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Software is now available to apply a salmonid bioenergetic drift-foraging model to generate values of net energy intake (NEI) over a range of water depths and velocities. The predictions can be use...

This study advances understanding of the flow dependency of invertebrate drift in rivers and its relevance to drift-feeding fish. Background drift concentration varied spatially and with flow over natural flow recession (lower mid-range to low flow) in a reach of a New Zealand river, largely consistent with passive entrainment. Seven taxonomic groups (dominated by Leptophlebiidae and Chironomidae) exhibited positive drift concentration–flow relationships, and one (sandy/stony-cased caddisflies (Conoesucidae)) exhibited negative relationships. A mechanistic drift transport model accurately predicted the slope, but not y intercept, of the drift concentration–flow relationship for the total drift community that positively responded to flow but performed more poorly at the taxon or size-class level. Partitioning the relative influence of drift entry and dilution revealed that positive drift concentration–flow relationships arose from entry overwhelming dilution with increasing flow. Drift transport models have potential for predicting relative (%) effects of flow change on concentration and rate of drift-prone invertebrates. This paves the way for drift transport models to inform inputs to net rate of energy intake models for drift-feeding fish.

Understanding what drives variation in fish abundance at reference sites provides perspective for assessing the effects of human alterations to river flow and land use. We examined temporal variation in fish community abundance in a headwater tributary of a large river in the upper South Island (New Zealand) over 10 years. We were interested in the influence of natural flow variation and temperature on native fish abundance within the context of potential competition/predation pressure from juvenile introduced trout. Results from biannual sampling highlighted the dominating influence of floods on fish population dynamics, overriding biotic effects. We found no evidence for adverse effects of trout on native fish, and flow-related habitat performed more poorly in explaining variation in fish abundance than low- and median-flow statistics. Differences in temporal variation in abundance between species were largely consistent with life histories that provide resistance and (or) resilience to flood flows and relative insensitivity to low flows. Long-term data (≥10 years) are needed for detecting meaningful trends and quantifying the effects of human activities on fish community abundance.

Mechanically reshaping stream banks is a common practice to mitigate bank erosion in streams that have been extensively channelised and lowered for land drainage. A common perception regarding this activity is that fish populations will be largely unaffected, at least in the short term, because the low‐flow wetted channel remains undisturbed. However, the response of fish populations to this practice has rarely been quantitatively evaluated. Using a Before‐After‐Control‐Impact design, we assessed fish community responses to a catchment‐scale bank reshaping event in a fourth‐order low‐gradient stream that drains an intensive agricultural landscape. Quantitative electric fishing and fish habitat data were collected 2 months before and annually for 3 years after the reshaping event. After reshaping, deposited fine sediment levels increased in impact reaches, and there was a significant reduction in anguillid eel biomass (by 49%). In contrast, densities of obligate benthic gobiid bully species increased significantly in impact reaches—potentially due to reduced predation pressure from eels. Three years after bank reshaping, fish community structure had largely returned to its preimpact state in the reshaped areas. Our results suggest that, even in highly modified stream channels, further bank modification can reduce instream habitat quality and displace eels for at least 1 year. Managers should endeavour to use bank erosion control measures that conserve bank‐edge cover, especially in streams with populations of anguillid eels, because these fish are declining globally.

Using a space-for-time substitution design, we investigated the response of structural instream habitat and fish populations to different riparian management practices throughout a Dairy Best Practice Catchment. We found a significant negative correlation between the upstream area of stock exclusion fencing and deposited instream fine sediment cover. Furthermore, we determined that this relationship emerges when ≥300 m lengths of upstream riparian area were included in the analysis, indicating the scale at which stock exclusion fencing results in a positive instream habitat response. Specifically, for this historically degraded spring-fed stream, our findings indicate that riparian segments with 5 m wide stock exclusion fences (both banks) are required to achieve instream fine sediment cover below 20% in downstream reaches. Fish were sparse and evenly spread throughout the catchment. Fish distributions were not correlated with reach-scale riparian or instream habitat variables, possibly because th...

We compared a process-based invertebrate drift and drift-feeding net rate of energy intake (NREI) model and a traditional hydraulic-habitat model (using the RHYHABSIM [River Hydraulics and Habitat Simulation] software program) for predicting the flow requirements of 52-cm Brown Trout Salmo trutta in a New Zealand river. Brown Trout abundance predicted by the NREI model for the constant drift concentration–flow scenarios were asymptotic or linear, depending on drift concentration, increasing through the mean annual low flow (MALF; 17 m3/s). However, drift concentration increased with flow, consistent with passive entrainment. The predicted fish abundance–flow relationship based on flow-varying drift concentration increased logistically, and more steeply, with flow through the MALF and beyond. Predictions for the relationship between weighted useable area (WUA) and flow were made for three sets of drift-feeding habitat suitability criteria (HSC) developed on three midsized and one large New Zealand ...

