STUDIES ON TAXONOMY, DISTRIBUTION, ECOLOGY AND REPRODUCTIVE POTENTIAL OF ROTIFERS FROM SELECTED CENTRES IN COCHIN BACKWATER SYSTEM, KERALA

The studies were conducted in nine stations with varying ecological characteristics along Cochin backwaters and adjoining canals. Many workers opined that the distribution of rotifers is cosmopolitan. The significance of rotifers as first food for early larvae was indicated by Fujita. Aquaculture is a fast growing field in fisheries sector and it is gaining more importance as the fish landings and supply are getting irregular. A consistent supply of fish/shellfish can only be achieved through aquaculture. The success of any culture activity depends on the timely production of seeds of finfishes/shellfishes. The availability of wild seed is seasonal and erratic. So, a dependable source of seed of fishes and shellfishes is possible only through large scale production in hatchery. A successful seed production activity depends on the availability of a variety of suitable live feed organisms in sufficient quantities at the proper time for use in the larval stages. As the live feeds promote high growth rates, easy digestion, assimilation and the quality of not contaminating the culture water when compared to other artificial feeds, make the culture of live feed organisms the principal means of providing food for the larvae of finfishes and shellfishes. Rotifers are considered to be an excellent and indispensable food for larvae of many finfishes and crustaceans. It (1960) was the first to culture Brachionus plicatilis for feeding marine fish larvae, and now it is being extensively used as live feed in hatcheries all over the world. They are a group of microscopic organisms coming under the Phylum Rotifera which comprises of about 2000 species. Their slow swimming habits, ability to tolerate a wide range of salinities, parthenogenetic mode of reproduction and ability to get enriched easily, make rotifers an ideal live feed organism. The major factors such as temperature, salinity and food that influence the reproductive potential and thereby the population size of rotifer, Salinity is one of the most important aspect influencing the reproductive rate of rotifers. The feed type and feed concentration play a vital role in influencing the reproductive rate of rotifers. For culture of rotifers, the commonly used micro algae belong to Chlorella, Nannochloropsis, Isochrysis and Tetraselmis. While some studies have suggested that, algal diet has little effect on reproductive rates in 1979 while using the rotifer, Brachionus plicatilis as feed for the larvae of red sea bream, Pagrus major. It is generally accepted that rotifers play a pivotal role in the successful rearing of marine fish larvae.

lmpact of bottom trawling on benthic ecology along the coastal waters of Kerala with special reference to meiofauna

School of Industrial Fisheries, Cochin University of Science and Technology

Nutrient Mobility in Chalakudy River,Typified With Riparian Buffer Zone and Its Adjoining Estuary:Spatiotemporal Manifestation

This study was aimed at to characterize the spatio-temporal trends in the distributional characteristics of various species of nitrogen and phosphorus as well as to elucidate the factors and processes aflecting these nutrients in the dissolved, particulate and sedimentary phases of a river estuarine system. The main area of study is Chalakudy river in Kerala, which is a fresh water system originating from Anamalai hills and ending at Arabian Sea. Its basin is between I00 05 ’ to I00 35’ North latitude and 76” 15 ’ to 760 55’ East longitude. Being a riparian bufler zone, the dynamics of nutrient mobility tend to be more complex and variable in this river-estuarine system.The diflerent species of nitrogen estimated from the filtrate were nitrite-N, nitrateN, ammonia-N, urea-N, total nitrogen and residual nitrogen. The diflerent forms of phosphorus estimated from the filtrate were phosphate-P, total-P and residualP. Pre weighed sediments as well as particulate matter were analysed for quantijying nitrite-N, nitrate-N, ammonia-N and urea-N. Total nitrogen was estimated after digestion with potassium persulfate. Fractionation of phosphorus in sediment/particulate matter was performed by applying sequential extraction procedure. The dijferent forms of phosphorus thus estimated were loosely bound (exchangeable) P, Fe/Al bound P, polyphosphates, Ca bound P and refractory P. Sedimental total P was also measured directly by applying digestion method.The analyses carried out in this bimonthly annual survey have revealed specific information on the latent factors influencing the water quality pattern ofthe river. There was dependence among the chemical components of the river sediment and suspended matter, reflecting the water quality. A period of profound environmental change occurred and changes in various species had been noted in association with seasonal variations in the waterway, especially following enhanced river runoff during the monsoon. The results also successfully represented the distribution trend of nutrients during the rainy as well as dry season. Thus, the information gathered in this work will also be beneficial for those interested or involved in river management, conservation, regulation and policy making in regional and national levels.

