Home About us Contact | |||
Irish Sea (irish + sea)
Selected AbstractsPatterns in the spawning of cod (Gadus morhua L.), sole (Solea solea L.) and plaice (Pleuronectes platessa L.) in the Irish Sea as determined by generalized additive modellingFISHERIES OCEANOGRAPHY, Issue 1 2000Eleven ichthyoplankton cruises were undertaken covering most of the Irish Sea during the period February to June, 1995. To identify spawning localities and investigate temporal trends in egg production, the data on stage 1 A egg distributions of cod (Gadus morhua), plaice (Pleuronectes platessa) and sole (Solea solea) have been modelled using generalized additive models (GAMs). A two-stage approach was adopted where presence/absence was firstly modelled as a binary process and a GAM surface subsequently fitted to egg production (conditional on presence). We demonstrate that this approach can be used to model egg production both in space and in time. The spawning sites for cod, plaice and sole in the Irish Sea were defined in terms of the probability of egg occurrence. For cod, we demonstrate that by integrating under predicted egg production surfaces, a cumulative production curve can be generated and used to define percentiles of production and thus delimit the extent of the spawning season. However, for plaice and sole, the surveys did not fully cover the spawning season and the limitations that this imposes on GAM modelling of these data are discussed. Comparison of the spawning sites in 1995 with historical data suggests that the locations of cod, plaice and sole egg production in the Irish Sea have probably remained relatively constant over the last 30 years. [source] GPS tracking of the foraging movements of Manx Shearwaters Puffinus puffinus breeding on Skomer Island, WalesIBIS, Issue 3 2008T. C. GUILFORD We report the first successful use of miniature Global Positioning System loggers to track the ocean-going behaviour of a c. 400 g seabird, the Manx Shearwater Puffinus puffinus. Breeding birds were tracked over three field seasons during the incubation and chick-rearing periods on their foraging excursions from the large colony on Skomer Island, Pembrokeshire, UK. Foraging effort was concentrated in the Irish Sea. Likely foraging areas were identified to the north, and more diffusely to the west of the colony. No foraging excursions were recorded significantly to the south of the colony, conflicting with the conclusions of earlier studies based on ringing recoveries and observations. We discuss several explanations including the hypothesis that foraging may have shifted substantially northwards in recent decades. We found no obvious relationship between birds' positions and water depth, although there was a suggestion that observations at night were in shallower water than those during the day. We also found that, despite the fact that Shearwaters can be observed rafting off-shore from their colonies in the hours prior to making landfall at night, breeding birds are usually located much further from the colony in the last 8 h before arrival, a finding that has significance for the likely effectiveness of marine protection areas if they are only local to the colony. Short sequences of precise second-by-second fixes showed that movement speeds were bimodal, corresponding to sitting on the water (most common at night and around midday) and flying (most common in the morning and evening), with flight behaviour separable into erratic (indicative of searching for food) and directional (indicative of travelling). We also provide a first direct measurement of mean flight speed during directional flight (c. 40 km/h), slower than a Shearwater's predicted maximum range velocity, suggesting that birds are exploiting wave or dynamic soaring during long-distance travel. [source] IDS40: Reflections from Across the Irish SeaIDS BULLETIN, Issue 2 2007Mary McKeown No abstract is available for this article. [source] Ecological relevance of temporal stability in regional fish catchesJOURNAL OF FISH BIOLOGY, Issue 5 2003H. Hinz The concept of habitat selection based on ,Ideal Free Distribution' theory suggests that areas of high suitability may attract larger quantities of fishes than less suitable or unsuitable areas. Catch data were used from groundfish surveys to identify areas of consistently high densities of whiting Merlangius merlangus, cod Gadus morhua and haddock Melanogrammus aeglefinus in the Irish Sea and plaice Pleuronectes platessa, sole Solea solea, lemon sole Microstomus kitt in the English Channel over a period of 10 and 9 years respectively. A method was introduced to delineate areas of the seabed that held consistently high numbers of fishes objectively from large datasets. These areas may constitute important habitat characteristics which may merit further scientific investigations in respect to ,Essential Fish Habitats'(EFH). In addition, the number of stations with consistently high abundances