We investigated changes in seasonal biomass of benthic macroinvertebrates over whole floodplain transects upstream and downstream of existing flow diversions in the Wilberforce and South Ashburton Rivers, Canterbury, New Zealand. We tested the predictive performance of a 1-dimensional hydraulic-habitat model informed with existing general habitat suitability curves (HSC), as well as river- and channel-specific HSC developed from the studied rivers. Diversions resulted in significant declines in wetted width, habitat complexity, and resulting declines in benthic biomass, but community composition was unchanged. Weighted usable area (WUA) predictions based on general HSC were often poorly correlated with cross-sectional macroinvertebrate biomass. River- and channel-type-specific HSC greatly improved the accuracy of predictions; however, all HSC generally under-predicted the total proportional change in cross-sectional macroinvertebrate biomass associated with flow change. We conclude that WUA was an insensi...

We investigated the potential of dual-frequency identification sonar (DIDSON) deployed from a drifting cataraft for estimating abundance in rivers of Brown Trout Salmo trutta larger than 20 cm. We compared triplicate trout density estimates made by DIDSON with drift-diving density estimates in three reaches of a clear-water river in New Zealand. DIDSON density estimates were much lower (∼22% of drift-dive estimates, range = 7–33%) and less precise than drift-dive estimates (DIDSON CV = 0.13–0.47; drift diving CV = 0.15–0.17). Variation in detecting fish in the DIDSON field survey contributed substantially more (95%) to DIDSON count variability than did fish detection in the image files. Highest precision with DIDSON was achieved in the reach with the least shallow habitat and most uniform channel. Fewer person-hours were required to undertake the field component of DIDSON surveys than the drift dives (5 versus 8.3 h), but the substantial time spent on image review (3.3 h) made DIDSON surveys 34% m...

We developed habitat suitability curves (HSC) using generalised additive models (GAMs) for nine benthic macroinvertebrate taxa from a small New Zealand river for hydraulic-habitat modelling assessments of instream flow requirements. We included interaction terms between the primary variables (water depth, velocity, substrate) when significant, to address a longstanding criticism of univariate HSC. To date, only large-river univariate HSC have been available and these have been used in hydraulic-habitat applications on small rivers, despite doubt over the transferability of HSC between rivers of different size and type. We tested the outcome on the predicted abundance–flow relationship of applying the small-river habitat suitability GAMs versus large-river GAMs for two taxa on the same small river. We found the effects of flow allocation were overestimated by the large-river GAMs relative to the small-river GAMs. Further research to develop general HSC for categories of river size and type is needed to bet...

We tested a model [Benthic Invertebrate Time series Habitat Simulation (BITHABSIM)] for simulating the effect of changes in flow on benthic macroinvertebrate habitat and relative abundance. The model calculates a habitat index (WUA2) based on weighted usable area (WUA) modified to account for reduction of invertebrate abundance by flood disturbance and drying followed by recolonization. The test involved a comparison of WUA and WUA2 with a 1-year abundance time series of the common New Zealand mayfly Deleatidium spp. in a small gravel-bed river with naturally variable flows. The fit of WUA and WUA2 to the Deleatidium spp. abundance time series was judged on correlation and regression analysis of the magnitudes and slopes of the mean-standardized indices and abundance versus time. WUA fit the low flow part of the abundance time series fairly well, but not the portion after flood disturbance. Over the entire time series, WUA fit Deleatidium spp. abundance and rate of change poorly. WUA2 fit Deleatidium abundance better, but the correlation was not quite statistically significant at the 95% level. However, it did explain the essential temporal pattern. The fit of the slopes of standardized WUA2 to the slopes of standardized Deleatidium spp. abundance was significant (R2 = 0.66), but with a systematic bias; high slopes were underestimated and low slopes overestimated. BITHABSIM adds biological realism to traditional hydraulic-habitat modelling based on WUA and so improves the reliability of assessments of effects of flow change on benthic macroinvertebrates over the entire hydrograph. Parameter uncertainty and research needs to improve BITHABSIM and future process-based models are discussed. Copyright © 2014 John Wiley & Sons, Ltd.

A dosimetry experiment used to measure the neutron flux and spectrum of a D-T neutron generator is presented. The D-T generator at Pacific Northwest National Laboratory is installed in the middle of a large room to minimize scatter of neutrons back to the sample. The efficacy of maintaining a pure fast neutron field for the sample is investigated. Twenty-one positions within 13 cm of the neutron source contained foils or wires of Fe, Ni, and Al with additional Au, and in monitors at some locations. Spectral adjustment of the neutron flux at each position based on the measured reaction rates and theoretical Monte Carlo calculations show that at least 99.1% of the spectrum lies above 110 keV for all measured positions, and neutrons above 14 MeV can account for as much as 91% at locations along the axis of the generator and close to the source. The 14 MeV component drops to 77% in radial positions far from the source. The largest total flux observed was 8.29E+08 n/cm 2 s (±1.4%) in the center of the cooling cap, although additional experiments have shown this value could be as high as 1.20E+09 n/cm 2 s.