Studies on taxonomy and ecology of Mysidacea from the EEZ of India

Members of the order Mysidacea are important component in marine and estuarine plankton inhabiting all regions of the oceans. There are many brackish water species and few species occur in fresh water, some have become adapted to the specialized environments of caves and wells. They are omnivores, responsible for remineralisation of a substantial portion of the detritus in the water column. They form an important link in the food chain (between microbial producers and secondary consumers) and therefore play a major role in the cycling of energy within the aquatic ecosystem. In tropical and subtropical waters, swarms of mysids are exploited commercially and marketed as preserved cooked food. Mysids have been used in fish farming as live feed resource. They are also excellent experimental organism, extremely useful in the studies of potential impact of various pollutants in the aquatic environment. Mysids are also used in wood pulp effluent plants.Considering the significant role of mysids in the productivity of tropical and coastal ecosystems,the present study has been undertaken to extend our knowledge on the systematics, species composition, distribution,abundance and ecology of mysid fauna of the Indian EEZ and adjoining areas. The present study therefore will undoubtedly fumish valuable information on Mysidacea of the Indian waters.

Studies on the Biology, Ecology and Fishery of the sea cucumber Holathuria (hetriatyla) scabra (Jaeger) from southeast coast of India

The distribution of the holothurian H. KH.) scabra indicated its availability all along coastal areas on Palk Bay from Rameswavam to Mallipattinam and along the Gulf of Hannah coast from Pamban to Ervadi and Tuticmhin,'at 4~2O m depth.The major fishing for holmthurians was done by skin diving at all the centres. The tallu valai was operated at Tuticorin and Vedalai and trawlevs were operated at Rameswaram.The fmod of H. KN.) scabra consists of ovganic matter which contains mud, sand, shell debris, bivalves and algae. Obsehvatinns indicated the species seems to be a n0n—se1ective feeder. The assimilation efficiency from sediment to faeces indicated that the faecal pellets of H. KH.) scabra are semidigested.A multiple relationship was fitted between total length, total weight, gutted weight, gonad weight and maturity stages were found significant.The fishing season for holothurians commences from October to March along Gulf of Manner coast and from March to October along Palk Bay coast.The percentage of catches recorded by skin diving, trawlere and tallu valai were 80.04%, 10.27% and 9.69% respectively. Skin diving contributes to maximum catch.The holothurians landed all along the Gulf of Manner and Palk Bay coasts constitute 25.6% and 74.4% respectively. This showed that Palk Bay coast is more productive.

Ecology of Chaetognaths in the Indian EEZ

This thesis entitled ecology of chaetognaths in the indian EEZ.The present study, in general, deals with the distribution pattern of mesozooplankton biomass and abundance with special reference to the detailed ecology of the important carnivorous planktonic group, the chaetognath, in the two major ocean basins of the Indian EEZ, the Arabian Sea (AS) and the Bay of Bengal (BoB). Prior to the International Indian Ocean expedition (IIOE, 1960 – 1965), cmprehensive studies on chaetognath in the Indian waters were very limited and was confined mostly to some coastal and oceanic regions. The study revealed a profound influence of different physical process on the abundance of chaetognath community. The significant influence exerted by different physico-chemical factors on the vertical distribution of chaetognath species was also evident. Prior to this study, only very little information was available on the ecology and distribution pattern chaetognaths in both the Arabian sea and the Bay of Bengal in relation to various mesoscale processes and physicochemical .variables. This study, emphasizing the short term and long term influences of different meso-scale and basin scale physical events on the ecology of this important plankton group provides the baseline data for extensive ecological research on any major mesozooplankton group in this tropical low latitude region.

Benthic ecology of selected prawn culture fields and ponds near Cochin

The thesis on the"Benthic ecology of selected prawn culture fields and ponds near Cochin” was taken up with a view to provide information on the qualitative and quantitative distribution of benthos and their relationships to prawnproduction of different culture ecosystems and to the physico-chemical parameters influencing their production. A two-year observation was carried out in nine selected prawn culture systems including perennial ponds (stations 1 to 4) seasonal fields (stations 5 to 7) and contiguous canals (stations 8 and 9) during December 1988 to November 1989. All macro- and meiobenthic organisms contributing to the faua were identified and their abundance, distribution, diversity, biomass and trophic relationships between benthos and prawns were studied. The environmental variables studied were temperature pH, salinity, dissolved oxygen, alkalinity, nitrite-nitrogen, nitrate-nitrogen, amonianitrogen, phosphate and silicate of bottom water and organic carbon and texture of the soil The thesis is presented in 4 Chapters. Chapter I presents an’ INTRODUCTION to the topic of study and a review of relevant works to bring an awareness to the present status of research in benthos and benthic ecology. Chapter 11, MATERIALS AND MTHODS, includes the techniques of sampling, preservation of samples and methods of analyses of various physico-chemical factors and area covered under the study is also given in this chapter. Chapter III, HYDROGRAPHY deals with the results of investigation and discussion onthe physico-chemical parameters of water and Chapter IV, SEDIMENT covers the sedimentoloical characteristics of the different culture systems followed by a detailed discussion. Chapter V, BOTTOM FAUNA presents an account on the various aspects of benthos and benthic ecology and the details of prawn production. A discussion on the overall assessment of interrelations between abiotic and biotic factors is given in Chapter VI, DISCUSSION. A critical evaluation of the implication of benthic production on prawn production under culture conditions and trophic relationships are also included in this chapter. An executive SUMMARY of the observations made during this study is presented in the final section of the thesis .

