Kevin J. Collier

Dispersal of adult caddisflies (Trichoptera) into forests alongside three New Zealand streams

The abundance and taxonomic richness of adult caddisfly faunas were determined at varing distances (up to 200 m) away from three North Island, New Zealand, streams to help define appropriate forested riparian zone widths for adult aquatic insects. Adults were collected using sticky traps and ultraviolet light traps on four occasions over summer. Light traps were more effective at catching caddisflies than sticky traps, but both methods gave similar patterns of declining abundance and taxonomic richness with distance from the stream edge. Abundances of total caddisflies at 20 m were <21% of those caught at the stream edge for both trapping techniques. The same trends were evident for abundances of most common species in light traps, whereas bimodal peaks were evident with distance from the channel edge for percentage females of three common species. More than 30% of species caught at the stream edge was found in light traps at least 70 m into forest at all sites. A faster rate of decline for abundance than richness with distance away from the stream reflected the relatively large distances travelled by representatives of many species. Similar results from the three sites for numbers and species richness indicate that the main area of activity for adult Trichoptera in forested riparian zones was within 30 m of the stream edge at these sites.

Effects of crayfish (Paranephrops planifrons: Parastacidae) on in-stream processes and benthic faunas: a density manipulation experiment

Abstract The effects of New Zealand freshwater crayfish or koura (Paranephrops planifrons: Parastacidae) on organic matter processing, sediment accumulation, and benthic invertebrate communities were investigated using four replicate treatments of 0 (control), 4–5 (medium), and 8–11 (high) similar‐sized koura in 0.5 m2 artificial stream channels colonised by benthic invertebrates from a pasture stream, Waikato, New Zealand. Wineberry (Aristotelia serrata) leaf packs were placed in each channel and after 7 weeks the leaf matter remaining was significantly lower in both medium and high koura channels than in controls. The amount of sediment (surficial cover by fines and weight of suspendable sediment) was also significantly reduced in high koura density channels. Densities of invertebrates other than crayfish were not significantly different among treatments; however, taxa richness and invertebrate biomass were significantly lower in high koura channels than in controls. Our results suggest that freshwater ...

Evaluating techniques for sampling stream crayfish (paranephrops planifrons)

We evaluated several capture and analysis techniques for estimating abundance and size structure of freshwater crayfish (Paranephrops planifrons) (koura) from a forested North Island, New Zealand stream to provide a methodological basis for future population studies. Direct observation at night and collecting with baited traps were not considered useful. A quadrat sampler was highly biased toward collecting small individuals. Handnetting at night and estimating abundances using the depletion method were not as efficient as handnetting on different dates and analysing by a mark-recapture technique. Electrofishing was effective in collecting koura from different habitats and resulted in the highest abundance estimates, and mark-recapture estimates appeared to be more precise than depletion estimates, especially if multiple recaptures were made. Handnetting captured more large crayfish relative electrofishing or the quadrat sampler. to

Influence of substrate type and physico‐chemical conditions on macroinvertebrate faunas and biotic indices of some lowland Waikato, New Zealand, streams

Abstract Lowland streams in agricultural areas are often considered degraded because of high turbidity, high biomass of adventive macrophytes, and a predominance of fine bed substrates. Invertebrate faunas in these streams are being increasingly used in biomonitoring, and an understanding of factors affecting their distribution and abundance is important for interpreting the results of these studies. We measured physico‐chemical parameters and sampled macroinvertebrate faunas on inorganic substrates, wood, and macrophytes to investigate factors influencing invertebrate distribution and abundance in Waikato, New Zealand, lowland streams, and to evaluate six biotic indices and a rapid bioassessment protocol for lowland stream environments. At most sites, invertebrate faunas were dominated numerically on all substrate types by the hydrobiid snail Potamopyrgus antipodarum (Gray), the eusirid amphipod Paracalliope, and Diptera (mostly the chironomid Neonella forsythii Boothroyd and the blackfly Austrosimulium ...

