Ten sites were sampled from the region during autumn and spring 2015. They were located among the southern and south-central parts of the peninsula. Land use mostly consisted of agriculture (grazing and cereal cropping) with patches of remnant native vegetation largely confined to the steeper, rocky hills, gullies, roadside vegetation and along creeklines.
Sites monitored from the Eyre Peninsula in 2015 were considered to be in a Fair to Very Poor condition. No sites were assigned to either the Excellent, Very Good or Good condition classes and may no longer exist in the region given the scale of vegetation clearance, salinisation and nutrient enrichment evident in 2015; similar results were also obtained in 2010 from 30 sites, supporting the view that streams throughout the region are in a degraded condition.
Of the sites assessed in 2015, 4 (40%) were in Fair condition, with moderate changes to animal and plant life, and some changes to the way the ecosystems functioned; 4 (40%) were considered to be in Poor condition, with evidence of major changes in the animal and plant life, and moderate changes to the way the ecosystems functioned; and two (20%) were considered to be in Very Poor condition, with evidence of major changes in the animal and plant life and the way the ecosystems functioned.
The better sites were located from the mid and upper reaches of the Tod River, including sites from near White Flat, Tod Reservoir, Koppio and Yallunda Flat. They were characterised by low to moderately diverse saline tolerant macroinvertebrate communities, moderate salinities for Eyre Peninsula streams, and generally only moderate evidence of significant nutrient enrichment. In contrast, the worst sites included Rock Valley Creek near Koppio and the Driver River near Verran. These sites had very sparse aquatic faunas comprising only the most saline tolerant species, very high salinity and nutrient concentrations, and poor riparian habitats.
Salinity is obviously a major issue on Eyre Peninsula with most streams considered to be saline (e.g. salinity > 3000 mg/L). None of the sites sampled in 2015 approached this threshold, with the lowest recorded salinity of 4,700 mg/L recorded from the Tod River, Koppio in spring. The other sites sampled from mid and upper reaches of the Tod River had salinities in the 5-7,000 mg/L range but most streams were higher, with the highest recorded salinity recorded from the Driver River in spring (39,985 mg/L). In contrast, three sites in 2010 were only moderately fresh (salinity 1,000-3,000 mg/L), including Poonana and Yeldulknie creeks near Cleve and Coonta Creek near Tumby Bay but the others were all saline.
All sites showed evidence of significant nutrient enrichment, including high concentrations of nitrogen and/or phosphorus and large growths of either filamentous algae, phytoplankton or aquatic plants such as reeds, sedges and rushes recorded from each stream. Most streams had significantly disturbed riparian zones with cropping or other introduced grasses and weeds often dominating the plants growing on banks that lacked extensive tree and shrub cover. Surface runoff from agricultural lands and bank erosion from stock (cattle and sheep) accessing riparian zones were also significant stressors affecting the condition of many streams in the region.
The aquatic macroinvertebrate communities of most streams were dominated by a few saline tolerant species and no site sampled in 2015 supported any rare or sensitive species. An amphipod crustacean (Austrochiltonia australis) was usually the most abundant macroinvertebrate, along with chironomids (Procladius, Chironomus, Tanytarsus, Dicrotendipes and Paramerina), waterbugs (Anisops and Sigara), snails (Coxiella and Potamopyrgus) and various beetles, mites, damselflies and yabbies. The only flow dependent species were a few tolerant blackfly larvae (Simulium ornatipes) that were collected from flowing habitats on the Tod River near the Tod Reservoir and further upstream at Koppio. The lack of sensitive groups such as mayflies and stoneflies highlights the lack of flowing, freshwater habitats in the region. The only caddisflies collected were several commonly collected saline tolerant species (eg Hellyethira simplex, Notalina spira and Triplectides australis) from sites in the mid and upper reaches of the Tod River but none of the more sensitive species were recorded.
No rare or sensitive species were found in the region in 2015 and the only flow-dependent species recorded were a few saline tolerant blackfly larvae from flowing riffle habitats in the Tod River upstream from the reservoir. Similar results were also obtained in 2010 when only one rare and regionally restricted species was collected, a saline tolerant caddisfly (Symphitoneuria wheeleri), and another tolerant flow-dependent caddisfly (Cheumatopsyche sp. 2) was found in saline riffle habitats. The region is notable due to the lack of many macroinvertebrate groups that are commonly found in freshwater streams from the southern part of South Australia, including bivalve molluscs, shrimps, prawns, mayflies, stoneflies, and a richer diversity of dipterans and caddisflies.
The only fish recorded in 2015 included the introduced Mosquitofish from several sites on the Tod River, unidentified hardyheads from coastal stream sites on Glengyle and Minniribbie creeks, and Western Blue-spotted Gobies near the estuary on the Tod River at North Shields. Similar fish species and distribution patterns were noted in 2010 but a threatened species called Climbing Galaxias (Galaxias brevipinnis) was also recorded from the Tod River near Whites Flat and another native species called Common Galaxias (Galaxias maculatus) was collected from the Unnamed Creek near Green Patch.
Previous sampling on Eyre Peninsula from the mid 1990-2000’s has included several other rare and uncommon species that were not recorded in either 2015 or 2010. They include a subterranean crustacean (Family Parabathynellidae), a mayfly (Cloeon), two beetles (Copelatus and Paroster), three chironomids (Botryocladius grape “th”, Apsectrotanypus and Paraheptagyia), a biting midge (Atrichopogon), three caddisflies (Ecnomus cygnitus, Hellyethira simplex and Oecetis) and the water measurer (Hydrometra). Most of these records came from either the Tod River catchment, Coonta or Yeldulknie creeks.
