, Volume 211, Issue 2, pp 77-88

Biology of the western minnow, Galaxias occidentalis Ogilby (Teleostei : Galaxiidae), in a south-western Australian river

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Abstract

Larval, juvenile and adult Galaxias occidentalis were collected with a plankton net and a fine-meshed beach seine from the southern branch of the Collie River in south-western Australia at approximately monthly intervals between January 1984 and December 1986. Seasonal changes in the density of G. occidentalis in the main river and its tributary creeks, and concomitant changes in gonadosomatic index and ovarian morphology, were used to elucidate the reproductive biology of this species. Sexual maturation commenced in autumn and fish moved into small tributaries soon after these creeks had begun to flow in early winter. While spawning commenced as early as June, it peaked in August, when water temperatures started to rise, and was essentially completed by the end of September. Galaxias occidentalis reached maturity at the end of its first year of life. Some fish survived to spawn in the following year and a very limited number into a third, fourth and even a fifth year. Mean fecundity ± 95% confidence limits increased from 725 ± 69 in 0 + females (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbnL2yY9% 2CVzgDGmvyUnhitvMCPzgarmqr1ngBPrgitLxBI9gBaerbd9wDYLwz% YbItLDharuavP1wzZbItLDhis9wBH5garqqr1ngBPrgifHhDYfgasa% acOqpw0le9v8qqaqFD0xXdHaVhbbf9v8qqaqFr0xc9pk0xbba9q8Wq% Ffea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dme% aabaqaciGacaGaaeqabaWaaqaafaaakeaadaqdaaqaaiaabEhacaqG% 0baaaaaa!45CA!\[\overline {{\text{wt}}} \] = 2.8 g) to 1421 ± 184 in 1 + females (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbnL2yY9% 2CVzgDGmvyUnhitvMCPzgarmqr1ngBPrgitLxBI9gBaerbd9wDYLwz% YbItLDharuavP1wzZbItLDhis9wBH5garqqr1ngBPrgifHhDYfgasa% acOqpw0le9v8qqaqFD0xXdHaVhbbf9v8qqaqFr0xc9pk0xbba9q8Wq% Ffea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dme% aabaqaciGacaGaaeqabaWaaqaafaaakeaadaqdaaqaaiaabEhacaqG% 0baaaaaa!45CA!\[\overline {{\text{wt}}} \] = 6.6 g) and 1538 ± 449 in II + females (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbnL2yY9% 2CVzgDGmvyUnhitvMCPzgarmqr1ngBPrgitLxBI9gBaerbd9wDYLwz% YbItLDharuavP1wzZbItLDhis9wBH5garqqr1ngBPrgifHhDYfgasa% acOqpw0le9v8qqaqFD0xXdHaVhbbf9v8qqaqFr0xc9pk0xbba9q8Wq% Ffea0-yr0RYxir-Jbba9q8aq0-yq-He9q8qqQ8frFve9Fve9Ff0dme% aabaqaciGacaGaaeqabaWaaqaafaaakeaadaqdaaqaaiaabEhacaqG% 0baaaaaa!45CA!\[\overline {{\text{wt}}} \] = 8.4 g). The mean diameter of mature, preserved eggs was 1.3 mm. A comparison of the data presented in this paper for G. occidentalis with those recorded for other galaxiids shows that spawning time, fecundity and egg size vary markedly within the family Galaxiidae.