Adaptation of "Biofloc" Aquatic System for Polyculture With Tilapia (Oreochromis Sp.) and River Prawn (Macrobrachium Sp.)

Abstract

Aquaculture is a productive activity in economic growth due to market productivity which supports many Ecuadorian communities. However, exotic species has been the basis of this activity without considering the endemic and mega-diverse component of Ecuador. On the other hand, current aquaculture systems use a lot of water, generating discharge of nitrogen and phosphorus, causing a negative impact on natural watersheds. The present investigation focused on the diversification of aquaculture production and environmental care, through the polyculture of tilapia and river prawn, in a Biofloc system, which allows reducing the use of water, space, and food, taking advantage of all the nutrients of the aquatic environment without generating pollutant residues, from a carbon-nitrogen ratio of 20:1. The research project was developed under laboratory conditions at 2.728 amsl, for 8 weeks in pre-breading stages. Two factors were established in the study: type of culture (monoculture and polyculture) and production systems (traditional and biofloc), with three replicates. In the Biofloc system, the environmental variables such as temperature, pH, and oxygen did not show any significant differences between treatments (p≤0.05), while conductivity and total suspended solids increased during the test, and the nitrification processes stabilized at day 28 with values of 0.06±0.01 and 0.35±0.09 ppm in ammonium and nitrite respectively. The bacterial load was higher in the Biofloc system (113.66x103 CFU/ml) with predominance of Bacillus sp. and Pseudomonas sp. The bioflocs showed greater volume in polyculture (17.62 ml/L) and 26% of protein. Under these considerations, the best productive performance was detected in the Biofloc polyculture with a total productivity of 142.86g/m2 (p≤0.05). Therefore, diversification of species, types and culture systems are viable for aquaculture in Ecuador, generating an interaction between the chemical and biological components, allowing productive processes to be sustainable.

Effects of C‐N ratio on growth, survival and proximate composition of Macrobrachium rosenbergii post larvae reared under a corn starch based zero‐exchange brackish water biofloc system

“…Biofloc-based systems often consist of various live and dead plankton species, and in this study, ciliates, rotifers and nematodes were identified and quantified. These zooplankton groups increased in abundance with increasing C-N ratios, which is in agreement with other studies (Asaduzzaman et al, 2010;Gallardo-Collí et al, 2019;Manan et al, 2017;Reinoso et al, 2019).…”

“…After 20 days, 50 ml water samples were collected from each tank to determine the zooplankton communities. The samples were preserved in 4% buffered formalin (Emerenciano et al, 2013;Thompson et al, 2002), and 1 ml was placed on Sedgwick-Rafter counting cell (Azim & Little, 2008), and the amount of ciliates, rotifers and nematodes were identified and counted (Gallardo-Collí et al, 2019;Hosain et al, 2013;Manan et al, 2017;Reinoso et al, 2019;Santhanam et al, 2019;Smith, 2001) A total 300 fields of SR-cells were counted for each sample in triplicate for each tank.…”

Microbial Community Response to Carbon-Nitrogen Ratio Manipulation in Biofloc Culture

“…The recommended C:N range to promote biofloc formation is from 11 to 20:1 (Ebeling et al 2006;Avnimelech 2012;Pérez-Fuentes et al 2016). Some studies used 15:1 C:N ratio (Kasan et al 2018;Cang et al 2019) while others adapted the maximum recommended ratio of 20:1 (de Souza et al 2019;Reinoso et al 2019). In practice, up to 20:1 is the recommended C:N ratio on the first three months of culture followed by a reduction to around 15:1 at the latter part of the culture to manage the decline of pH and production of settled biomass (Pérez-Fuentes et al 2016).…”