Hawkesbury-Nepean River Environmental Monitoring Program

Hypseleotris were caught only much farther upstream in Penrith Weir Pool and at
Wallacia.
• Pair-wise differences among sites were also significant in most cases, with the
exception of Devlin’s Lane and Penrith Weir Pool (ANOSIM, P = 0.542), Sackville
and Windsor (ANOSIM, P = 0.154) and Penrith Weir Pool and Windsor (ANOSIM,
P = 0.079).
• The multidimensional scaling ordination (Figure 6.21) is suggestive of longitudinal
variations in fish communities from downstream (Sackville) to upstream (Wallacia
and Mangrove Mountain) sites. This is perhaps not all that surprising considering
the differences in salinity and other physical attributes at these sites.
• Analysis of data sites with the longest history of sampling indicated no significant
difference among decades (1990s vs 2000s; ANOSIM, P = 0.183), although the
much lower frequency of sampling during the 2000s may have some bearing on
this conclusion (Figure 6.22).
• Proportional differences in the occurrence of some species (e.g. an increase in
proportional representation of goldfish) were suggested from the 1990s to 2000s
at these long-sampled sites, but this may simply be a result of the sampling frame
(i.e. the specific sites and times sampled during the 2000s decade).
• An attempt was made to look at length frequencies, but this served only to further
illustrate the sporadic nature of the sampling and the relatively low numbers of
individual fish species collected and measured at each site and time (Figure
6.23). Length frequencies for other species and sites are included in Appendix 7.
Figure 6.20: Proportional abundance of fish species at sites in the Hawkesbury-Nepean
River
Hawkesbury Nepean River Environmental Monitoring Program: Final Technical Report 49