Aquaculture of Marine Fish in Inland Low Salinity Well Water: Potassium Is Not the Only Limiting Element

N Mourad S Kreydiyyeh,J Ghanawi Ip Saoud

doi:10.4172/2150-3508.1000042

Abstract

Inland saline groundwater is abundant in various areas of the world but is not suitable for traditional agriculture irrigation and is also not suitable for marine aquaculture mainly because of potassium deficiencies. In the present work, we used marbled spinefoot rabbitfish Siganus rivulatus, as a model organism to investigate whether varying levels of aqueous K+ affect survival and growth, and whether ambient K+ has an effect on fish osmoregulation and haemolymph osmolality. A ten-week growth experiment was conducted where fish were reared in reconstituted inland saline water containing K+ concentrations equivalent to 15%, 40% and 100% (denoted as: Trt15, Trt40, and Trt100, respectively) of potassium in 15 ppt seawater. A 15 ppt seawater treatment (CSW) was used as a control. Fish weight, length, survival, Fulton-type condition index, blood and water osmolality, and serum Na+ and K+ concentrations were evaluated. Gill NKA activity was also estimated. Fish reared in Trt15 died during week 8. At the end of the experiment (week 10), no differences were observed in fish survival and total length among treatments Trt40 and Trt100 and control (P>0.05). Final weight was less in Trt40 and Trt100 than in CSW. Fulton-type condition index results showed that Trt100 was more suitable for fish than Trt40, but still not as suitable as 15 ppt sea water. Sodium (Na+) in serum was not affected by aqueous K+ levels, whereas serum K+ varied congruently with aqueous K+. Rabbitfish reared in Trt40 and Trt100 had greater blood osmolality than those reared in control seawater. Gill NKA activity also increased by 50% in Trt40 and Trt100 as compared to control. The present study shows that potassium-deficient 15 ppt inland well water is not suitable for long-term culture of Siganus rivulatus. Results suggest that inland saline well waters greatly increase activity of NKA and consequently energy expenditure. Furthermore, K+ does not appear to be the only limiting mineral in inland low salinity groundwater that affects fish osmoregulation.

Highlights

Increasing demand for aquatic food products combined with limited production from capture fisheries is responsible for rapid coastal and inland aquaculture development
Results of the present study suggest that potassium-deficient 15 ppt low salinity well water is not suitable for longterm culture of Siganus rivulatus
When potassium is supplemented to Inland saline well waters (ISWW), survival and growth of S. rivulatus improves

Summary

Introduction

Increasing demand for aquatic food products combined with limited production from capture fisheries is responsible for rapid coastal and inland aquaculture development. High cost of coastal land, strict regulations, and environmental concerns, have led aqua farmers to favor inland aquaculture. The fact that various areas of the world (e.g. Australia, USA, China, India, Thailand, Brazil, Ecuador) are underlain by saline ground waters not suitable for traditional agriculture [1,2,3] has greatly increased interest in inland aquaculture of saltwater species. Saline ground waters are generally deficient in the key ion potassium (K+) [5, 6]. Adding a potassium source such as muriate of potash (KCl) and K-Mag to pond waters in order to increase aqueous K+ concentrations generally improves performance/production of marine species [7,8,9]

Methods

Results

Conclusion