Changes in the population structure of Ascophyllum nodosum (L.) Le Jolis due to mechanical harvesting

The use of a Norwegian suction cutter to harvest populations of the brown alga Ascophyllum nodosum (L.) Le Jolis in southwestern Nova Scotia started in 1985. The impact of this type of mechanical harvest on the algal population structure was evaluated. Changes in the length and density of individual plants (clumps) within 0.25 m^–2 quadrats, as well as the length of individual shoots within clumps were monitored before and after an experimental harvest. The mechanical harvest cut mainly the longer plants, thus changed the initial bimodal size structure of the population to unimodal. There was a 20 to 36% plant mortality, reducing the plant density from 92.6 to 73.6 individuals m^–2. Pre-harvest size distribution of the tagged shoots was skewed to the right and became more normal after the harvest. Tagged shoots in the harvested quadrats suffered a 42% mortality as compared to 11% of those in the control quadrats. An understanding of the impact of the mechanical harvesting on the harvested population is essential in the design of a management strategy. Sources of variation in the impact of mechanical harvest include the tide level at time of harvest, length of time the machine operated in one site, skill of the machine operator, and sharpness of the machine cutting blades.     

A Comparison of Soil Microbial Community Structure, Protozoa and Nematodes in Field Plots of Conventional and Genetically Modified Maize Expressing the Bacillus thuringiens is CryIAb Toxin

Field trials were established at three European sites (Denmark, Eastern France, South-West France) of genetically modified maize (Zea mays L.) expressing the CryIAb Bacillus thuringiensis toxin (Bt), the near-isogenic non-Bt cultivar, another conventional maize cultivar and grass. Soil from Denmark was sampled at sowing (May) and harvest (October) over two years (2002, 2003); from E France at harvest 2002, sowing and harvest 2003; and from SW France at sowing and harvest 2003. Samples were analysed for microbial community structure (2003 samples only) by community-level physiological-profiling (CLPP) and phospholipid fatty acid analysis (PLFA), and protozoa and nematodes in all samples. Individual differences within a site resulted from: greater nematode numbers under grass than maize on three occasions; different nematode populations under the conventional maize cultivars once; and two occasions when there was a reduced protozoan population under Bt maize compared to non-Bt maize. Microbial community structure within the sites only varied with grass compared to maize, with one occurrence of CLPP varying between maize cultivars (Bt versus a conventional cultivar). An overall comparison of Bt versus non-Bt maize across all three sites only revealed differences for nematodes, with a smaller population under the Bt maize. Nematode community structure was different at each site and the Bt effect was not confined to specific nematode taxa. The effect of the Bt maize was small and within the normal variation expected in these agricultural systems.     

Patterns and diversity in locomotor activity in spotted munia (Lonchura punctulata)

In a population, the individuals exhibit temporal spacing of their behaviours to avoid conflict with the environment and conspecific. In the present study, we have analysed the diversity in activity patterns in spotted munia (Lonchura punctulata) under laboratory conditions. Birds (n = 101) kept under 12L:12D and constant temperature conditions during summer and winter solstices of the year were monitored for their locomotor activity. All birds showed diurnal activity and exhibited different patterns such as unimodal (U), bimodal (B), trimodal (T) and amodal (A). Of these, U and B showed their subtypes (unimodal morning, UM; unimodal evening, UE; bimodal morning, BM; bimodal morning-evening, BME; bimodal evening, BE) also. The offset but not the onset of activity differed significantly among different types. These activity patterns appeared to be season independent. The results suggest that the diverse activity patterns in munia could be the result of “environmental imprinting” which may have ecological significance.     

An adaptive management approach to an octocoral fishery based on the Beverton-Holt model

Coral reef species are frequently the focus of bio-prospecting, and when promising bioactive compounds are identified there is often a need for the development of responsible harvesting based on relatively limited data. The Caribbean gorgonian Pseudopterogorgia elisabethae has been harvested in the Bahamas for over a decade. Data on population age structure and growth rates in conjunction with harvest data provide an opportunity to compare fishery practices and outcomes to those suggested by a Beverton-Holt fishery model. The model suggests a minimum colony size limit of 7–9 years of age (21–28 cm height), which would allow each colony 2–4 years of reproduction prior to harvesting. The Beverton-Holt model assumes that colonies at or above the minimum size limit are completely removed. In the P. elisabethae fishery, colonies are partially clipped and can be repeatedly harvested. Linear growth of surviving colonies was up to 3 times that predicted for colonies that were not harvested and biomass increase was up to 9 times greater than that predicted for undisturbed colonies. The survival of harvested colonies and compensatory growth increases yield, and yields at sites that had previously been harvested were generally greater than predicted by the Beverton-Holt model. The model also assumes recruitment is independent of fishing intensity, but lower numbers of young colonies in the fished populations, compared to unfished populations, suggest possible negative effects of the harvest on reproduction. This suggests the need for longer intervals between harvests. Because it can be developed from data that can be collected at a single time, the Beverton-Holt model provides a rational starting point for regulating new fisheries where long-term characterizations of population dynamics are rarely available. However, an adaptive approach to the fishery requires the incorporation of reproductive data.     

