Date of Award

1997

Degree Type

Thesis

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Science and Technology

First Advisor

Dr Pierre Horwitz

Second Advisor

Prof Alan Bittles

Abstract

This study resulted from concerns for the present and proposed movement of barramundi (Lates catcarifer) across presumed population genetic boundaries into the Kimberley region of Western Australia for net-pen aquaculture and a recreational fishery development in dams no longer available to seasonal barramundi dispersal. Direct DNA sequencing of the non-recombining, maternally inherited mitochondrial genome of barramundi thought to represent wild populations from a broad section of a still wider Australian range were used for phylogenetic reconstructions that support hypotheses for historic gene flow between Kimberley and other populations during Recent sea level fluctuations. Nil or low levels of genetic diversity in samples beyond the Kimberley were reflected in highly significant estimates of population genetic subdivision and low gene flow between the contemporary Kimberley population and elsewhere. The observed population genetic structure of western Australian barramundi is discussed with regard to the island and isolation by distance models, however limited sampling and an absence of demographic data leaves a conclusion problematic. Stochastic, but long distance gene flow is predicted within Kimberley barramundi, and is discussed in relation to a distinct east-trending environmental cline that is thought to influence habitat availability and subsequent juvenile dispersal. The effects of hybridization due to stock enhancement or escapement are discussed in the context of the management objective, which is to maintain genetic diversity. Given this, there are clear implications for hatchery practices and wild fishery management in the Kimberley, which leaves the present translocation of barramundi a questionable practice that should not occur unless no contravention of the management objective can be assured.

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