North Sea Ecology

European plaice Pleuronectes platessa often appears in ichthyological check lists for the Mediterranean Sea, as well as in regional field guides and even in some official national landings statistics. However we have not found a single ichthyologist or fisheries biologist who has actually observed this fish in the Mediterranean. The ichthyologic sources available, from classical antiquity to recent times, were checked in order to follow the track of the citations (i.e. true field observations or citations of former authors), and to try to detect misidentifications, if any. Few of these citations appear to be reliable and misidentifications with flounder Platichthys flesus are frequent. Recent scientific trawl surveys have not reported any observations of plaice. The statistics provided by France to the FAO with positive catches of P. platessa appear to be misidentifications of P. flesus. Plaice may have been present in some areas of the Mediterranean in the past, as a result of climatic changes related to the ice age. However, the species seems to be absent now. We propose that this species should be removed from the ichthyofauna records of the Mediterranean.

Spatial and temporal variations in the diet of Crangon uritai were examined using stable isotope and stomach content analyses. The sand shrimp and its potential prey were collected from Yura Estuary (3-5 m), shallow coast (5-10 m), and deep coast (30-60 m) stations of Tango Sea from April 2006 to February 2007. The measurements of the length (carapace and total lengths) and feeding habit (stomach content and stable isotope ratios) of C. uritai showed that this shrimp changed its diet during migrations between the estuary and marine environments. This species consumes a variety of food at the lower estuary: mysid Orientomysis japonica, small crustaceans particularly amphipod Melita hoshinoi, and bivalve Veremolpa micra. The abundant mysid O. japonica at the shallow coast and juveniles of unidentified bivalve species at the deep coast were the favored food throughout the year. The d 13 C and d 15 N variations in C. uritai confirmed the spatial and temporal diet shift in gut content composition as the sand shrimp grow and migrate along the estuary-marine gradient.

Estuaries are inherently open systems, linking together terrestrial, aquatic, and marine ecosystems. With fluid, permeable transitions (ecotones) marking the boundaries between these ecosystems, estuaries subsidize coastal food web productivity through the mediation of nutrient, material, and energy flux across ecosystem boundaries. Mechanisms governing the strength and scale of estuarine detritus-based food web connectivity, however, are poorly understood. For example, early estuarine descriptions suggest that extensive mixing and large-scale transport of organic matter occurs within estuarine systems, while recent evidence in estuarine detritus-based food webs has shown strong spatial gradients in the sources of organic matter assimilated by consumers across a diversity of scales. This suggests food webs are spatially compartmentalized in some estuaries, but strongly connected in others. Given that estuaries have experienced extensive structural and hydrological alterations over the past century, research describing the mechanisms of estuarine-supported subsidies is necessary if we are to provide informed guidelines for the conservation and restoration of estuaries and estuarine functions. In this dissertation, I describe the role of landscape context, consumer feeding mode, and consumer life histories in shaping the scale of food web connectivity in Pacific Northwest estuaries with implications for conservation and restoration strategies. Specifically, I examine detritus-based food webs, using multiple stable isotopes (δ 13 C, δ 15 N, δ 34 S) in combination with a Bayesian stable isotope mixing model to trace food web connections between organic matter (OM) sources and estuarine consumers. 14 web relationships at the landscape scale, especially for sedentary organisms which cannot track their food sources.

Natural mortality, due to predation, of juvenile plaice (Pleuronectes platessa) was estimated in a Scottish nursery ground (Tralee Beach) in the spring of 2009 by means of using a DNA based method (TaqMan real-time PCR based assay), targeting a plaice-specific cytochrome-b sequence, in the DNA extracted from potential predators' stomach contents. The assay was run in 1305 stomachs from a set of predators thought to be important sources of mortality of small juvenile plaice on inshore nursery grounds (including the brown shrimp, Crangon crangon, the shore crab, Carcinus maenas, and several fish species). Previous studies of predation on juvenile plaice have used visual examination of stomach contents but this is time-consuming and may underestimate true predation levels as remains may become unidentifiable due to maceration and digestion. Molecular based tools for detecting the presence of prey tissue in predator stomachs and scat are becoming increasingly used in marine ecology and provide an alternative or complementary approach to visual identification. In this sense, while 45.2 % of the brown shrimp's stomachs tested positive for plaice DNA after running the assay, only 5.7 % and 10.5 % did for, respectively, the shore crab and gobies. Results are discussed in relation to different biological and environmental variables.