of fishes and the number of stations where no fishes were caught gave an indication of the site specificity of the fish species analysed. For the gadoids, whiting was found to be less site specific than cod and haddock, while for the flatfishes, plaice and sole were less site specific than lemon sole. The findings are discussed in the context of previously published studies on dietary specializm. The site specificity of demersal fishes has implications for the siting process for marine protected areas as fish species with a strong habitat affinity can be expected to benefit more from such management schemes. [source] Dating the introduction of cereal cultivation to the British Isles: early palaeoecological evidence from the Isle of ManJOURNAL OF QUATERNARY SCIENCE, Issue 7 2003James B. Innes Abstract The adoption of cereal cultivation is a key benchmark in the transition from Mesolithic hunter,gatherer foraging to Neolithic farming economies, but the nature, timing and ecological,cultural context of the earliest cereal use in the British Isles and northwest Europe is still uncertain. We present AMS radiocarbon dating and fine-resolution pollen evidence from the Isle of Man for cereal growing in the latter stages of a distinct episode of forest disturbance at almost 6000,yr,BP (uncalibrated). The coherent ecological structure of this phase at the fine resolution level suggests that it records cereal cultivation well before the Ulmus decline, rather than wild grass pollen grains. This example is one of a cluster of early dates for cereal-type pollen near the start of the sixth millenium BP, including several around the Irish Sea, which indicate that the introduction of cereal agriculture probably occurred as early in the central British Isles as in the northern European plain. This early cereal phase is followed later by a probable phase of pre- Ulmus decline pastoral activity. We also report Mesolithic age woodland disturbance around 7000,yr,BP (uncalibrated) and the first radiocarbon dates for mid-Holocene forest history of the Isle of Man. Copyright © 2003 John Wiley & Sons, Ltd. [source] Context dependency of relationships between biodiversity and ecosystem functioning is different for multiple ecosystem functionsOIKOS, Issue 12 2009Jan Geert Hiddink Increasing concern over the loss of biodiversity has led to attempts to quantify relationships between biodiversity and ecosystem functioning. While manipulative investigations have accumulated substantial evidence to support the notion that decreasing biodiversity can be detrimental to the functioning of ecosystems, recent investigations have identified the potential importance of physical processes in moderating biodiversity , ecosystem function relationships at larger geographical scales. In this study, the relationship between the genus richness of benthic macro-invertebrates and five measures of ecosystem functioning (macrofaunal biomass, depth of the apparent redox discontinuity, fluxes of ammonium and NOx and the abundance of nematodes) was determined over a large scale wave-induced bed shear stress gradient on the seabed of the northern Irish Sea. Ecosystem functioning was significantly correlated to genus richness for four out of five ecosystem functions. However, wave stress moderated the genus richness , ecosystem functioning relationship for only one of the ecosystem functions; genus richness had a positive effect on the depth of the apparent redox discontinuity in the sediment at high wave stress but not at low wave stress. These results indicate that the effects of biodiversity on some ecosystem functions may be sufficiently strong to generate patterns in ecosystems where other factors are also affecting ecosystem processes, but that the biodiversity,ecosystem function relationship for can be dependent on environmental conditions for specific ecosystem functions. [source] ISLANDSCAPES AND ,ISLANDNESS': THE PREHISTORIC ISLE OF MAN IN THE IRISH SEASCAPEOXFORD JOURNAL OF ARCHAEOLOGY, Issue 2 2008CATHERINE FRIEMAN Summary. This paper will explore the role of the Isle of Man in the prehistory of the Irish Sea area through an examination of its changing islandscape from the Neolithic through the Iron Age. It was far from insular during prehistory, but the social and economic interactions of prehistoric Manx people around the Irish Sea and beyond were heavily affected by their water-bound environment. The way that the prehistoric Manx perceived their boundaries and their coastal situation is reflected in their ritual and social landscape, their preferential use of coastal areas for monumental architecture, and in the choices they made with regard to the island landscape they inhabited. This culturally constructed sense of islandness allowed the prehistoric Manx people to maintain distinctive local cultures while still playing an active role in the larger Irish Sea region. [source] Places Of Transformation: Building Monuments