Need for diversification of coastal aquaculture

There is large potential for coastal aquaculture in the vast stretches of shallow coastal waters, creeks, bays lagoons and mudflats along the northeast coast of India comprising Andhra Pradesh, Orissa and West Bengal. Considering the good prospects for ariculture along the Indian coasts, the Central Marine Research Institute has carried out research and developed techniques for the culture of several groups of cultivable organisms like prawns, finfishes, crabs, the molluscan shellfishes like oysters, mussels, clams, pearl oyster and cephalopods, holothurians and seaweeds

Molluscan Fisheries of India

Molluscs form valuable fisheries in various parts of the coasts of India providing shellfish as food and as source of lime, pearls and decorative shells, as constituents of medicinal preparations etc. The present status of exploitation of molluscan resources in the country and the progress made in researches on the culture of bivalve molluscs are presented and the possibilities for better utilization of the resources by proper exploitation are emphasized. Molluscan resources exist at innumerable places along the coasts of India and are exploited in varying degree of intensity forming valuable fisheries. The fisheries and biological aspects of the major species of molluscs of economic importance have been studied only at a few areas in the last few years. Exploitation of the available molluscan resources it is possible for India to increase production substantially from the present level which will provide greater quantities of wholesome sea-food to meet internal demand and requirements of export industry

Biological Fouling at Port Kakinada, Godavari Estuary, India

Results of fouling investigations conducted for the first time at the fastdeveloping intermediate port of Kakinada in Godavari Estuary, Andhra Pradesh during 1983-1984 are presented. The fouling species collected from different structures and craft were identified and listed. Several of the species are reported for the first time from the area and some are new records to the Bay of Bengal. The main species are: the serpulid, Mercierella enigmatica; the barnacle, Balanus amphitrite; and the bryozoans, Electra bengalensis, Membranipora amoyensis, A lderina arabianensis, and Victorella pavida. Panel tests (timber and glass; short- and long-term) were conducted at two selected stations (Station I: Kakinada canal, port area; Station II: new fishing harbor) with widely differing hydrographical conditions. The data obtained for one year are presented. Variations in the nature and composition of the fouling communities were found between the two stations. Station I, subjected to extreme salinity fluctuations, typically supported a low number of highly tolerant (estuarine) species, whereas a high number of species and a more complex community structure were found at the more stable Station II. Data on seasonal settling patterns, fouling biomass fluctuations, and growth rates of important species are given and relevant comparisons made with other Indian harbors

Commercial trawl fishery off Madras coast during 1980-'89 with acomparative account of the catch trend of shrimp and fish trawlers during 1989-91

Introduction of commercial trawling and expansion of the fishing fleet to exploit the ground fishes and prawns along the coast have resulted in considerable development of mechanised fisheries sector. The trawlers operated from Madras base comprise of four different overall length groups, 9.5-10 m, 11 m, 12 m and 13 - 14 m (the conventional 32', 36', 40' and 45') with the horsepower varying between 90 and 120. Landings increased with effort over the years, from 1,416 t in 1980 a steep rise in production to 16,342 t has occurred in 1987 and there has been a further increase to 23,953 t in 1989. The average annual fish production during 1985-'89 was 14,162 t which is almost thrice that in the period 1980-'84 (4,796t). The CPUE has doubled to 369 kg in 1987compared to earlier years and has risen steadily with a maximum of 565 kg in 1989. The highest quantity of prawns (64%) is caught in short trip shrimp trawlers from depths of 15-30 m. The commercially important fishes like threadfin breams, ribbon fishes, goatfishes, barracudas, silverbellies and whitebaits are caught in maximum quantities in short trip shrimp trawls. Seasonal abundance of the resources show that the best catches were got in the third quarter followed by fourth quarter during the period 1980-'89

On a class of translation planes of square order

AbstractA class of translation planes of order q2, where q = pr, p is a prime, p ⩾7, p ≠± 1 (mod 10) and r is an odd natural number is constructed and the translation complements of these planes are determined. A property shared by all these planes is that the translation complement fixes a distinguished point and divides the remaining distinguished points into two orbits of length q and q2 − q. The order of the translation complement is rq(q − 1)2 except for q = 7 and q = 13. The translation complements of these exceptional cases are also briefly studied. The class of planes considered in this paper are distinct from the classes of translation planes of S.D. Cohen and M.J. Ganley [Quart. J. Math. Oxford, 35 (1984) 101–113]

