54 resultados para Deep water formation


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Majority of the prawn catch of the Kerala coast comes from the inshore regions within the 10 fathom line. A bottom deposit formed of fine mud rich in humus is found to be the ideal condition for the penaeid prawns. Similarly the lobster is observed in large numbers at localised areas very near the coast in the crevices of rocks. Though it has been observed that prawns and lobsters exist in deep water as well under different conditions, our knowledge about these forms along the Indian coasts is very scanty, being restricted to the works of Spence Bate, Alcock, De Man and Ramadan. Recently, during the cruises of the University Research Vessel Conch off the Kerala Coast (1958-1963) two species of deep water prawns and one species of lobster were collected from depths 100 - 180 fathoms. Of these, Penaeopsis philippi is found in large numbers occupying an almost continuous bed extending from Anjengo to Mangalore, while P. rectacutus has a restricted appearance between Cochin and Calicut. However, some sort of year to year variation has also been observed regarding the abundance of the species at various stations. Peurulus sewelli has a more restricted distribution, the maximum number being found between Puvar and Cochin. Attempt has been made to correlate the occurrence of the species with the hydrological conditions at the bottom and the nature of the substratum. It is observed that Peurulus sewelli occupies a more or less hard bed formed of sand with shell fragments or stones and small percentage of silt, the bottom temperature at the stations varying from 11°C to l4°C. P. sewelli is a more or less permanent inhabitant of the edge of the continental shell off the Kerala Coast worthy of attention for detailed investigation with a view to explore the possibilities of commercial exploitation.

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Fish culture in deep-water-rice (DWR) environment using net pen and polder systems was evaluated. In net pen rohu and Thai silver barb were cultured, whereas a 5-species combination (rohu, mrigal, common carp, grass carp and Thai silver barb) were cultured with BR3 rice variety and DWR. Boro-fish production system produced 2.8 t/ha of fish and 7.33 t/ha of rice in polder system with 5-species combinations.

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The pink shrimp, Haliporoides triarthrus, is an important species in the deep-water shrimp fishery in Mozambique. Total catches are in the range of 1,500 to 2,700 tons, with the pink shrimp accounting for 70-90%. Estimates of growth parameters and of natural mortality are used for a preliminary assessment of the fishery, based on length-structured virtual population analysis and yield-per-recruit analyses. With an arbitrarily chosen terminal fishing mortality F, the results indicate a situation of overfishing, but realistic parameters must be acquired in order to diagnose the state of the stock

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Catch and effort data and some biological characteristics of the deep water spiny lobster P. delagoae collected between August 1980 and December 1981, are presented. The work was conducted on board a commercial vessel off the coast of Mozambique.

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From 1976 to 1979 tunas of Mozambique were studied for about 40 months using seven research vessels. The main purpose of survey was not to study these resources therefore part of the information is poor and incomplete. During these three years, there were about fourteen months for experimental logline fisheries of deep-water tunas. This work corresponds to a bilateral cooperation program with USSR.

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Catch and effort data and some biological characteristics of the deep water spiny lobster P. delagoae were presented.

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The deep-water shrimp were already studied many years ago, but their commercial fishing on large scale, only developed from the seventies. Two Luso-U.S. fishing companies (1966), and a Luso-South African company (1963- 1968), dedicated to the fishing of deep-water crustaceans, including Haliporoides triarthrus species (Araújo, 1973). Also Champion (1973) described commercial catches of Plesiopenaeus edwardsianus, Aristaeomorpha foliacea and Haliporoides triarthrus in the waters of Mozambique. The first Spanish vessels began fishing activity in 1968 (Freitas and Araújo, 1973) but all of these companies captured mainly penaideos on the continental shelf.

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The major task in hand at the beginning of the year was the Deep Water Fishing Survey in Uganda waters. This has continued throughout the year with varying, lm generally, not particularly encouraging, results. A full account is given in paras. 33 to 67 of this Report. The new method of marking Tilapia was introduced at the beginning of the year, and, apart from delays resulting from the delivery position of marking materials, has gone ahead steadily. The improvement in results expected from this method was already evident after only nine months' work, and information has been obtained which never was-nor could have been-obtained by the old method of marking. A full account is given in paras 114 to 133.

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This work is based on the analysis of 420 planktonic samples of 7 oceanopraphic cruises distributed over the Argentine, Uruguayan and South brasilian continental shelf (SW Atlantic ocean), as well as from some oceanic sectors, adjacent to the continental slope. Vertical hauls were performed in all stations from 100 m depth to surface, except in the Walter Herwig cruise (where vertical hauls were predominantly performed out of slope sectors, between 300 and 500 m depth to surface) and Productividad cruise in which only surface waters were hauled. A list of 27 species are determined, corresponding to 5 families: Iospilidae (3 species), Lopadorrhynchidae (4), Alciopidae (9), Typhloscolecidae (5) and Tomopteridae (6). Larvae and epitokous forms of benthonic species are not taken into account. The genus Iospilus is revised, Pariospilus and Iospilopsis being considered their synonyms; the identity of Pariospilus affinis Viguier is maintained, being transferred to the genus Iospilus. The species Vanadis studeri Apstein is redescribed and its synonymy is established. The taxonomic value of the apical glands of Tomopteris species is discussed and some specimens are found to coincide with T. kefersteini in relation to the mentioned glands. All the species found in this work are described and illustrated, a systematic key being added for their identification. Considering the vertical nature of the hauls, it was not possible to specify the habitats of the different species; for this reason they are grouped as species from subtropical and subantartic areas of influence. The first group, made up of 17 species, shows and evident graduation in its latitudinal distribution, some of them being more restricted in their distribution than the others. The second group, of 4 species, is found south to the tropical convergence, in transitional waters, towards cold sectors. The third group, of 6 species, is found to be distributed all along the continental shelf, in subtropical and subantartic regions, and extending their distribution northwards, possibly related to deep water levels. The general scheme is coincident with the distribution of other planktonic groups (Copepods, Euphausiids). As a general feature, neither coastal nor shelf water specimens of pelagic Polychaeta were found, with exception of T. septentrionalis. A comparison with the results in Tebble's paper (1960) in the southwest Atlantic ocean is made, 12 of our species being coincidently found in the same hydrological area by that author. The drift of the main water masses of the South Atlantic ocean is accepted as a possible cause for the distribution of the pelagic Polychaeta of the southwest Atlantic regions.