North-west Coast Of Scotland Research Articles

Understanding weather futures based on the past: a case of Stornoway, Outer Hebrides

ABSTRACT We present a weather history for Stornoway in the Outer Hebrides, an island chain off the northwest coast of Scotland. It combines a new 164-year composite rainfall record representative of the settlement of Stornoway (1857–2019), alongside descriptive accounts of weather harvested from the school logbooks from the Nicolson Institute in Stornoway (1873–1974). The school logbooks record the experiences of the school, school children and wider community throughout the seasons. We describe the construction of the rainfall record for the period 1857–2019 and present analyses of long-term annual and seasonal variability, with a particular focus on wet/dry extremes. In examining instrumental and qualitative sources together, we consider not just climate, but also the impacts and responses of extreme weather on the communities of the Outer Hebrides and specifically Stornoway. The climate of the late nineteenth century in the Outer Hebrides was climatologically and meteorologically challenging, with harsh storms, severe cold, and droughts with notable societal impacts. School logbooks provide the opportunity to examine societal responses to past climate variability, enabling a better understanding of how future climates may be adapted and responded too.

Population Genetic Structure of Anisakis simplex Infecting the European Hake from North East Atlantic Fishing Grounds.

The European hake, one of the most commercially valuable species in ICES fishing areas, is considered an important neglected source of zoonotic risk by nematode parasites belonging to the genus Anisakis. Merluccius merluccius is, by far, the most important host of Anisakis spp. at the European fishing grounds, in terms of demographic infection values, and carries the highest parasite burden. These high parasite population densities within an individual fish host offer a chance to explore new sources of variations for the genetic structure of Anisakis spp. populations. A total of 873 Anisakis spp. third-stage larvae, originally sampled from viscera and muscular sections of hake collected at ten fishing grounds, were primarily identified using ITS rDNA region as molecular marker. After that, we used mtDNA cox2 gene to reveal the high haplotype diversity and the lack of genetic structure for A. simplex. Dominant haplotypes were shared among the different fishing areas and fish sections analyzed. Results indicate a clear connection of A. simplex from European hake along the Northern North Sea to the Portuguese coast, constituting a single genetic population but revealing a certain level of genetic sub-structuring on the Northwest coast of Scotland. This study also provides useful information to advance the understanding of parasite speciation to different fish host tissues or microenvironments.

Simulating the distribution of beached litter on the northwest coast of Scotland

Various field methods have been used globally in an attempt to understand and quantify plastic pollution. However, in regions, such as the west coast of Scotland, sparse populations, combined with complex coastlines of numerous islands, sea lochs and headlands, has resulted in limited field data. The Clyde Sea is the most populated and industrialised region on the west coast of Scotland and therefore a potential source of land-based plastic litter to the less populated coast to the north. This study first presents an analysis of Marine Conservation Society (MCS) citizen-science beach-clean data, from 1994 to 2019, revealing spatial patterns between beach-clean sites. Plastic litter was categorised into land, marine and unknown sources, with the most common items in these three categories being crisp packets, fishing rope and fragments, respectively. On the west coast of Scotland there is on average 380.3 ± 419.9 plastic items per 100 m of coast, with the site average number of items recovered ranging from 1–2,355 per 100 m of coast. To simulate marine plastic litter movement from the Clyde Sea to a defined northwest model sub-area, an unstructured-grid hydrodynamic model was coupled with a particle tracking model subject to currents, diffusion, and wind. Three coastal boundary conditions were used to compare transport paths with or without particle beach resuspension, and for the resuspending cases, with or without a distinction between coastal type (retentive beaches versus reflective rocky coasts). Of the total released particles, the percentage that beached within the model sub-area, after a 1-year model run, ranged between 45.7% and 88.3% depending on the coastal boundary condition. The Clyde Sea was found to be a potential source of beached land-based plastic litter to the north, as on average, 6.8% (range: 2.9%–11.7%) of particles exited the Clyde Sea, crossed a defined northern boundary, and beached on the northwest coast. Both hydrodynamic and particle tracking models were tested, and the varying boundary conditions were compared to investigate holistic methodologies to better understand plastic pollution.

