Growing fish in the desert: a remarkably sustainable venture
By Mary M. Carroll
On a hot October day in the Arizona desert, Durkee McMaster scooped up a net of quarter-sized tilapia, a hearty freshwater fish native to Africa, from a round water nursery tank at Desert Springs Tilapia, an aquaculture farm. Tilapia farming has extensive roots in history, with a 4,000 year old Egyptian tomb containing a statue depicting tilapia held in ponds, and a biblical reference that leads some people to call tilapia “the Jesus fish” even to this day.
The practice of aquaculture has become popular in the United States over the past 40 years, due in part to the overexploitation of global fisheries. A 2010 U.N. Food and Agriculture Organization report stated: “Never has the need for sustainable global fisheries been more apparent and never have global fish stocks been more threatened. Overfishing and destructive fishing practices endanger not only the health of these stocks, but also the livelihoods of approximately 540 million people and the food security of some 3 billion people.”
Kevin Fitzsimmons, a professor in the Department of Soil, Water and Environmental Science at the University of Arizona, has been working in aquaculture for 25 years. He said it became popular in North American during the 1970s, as people recognized that global fisheries were declining because of unsustainable practices, such as trawling the ocean floor and overharvesting many species.
“Here in Arizona where we use a lot of water for irrigation,” Fitzsimmons said. “It just made sense that we grow fish or shrimp in that water before we use it to irrigate field crops – so that all of the waste from fish goes out as fertilizer for the crops.“
McMaster and Tark Rush, both former students of Fitzsimmons, co-manage and operate the Desert Springs Tilapia farm in Dateland, Arizona. McMaster holds a degree in fisheries management from the UA School of Natural Resources and the Environment, while Rush has a degree in microbiology.
“This is the only farm of its kind operating here in Arizona,” said McMaster.
Dealing with salty water
One unique feature of the farm is that they are using a water source that, due in part to damming, has proven inadequate for raising certain types of crops that were historically grown in the area.
“This farm was originally a cotton farm and as they pumped the groundwater table down, it became salty,” McMaster said. “The salinity actually crept into the groundwater and cotton can handle zero parts of salt, so the farm was no longer able to raise cotton as a crop.”
“I have lived here since 1973, when I was three years old,” Rush noted. “The Gila River, right here, used to always run. When the Gila River was running, we had good water, but it hasn’t been since about 1975, because they put all the dams up. The salt water we have here – the farms up above, their runoff is coming underground and as it leaches out, it is leaching salts out. So we are getting the tail end of this … and that is why our water is pretty salty.”
Tilapia can actually benefit from the salinity levels of 2 to 4 parts per thousand, McMaster explained, adding, “That’s enough to kill most crops – in particular, vegetable or table crops. Fish thrive on salt water as a general rule. Even freshwater fish, to a point, will do much better with salinity in the water.”
Tilapia, dubbed the “Jesus fish” because the Bible parable Mathew 17:27 states that a tilapia prophetically yielded a coin for paying taxes, is considered a good source of protein and vitamin B12. It is also low in saturated fat and sodium. It is considered a good choice for aquaculture as it is a fast-growing, short-lived, mainly herbivorous species.
The fish grown at the Arizona farm is packed fresh on ice and shipped, for human consumption, to restaurants and supermarkets in Phoenix, Las Vegas, and parts of southern California.
Another unique feature of this farm is that the aquifer supplying it generates geothermally heated water, which comes right out of the ground at a balmy 85 to 89 degrees. Tilapia thrive in water temperatures of 82 to 86 degrees Fahrenheit. This increases profitability by reducing costs for electricity. This supports year-round production, which is critical for profitability of agricultural ventures.
“If you are doing anything in ag, you prefer to have year-round in whatever that product happens to be when it goes to market,” McMaster said. “When we go to the grocery store today, we are accustomed to always seeing lettuce on the shelf. You can’t go to a grocery store and not find fresh lettuce – it just doesn’t exist anymore, and so all produce or meats have moved in that same direction.”
As Fitzsimmons indicated, “The purpose is to come up with more sustainable aquaculture and agriculture. And by sustainability, we mean both from an organic fertilizer type waste, and we mean that the farmer makes money. If you are an organic farmer and you don’t make any money, it is not sustainable. You have to be able to make money and you have to be able to protect the environment and make it a sustainable farm.”
The farm enhances its sustainability by utilizing a system of flowing well water and irrigation ditches to make a good second use of the water. Although cotton may not be able to tolerate saline water, other crops can.
“Most people consider water as their primary input product, but to us, it is a waste product,” McMaster explained. “You can either throw it out, which gives you absolutely no money – you make nothing on it, and probably have to pay somebody to get rid of it – or you figure out ways to then utilize that as a resource.”
Using these nutrient-rich waters for crop irrigation, they are able to successfully grow acres of wheat, sorghum, alfalfa, barley, a few other crops and some olive trees. The effluent produced by the tilapia contains nitrogen and phosphorus, key nutrients for plants.
When asked if having a fish farm in the desert might be considered bad for the environment, Fitzsimmons responded, “Not much, considering you are not putting chemicals on the ground, you are making better use of water resources, and you are putting fish on the market, which reduces the demand for wild fisheries that are overtaxed.”
In addition to the financial gains of growing additional crops, the plants also aid by filtering the water before it is reintroduced to the water table.
Desert Springs Tilapia has been operating as an aquaculture farm for approximately six years. In addition to raising tilapia and agricultural crops, McMaster and Rush also have recently added goats, which can feed on the crops grown there.
“We are about the only farm I know of that does a triple crop and we aren’t even done there,” Rush said. “We have 1,100 acres here and we can grow.”
They are making strides toward sustainability and innovation in a unique way in the Arizona desert. They use saline, geothermal water in the Gila River Valley to produce two – or even three, counting the goats – cash crops. Their efforts are helping to reduce pressure on global fisheries and provide a good source of protein to feed a growing population.
Perhaps these methods should be considered as a potentially profitable and sustainable way of farming for more farmers in the future, Fitzsimmons indicated.
“I would like to see all of agriculture in the world integrate with aquaculture and use the water twice,” he said. “Whether you are in Egypt or Pakistan or Mexico or southwestern Arizona, anybody who is pumping water to irrigate, you ought to grow fish in it. It doesn’t hurt anything, it just adds a lot of fertilizer value to the water, and the farmer gets another cash crop.”
Mary M. Carroll, a Pima Community College transfer student, is a junior at the University of Arizona majoring in the fisheries management option in the School of Natural Resources and the Environment. Since taking this class, Mary has discovered she is very interested in aquaculture. She hopes to further pursue more education in this field.
FAO. The State of World Fisheries and Aquaculture 2010. Rome, FAO. 2010. p.6.