Six sites were sampled from the region during autumn and spring 2017. They were located from Spring Creek near Wilmington and Pekina Creek near Orroroo in the south to Willow Creek near Hawker in the north. Land use was dominated by agriculture (stock grazing and cereal cropping) on the flatter land, with grazing of remnant native vegetation and conservation areas confined to the steeper ranges around the Melrose to Wilmington area (including Mount Remarkable National Park) and Mount Plantagenet to the east from Hawker.
Sites monitored in the Northern and Yorke region during 2017 were considered to be in a Good to Poor condition. No sites were assigned to either the Excellent, Very Good or Very Poor classes and given the scale of vegetation clearance and nutrient enrichment evident in 2017, it is unlikely that any stream in the region remains unaffected by human activities. Of the sites assessed, two sites (33%) were in a Good condition with only minor changes to animal and plant life; two sites (33%) were in Fair condition with moderate changes to animal and plant life, and some changes to the way the ecosystems functioned; and two sites (33%) were in Poor condition with evidence of major changes in animal and plant life, and moderate changes to the way the ecosystems functioned.
The better sites were located in well vegetated catchments to the east from Hawker (Willow Creek) and near Wilmington in Mount Remarkable National Park (Spring Creek). These sites were characterised by good riparian habitats dominated by natural vegetation that included a range of coarse and fine sediments, and showed little to no bank erosion caused by stock accessing the banks or streambed during the year. Spring Creek maintained wetted pool habitats during both seasons and showed evidence of nutrient enrichment but was not obviously overwhelmed by some of the problems often associated with eutrophication (eg low dissolved oxygen and loss of sensitive species).
The sites assigned Fair ratings generally showed more evidence of nutrient enrichment (eg high nutrient concentrations, large growths of algae and/or aquatic plants, anaerobic sediments, dominance by plant and detrital feeding macroinvertebrates). They included Pekina creek upstream from the reservoir and the normally saline Kanyaka Creek that drains into Willochra Creek.
The two sites sampled from Willochra Creek were assigned Poor ratings. Both sites were highly saline and nutrient enriched, and supported depauperate aquatic communities dominated by tolerant and generalist species.
The aquatic macroinvertebrate communities of the water-holding streams were dominated by very tolerant, generalist species that occasionally included low numbers of a few rare and sensitive species. The waterbugs (Micronecta, Enithares and Anisops), amphipod crustacean (Austrochiltonia) and baetid mayfly (Cloeon) were usually the most abundantly collected macroinvertebrates, along with chironomids (including Paramerina, Tanytarsus, Chironomus and Dicrotendipes) and dytiscid beetle larvae and adults (Necterosoma). The pool habitats of streams in the region also supported low numbers of freshwater limpets, snails, yabbies, beetles, mosquitoes, biting midges, dragonflies, damselflies and leptocerid caddisflies.
Small flowing riffle habitat were only recorded at the two Willochra Creek sites but they lacked any flow dependent species.
Spring Creek was the only site that supported the regionally rare and sensitive leptophlebiid mayfly (Thraulophlebia inconspicua), a species with a restricted distribution to streams in the Mount Remarkable area of the Flinders Ranges. A more widely distributed and tolerant baetid mayfly (Cloeon) was collected from Pekina Creek and Kanyaka Creek, with the latter record in spring notable because the creek had a salinity of about 5,500 mg/L. Several molluscs (Ferrissia, Isidorella and Glyptophysa) were also collected from Spring Creek and Pekina Creek, otherwise they were absent from the more saline streams in the region.
The only fish recorded from the region included the introduced mosquitofish (Gambusia) from Pekina Creek in autumn and the native Lake Eyre Hardyhead (Craterocephalus eyresii) from the two Willochra Creek sites in spring. These fish species had a similar distribution in 2012 and it appears that lower Flinders Ranges streams may be too ephemeral or saline to support the much wider diversity of fish that occur further south in the Broughton and Wakefield River catchments within the Northern & Yorke NRM region.
The majority of streams in the region have limited riparian habitats with the fresher creeks supporting a narrow stand of large River Red Gums on each bank over introduced grasses, weeds and patches of sedges or rushes. Willochra Creek is too saline to support gum trees and the only plants commonly found on the banks are low chenopod shrubs (e.g. samphire).
Few rare or sensitive macroinvertebrates were recorded from the region in 2017 but the most notable were the presence of the leptophlebiid mayfly (Thraulophlebia inconspicua) from Spring Creek and the baetid mayfly (Cloeon) from Pekina and Kanyaka creeks. A number of molluscs, mites, beetles and caddisflies have also only been occasionally collected from the region in the past but there is limited information on their distribution and life history needs to confirm their regional significance in these assessments at this stage.
The only native species of fish recorded during 2017 was the Lake Eyre Hardyhead (Craterocephalus eyresii) which co-occurred with the introduced pest Mosquitofish at the two most saline sites sampled on Willochra Creek in 2012. The hardyhead is commonly found from streams in the Lake Eyre Basin, so its presence in part of the Lake Torrens Basin suggests some fish obviously moved between basins during a wetter period in the past.
