196 research outputs found
Stock assessment of the oceanic skipjack, Katsuwonus pelamis in Minicoy, Lakshadweep
The annual catch of skipjack tuna Katsuwonus pelamis at Minicoy fluctuated between
721.21 and 1036.5 t during 1993-'98 with an average catch of 827.61 which
constituted about 89 % of the total tunas landed by pole and line (live bait) fishery
and troll line fishery. The growth parameters estimated for skipjack tuna were
Loo= 92.6 cm and K= 0.98 (annual). Following VBGF this species is found to attain
a length of 57.8,79.6, 87.7 and 90.8 cm during the I,II,III and IV years respectively
Marine fish calendar.12. Mandapam
The Ramanathapuram District with a coastline of
261 km, covering the sea-front of Gulf of Mannar and
Palk Bay, ranks foremost in marine fish production of
Tamil Nadu State. Sustaining high levels of organic
production, the seas along the coast have lucrative fishing
grounds with greater profusion of finfishes, shellfishes,
seaweeds and other economically important organisms
Scale-free switching of polarization in the layered ferroelectric material CuInPS
Using first-principles calculations we model the out-of-plane switching of
local dipoles in CuInPS (CIPS) that are largely induced by Cu
off-centering. Previously, a coherent switching of polarization via a
quadruple-well potential was proposed for these materials. In the super-cells
we considered, we find multiple structures with similar energies but with
different local polar order. Our results suggest that the individual dipoles
are weakly coupled in-plane and under an electric field at very low
temperatures these dipoles in CIPS should undergo incoherent disordered
switching. The barrier for switching is determined by the single Cu-ion
switching barrier. This in turn suggests a scale-free polarization with a
switching barrier of 203.6-258.0 meV, a factor of five smaller than that
of HfO (1380 meV) a prototypical scale-free ferroelectric. The mechanism of
polarization switching in CIPS is mediated by the switching of each weakly
interacting dipole rather than the macroscopic polarization itself as
previously hypothesized. These findings reconcile prior observations of a
quadruple well with sloping hysteresis loops, large ionic conductivity even at
250~K well below the Curie temperature (315~K), and a significant wake-up
effects where the macroscopic polarization is slow to order and set-in under an
applied electric field. We also find that computed piezoelectric response and
the polarization show a linear dependence on the local dipolar order. This is
consistent with having scale-free polarization and other polarization-dependent
properties and opens doors for engineering tunable metastability by-design in
CIPS (and related family of materials) for neuromorphic applications
Installation of fishing net tracking buoys in deep sea multiday tuna drift gillnetters at Chennai
The deep sea multiday tuna drift gillnetters face
many risks while they engage in fishing. The cutting
and stealing of nets by fishermen of other boats
or damage of the nets by the ships is common. As
the total length of a net when set is around 5 to 6
nautical miles (nmi) and the fishing is carried out
during night, quite often the fishermen come to
know about the loss only at the time of hauling
the net. Another serious issue is the possibility of
collision with an approaching ship as sometimes
the fishing ground can be on the same track of a
ship and fishermen notice it only when the ship is
too near to them. Installation of fishing net tracking
buoy can effectively avoid these risks and enable a
hassle free fishing trip
Note on catfish landing with gravid females, male brooders and young ones at Cuddalore, Tamil Nadu
In Tamil Nadu catfish is landed mainly as a by-catch
in trawlers, drift gill netters and the hook and line
units. In 2018, the total catfish landing in Tamil Nadu
was 4165 t of which almost 90 % was contributed by
trawlers. On 22.8.2019, around 3000 kg of catfish, Arius
maculatus was landed by a ring seiner at Cuddalore,
Tamil Nadu. The catch was comprised of gravid females
and incubating males of total length ranging from 350
mm to 370 mm. Along with the catch, eggs in various
stages of development, juveniles with yolk and without
yolk were also seen in good quantity in the boat. One
gravid ovary contained 24 eggs in the right ovary and 29
in the left
Tuna live-bait fishes - their exploitation, conservation and management in Lakshadweep
The total annual catch of baitfishes form pole and line fishing areas of Lakshadweep
is estimated to be 1251. At Minicoy, the average annual catch is estimated at 9.11 and
at Agatti it is estimated to be 51 t. Data from other baitfish fishing areas such as
Suheli, Valiapani and Cheriyapani are virtually non-existent. Management options
suggested earlier include the collection of fishery data from more areas, studying the
biology and understanding the stock of exploited species, culture of suitable species
and maintaining the health of the coral reefs of the islands. Future thrust areas for
research to elucidate the factors that determine the baitfish fishery include a full
review of the existing fishery and development of a baitfish statistics collection
system
Heavy landing of tuna by multiday deep sea ringseiners at Cuddalore.
In Tamil Nadu, Cuddalore fishing harbour is known for
ringseine operation and in February 2018, the fishermen
introduced multiday deep sea ringseine for oceanic tunas
and the result was encouraging ( Sivadas et al., 2018. Mar.
Fish. Infor. Ser. T & E Ser. No.235). Now the fishermen
from neighbouring areas like Pazhayar, Kalpakkam etc
also started practising this fishing. In 2019 since July,
there were good landings by this gear. A brief account
of the landings during July and August is given below to
highlight their role in exploitation of both inshore and
oceanic tunas. In a boat the catch varied from 5 t to 30
t. Initially the catch was comprised by yellowfin tuna and
skipjack tuna
Tuna drift gillnet fishery at Chennai, Tamil Nadu- an update
The present study describes the status of multiday drift gillnet fishery
for tuna from Chennai fishing harbour based on data for the years
2016 тАУ 2017. The data is also compared with that during 1999-
2006. Both the craft and gear increased in size with consequent
extension of fishing grounds and increase in the number of days/
fishing trip. The size of the boats increased to 20-23 m OAL from
11-12 m OAL and weight of the gear from 1 to more than 6 t.
Annual average catch increased to 8523 t during 2016-2017 from
595 t during 1999-2006. Average catch per unit effort was 8310 kg
as against 730 kg during 1999-2006. Yellowfin tuna, Thunnus
albacares and Skipjack tuna, Katsuwonus pelamis were the dominant
species. The stock position of skipjack tuna and yellowfin tuna vis-├аvis
the three indicators indicated that the percentage of mature
yellowfin tuna in the catch in 2017 was 68%, fish in optimum length
35% and mega-spawners 33% whereas in skipjack tuna the
respective percentages were 99.5, 21.1 and 79.1. Problems and
prospects of multiday tuna drift gillnet fishery are also discussed
Problems and prospects of marine fisheries at Lakshadweep
The Lakshadweep sea is estimated to have an annual fishery potential of about 90,000 tonnes while the present yield is only about 6000 tonnes. ' Endowed with vast lagoons and tuna-rich oceanic waters, I fishing is an important component of the economy of Lakshadweep. Tunas form 87% of the fishery and is caught mainly by the pole-and-line technique-:-This method involves locating the tuna shoals, then attracting by chumming with live bait and water spraying, and finally, catching the fish using poles and lines with barbless hooks
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