# Water-Use Efficiency and Physiological Responses of Juvenile Northern River Shrimp (Cryphiops caementarius) Cultured in Biofloc Systems Using Molasses and Chancaca as Carbon Sources

## TL;DR

This study shows that using biofloc systems with molasses or chancaca can significantly reduce water use in shrimp farming while maintaining growth and offering environmental benefits.

## Contribution

The study introduces biofloc technology with specific carbon sources as a sustainable method for culturing an endangered freshwater shrimp species.

## Key findings

- Biofloc systems reduced water exchange by 81.6% without affecting shrimp growth.
- Molasses-based biofloc systems increased stress-related Hsp70 protein levels.
- Biofloc systems maintained suitable water quality and biological performance.

## Abstract

Shrimp farming is an important source of food and income, but it often requires large amounts of water and can generate waste that negatively affects rivers and lakes. This study explored biofloc technology as a water-saving strategy for rearing juvenile northern river shrimp (Cryphiops caementarius), an endemic freshwater species from Chile that is currently classified as vulnerable. Biofloc systems improve water quality by recycling waste nutrients into microbial aggregates that remain suspended in the water. Two natural sugar-based carbon sources, molasses and chancaca, were used to support biofloc development. Over a 157-day experimental period, shrimp reared in biofloc systems were compared with shrimp maintained under clear-water conditions. Shrimp growth performance was similar among all systems; however, biofloc treatments reduced water exchange by 81.6%. The type of carbon source influenced the structure of the microbial community, and molasses was associated with changes in the stress-related biomarker heat shock protein 70 (Hsp70), linked to physiological responses. These results indicate that biofloc technology can markedly reduce water use while maintaining biological performance, offering a practical and environmentally sustainable approach for the culture of an endemic freshwater shrimp and contributing to the conservation of Chile’s river ecosystems.

Biofloc technology (BFT) is based on the reutilization of nitrogenous waste generated by cultured organisms through the biotransformation of these compounds primarily into microbial biomass, allowing a reduction in water exchange. The aim of this study was to evaluate BFT as a water-saving culture strategy, using two carbon sources (chancaca and molasses), and to assess its effects on water-use efficiency, growth performance, digestive enzyme activity, and physiological responses in juvenile northern river shrimp (Cryphiops caementarius). The experiment was conducted in triplicate using 400 L fiberglass tanks, with an initial stocking density of 75 shrimp m−2 and an average individual weight of 0.85 ± 0.65 g, over a 157-day rearing period. Water quality parameters were maintained within suitable ranges throughout the study. Significant differences were observed in the composition of bacterial and plankton communities among the biofloc treatments, whereas no significant differences were detected in growth performance or digestive enzyme activities. Heat shock protein 70 (Hsp70), a stress-related biomarker indicative of physiological responses, exhibited higher levels in the biofloc treatment supplemented with molasses. Overall, BFT treatments reduced water exchange by 81.6% while maintaining comparable biological performance to the control, indicating that biofloc technology represents a water-efficient and environmentally sustainable culture approach for juvenile Cryphiops caementarius, an endemic freshwater shrimp species, particularly in water-limited regions of northern Chile.