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 CuInP2_2S6_6

Using first-principles calculations we model the out-of-plane switching of local dipoles in CuInP$_2$S$_6$ (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 $\sim$ 203.6-258.0 meV, a factor of five smaller than that of HfO$_2$ (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 – 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-àvis 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