Introduction 1.1 Overview 1.2 Estuaries 6.3.1 All shorebird species 6.3.2 Redshank 6.3.3 Feather, claw and soil 6.4 Discussion 6.4.1 Feathers 6.5 Conclusion Chapter 7: General Discussion 7.1 Introduction 7.2 The weighted area models 7.2.1 Proposed Improvements to the weighted area models and maps 7.2.2 Spatial analysis by distance indices (SADIE) 7.2.3 Giving dynamism to the weighted area model using cellular automata 7.2.4 Application of these weighted area models to other estuaries 7.2.5 The use of other GIS platforms 7.3 The validity of the weighted area approach in the long term: testing the long-term stability of the estuarine community at Kinneil 7.4 The further use of geostatistical methods in characterising and predicting the spatial distribution of regionalised variables. 7.4.1 Determining the optimal sampling design for mapping over-wintering shorebirds 7.4.2 The application of conditional simulation for assessing the sensitivity of inputs to models of estuarine shorebird distribution 7.4.3 Characterising spatial variation in the distribution of estuarine invertebrates: assessing the validity of scaling up count measurements 7.5 Does the carrying capacity of a site have to be reached before birds are at risk of starvation or displacement? 7.6 How important is habitat change induced prey depletion for shorebird survival? 7.6.1 Improvements for future work measuring shorebird prey depletion 7.7 The importance of determining the relative proportions of sub-populations of overwintering shorebirds. 7.7.1 Improvements and potential applications of strontium isotope ratios in bird tissue 7.7.2 The potential uses of tissues other than bone and feather in isotopic studies for tracing natal origins of birds 7.7.2.1 Eggshell

The long-tailed duck (Clangula hyemalis) is a vulnerable and declining species wintering in the Baltic Sea. The introduction of the invasive fish, the round goby (Neogobius melanostomus), dramatically impacted the benthic macrofauna in hard-bottom habitats, while no significant changes occurred in soft-bottom benthic macrofauna. Therefore, we aimed to assess the extent to which the diet of long-tailed ducks changed in two different bottom types. We analysed the stomach content of 251 long-tailed ducks bycaught in gillnets from 2016 to 2020 in hard- and soft-bottom habitats and compared these results with those published by Žydelis and Ruškyte (2005). The results show that the long-tailed duck experienced a change in diet in hard-bottom habitats, shifting from the blue mussel to Hediste diversicolor, barnacles, and fish. In soft-bottom habitats, their diet remained similar over time and was based on H. diversicolor, a few bivalve species, and Saduria entomon. There was no evidence of...

Available research is inconclusive on how circatidal habitat use and cross-shore distribution of aquatic epibenthic predators may affect the vertical zonation of infauna in muddy, soft-bottom substrates in estuaries. We placed fyke traps at different heights on the intertidal mudflat to assess the circatidal density of epibenthic predators. Infauna was sampled across the same tidal gradient. The abundance of epibenthic predators in the fykes decreased with elevation (decreasing inundation time), yet for the shrimp Palaemon longirostris abundance did not change with elevation in autumn. When corrected for inundation time, predator density was equal over the tidal range or higher on the high mudflat in some instances, indicating that predators evenly distributed over the mudflat or moved to the highest part during a high tide. The density of epibenthic predators did not correlate with the density of infauna, whereas the latter did show a close relationship with sediment characteristics. Our data suggest epibenthic predator density does not shape the present distribution of infauna across the tidal gradient on the oligohaline mudflats in the Scheldt.

Long-term trends in brown shrimp Crangon crangon abundance were studied near the entrance of the Dutch Wadden Sea using a 34 yr time series of fyke net catches. A general trend of increasing abundance was observed. In autumn, brown shrimp abundance was 5 times greater than in spring, and interannual fluctuations were also more pronounced. Biotic and abiotic conditions showed effects with time lags of up to 1 yr, which is consistent with the species' life cycle. The population responded rapidly to changes in environmental conditions: abrupt declines after adverse conditions, as in spring 1999, were followed by steep recoveries in the following autumn. Two hypotheses were tested and discussed: (1) autumn recruitment is related to predator abundance and temperature during previous warmer seasons, and (2) overwintering adult abundance is determined by predation pressure and abiotic conditions in winter. In general, predator abundance was the main factor correlated to brown shrimp abundance, especially in autumn. Multiple linear regression modelling showed that predators altogether accounted for up to 55% in spring and up to 85% in autumn of the explained variance. Previous winter conditions such as sunshine duration, salinity and fresh water discharge, and the North Atlantic Oscillation Index (NAOI) were also correlated with autumn abundance. Yet, temperature conditions during the previous growing season did not determine the autumn stock size. Winter sunshine duration and the winter NAOI were correlated with spring stock size. Additionally, temperature and salinity were relevant factors affecting abundance during spring. A significant positive relationship between spring and autumn abundance and annual commercial landings was also found.

