Life-cycle duration, growth and spawning times of five species of atherinidae (Teleostei) found in a Western Australian estuary

Abstract

Five species of atherinid were collected monthly from the estuary of the Swan-Avon river system. Length-frequency data and gonadosomic indices showed that Atherinosoma presbyteroides, A. elongata, A. wallacei and Allanetta mugiloides typically have a 1-year life cycle and generally reach maturity at total lengths of 40-85 mm. The mean length of the mature females was significantly greater than that of the mature males in each Atherinosoma species, but not in Allanetta mugiloides. The fifth species, Pranesus ogilbyi, was often represented by many individuals with far greater total lengths (100-150 mm) than were found in the other four species, a feature that reflected the presence of two year classes. Length-frequency and gonadosomic data indicated that all five atherinid species breed over protracted periods during spring and summer. Values for the gonadosomic index and the absence of local marine populations of Atherinosoma elongata, Allanetta mugiloides and Atherinosoma wallacei confirmed that the populations of these species in the Swan-Avon are estuarine or estuarine-inland water sensu stricto. Gonadosomic values for the marine species A. presbyteroides and P. ogilbyi, allied with the times of disappearance of larger individuals from the estuary, suggested that only the former of these two species may breed to any extent in the estuary. Length-frequency histograms showed that the populations of A. presbyteroides and P. ogilbyi in the Swan-Avon are more heterogeneous than those of the same species in a nearby marine embayment.