Spatial and temporal patterns of habitat use by three estuarine species of mysid shrimp

Abstract

The mysids Rhopalopthalmus egregius, Haplostylus dakini and Doxomysis australiensis are abundant yet unstudied omnivorous crustaceans in Australian estuaries. Habitat use and population dynamics were investigated for these species over spring and summer in the Tweed River, Australia, to explore their ecological role in estuarine ecosystems. Overall, mysids were concentrated in shallow unvegetated and deep unvegetated estuarine habitats. H. dakini were most abundant in shallow and deep bare habitats at night, whereas R. egregius were most abundant in deep bare habitats during the night. D. australiensis were present across all habitats in the night, but negligible numbers were present during the day. Significantly greater numbers of R. egregius and D. australiensis were sampled during the new moon, compared with the full moon. Significantly larger R. egregius and D. australiensis individuals were present in benthic habitats at night, indicating possible partitioning of habitat for juvenile and adult subpopulations. Adaptive foraging strategies and habitat use facilitates the coexistence of sympatric mysid species, H. dakini and R. egregius, and within-species habitat partitioning allowed juvenile R. egregius to avoid interaction with adult R. egregius. The observed dynamics minimize inter- and intra-specific predation between mysids, and by other predators, while optimizing access to key trophic resources.