1,2Mamun Abdullah Al*, 2Md. Didarul Alam, 2Aysha Akhtar, 3Abu Hena Mustafa Kamal, 2Md. Shafiqul Islam, Md. Wahidul Alam, Rahman Muhammed Forruq, M Muslem Uddin & Henglong Xu 1Laboratory of Microbial Ecology, Ocean University of China, Qingdao 266003, China 2Faculty of Marine Sciences and Fisheries, University of Chittagong, Chittagong-4331, Bangladesh 3Department of Animal Science and Fishery, Faculty of Agriculture and Food Sciences, Universiti Putra Malaysia Campus Bintulu Sarawak, 97008 Bintulu, Sarawak, Malaysia *[Email: [email protected]]

On six 400 m 2 plots over 3 years, we excluded the sessile subduction and conveyer-belt feeding polychaete Arenicola marina which generates a pit-and-mound topography at the sediment surface from intertidal sands near the island of Sylt, Germany. This experiment was used to test whether other abundant deposit feeding polychaetes (the discretely motile and surface feeding ragworm Nereis diversicolor and the subsurface-feeding, motile orbiniid polychaete Scoloplos cf. armiger) benefit from competitive release. Ragworms took advantage from the absence of lugworms. Presumably they responded to a more stable and nutritious surface layer at lugworm exclusion plots (relief from inhibitive bioturbation). Contrary to this, S. cf. armiger was negatively affected by the exclusion of A. marina. It may have suffered from higher sulfide concentrations in the less irrigated and less permeable sediment where lugworms were absent. For adult worms of both species these results were consistent in 2 out of 3 years examined. Recruitment by N. diversicolor was highly variable between years and occurred either irrespective of experimental treatments or the response was inconsistent. Juveniles of S. cf. armiger benefited from the presence of A. marina and aggregated near lugworm tail shafts where inflow of oxygen rich water was high and sulfide concentrations were low. Biogenic habitat mediated effects of lugworms on both deposit feeders were in the same order of magnitude as abundance variation in space and time. Thus, A. marina was one of the key factors structuring the deposit feeding community. It is suggested that arenicolids modify the composition of the associated polychaete assemblage primarily through habitat transformation.

The lack of a common statistical approach describing the distribution and dispersion pattern of marine benthic animals has often hampered the comparability among studies. The purpose of this study is therefore to apply an alternative approach, Taylor's power law, to data on spatial and temporal distribution of 9 dominating benthic invertebrate species from two study areas, the estuaries Odense Fjord and Roskilde Fjord, Denmark. The slope (b) obtained from the power relationship of sample variance (s 2) versus mean (μ) appears to be species-specific and independent of location and time. It ranges from a low of~1 for large-bodied (> 1 mg AFDW) species (e.g. Marenzelleria viridis, Nereis diversicolor) to a high of 1.6-1.9 for small-bodied (b1 mg AFDW) species (e.g. Pygospio elegans and Tubificoides benedii). Accordingly, b is apparently a valuable species-specific dispersion index based on biological factors such as behavior and intraspecific interactions. Thus, at the examined spatial scale, the more intense intraspecific interactions (e.g. territoriality) cause less aggregated distribution patterns among large-than small-bodied invertebrates. The species-specific interactions seem sufficiently strong to override environmental influences (e.g. water depth and sediment type). The strong linear relationship between the slope b and intercept log(a) from the power relationship is remarkably similar for all surveys providing a common slope of −1.63 with the present sampling approach. We suggest that this relationship is an inherent characteristic of Taylor's power law, and that b as a dispersion index may be biased by e.g. sampling errors when this relationship is weak. The correlation strength between b and log(a) could therefore be envisioned as a data quality check.

