Variation in Life History of Land-Locked Lacustrine and Riverine Populations of Galaxias maculatus (Jenyns 1842) in Western Australia

Abstract

Galaxias maculatus is one of the most naturally widely distributed species in the world yet there is no published literature on the biology of Western Australian populations. Galaxias maculatus in the rivers of the south coast of Western Australia inhabit an environment that is variable and at times unpredictable. By examining trends in gonadal development, lengths at first maturity, growth and appearance and persistence of larvae of G. maculatus in two saline rivers (Jerdacuttup River and Oldfield River) and one freshwater lake (Moates Lake), the life histories of populations in contrasting environments were determined. The stable conditions that prevail in the low salinity, cool waters of Moates Lake have fostered an extremely protracted breeding and larval recruitment period (year round) in comparison to limited recruitment in the riverine environments which experience less predictable flow events and water quality (salinity). An upstream migration for breeding in the Jerdacuttup and Oldfield rivers is similar to land-locked G. maculatus in south-eastern Australia and is a reversal of the downstream migration in Moates Lake or populations with marine larval dispersal, i.e. diadromous populations. Differences in population demographics existed between these habitats, with smaller maximum sizes and significantly smaller sizes at maturation occurring in the rivers compared to the lake. In Moates Lake approximately 93, 6 and 1% were 0+, 1+ and 2+, respectively; while cohort progression in the rivers suggests that most fish do not live beyond their first year. As an adaptable opportunist, G. maculatus can modify its life history strategy at a local level to persist in varied and sometimes unpredictable environments.