Abstract

Ambassis interrupta enters the lower Sepik River and is found in or near turbid river channels. The species is considered to be a predominantly marine and/or estuarine spawner. A. interrupta feeds mainly on small aquatic insect larvae but also on insects from terrestrial sources and on small crustaceans. Low variability in the data for condition, fat deposition, reproduction and feeding is interpreted by the species' lack of affinity for the floodplain and the presumed transient nature of the population. Fecundity (F) is expressed by the formula F= - 12.3 + I^5.3, where I is standard length (mm), and varied between 29 000 and 310 000 eggs per fish (70-105 mm standard length). Eggs are small (0.22 mm mean diameter) in comparison with known egg sizes for freshwater-spawning ambassids.