Publisher: Bachudo Science Co. Ltd

Influence of Rainfall On The Dynamics of Two Prawn Populations In The Cross River Estuary, Nigeria.

U. I. Enin
KEYWORDS: Rainfall, Catch rate, Spawning, Recruitment, Macrobrachium. Nematopalaemon, Cross River Estuary, Nigeria


The influence of rainfall on the population dynamics of the prawns, Macrobrachium macrobrachion Herklots 1851 and Nematopalaemon hastatus Aurivillius 1898, in the Cross River Estuary, Nigeria, was investigated. Rainfall accounted for a significant portion of the variations in catch rate, spawning and recruitment indices of M macrobrachion. This is because the processes of migration to the estuary, and the spawning of the prawns there, are presumably not only triggered off by rainfall but aiso progressively influenced by it With significant relationships also among the popolation variables (catch rate, spawnina and recruitment indices) at appropriate lags, it was possible to chart the time steps from rainfall through cater, rate, to spawning and recruitment A certain amount of rainfall in a given month leads to a given abundance of adult population (catch rate) in the estuary two months later, which is followed in another one month by spawning. Recruitment takes place 4 to 5 months after spawning. Thus the time span from rainfall to recruitment of the young of a given cohort ls 7 to 8 months. For N. hastatus, the catch rate in the estuary does not see,n to proceed linearly with rainfall because after the early rains, the prawns migrate offshore for spawning purposes However. from the analyses the time span from rainfall through spawning to recruitment of the young was estimated at 6 months. 

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