Species abundance and distribution patterns of some shellfishes in coastal waters of Ondo State, South West, Nigeria

Abstract

The abundance and distribution of some shellfishes of the coastal waters bordering Ayetoro, Bijimi, Asumogha and Idiogba of Ondo States, Nigeria was studied between September and December, 2011. Specimens were collected monthly with the assistance of artisanal fishermen. The population structure and distribution patterns were determined using Margalef’s diversity index, Sorensen’s index, and Number of Occurrence Index (NOI). Nematopalaemon hastatus, Farfantepenaeus notialis, Parapenaeopsis atlantica and Portunus validus occurred at the four sampling stations throughout the sampling period. Macrobrachium macrobrachion was not caught in December whileCallinectes marginata and Ocypode africana were caught once during the sampling period. In September, N. hastatus was dominant in the four locations with 83.05%, 76.47%, 72.50% and 71.67%, in Ayetoro, Idiogba, Asumogha and Bijimi respectively. In Asumogha in October, N. hastatus had 71.93%, F. notialis17.54%, P. atlantica 7.89%. while P. validushad 2.64% NOI. 207 specimens were captured from Idiogba in November and N. hastatushad 86.96% NOI. The diversity index (d) ranged from 0.38 at Idiogba to 0.91 at Asumogha in December and September respectively, while Sorensen’s similarity (Cs) values ranged from 0.38 to 0.5. The study revealed that there was a generally high similarity among the shellfish communities in the four sampling stations.