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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


Lepage M.,IRSTEA | Harrison T.,17 Antrim Rd | Breine J.,Research Institute for Nature and Forest | Cabral H.,University of Lisbon | And 10 more authors.
Ecological Indicators | Year: 2016

A simple procedure to harmonise and intercalibrate eight national methods classifying the ecological status using fish in transitional waters of the North East Atlantic is described. These methods were initially intercalibrated and a new method recently developed was added to this exercise. A common human pressure index pre-classified the status of each water body in an independent way. Ecological class boundaries values were established according to the level of anthropogenic pressure using regression analyses. A simulated dataset was used to assess the level of agreement between the fish classification methods. Fleiss' multi-rater kappa analysis indicated that boundary harmonisation was achieved; all classifications fell within one class of each other and class agreement between methods exceeded 70%. The use of a pressure index to establish boundary thresholds provides a practical method of defining and harmonizing the quality classes associated with human pressures, as required by the European Water Framework Directive. © 2016 Elsevier Ltd. All rights reserved. Source


Wetzel M.A.,German Federal Institute of Hydrology BfG | Wetzel M.A.,University of Koblenz-Landau | Scholle J.,BioConsult Schuchardt and Scholle GbR | Teschke K.,Alfred Wegener Institute for Polar and Marine Research
Marine Environmental Research | Year: 2014

Artificial substrates are omnipresent today in most estuaries mostly in form of massive rip-rap used for groynes and jetties. In the Weser estuary, Germany, 60% of the shoreline is covered with such artificial substrates while, natural rocky substrate is lacking, as in all Wadden Sea estuaries. This large quantity of artificial substrates may be colonized by a benthic hard-substrate community which differs from the local natural soft-substrate assemblage. In this study we examined species compositions, abundances, biomass, and numbers of species of subtidal benthic communities on groynes and in the natural habitat, the sediment, along the salinity gradient of the Weser estuary. Species composition changed on both substrates significantly with salinity and was also significantly different between the substrates. In a comparison with the sediment, the groynes did not provide any benefit for non-indigenous nor for endangered species in terms of abundance, biomass, and number of species, but represent habitats with higher total abundances and biomass; though some non-indigenous species even occurred exclusively on groynes. In particular, groynes supported filter-feeding organisms which play an important role by linking benthic and pelagic food webs. The dominance of the suspension feeders affects crucial estuarine ecosystem services and may have important implications for the estuarine management by altering the estuarine ecological quality status. Hence, artificial substrates should be considered in future conservation planning and in ecological quality monitoring of the benthic fauna according to the European Water Framework Directive. © 2014 Elsevier Ltd. Source


Schuchardt B.,BioConsult Schuchardt and Scholle GbR | Bildstein T.,BioConsult Schuchardt and Scholle GbR | Gunther C.-P.,BioConsult Schuchardt and Scholle GbR | Scholle J.,BioConsult Schuchardt and Scholle GbR
Natur und Landschaft | Year: 2011

Maps of types of marine landscape have been drawn up on the basis of existing data for the German North Sea and Baltic Sea in accordance with international requirements within the scope of an R & D project supported by the German Federal Agency for Nature Conservation (BfN). These maps provide an overview of the ecological situation, but are not adequate for nature conservation practice. Therefore, efforts are additionally being made to determine the extent to which maps of habitat types can also be prepared on the basis of existing data. Of 70 types of habitat, only 15 can be depicted over the entire area and 13 over a restricted portion of the area. It is thus necessary to supplement an extensive compilation of existing data with targeted mapping. Furthermore, the existing habitat classification, particularly of soft soils, should be differentiated by integrating biological parameters, as has already been realized to a certain degree by means of new legally protected types of habitat. Source

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