In this paper we review drift-feeding models for stream salmonids. We assess their historical development and current state, and we propose areas for future research. Drift-feeding models serve as the critical input for energetics-based habitat selection and habitat quality models, which have recently begun to see widespread use for predicting salmonid distribution, growth and abundance. We use a bibliometric approach to find drift-feeding model publications, especially those citing three landmark papers that began the quantification of drift feeding by stream fish (Fausch 1984; Hughes and Dill 1990; Hill and Grossman 1993). Subsequent drift-feeding models have largely been built upon these models. Research effort has focused on model development and applications but model testing has been neglected. To date, the only rigorous test of a drift-feeding model (Hughes et al. 2003) identified several limitations and violations of model assumptions. The most important limitation was that prey capture- and gross energy intake rates were overestimated by a factor of two, due largely to poor predictions of prey detection probabilities. Consequences of error in drift-feeding models, and consequently in the habitat selection/quality models that employ them, are greater for applications aimed at predicting growth and abundance than they are for predicting distribution. Research effort on a broad front is needed to advance both drift-feeding models and habitat selection/quality models, including: further development of drift-foraging theory, revision and testing of drift-feeding models (specifically new, functional prey detection and interception sub-models), and revision of habitat selection/quality models to incorporate spatial, temporal, and flow-dependent variation in drift concentration.

We investigated juvenile brown trout migration and mortality in a headwater tributary of the Motueka River, New Zealand, by tracking 1000 young-of-the-year passive integrated transponder (PIT) tagged fish over autumn to summer to (i) partition total loss into emigration and mortality and (ii) determine the influence of season and flow on emigration. Fish were tracked using mobile and fixed PIT tag readers. Of the 1000 fish tagged, 173 remained within the Rainy River; emigration contributed 60% and mortality 29% to loss. Only 11% of fish tagged in autumn were predicted to remain in the upper reaches of the stream by early summer, and this agreed with density data collected in a parallel study. We identified a two-phase downstream migration pattern with early movement of large young-of-the-year fish in autumn (mainly during floods). This was followed by another substantial period of movement in spring (during floods and lower flows) by fish that were initially smaller at the time of PIT tagging. The management implications for damming and fish screening in headwater tributaries are discussed.

We describe and demonstrate a model (Benthic Invertebrate Time Series Habitat Simulation) for calculating the effect of changes to flow regimes on benthic invertebrate habitat and population dynamics. The following inputs are required: a hydrograph (discharge time series), habitat–discharge relationship, disturbance–discharge relationship, wetted width–discharge relationship and a recolonization time series. Habitat–discharge, disturbance–discharge and wetted width–discharge relationships are common outputs from instream hydraulic habitat models (e.g. Physical Habitat Simulation, River Hydraulic Habitat Simulation and River2D). Hydraulic habitat models calculate a combined habitat suitability index from physical habitat suitability curves for water depth, velocity and substrate composition and weight this by area to give a weighted usable area (WUA). Because conventional invertebrate habitat suitability curves are based on density estimates, the combined habitat suitability index can be treated as an index of density and WUA treated as an index of potential relative abundance (at the reach scale) in the absence of disturbance due to flow variation (flooding and drying) and biotic processes. Our approach begins with WUA and calculates realizable suitable habitat (i.e. relative abundance) by taking into account the resetting of benthic invertebrate densities by floods and drying and recovery (or accrual) rates and times. The approach is intended mainly to compare the relative amounts of productive invertebrate habitat sustained by natural and modified flow regimes, but it also has the potential for investigating the influence of flow variation on invertebrate population dynamics. We anticipate that the model will be particularly useful for assessing effects of changes in flow regimes caused by diversions, abstractions or water storage on annual benthic invertebrate productivity. Copyright © 2013 John Wiley & Sons, Ltd.

“Imagine a fish feeding in swift water.” With this statement in their landmark foraging model paper, Nicholas Hughes asked the reader to visualize how a driftforaging fish captures its prey (Hughes and Dill 1990). It is a simple, elegant statement, but it captures the essence of stream fish ecology. A stream is defined, after all, as flowing water. Its inhabitants are the product of millennia of adaptations to the unique selective pressures created by this dynamic environment. Imagination is the key for many of us who have studied fish feeding in swift water. It was perhaps Nick’s greatest gift to us. Foraging adaptations, in fact, have for many years led community ecologists to categorize stream fishes by their foraging guilds (e.g. Schlosser 1982). Clearly, stream fish fitness is largely determined by their ability to forage effectively in flowing water. Like all animals, the life histories of stream fishes have been finely tuned by natural selection to capitalize on spatial and temporal availability of prey resources. This truth is so transparent that it is surprising to realize just how under-appreciated it has become in stream fish ecology and management. A survey of the stream fish literature shows howmuch attention is paid to quantifying where fish make their living, versus how little attention is paid to quantifying how they do so. The study of physical habitat in streams has become a sub-discipline of its own, whereas the study of drift foraging has until very recently remained mostly in the realm of ecological theory. Were this a simple academic question it might not be so critical to bring this issue forward. But stream fish management, with its multitude of social and economic implications, has yet to come to grips with the fact that the distribution, growth, and abundance of fish probably depend as much (or more) on food as on space (Chapman 1966). Evolutionary theory, in fact, says as much. Darwin himself suggested that species are shaped more by interactions among themselves (e.g. predators and their prey) than they are by interacting with the physical environment. Animals must acquire resources to grow and reproduce, and those that are most successful enjoy the highest fitness. Thus, restoring natural flow regimes (e.g. Poff et al. 1997) to maintain fish habitat is only half the battle. Without a better mechanistic understanding of how food and space influence fish distribution, growth and abundance, we lack the tools to predict the outcome of habitat change, be it degradation or restoration. We still need an answer to the question that Nicholas posed in the opening lines of Hughes and Dill (1990)

