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BIOECONOMIC MODELLING OF A THREE-SPECIES FISHERY WITH SWITCHING EFFECT
Samanta, G.P.,Manna, Debasis,Maiti, Alakes 한국전산응용수학회 2003 Journal of applied mathematics & informatics Vol.12 No.1
This paper aims to study the problem of combined harvesting of a system involving one predator and two prey species fishery in which the predator feeds more intensively on the more abundant species. Mathematical formulation of the optimal harvest policy is given and its solution is derived in the equiblibrium case by using Pontryagin's Maximum principle. Dynamic optimization of the harvest policy is also discussed by taking E(t), the combined harvest effort, as a dynamic variable. Biological and bioeconomic interpretations of the results associated with the optimal equilibirum solution are explained. The significance of the constraints required for the existence of an optimal singular control are also given.
DYNAMICAL MODEL OF A SINGLE-SPECIES SYSTEM IN A POLLUTED ENVIRONMENT
Samanta, G.P.,Maiti, Alakes 한국전산응용수학회 2004 Journal of applied mathematics & informatics Vol.16 No.1
The effect of toxicants on ecological systems is an important issue from mathematical and experimental points of view. Here we have studied dynamical model of a single-species population-toxicant system. Two cases are studied: constant exogeneous input of toxicant and rapidly fluctuating random exogeneous input of toxicant into the environment. The dynamical behaviour of the system is analyzed by using deterministic linearized technique, Lyapunov method and stochastic linearization on the assumption that exogeneous input of toxicant into the environment behaves like ‘Coloured noise’.
Dynamical model of a single-species system in a polluted environment
G. P. Samanta,Alakes Maiti 한국전산응용수학회 2004 Journal of applied mathematics & informatics Vol.16 No.-
The effect of toxicants on ecological systems is an important issue from mathematical and experimental points of view. Here we have studied dynamical model of a single-species population-toxicant system. Two cases are studied : constant exogeneous input of toxicant and rapidly fluctuating random exogeneous input of toxicant into the environment. The dynamical behaviour of the system is analyzed by using deterministic linearized technique, Lyapunov method and stochastic linearization on the assumption that exogeneous input of toxicant into the environment behaves like ‘Coloured noise’.
Sarma Nittala S.,Baliarsingh Sanjiba Kumar,Lotliker Aneesh Anandrao,Pandi Sudarsana Rao,Samanta Alakes,Srichandan Suchismita 한국해양과학기술원 2023 Ocean science journal Vol.58 No.1
Green Noctiluca scintillans (NSG) is a mixotrophic dinofagellate that frequently forms intense blooms in the north Indian Ocean, especially in the northeastern Arabian Sea during winter. This study investigates the conducive conditions and drivers associated with NSG blooms and proposes signifcant models for estimating NSG based on in situ (time-series) study during the bloom cycles. Two critical factors with regard to the blooms, i.e., phytoplankton abundance and sea surface temperature (SST), were examined. The frst phase of heterotrophy dominance was when moderate blooms up to~ 2.26× 104 cells 1–1 occurred and, when NSG cells per unit chlorophyll-a (chl-a) increased, SST decreased up to~24.5 ºC. The bloom intensity was proportional to the feed (diatoms/phytoplankton) availability and the degree of cooling (by the winter convection, i.e., nutrient enrichment). In the second phase of autotrophy dominance, intense blooms up to 1.9× 105 cells l −1 occurred and NSG cells per unit chl-a fell, when the SST increased. During this period, bloom intensity was proportional to the degree of warming, i.e., nutrient and physiological stress. Phytoplankton are related to NSG by a single linear model through this SST cycle and is likely the NSG’s essential biotic precursor. Attention is then focused on developing a remote sensing refectance (Rrs) model for efcient synoptic monitoring of NSG using ocean color satellites. The Rrs band product ratio, a new metric, in combination with SST, notably modelled NSG abundance, which may be of potential routine application.
Sanjiba Kumar Baliarsingh,Rashmin Dwivedi,Aneesh A. Lotliker,Reeta Jayashankar,Biraja Kumar Sahu,Suchismita Srichandan,Alakes Samanta,Chandanlal Parida,Tummala Srinivasakumar,Kali Charan Sahu 한국해양과학기술원 2018 Ocean science journal Vol.53 No.1
The present paper reports on the phenomenon of pinkish-red discoloration of the nearshore water of Puri, Odisha on 12th May 2016. Many local newspapers covered this event, as Puri city is a major tourist and pilgrimage place on the east coast of India. Field observations were carried out in order to provide a scientific basis to the event and to elicit possible causes of this discoloration. Taxonomic analysis of the phytoplankton samples revealed the dominance of red colored dinoflagellate species Gonyaulax polygramma, contributing 90% to total phytoplankton population. The localized concentration of G. polygramma was responsible for the pinkish-red discoloration of nearshore water. The exact factor that lay behind the genesis of this bloom could not be delineated due to the short period of its persistence. But two factors - upwelling and anthropogenic nutrient influx - can be viewed as the main cause for this ephemeral bloom. Non-hypoxic conditions in the coastal water following the ephemeral bloom event indicated no significant risk of ecological deterioration to the ambient medium.