An LCA of the Pelamis wave energy converter

PurposeTo date, very few studies have attempted to quantify the environmental impacts of a wave energy converter, and almost all of these focus solely on the potential climate change impacts and embodied energy. This paper presents a full life cycle assessment (LCA) of the first-generation Pelamis wave energy converter, aiming to contribute to the body of published studies and examine any potential trade-offs or co-benefits across a broad range of environmental impacts.MethodsThe process-based attributional LCA was carried out on the full cradle-to-grave life cycle of the Pelamis P1 wave energy converter, including the device, its moorings and sub-sea connecting cable up to the point of connection with the grid. The case study was for a typical wave farm located off the north-west coast of Scotland. Foreground data was mostly sourced from the manufacturer. Background inventory data was mostly sourced from the ecoinvent database (v3.3), and the ReCiPe and CED impact assessment methods were applied.Results and discussionThe Pelamis was found to have significantly lower environmental impacts than conventional fossil generation in 6 impact categories, but performed worse than most other types of generation in 8 of the remaining 13 categories studied. The greatest impacts were from steel manufacture and sea vessel operations. The device performs quite well in the two most frequently assessed impacts for renewable energy converters: climate change and cumulative energy demand. The carbon payback period is estimated to be around 24 months (depending on the emissions intensity of the displaced generation mix), and the energy return on investment is 7.5. The contrast between this and the poor performance in other impact categories demonstrates the limitations of focussing only on carbon and energy.ConclusionsThe Pelamis was found to generally have relatively high environmental impacts across many impact categories when compared to other types of power generation; however, these are mostly attributable to the current reliance on fossil fuels in the global economy and the early development stage of the technology. Opportunities to reduce this also lie in reducing requirements for steel in the device structure, and decreasing the requirements for sea vessel operations during installation, maintenance and decommissioning.

Characterisation of the mantle transcriptome and biomineralisation genes in the blunt-gaper clam, Mya truncata

Members of the Myidae family are ecologically and economically important, but there is currently very little molecular data on these species. The present study sequenced and assembled the mantle transcriptome of Mya truncata from the North West coast of Scotland and identified candidate biomineralisation genes. RNA-Seq reads were assembled to create 20,106 contigs in a de novo transciptome, 18.81% of which were assigned putative functions using BLAST sequence similarity searching (cuttoff E-value 1E−10). The most highly expressed genes were compared to the Antarctic clam (Laternula elliptica) and showed that many of the dominant biological functions (muscle contraction, energy production, biomineralisation) in the mantle were conserved. There were however, differences in the constitutive expression of heat shock proteins, which were possibly due to the M. truncata sampling location being at a relatively low latitude, and hence relatively warm, in terms of the global distribution of the species. Phylogenetic analyses of the Tyrosinase proteins from M. truncata showed a gene expansion which was absent in L. elliptica. The tissue distribution expression patterns of putative biomineralisation genes were investigated using quantitative PCR, all genes showed a mantle specific expression pattern supporting their hypothesised role in shell secretion. The present study provides some preliminary insights into how clams from different environments – temperate versus polar – build their shells. In addition, the transcriptome data provides a valuable resource for future comparative studies investigating biomineralisation.

Genetic structure of the tall sea pen Funiculina quadrangularis in NW Scottish sea lochs

AbstractThe tall sea pen Funiculina quadrangularis has a patchy distribution around the UK, being found in sheltered waters below 20 m depth on the northwest coast of Scotland and Ireland. The limited distribution and sensitivity to bottom fishing activities make F. quadrangularis vulnerable to reduction in population numbers that may lead to genetic isolation and reduced diversity. Because of this vulnerability and low resilience to physical disturbance, the tall sea pen is recognised as a Species of Principle Importance under the Natural Environment and Rural Communities Act, 2006, UK. (http://www.legislation.gov.uk/ukpga/2006/16/contents) and is also on the Biodiversity Action Plan list of Priority Species for the UK. In the Mediterranean it is recognised as a sensitive and essential fish habitat because it forms habitat for several commercially important crustaceans. The aim of this study was to understand the current state of the genetic structure and gene flow of F. quadrangularis in areas of NW Scotland. We developed 10 microsatellite markers and used them to genotype 176 samples from four populations. Overall, our results suggest that there is high genetic diversity and high gene flow between colonies of F. quadrangularis in and among locations in Loch Linnhe and Loch Duich. As a result of the high rates of gene flow, genetic differentiation between sites was low. This may provide resilience to human impacts if distant populations have a high connectivity. However, care must be taken, as small but significant isolation by distance was found between the most geographically distant sites and only a small part of the species range was examined in this study. The genetic tools developed here will provide a foundation for wider studies of this vulnerable species.