The present paper examined the possible impact of macroalgal blooms, among other influential factors, on prey abundance and availability to waders, assessing the consequences for feeding behaviour and for the specific patterns of use of the intertidal areas by these birds when macroalgal mats become dense and contiguous covering large areas of the Mondego estuary (west Portugal). Three representative microhabitats were chosen in intertidal flats to control and evaluate the effects of various factors on waders. This study shows that foraging waders did not seem to be indifferent to the effects of some biological factors, sediment characteristics and epistructures when selecting feeding microhabitats. Overall, the results suggest that the predominant and constant negative effects on specific patterns of use of the intertidal sub-areas by the majority of waders were determined by two main factors: gull perturbation and macroalgal biomass. The macroalgal blooms assumed, by their persistence over a period of several months, a different magnitude of effect when compared with sporadic factors such as gull presence. Contrary to the effects on distribution, macroalgal blooms do not influence negatively the feeding behaviour parameters considered. Moreover, we were unable to prove that the presence of macroalgae on the sediment was pernicious to the wader prey organisms, perhaps because the total amount of the area of the estuary affected by weed during the study period never exceeded 36 % and was surrounded by important algal-free areas that ensured a healthy prey population. Nevertheless, on the long-term, an increase of dense and contiguous macroalgal mats due to the progressive eutrophication of the Mondego estuary, covering large areas of the intertidal flats, may affect directly or indirectly all wader species. © 1999 Éditions scientifiques et médicales Elsevier SAS Shorebirds / waders (Charadrii) / eutrophication / foraging behaviour / zoobenthos

Predators are thought to play prominent roles in determining population abundance and dynamics of many species, but it is often difficult to document effects of predators in the held. For lack of any other effective means of manipulating predator densities, many studies use predator exclosures, however, the results of these studies are difficult to interpret because the exclosures may introduce artifacts that cannot be separated from predatory effects. Using a design common in tests of predatory effects, exclosure cages (-predators), "cage controls" = partial cages (+ predators), and no cages (+ predators), patterns of survival were found for two reef fishes that were consistent with both predator and cage effects. To separate cage artifacts from effects of predators, direct tests of cage effects in an environment free of predators were conducted, within a large predator exclosure. Cage artifacts had dramatic effects on one fish species but not the other. Moreover, the way the affected species responded to cages was exactly what would be expected if predators had strong negative effects on these fish: growth and survivorship were much lower on uncaged reefs than on caged reefs. To circumvent the cage effects, rather than compare uncaged reefs (+ predators) to reefs in exclosure cages (-predators), exclosures were compared to partial cages (+ predators). In the absence of predators, the partial cages did not differ from exclosure cages in their effects on the prey. Using the partial cages and exclosure cages in an area where predators were present, predator effects on the two fishes were tested. Survivorship of one species was greatly reduced by predators, but the other species was not affected. The lack of a predator effect on the one species was apparently an artifact of comparing completely caged reefs to partially caged reefs; another experiment documented strong predator effects on this species. Partial cages probably greatly reduced the ability of predators to consume the "unaffected" species. When cage artifacts affect prey, partial cages may be usefully employed to avoid confounding predator effects with cage effects at the cost of underestimating the magnitude ol predator effects. Direct tests of cage effects are necessary to interpret the results of any study that uses cages to test for predatory effects.

A field experiment was performed between February and May 2002 to evaluate the predation effects of migratory shorebirds on the macrofauna structure at an intertidal mudflat of the estuarine region of the Patos Lagoon. Predators were excluded by use of the metallic cages (20 x 20 x 30 cm). The macrofauna densities in shorebird exclusion treatments were always lower or equal to controls, indicating a no significant predation effect. The lower macrofauna densities in shorebird exclusion cages were probably associated to crab intrusion, which had been benefited by protection of this treatment. The low shorebird predation effects observed in this study can be related to biological characteristics of these predators associated to the local environmental conditions during the realization of these experiments.

Coastal habitats provide many important ecosystem services. The substantial role of shellfish in delivering ecosystem services is increasingly recognised, usually with a focus on cultured species, but wild-harvested bivalve species have largely been ignored. This study aimed to collate evidence and data to demonstrate the substantial role played by Europe's main wild-harvested bivalve species, the common cockle Cerastoderma edule, and to assess the ecosystem services that cockles provide. Data and information are synthesised from five countries along the Atlantic European coast with a long history of cockle fisheries. The cockle helps to modify habitat and support biodiversity, and plays a key role in the supporting services on which many of the other services depend. As well as providing food for people, cockles remove nitrogen, phosphorus and carbon from the marine environment, and have a strong cultural influence in these countries along the Atlantic coast. Preliminary economic valuation of some of these services in a European context is provided, and key knowledge gaps identified. It is concluded that the cockle has the potential to become (i) an important focus of conservation and improved sustainable management practices in coastal areas and communities, and (ii) a suitable model species to study the integration of cultural ecosystem services within the broader application of 'ecosystem services'.

