Spring and summer macroinvertebrate drift in the lower Mississippi River, Louisiana

Macroinvertebrate drift was sampled dielly each month at 3 stations across the lower Mississippi River, Louisiana. At least 134 taxa were identified from seven phyla. Total drift catches varied with respect to month, time of day, and station. Relative abundance was greatest in June and August, moderate in July, and lowest in April and May. Dipterans, ephemeropterans and trichopterans numerically dominated the catches and each tended to have its zenith in July, August and June respectively. Important non-insect groups were hydroids, oligochaetes, pelecypods and amphipods and with the exception of pelecypods, were most abundant in April. The presence of certain apparent "exotic" oligochaetes suggested that at least some elements of the drift may be derived from rather remote areas - perhaps even the drainage headwaters.