Controls on spatial and temporal variations in sand delivery to salmonid spawning riffles

Fine sediment infiltration into gravel interstices is known to be detrimental to incubating salmonid embryos. Infiltration into spawning riffles can show large spatial variations at the scale of a morphological unit and over time, with significant implications for embryo survival. Furthermore, some process-based infiltration studies, and incubation-to-emergence models assume that fines are delivered to redds via suspension rather than bedload. This process-based 12-month study examined spatial patterns of predominantly sand infiltration into gravels in an upland trout stream, using infiltration baskets. An assessment of Rouse numbers for infiltrated sand indicated that it was transported predominantly as bedload at flow peaks. Clear temporal and spatial patterns existed, with highest rates of infiltration strongly associated with higher discharges (r2 = 0.7, p < .05). Seasonal variations in the delivery of different grain sizes were also a feature, with enhanced contributions of 0.5–2 mm sediment during elevated winter flows and 0.125–0.5 mm sediment during spring and summer; the latter is potentially harmful to the later stages of embryo incubation. Clear spatial patterns were also evident across riffles, with highest rates of infiltration tending to occur in areas of lower relative roughness—the areas competent to transport sand for longer periods. Incubation-to-emergence models should take into consideration spatial patterns of fine sediment dynamics at the pool–riffle scale, to improve prediction

Assessment of salmon spawning gravel in the River Frome, Gloucestershire

Three gravel freeze cores were extracted from each of three sites, identified as potentially suitable for salmon (Salmo salar, L.) spawning, on the River Frome. A quantitative assessment of the capacity of these gravel beds to support effective spawning was made based on the composition of the sampled substrata. Examined sediment size ranges included: optimum spawning gravel (16 > D > 64 mm), fine sediment (D D ≥ 1 mm) and clay (D < 4 µm). A threshold limit of 14% of sediment D <1 mm was used. Results indicated that optimum spawning gravel occurred at all sites in varying amounts. The distribution of these, however, were within the smaller size range suitable for spawning. Moreover, significant deposits of sediment D <1 mm limit potential spawning quality at all sites. The overall composition of substrata at Button Mill offers the best potential spawning habitat of the identified sites

Assessment of Past and Present Sediment Quality of Stoney Creek in Burnaby, British Columbia

In analyzing the sediment and water quality of the Stoney Creek habitat, four key aspects were investigated: lithology, sediment/water quality, salmon spawning/incubation, and particle size distribution. The lithology found the streambed sediment layer is 3 cm in depth (over bedrock) and consists mainly of sand and some coarser material including gravels, cobbles, and boulders. The sediment of the offchannel pond is mainly mud (fine material) with a moderate amount of sand and a very small percentage of coarser material including gravels and organic matter (leaf detritus and woody debris). Chemical analysis concluded a significant concentration of iron in the pond environment, with potential for adverse effects to salmon offspring. This report further aims to assess the influences of fine sediment on the quality of salmon spawning habitat and incubation success rate. Permeability of spawning gravels and dissolved oxygen concentrations are measured to see if they support the incubation and growth of salmon eggs. Particle size distributions are found significantly different between upstream pool and pond side. And the difference of particle size distributions can influence salmon production in the off-channel site

Conservation of barbel (Barbus barbus) in the River Great Ouse

There have been growing fears relating to the distribution and a perceived lack in natural recruitment of barbel in European rivers. This project reviewed existing literature, examined the suitability of Environment Agency data to assess barbel populations and designed investigations to identify possible bottlenecks in recruitment focusing on all life history stages and environmental influences, with the intention of developing a practical management plan for the River Great Ouse fishery that can be applied to other rivers.This study examined seasonal movements of 20 wild barbel via radio telemetry in a nine kilometre river stretch on the upper Great Ouse, recording weekly movements over an 18 month period. The project aimed to ascertain the effects of environmental influences on movement and habitat use. Radio tracking over 100 consecutive days throughout the spring periods in 2010 and 2011 gave an understanding of their daily movements, identified barriers limiting longitudinal movements and located active spawning gravels. Health of spawning gravels was assessed by monitoring changes in diatom growth and hyporheic water quality during the embryonic development stage. Representative freeze core samples from spawning gravels were used to assess fine sediment infiltration. Larval drift measured the number of larvae leaving the spawning grounds, a range of methodologies were used to capture 0+ to 3+ barbel. Habitat and feeding preferences were then evaluated.It was found that temperature and flow impacted movement, individuals moved through the entire river stretch, despite the presence of a weir that was previously thought of as impassable. Variations in sediment loading were found between spawning habitats, but fine sediment and organic matter were improved with gravel jetting. Larval drift and electric fishing were found to be the most effective methods for catching young barbel, but the necessary habitats to support these young fish were not readily available within the study stretch

River Crake (at Bouthrey Bridge) freeze coring report

This is the River Crake (at Bouthrey Bridge) freeze coring report produced by Lancaster University in 1999. This study looks at fine materials in river Crake at Bouthrey Bridge that may have to be considered detrimental to successful salmonid spawning. Following an observed decline in quality of salmonid fisheries at the site an investigation was initiated to assess the extent of ingress of fine sediments into the spawning gravels. Fine sediments from one potential source, upstream riverbanks, are also compared to those isolated from the spawning gravels. The percentage by weight of fine sediments for the six freeze cores, was found to be lower than first expected, given the visual appearance of the reach. However the fines were found to be distributed evenly down the cores with a marked absence of an upper, coarse gravel armour layer. In addition the median grain size (D50) of the six samples was generally low, falling to 6mm for core 5. The low median grain size and the absence of coarse grained upper strata are considered detrimental to the success rate of salmonid spawning

