Evaluation of aqueous magnesium concentration on performance of Pacific white shrimp (Litopenaeus vannamei) cultured in low salinity water of west Alabama, USA

Authors: HERNANDEZ, DAVID - Auburn University; ABDELRAHMAN, HISHAM - Auburn University; GALKANDA-ARACHCHIGE, HARSHA - Wayamba University Of Sri Lanka; KELLY, ANITA - Auburn University; BUTTS, IAN - Auburn University; DAVIS, D. ALLEN - Auburn University; Beck, Benjamin; ROY, LUKE - Auburn University

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2022
Publication Date: 12/5/2022
Citation: Hernandez, D.P., Abdelrahman, H.A., Galkanda-Arachchige, H.S., Kelly, A.M., Butts, I.A., Davis, D., Beck, B.H., Roy, L.A. 2022. Evaluation of aqueous magnesium concentration on performance of Pacific white shrimp (Litopenaeus vannamei) cultured in low salinity water of west Alabama, USA. Aquaculture. 565. Article 739133. https://doi.org/10.1016/j.aquaculture.2022.739133.
DOI: https://doi.org/10.1016/j.aquaculture.2022.739133

Interpretive Summary: The ionic profile of inland low salinity sources can be dramatically different with variable concentrations of magnesium (Mg2+) in water. Inland shrimp farmers in Alabama supplement Mg2+ at the start of each production cycle to reach the level >20 mg/L. However, this level may not be high enough for larger shrimp in the later phase of the production cycle. Therefore, two field trials were conducted on a commercial shrimp farm in west Alabama to evaluate the effects of Mg2+ levels in low salinity water on growth, survival, and physiology of Pacific white shrimp. In the first study, additional Mg2+ was supplemented to four production ponds (28 mg/L Mg2+) and compared with control ponds (12.8 mg/L Mg2+). Shrimp were stocked and fed a commercial feed twice a day. After a 23-week pond trial, whole-body Mg2+ concentrations were higher in shrimp reared in Mg2+ treated ponds, while no significant differences in other study variables were observed between pond groups. However, after week 15 (shrimp weight> 22 g), weekly body weights of shrimp were significantly lower in the control group compared to the elevated Mg2+ treatment. This could perhaps be due to the size-dependent deficiency in the availability of adenosine triphosphate (ATP) and Mg2+ to support the growth of larger adult shrimp. The second experiment was conducted to evaluate the performances of larger shrimp (~13 g) reared in two on-levee flow-through tank systems. One tank system received water from a control pond with 12 mg/L Mg2+ while the second system was sourced with water from a production pond with a higher amount of Mg2+ (37 mg/L). In each system, twelve tanks were stocked with shrimp at three different densities (24, 29, and 35 shrimp/m2) to evaluate possible interactions between stocking density and Mg2+ level in water. Following an 8-week tank trial, no significant effects of tested Mg2+ levels, and/or tested stocking densities, or their interaction were observed on growth performance, survival, or physiology of shrimp. Overall, results from the current study confirm that even moderate elevations in the level of Mg2+ in low salinity water are advantageous to adult shrimp in later stages of the production cycle compared to the post-larvae, juveniles, or sub-adult shrimp.

Technical Abstract: The ionic profile of inland low salinity sources can be dramatically different with variable concentrations of magnesium (Mg2+) in water. Inland shrimp farmers in Alabama, USA supplement Mg2+ at the start of each production cycle to reach the level >20 mg/L at 1–15 g/L salinities. However, this level may not be high enough for larger shrimp in the later phase of the production cycle. Therefore, two field trials were conducted on a commercial shrimp farm in west Alabama to evaluate the effects of Mg2+ levels in low salinity water on growth, survival, and physiology of Pacific white shrimp, Litopenaeus vannamei. In the first study, additional Mg2+ was supplemented to four production ponds (28 mg/L Mg2+) and compared with control ponds (12.8 mg/L Mg2+; n=4). A stocking density of 27 postlarvae/m2 was used in ponds, and shrimp were offered a commercial feed twice a day. After a 23-week pond trial, whole-body Mg2+ concentrations were higher in shrimp reared in Mg2+ treated ponds, while no significant differences in other study variables were observed between pond groups. However, after week 15 (shrimp weight> 22 g), weekly body weights of shrimp were significantly lower in the control group compared to the elevated Mg2+ treatment. This could perhaps be due to the size-dependent deficiency in the availability of adenosine triphosphate (ATP) and Mg2+ to support the growth of larger adult shrimp. The second experiment was conducted to evaluate the performances of larger shrimp (~13 g) reared in two on-levee flow-through tank systems. One tank system received water from a control pond with 12 mg/L Mg2+ while the second system was sourced with water from a production pond with a higher amount of Mg2+ (37 mg/L). In each system, twelve 800-L tanks were stocked with shrimp at three different densities (24, 29, and 35 shrimp/m2) to evaluate possible interactions between stocking density and Mg2+ level in water. Following an 8-week tank trial, no significant effects of tested Mg2+ levels, and/or tested stocking densities, or their interaction were observed on growth performance, survival, or physiology of shrimp. Overall, results from the current study confirm that even moderate elevations in the level of Mg2+ in low salinity water are advantageous to adult shrimp (>22 g) in later stages of the production cycle compared to the post-larvae, juveniles, or sub-adult shrimp.