3. MARINE LIVING RESOURCES

 

3.1  Assessment of Marine Living Resources

 

This programme initiated during 1997, envisages comprehensive assessment of the Marine Living Resources of the Indian EEZ and studies on the influence of the marine environment on these resources.

 

Environmental parameters, primary and secondary productivity

Assessment of environmental parameters, primary and secondary productivity in the Indian EEZ was carried out in four seasons, i.e., inter-monsoon (Spring - March to May); Summer-monsoon (June to September); inter-monsoon (Fall - October) and winter monsoon (November to February). Bay of Bengal was studied during inter-monsoon (Spring: March - May) and winter-monsoon (November - February) where as Andaman sea and Arabian Sea were surveyed during inter-monsoon and summer monsoon (June - September), respectively.

Physical Oceanographic Studies

Andaman Sea:

The mixed layers were constant (~50 m) during March along the North-South transect and in the East-West transect observed up to 11 m, which could be due to an open ocean upwelling. During inter-monsoon the mixed layer showed lateral variation ranging
from 30 m to 60 m.

 

Bay of Bengal:

It was observed that the mixed layers varied between 10 and 40 m and tended to be deeper in the middle along east west transect. The most conspicuous feature observed was the presence of a less saline, less thermal and less dense pool of water within the upper 50 m, which could be due to heavy precipitation or heavy river influx during winter monsoon period.

Chemical Oceanographic studies

Andaman Sea:

During inter-monsoon (Spring) low concentration of dissolved oxygen was observed between 150 and 500 m depth. The thickness of the oxygen minimum layer is more along the northern latitudes than the southern latitudes as a result of poor water exchange and relatively stagnant water with low oxygen concentration.  Nitrate level increased from a non-detectable level to 30 m mol/l at 200 m depth and          38 m mol/l at 1000 m depth. The nutrient values were almost constant at all the stations, indicating the poor renewal of water at deeper depths in the Andaman Sea. The magnitude of values for phosphates and nitrates is observed to be relatively higher than those recorded for corresponding depths in the Arabian Sea.

Bay of Bengal:

During inter-monsoon (Spring), the Oxygen Minimum Zone (OMZ) was observed between 150 and 600 m depth and the thickness of OMZ increased towards northern latitudes. The concentration of phosphate was relatively higher in the shelf waters ranging from 0.6 m mol/l to 1.6 m mol/l. The value increased towards the west in almost all latitudes. The concentration of silicate and nitrate increased rapidly with the thermocline and further down to 200 m depth. In general, nutrients in the mixed layer were high. Dissolved oxygen ranged from 200 m mol/l at the surface to 100 m mol/l at 75 m depth.

 

Arabian Sea:

The high concentration of nutrients and dissolved oxygen and low sea surface temperature during southwest monsoon revealed signatures of upwelling along the west coast. The vertical sections of various chemical parameters along 8 transects indicated tilting up of isolines towards coast in the shelf and slope region.

 

Biological Oceanography

Primary productivity studies:

Primary production was varying between 3.54 - 10.17 mg Cm^-3 d^-1 and 172 - 674 mg Cm^-3 d^-1 during the inter-monsoon (Spring) for the surface and column with the corresponding averages of 6.3 mg Cm^-3 d^-1 and 390 mg Cm^-3 d^-1 in the Andaman Sea. Surface and column chlorophyll-a value ranged between 0.1 - 0.24 mg m^-3 and 9.6 - 23.8 mg m^-3.

A patchy layer of blue green algal bloom (Trichodesmium erythraeum) was observed along the eastern Bay of Bengal near Andaman Islands andcontinued towards the coast at 420 m depth. Along the east coast of India, the surface and column primary production varied between 0.9 – 15.1 mg Cm^-3 d^-1 and 139 – 340 mg Cm^-3 d^-1 and the corresponding averages were 6.5 mg Cm^-3 d^-1 and 233 mg Cm^-3 d^-1, respectively. Surface and column chlorophyll-a values varied between 0.08 – 0.28 mg m^-3 and 8.5 – 22.3 mg m^-3. Also two more blooms of blue green algae were observed off Karaikal and off Chennai. It was recorded that the primary production and chlorophyll-a values were comparatively similar in Andaman Sea and Bay of Bengal during inter-monsoon (Spring) with the occurrence of Trichodesmium blooms in these areas.

