Overview of elasmobranch fisheries of West Bengal in 2018

Elasmobranch fishery of West Bengal comprises of sharks, rays, guitarfishes and skates. Due to demand in the national and international market, the fishery has gained importance though it is not a targeted resource. The catch data showed that the fishery is in a declining phase since 2016. The estimated landing of elasmobranchs (3799 tonnes) has shown a further decrease of 12.6% during 2018 in West Bengal compared to 2017. Sharks form the major portion (48%) of the elasmobranch fishery followed by rays (40%) and guitarfishes (12%) during 2108 in West Bengal. The fishery flourished more during the first (January-March) and last quarter (October- December)of the year. Maximum catch of sharks have been observed in October followed by February. The gear-wise landings of sharks showed that multiday trawlers contributed 81% of the shark landings followed by mechanized gill netters (17%) and the remaining 2% by inboard gill netters. Maximum catch of rays have been observed during June followed by January and October. The rays were mainly exploited by trawlers (76%) followed by hook and lines (15%) and gill netters (8%). Maximum catch of guitarfishes was observed during January followed by August and February. Guitarfishes are landed mostly by trawlers (91%) followed by gill nets (9%). The elasmobranch resources in West Bengal are very diverse in nature. However, there is a continuous decline in the landings which could be detrimental in future if the resources are not managed properly. Hence, it is recommended to follow good management practices to ensure long term sustainability of the resources

5 GHz Band Vehicle-to-Vehicle Channels: Models for Multiple Values of Channel Bandwidth

In Sen and Matolak\u27s earlier paper, 5-GHz-band vehicle-to-vehicle (V2V) channel models were presented for channel bandwidths of 5 and 10 MHz. In this paper, we provide additional tapped delay line models for bandwidths of 1, 20, 33.33, and 50 MHz based upon the data used in Sen and Matolak\u27s paper. We provide tables of channel parameters for five types of V2V channel classes and also include example tap correlation coefficients. Root-mean-square delay spread values are summarized, as are values of bandwidth for which the channel frequency correlation takes values of 0.7 and 0.5. As with the results from Sen and Matolak\u27s paper, these models should be useful for designers in future V2V communication systems

Deformities recorded in fishes

During regular field visits to Digha Mohana Fish landing centre (West Bengal, India) during August, 2018 to October, 2019 period, five abnormal fishes were collected and are recorded as given below. Deformed specimens of Brevitrygon walga and Pateobatis bleekeri (Rays), a deformed embryo of the shark Scoliodon laticaudus, guitarfish Glaucostegus granulatus and pomfret Pampus argenteus were recorded among the commercial landing. The rays were found to have rostral deformit

Analysis of the Three-dimensional Superradiance Problem and Some Generalizations

We study the integral equation related to the three and higher dimensional superradiance problem. Collective radiation phenomena has attracted the attention of many physicists and chemists since the pioneering work of R. H. Dicke in 1954. We first consider the three-dimensional superradiance problem and find a differential operator that commutes with the integral operator related to the problem. We find all the eigenfunctions of the differential operator and obtain a complete set of eigensolutions for the three-dimensional superradiance problem. Generalization of the three-dimensional superradiance integral equation is provided. A commuting differential operator is found for this generalized problem. For the three dimensional superradiance problem, an alternative set of complete eigenfunctions is also provided. The kernel for the superradiance problem when restricted to one-dimension is the same as appeared in the works of Slepian, Landau and Pollak. The uniqueness of the differential operator commuting with that kernel is indicated. Finally, a concentration problem for the signals which are bandlimited in disjoint frequency-intervals is considered. The problem is to determine which bandlimited signals lose the smallest fraction of their energy when restricted in a given time interval. A numerical algorithm for solution and convergence theorems are given. Orthogonality properties of analytically extended eigenfunctions over L2(−∞,∞) are also proved. Numerical computations are carried out in support of the theory

The 5 GHz Airport Surface Area Channel: Part II, Measurement and Modeling Results for Small Airports

This paper describes results from a channel measurement campaign performed at several small airports in the U.S. in the 5-GHz band. This paper is a companion to another paper, which describes channel models for large airports. We classify the small airport surface channel into three propagation regions based upon different delay dispersion conditions. The channel characteristics of these regions in the delay and frequency domains are discussed with examples. We provide empirical stochastic channel models (of different bandwidths) to accurately represent the channel on the airport surface area for all propagation regions. The models are provided in the form of tapped delay lines, and complete statistical tap descriptions are given. Several key observations, including the presence of severe amplitude fading, some correlated scattering, and statistically nonstationary behavior, are also discussed

Vehicle-Vehicle Channel Models for the 5 GHz Band

In this paper, we describe the results of a channel measurement and modeling campaign for the vehicle-to-vehicle (V2V) channel in the 5-GHz band. We describe measurements and results for delay spread, amplitude statistics, and correlations for multiple V2V environments. We also discuss considerations used in developing statistical channel models for these environments and provide some sample results. Several statistical channel models are presented, and using simulation results, we elucidate tradeoffs between model implementation complexity and fidelity. The channel models presented should be useful for system designers in future V2V communication systems

New record of the giant freshwater whipray, Urogymnus polylepis from West Bengal waters, east coast of India

The giant freshwater whipray, Urogymnus polylepis belongs to the family Dasyatidae, the most species-rich family of the order Myliobatiformes comprising 19 genera and 89 species (Last et al., 2016a). Whiprays (subfamily Urogymninae) mostly live in marine environments worldwide in both tropical and temperate waters, while only a few species penetrate into estuarine and freshwater environments due to their remarkable physiological adaptability (Last et al., 2016b). Urogymnus polylepis is one of such species which primarily lives in freshwater environment; however there are records from brackish waters and even from marine coastal habitats (Last et al., 2010; Vidthayanon, et al. 2016)