Sources and impacts of inorganic and organic fine sediment in salmonid spawning gravels in chalk rivers

Poor salmonid spawning habitat due to excessive fine sediment inputs has been identified as a major factor limiting survival in chalk rivers. A lack of knowledge about the complex processes and factors affecting survival was the driver for this study and gaps in the research were identified concerning the sources of fine sediment and the impact organic material had on salmonid survival in chalk streams. Consequently the main objectives of this study were to characterise spawning habitat quality of a chalk catchment, assess the sources of sediments accumulating within artificial redds, describe the composition of organic sediments using emerging technology and to create a novel method to assess the sediment oxygen consumption of those sediments. Methods were based around a catchment wide field based monitoring programme, consisting of artificially constructed spawning gravels which allowed hyporheic measurements to be taken, and sediment analysis and sediment oxygen consumption methods were carried out using different laboratory methods. Spawning habitat characteristics of the chalk catchment were found to exhibit; low sediment accumulation rates although original levels of fine sediment were high, high organic matter content, variable intra-gravel flow and intra-gravel oxygen concentrations and groundwater influences. Primary sources of fine sediment accumulating in spawning gravels and suspended sediments were found to be attributed to catchment surface sources, namely pasture (50-68%) and arable (32-50%) using inorganic and organic parameters. Organic composition of redd gravels was found to be dominated by protein material rather than humic substances, the more commonly found fluorescent compound in freshwater systems and the sediment oxygen consumption of sediments varied throughout the catchment and was found to consume the greatest oxygen in &lt;63?m size fraction. Application of sediment oxygen consumption rates to existing parameter based models that predict salmonid survival, highlighted the need to address the sensitivity of current models to rivers experiencing low sediment accumulation rates. Outcomes of this study further the knowledge of the sources, organic composition and sediment oxygen consumption capacity of fine sediments accumulating in spawning gravels which can lead to appropriate mitigation on chalk rivers to improve salmonid spawning habitat

Does fine sediment source as well as quantity affect salmonid embryo mortality and development?

Fine sediments are known to be an important cause of increased mortality in benthic spawning fish. To date, most of the research has focussed on the relationship between embryo mortality and the quantity of fine sediment accumulated in the egg pocket. However, recent evidence suggests a) that the source of fine sediment might also be important, and b) that fitness of surviving embryos post-hatch might also be impacted by the accumulation of fine sediments. In this paper, we report an experiment designed to simulate the incubation environment of brown trout (Salmo trutta) and Atlantic salmon (Salmo salar). During the experiment, the incubating embryos were exposed to different quantities of fine (&lt; 63 ?m) sediment derived from four different sources; agricultural topsoils, damaged road verges, eroding river channel banks and tertiary level treated sewage. Results showed that mass and source are independently important for determining the mortality and fitness of alevin. Differences between species were observed, such that brown trout are less sensitive to mass and source of accumulated sediment. We demonstrate for the first time that sediment source is an additional control on the impact of fine sediment, and that this is primarily controlled by the organic matter content and oxygen consumption of the catchment source material

Factors controlling dissolved oxygen in spawning gravels: Evaluation of the Sediment Intrusion and Dissolved Oxygen model (SIDO) for fisheries management

Natural and anthropogenic landscape disturbance pressures have accelerated the transfer of fine sediment to streams in forested headwater regions of the eastern slopes of the Rocky Mountains. The accumulation of fine sediment in spawning gravels can reduce survival rates of salmonid eggs by decreasing intragravel flow velocities and dissolved oxygen concentrations. The goal of this study was to examine the effect of fine sediment intrusion on the abiotic characteristics of the salmonid redd and assess the potential consequences for egg development and survival using a physically based numerical model SIDO (Sediment Intrusion and Dissolved Oxygen). Field observations from the Crowsnest River, Alberta, Canada were used to calibrate the model using flow, suspended solids and sediment accumulation data as well as high frequency dissolved oxygen (DO) measurements in spawning gravels. The impact of varying sediment inputs upon sediment intrusion rates, abiotic redd characteristics and fish egg survival rates were assessed using SIDO. Dissolved oxygen concentrations in redds were highly variable both within and between sites and varied with observed changes in river discharge and suspended sediment concentrations. Trends in measured and modelled DO concentrations in redds were generally comparable, reflecting a general decrease in dissolved oxygen levels in spawning gravels over the study period. SIDO was not sensitive to measured short term fluctuations of DO and modelled predictions of DO were higher than measured values. The quantities of sediment ingress predicted by SIDO were lower by an order of magnitude than those measured in ingress baskets. Differences between observed and modelled DO are related to the fact that this physically based model does not include terms that describe the effects of groundwater and biotic (microbial) processes on dissolved oxygen in spawning gravels. The potential of SIDO as a tool for fisheries management will be enhanced by including terms that describe groundwater and microbial processes that influence spawning gravel DO dynamics