Rhythm and Mobility in the Inner and Outer Hebrides: Archipelago as Art-Science Research Site

This paper explores some of the dimensions of mobility and rhythm emerging from a voyage to the Inner and Outer Hebrides, island collectives on the North West Coast of Scotland. In the summer of 2011, this voyage, combining boat, water and islands, as well as their inhabitants, became a research site for members of Cape Farewell, an organisation that seeks to produce creative responses to climate change. Crew members specifically sought to consider the impact of climate change on island cultures and ecologies, and the sustainability and preservation initiatives deployed here, as well as broader indicators of climate change in the area. Using participant observation of the voyage and interviews, we examine the bodily experienced, rhythmic aspects of the voyage itself; that is, the aesthetics via which the spaces and places of the Inner and Outer Hebrides became known and felt. We consider especially the rhythms of nature and the sea that encompass the motility of materials that are central to a ‘politics of mobility’ that, for Cape Farewell, characterises these islands as frontiers of climate change.

Visual, seascape and landscape analysis to support coastal aquaculture site selection

The visual impact of aquaculture is a controversial issue and in some countries must be assessed prior to any new development. However, at present, there are no definitive, objective methods used to evaluate the potential visual impacts of new aquatic farms and therefore assessment is difficult for both developers and regulators. This study presents a GIS based methodology for use in the visual assessment of a potential new coastal fish farm development, focusing on both sea cages and the associated land based structures. The methodology has been applied to a case study area, the Western Isles located off the North West coast of Scotland, which already has an extensive aquaculture industry and significant potential for future growth.Using a two stage sequential modelling process, the methodology combines visual, seascape and landscape analysis within a GIS environment to produce spatial models indicating where there is the potential for new aquaculture development with minimal visual impact. The preliminary visual assessment model combines a series of Boolean viewsheds with landscape and seascape sensitivity models to assess the potential visibility across different user groups and the sensitivity of the area to visual change. The second stage focuses on an area identified from the preliminary model as having potential for development and then performs a more detailed analysis using a site specific proportional visual impact model. This model quantifies the impact by assessing the proportion of viewpoints from which the proposed development can actually be seen. Both stages of the modelling process provide valuable information and support for decision makers regarding the potential visual impacts of aquaculture.

Space‐time modelling of blue ling for fisheries stock management

Fishery catch data offer a rich potential source of information for management, if modelling can separate out the effects of fishing effort, species behaviour and population abundance. Here, we model catch data from the blue ling fishery off the northwest coast of Scotland, using generalised additive mixed models with a space time interaction represented via a novel tensor product of a soap film smooth of space with a penalized regression spline of time. The use of soap film smoothers avoids imposing correspondences between spatially adjacent areas that are in fact separated by the stock boundary. The comparison of the performance of the soap film smooth for space–time with that of a thin plate regression spline based on root mean squared prediction errors and k‐means cross‐validation suggests that in this application, the former is better overall and in particular for modelling local changes. Further, a model with continuous space‐year interaction performed better compared with one with an additive space‐year effect. After model selection, checking and validation, there is evidence for increasing blue ling abundance from 2000–2010 in some spatial locations. Copyright © 2013 John Wiley & Sons, Ltd.

Persistent organic pollutants and trace metals in sediments close to Scottish marine fish farms

The global demand for aquatic food products is increasing and the aquaculture industry is expanding as it strives to meet this increasing demand. There are concerns about the environmental impact of aquaculture to the seabed close to fish-farm cages, including potential effects from persistent organic pollutants and trace metals, which may come from the feed or anti-foulants on the cages. To determine if this could be a problem in Scotland, three main aquaculture areas were examined; Western Isles, North-West Coast of Scotland and the Shetland Isles. Samples of sediment were collected from various sea lochs in these areas in 2005 and 2006 and concentrations of persistent organic pollutants (polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs)) and trace metals (copper (Cu) and zinc (Zn)) were determined. Concentrations of PCBs were below the EAC (environmental assessment criteria) for all bar one congener in one sample, and below the BAC (background assessment concentration) for most. PBDE concentrations in the sea lochs are comparable with those found at remote sites around Scotland and comparable with the lower end of concentrations found in the more industrialised Firth of Clyde. Although slightly elevated Cu and Zn concentrations were measured in sediments from < 330 m from some farms, concentrations in sediments outwith 25 m from any farm are below those that cause benthic effects. Only the farms in Loch Shell, Loch Greshornish and Loch Kishorn had concentrations for Cu and Zn which might cause adverse affects in the environment, and all of these samples were from within 25 m of the cages. Therefore it was concluded that any impact on the environment from organic pollutants or trace metals is of a local nature.