The effects of natural flow variation on juvenile brown trout population dynamics were investigated by biannual sampling over 5.5 years in the Rainy River, a tributary of the Motueka River. A large flood in late March (50-year return period) substantially reduced the density (by 66%) and biomass (by 73%) of 0+ trout over autumn–spring, but the cohort responded with compensatory survival to achieve similar density and biomass by spring as in other years. A low-flow event in February–April (return period >8.4 years), when 7-day low flows fell to 56% of the 7-day mean annual low flow (MALF) and were less than the MALF for 46 days, had no adverse affect on the population. We found no evidence for density-dependent growth. However, there was strong evidence for a two-phase self-thinning response in density, with no self-thinning occurring over summer (i.e. the 0+ population remained below carrying capacity) until a threshold mass of 22.08 g (length=123.7 mm) was attained in autumn after which severe s...

Management of the effects of water quality and flow on fisheries requires an understanding of the factors that control fish movements. We used radiotelemetry to monitor the movements of adult brown trout Salmo trutta in a New Zealand river over 11 months (September 2004 to August 2006) and linked those movements to the changes in flow and water temperature. Individual fish moved up to 41 km during the study. However, most fish moved less than 1 km. All of the trout that showed little movement throughout the summer were living in relatively deep pools that presumably provided cover. The rates of movement declined steadily over the spring–summer period, as flow decreased and water temperature increased. The percentage of fish moving was positively related to the average daily flow during the interval between tracking occasions and negatively related to the average daily water temperature, less than 20% of the tagged fish moving once temperatures were above 19°C. A severe, 50-year flood occurred in ...

We present an overview of a process-based modelling approach for predicting how change in flow affects drift density, net rate of energy intake (NREI) and numbers of drift-feeding salmonids. It involves linking an existing two-dimensional flow model (River2D) with models of invertebrate drift transport and drift-foraging which we have developed. We describe, demonstrate and partially test our models in an application on a 80 m × 20 m pool on a New Zealand river. We show how these models realistically capture hydraulic, drift dispersion and bioenergetics drift-foraging processes to predict the relationship between stream flow, habitat quality and quantity (in terms of NREI), and carrying capacity for drift-feeding salmonids. Overall, the 2D hydraulic model made good predictions of water levels, depths and water velocity at the calibration flow and a lower (validation) flow. The drift transport model made good predictions of the spatial distribution of invertebrate drift density throughout the pool at low flow after it was calibrated against observed drift density at the higher flow. The model correctly predicted that drift density would decline downstream and into the margins due to the process of settling dominating over entry from the stream bed, and that drift would be carried further downstream and laterally as flow increased. The foraging model made a reasonable prediction (6–7) of the numbers of 0.5 m adult brown trout observed (5) in the pool. It accurately predicted that trout should be distributed down the thalweg where net rate of energy intake (NREI) was highest, but when NREI was adjusted for depletion by feeding fish the predicted drift-feeding locations were more closely spaced (bunched) than observed fish locations. Our process-based modelling approach has important implications for improving biological realism in predictions of the response of drift-feeding fishes to flow change within the context of the IFIM.

Angling pressure is increasing in many recreational trout fisheries throughout the world. There is a strong perception among anglers that trout become harder to catch after being disturbed by other anglers, thus affecting the quality of their angling experience. However, there is little scientific evidence to support or refute this perception. We measured the response to angling pressure in two rivers in New Zealand: The remote Ugly River and the more heavily fished Owen River. Both of these rivers have fisheries for brown trout Salmo trutta. The numbers of trout seen and caught over the length of four 3-d angling trips were compared between rivers. The behavioral responses to angling of naive trout in the Ugly River were compared with those of Owen River trout and trout that had been angled previously from the Ugly River. The proportion of the trout population in the study reaches caught by two anglers after four 3-d trips was estimated as between 11% and 23% in the Owen River and up to 47% in t...

