Interspecific differences in larval production and dispersal in non-migratory galaxiids: implications for metapopulation structure

Abstract

Metapopulation structure can strongly influence how species respond to extinction threats. Isolated populations are highly vulnerable to extirpation, whereas interconnected populations are generally more resilient to pressures. In fish with sedentary adults, population connectivity can depend on the movements of early life stages. The present study examined how previously identified interspecific differences in life history affect larval production and dispersal in a species-complex of non-migratory galaxiid fish. Consistent with a priori predictions, ‘fast’ life-history species (high size-relative fecundity, early maturation, small egg size) showed high abundance of potential recruits, whereas the larvae of ‘slow’ life-history species (low size-relative fecundity, late maturation, large egg size) were, on average, between six and nine times less abundant. The species with intermediate traits showed moderate larval abundance compared with other species. The small, poorly swimming larvae of a ‘fast’ life-history species dispersed over large spatial scales (up to over 12km), whereas the larger, better-swimming larvae of a ‘slow’ life-history species showed minimal dispersal (<300m). These findings suggest that the ‘fast’ life-history species are likely to follow a classic source–sink metapopulation structure, whereas ‘slow’ life-history species are more likely to form isolated population structures. The implications for how these species respond to pressures from invasive salmonids, a principal cause of their decline, are discussed.