Postlarvae and juveniles of Farfantepenaeus spp. and Xiphopenaeus kroyeri were collected at Boca de la Barra (Cienaga Grande de Santa Marta) by means of a channel net that orientates with the tide. Sampling was carried out every two weeks for a year (February 1998-February 1999) so that each sampling date corresponded to full and new moon alternatively. Farfantepenaeus spp. postlarvae tended to appear in the dry season and with significantly greater abundance during full moon (Mann-Whitney test, P 0.05). In the case of X. kroyeri in no instance significant were differences found between seasons or moon phases (Mann-Whitney test, P>0.05). However, some tendencies can be pointed out: postlarvae appeared in higher proportions during the new moon but no major difference was recorded between seasons whereas juveniles appeared in greater concentracions in the rainy season with almost no difference between moon phases. These results are disscused in terms of the scanty historical previous work. The relations TL-CL and CL-Weight and some morphometric and meristic features are reported.