Application of modeling as a study tool to determine the number of farfante farms for Farfantepenaeus paulensis cultivation in shallow bays in the Lagoa dos Patos estuary, RS
Author: Ângela Machado Milach (Currículo Lattes)
Supervisor: Dr Ronaldo Cavalli
Co-supervisor: Dr Luis Henrique da Silva Poersch
Abstract
In aquaculture, the flow of nitrogen can act as an important indicator of the interactions between crops and the aquatic ecosystem. Understanding these interactions encompasses knowledge of ecological processes and crop management strategies. In this work, modeling is used as a signaling tool for the possible effects of this activity. This instrument, when applied to aquaculture, aims to improve the understanding of the processes involved, in addition to allowing momentarily stratify the causal relationships between variables, coming into existence as an artificial world and reflecting a vision of the real world. In order to create scenarios for the cultivation of the pink shrimp Farfantepenaus paulensis in pens based on the nitrogen flow in the water column, a mathematical model was built.This was used to estimate the release of nitrogen by the enclosures and the maximum number of these production units that the coves, Korea and Porto do Rei, in the Lagoa dos Patos estuary, RS, would hold, without compromising the water quality and sustainability of the system. For the construction of the numerical model, the software STELLATM v. 9.0.1 and the model was run at the time step of 1 (DT). For the calibration of the model, information about the shrimp Litopenaeus vannamei and F. paulensis were used. In addition, field measurements such as temperature, salinity, current velocity data and nitrogen concentrations were obtained from historical data. The model was validated by monitoring shrimp cultivation in pens in Ilha dos Marinheiros, Rio Grande, RS.The values of the environmental variables proved to be favorable for the production cycle to be successfully completed. Through simulations, the model's predictions were then compared with the crop data. The correlation between predicted and observed data was 0.99. Several scenarios were built to provide the number of pens for the inlets according to the different situations presented. The simulations performed by the model indicated that it is possible to insert up to 509 pens in the Korean cove and 683 in Porto do Rei according to the chosen values. However, pens must be placed in the aquatic environment based on a more conservative scenario taking into account the precautionary principle. Thus, the most suitable would be to place the pens in a scenario of current speed of 0,01m / s and 40% of the influence of the mesh and its clogging state, thus enabling the placement of 29 pens in Korea and 39 in Porto do Rei. The model results indicate based on their simulations that shrimp farming in pens it would not be a source of problems for protected coves, as long as the number of units does not exceed the capacity of assimilation of the environment, with regard to the release of nitrogen in the water column. The model and its simulations were valuable and promising tools for predicting nitrogen-based analysis scenarios, expanding the understanding of the behavior and interaction of F. paulensis cultivation and the aquatic environment. Thus,the present work serves as a basis for future studies that aim to estimate the carrying capacity of water bodies in which aquaculture is practiced.