Environmental factors affecting the taxonomic composition of aquatic macroinvertebrate communities in lowland waterways of Northland, New Zealand

Abstract Environmental data and aquatic macroinvertebrates colonising macrophytes or stones were collected at 29 stream and river sites in Northland, New Zealand, in February 1994 to elucidate environmental factors influencing the taxonomic composition of invertebrate communities. The 84 taxa recorded in February comprised predominantly Trichoptera (24 taxa), Ephe‐meroptera (17), and Diptera (14). Substrate type (macrophytes or stones) and percentage of native forest up stream or in the riparian zone appeared to be factors affecting classification of sites in TWINSPAN. Although catchment land use or riparian vegetation were not implicated as major factors affecting taxonomic richness or overall community composition (as indicated by DECORANA) at stony sites, the number of mayfly, stonefly, and caddisfly taxa was significantly correlated with the proportion of native forest cover in the riparian zone. Overall taxonomic richness and community composition appeared to be affected by small‐ to medium‐scale fac...

Interaction of Press and Pulse Disturbance on Crayfish Populations: Flood Impacts in Pasture and Forest Streams

Interactions between press and pulse disturbances can significantly impact benthic macroinvertebrate (crayfish) populations. Press disturbances such as land-use change can make crayfish more vulnerable to the detrimental effects of pulse disturbances, by changing the habitats available to crayfish. The impact of a pulse disturbance, a major flood (1 in 28 years return period), on crayfish (Paranephrops planifrons) was significantly greater in pasture than native forest streams. Population densities of crayfish in three forest and three pasture streams had been measured seasonally for 2 years prior to the flood and many crayfish had been marked with individually identifiable tags. Low numbers of marked crayfish were recaptured after the flood in the forest streams, but no marked crayfish were identified in any pasture stream. Crayfish densities in one pasture stream declined from an average of 5 m−2 prior to the flood to <1 m−2 soon after the flood and it took 3 years for the population to show evidence of recovery. Macrophytes and cobbles, the dominant habitats of crayfish in pasture streams, did not appear to provide stable refugia during the flood. Habitat stability was linked to the riparian zone in forest streams where undercut banks, tree roots, and pools were important habitats for crayfish. Frequent pulse disturbance could affect population persistence of refugia-dependent species when the pressure of land-use change affects the stability of habitats, but this may only be evident over long time scales.

Summer light‐trap catches of adult Trichoptera in hill‐country catchments of contrasting land use, Waikato, New Zealand

Abstract The distribution of adult Trichoptera in light traps was investigated alongside nine streams draining catchments under native forest, pine forest, or pasture near Hamilton, Waikato, New Zealand. The aim of the study was to determine the relationship between abundance, taxonomic richness, and community composition with respect to land use during summer, and to evaluate the use of adult Trichoptera compared with benthic invertebrates as potential bio‐indicators of the effectiveness of land‐management changes. Adult Trichoptera faunas alongside the native streams were dominated by Hydrobiosidae, Conoesucidae, and Helicopsychidae (each >10% of total Trichoptera numbers for at least two of the three sites), whereas Leptoceridae, Oeconescidae, and Hydrobiosidae were relatively abundant alongside at least two of the pine sites. Adult Trichoptera faunas at the pasture sites were strongly dominated by Hydroptilidae which made up 47–85% of numbers caught at all sites. The mean number of individuals and tax...

