Biology of the black-stripe minnow Galaxiella nigrostriata, including comparisons with the other two Galaxiella species

The growth, age composition, reproductive biology and diet of Galaxiella nigrostriata in seasonal water bodies in south-western Australia are described and compared with G. munda and G. pusilla. Like the other two Galaxiella species, G. nigrostriata has a 1 year life cycle. The mean length attained by female G. nigrostriata at sexual maturity is approximately 37 mm, compared with about 47 and 28 mm for G. munda and G. pusilla, respectively. Like G. munda, G. nigrostriata is a multiple spawner. Although all three Galaxiella species breed mainly in winter and early spring, spawning occurs earlier in G. nigrostriata than in the other two species. An early production of offspring enables the young females and males of this species to reach approximately 78 and 88%, respectively, of their ultimate body length by early summer. Such a prolonged period of early and relatively rapid growth is advantageous to G. nigrostriata, since this species lives in water bodies that often dry up during the summer and early autumn and thus cannot grow during this period. The gonads start to undergo rapid development in autumn, when the pools begin to fill with water following the onset of the seasonal rains. All three Galaxielta species are carnivores. Galaxiella nigrostriata mainly takes prey from the water column and the water surface, G. pusilla focuses on prey in the water column and benthos, and G. munda feeds widely on prey on the water surface, throughout the water column and from the benthos. The prevalence of small prey, such as cladocera and calanoid copepods, is greater in the diets of G. nigrostriata and G. pusilla than in that of G. munda.