 

                                                      

Distribution of primary production in Bay of Bengal

 

 

Surface primary production (mg C/m3/d) in Bay of Bengal (a) Summer monsoon 1999 (b) Winter monsoon 1999 (c) Inter monsoon 1999

Column primary production (mg C/m3/d) in Bay of Bengal (d) Summer monsoon 1999 (e) Winter monsoon 1999 (f) Inter monsoon 2000

 

Secondary production:

In Andaman Sea the mesozooplankton biomass ranged between 36 ml/1000 m³ - 399 ml 1000 m³. The highest biomass recorded was 399 ml/1000 m³. The minimum and maximum biomass of the mixed layer along the east coast of India were 775 ml/1000 m³ and 25 ml/1000 m³, respectively. The biomass densities were high in both southeast and northeast coastal stations than oceanic stations. Along the southwest coast of India, the zooplankton biomass ranged between 183 ml/1000 m³ and 1333 ml/1000 m³. Data were also obtained for different depth strata in all transects for assessing secondary production. The dominant groups in the upper 1000 m were Copepods, Ostracods, Decapods, Siphonophoresand Chaetognaths. The abundance of Copepods in the surface layers showed more or less similar trend in both west and east coasts. In the Arabian Sea, maximum density of copepods recorded was in the thermocline layers. The distribution of ostracods was patchy and was absent in deeper strata. Chaetognaths were more abundant in the thermocline layer in some transects in the west and east coasts. It is evident that the phenomenon of vertical migration is well manifested in the summer monsoon period. The subsurface layers and even deeper layers support a rich mesozooplankton assemblage, which is brought to the surface during night.

 

                                                        

                      Distribution of mesozooplankton biomass (m1/1000m^-3) in the mixed layer of the Indian EEZ

Studies on Deep Scattering Layers:

Acoustic recordings and samplings with IKMT in 18 day samplings and 16 night samplings were carried out along the east and west coasts. During pre-monsoon (April and May) 26 stations were covered and 8 stations during monsoon. Quantitative estimation of the DSL has revealed that west coast was rich with diverse assemblage of zooplankton and nekton. West coast contributed an average of about 77% and 57% to the total DSL production during day and night, respectively. DSL organisms of the west coast especially the south west coast had made significant (40%) contribution to the total production. Nekton like pelagic shrimps, myctophids other mesopelagic fishes that dominated the catches could be considered a potential prey for major and exploitable pinnacle carnivorous fishes/shellfishes. High marine fish production from the west coast could be considered as a positive indication of the aspired importance these DSL organisms have in the diet of commercially exploited/exploitable larger pelagics and demersal fishes.

 

It is evident from the analysis that pelagic shrimps especially Leptochela sp. and Thalassocaris sp. which generally appear in swarms could be considered as indicators of larger pelagics in particular, tunas. Decapods especially pelagic shrimps were concentrated in the catch of south-east and north-east coast during day and night, respectively. Ichtyoplankton were more abundant along the north-west coast. Cephalopods were dominant in the catches from the north-west coast during day and south-west during night. Myctophids were found to be more abundant along the north-west during day and night. The biodiversity and abundance of other mesopelagics were in the southwest coast during day and night.

 

                                                                    

                                                                                         

                    

 

Three Species of Pelagic shrimps

 

The horizontal distribution studies showed that the DSL is more dense and concentrated in the shelf break region and beyond (slope waters).

Resources Assessment and Biology of deep-sea fishes in the continental slope of Indian EEZ

The research team involved in this venture explored the deep-sea fishery resources in four cruises, conducted along the continental slope, i.e. one in Andaman waters, another off east coast and two off west coast of India. By using EXPO model fish trawl, HSDT (Fish and Crustacean versions) and HOT, 81 fishing operations were carried out spanning over a period of 72½ hours, which yielded 17,186.3 kg with a CPUE of 237.05 kg/hr.  Along the south-west coast the CPUE obtained was 428.98 kg/hr.

	Deep sea lobster catch onboard FORV Sagar Sampada
Psenopsis cyanea- a dominant species in the continental slope

 

Harvest technology and catch composition studies

Comparative escapement studies were carried out with HSDT – II (Fish and Crustacean versions) by using 40 mm square, 40 mm diamond and 30 mm square mesh cod end with 20 mm cover. It was observed that the gear with 40 mm square mesh cod end provided more escapement of juveniles and sub-adults of all finfish species. In demersal trawl operations 30 mm square mesh cod end provided better chance for escapement of juveniles and sub-adults of shellfishes. Based on the comparative studies 35 mm square mesh cod end is suggested for demersal trawl operations in the offshore waters for better management and conservation of fishery resources.

