Increased production of inland shrimp farms
A developing industry in the WSARE region and elsewhere in the United States is the farming of marine shrimp in inland areas where saline groundwater is available. There are numerous advantages of inland shrimp aquaculture, and these are well known. Chief among these is that the farms are located far from coastal areas. Inland farms can be developed in areas where land costs are much lower and where the risk of transferring diseases between farmed and wild stocks is virtually eliminated. The saline groundwater used for shrimp culture is abundant in the arid west and previously has not been considered a resource, because it is generally not suitable for agriculture. However, the marine shrimp currently being farmed can grow at the salinities characteristics of these groundwater sources. This is possible since the shrimp can regulate the hamolymph ionic concentrations, and can be acclimated to low salinities.
Osmoregulation by penaeid shrimp is influenced by several factors including size, temperature, and condition. Osmoregulatory capacity has been suggested for use as means of monitoring stress in farmed shrimp populations. Conditions adverse to the ability of the shrimp to osmoregulate can result in reduced growth and increased mortality.
Although these marine shrimp can be grown in low salinities, the current farms in Arizona have had problems with mortalities, especially at times of added stress, such as during molting, and at higher temperatures. These problems occur even at salinities the shrimp are known to tolerate. Similar problems are known from inland shrimp farms in other parts of the US. The problems have been attributed to the ionic composition of the groundwaters differing considerably from that of dilute (low salinity) seawater.
Analyses of the ionic composition of saline groundwaters have shown the relative concentrations of individual cations vary considerably among farms and are quite different from those in seawater. Of particular concern is potassium (K+), which is known to be important in shrimp osmoregulation and which is proportionately very low in saline groundwater in comparison to seawater. Mangesium is also of interest. However, from previous research, potassium levels have been shown to be critical to shrimp survival in low-salinity groundwaters. In some cases it may be the ratio of potassium to other cations in the water that is of importance, rather than simply the potassium concentrations. In particular the ratio of potassium to sodium (Na+) may be important because these are exchanged between the shrimp, via the gills, and the environment in order to balance critical levels in the shrimp hemolymph. These exchanges of these ions at specialized sites in the gills are made physiological pumps that require metabolic energy expenditure, so shrimp must have adequate caloric intake to meet these needs. Two general approaches have been taken to increase the availability of potassium to shrimp grown in inland farms.
One approach is to add additional potassium to the pond water. However, adding sea salt to inland pond water to achieve an ionic balance is expensive and, therefore, not practical for commercial farms. Although some producers have had success with adding potassium, in the form of potash, to the pond water, critical levels have not been established. Also, because many variables involved in shrimp farming can affect production and mortality, it is difficult to draw meaningful conclusions based on short-term experiences of various farms. In addition, solutions derived through trial and error on one farm may not work on other farms. We propose to address this issue through carefully designed replicated experiments at two commercial farms.
Another approach is to provide critical minerals in the diet. There has been some work in this area, but the results in practical application have been inconclusive. We are using rigorous statistical designs in experimental trials to determine if increased magnesium and potassium in the shrimp feed will improve growth and survival at commercial farms in Arizona. This entails a series of replicated experiments both at farm locations and in carefully controlled laboratory/greenhouse experiments.
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 osmoregulatory stress, and related mortalities, to shrimp in low-salinity ponds; and 2) to develop pond management strategies based on these results.
We have expanded the project to include an additional producer and to examine the effects of magnesium in the diet. Also, we have developed the capability of manufacturing small lots of pellitized shrimp feed, so we can readily make the diets to our specificiations. This eliminates the need for obtaining large quanties of shrimp feeds from the major manufacturers and allows us to run more feeding trials.
The grant funds were only available just prior to the 2006 growing season. This resulted in problems obtaining needed equipment for monitoring and maintaining water quality. We conducted two growth trials at one shrimp farm; but because of water quality issues, the results the trials were aborted. However, the cages are in place and materials available to re-run the trials during the next growing season. Emphasis to date has focused on greenhouse trials.
During the down time for the farms, we set up two recirculating systems in an environmentally controlled greenhouse at the Enivronmental Research Laboratory to use in diet studies with marine shrimp. We obtained post-larval shrimp from a commercial hatchery. These post-larvae were reared in temperature-contolled, aerated tanks supplied with biological filteration until the shrimp were large enough to use in the diet trials. Our initial experiments have focused on the effects of magnesium added to the diet. We found an increased growth with diets containing 2 g/kg of Mg compared to a control diet without added Mg and to a diet containg a higher (3g/kg) concentrations of Mg. In the first trial we used shrimp that were from 2-8 grams initial weight. We then determined the relation between specific growth rate of the shirmp and intial weight, so we could use initial weight as a covariate in the statistical analysis of the feeding trials. Trials are being run in dilute seawater and in saline water from the farm sites.
Accomplishments to date:
1) We have manufactured cages for use in diet trials at the farm sites.
2) We have refurbished the feed manufacturing facilities at the Environmental Research Laboratory and have manufactured some of the experimental diets.
3) We have set up environmentally controlled recirculating systems for conducting diet studies with marine shrimp
4) We have set up rearing tanks for growing post-larval shrimp to sizes that can be used in the growth trials.
5) We have run preliminary growth trials at the farm site and have successfully run growth trials in recuirculating tanks in the laboratory.
1) We will test additional diets in laboratory growth trials. Each test lasts approximately 1 month.
2) We will run diet tests at the farm sites when the next production cycle begins.
Impacts and Contributions/Outcomes
We expect that the results of this project will allow an increase in annual production for existing farms and an increase in farm gate value. Also, from the dissemination of these results, development of additional inland aquaculture farms will be encouraged. As this project addresses a major issue for inland shrimp farms in the United States 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.
Senior Research Scientist
University of Arizona
Environmental Research Lab
Tucson, AZ 85706
Office Phone: 5206263318
Arizona Shrimp Company
Dateland, AZ 85333
Office Phone: 9282461877
Arizona Maroculture Associates
Dateland, AZ 85333
Office Phone: 9284542360
University of Arizona
1117, E. Lowell
Department of Veterinary Science/Microbiology
Tucson, AZ 85721
Office Phone: 5206214438