Growth and population dynamics of crayfish Paranephrops planifrons in streams within native forest and pastoral land uses

Abstract Population dynamics of crayfish (Paranephrops planifrons White) in streams draining native forest and pastoral catchments, Waikato, New Zealand, were investigated from September 1996 to July 1998. Crayfish densities were generally greater in native forest streams because of high recruitment over summer, but varied greatly between streams in both land uses. Peak densities in summer were 9 crayfish m‐2 in native forest and 6 crayfish m‐2 in pasture streams, but peak biomass in summer was much greater in pasture streams. Mark‐recapture data showed that crayfish, particularly juveniles, in pasture streams grew faster than in native forest streams, through both greater moult frequency and larger moult increments. Females reached reproductive size at c. 20 mm orbit‐carapace length (OCL) after their first year in pasture streams, but after 2 years in native forest streams. Annual degree days >10°C appeared to explain the differences in the timing of life cycles. Estimates of annual crayfish production (range = 0.8–3.4 g dry weight m‐2 year–1) were similar in both land uses, and P/B ratios were between 0.95 and 1.2. Despite deforestation and conversion to pasture, crayfish in these Waikato hill‐country streams have maintained similar levels of annual production to those in native forest streams, although juvenile growth rates have increased and longevity has decreased.

Interactions of Adult Stoneflies (Plecoptera) with Riparian Zones I. Effects of Air Temperature and Humidity on Longevity

The effects of constant air temperature and relative humidity on the longevity of three species of gripopterygid stonefly adults from New Zealand were investigated in laboratory experiments, and the results were compared to field measurements of air temperature and humidity obtained during summer. Greatest longevity for Zelandobius furcillatus, Zelandoperla decorata and Acroperla trivacuata was recorded in cool humid conditions (10°C, 100% humidity) for adults fed water and a 5% sucrose solution. Absence of feeding reduced survival by 37–73% at 17°C and 100% humidity. Survival decreased significantly with increasing constant air temperature (10, 17 and 25°C) and decreasing mean relative humidity (100, 81 and 15%). Males survived significantly longer than females in all temperature treatments for Z. furcillatus, but longevity was not influenced by gender in other species or in the humidity experiments. Interpolated LT 50 values over 96 h for female stoneflies in the temperature treatments averaged of 22–23°C. Field measurements at near-ground level and 1.5 m above the streambank during summer indicated that these air temperatures were exceeded for 25% of the time in a pasture catchment compared to <0.1% of the time in a native forest catchment. These findings implicate air temperature as a factor potentially influencing the longevity of adult stoneflies, and suggest that maintenance of appropriate microclimate conditions should be a consideration in riparian management.

Role of wood in pumice-bed streams: I: Impacts of post-harvest management on water quality, habitat and benthic invertebrates

Abstract Harvesting slash was experimentally manipulated in three headwater, spring-fed, pumice-bed streams draining Pinus radiata catchments in the central North Island, New Zealand. Changes in water quality, benthic sediments, organic matter and invertebrate communities were studied up to 5 years after (i) removal of most wood from the channel (low-wood site), (ii) removal of large wood only (medium-wood site), and (iii) retention of all wood (high-wood site). We detected minor effects of wood treatment on water temperature, short-term effects on dissolved organic carbon, nitrite-nitrogen and dissolved reactive phosphorus concentrations ( 1 year). Post-harvest dry mass of stored benthic organic matter declined at all sites over 1–3 years to levels recorded at an unharvested reference site. In contrast, changes in the percentage of surficial sand and gravels were still evident 5 years after treatment. Significant temporal differences in the taxonomic richness and density of benthic invertebrate faunas were detected at all treatment sites, and initially appeared to reflect degree of channel disturbance during harvesting and wood management. Following these initial impacts, richness and densities of some major invertebrate groups increased as successional taxa colonised streams, apparently in response to trophic subsidies from organic matter inputs or increased primary production, and recovery of sites from disturbance. Pre-harvest and reference site invertebrate community composition was considerably different from that at the low-wood site until 1 year after treatment, and at the high-wood site until 3 years post-treatment when communities at all sites were broadly similar. By carrying out a medium-term study and manipulating stream channel wood along the length of perennial flow in headwater basins, we have provided a basis for understanding the magnitude and duration of ecological impacts, and the timescales of recovery associated with different post-harvest wood management approaches in pumice-bed stream ecosystems.