Optimal Dietary Crude Protein in Commercial Feeds for Shrimp and Halophytes in Marine Aquaponic Biofloc Systems

Abstract

Formulated diets for animals is the primary source of nutrients in aquaponic systems that need to maintain beneficial bacteria as well as for plants. Dietary protein is one of the expensive macronutrients in fish diets, especially when fishmeal is used, and it is the source of nitrogen (N) for other biotic components. Biofloc has the potential to serve as the supplement diet for shrimp and reduce the need of expensive protein. However, it is not clear if low dietary protein will be adequate to support the three organisms (animals, plants, and bacteria) in an aquaponic system operated with biofloc technology. The aim of the present study was to investigate the effect of shrimp feed with different protein concentrations (30, 35, or 40%) on water quality and the growth performance of Pacific whiteleg shrimp (Litopenaeus vannamei) and three edible halophytic plants (Atriplex hortensis, Salsola komarovii, and Plantago coronopus) in biofloc-based marine aquaponics. The experiment was conducted for 12 weeks, the plants were harvested and seedlings transplanted every 4 weeks. Dietary protein content did not influence shrimp growth in the current study, indicating that feeds with lower protein concentrations can be used in biofloc-based marine aquaponic systems. During the early and mid-stages of cultivation, plants grew better when supplied diets with higher protein concentration, whereas no differences were observed for later harvests. Hence, for maximum production with mature systems or in the scenario of high concentration of nitrate, providing a higher protein concentration feed in the early stages of system start-up, and switching to a lower protein concentration feed in later stages of cultivation was recommended.

Environmental pH and Supplemental C Exert Little Impact on Shrimp, but Profound Impacts on Plants in Marine Aquaponics

“…After the first harvest (day 28), the concentration of TAN and NO2increased in all treatments in the present study (Figure 5 C and D), which is similar to results from other studies [21,83]. Chu and Brown [9] reported that the concentration of nitrogenous compounds increased after harvests, but the concentration of TAN did not increase to a hazardous level at the late stage, and the concentration of NO2remained within safe ranges throughout the experiment.…”

“…In the present study, the potential reasons for TAN and NO2increasing beyond the safe range after harvest might be the frequency of inoculating probiotics, the C/N ratio, animal to plant ratio, the water source, or the ionic composition in the water. Chu and Brown [9,21,31] inoculated probiotics on a regular basis and maintained the C/N ratio at 12 and 15, which provided a better environment for heterotrophic bacteria to assimilate nitrogenous compounds. The lower C/N ratio and discontinuous inoculation in the present study could be one of the causes of the high concentration of TAN and NO2 -.…”

“…the probability of a pH conundrum in marine or brackish water aquaponic systems may be less than in freshwater systems. Nevertheless, Chu and Brown [9,21] mentioned that pH was a possible factor influencing growth of the halophytes they evaluated. The ideal range of pH for an integrated system that includes aquatic animals, plants and bacteria in marine aquaponics remains largely unknown and may significantly influence compatibility of biotic subsystems and significantly influence outputs.…”

Evaluation of the Optimal Protein Required in Granulated Microdiets for Rockfish (Sebastes schlegeli) Larvae

“…The high demand for energy for catabolism rather than protein deposition will result in a poor growth rate of fish when diets are excessively high in protein [ 28 ]. The decrease in growth as a result of high protein may be caused by the build-up of toxic nitrogen compounds, which can affect the growth of rockfish [ 29 , 30 ]. Therefore, the protein requirement of rockfish larvae fed granulated microdiets was estimated to be 54.0% according to the broken line analysis of weight gain of larval fish.…”

The effect of swimming activity and feed restriction of rainbow trout (Oncorhynchus mykiss) on water quality and fish‐plant growth performance in aquaponics

“…In commercial aquaponic setups, fish may undergo feed restrictions to maintain a balance between the aquaculture and hydroponic components (Chu & Brown, 2022). These strategies, aimed at controlling growth, preventing disease, preserving water quality, and enhancing energy efficiency, can include periodic fasting (Robaina et al, 2019).…”