Water temperature affects life-cycle duration of tadpoles of Natal cascade frog

Direct and indirect effects of climate change on amphibians include range shifts and changes in community structure. The Natal cascade frog Hadromophryne natalensis has an altitudinal range of some 2 400 m in KwaZulu-Natal, and presents an opportunity to assess how increased water temperatures may impact on widely distributed amphibians. We sampled populations of tadpoles at three sites near the upper and lower altitudinal extremes of their range, measuring total length, mass and habitat water temperatures. Except for the spring survey, frequency–size class data showed bimodal curves at the two high-altitude sites and unimodal curves at the low-altitude site, suggesting a two-year aquatic life cycle in the cooler, higher rivers and a one-year life cycle at the warmer site. These data were consistent with cumulative degree days, which doubled from the higher- to the lower-altitude sites. Tadpoles at the warmer, lower-altitude site were in worse condition than those at the cooler, higher-altitude sites. We hypothesise that, while thermal changes may not result in rapid, large range shifts for this species, there are a number of unknown variables that may result from potential reductions in life-cycle length, including changes in competitive behaviour and community structure linked to asynchronies between species.     

Population structure and gene flow in a newly harvested gray wolf (<Emphasis Type="Italic">Canis lupus</Emphasis>) population

The genetic effects of harvest may be especially important in species that form social groups, such as gray wolves (Canis lupus). Though much research exists on the ecology and population dynamics of gray wolves, little research has focused on how anthropogenic harvest relates to the genetics of wolf populations. To analyze the short-term genetic consequences of the first two years of public wolf harvest in Minnesota following delisting under the Endangered Species Act, we genotyped harvested individuals at 18 microsatellite loci and quantified changes in population genetic structure and diversity in the first post-harvest year. If the harvest rate was high enough to create detectable genetic changes, population structure and differentiation between clusters could both increase because of decreased natal dispersal and increased disperser mortality, or they could decrease because of increased immigration from outside the population. In the Minnesota population, heterozygosity and allelic richness were not significantly different between years. However, population genetic structure increased and effective migration decreased among the sampled wolves. While the role of anthropogenic harvest in these changes cannot be distinguished from other confounding factors, this analysis suggests that harvest has a non-negligible effect and indicates the need for continued study to determine whether harvest-induced changes in genetic structure affect the evolutionary trajectory of harvested populations.     

Influences of riparian logging on plants and invertebrates in small,depressional wetlands of Georgia,U.S.A.

We studied 12 small, seasonally flooded, depressional wetlands on the Atlantic Coastal Plain of Georgia, U.S.A. Each wetland was embedded in stands of managed plantation pine. The pine trees surrounding each wetland had been harvested and replanted beginning in 1997 (2 sites), 1995 (2 sites), 1993 (1 site), 1988 (2 sites), 1984 (2 sites) or 1975 (3 sites). Regressions of various environmental variables with harvest histories indicated that those wetlands surrounded by smaller trees had greater light levels, water temperatures, pH, herbaceous plant cover and biomass, terrestrial invertebrate diversities and numbers, and water flea numbers, and lower water electrical conductivities and aquatic oligochaete numbers than those wetlands surrounded by more mature trees. Detected variations in hydroperiod, water depth, dissolved oxygen levels, sediment inputs, macrophyte diversity, periphyton biomass and densities of most aquatic invertebrates were not clearly correlated with past histories of peripheral tree harvest. This study suggests that harvesting trees around small wetlands initiates physical and ecological changes within the embedded habitats and that changes can persist for up to 15 years.     

