L - Cochin University of Science and Technology

E2.2.2.!. Richness (Margalef's index, d)
Depth wise average richness based on groups is presented in Fig. 42a. Group
wise richness showed slightly different trend as that of species richness with high
average richness in the deeper depth except at > 150 m. Group richness in the
southern transects varied from 0.12 to 1.53 and in the northern transects it varied
from 0.7 to 1.61 (Table 25). Transect wise richness in different depth zones is
presented in Fig. 43. Results showed that at 30 m zone, richness was more in the
northern transect stations than in the southern transect stations and the highest value
was observed off Dwaraka and lowest off Mumbai. At 50 m zone, with an
exceptional low value off Mormugao, richness decreased from ofT Ratnagiri to
veraval. At 75 m depth, richness was fluctuating with maximum value observed ofT
Mumbai and minimum ofT Veraval. Average values showed more or less similar
richness in the southern and northern transect stations at this depth zone. At 100 m
depth zone, richness was more in the northern transects than in the southern transects
with lowest value ofT Mormugao and highest off Dwaraka. At 150 m depth,
comparatively high richness was observed off Mumbai and low off Dwaraka with a
general decrease towards north. Below 150 m depth no comparison was possible due
to insufficient observation. Generally, at 30 m and 100 m depth zones, richness was
more in the north and in 50 m and 150 m it was more in south and at 75 m zone it
was more or less similar in northern and southern transects.
62.2.2.2.2. Evenness (Heip's index, J ')
Evenness was low in shallow depths and comparatively high evenness was
observed beyond 75 m depth zone (Fig. 42b). Evenness in the southern transects
varied from 0.04 to 0.69 and in the northern transects it varied from 0.27 to 0.81
(Table 25). Transect wise evenness distribution in different depth zones showed that
(Fig. 44) at 30 m depth zone, slightly higher values were observed off Mormugao,
and Ratnagiri and low values in the rest of transects. At 50 m depths, fluctuating
results were observed, with high value off Ratnagiri and low values off Mormugao.
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