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Geffen A.J.,University of Liverpool | Nash R.D.M.,University of Liverpool | Nash R.D.M.,Norwegian Institute of Marine Research | Dau K.,University of Liverpool | And 4 more authors.
Journal of Experimental Marine Biology and Ecology | Year: 2011

The settlement, growth and mortality of plaice (Pleuronectes platessa L.) were examined on a small nursery ground (Port Erin Bay, Isle of Man) in the Irish Sea in 1993 and between 1996 and 2000. The timing, duration and strength of juvenile settlement varied between years and were positively correlated with the duration and quantity of egg production. Otolith increment counts were used to determine the age and metamorphosis and/or settlement dates of fish and to compare settlement patterns inferred from catch data with those inferred from age data. The catch data suggested two 'pulses' of settlement in Port Erin Bay whereas the otolith age data indicated three main settlement events. Over the years the first sub-cohort was generally the largest and overall this sub-cohort suffered the highest mortality. This first sub-cohort may have a "high risk" strategy and swamp potential predators early in the settlement period, with the result that the second sub-cohort generally has faster growth rate and lower mortality. A release of predatory pressure on the second sub-cohort could be a cause of large year classes in plaice populations. Growth rates were lowest for fish in the first sub-cohort, likely reflecting density-dependent effects and less optimal environmental conditions early in the year. The variations in instantaneous mortality rate between sub-cohorts, as well as inter-annually within sub-cohorts, illustrate the complex dynamics in the structure of these juvenile plaice populations on the nursery grounds. Global environment change effects are visible in the wider Irish Sea plaice population dynamics, with temperature dependent nursery ground processes as one of the contributing mechanisms. © 2011 Elsevier B.V. Source


Kettel E.F.,University of Nottingham | Kettel E.F.,Nottingham Trent University | Perrow M.R.,ECON Ecological Consultancy Ltd. | Reader T.,University of Nottingham
European Journal of Wildlife Research | Year: 2016

The harvest mouse (Micromys minutus) is understudied compared to other small mammals as a result of its small size and scansorial habits. This study in wetlands dominated by common reed (Phragmites australis) compared nest census, a commonly used technique to confirm presence/absence and monitor populations, with live-trapping using Longworths and a home-made alternative trap (the Jordan trap) set both on the ground and in the stalk zone (∼1 m from ground or water level). Nests were found at only two of the four study sites, which may have suggested an absence of the species. However, harvest mice were caught in traps at all sites. All 108 captures of 39 individuals were made in aerial traps in the stalk zone with none caught in ground traps. Generalised linear mixed model (GLMM) also showed that significantly more captures were made in Longworth traps compared to the Jordan trap, although the efficiency of the latter increased after modification. There were also significant differences in capture rate between sites and season and a preference for higher reed quality as described by PCA in the wetter areas of the reed-beds studied. We conclude that live-trapping is preferable to nest census as a population monitoring technique and that future studies of harvest mice, especially in tall wetland vegetation, should use Longworth traps and/or cheaper home-made alternatives set in the stalk zone. © 2016 The Author(s) Source


Skeate E.R.,ECON Ecological Consultancy Ltd. | Perrow M.R.,ECON Ecological Consultancy Ltd. | Gilroy J.J.,ECON Ecological Consultancy Ltd. | Gilroy J.J.,Rutgers University
Marine Pollution Bulletin | Year: 2012

Scroby Sands offshore wind farm was built close to a haul-out and breeding site for harbour seal, a species of conservation concern. An aerial survey programme conducted during a five-year period spanning wind farm construction, revealed a significant post-construction decline in haul-out counts. Multivariate model selection suggested that the decline was not related to the environmental factors considered, nor did it mirror wider population trends. Although cause and effect could not be unequivocally established, the theoretical basis of hearing in pinnipeds and previous studies suggested that extreme noise (to 257dB re 1μ Pa pp @ 1m) generated by pile-driving of turbine bases led to displacement of seals. A lack of full recovery of harbour seal during the study was also linked to their sensitivity to vessel activity and/or rapid colonisation of competing grey seal. Any impact of offshore wind farm development upon pinnipeds would be much reduced without pile-driving. © 2012 Elsevier Ltd. Source


Perrow M.R.,ECON Ecological Consultancy Ltd. | Skeate E.R.,ECON Ecological Consultancy Ltd. | Gilroy J.J.,ECON Ecological Consultancy Ltd.
Journal of Field Ornithology | Year: 2011

Defining the at-sea foraging movements of seabirds is fundamental to understanding their ecology and can also be important in assessing the potential impact of marine developments such as offshore wind farms (OWFs). Surveys of predefined areas using aerial or boat-based transect surveys may not allow adequate assessment of the relative importance of different areas to birds. Individual-based satellite or radio-telemetry can be effective in identifying foraging ranges and preferred areas, but may not be suitable for some species. We developed a method to determine the foraging movements of breeding terns (Sterna spp.) by visually tracking individuals using a rigid-hulled inflatable boat (RHIB). Sandwich Terns (S. sandvicensis), Common Terns (S. hirundo), and Arctic Terns (S. paradisaea) were tracked from colonies in Norfolk and Anglesey, United Kingdom, from 2006 to 2008. The proportion of complete (from and to colony) trips varied from 29-60% among species, years, and colonies. Individual Sandwich Terns were tracked for periods up to 126 min over distances up to 72 km and as far as 54 km from the breeding colony, further than Arctic (up to 57 km and 29 km from the colony) and Common (to 29 km and <9 km from the colony) terns. Mean values were much smaller. Multivariate modeling of Sandwich Tern foraging trips indicated that flight speeds >50 km/hr coupled with greater distances from shore (>25 km) significantly reduced the likelihood of tracking a bird for an entire foraging trip. Use of different boats that differ in speed and performance may alleviate such issues. Visual tracking allowed us to collect data on foraging behavior, flight height, and prey capture rates, and also permitted comparisons between species. Our results indicate that visual tracking may be an effective means of determining the foraging movements and at-sea behavior of a variety of short-ranging, day-active seabirds. © 2011 The Authors. Journal of Field Ornithology © 2011 Association of Field Ornithologists. Source


Perrow M.R.,ECON Ecological Consultancy Ltd. | Gilroy J.J.,ECON Ecological Consultancy Ltd. | Skeate E.R.,ECON Ecological Consultancy Ltd. | Tomlinson M.L.,ECON Ecological Consultancy Ltd.
Marine Pollution Bulletin | Year: 2011

Despite widespread interest in the impacts of wind farms upon birds, few researchers have examined the potential for indirect or trophic (predator-prey) effects. Using surface trawls, we monitored prey abundance before and after construction of a 30 turbine offshore wind farm sited close to an internationally important colony of Little terns. Observations confirmed that young-of-the-year clupeids dominated chick diet, which trawl samples suggested were mainly herring. Multivariate modelling indicated a significant reduction in herring abundance from 2004 onwards that could not be explained by environmental factors. Intensely noisy monopile installation during the winter spawning period was suggested to be responsible. Reduced prey abundance corresponded with a significant decline in Little tern foraging success. Unprecedented egg abandonment and lack of chick hatching tentatively suggested a colony-scale response in some years. We urge a precautionary approach to the timing and duration of pile-driving activity supported with long-term targeted monitoring of sensitive receptors. © 2011 Elsevier Ltd. Source

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