Spawning strategies ofGalaxias gollumoidesMcDowall and Chadderton (Gollum galaxias) from wetland and stream habitats

Abstract

AbstractGalaxias gollumoidesMcDowall and Chadderton occurs in contrasting hydrological environments across Southland and Stewart Island, New Zealand. Our study experimentally investigated intraspecific variation inG. gollumoidesfrom wetland and stream habitats, testing for phenotypic divergence in spawning substrate choice, and that spawning timing is influenced by the proximate hydrological and meteorological environments. Wetland and streamG. gollumoidesdisplayed intraspecific behavioural divergence, utilising contrasting spawning substrates across multiple tanks, even when held in common experimental conditions.Galaxias gollumoidesdisplayed intraspecific spawning timing differences with wetland‐sourcedG. gollumoidesspawning earlier than stream‐sourcedG. gollumoides. Spawning also occurred significantly more often during peaks of warmer mean daily water temperature and barometric pressure, than during colder temperature, low‐pressure periods. Interannual variation in initial spawning timing was also attributed to differences in water temperature. In combination, experimental evidence‐ and field‐based observations support our hypothesis thatG. gollumoidescan utilise available substrates in habitats of contrasting hydrology and structure, while spawning timing is controlled by changes in proximate environmental conditions. These characteristics may enhance a population's recruitment success and the species persistence in the fluctuating hydrological environments of ephemeral wetlands and tributary streams that were once likely widespread in Southland.