Increased production of inland shrimp farms

Increased production of inland shrimp farms

Summary

Inland shrimp farming uses groundwater that, relative to seawater, is deficient in potassium (K) and magnesium (Mg. This causes an ionic imbalance in the shrimp resulting in significant stress and major mortalities during the summer. Farmers must often harvest ponds before the shrimp have reached optimal size, resulting in economic loss. Two strategies for alleviating the low-K, Mg problem will be developed and tested in replicated trials: addition of K and Mg to the pond water and to the feed. We have completed controlled experiments to examine the effects of K and Mg on shrimp growth with supplementing either Mg or K to the commercial diets. However, we found no significant increases in shrimp growth.

Objectives/Performance Targets

Objectives
The overall goal of the project is to increase the viability of inland shrimp farms in the WSARE region by improving farm productivity. The project objectives are: 1) to determine the concentrations of potassium, both in the pond water and feed, needed to reduce osmoregulation stress, and related mortalities, to shrimp in low-salinity ponds; and 2) to develop pond management strategies based on these results.

Results and Discussion
At the end of the previous year, two farms quit producing shrimp and switched to raising fish. The remaining farm is not conducive to conducting pond trials, because it has few employees and the farm manager is concerned about possible contamination. Therefore, our emphasis to date has focused on greenhouse and laboratory trials. We set up two recirculating systems in an environmentally controlled greenhouse at the Enivronmental Research Laboratory to use in diet studies. We also set up a wet lab with controlled aquaria for replicated growth and physiology trials. We have established a post-larval, greenhouse, system for rearing post-larvae, which we obtain from commercial hatcheries. Water for the growth and physiology trial is hauled in large tanks from the pond sites to the university.
We focused our initial efforts on evaluating the effects of supplementing commercial shrimp feed with potassium and magnesium of the growth and osmoregulation of shrimp reared in low-salinity water. We refurbished a pellet mill and feed laboratory at University of Arizona, allowing us to produce small lots of pelletized shrimp feeds with added K and Mg. This eliminated the need for obtaining large quantities of shrimp feeds from the major manufacturers and allowed us to run a series of feeding trials.
We completed two independent greenhouse trials in low-salinity, recirculating raceways to look for effects of added magnesium in the diet on shrimp growth. We also completed independent tests in raceways and tanks to look at the effect of increased dietary potassium on shrimp growth. We found no significant increases in growth from adding either Mg or K to the commercial diets. Also, there were no significant effects of diet on either the osmolality of the shrimp haemolymph or the ion concentrations in the shrimp tissues.
One caveat is that the K ions added to the diet were added as KCl, which is water soluble. We examined the leaching of K from the the diets under our experimental conditions. We found that at the end of a two-hour feeding period all of the diets had the same K concentrations. Therefore, the shrimp may not have received any actual nutritional advantage from the supplemented diets.
We have completed one controlled experiment to examine the effects on shrimp growth and osmoregulation of supplementing pond water with K. In this trial shrimp were individually marked, so that effects of initial weight could be taken into account in the analysis. We found no significant effect of increasing the K concentrations on either the specific growth rate of the shrimp or on the blood osmolality.

Accomplishments/Milestones

Accomplishments to date:
1) We have conducted several successful, carefully replicated, growth trials with commercial feeds supplemented with K and Mg.
2) We have successfully completed a growth trial testing the effect of adding KCl to pond water on shrimp growth.
3) We have set up controlled recirculating systems for conducting diet studies with marine shrimp.
4) We have set up aquaculture facilities in greenhouses and in a restricted laboratory at the University of Arizona for rearing post-larval shrimp and for conducting replicated growth and physiology trials.
5) One graduate student and two undergraduate students have received training by participating in this project.
Remaining tasks
1) We will conduct additional trials to confirm our results regarding supplementing pond water with potassium
2) We will run additional trials to examine the effect of temperature on the osmoregulation of shrimp in saline groundwater.

Impacts and Contributions/Outcomes

From the dissemination of these results, development of additional inland aquaculture farms may be encouraged. As this project addresses a major issue for inland shrimp farms in the US and elsewhere, the potential economic impact is significant. In addition, the results will allow wider development of a largely unused resource of saline groundwater, allowing agriculture development on land where it was previously not feasible. It will also allow the expansion of inland aquaculture in the arid West and provide a means of economic development in isolated rural communities in this region.

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