We tested the assumptions and predictions of a foraging model for drift-feeding fish. We used three-dimensional videography to describe the foraging behavior of brown trout, Salmo trutta, mapped water depth and velocity in their foraging area, sampled invertebrate drift to determine length class specific drift densities, and captured trout to determine the size composition of their diet. The model overestimated the fish's prey capture rate and gross energy intake rate by a factor of two. Most of this error resulted from the fact that prey detection probabilities within the fish's foraging area averaged only half the expected value. This was the result of a rapid decrease in capture probability with increasing lateral distance from the fish's focal point. Some of the model's assumptions were accurate: equations for predicting reaction distance and minimum prey size supported reliable predictions of the shape and size of the fish's foraging area and the size composition of the diet. Other assumptions were incorrect: fish detected prey within the predicted reaction volume, not on its upstream surface as expected, fish intercepted prey more slowly than the expected maximum sustainable swimming speed, and fish captured about two-thirds of their prey downstream of their focal point, rather than upstream.

We assessed whether taxonomic structure and density of aquatic drift could be predicted from the benthos in three New Zealand rivers. The three main orders contributing to both the benthos and drift were Ephemeroptera, Diptera, and Trichoptera. Drift and benthic densities for all taxa and all rivers combined were not significantly correlated (adults inclusive and exclusive). There were significant positive correlations between benthic and drift densities for the three main drifting orders—Ephemeroptera, Diptera, and Trichoptera when data from all rivers were combined. However, these relationships were not always detected in individual rivers. The propensity for Deleatidium to drift was negatively related to chlorophyll a concentration; suggesting density‐dependent drift mediated by food limitation. Drift was reduced when periphyton chlorophyll a concentration was high in relation to benthic Deleatidium density. This highlights an unexpected effect of periphyton proliferation on invertebrate drift...

We investigated temporal (day‐to‐day and season) and spatial (reach) variability of drift with the aim of guiding sampling protocol for quantifying drift at the whole river or reach scale. Overall, we found aquatic drift density and biomass varied considerably seasonally (CV = 72.9, 88.1) and to a lesser extent spatially (CV = 31.3, 30.7) and from day‐to‐day (CV = 45.2, 39.4). Although spatial and day‐to‐day variation in drift density and biomass were similar, sampling logistics suggest spatial sampling would be more cost‐effective and less time consuming. Drift density and biomass estimated from top samplers was often higher than estimates from samplers near the streambed or mid‐water column. A reliable estimate of mean densities and biomass at a site may require only two samplers— a top sampler and either a middle or bottom sampler. In our study, we calculated that sampling at four sites over 1 or 4 days at one site would be required to obtain a 95% CI within 50% of the mean drift density. Eigh...

Here is presented, along with a revised overall site-plan indicating findspots, the late material from the BSA excavations in the northern cemetery area of ancient Knossos, prior to the construction of the present University buildings. These finds were excluded from the major published site-reports. They relate to the Early Christian martyrion-church complex noted in the preliminary site report. Dating from the period c. AD 400–650, they comprise some small deposits within the church complex, items placed in some of the many ossuaries (osteothekai) surrounding it, and in particular a well/cistern filling datable to c. 620–640 which may signal the end of use of the church (though perhaps not of the cemetery). The ossuary finds document a widespread sixth and seventh century burial custom—did the practice of depositing pots in funerary contexts then cease, due to religious censure? The well finds include the normal ‘export’ wares of the period, along with a class of Cretan(?) imitations of the African and Phocaean fine wares. Some wheelmade lamps have parallels from elsewhere in Crete; a class of very simple coarse bowls could be locally made. Several vessels bear graffiti, in particular a Phocaean Red Slip dish with two Christian dedicatory texts.

We compared raw drift‐dive counts of adult brown trout (Salmo trutta Linnaeus 1758) with population estimates calculated from mark‐resight techniques on two occasions in two back‐country rivers near Nelson, New Zealand. Trout were caught by angling and marked with colour‐coded dart tags between 1 and 7 days before drift dives were carried out. Drift‐dive counts in the Owen and Ugly Rivers were 57–66% and 21–43%, respectively, of the population estimates calculated using the mark‐resight techniques. Although underwater census is the cheapest and easiest way to census adult trout populations in clear‐water rivers, a large proportion of the trout population may not be seen in rivers with abundant in‐stream cover. Raw drift‐dive counts provide an index of relative abundance that is useful for monitoring changes in trout populations of specific river reaches over time. However, for comparisons between rivers more accurate population estimates are required. We recommend a combined approach of raw drift...

The post‐spawning movements and distribution of 15 brown trout (Salmo trutta Linnaeus 1758) and 21 rainbow trout (Oncorhynchus mykiss Richardson, 1836) were monitored weekly between August 1996 and March 1997 in the hydro‐electric reservoir, Lake Otamangakau, New Zealand, using radio‐telemetry. The most frequently used areas were the vicinity of the main inflow and the channel running through the main body of the lake. After spawning, brown trout regained rapidly their usual habitat. Rainbow trout were using the inlet intensively before recolonising the main channel of the lake. Brown trout made greater use of the weedy parts of the lake and littoral margins, had a more confined home range, and were less mobile than rainbow trout. Rainbow trout occupied the main body of the lake by day, and moved nearer the surface, and closer to the margins, at night. High lake levels allowed brown trout to exploit wetland margins of the lake.

