Date of Award

1996

Degree Type

Thesis

Degree Name

Bachelor of Science Honours

Faculty

Faculty of Science, Technology and Engineering

Abstract

The Marron (Cherax tenuimanus) is arguably the most easily identified and ecologically important aquatic animal species in south-western Australian rivers. In fact it is quintessientially south-western Australian, endemic to the south-west corner of the continent and supporting a recreational fishery and commercial aquaculture industry within the state. Marron have keystone qualities as hosts of various epiphytic flora and fauna, and are central to the food web within south-west rivers. Their sensitivity to depleted oxygen conditions have also made them a potential "indicator" for water quality degradation. The study investigated these qualities in reference to the marron's potential as a flagship species for the restoration of the Blackwood River. Marron could, as flagships, provide direction and understanding for an already community driven catchment group, and provide a focal point for research, landcare, and foreshore restoration along the Blackwood River. According to a list of criterion for flagship species selection the study reviewed the literature on the scientific knowledge and ecological, cultural and economic value of marron within the south-west. The marron 's ability to recover from threatening processes within the Blackwood River was investigated, based on an earlier study in 1973. Seven pools within the Middle Catchment (the study area) were sampled for marron using a competitive density of drop nets within each pool, followed by the mapping of cross-sectional dissolved oxygen profiles. The upper limit of marron distribution was confirmed to be approximately 100km below the original upper limit maintained until the late 1950's. Depleting oxygen concentration associated with persistent stratification and organically enriched sediments and high water temperatures were identified to have the potential to lock marron out of pools, at certain times of the day during the summer months. These threatening conditions could be ameliorated with daily or seasonal holomixis and the flushing effect of winter rain, thus enabling marron recovery. A face to face questionnaire sampling the Middle Blackwood Catchment community was used to test the marron's ability, to evoke public sympathy and pride, and assess marron popularity and appeal. Marron fulfilled all criteria tested, with significant variation in opinion and attitudes identified between shires, gender of respondent, river use and those involved in the recreation of marron fishing. The study found marron to be an appropriate flagship species for restoration of the Blackwood River. It represents an appealing icon for tangible community understanding of the restoration process, and a biological indicator for monitoring change as restoration becomes effective, providing direction for restoration action, milestones for the community, and an endpoint for the restoration programme.

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