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The biology of four species of native and two species of introduced fish in south-western Australia

Pen, Luke Jerome (1990) The biology of four species of native and two species of introduced fish in south-western Australia. PhD thesis, Murdoch University.

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A seine net (3 mm mesh), and where necessary other methods, were used to collect three native species (Galaxias occidental is, Bostockia porosa and Edelia vittata) and two introduced species (Gambusia affinis and Perea fluviatilis) at regular intervals from the southern branch of the Collie River. The same net was used to sample the native species Galaxiella munda from a tributary of the Warren River 120 km further south in Western Australia. Annuli on otoliths and the seasonal trends shown by gonadal development, including changes in oocyte diameter, were used to determine the age and the duration and peak time of spawning of each of the four native species.

Spawning of all four native species, which follows a movement into either tributary creeks or flood waters, takes place between mid-winter and mid-spring, with the peak time of spawning differing slightly amongst species. While sexual maturity is reached by G. occidentals, E. vittata and G. munda at the end of the first year of life, it is not attained by B. porosa until the end of the second year of life. Each species can live for five or six years, except G. munda which dies before it reaches two years of age. The breeding of G. afTinis occurs in the shallows between mid-spring and late summer, while that of P. fluviatilis takes place in deeper water in the spring.

Amongst the native species, G. occidentals and B. porosa spawn only once in a breeding season, whereas E. vittata and G. munda are multiple spawners, producing clutches of eggs at intervals throughout the spawning period. The relationships between the age and size at first maturity and the growth rate and spawning mode of these four species are discussed. The influence of growth of the females of G. affinis during the spring and summer on the number of live young they produce is determined.

All of the above native and introduced species are carnivorous. At most times of the year, the diets of G. occidentals and 0+ P. fluviatilis, which were characterised by insects from the water surface and copepods from the plankton respectively, showed little overlap with those of other species. Although B. porosa and E. vittata both fed predominantly on benthic invertebrates, the former species ingested a greater amount of larger prey and fed at night rather than during the day. The diets of G. affinis varied considerably at different times and in different locations, indicating that this species was particularly opportunistic and could focus on prey which were abundant.

Comparisons are made between the biology of native fish in the highly seasonal environment of south-western Australia and those of the same and other families in eastern Australia and New Zealand.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Biological and Environmental Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Potter, Ian
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