting that female prawns were comparatively in better condition than males of the same population. The LWR analysis showed a highly significant correlation in both sexes (r(2) > 0.90, p < 0.001). The relative condition factor K for both males and females were computed as 0.61 +/- 0.18 and 0.86 +/- 0.46, respectively, suggesting that M. m. malcolmsonii in lower Indus River were in good condition. However, females recorded better condition than males which may be attributed to reproduction and the occurrence of ovigerous females. This paper presents the first report on the growth of M. m. malcolmsonii from the Indus River.