Impact of Shrimp Farming on Mangrove Forest and Other Coastal Wetlands: The Case of Mexico - Aquaculture and the Environment: A Shared Destiny - page 19

per kg, with feed and seed prices as the major constraints for investors (Ponce-Palafox et al.,
2011). However, farmed shrimp production has grown from 0.05% to 40% of the total
national production for this crustacean (FAO, 2011), and Mexico is currently positioned
among the ten largest producers of farmed shrimp in the world (Fig. 1) (Conapesca, 2009;
2010).
At the country level, shrimp aquaculture is practiced in almost all 17 coastal states. Even in
inland locations, there are some initiatives to cultivate the same species used in marine
aquaculture but adapted to freshwater environments. Although shrimp aquaculture is
widespread nationally, the Gulf of California region is the most highly concentrated region
of activity, with the states of Sonora, Sinaloa and Nayarit representing more than 95% of the
total shrimp pond extent and production in Mexico. By contrast, Jalisco, Michoacán, Oaxaca,
Chiapas and Tabasco together amount to less than 1% (Fig. 2) because physiographic or
economic factors have inhibited the development of this activity.
Some species of the genera Litopenaeus and Farfantepenaeus have been used for commercial
purposes, but the white shrimp L. vannamei is currently the most common species in culture.
This species is grown in one (8-9 months) or two cycles (3-4 months each) a year, obtaining a
final weight between 10 to 25 g in the first case and 7 to 11 g in the second. Even when the
use of wild postlarvae (PL) is allowed in Mexico, with permission granted for extraction,
this activity is sustained by PL production controlled in 33 laboratories that produce in
average of approximately 76 million PL per year. The last reliable record of aquaculture in
Mexico (CONAPESCA, 2010) states a total output of approximately 72 900 ha as of 2008
(Figure 1). In almost all cases, the shrimp farms use semi-intensive production systems,
which, aside from the certified larvae, require substantial amounts of fertilizers to increase
natural productivity and complementary feed to maintain stocking densities from 6 to 30
postlarvae per area (PL/m 2 ).
With this system, and considering the figures on total shrimp pond area and production, the
average yield from 2000 to 2008 was 1260 kg ha -1 (Fig. 1), although it was lower from 2000 to
2003, when sanitary problems associated with viral diseases occurred, increasing later to
approximately 1750 kg ha -1 , a level that has been maintained since 2006 (CONAPESCA, 2009;
2010). In agreement with Ponce-Palafox et al. (2011), the top three producer states in Mexico
obtained average yields of 800 (Nayarit), 900 (Sinaloa) and 3200 (Sonora) kg ha -1 per crop.
2. Methods: Land use changes associated with shrimp farming in Mexico
To analyze the land use changes caused by shrimp farming in Mexico and to estimate rates of
coastal wetland loss induced by this activity, we performed a change detection analysis in
three steps following a procedure similar to that proposed by Berlanga-Robles et al. (2011).
Because shrimp farming in Mexico is concentrated around the northern states, particularly the
east coast of the Gulf of California, to make this study representative, four states that account
for 97% of this activity in extent and production were chosen for the analysis: Nayarit, Sinaloa
and Sonora in the Gulf of California and Tamaulipas in the Gulf of Mexico (Figure 2).
2.1 Shrimp farm location and inventory
First, the shrimp farms of the four states selected were geographically located with a database
provided by the National Commission for Fisheries and Aquaculture (CONAPESCA).