Scales of spatiotemporal variation in macroinvertebrate assemblage structure in monsoonal streams: the importance of season

1. We assessed the relative importance of different scales of spatial and temporal variability on benthic macroinvertebrate assemblage structure in six unpolluted streams in monsoonal Hong Kong using ordination and complementary multivariate analyses. The spatial scales were regions, sites (streams) and sections (riffles) within sites. The temporal scales were years (three, including one with unusually high rainfall), seasons (dry versus wet) and days within seasons. 2. Significant differences in assemblage structure were manifested at all temporal scales. Those at the site scale were most obvious, whereas demarcation of assemblage structure at the section (riffle) scale was smaller, and there was no significant regional differentiation in assemblage structure. Seasonal variability in assemblage structure was greater than that among years or days. 3. Inter‐year differences in assemblage structure were recorded at all sites, and were noted among all years at some sites but not at others. They were recorded more frequently during the dry season, although their occurrence (in pair‐wise comparisons between years) appeared to be related to differences in the monsoonal (wet season) rainfall. 4. Seasonal differences in assemblage structure were strongly evident at all sites. Inter‐site differences were more apparent during the dry season when local (site‐scale) influences on assemblages were stronger. By contrast, wet‐season samples were more variable because of spate‐induced disturbance, and inter‐site differentiation was less distinct. 5. Differences among days at all sites were relatively minor, but shifts attributable to repeated spate‐induced disturbance were evident at some sites during the wet season. 6. Differences at the section scale were recorded more frequently during the dry season, when the extent of within‐site variability among sections was higher, reflecting increased patchiness within sections resulting from increased substratum heterogeneity and/or greater intensity of biotic interactions. 7. Seasonal shifts in macroinvertebrate assemblage structure at a variety of scales in Hong Kong streams are likely to be attributable to monsoonal rains affecting the relative intensity of abiotic disturbance and biotic interactions in accordance with the harsh‐benign hypothesis.     

Spectral analysis discerns pattern and feedback in natural‐ and anthropogenic‐disturbed boreal black spruce forests

The two major disturbance types of boreal black spruce forest in north–central Quebec, Canada – natural disturbance by wildfire and anthropogenic disturbance by harvest – may affect processes of recovery differently and leave distinct post‐disturbance soil and vegetation spatial patterns. We tested whether 1) spatial patterns of physico‐chemical soil organic layer properties, black spruce diameter and density, and understory ericaceous shrub cover, differ between these two principal disturbance types; 2) operations associated with forest harvest result in distinct, regular spatial patterns of these same variables related to presence of machine trails; and 3) ericaceous shrub presence is a potential factor contributing to the legacy of spatial patterns after harvest. We explored these patterns on black spruce‐feathermoss forest stands, including fire‐origin stands (18 and 98 years) and stands originating from harvest (16 and 62 years) in central Quebec, Canada. We used two spatial analysis methods, spectral analysis and principal component analysis in the frequency domain, to characterize and relate spatial patterns of these soil and vegetation variables, measured along 50‐m transects on each site. Spatial patterns of distribution of soil and vegetation variables were different on the burned and the harvested forest sites. Wildfire gave rise to spatial patterns in soil and vegetation variables at multiple scales, reflecting the complexity generated by variable burn intensity. Patterns following forest harvest were mainly related to the regular structure defined by trails created by logging operations. In contrast to burned sites, ericaceous shrub patterns on harvested sites were strongly associated with spatial arrangements of spruce diameter and density, promoting absence of canopy closure and persistence of trails. Moreover, different spatial signatures did not converge in the long‐term (62–98 years) between the two disturbance types. The divergence in spatial structure between natural and anthropogenic disturbances has implications for ecosystem structure and function in the longer term.     

Bimodal length frequency distribution in 0+aged masu salmon,Oncorhynchus masou,in a natural stream of southern Hokkaido

The frequency distribution of the fork length of 0⁺ aged masu salmon,Oncorhynchus masou, changed from unimodal to bimodal distribution in autumn of the years from 1982 to 1984 in the Mogusa River of southern Hokkaido, Japan. The bimodal distribution consists of two (upper and lower) modal groups. These two groups resulted from a difference in growth rate of 0⁺ aged individuals in autumn. Fish belonging to the upper modal group are assumed to be potential 1⁺ smolts. Whether 0⁺ aged parr transform into smolt or remain as parr in the following spring may be related to the growth rate of fish in the first autumn.     

