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Estuarine species:

year-to-year changes in abundance

in the lower Hastings River

High flows Hastings from 1997.png
Estuary species Hastings.png
Low flows-96-onwards.png
Estuary species Hastings.png

 What is likely to explain these year-to-year changes (up to 2018)?

For Yellow-finned bream:

  • positive role of the duration of moderate and high  flows in the previous month (see correlations below)

  • negative role of the duration of low  flows in the previous month (see correlations below)

  • positive role of La nina tending conditions (see correlations below)

For Estuary perchlets:

  • positive role of the duration of low  flows in the previous month (see correlations below),

  • negative role of the duration of higher  flows in the previous month (see correlations below),

  • positive role of the duration of lower  flows in the previous year (see correlations below)

  • negative role of the duration of higher  flows in the previous year (see correlations below),

  • positive role of El nino tending conditions (see correlations below)

For Common Silverbiddys:

  • positive role of the duration of moderate to high flows in the previous month (see correlations below)

  • negative role of the duration of lower  flows in the previous month (see correlations below),

  • positive role of La nina tending conditions (see correlations below)

For Dusky Flathead:

  • positive role of El nino tending conditions (see correlations below)

For Snub-nosed garfish:

  • positive role of the duration of higher flows in the previous month (see correlations below)

For the total abundance of estuarine species:

  • positive role of the duration of moderate to high flows in the previous month (see correlations below)

  • negative role of the duration of lower  flows in the previous month (see correlations below),

For the number of estuarine species:

  • negative role of the duration of near-zero flows in the previous year (see correlations below)

  • positive role of El nino tending conditions (see correlations below)

Estuarine species Hasting correlations O
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.
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