The study of seasonal variation in distribution of 167 fishes of magalaspis cordyla from the Karachi fish harbour collected seasonally (pre-monsoon, mon-soon, post-monsoon) between September 2011-August 2012. The highest catch of fish (68) was recorded in pre-monsoon season and the lowest catch of fish (47) was recorded in monsoon season. The highest mean length (38.6+ 0.746) and weight (288+ 21.90) was measured during pre-monsoon season and lowest mean length (22.5+ 0.671) and weight (120.5+ 2.73) was measured during mon-soon season. The highest mean condition factor (1.192+ 0.817) and minimum (0.500+ 0.038) was recorded in pre-monsoon season. Fish estimated negative and positive allometric growth because b values larger and less then 3 in pre-monsoon and monsoon season but post-monsoon season showed positive allometric growth because b value larger then 3 in all size classes