Acoustic detection of UHE neutrinos – the ACORNE project

An interesting new possibility of detection of ultra-high energy (UHE) neutrinos is that of acoustic detection whereby the acoustic pressure pulse generated as a UHE neutrino interacts in a suitable medium such as water or ice is detected by an array of acoustic sensors. Recent years have seen something of a renaissance of this field and there are currently a number of activities worldwide to assess the potential of this technique. The UK-based ACORNE collaboration is one of these activities; ACORNE has access to the QinetiQ underwater acoustic range off Rona, an island off the North-West coast of Scotland. The poster will summarise ACORNE's R&D work, including simulation of the thermoacoustic emission of neutrino-induced particle cascades, reconstruction of event vertices and the effects of refraction, potential neutrino flux sensitivities from large area hydrophone arrays, a study transducer based calibration techniques and an analysis of the first acoustic data recorded by the Rona hydrophone array.

Spatial and temporal distribution of Lepeophtheirus salmonis (Krøyer) larvae in a sea loch containing Atlantic salmon, Salmo salar L., farms on the north‐west coast of Scotland

A plankton survey investigated spatial and temporal distributions of larval sea lice in a sea loch on the north-west coast of Scotland. Plankton tows were collected approximately weekly at two depths (0 and 5 m) at five sample stations over a 2-year period. The survey began in March 2002 when Atlantic salmon, Salmo salar L., farms in the study area stocked with fish and finished in March 2004, after farms completed harvesting. Over 90% of lice recovered were Lepeophtheirus salmonis (Krøyer); therefore, the results of this paper refer largely to that species. The data were analysed using generalized additive models with explanatory variables for time, depth and station. Greatest densities of nauplii were recovered at stations adjacent to farms indicating that the local salmon farms were a likely source of larvae at times during the production cycle. There were significant temporal trends in larval densities and the stocking and harvesting of farms can possibly account for these increases and decreases, particularly at the start and at the end of the production cycle. The distribution of copepodids was more widespread than that of nauplii, indicating that the larvae can be transported several kilometres from the point of release.

Otter Surveys of the North West Scottish Islands

Between 1995 and 2003, otter surveys were conducted on 11 islands off the north west coast of Scotland. These located holts in a 100-metre-wide strip along the coasts of these islands. The information was then used to calculate the total number of holts for each island, and from that the adult otter population for each island was calculated using the models based on studies in Skye and Shetland. The diet of marine-foraging otters was assessed from five of these islands using spraint analysis, and was compared with the diet of otters from other coastal areas in Scotland. With the exception of the free-swimming saithe, the diet was dominated by small benthic fish, with the five key prey species being viviparous blenny, five-bearded rockling, butterfish, sea scorpion, and saithe.

Enhanced production of the sea urchin Paracentrotus lividus in integrated open-water cultivation with Atlantic salmon Salmo salar

Survivorship and performance was investigated for two size classes of the sea urchin Paracentrotus lividus grown adjacent to open-water Atlantic salmon (Salmo salar) cultivation on the north-west coast of Scotland. Juvenile P. lividus were maintained for 12 months at 0 m, 50 m and 2.5 km from the mariculture activity. The sea urchins at the 0 m station showed higher survivorship than at the 50 m and 2.5 km stations and had significantly greater test diameter than at the 50 m station. Only urchins at 0 m developed gonads and, although small, these were of acceptable or excellent colouration in terms of their marketability. Adult P. lividus were maintained for 3 months at 0 m and 15 m from the mariculture activity, either with or without additional macroalgae Laminaria spp. Sea urchins at the 0 m station and fed additional macroalgae showed higher gonadal growth than sea urchins at the 15 m station held without additional food. Gonad colouration in the adult urchins, irrespective of the treatment, was acceptable or excellent. The 0 m station also received significantly greater quantities of particulate organic matter (POM) than the other stations in both the juvenile and adult experiments. At the 0 m station, the presence of the fatty acid 22:1n-11 and elevated levels of the long chain n-3 fatty acid DHA 22:6n-3 in the gonadal tissue of the urchins confirmed the consumption of fish farm derived POM and highlighted the potential human health benefits from consuming sea urchin roe.The results show that P. lividus can thrive in the salmon culture environment and suggests that the integration of P. lividus with Atlantic salmon can provide a viable means to culture this species, even at this northerly latitude. Salmon-sea urchin co-culture would enable fish farms to diversify into producing a second highly valuable product and would reduce the increasing worldwide pressure of sea urchin fisheries on wild stocks.

