Vertical Distribution of Shrimp Larvae of the Superfamily Penaeoidea During a Diurnal Cycle in the Southern Gulf of Mexico.

The vertical distribution of penaeoid shrimp larvae along a 24 hr cycle was analysed from two samplings carried out in distinct periods, i.e., summer and autumn 1993 in the southern Gulf of Mexico. A total of 7238 larvae belonging to the genera Solenocera and Sicyonia, and to the family Penaeidae was collected. In summer, the abundance of shrimp larvae was comparatively lower, with a total of 1062 individuals. The very low number (33 individuals) of Sicyonia larvae collected during this period did not allow detecting a clear vertical migration pattern. In the larvae of the genus Solenocera (837 specimens) and of the family Penaeidae (192 specimens), a typical vertical migration pattern was observed, in which larvae concentrated in shallow strata at dusk, while at dawn they moved toward deeper areas. During autumn, the highest abundance of larvae was obtained, with 6176 individuals captured. Larvae of the family Penaeidae adjusted to the typical vertical distribution pattern of meroplanktonic larvae, with a higher abundance near the surface during the day, and toward deeper strata at night. The Solenocera mysis (1685 individuals) showed a reverse behaviour, with high concentrations between 10 and 45 m depth. The Sicyonia mysis larvae (2465 specimens) increased their dispersion pattern along the water column at night. The distribution of the various penaeid larvae suggests a different vertical distribution behaviour for each group, with some overlap. The Solenocera's tend to remain mainly in the middle of the water column sampled, while Sicyonia larvae show a larger dispersion in that column, and the Penaeidae tend to concentrate near to the surface between 0 and 10 m depth. [ABSTRACT FROM AUTHOR]