Effects of secondary tuber harvest on populations of devil's claw (Harpagophytum procumbens) in the Kalahari savannas of South Africa

Devil's claw ( Harpagophytum procumbens ) is an internationally traded species that is harvested for its secondary tubers. Root extracts are used to treat arthritis and other inflammatory diseases. This study examined population structure, density, growth, mortality, and seed and fruit production in harvested and unharvested populations in the Kalahari savannas of South Africa over 4 years. Plant density and population structure differed significantly between overgrazed and grass-dominated areas, suggesting that the differences may be due to competition for water and nutrients. Experimental removal of secondary tubers (harvest) was not a significant factor for mortality in any of the harvested size classes. Harvest also did not affect growth, although plants in the 3–4 cm size class grew more in both the harvested and unharvested populations. Fruit production was variable; fruits matured only after sufficient rains. Under the conditions of this study, the species appears to be resilient to harvest, with both harvested and unharvested plants surviving. After harvest, both groups recovered and grew (on average) at the same rate. Because of the spatially variable habitat and the plasticity of the plants themselves, a large number of plants over a wide area are required to better understand the species' life history.     

Growing season carbon gas exchange from peatlands used as a source of vegetation donor material for restoration

The moss layer transfer technique removes the top layer of vegetation from donor sites as a method to transfer propagules and restore degraded or reclaimed peatlands. As this technique is new, little is known about the impacts of moss layer transfer on vegetation and carbon fluxes following harvest. We monitored growing season carbon dioxide (CO₂) and methane (CH₄) fluxes as well as plant communities at donor sites and neighbouring natural peatland sites in an ombrotrophic bog and minerotrophic fen in Alberta, Canada from which material was harvested between 1 and 6 years prior to the study. Plant recovery at all donor sites was rapid with an average of 72% total plant cover one growing season after harvest at the fen and an average of 87% total plant cover two growing seasons after harvest at the bog. Moss cover also returned, averaging 84% 6 years after harvest at the bog. The majority of natural peatlands in western Canada are treed and tree recruitment at the donor sites was limited. Methane emissions were higher from donor sites compared to natural sites due to the high water table and greater sedge cover. Carbon budgets suggested that the donor fen and bog sites released higher CO₂ and CH₄ over the growing season compared to adjacent natural sites. However, vegetation re-establishment on donor sites was rapid, and it is possible that these sites will return to their original carbon-cycle functioning after disturbance, suggesting that donor sites may recover naturally without implementing management strategies.     

Is hunting an effective tool to control overabundant deer? A test using an experimental approach

Overabundant populations of cervids have induced drastic negative effects on plant communities in several regions worldwide. Antlerless deer harvest by sport hunters has been proposed as a potential solution to overabundance because the philopatric behavior of female deer is expected to limit recolonization of hunted zones. The efficiency of this method, however, has rarely been tested in the wild. Using a large-scale experimental design, we reduced white-tailed deer (Odocoileus virginianus) density within 5 20-km² areas on Anticosti Island (Québec, Canada). Our objective was to harvest 50% of antlerless deer in each site during the first year of the study in 2002, and 30% from 2003 to 2006. We monitored deer density, vegetation abundance and growth as well as deer life-history traits during 6 years in these experimental sites and in 5 control sites where harvest rate was 5–7%. Overall, we achieved 93% of harvest objectives. Contrary to our expectations, however, deer density, vegetation abundance and growth, and deer life-history traits did not vary differently in experimental and control sites during the study period. They rather varied stochastically but synchronously. We discuss several alternative hypotheses that may explain these results, including 1) compensatory mechanisms, 2) biases in density estimates, 3) limited access to territory for hunters, 4) large target areas for localized management, 5) low hunter density, 6) recolonization by surrounding deer, 7) slow plant response under canopy cover, and 8) bottom-up mechanisms. Given the large efforts invested in this study, we conclude that the local control of abundant cervid populations through sport hunting may be difficult to achieve in many natural environments. © 2012 The Wildlife Society.     

Spatial and temporal changes in occupancy frequency distribution patterns of freshwater macrophytes in Finland

