பயோடைவர்சிட்டி & அழிந்து வரும் உயிரினங்களின் இதழ்

Studies on biodiversity of pelagic fishes of Mangalore coast, Karnataka, India

Abstract

Nayana P

The current investigation was taken up to assess the status of pelagic fish biodiversity of Mangalore coast (Lat. 12°50'54"N; Long. 74°50'11"E). The data for the current study was collected from the trawlers and purse seiners operating from Mangalore fishing harbour over a period from September-2012 to April-2013 and sampling was done once in fortnight. A overall sixty nine species belonging to forty nine genera, 20 households and six orders had been recorded at some point of the take a look at period. Oil sardine contributed 26.97% of overall touchdown observed through Indian mackerel (26.30%). The own circle of relatives Carangidae contributed 21.74% of overall quantity of species, observed through Clupeidae 17.39%. Diversity indices together with Margalef s richness index, Shannon-Wiener index (H), Simpson index (λ), Hill variety quantity (N1 ) and (N2 ) and Evenness (J) had been calculated. The values of Shannon-Wiener index (H) (at log10) ranged among 1.1553 and 1.2679. The common fee recorded become 1.20, while maximum fee become recorded at some point of month of October 2012. The Simpson index (λ) ranged from 0.0650 to 0.0979, the common fee become 0.0836. Highest values for Hill variety quantity (N1 ) and (N2 ) had been recorded at some point of the month October 2012 and lowest at some point of the month of November 2012. The fee of evenness (J) ranged from 0.8134 to 0.9311. It become located to be lowest at some point of the month of October 2012 and maximum at some point of January 2013. Hierarchical cluster evaluation approach confirmed the similarity in species composition and abundance become located among the month of October and December 2012 (97.92%) and minimal inter-dating become among September and December 2012 (64.27%).

Evaluation of spatial-temporal variability of species composition and variety in oceanic ecosystems isn't smooth due to the fact it's also hard to acquire enough statistics quantifying such variability. In this study, we tested pelagic species range indicators, species richness, Shannon-Wiener index of range and Hurlbert’s species evenness, for fish assemblages from areas (north and south) withinside the North Pacific Ocean (2°–12°N, 178°E–165°W) in the course of May–July 2008. The assemblages had been primarily based totally on statistics accumulated through an onboard clinical observer in the course of a industrial longline fishing trip.

The equal sample become additionally obtrusive withinside the Non-metric Multi Dimensional Scaling plot wherein samples from Monsoon fell on one facet and people from post-monsoon and pre-monsoon on the opposite facet of the map demonstrating the near similarity with (80%) in species composition and abundance at some point of exceptional seasons. The strain fee, which become overlying at the MDS plot (0.01), confirmed an brilliant ordination of the samples collected. Studies have indicated that the Mangalore coast is one of the fundamental fishing harbours and having wealthy biodiversity; at some point of the take a look at period, there has been accurate recruitment to the fishery right now after the ban period, however the expanded recruitment did now no longer final for extra than 2 to three months; a bargain of pelagic biodiversity become located.