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Guide to New Zealand's freshwater invertebrates
Phreatogammarus is one of several amphipod genera with species usually found in or near stream and river estuaries. The species pictured (possibly P. helmsii), is a coastal stream species that is typically pale, sometimes with grey-brown mottling, and has a bean-shaped eye. The 1st (upper) antennae are slightly longer than the 2nd antennae.
Most of our records of Phreatogammarus are from the slow-flowing, lower reaches of streams in or near the estuarine zone.
They are likely to be collector-gatherers, feeding on deposited organic matter and biofilms.
The Phreatogammarus species pictured may provide an indication of estuarine influence, but little indication about water quality. Phreatogammarus has not been assigned tolerance values, but the general amphipod values are 5 (hard bottom sites) and 5.5 (soft bottom sites).