A useful method for characterizing biological numerous assemblages at regional scales is the species occupancy frequency distribution (SOFD). An SOFD shows the number or proportion of study sites each species occurred. Species that occur at only a few sites are termed satellite species, while species that occur at many sites are termed core species.This study is the first to document and assess SOFD patterns in aquatic macrophytes. It characterizes SOFD patterns of freshwater macrophyte assemblages in Finland at two spatial and two temporal scales. For this, I analyzed three published datasets on freshwater macrophyte distributions: two from studies conducted at a local scale and the third from large national surveys. One local study and the national study also included data on temporal variation in species occupancy frequencies.In the national study, the number of core and satellite species varied slightly between the older and the newer survey, respectively. Among the 113 waterbodies surveyed as part of the national study, the SOFD followed a unimodal satellite pattern. However, for the older dataset (from the 1930s), a bimodal symmetric pattern also fit the SOFD data well. At the local scale, I observed geographical variation in SOFD patterns. The dataset from southern Finland followed a unimodal satellite SOFD pattern; data from central Finland instead displayed a bimodal symmetric SOFD pattern, although they also fit equally well with a bimodal truncated pattern. Moreover, temporal patterns in central Finland seemed to demonstrate a shift from a bimodal symmetric to a bimodal asymmetric SOFD probably.Geographical variation in the SOFD pattern may be due to variation in the regional species pool. The temporal changes in SOFD pattern may be due to lake eutrophication and anthropogenic disturbance around waterbodies, which may increase number of macrophyte species.     

Recolonization and restoration of upper intertidal Fucus gardneri (Fucales,Phaeophyta) following the Exxon Valdez oil spill

The Exxon Valdez oil spill in March 1989 and subsequent cleanup caused injury to intertidal Fucus gardneri populations especially in the upper intertidal. A survey in 1994 in Prince William Sound, Alaska showed that the upper boundary of Fucus populations at oiled sites was still an average of 0.4 m lower than the upper boundary at unoiled sites.Restoration of severely damaged Fucus populations was started on a small-scale at a heavily oiled rocky site in Herring Bay, Prince William Sound. Experiments employed mats of biodegradable erosion control fabric to act as a substratum for Fucus germlings and to protect germlings from heat and desiccation stress. A series of plots was covered with mats made from a resilient coconut-fiber fabric in June 1993. Half of the mats were inoculated with Fucus zygotes. A series of uncovered control plots was also monitored. There was no enhancement of Fucus recruitment on the rock surfaces under the mats. Dense populations of Fucus developed on the surface of all of the mats by the summer of 1994. The natural rock surfaces in the control plots, both inoculated and not, were barren of macroscopic algal cover. By September 1994, the juvenile thalli on the mats were approximately 2 cm in length. Inoculating the mats had an effect only in the upper region of the intertidal. It is expected that the thalli will become fertile during the 1995 season. These thalli may serve as a source of embryos to enhance the recovery of new Fucus populations in this high intertidal area.     

Age structure: an indicator to monitor populations of large herbivores

Most populations of large herbivores are hunted over much of their distribution. The size of these populations over time must be monitored to detect responses to management actions and environmental changes. Here, I first review the limits in precision and accuracy of most methods used to estimate population size in wild herbivores. I then show how density-dependence of age structure can be used to monitor harvested populations, using simulated and empirical data. Accurate estimates of population size are difficult, costly in time and effort, and mostly impracticable at a large scale. Indices are widely used to monitor population size at a large scale, but are rarely tested, and assumptions of constant detection rates over years are questionable. In a recent approach, the effects of population density on habitat quality and individual performance were used as ecological indicators to infer changes in population size over time. Populations of large mammals are strongly age structured. In harvested populations, density-dependence and harvest affect age structure through changes in age-specific vital rates. Because age- and sex-specific vital rates are density-dependent, changes over time in age structure should reflect the response of population to changes in environmental conditions such as density and harvest rate. Time series of age-structure may be used as an ecological indicator to monitor harvested populations, and to infer their demographic trajectory, especially when used within a set of ecological indicators. However, attention needs to be paid in the use of ecological indicators because of the potential bias introduced in data collection by hunter selectivity.     

Growth and development of a bimodal length-frequency distribution during smoking in a wild population of white-spotted charr in northern Japan

Smolt age and size, and individual growth during smoking were examined in a wild population of white-spotted charr, Salvelinus leucomaenis , in a small stream in northern Japan. Smolt size (110–210 mm F.L.) differed neither between sexes nor among age cohorts of 2–7 years. Back-calculation of riverine growth of smolts using otoliths showed a gradually increasing discrepancy in fork lengths of these age cohorts in both males and females, the faster-growing individuals smolting at an earlier age. A mark—recapture study on individually-identified fish revealed that the initial (spring-summer) length-frequency distribution of parr was unimodal, but became slightly skewed to the larger side in autumn, resulting in a bimodal distribution being evident by the following spring, with the upper modal group primarily composed of smolts. However, closer examination revealed that both male and female potential (subsequent) smolts were larger than the potential parr in the previous spring, the minimum lengths of the former being around 90–100 mm f.l. Specific growth rates of the potential smolts remained relatively high after summer through to the following spring, whereas those of the potential parr decreased after summer, despite having been similar between the two groups during the previous spring and summer. These observations revealed that the developmental triggering of smelting possibly occurs in or following the summer season.     