We developed and tested a combined foraging and bioenergetics model for predicting growth over the lifetime of drift-feeding brown trout. The foraging component estimates gross energy intake within a fish- and prey size-dependent semicircular foraging area that is perpendicular to the flow, with options for fish feeding across velocity differentials. The bioenergetics component predicts how energy is allocated to growth, reproduction, foraging costs, and basal metabolism. The model can reveal the degree to which growth is limited by the density and size structure of invertebrate drift within the physiological constraints set by water temperature. We tested the model by predicting growth based on water temperature and on drift density and size structure data from postemergence to age 12, and we compared the predictions with observed size at age as determined from otoliths and scales for a New Zealand river brown trout population. The model produced realistically shaped growth curves in relation to...

SUMMARY 1. The impact of agricultural activities on waterways is a global issue, but the magnitude of the problem is often not clearly recognized by landowners, and land and water management agencies. 2. The Pomahaka River in southern New Zealand represents a typical lowland catchment with a long history of agricultural development. Fifteen sites were sampled along a 119-km stretch of the river. Headwater sites were surrounded by low-intensity sheep farming, with high-intensity pasture and dairying occurring in the mid-reach and lower reaches. 3. Water clarity decreased significantly from about 6 m in the headwaters to less than 2 m in the lower reaches. Benthic sediment levels increased significantly downriver, peaking at 35 mg mT 2 below several tributaries with high-intensity agriculture in their catchments. Periphyton levels were also significantly greater in the lower reaches than the headwaters, and coincided with increased nitrogen (DIN) and phosphorus (SRP) concentrations. 4. Macro-invertebrate species richness did not change significantly throughout the river, but species composition did with Ephemeroptera, and to a lesser extent, Plecoptera and Trichoptera dominating the headwater sites (where there was high water clarity, and low nutrient and periphyton levels). Downriver these assemblages were replaced by molluscs, oligochaetes and chironomids. 5. Canonical correspondence analysis indicated that agricultural intensity and physical conditions associated with agriculture activity (e.g. impacted waters, high turbidity and temperature) were strongly associated with the composition of benthic assemblages at differing reaches down the Pomahaka River. 6. The present results indicate that quantifying agricultural intensity within a catchment, particularly relative livestock densities, may provide a useful tool for identifying threshold levels above which river health declines.

New Zealand landscapes were extensively modified after European settlement in the late 1800s. Large areas of native forest were converted to pasture and few large areas of unmodified forest remain. Trout (Salmo trutta and Oncorhynchus mykiss) were introduced into the rivers at the same time, and these two changes are thought to have affected native fish communities. Kahurangi National Park is a large area of unmodified native forest with few introduced trout in smaller rivers draining to the west. A survey of these streams was made to determine whether their communities differed from those in other areas of New Zealand. No non‐diadromous native fish were found, suggesting a biogeographic separation from adjacent eastern and southern areas since the Pliocene or early Pleistocene. Contrary to popular expectation, fish diversity and abundance was often lower than at equivalent elevations in other areas of New Zealand. Lowland fish communities comprised a small stream community dominated by inanga (G...

Pacific Northwest National Laboratory (PNNL) has been tasked with evaluating the effectiveness of ORNL’s new hybrid transport code, ADVANTG, on scenarios of interest to our NA-22 sponsor, specifically of detection of diversion of special nuclear material (SNM). PNNL staff have determined that acquisition and installation of ADVANTG was relatively straightforward for a code in its phase of development, but probably not yet sufficient for mass distribution to the general user. PNNL staff also determined that with little effort, ADVANTG generated weight windows that typically worked for the problems and generated results consistent with MCNP. With slightly greater effort of choosing a finer mesh around detectors or sample reaction tally regions, the figure of merit (FOM) could be further improved in most cases. This does take some limited knowledge of deterministic transport methods. The FOM could also be increased by limiting the energy range for a tally to the energy region of greatest interest. It was then found that an MCNP run with the full energy range for the tally showed improved statistics in the region used for the ADVANTG run. The specific case of interest chosen by the sponsor is the CIPN project from Las Alamos National Laboratory (LANL), whichmore » is an active interrogation, non-destructive assay (NDA) technique to quantify the fissile content in a spent fuel assembly and is also sensitive to cases of material diversion. Unfortunately, weight windows for the CIPN problem cannot currently be properly generated with ADVANTG due to inadequate accommodations for source definition. ADVANTG requires that a fixed neutron source be defined within the problem and cannot account for neutron multiplication. As such, it is rendered useless in active interrogation scenarios. It is also interesting to note that this is a difficult problem to solve and that the automated weight windows generator in MCNP actually slowed down the problem. Therefore, PNNL had determined that there is not an effective tool available for speeding up MCNP for problems such as the CIPN scenario. With regard to the Benchmark scenarios, ADVANTG performed very well for most of the difficult, long-running, standard radiation detection scenarios. Specifically, run time speedups were observed for spatially large scenarios, or those having significant shielding or scattering geometries. ADVANTG performed on par with existing codes for moderate sized scenarios, or those with little to moderate shielding, or multiple paths to the detectors. ADVANTG ran slower than MCNP for very simply, spatially small cases with little to no shielding that run very quickly anyway. Lastly, ADVANTG could not solve problems that did not consist of fixed source to detector geometries. For example, it could not solve scenarios with multiple detectors or secondary particles, such as active interrogation, neutron induced gamma, or fission neutrons.« less

