187 research outputs found
Large-scale exploitation of sacred chank Xancus pyrum using modified trawl net along Rameswaram Coast, Tamil Nadu
The sacred chank, Xancus pynim is a
gregarious, large gastropod and its habitat
forms distinct chank bed. Homell as early as
1922 described the chank beds in depths of
10 to 20 metres in the Gulf of Mannar and
are considered as the most important ones in
the country although there are other chank
beds along the Gulf of Kutch and the southwest
coast of India
Sardines of the Gulf of Mannar ecosystem - fishery and resource characteristics of major species
Fishery, species diversity and resource characteristics of exploited sardine resources of the genera Sardinella were studied
during 2000-2008. Sardines were exploited by sardine gillnets, trawls and shore seine. Annual average production for the
period was 20,249 t. They formed about one fourth of the total marine fish production (77,443 t) of the region. Fishery was
supported by eight species dominated by Sardinella gibbosa, followed by S. sirm, S. albella and S. longiceps. Fishery
fluctuated widely with declining trend over the years mainly due to reduction in the fishing effort following destruction of
traditional crafts and gears during the Tsunami in 2004. Oilsardine in the fishery registered an increasing trend with wide
annual fluctuation during the period. Stock assessment studies show that the exploitation rate of major species ranged between
0.45 and 0.62, against the EMSY value of 0.72 and 0.86. This indicated that sardine resource as a whole is under-exploited,
offering considerable scope for enhancing their yield. Despite contributing a higher share to marine fish production, sardines,
along with other small pelagics, play a vital ecological role in sustaining the stock and fishery of other predatory groups
especially large pelagics by providing them a major share of their forage. They support 46 to 87% of the total food of pelagic
predators and 14 to 29% of demersal predators
Temperature and terahertz frequency dependence of the dielectric properties of Fe3O4 thin films deposited on Si substrate
The FeO/Si films are considered to be promising materials for THz
spintronic applications due to their high temperature magnetic transition and
semiconducting properties. In this article, we present the real part of the
dielectric constant () and the optical conductivity () of
FeO films of different thicknesses deposited on Si substrate
(FeO/Si) in the THz range at temperatures 2- 300 K. Although the
magnetization of the films with thickness 115 nm shows a clear change at
the Verwey transition temperature T = 121 K, their optical properties in
the THz frequency range are drastically different from each other. We have
shown that is maximum and is minimum when the
Fe/Fe ratio is equal to 0.54 which is the ratio of Fe+2/Fe+3 for
pure FeO. The reduces and increases at all
temperatures when the Fe/Fe ratio deviates from 0.54. We have
shown that a slight change in the Fe/Fe ratio can induce large
changes in the optical properties which shall have implications in the
application of the Fe3O4 films in THz spintronics.Comment: 18 pages, 6 figure
Feeding congregation of ribbonfish, Trichiurus lepturus juveniles in oceanic waters and their targeted exploitation by deepsea trawlers along the Tuticorin coast in Gulf of Mannar
Ribbonfishes supported commercial fishery at
Tuticorin prior to nineteen nineties. But reports
suggested that their stock and fishery declined
considerably thereafter. Their fishery during 2000-
2006 was represented by occasional landings of
small quantity of ribbonfish by trawls. Average
production by trawls at Tuticorin fishing harbour
during the period was 250 t. They represent about
0.7% of the total fish catch of the period
Exploited marine fishery resources off Tuticorin along the Gulf of Mannar coast
Tuticorin coast of Gulf of Mannar is endowed
with rocky bottom, coral reefs and sea grass
beds with characteristic flora and fauna. It also
acts as home for several endangered marine
mammals, sea cows and marine turtles. These
resources were exploited by a variety of gears
during 2000-2005
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