Age composition, growth and reproductive biology of the salamanderfish Lepidogalaxias salamandroides: a re-examination

This study has determined the age and size compositions, growth rate and re productive biology of Lepidogalaxias salamandroides using data for fish of known sex and age and the monthly trends exhibited by various gonadal varia bles, including the sizes and stages of the oocytes. The results resolve co nflicting conclusions drawn by other workers concerning certain aspects of the biology of this freshwater species and expands our knowledge of this te leost. Our results are based on data derived from samples collected from sm all, ephemeral acidic pools in south-western Australia in 22 consecutive mo nths. Although ca. 78% of the fish caught belonged to the 0+ age class, sub stantial numbers of the 1+ and 2+ age classes and some 3+ and 4+ fish were caught. Spawning occurs between late May and late August, with peak activit y in late July and early August. During the first year of life, growth is i nitially rapid, but then ceases in the weeks immediately prior to and durin g the period when the habitat becomes dry and fish aestivate, before recomm encing in autumn as the pools again become filled with water. The growth co efficient (K) in the von Bertalanffy growth equation was lower for females (0.63) than males (1.28), reflecting the greater growth undergone by female s after the first year of life. Maturity was attained by ca. 28% of the fem ales and ca. 26% of the males that reached the end of their first year of l ife and by all fish that reached the end of subsequent years of life. The L (50)s for females and males at first maturity were 43.2 and 38.6 mm TL, res pectively. The mean fecundity was only 82.4, reflecting a combination of a small body size and a relatively large egg (diameter=1.8 mm). Lepidogalaxia s salamandroides is a multiple spawner, which increases the chances of some eggs and newly-hatched embryos encountering a period of favourable environ mental conditions during the spawning period, which is characterised by bou ts of heavy rainfall. The ratio of females to males was essentially parity in the 0+ and 1+ age classes and in all age classes collectively. When test es commence maturing for the first time, the anal fin of males starts to be come modified to form a structure that facilitates the transfer of sperm to the female, and it remains modified throughout the rest of life.