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Fluctuating asymmetry of fish populations as a bioindicator of environmental quality in aquatic ecosystems

Utayopas, Poranee (1997) Fluctuating asymmetry of fish populations as a bioindicator of environmental quality in aquatic ecosystems. PhD thesis, Murdoch University.

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A study of fluctuating asymmetry (FA) in two species of fish; the Swan River goby (Pseudogobius olorum) and the mosquitofish (Gambusia holbrooki) was undertaken at wetlands in Perth, Western Australia. Although significant levels of FA were recorded, no clear relationships between FA and the concentrations of pollutants were found. Physicochemical stress, ecological stress and genetic factors were hypothesized to be causative factors of the FA detected.

A laboratory investigation based on the experimental effects of temperature, conductivity and food availability on G. holbrooki collected from Lake Jandabup and Lake Carabooda revealed significant correlations between these factors and FA in fish from both wetlands. However, the response of FA to experimental treatments differed between fish from the two water bodies. The differing results appeared to be the result of different genetic composition arising from adaptation to differing conditions within each wetland.

Multicomparison tests of FA in G. holbrooki collected from wetlands of differing pH, colour and nutrient status revealed no significant differences in FA among locations, however high levels of FA were detected in fish from Kogolup Lake, Mussel Pool, Lake Jandabup and Bibra Lake. Whether low pH or other stresses were the causative factors could not be determined. Fluctuating asymmetry appeared to be influenced by nonspecific, complex stresses occurring within the wetlands and so does not appear to be a useful bioindicator with respect to specific pollutants events.

The lack of significant differences in levels of FA in G. holbrooki from Perth wetlands and those of G. affinis from heavily polluted waterbodies in Bangkok, Thailand appeared to be the result of local adaptation of the Thai fish to heavily polluted environments. However, FA in fish from the most highly polluted site in Thailand ranked most highly. In addition, the FA of fish (pooled) from all Perth wetlands was significantly lower than those of all sites in Thailand. The lack of differences of FA in G. holbrooki collected before and after an application of a herbicide (glyphosate) in the Canning River may have been due to the small pre-treatment sample size, the presence of other factors obscuring the impacts of the herbicide, or the low persistence of the herbicide in environment.

Detection of high levels of FA and deformity in particular characters appeared to be a function of fitness, stage, time of development as well as low canalization of these characters. High levels of FA detected in some meristic characters appeared to be the result of low canalization. Deformities were detected in fish in the natural environment but were lower in number and level. The reasons why deformities occurred in different characters at different wetlands were not known. Possibly different stressors were present or the fish were adapted to different conditions.

The finding that physico-chemical and ecological factors may have a greater influence on FA than pollutants supports the results of previous studies. Improvement in the ecological status of degraded wetlands is recommended and suggestions as to further research needed on FA as an bioindicator for developmental stability are provided.

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): Davis, Jenny
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