Freshwater sawfish

A good video by the ABC on the sawfish threatened by the river diversion, shame that the same biologist promoting the sawfish helped get approval for the mine and River diversion.

 See video by Anne Barker Darwin ABC

More details on the freshwater sawfish

Here are some issues identified by the NT Government’s EPA report before the project was approved (EPA Assessment Report 54).
“However, the 2006 survey confirms that freshwater sawfish at least transit through the proposed project area. This transit, to upstream dry season refugial pools, may be necessary for the long-term maintenance of the local population of sawfish in the McArthur River, and hence it is important that the proposed development does not result in impedance of this movement….[T]here remains some uncertainty about the extent to which the designed rock riffles at the upstream portion of the diversion channel may act as a barrier to sawfish dispersal; and some uncertainty about the feasibility and timing of construction of a suitable diversion channel relative to the proposed timing of severing of the natural river channel. It is difficult to be more precise in the assessment of dispersal patterns, and the likelihood that development will affect these patterns, because there has been no baseline study of dispersal of freshwater sawfish in this river system. This is a notable limitation in the material presented.

“Other aspects of the proposed development pose risks to this local population of freshwater sawfish. The PER notes that aquifer drawdown will reduce the volume of water maintained in Djirrinminni Waterhole, particularly during the late dry season. The PER asserts that this waterhole is suboptimal as a dry season refuge for freshwater sawfish, but this assessment is based largely on a single wet season sampling, supported by generalisations about its presumed resource requirements. The proposed development will reduce habitat quality at this site, one of the few persistent pools in the mid- to upper-reaches of the McArthur River. The PER also notes that the lower McArthur River (notably the estuarine delta) may support more substantial populations of freshwater sawfish, at least during some times of year. There may be some risks to this potentially important population associated with either catastrophic release of contaminants from the mine or low-level chronic reductions in water quality. The 2006 survey does not represent a particularly comprehensive nor substantial baseline for the ongoing assessment of impacts upon freshwater sawfish; and does not provide any detail on dispersal patterns.

“The limited survey data demonstrate that the freshwater sawfish currently disperses (presumably as an essential component of its life history) along the McArthur River through the project area. Characteristics of this dispersal pattern remain unknown. There is substantial risk that this dispersal will be detrimentally affected by the proposed development.

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