Nitrogen and phosphorus dynamics in Nile tilapia farming in excavated rearing ponds

Anderson Coldebella,Wilson Rogério Boscolo,Antonio Cesar Godoy,André Luis Gentelini,Pitágoras Augusto Piana,Aldi Feiden,Priscila Ferri Coldebella

doi:10.33448/rsd-v9i11.9699

Abstract

The purpose of this study was to determine the total nitrogen (TN) and total phosphorus (TP) balance during intensive tilapia farming in excavated ponds. To quantify TN and TP released into the environment, the supply water, effluents at the harvest time, fish composition, feed, and sediment were analysed. The mass balance between the amount of nutrients that is inserted through the feed, which is transformed into biomass by the fish and is retained in the sediment was calculated based on dry matter. The nutrient load arriving from the supply water was calculated as a function of the concentration of TN and TP. The TN and TP dynamics during the harvesting process in three different pond sizes identified that, on average, 2.37% of TN and 2.05% of TP inserted into the system during rearing is eliminated with 10.64% TN and 37.01% TP are retained in the sediment. The TN and TP input into the system occurs through the water supply, young fish, and the feed, the latter being responsible for about 92.87% TN and 96.05% TP. The feed composition indicates that the P level of the food is above the nutritional recommendations for the species. The amount of TP accumulated in the sediments indicates that there is a need for good management practices for water quality during the rearing and sediment management period before the beginning of a new production cycle.

Highlights

Aquaculture and fishing are important sources of food and income for millions of people worldwide (FAO, 2018)
The purpose of this study was to determine the total nitrogen (TN) and total phosphorus (TP) balance during intensive tilapia farming in excavated ponds
The TN and TP dynamics during the harvesting process in three different pond sizes identified that, on average, 2.37% of TN and 2.05% of TP inserted into the system during rearing is eliminated with 10.64% TN and 37.01% TP are retained in the sediment

Summary

Introduction

Aquaculture and fishing are important sources of food and income for millions of people worldwide (FAO, 2018). Aquaculture activity has shown significant growth in recent years in the production of a healthy and nutrient-rich food (Osti et al, 2017). A trawler is used manually when the water level of the pond is 50% of its total water capacity, the net is passed through the pond several times while the water is drained, this process stirs the sediment at the bottom of the pond, rich in N and P, and causes the worsening of the quality of the effluent released into the environment (Mardini & Mardini, 2006). Due to the impacts N and P on the enviroment, it is necessary to quantify these elements released into the environment by Nile tilapia (Oreochromis niloticus) in a pond excavated for farming. The objective of this work was to characterize the water supply, the wastewater effluents, the sediment, feed, and fish in three pond size classes on how production practices affect the release of nitrogen and phosphorus into the environment

Objectives

Methods

Conclusion