Otolith daily growth increment patterns were used to discriminate between early life‐history patterns of 0+ rainbow trout and to determine the contribution of each to adult recruitment. Inlet stream residents had narrow increments (2.13–3.18 μm) and Outlet Creek residents generally had wide increments (3.63–4.26 μm) across the entire otolith radius. The dominant otolith growth pattern in lake juveniles comprised narrow increments before emergence (3.23–3.66 μm) with wide increments (4.34 μm) soon after emergence. This “early lake migrant” pattern was consistent with incubation in cool inlet streams followed by emigration to the warmer lake upon emergence. Discriminant function analysis (DFA) using mean increment widths at 50, 150, and 200 |im from the primordia discriminated between these patterns (78% overall classification success; 96.5% for inlet stream residents, 60.0% for Outlet Creek residents, 77.0% for early lake migrants). Estimated proportions (from DFA) of the early life‐history types ...

Spatial and temporal variation in relative density of 0+ and 1+ brown trout was examined over three summers in the Kakanui River, North Otago, New Zealand. Both 0+ and 1+ trout were distributed throughout the river. Spatial variation in relative density was much higher than annual variation. Within years, relative density of 0+ brown trout varied by 5 to 92 times between sites (mean coefficient of variation, CV = 1.08) and of 1+ trout by 18 to 84 times between sites (CV = 1.13). Mean relative density of 0+ brown trout varied by 1.5 to 2.0 times between years (CV = 0.35) and of 1+ trout by 3.6 to 23.2 times between years (CV = 0.96). The pattern of 0+ trout spatial distribution was not closely related to the distribution of redds (which also were distributed throughout the river) and not related to the distribution of benthic invertebrate food. By their second summer, most trout occupied the middle and lower reaches of the river. Mean length of both 0+ and 1+ trout increased with distance downstre...

Summary The Multi-Isotope Process (MIP) Monitor represents a potentially new and efficient approach to monitoring process conditions in reprocessing facilities with the high-level goal of aiding in the “...(minimization of) the risks of nuclear proliferation and terrorism” (Office of Technology Assessment 1995). This approach relies on multivariate analysis and gamma spectroscopy of spent fuel product and waste streams to automatically and simultaneously monitor a variety of process conditions (e.g., acid concentrations, burnup, cooling time, etc.) in near real-time (NRT). While the conceptual basis for the MIP Monitor has been shown to be effective in an aqueous reprocessing system, the fundamental approach should also be viable in a pyro-processing recycle system. The MIP Monitor may be calibrated to provide online quantitative information about process variables for process control or domestic safeguards applications; or it can simply monitor, with a built-in information barrier, for off-normal conditions in process streams, making the approach well-suited for applications were it is necessary to respect proprietary information or for international safeguards applications. Proof-of-concept simulations and experiments were performed in previous years demonstrating the validity of this tool in a laboratory setting. This report details follow-on research and development efforts sponsored by the U.S. Department of Energymore » Fuel Cycle Research and Development (FCR&D) related to the MIP Monitor for fiscal year 2011 (FY11).« less

Underwater census and single‐pass electrofishing were compared for estimating relative abundance of juvenile brown trout in the Kakanui River, South Island, NZ. Mean sampling efficiency was lower, and the variability of sampling efficiency was much greater, for underwater census (0+ trout: x = 0.38, s = 0.368; 1+ trout: x = 0.62, s = 0.822) than for single‐pass electrofishing (0+ trout: x = 0.61, s = 0.143; 1+ trout: x = 0.74, s = 0.171). Sampling efficiency of both methods was dependent on temperature. Electrofishing became less efficient at higher temperatures whereas underwater census became less efficient at colder temperatures. The low, and highly variable, sampling efficiency for underwater census of 0+ brown trout was related to substrate hiding behaviour which is dependent on temperature. A ratio method for comparing relative abundance estimates is presented. Minimum significance values for the ratio (R) were derived for 0+ trout using temperature adjusted sampling efficiencies. To be sta...

