Another concern related to shrimp aquaculture and fisheries has appeared; fishermen claim that pumping water transfers postlarvae to shrimp ponds causing an additional impact on wild shrimp populations and consequently on shrimp landings. Considering the number of farms and the amount of water pumped, it is obvious that some postlarvae could be carried into the ponds; however, there is no scientific evidence that this activity is affecting shrimp fisheries. First, this extraction would take place at postlarvae age where the impact on the fishery is minimal. Moreover, postlarvae distribution patterns offshore, and nursery ground immigration behavior, make it unlikely. Postlarvae distribution is not homogenous in time and space and it is known that they concentrate near lagoon and estuary inlets. Also, immigration mechanisms are based on tidal movements combined with postlarvae vertical migration. Postlarvae can remain near the bottom to avoid being carried offshore when the tidal current is offshore and move higher in the water column during the opposite direction to enter estuaries and coastal lagoons ( Macias-Regalado, 2001). However, as in the above case, further observations are needed to give a sound opinion about a possible effect derived from pumping water on the fisheries production.