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against gastropods during pre- monsoon. In miscellaneous groups, sipunculids were comparatively high in number during post-monsoon, and during pre- monsoon sipunculids and nematods were the major taxa encounterd. Statistical analysis showed that species richness was low during post-monsoon. Richness and diversity of polychaetes were high in the shallow depths while that of crustaceans and molluscs were high in deeper depths in both seasons. Trophic relationships showed that primary production was adequate enough in the surface layers and was not limiting the benthic production. Estimated fishery potential showed that about 21 % of the tertiary production could be supported by benthic community (macro and meiobenthos) and rest of which contributed by microfauna, epifauna and benthos below 30 m depth. 13enthic biomass and its relation to the environmental parameters like temperature, salinity, DO, sediment texture and OM are discussed in chapter 7. In general, benthic biomass was positively related with temperature, salinity and 00. Sediment texture was another important factor and polychates and miscellaneous groups prefer fine sediment, whereas crustaceans and molluscs prefer sand dominated substratum. OM in the range of 1-2% is conducive for benthos beyond 3% it adversely affects the organisms. Multiple regression analysis revealed that a combined effect of three or more environmental factors affect the biomass and density distribution of most of the benthic fauna. But for the density molluscs and miscellaneous groups during post- monsoon a minimum of two parameters (viz, sand and temperature for molluscs; DO and depth for miscellaneous groups) showed higher influence. Thus it can be stated that no single factor could be considered as an ecological master factor as observed by Harkantra and Parulekar (1991). Trophic relationships showed that estimated annual macrobenthic production for the study area is about 311 kgC/km2/yr and meiobenthic production amounts to 994 kgC/km2/yr (since meiofauna have an average life span of 3 months, total annual 249
production will be more than that of macrobenthos) and the total annual benthic production (both macro and meio) in the study area will be 1.09 million tonnes. Average macrobenthic biomass in the study area was 4.16 g/m 2 and for meiobenthos it was 2.88 mg/m 2 . Benthic biomass and density was generally high in the shallow depths compared to the deeper zone. Average biomass for the shallow depths (30 and 50 m) was 6.73 g/m 2 and in deeper depths (150 m and beyond 150 m) it was 1.5 g/m 2 . On av average basis, population density for shallow depths and deeper depths were 1971 ind/m2 and 790ind/m 2 respectively. Thus a three-fold decrease in the benthic biomas and more than one fold decrease in density from shallow to deeper depths were observed in the study area. Seasonal difference was not observed for biomass as well as density. Latitudinal variation was not well defined, however, relatively high biomass was recorded in the northern area while density was more in the southern area. Polychaetes were rich and diverse in the shallow depths and decreased with depth. in deeper zones, members of family Spionidae, Cirratulidae and Cossuridae were predominant suggesting their ability to withstand low oxygen conditions. But richness and diversity for crustaceans and molluscs were high in deeper depths. Similar to the macrobenthos, total biomass and density of meiobenthos were high in shallow depths and low in deeper depths. Nematods were the dominant group at all depths and their distribution pattern was comparable to that of total biomass and density. Copepods and miscellaneous groups were low in shallow depths and high at deeper area. Temperature and DO showed significant variations between the seasons but significant difference in sediment charecteristics was observed only in the shallow depths (30 and 50 m). Benthic biomass and density did not show any significant difference for the two seasons. Community structure showed significant changes in the two seasons except few depths especially beyond 100 m. Ecological relationship showed that combined effects of temperature, DO, salinity and sediment charecteristics were mainly steering the benthic production, distribution and seasonal 250
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Certificate I hereby certify that t
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Contents Page No. Chapter 1. Introd
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the bottom. Ekman (1935) described
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wonns are the most abundant group a
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leadership of Sir James Clark Ross,
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Ansari et al., (1977b) carried out
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Gopalakrishnan and Nair (1998) cond
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Major objectives:- 1. To understand
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CMFRI (Central Marine Fisheries Res
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Joydas, T.V., Damodaran, R., 2001.
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monitoring committee (Atlantic Mari
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Vizakat Lathika, I-Iarkantra, S. N.
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analysed after acidification by tit
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used as stain prior to sorting and
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space. Therefore, it is very essent
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Fig. I - Station locations 32
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affected at high temperature. Most
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layers exhibit different oceanograp
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Transect wise variation in temperat
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3.2.2.3. Dissolved oxygen (DO) Dist
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monsoon temperature initially incre
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opined that limited mixing. high or
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Naqvi, S. W. A., Noronha, R. J., Re
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orr Mormugao orr Vernal 35.36 35.32
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The continental shelf and its adjoi
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sediments (4 stations). Silty sand
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fine sediments with comparatively h
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Narayana, 1991 ). Limited input of
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In general. two ditlerent patterns
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et al., (1980) reported values in t
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organisms living in the water and t
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Hashimi, N. H., Kidwai, R. M., Nair
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Postma, H., 1967. In Estuaries, Lau
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Depths Sand Silt Clay Organic matte
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• PRE'MONSOON SOUTHERN'TRANSECTS
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as the best indicators of the envir
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showed that northern transects have
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decreased from shallow to deeper de
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different depth zones showed that a
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cm 2 with a dominance of nematodes.
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and 6.08 g/m 2 were recorded during
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were located in the nearshore water
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changes in the hydrographical and t
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factor for such a large difference
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Belegvad, H., 1932. Investigations
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Parulekar, A. H., Harkantra, S. N.,
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Savich, M. S., 1972. Quantitative d
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Traosects Polychaetes Crustaceans M
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Miscellaneous Transects Nematodes C
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Depths Nematodes Cope pods Foramini
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Wagh, 1975; Parulekar et ai, 1976;
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ones and 17 were included in the 'r
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Nephtydae (2%). Among the 20 sedent
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At 75 m zone, 31 groups/species wer
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Porbandar. At 50 m depth zone, fluc
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otTMumbai and Ratnagiri and low eve
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species richness at each depth zone
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E2.2.2.!. Richness (Margalef's inde
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I ):.2.2.2.4. Dominance (Pie/ou's i
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Tablc 17. Contd .. - Sternaspidae 0
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Table 20. contd .. G. alba 20 25 20
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150 Taxa 30m 50m 75m lOOm 150 m m D
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9% 1% o poIychaete • crustacea o
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a) c) e) g) Plate 5 a) Prinospio sp
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a) c) e) Plate 7 a) Cardium sp. d)
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7/. /ntroduct ion 7.2. Hydrography
Page 211 and 212: also showed a similar pattern with
Page 213 and 214: y most of the organisms. It was als
Page 215 and 216: with sand of which total density (r
Page 217 and 218: muddy bottom of the west coast of I
Page 219 and 220: crustaceans and miscellaneous group
Page 221: the organic rich environment with h
Page 225 and 226: Icvci (p
Page 227 and 228: mcioHmna serve primarily as rapid m
Page 229 and 230: surface chlorophyll a was 0.36mg I
Page 231 and 232: Devassy, V. P., Achuthankutty, C. T
Page 233 and 234: Longhrust, A. R., Pauly, D., 1987.
Page 235 and 236: Sikora, W. B., 1977. The ecology of
Page 237: Faunal groups Silty Clayey Mixed Sa
Page 257: Mannagoa to Porbandar located betwe
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