Annual reproductive cycle of the wedge clam, Donax cuneatus Linnaeus

The venerid clam Venus mercenaria of the temperate waters is known to have a distinct annual reproductive cycle, gametogenesis taking place during the autumn and winter and spawning between July and September (Loosanoff, 1937). Studies on the reproductive activity of the economically important clams of the family veneridae of the Indian coasts have received some attention. Hornell (1922) has observed that in Meretrix casta spawning takes place twice a year, during April- May and September on the east coast. Abraham (1953) and Durve (1964) have found that M. casta in the Adyar estuary and Mandapam fish farms spawn several times a year. In the estuarine clam, Katelsia opima, Rao (1951) has observed that gametogenesis takes place between April and August and' that spawning which commences in December is completed in January. The reproductive periodicity of the clams of the family Donacidae which occur in fair abundance along the Indian coasts has not been studied in detail except for the observations of Nayar (1955) who has stated that Donax cuneatus of the Palk Bay spawns between January and April and of Alagarswamy (1967) who very recently reported prolonged spawning from November to June in D. faba from Mandapam coast. The annual reproductive cycle of D. cuneatus of the Madras coast has been studied in the present work based on the seasonal gonadal changes of the adult clams

Eggs and early developmental stages of Hilsa kelee (Cuvier)

A type of clupeiod fish eggs 1.005-1.065 mm in diameter with six or seven oil globules recorded in the plankton off Madras coast from February to April and in December in 1967 and in January and March in 1968 have been ascribed to Hilsa kelee (Cuvier) based on the structure of the eggs and larvae hatching from them, the simultaneous occurrence of ripe fish of the species in inshore waters of Madras and coincidence of myotome number of larvae with the number of vertebrae in adult fish. The newly hatched pro-larva has ellipsoidal yolk sac, thirty six pre-anal and six or seven post-anal myotomes and small black spots on the dorsal side of the pro-larva. The three day old pro-larva has three pairs of rudimentary gills, well-developed pectoral fins, small black streaks on the gut and caudal fin rays and 42 or 43 myotomes. The eggs appear to tolerate a fairly wide range of salinity between 26.22 %. and 35.62%,

Taxonomy of Indian oysters

There has been considerable disagreement on the identity of oysters due to the large variations in shape, size, texture and colour of shell which are very much influenced by the substratum and ecological conditions. As many as hundred species of living oysters and five hundred species of extinct ones were recognized initially (Korringa, 1952). Later it has been realized that most of the species were not valid

IX Other Commercial Molluscs

In addition to the moUuscan species dealt with in the preceding chapters, there are several others which are also of commercial value but have not so far received much attention from biologists in our country. In this chapter an account is given of what is known about the identity, habits, biology, distribution and utilization of these shell-fish

VI pearl Oysters

Pearls are formed in a number of species of molluscs viz., the pearl oysters, window-pane oysters, edible oysters, fresh-water mussels, abalones, chanks, topshells, turban shells etc. Pearls formed in some of the pearl oyster species are valued very highly as gems because of their excellent shape, quality and lustre. Pearl oysters enjoy a world-wide distribution occuring in almost all the seas of the tropical belt. Six species of pearl oysters are known from the Indian coasts viz. Pinctada fucata (Gould), P. margaritifera (Linnaeus), P. chemnitzii (Philippi), P. sugillata {Ree\e), P. anomioides (Reeve) and P. atropurpurea (Dunker). Of those, P. fucata which occurs in extensive beds in the Gulf of Mannar and to a much less extent in the Gulf of Kutch is commercially very important being the source of the 'Oriental pearls' or 'Lingah' pearls of great renown. P. fucata occurring in the Persian Gulf and off the coasts of Ceylon also supports excellent fisheries for natural pearls. The Indian pearl fisheries have been famous since ancient times for the most beautiful pearls they yield. The other five species of pearl oysters on the Indian coasts arc not of any importance as their pearl yield is low or the pearls produced by them are not of high quality