Assessments of the stream and riparian environment are undertaken including stream classification (permanent, intermittent, or ephemeral), water quality, channel morphology, and availability of spawning habitat. Riparian vegetation is assessed and described.
Freshwater fish are sampled using a kick net, sweep net, Fyke traps, Gee minnow traps, spotlighting, or by electrofishing depending on the habitats present, the species to be sampled, and the project type. Wildlands staff have expertise in sampling Threatened and At Risk species, including mudfish (Neochanna spp.) and longfin eel (Anguilla dieffenbachii).
Freshwater macroinvertebrates are collected using the national protocol C2 (Stark et al. 2001), which involves using a D-net (0.5 mm mesh) to collect invertebrates from the water column, submerged wood, cobbles, bank margins, and macrophytes. Samples are preserved in ethanol for later analysis in a laboratory, where they are identified and counted. Assessments are made based on the abundances and pollution tolerance scores of individual taxa, the presence of Ephemeroptera (mayfly), Plecoptera (stonefly), and Trichoptera (caddisfly) (EPT) taxa, and Macroinvertebrate Community Index (MCI) scores.
Assessment of Ecological Effects
Wildlands staff have investigated the potential adverse effects of earthworks, stormwater discharge, stream diversion, piping, culverts, subdivision, and road and bridge construction on aquatic species and habitats.
Stream Ecological Valuation (SEV)
Stream Ecological Valuation is a comprehensive method for quantifying the value of aquatic ecosystems. The SEV method is the recommended method for assessing streams in the Auckland and Wellington Regions, but has also been applied successfully in other parts of New Zealand. The method uses a range of qualitative and quantitative variables to assess the main ecological functions of streams.
The SEV method assesses 14 ecological functions of streams, divided into four categories. Each function is weighted equally, with the resultant SEV score being the mean function score between 0 (a stream with no ecological value) and 1 (a pristine stream with maximum ecological value). The method allows even very different streams to be evaluated and compared. These function scores enable stream and catchment managers to understand the range of ecological services a stream provides.
When used in conjunction with an SEV for a second stream proposed as a site for compensating adverse effects on the impact stream, the SEV scores are used to determine an Environment Compensation Ratio, which in turn is used to calculate the total stream area required to ensure adequate mitigation to achieve “no net loss in ecological value”.
A comprehensive range of quantitative and qualitative assessments of the stream and riparian environment are made in the field. Data collection involves aquatic macroinvertebrate sampling, a fish survey, analysis of stream channel morphology (width, depth, and substrate particle size, or roughness) from ten transects across the stream, as well as a critical visual assessment of the entire reach that records a range of parameters. Field data are complemented by existing information derived by desktop analysis, such as the area of impervious surfaces, flooding frequency, and catchment size.
Wildlands can identify and describe opportunities to avoid, remedy, or mitigate adverse ecological effects on aquatic values such as indigenous riparian plantings, reinstatement of fish passage (e.g. by installing bypasses or ladders), enhancement of in-stream habitat, and undertaking fish rescue and relocation.