Some observations on the ecology and biochemical aspects of the seaweeds of Kerala coast

In the present thesis , observations on the ecology of seaweed flora of Kerala, their distribution and zonation pattern, monthly/seasonal density of seaweeds at each station, frequency of occurrence, standing crop, monthly/seasonal/place-wise data on physico—chemical characters of ambient waters at the stations and their influence on seaweed density have been made. This data will help us in the farming of economically important seaweeds, by providing information on the ideal conditions of seaweed biomass production. Biochemical observations on protein, carbohydrate and lipid contents of different species of nutritive value. Seaweeds with high content of proteins, carbohydrates and lipids can be recommended for food and feed formulations after subjecting them to toxicological studies. The study on monthly/seasonal/placewise variation in biochemical composition of seaweeds will provide necessary information on the appropriate time and place of harvesting the algal species for exploiting its constituents .

Studies on the ecology and productivity of saline lagoon

A perusal of the literature shows that most of the earlier works on the ecology and productivity from the Indian waters have been confined to the estuarine ecosystms and contiguous neritic and oceanic water bodies. Although some information is available on certain aspects of the envirornental parameters from the ‘coastal lagoon ecosystem‘, there is hardly any indepth study on the ecological and productivity problems from "derlict saline lagoonal environment" in India . In view of this, the researcher undertook a study on the subject "ecology and productivity“ of a typical “coastal saline lagoon"(Pilla;headan lagoon) situated along the southeast coast of India for a period of two years!-N11, 1982 to June, 1984) , and the results of the investigations are embodied in the present thesis entitled "studies on the ecology and productivity of saline lagoon‘.

Studies on the ecology of zooplankton of cochin backwaters(a tropical estuary)

Ecology is the study of systems at a level in which individuals or whole organisms may be considered elements of interaction, either among themselves, or with a loosely organised environmental matrix. Systems at this level are named ecosystems, and ecology, of course, is the biology of ecosystems" (Hargalef, 1968). This thesis includes principally, a study on the ecology of zooplankton of the Cochin backwaters conducted during the years 1971-72. This monsoonal estuarine system is particularly interesting, since it exhibits a wide range of variations in its environmental conditions which is naturally reflected in the fauna also. Several publications on various aspects of its hydrobiology have come out in the recent past. But studies on the zooplankton of the estuary have mostly been discontinuous either in space or time or restricted to its groups

Population Biology And Ecology Of Artemia From Salinas Of South East Coast Of India

This thesis deals with the population characteristics of Artemia and the effect of different environmental parameters on the different stages of Artemia in a salina at Tuticorin, south east coast of India. The present investigation was carried out from 1985 to I987. The study was initiated by undertaking a survey to find out suitable Artemia habitats along the south east coast of India and a perennial salina with an area of 0.25 ha was selected at Karapad (Tuticorin). Weekly samplings were made for two full calender years (1986-87) to collect the different stages of Artemia population as well as the different environmental parameters. The thesis comprises of the following sections: Introduction, materials and methods, systematics, biology and distribution of Artemia, results and discussion, summary and bibliography. The section on results and discussion gives the characteristics of Artemia population in the salina, the seasonal variations of different environmental parameters in the salina and their effects on different stages of Artemia population. Description of an experiment conducted to show the sudden changes of salinity on different stages of Artemia is also given as a separate section.

Studies on The Ecology And Production of Algae in Prawn Culture Systems

Existing method of culture were largely based on empirical knowledge. Lacking a scientific basis as such methods did, they were often wasteful and suffered severe limitation. Modern methods of fish and prawn culture based on scientific research, have revolutioned the industry in recent years and not only extended its scope to cover the whole country but led to increased fish and prawn production. An understanding of the biological capability of the water in the perennial and seasonal culture ponds, and the nature and extent of the influence of the abiotic factors on the production of organisms in the primary level of food chain would contribute to effectively implement management measures in the stocking strategies and in the evaluation of economics of production of prawns. It is against this background that the present topic of investigation "Studies on the ecology and production of algae in prawn culture systems” was selected.