Marine ichthyofaunal biodiversity in the trawling grounds off Mangalore coast

Abstract

Present investigation was taken to assess the status of ichthyofaunal diversity off Mangalore coast. The data for the present study was collected from the multiday trawlers operating from Mangalore fishing harbour over a period from September-2012 to April-2013 and sampling was done once in fortnight. A total 97 species belonging to 72 genera, 50 families and 15 orders were recorded during the study period. The value of Shannon-Wienner index (H') was recorded ranged from 1.404 to 1.648. There is less variability among H'. Diversity and evenness are highly correlated (0.90) and showed variation with each other. Average value of Simpson index was found to be 0.038 and the value of Simpson index increased with decrease in diversity. In the present study the Margalef richness index showed a high positive correlation with H', N₁ and N₂, and J' and negative with Simpson index (λ), Evenness index (N₂₁ and N_21'). The value of H' showed positive correlation with all diversity indices except λ. K-dominance plot clearly demonstrated the diversity pattern during the study period. When the data of 8 month (September-2012 to April-2013) were plotted together, the curve which lied on the lower side during October-2012 extended further and rose slowly due to the presence of more number of species. K-dominance curve showed that density of fish species was high in the month of October-2012 and proved the number of species (richness) more in the month of October-2012 compared to other months. Bray-Curtis similarity (hierarchical clustering) from the overall cluster analysis, it was observed that the maximum similarity (89.65%) was observed between March-2013 and April-2013.