Levels of intra-host and temporal sequence variation in a large CO1 sub-units from Anisakis simplex sensu stricto (Rudolphi 1809) (Nematoda: Anisakisdae): implications for fisheries management

This paper is the first to address the suitability and potential of the cytochrome oxidase-1 (CO1) region of the parasitic marine nematode Anisakis simplex sensu stricto as a genetic marker. A. simplex s.s. is an ubiquitous parasite of many marine organisms and has been used as a ‘biological tag’ for population studies of pelagic fish stocks. The CO1 marker informs not only about nematode population structure but also about its hosts. The large CO1 sub-unit (∼800 bp) was analysed from third stage larvae of A. simplex s.s. from Atlantic herring, Clupea harengus L. caught off the north-west coast of Scotland. In total 161 A. simplex s.s. CO1 sequences were analysed from 37 herring that represented three spawning periods over 2 years. Overall very high haplotype and low nucleotide diversities were observed (h = 0.997 and π = 0.008, respectively). These results are in keeping with studies investigating parasitic nematodes of ungulates and are symptomatic of the high rate of substitutions accumulated by mtDNA and effective dispersal strategies of the parasite. The Tamura-Nei I + Г (Г = 1.2243) model of nucleotide substitution best suited the present data which were dominated by a high thymine bias and associated transitions. Large within population differences were highlighted by hierarchal AMOVAs with little variation related to spawning events or years which may indicate localised temporal stability. Temporal homogeneity in the CO1 gene coupled with the ubiquitous and widespread nature of the parasite indicates both the potential and limitations for its incorporation in stock-separation studies of its hosts.

Application of the Gómez-Muñoz model to estimate catch and effort in squid fisheries in Scotland

The Gómez-Muñoz model, which utilises interview data obtained from fishermen, was developed to aid the management of small-scale artisanal fisheries, where there may be a dearth of catch and effort data, and has been successfully used in the estimation of catch per unit effort (CPUE) in this type of fishery in Galicia. The suitability of applying the model to two cases in Scotland, a non-targeted by-catch fishery off the northwest coast of Scotland and a directed squid fishery in the Moray Firth, is explored. The interview information returned from the directed fishery is generally of higher quality. In order to study the model behaviour, an alternative parameterisation is carried out. In general, the model was found to be most sensitive to parameters having a direct effect on catch and effort. Calculated confidence intervals are rather wide but could be improved by refining the interview protocol with emphasis placed on reducing the timing from monthly to weekly. A database of 671 individual vessels’ landings into Scottish ports in 2000 is created and, from this, an index of fishing effort calculated, which displays a close approximation with official data. The results from the by-catch fishery are extrapolated to larger areas. In all cases, the predicted catches are higher than official figures although similar trends are evident.

Levels of Hexabromocyclododecane in Harbor Porpoises and Common Dolphins from Western European Seas, with Evidence for Stereoisomer-Specific Biotransformation by Cytochrome P450

Commercial hexabromocyclododecane (HBCD) is a high-production-volume flame-retardant applied in polystyrene foams. It contains three stereoisomers, of which gamma-HBCD always dominates. Here we report on the levels of HBCD in blubber of harbor porpoise and common dolphin from different European seas. The highest total (sigma)-HBCD levels were measured in harbor porpoises stranded on the Irish and Scottish coasts of the Irish Sea (median concentration 2.9 microg (g of lipid)(-1)) and the northwest coast of Scotland (median concentration 5.1 microg (g of lipid)(-1)). The median levels in other areas were, for the harbor porpoise south coast of Ireland, 1.2 microg (g of lipid)(-1), for the coasts of The Netherlands, Belgium, and France north of Calais (southern North Sea), 1.1 microg (g of lipid)(-1), for the east coast of Scotland (northern North Sea), 0.77 microg (g of lipid)(-1), and, for Galicia (Spain), 0.1 microg (g of lipid)(-1). The median levels for the common dolphin were, for west coast of Ireland, 0.9 microg (g of lipid)(-1), for the French coast of the English Channel between Normandy and Brest, 0.4 microg (g of lipid)(-1), and, for Galicia, 0.2 microg (g of lipid)(-1). A subset of 10 harbor porpoise and 9 common dolphin blubber samples representing all areas were analyzed by LC/MS to determine the diastereomeric composition of their HBCD residues. All samples showed exclusively the peak of alpha-HBCD. To test if biotransformation by the cytochrome P450 system could explain the observed compositional difference with technical HBCD mixtures, a number of in vitro assays with microsomal preparations of liver were carried out. We had to revert to material stored at -80 degrees C from laboratory rats and a fresh harbor seal found dead in the Dutch Wadden Sea, since such liver samples of cetaceans were not in our possession. The in vitro assays showed that beta- and gamma-HBCDs were indeed significantly metabolized when incubated in the presence of NADPH as electron donor, compared to a set of reference samples which were identical except for the addition of NADPH. In contrast, the peak of alpha-HBCD did not decrease significantly in the presence of NADPH. In separate microsomal assays with beta- and gamma-HBCDs, new peaks of brominated compounds (signal at m/z = 79 or 81) with masses of [M + 0] were formed only when NADPH was added. This confirms the process of cytochrome P450 mediated biotransformation. Although rat and harbor seal belong to different families of the mammalia than the cetaceans, we propose that biotransformation by the cytochrome P450 system is also the most likely process to explain the exclusive accumulation of alpha-HBCD in harbor porpoise and common dolphin.

