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March 13, 2013

 

Mexico—A Solution to the Whitespot Problem?

 

 

At the recent World Aquaculture Society meeting in Nashville, Tennessee, USA, I chatted with Armando Leon, president and chief executive officer of Aonori Aquafarms, which farms brown shrimp (Penaeus californiensis, a cool water species) in ponds located along the Pacific Coast of Baja California, Mexico.  Its ponds are covered with a thick mat of macroalgae (Ulva clathrata).  The shrimp feed on the algae and the small organisms that live in it, and the algae recycle shrimp waste products and produce oxygen.  The algae are harvested as a high-value crop for animal feeds, seaweed snacks and condiments.  In our chat, Leon explained why his farm is far less likely to be hit by whitespot than the shrimp farms along the Sea of Cortez in the Mexican states of Sonora and Sinaloa.  Here are some excerpts from our chat.

 

Shrimp News: According to the State of Sonora Aquaculture Health Committee (COSAES), farmed shrimp production was 81,423 metric tons in 2009.  In 2010, the whitespot virus was detected in the coastal area around Hermosillo, an area on the Sea of Cortez with many large, semi-intensive farms, and by 2012, production decreased to 35,283 tons—a drop of 57%.  You’re planning to develop a big, new shrimp farm in Mexico based on a new technology.  What are you doing to protect your investment from whitespot?

 

Armando Leon: We are going to increase our production capabilities to meet the demand from our customers. To accomplish this, we are now seeking equity investments from investment funds and strategic investors who will what answers to the following two questions:

 

How do you deal with the diseases, particularly whitespot, that have hit other farms in northwest Mexico?

 

What makes your farm better able to deal with diseases than the traditional semi-intensive farms in northwest Mexico?

 

We will tell them that, there are several key differences between our system and the traditional system used by shrimp farmers along the Sea of Cortez

 

First, we are producing our own postlarvae from native brown shrimp broodstock obtained from the Pacific Ocean near our farm in San Quintin.  They have been tested for whitespot and other viruses by CIBNOR (Biological Research Center of the Northwest) in Hermosillo, Mexico, and found to be free of the five most common shrimp viruses, including whitespot.  Most of the farms on the Sea of Cortez purchase seedstock from biosecure hatcheries, some of which are located near farms that are know to have whitespot.

 

Whitespot has not been detected in any wild-caught crustaceans off the Pacific Coast of Baja California.  There are other shrimp farms on the Pacific side of the Baja Peninsula, but they are about a thousand miles south of us, and the currents flow north to south.  There are no farms north of us on the Pacific Ocean; therefore, the transmission of the whitespot virus to our farm via seawater is very highly unlikely. 

 

On the other hand, the whitespot virus has been detected in wild-caught crustaceans in different areas of the Sea of Cortez, where all farms have direct seawater intakes.  In contrast, by design, we have lower water flows than a conventional shrimp farm and our water intake is a beach well, not an open water channel.  As a result, the entry of organisms that might carry a disease is much less likely.

 

Nobody comes to our farm from other shrimp farms.  We have no vehicular deliveries from service providers that may have been at other farms.  There are no other shrimp farms around us; we are pretty much isolated.  That’s not the case for the farms along the Sea of Cortez where a large industry of hatcheries, farms, processing plants and service providers exists.

 

Our ambient temperatures also protect us from whitespot.  The whitespot virus only occurs in water temperatures between 24° and 30° centigrade.  The sea surface temperatures in the coastal area surrounding us don’t go above 22°C.  In the last three years, there have been no temperature readings above 22°C off our coast.  In the Sea of Cortez, they have temperature risks in the spring and the fall.  On our farm, we have only had temperatures above 24°C during the months of August and September, and then only for two days each month.  The temperature of the water in our ponds during 2012 was only above 24°C twice.  Other viruses may have different temperature ranges, but it’s the whitespot virus that everyone fears in Mexico, and it is the virus that crippled the shrimp farming industry along the Sea of Cortez in 2011 and 2012.

 

Low oxygen levels stress shrimp and make them more susceptible to disease.  The chances of our shrimp becoming stressed by low oxygen levels is much less than it is for the farms on the Sea of Cortez.  The algal mat on the surface of our ponds provides oxygen to the pond, and the liners on the bottom and sides of the ponds prevent soils from sucking oxygen out of the water column.  We also have an emergency aeration system to ensure that oxygen levels do not drop below three parts per million, and we have determined the best stocking density for preventing low oxygen conditions.  In the shrimp ponds along the Sea of Cortez, however, high temperatures lead to conditions of low oxygen when the stocking density exceeds the pond’s carrying capacity.  Those ponds also have soil bottoms that draw a lot of oxygen out of the water.

 

We usually have mild water temperatures because most of the surface of our ponds is covered with algae, which helps prevent dramatic swings in water temperature. We balance the biomass of shrimp with the biomass of algae so that we have don’t have to face oxygen depletion.

 

Along with supplemented feeds and probiotics, our shrimp eat the algae that floats on the surface of the ponds and the organisms, like and Artemia and copepods, that live in the algae.  The natural feeds stimulate more disease resistance, and there is research that shows that macroalgae provide a stimulus to the immune system in shrimp.  Our algae also has some antibacterial properties, so the Vibrios in our ponds are pretty much controlled by the macroalgae that floats on the surface.  Vibrios are much more common in the white shrimp farms along the Sea of Cortez.

 

In summary, our system and our location provide an environment that is less stressful to shrimp and make it far less likely that we will ever contract the whitespot virus.  Considering the damage that the whitespot virus has done to the shrimp farming industry in Mexico over the past two years, that is a critical point.  We feel we have something special for Mexico, a local species and an environment and system that should help prevent whitespot.

 

Information: Aonori Aquafarms, Inc., 8684 Avenida de la Fuente, Suite 11, San Diego, California 92154, USA (phone 1-619-785-3905, cell 1-408-439-4752, Skype: Armando A Leon, phone in Mexico 52-664-687-4656, email aonoriaquafarms@aol.com, webpage http://www.aonori-aquafarms.com/home).

 

Source: Armando Leon, interviewed by Bob Rosenberry, Shrimp News International.  World Aquaculture Society Meeting, Nashville, Tennessee, USA (February 21-25, 2013).  February 21, 2013.

 

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