Postlarvae recruitment of blue shrimo Litopenaeus stylostris (Stimpson, 1871) in antiestuarin conditions due to anthropogenic activities

Abstract

The objective of this survey was to determine a statistic relation between freshwater discharge of th eColorado River, relative abundance of blue shrimp (L. stylirostris) postlarvae and commercial shrim catch in the Upper Gulf of California (UGC). In order to get the objective we get records of the Colorado River flow from 1904 to 1998, we collected blue shrimp postlarvae (PL) in San Felipe, B. C. every fourteen days from April to November of 1993, 1994 and 1997; 12-27 of July of 1995 and from 29 of june to 16 July of 1996. We also get daily record per boat of the commercial shrimp catch in the UGC from September to December from 1995 to 1998 to determine the CPUE in kg/trip. The analysis were made using LSD test with a 0.05. We found two groups of postlarvae abundance with significant difference (>43 PLm^-3 and <16 PLm^-3 ). The CPUE also showed two significant groups one of 21.5 kg/trip and other <18.2 kg/trip. The hogher values groups in CPUE and postlarvae abundance were on those years when river flow was larger than 100 m³ s^-1 in 1993, 1997 and 1998. And the lower values groups were found when river flow was less than 80 m³ s^-1 in 1994, 1995 and 1996. The increase in postlarvae abundance and commercial shrimp catch on those years when freshwater discharge were larger was likely because to positives effects on the habitat: 1) the increase of carrying capacity by nutrient addition and 2) the increase of the habitat volume. We conclude that blue shrimp L. stylirostris can use the high salinity areas like UGC as abundance and commercial catch of blue shrimp.