From Water And Stone In The Neolithic Of The Irish SeaTHE JOURNAL OF THE ROYAL ANTHROPOLOGICAL INSTITUTE, Issue 1 2003CHRIS FOWLER Using the Irish Sea area as a case-study, we argue that both sites and landscapes can be understood as containing a series of components procured from the landscape and from human, animal, and object bodies. These components were organized in a way that commented on and related to specific cultural relationships between these different locations and through the substances found within them. This idea is explored by examining Neolithic monuments, material culture, and natural materials in southwest Wales, northwest Wales, the Isle of Man, and southwest Scotland. We trace some metaphorical schemes which were integral to Neolithic activity in this part of the Irish Sea. In particular, we highlight the metaphorical connections between water and stone in places associated with transformation, particularly the repeated transformation of human bodies. We suggest that the series of associations present in the Neolithic were not invested with a uniform meaning but, instead, were polyvalent, subject to conflicting interpretations, contextually specific and variable through both space and time. The relationship between these elements was therefore dependent on the contexts of their association. Nevertheless, the association of water and stone can be found repeatedly throughout the Neolithic world and may have been the medium of a powerful trope within broader conceptions of the world. This article is intended as a preliminary consideration of these issues (particularly the links between stone, mountains, water, quartz, shell, and human remains) and is offered as a thinking-point for ongoing research in this area. [source] The detection of elements in larval otoliths from Atlantic herring using laser ablation ICP-MSJOURNAL OF FISH BIOLOGY, Issue 4 2003D. Brophy Trace element concentrations of otoliths from larval herring Clupea harengus collected from known spawning beds in the Celtic and Irish Seas, were investigated using laser ablation ICP-MS and compared with concentrations in the larval cores of juvenile otoliths from the same populations and year class. A range of elements (Mg, Zn, Sr, Ba and Pb) was detectable in early larval otoliths (20,40 µm diameter). Larval otolith concentrations exceeded the larval core concentrations of juvenile otoliths and also the concentrations reported in the literature, for Mg, Zn, Ba and Pb, indicating that the measurement of elements in larval otoliths was severely affected by post-mortem contamination, most likely due to adherence of tissue and endolymph residue on the otolith surface. Comparison of otolith composition between larvae from two freezing treatments showed that contamination from Mg and Zn was more serious in otoliths that had remained in frozen larvae for prolonged periods. Larval populations from the two seas showed significant differences in otolith Sr concentrations, which were consistent over two sampling years. Similar differences were seen in the corresponding juvenile populations. The results show that while early larval otoliths are extremely susceptible post-mortem contamination, Sr concentrations can be reliably measured using laser ablation ICP-MS and for this element, the detection of region specific differences is possible. [source] Seasonal variations in nitrate reductase activity and internal N pools in intertidal brown algae are correlated with ambient nitrate concentrationsPLANT CELL & ENVIRONMENT, Issue 6 2007ERICA B. YOUNG ABSTRACT Nitrogen metabolism was examined in the intertidal seaweeds Fucus vesiculosus, Fucus serratus, Fucus spiralis and Laminaria digitata in a temperate Irish sea lough. Internal NO3 - storage, total N content and nitrate reductase activity (NRA) were most affected by ambient NO3 - , with highest values in winter, when ambient NO3 - was maximum, and declined with NO3 - during summer. In all species, NRA was six times higher in winter than in summer, and was markedly higher in Fucus species (e.g. 256 ± 33 nmol NO3 - min,1 g,1 in F. vesiculosus versus 55 ± 17 nmol NO3 - min,1 g,1 in L. digitata). Temperature and light were less important factors for N metabolism, but influenced in situ photosynthesis and respiration rates. NO3 - assimilating capacity (calculated from NRA) exceeded N demand (calculated from net photosynthesis rates and C : N ratios) by a factor of 0.7,50.0, yet seaweeds stored significant NO3 - (up to 40,86 µmol g,1). C : N ratio also increased with height in the intertidal zone (lowest in L. digitata and highest in F. spiralis), indicating that tidal emersion also significantly constrained N metabolism. These results suggest that, in contrast to the tight relationship between N and C metabolism in many microalgae, N and C metabolism could be uncoupled in marine macroalgae, which might be an important adaptation to the intertidal environment. [source] |