Variation in frequency of hybrids and spatial structure among Ipomopsis (Polemoniaceae) contact sites

Rates of hybridization vary among angiosperm taxa. Among-taxon variation in hybridization rate has been used to compare the importance of pre- and post-zygotic reproductive isolating mechanisms. Variation in rates of hybridization within a single-species pair would suggest that local conditions also affect reproductive isolation within a single taxonomic context. In this study, contact sites of Ipomopsis aggregata-Ipomopsis tenuituba were surveyed for variation in frequency of hybrids, and spatial structure. Floral morphology was used to identify parent species and hybrids in seven contact sites in the western Rocky Mountains, USA. Contact sites varied widely in elevational range, the degree to which morphological variation was clinal rather than mosaic and the frequency of hybrids. Two sites provided a strong contrast between a clinal, unimodal site and a mosaic, bimodal site. This natural variation among contact sites of the same species pair provides an opportunity to assess the effect of local ecological conditions and spatial structure of parent populations on reproductive isolation, while controlling for between-taxon variation.     

Gelidium pristoides in South Africa

Gelidium pristoides has been harvested commercially from the eastern Cape, South Africa, since 1951, with 40–80 t y^–1 (dry wt) collected in recent years. This species has been intensively studied since 1983, and we briefly review knowledge of its biology in relation to harvesting. We describe a new study of intertidal epiphytic animals, showing that none is specific to G. pristoides, and that only 2.8% of these animals (numbers) inhabit this agarophyte, while the rest are found in other intertidal algal communities: harvesting is considered to have negligible effects on epifauna. Over the past 3 y, we have monitored, at two sites, the effects of the harvesting of G. pristoides on other benthic algae and animals. In only two of the seven main components analysed, did we find any difference between harvested and control plots. At one site only, the number of limpets and percentage cover of Gelidium was higher in harvested plots. These results show that harvesting has no significant biological effect. Regulations governing seaweed exploitation in South Africa were amended in 1988, to encourage local processing of products, and these changes are discussed in relation to the local Gelidium industry. Despite experimental results predicting a higher yield per unit effort if harvesting is limited to summer, harvesting continues throughout the year for practical reasons.     

Macroinvertebrate community response to natural and forest harvest gradients in western Oregon headwater streams

1. To examine the effects of forest harvest practices on headwater stream macroinvertebrates, we compiled a 167 site database with macroinvertebrate, fish, physical habitat and catchment land cover data from the three forested ecoregions in western Oregon. For our analysis, headwater streams were defined by catchment areas <10 km² and perennial water during summer low flows. Almost all sites in the database were selected using a randomised survey design, constituting a representative sample of headwater streams in these ecoregions. 2. Macroinvertebrate taxonomic and functional feeding group composition were very similar among the three ecoregions in the study area (Coast Range, Cascades and Klamath Mountains). On average, 55% of the individuals at each site were in the orders Ephemeroptera, Plecoptera or Trichoptera. Dipteran taxa (mostly chironomids) accounted for another 34%. At almost all sites, non‐insects made up <10% of the macroinvertebrate assemblage. Almost half (49%) of the assemblages were collectors; remaining individuals were about evenly divided among scrapers, shredders and predators. 3. There were 189 different macroinvertebrate taxa at the 167 sites with richness at individual sites ranging from 7 to 71 taxa. Ordination by non‐metric multidimensional scaling revealed a strong association between % Ephemeroptera, especially Baetis, and site scores along the first axis. This axis was also strongly related to % coarse substratum and fast water habitat. The second axis was strongly related to % intolerant individuals, site slope and altitude. No strong relationships were evident between any ordination axis and either logging activity, presence/absence of fish, catchment size or ecoregion. 4. Based on macroinvertebrate index of biotic integrity (IBI) scores, 62% of the sites had no impairment, 31% of the sites had slight impairment and only 6% of the sites had moderate or severe impairment. IBI scores were not strongly related to forest harvest history. All four severely impaired sites and five of the seven sites with moderate impairment were lower altitude, shallower slope stream reaches located in the Coast Range with evidence of agricultural activity in their catchment or riparian zone. % sand + fine substratum was the environmental variable most strongly related to macroinvertebrate IBI.