P. aztecus, like other penaeids, is an opportunistic omnivore that consumes some algal species (i.e., filamentous green algae, benthic diatoms, plant detritus, etc.) as well as small invertebrates such as copepods, mollusks, and annelids (Dall 1968; Odum and Heald 1972).Jones (1973), in a Louisiana study, found a dietary shift in P. aztecus as body size increased. Small shrimp measuring 22 - 44 mm in length were observed to feed nonselectively on top-layer sediments. Shrimp in a larger size class, from 45 - 64 mm in length, became selective in their feeding, preferring only organic materials from top-layer sediments. Larger shrimp, from 65 - 100 mm in length became predatory, feeding on annelid worms, amphipods, zooplankton larvae, and nematodes.Competitors: P. aztecus is likely to compete with other crustacean species, as well as with some fishes for access to invertebrate prey.Habitats: Brown shrimp are commonly found in estuaries and littoral zones along coasts. Primary habitats for these shrimp are muddy bottom areas from the intertidal zone to approximately 110 m. The greatest density of P. aztecus occurs at depths between 27 - 55 m. This species is rarely observed at depths exceeding 165 m (Williams 1984).In laboratory studies of substrate preference (Williams 1958), P. aztecus favored sandy mud and loose peat substrates over other offerings such as loose sand, and shell sand.Activity Time: P. aztecus is a burrowing shrimp that is considerably more active at night in open waters than it is during the daylight hours (Williams 1984).