 

The gear selectivity studies were also conducted with 40 mm and 35 mm of square and diamond meshes cod end with 20 mm cover. Rectangular Mid-water Trawl 6 EL was tested with Suberkrub otter boards which achieved 7.8 m vertical opening with 70 m sweep line. During the study period 70 hauls were conducted, all the species caught were identified and recorded.

 

Modified version of HSDT - II (Fish Version) Net having a provision for escapement of fish

from the cod end of the net.

 

Investigation on toxic algal bloom in the EEZ of India

The major groups of micro-algae observed during the period were dinoflagellates, diatoms and blue green algae. Among 78 sp. of dinoflagellates identified during this period three species were harmful algae. Out of 47 species of diatoms, 4 species belonged to the harmful group. Trichodesmium erythraeum is the only species that is harmful among several blue green algae found during this period.

 

Two Species of dinoflagellates- harmful algae.

 

The chlorophyll-a value varied remarkably - 0.05 mg/m³ to 1.15 mg/m³ (182); 0.056 mg/m³ to 0.332 mg/m³ (184); 0.079 mg/m³ to 0.332 mg/m³ (186) during different seasons. The chlorophyll-a value was found to be 218.4 mg/m³ at the blooming region of Cochin coastal waters. The amount of carotenoids was also found to be high at this station. The primary production and chlorophyll values were very high in the sampling points where blooming was observed.

 

Benthic productivity in the EEZ in India

Meiobenthos

The meiobenthos were represented by eight groups, of which the nematodes constituted the bulk of the population followed by foraminiferans and copepods that revealed considerable spatial differences in relation to location, depth and nature of the sediment. Meiobenthos densities were appreciably high along the northeast coast (mean 190 nos./10 cm²), even though the biomass being a meagre 0.39 mg/10 cm². In the west coast, despite low abundance (165 nos./10 m²), the biomass was the highest (2.05 mg/10 cm²).

 

Macrobenthos

The macrobenthos was represented by 15 groups. Based on the epifaunal elements, the northeast coast supported a great majority of species (121), which were numerically rich (mean 56 nos./haul). Macrobenthos densities for the whole of west coast registered the highest value at 1385 per sq. m. The benthic biomass for the west coast levelled at 5.53 g/m².

 

Sediment texture

On the west coast where the width of the continental shelf varies markedly from south (82 km) to north (237 km), the most important textural class at a great majority of the stations (32/62) was sand. In contrast, sediments along the east coast were mostly clayey-silt.

Resources assessment and biology of deep-sea fishes

The deep sea fishery resources of our EEZ along the east and west coasts including the Andaman and Nicobar waters were explored. The samples were collected from the continental slope. Bottom fishery resources were sampled in 81 stations by operating different types of gears viz., EXPO Model (Fish version), High Speed Demersal Trawl (Fish and Crustacean Versions) and High Opening Trawl. The average CPUE recorded was 237 kg/hr.

 

Along the South-west coast of India, the average CPUE obtained was 430.24 kg/hr. The maximum CPUE recorded in a single haul was 1053.33 kg/hr, at 242 m depth. The samples were collected along the east coast in the depth range of 202 m to 1024 m with the average CPUE of 113.81 kg/hr. The landing was dominated by finfish. In Andaman and Nicobar waters, the CPUE registered was 44.56 kg/hr.

 

A detailed study on biology (Lengthy frequency, Length-weight relationship, food and feeding habits and maturity studies) of all the economically important species was carried out.

 

3.2 Drugs from Sea

The National Project on Drugs from Sea is a multi-institutional project aiming at developing potential drugs and chemicals from the marine flora and fauna. This project has led to identification of five marine organisms showing potent activity as anti-diabetic, anti-viral, anti-anxiety, anti-cholesterol and larvicidal agents for developing new drugs during the IX Plan. In order to focus on product development and exploratory work, the project was extended for another two years from 2000-01 onwards.

During the period under report, over 350 new samples of marine flora and fauna were collected and tested for various pharmacological activities. Bioactivity confirmation, regulatory pharmacology, safety toxicology of anti-diabetic and anti-diarrhoeal products were completed and licensed to M/s Axon Biogenics Ltd of New Delhi as a part of the product development programme. The third product, which is awaiting clearance for monkey toxicity studies, has been found to be safe in rodent toxicity. Five new organisms showing anti-fungal, anti-hypoglycaemic, and anti-hyperlipidemic activities were identified under the exploratory phase of the project. These organisms have shown significant activity on repeat tests and they would be subjected to further screening for future drug development.