We compared the fish communities of two shallow lakes in the lower Waikato River basin, North Island, New Zealand, to determine the effects of elevated suspended solids (SS) and collapse of submerged macrophytes. Lake Waahi was turbid (20–40 g m-3 SS) and devoid of submerged macrophytes whereas Lake Whangape was clearer (5 g m-3 SS) and dominated by submerged macrophytes. The lakes had similar fish species richness and had nine major species in common; representing eight families including Anguillidae, Retropinnidae, Galaxiidae, Eleotridae, Mugilidae, Ictaluridae, Poeciliidae, and Cyprinidae (two species). The only major fish that was absent from Lake Waahi was a lacustrine form of the common smelt, Retropinna retropinna, which disappeared after the lake became turbid in the late 1970s. CPUE, condition, and size of most species in Lake Waahi were similar to, or greater than, those in Lake Whangape. Lake Whangape clearly exceeded Lake Waahi only for CPUE of two species. Within Lake Whangape two species displayed significantly greater condition, and one species greater size, in a turbid arm of the lake than in the main basin. Apart from lacustrine Retropinna retropinna, the fish in these lakes appear well adapted to cope with, or to avoid, the direct toxic effects of suspended and settleable solids on sensitive early developmental stages. In Lake Waahi loss of cover and food provided by submerged macrophytes appears to have been compensated for by increased turbidity and an associated increase in the biomass of the mysid, Tenagomysis chiltoni (a major prey item).

Stomach contents of Gobiomorphus cotidianus,Retropinna retropinna, Gambusia affinis, and Anguilla australis were compared between two shallow lakes in the lower Waikato River basin, to examine the relationship between turbidity and diet. Lake Waahi and the south arm of Lake Whangape had been turbid (20–40 g suspended solids (SS) m−3) and devoid of submerged macrophytes since the late 1970s and early 1980s, respectively. The main basin of Lake Whangape had been generally clearer (5 g SS m−3) with dense beds of submerged macrophytes, but at the time of sampling (1987) water clarity had deteriorated (> c. 10 g SS m3) and submerged macrophytes had declined. The mysid Tenagomysis chiltoni was an important prey for all species of fish from turbid water bodies but was less important in stomachs of fish in the main basin of Lake Whangape. Apparently, mysids were not an important prey in Lake Waahi before it became turbid. Chironomid larvae and pupae dominated the diets of small fish in the main basin of ...

Growth rates of shortfinned eels (Anguilla australis) from various locations in the Waikato basin, New Zealand, were determined by otolith examination. Two colour‐morphs from the Whangamarino Swamp exhibited different growth rates. Dark‐coloured eels (96% of the catch in low water levels) resided in the swamp; their growth was much slower than that of light‐coloured eels (40% of the catch in floods) which probably entered this habitat in flood waters from Lake Waikare, the Whangamarino River, or main wetland channels. Overall, growth rates were fastest in Lake Waikare followed by Lake Waahi, Lake Whangape, and Hakarimata pastoral streams. Dark‐coloured swamp eels were the slowest growing. Relative annual length increments ranged between 10 and 47 mm. Fast growth of eels in Lake Waikare may be the result of low densities owing to poor recruitment and heavy fishing pressure in recent years. Estimated age at threshold commercial size varied by 11 years throughout the Waikato.

This case demonstrates the efficacy of prazosin in treating civilian post traumatic stress disorder (PTSD)-related nightmares. Although its mechanism is not fully elucidated, it is clear that prazosin decreases nightmares. Tolerability may limit one's ability to titrate to an effective dose.

Large koaro (Galaxias brevipinnis) were observed drift‐feeding in the water column and from the surface in a pool in Cave Brook, a tributary of Big River draining the Gouland Downs, Kahurangi National Park: an area free of introduced trout. This contrasts with the common perception of koaro habitat being cascades and fast, boulder riffles. It is suggested that sampling limitations of electrofishing may have given a misleading impression of the habitats occupied by this species in the past, and this may have been exacerbated by the presence of trout. The drift‐feeding behaviour and pool habitat use exhibited by koaro is similar to that of introduced trout. Where trout have invaded koaro habitat, predation and competitive displacement of koaro by trout seems likely.

Applications of planar integrated optical waveguide (IOW) technology to problems in surface spectroscopy and optical chemical sensing have been partly limited by the difficulty of producing high-quality glass IOWs. The fabrication of IOWs by the sol-gel method from methyltriethoxysilane and titanium tetrabutoxide precursors is described here. The physical, chemical, and optical properties of the films during and after high-temperature annealing were studied using a variety of analytical techniques. The results show that the catalyst used to accelerate the sol-gel reaction strongly influenced the optical quality of the IOW. HCl catalysis produced waveguides with propagation losses of approximately 1 dB/cm, whereas in the case of SiCl4 catalysis, propagation losses were < 0.2 dB/cm, a value significantly less than any previously reported for sol-gel-derived IOWs. An examination of film surface structure and morphology by scanning electron microscopy and atomic force microscopy showed that the SiCl4-catalyzed IOWs were significantly smoother and more homogeneous on a submicrometer scale than the HCl-catalyzed IOWs. The use of SiCl4 is thought to retard formation of a microheterogeneous network containing Si-rich and Ti-rich domains, which is favored with HCl catalysis and contributes to the higher observed losses.