Browsing by Author "Joy, Michael Kevin"

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    The development of predictive models to enhance biological assessment of riverine systems in New Zealand : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Palmerston North, New Zealand
    (Massey University, 2003) Joy, Michael Kevin
    A suite of new regional and national lotic freshwater bioassessment tools were developed for New Zealand. This work permits the inclusion of freshwater fish in bioassessment, a component of the fauna previously largely ignored. The multivariate predictive models developed gave a number of advantages over the existing albeit overextended single-index approach (the macroinvertebrate community index) used by regional authorities. To acquire the data for constructing the models more than 500 sites were sampled over three North Island regions. The sites were selected to represent least impacted conditions known as reference sites so that the biotic communities sampled would representing the best attainable or the goal for resource managers. Models were constructed to predict the biota representing best available conditions based on the non human influenced physicochemical variables defining the sites. The predicted and observed assemblages were then compared using an observed over expected ratio (O/E) so that scores less than 1 represent less [i.e. fewer] species observed than expected. This (O/E) ratio is more than simply the assessment of species richness, as only those species predicted are included in the ratio. Reference site multivariate predictive models using fish and macroinvertebrate assemblage groups were developed for bioassessment in the Manawatu-Wanganui Region. Two reference site multivariate predictive models using individual fish and decapod species were developed for the Auckland region. The first used traditional linear discriminant function analysis and the second used artificial neural networks (ANNs). A model to predict the spatial occurrence of fish and decapods was developed for fish in the Wellington Region using Geographic Information Systems (GIS) and ANNs. The remotely sensed data was available for all rivers in the region so the predictions could be extended over the entire stream network to produce a fish map. Finally an index of biotic integrity (IBI) using fish was developed for the entire country and evaluated using remotely assessed environmental data. Exhaustive evaluations of predictions from all the models confirmed their credibility as a biomonitoring.
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    Freshwater fish community structure in Taranaki : dams, diadromy or habitat quality? : a thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Ecology at Massey University
    (Massey University, 1999) Joy, Michael Kevin
    The relationships between freshwater fish community structure and habitat characteristics including dams were examined at 85 sites on 38 waterways draining Mount Taranaki during the summer of 1997/98. Thirteen native and two exotic fish species were captured. Four groupings were identified based on species composition. The first two were high elevation site groups: one dominated by the diadromous Galaxiids: shortjawed kokopu, banded kokopu and koaro, the other dominated by longfin eels. The third group of sites was a mid-elevation group dominated by redfin bullies and longfin eels while the fourth group was made up of low elevation sites dominated by redfin bullies and shortfin eels. Discriminant analysis revealed that distance from the sea, site elevation and the presence of dams were the environmental variables most strongly associated with fish distribution patterns. Data from the New Zealand freshwater fish database (NZFFD) were used to examine the influence of dams and other environmental variables on the fish communities. The sites listed in the NZFFD as having free migratory access were used as reference sites for the construction of a predictive model of fish community assemblage. The species found at test sites were compared with the predicted assemblage and an observed over predicted ratio (O/P) produced for each test site in order to evaluate the relative impact of migratory barriers. The 85 sites from the 1997/98 survey, which were independent of the reference sites used in the model, were used as a test of the model. The O/P ratios were significantly lower for sites above barriers when compared with sites with free access. To demonstrate the use of the model, the impact of the Motukawa dam on fish communities was analysed by comparing the O/P ratios for sites above and below the dam. The resulting ratios were significantly lower above the dam, indicating that the dam was having a negative impact on fish communities. Distinctive trajectories of occurrence were detected for 13 species from the Taranaki ring plain. The diadromous species were ranked based on their ability to penetrate inland to enable comparison with other regions. The Taranaki rankings were consistent with rankings for the same species from the West Coast of the South Island. The high proportion of diadromous species in the Taranaki fauna means that access is of primary importance in structuring the fish communities and the large number of dams in the region has had a discernable negative effect on freshwater fish communities.