Does the relative value of submerged aquatic vegetation for penaeid shrimp vary with proximity to a tidal inlet? Preliminary evidence from a subtropical coastal lagoon

The value of submerged aquatic vegetation (SAV) as a nursery habitat for penaeid shrimp has been recognised previously; however, the importance of SAV in terms of its distance from a tidal inlet (a site through which shrimp postlarvae migrate into coastal lagoons) has not been evaluated. In the present study, the effect of proximity to a tidal inlet on the relative importance of SAV beds for Farfantepenaeus shrimp was evaluated in the Laguna Madre of Tamaulipas (Mexico). Sampling was performed monthly from February to December 2005, diurnally and nocturnally, in two SAV bed areas, one 25 km (distant) and the other 1 km (nearby) from the inlet. Densities of shrimp (F. aztecus, F. duorarum and F. brasiliensis) were consistently higher in the nearby SAV bed during both the day and night. Water temperature was the most important explanatory variable of shrimp abundance in both SAV beds. The temperature-abundance relationship was negative in all cases, except in the distant SAV bed at night, when shrimp abundance was positively related to dissolved oxygen and salinity. The nearby SAV bed had higher recruit abundance and supported a greater numbers of juveniles and subadults. In contrast, shrimp abundance in the distant SAV bed was apparently limited by recruitment.