Physicochemical properties of atmospheric aerosol at South UIST

Four field campaigns over the period November 1993 to August 1994 were undertaken on the island of South Uist, off the northwest coast of Scotland as part of the BMCAPE project. Measurements were made of the concentration and chemical composition of aerosol particles, utilising a variety of instruments. Sulphur and nitrogen gas species were also measured throughout these campaigns, together with appropriate meteorological parameters. A variety of air mass types were encountered during the campaigns and the relationship between the physical and chemical aerosol properties are discussed in terms of air mass histories and season factors.

Waveform inversion of deep seismic reflection data: the polarity of mantle reflections

The Flannan and W-reflectors are two prominent mantle features observed on seismic reflection data off the northwest coast of Scotland. They are the brightest, most laterally extensive, intra-mantle reflectors identified on a deep seismic dataset anywhere in the world. Despite extensive study, their physical origin is still the subject of speculation. We present a scheme to determine the polarity of these mantle reflectors, and constrain their upper structure using near-normal-incidence seismic reflection data. The technique exploits the convolutional model of the earth; we use a deterministic source-signature deconvolution to invert the data. We have explored the parameterization of the inversion by testing real and synthetic data. We find that it is critical to the legitimacy of the reflectivity model that many traces are stacked prior to the inversion and that the data have a good signal-to-noise ratio. Furthermore, an accurate estimate of the effective source wavelet is a fundamental requirement for obtaining a valid reflectivity model; in particular we find the deconvolution results are most sensitive to the precise value of the water depth and reflection coefficient used in estimating the sea-bed multiple train. In the case of the Flannan-reflector, the inversion shows unequivocally that it has a positive polarity. Modelling the W-reflector is less straightforward as a result of reduced signal-to-noise ratio. None-the-less, the inversion suggests a positive polarity for the W-reflector, in agreement with observations of post-critical reflections seen on wide-angle seismic data. The near-normal-incidence polarity measurements support the suggestion that both the Flannan and W-reflectors represent an eclogitic slab, presumably a relict oceanic subduction zone, preserved within the continental lithospheric mantle.

A three dimensional hydrodynamic model of tides off the north-west coast of Scotland

Abstract A three dimensional hydrodynamic model using a fine 1 12 ° × 1 12 ° finite difference grid in the horizontal with a spectral approach in the vertical is used to examine the spatial distributions of the M2 and O1 tidal elevations and currents at the shelf edge. The region chosen for the study is the Malin-Hebrides shelf off the west coast of Scotland, where a set of offshore elevation and current meter data exists. Calculations show that M2 tidal elevations and currents increase rapidly from ocean to shelf having the largest amplitude in the near shore regions. In contrast O1 elevations and currents are intensified at the shelf edge showing spatial changes corresponding to a first mode shelf wave. Computed O1 current ellipses show significant small scale horizontal spatial variability in the shelf edge region. Comparison of computed and observed M2 tidal currents, shows that away from abrupt changes in topography, the model can adequately reproduce the currents, although in regions of rapid change in water depth a finer grid is probably required. Calculations show that with the finite difference grid used here the intensity and the spatial variability of the O1 tidal currents in the shelf edge region is strongly influenced by the magnitude of horizontal eddy viscosity, the exact formulation of which is poorly known.