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Studies on the Hastings River, NSW

Where is the Hastings River and estuary (inland from Port Macquarie)?:

Studies areas are upstream and downstream of the tidal limit

Wauchope

Vegetation in the upper estuary study area

Fish abundance study area

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Two major studies in the Hastings (upper estuary and lower river):

Vegetation in the upper estuary (currently self funded)

Beds of freshwater vegetation in the upper estuary are very important places for fishes as they use these areas variously for sheltering, feeding, breeding and raising their young. Their importance parallels crayweed beds in the marine environment - "the biological engine of the southern reef" - which are now subject to recuperative efforts since their demise in the 1980s  (see crayweed project). 

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When river flows reduce during droughts, or importantly, as a result of water extraction, these upper estuary beds are threatened by the toxic effects of saltwater intruding up from the ocean.  Since 2000, the abundance and health of these beds has been regularly surveyed along an eight kilometre length of the upper estuary.

 

The objective of this work is to determine if  there are critical river flows  which, if passed (to lower levels), will result in a rapid increase in salt-induced damage to the beds. Having this knowledge is very important in developing effective environmental flows to protect the Hastings River from damage caused by water extraction. The word 'effective' is used as many environmental flow specifications have dubious effectiveness as they are based on 'informed' guesswork, rather than hard data such as that gathered in this study.

Fish abundance in the lower river (currently self funded)

At least twenty-five  species of fish have been recorded in the freshwaters of the Hastings River. These species are valued in various ways: recreational angling (e.g. Australian bass, yellow-finned bream and dusky flathead), conservation (e.g. Bellinger River catfish or east coast catfish), or from a commercial point of view (e.g. sea mullet). The abundance of these species varies greatly between years and there is very little scientific understanding of the factors which drive these changes. Without such an understanding it is impossible to distinguish between  changes caused by mans' activities and those simply caused by natural variation.

 

Since 1997, the abundance of the fishes has been  surveyed on a once-a-year basis at four sites in the lower-most four kilometers of the river. The technique used for survey is identified as 'Night-count transects' which is direct-observation, non-destructive approach that was initially develop within Kakadu National Park by the Federal Government in the 1980s. (This long-term data has no equals in Australian freshwater fish studies!)

 

The objective of this work is to determine if changes in the abundance of the fishes can be related to changing river flows. If this is the case, particularly in relation to the duration of lower river flows, the study will provide very important knowledge for the development of effective environmental flows to protect the Hastings River from damage caused by water extraction. As before, the word 'effective' is used as many environmental flow specifications have dubious effectiveness because they are based on 'informed' guesswork, rather than hard data such as that gathered in this study.

 

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