Geographic Information System (GIS) was used to identify potential reference sites for wadeable stream monitoring, and multivariate analyses were applied to test whether invertebrate communities reflected a priori spatial and stream type classifications. We identified potential reference sites in segments with unmodified vegetation cover adjacent to the stream and in >85% of the upstream catchment. We then used various landcover, amenity and environmental impact databases to eliminate sites that had potential anthropogenic influences upstream and that fell into a range of access classes. Each site identified by this process was coded by four dominant stream classes and seven zones, and 119 candidate sites were randomly selected for follow-up assessment. This process yielded 16 sites conforming to reference site criteria using a conditional-probabilistic design, and these were augmented by an additional 14 existing or special interest reference sites. Non-metric multidimensional scaling (NMS) analysis of percent abundance invertebrate data indicated significant differences in community composition among some of the zones and stream classes identified a priori providing qualified support for this framework in reference site selection. NMS analysis of a range standardised condition and diversity metrics derived from the invertebrate data indicated a core set of 26 closely related sites, and four outliers that were considered atypical of reference site conditions and subsequently dropped from the network. Use of GIS linked to stream typology, available spatial databases and aerial photography greatly enhanced the objectivity and efficiency of reference site selection. The multi-metric ordination approach reduced variability among stream types and bias associated with non-random site selection, and provided an effective way to identify representative reference sites.
Fine-mesh monofilament gill nets were deployed within the three shallow lakes of the Rotopiko complex, Waikato, New Zealand to assess their potential as a tool for controlling or eradicating rudd (Scardinius erythrophthalmus). Nets of different mesh sizes were placed at different spacings and orientations throughout the lakes for two fishing periods, to determine methodology to be used for intensive removal. Rudd were intensively netted for a further two periods and then the success of the operations was assessed. Gill nets of a 13-mm mesh were more effective at capturing rudd when set perpendicular rather than parallel to the shore, whereas there was no significant effect of orientation in 25 mm and 38 mm nets. Comparisons of catch per unit effort (CPUE) on the first night of fishing for M03087; Online publication date 3 August 2004 Received 2 December 2003; accepted 28 April 2004each fishing period showed a significant reduction in the initial CPUE as fishing proceeded. A reduction in the numbers of rudd captured was most marked in the 38 mm nets. 80% of rudd captured over a 7-night period were caught in the first 3 nights of fishing. Post-removal sampling using gill, fyke, and trammel nets, and an electric fishing boat, showed that rudd remained in all of the lakes following intensive removal efforts. However, relative to other methods currently available in New Zealand for control or eradication of unwanted fish, monofilament gill nets appear to be a potentially viable and cost-effective option where ongoing control may provide sustained conservation outcomes.
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