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East coast catfish or Wilang:
a high conservation value species
year-to-year changes in abundance
in the lower Hastings River
What is likely to explain these year-to-year changes (up to 2018)?
For catfish of all sizes:
-
positive role of the duration of high flows in the previous month (see correlations below)
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positive role of the duration of high flows in the previous year (see correlations below)
For adult catfish:
-
positive role of the duration of moderate and high flows in the previous month (see correlations below)
-
positive role of the duration of high flows in the previous year (see correlations below)
For juvenile catfish:
-
positive role of the duration of higher flows in the previous month (see correlations below)
-
positive role of the duration of higher flows in the previous year (see correlations below)
-
positive role of higher flows in the breeding season (Sep-Dec) in the same year (see correlations below)
Flow data
Note that in the early stages of this investigation reliance was placed on Koree Island flow data provided by Port Macquarie and Hastings Council, data they are required to gather so to effectively provide environmental flows (EF) and to inform their own EF investigations. The Council's last revision of the flow rating curve for the site was in late 2015 and so data gathered subsequently, particularly after a major flood that occurred in March 2017, has questionable reliability due to possible channel-form changes. Accordingly, additional reliance has been placed on flow data gathered further upstream at the Ellenborough gauging site. It is recognised that this data too has dubious reliability for understanding flow conditions in the lower river as approximately 500 square kilometers of catchment is present between the Ellenborough gauging site and Koree Island near the tidal limit.
Abundance patterns within the lower river:
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