Evaluations of the functioning of benthic marine food webs could be improved by quantifying organic matter fluxes from the meiofauna to higher trophic levels. In this study, we measured the simultaneous ingestion of meiofauna and macrofauna by common dwellers of a tropical intertidal mudflat on the coast of Amazonia. The meiofauna and macrofauna (tanaid) communities of a tropical intertidal mudflat of French Guiana were separately enriched with 15 N and 13 C, respectively. The enriched preys were then used as tracers during feeding experiments with common predators of different sizes and feeding mechanisms: a Portunidae crab (Callinectes bocourti), a Penaeidae shrimp (Farfantepenaeus subtilis) and a Gobiidae fish (Gobionellus oceanicus). In feeding experiments with all predators except crabs, feeding rates increased with the availability of meiofauna and macrofauna food sources. The ability of consumers to ingest their food selectively was evaluated by calculating the differences in the ratio of macrofauna to meiofauna between the i) ingested material and ii) that available in the environment. Larger predators showed a higher degree of preferential macrofauna ingestion than smaller predators, consistent with the optimal foraging theory. For large predators, the meiofauna would be important only during early life or in the absence of large food items.

The present work aims to assess the importance of settlement ponds (SP) in semi-intensive fish farms by studying benthic dynamics in an aquaculture fish farm, more specifically in the water reservoir (WR) and SP and also in production (P) and nonproduction (C) ponds during a 16-month period. In Portugal, a SP is only mandatory for intensive fish farms, and another objective of the present study is to assess the importance of these areas in semi-intensive fish farms. The WR was the area with highest diversity and evenness, as well as the higher number of exclusive taxa and taxa sensitive to organic enrichment. P and SP samples showed signs of higher disturbance levels, emphasized namely by the association of the opportunistic annelids Capitella spp. and Tubificidae. However, the benthic data from SP points to lower disturbance levels than P both due to an increase in the percentage of sensitive taxa observed in June and October 2004 and by the association of this latter sample with water reservoir samples as evidenced by canonical correspondence analysis. Moreover, a higher and increasing number of taxa when compared with the P area were also observed. Therefore, in semi-intensive fish farms, where effluents from P ponds are directly discharged to the lagoon, the potential environmental impacts would be more severe. In conclusion, the imposition of SP in semi-intensive fish farms should be considered, especially because most fish farms are located within relevant wetland areas.

The relationship between foraging shorebirds, macrobenthos and sedimentary parameters has been widely studied across Western Europe. Megatidal areas have large zones uncovered when the water retreats. Consequently, in such cases, the tide also influences foraging activities. This paper examines the use of an intertidal space by waders to define how macrobenthic resource concentrates foraging activity of birds in a large megatidal sandflat. This approach combines accurate spatial distribution of waders (Oystercatcher, Eurasian curlew, Bar-tailed Godwit and Redknot) according to their activity with ecological/biological parameters. A differential exploitation of the flat is clearly shown, with macrobenthic biomass appearing as one of the main explanatory factor for the four species considered on the western part of the bay and altitude (shore elevation) in the eastern part. The novelty of this study relates to the large area, also presumed to be a functional unit, while considering at the same time the singularities of the different parts of the flat. This multi-scale approach identifies important factors influencing the differential distribution patterns observed. The different selected parameters present an important variability in their contribution, underlining the complexity of explaining the distribution of foraging birds. Consequently, the study of such complex phenomena needs to consider additional variables to improve the relevance of explanatory models. Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.

The aim of this study was to determine the influence of temperature increase combined to conditions of light incidence on functional response of Heleobia australis. Experiments were conducted using nine to ten food concentrations for each treatment: 20°C without light; 30°C without light and, 30°C under low light intensity. For each experiment, the functional response type III (sigmoidal) was fitted and equation parameters were determined. Results suggest that, if the sediment temperature increases, H. australis will not have its ingestion rates affected negatively, whilst its feeding behavior seems to be negatively affected by light. Ingestion rates estimated for organic content in the Guanabara Bay were: 0.34 μgC ind-1 h-1 at 20°C without light, 1.44 μgC ind-1 h-1 at 30°C without light and 0.64 μgC ind-1 h-1 at 30°C under light incidence. Higher ingestion rates were estimated at the high temperature, even under light incidence, and temperature seems to have outweighed the light effect. In contrast, if higher carbon content is considered, despite high temperature, the experiment conducted with light incidence showed lower ingestion rates than those from the experiment at 20°C without light. This study provides the first quantification of H. australis ingestion rates and the effects that changes in temperature and light have on its feeding behavior.

Community structure of the macroinfauna in the sediments below an intertidal mussel bed (Mytilus chilensis (Hupe)) of southern Chile Estructura comunitaria de la macroinfauna en los sedimentos bajo un banco intermareal de bivalvos (Mytilus chilensis (Hupe)) en el sur de Chile

The principal objective of the present study was to determine the positive effects of artificial illumination on the juvenile black rockfish Sebastes inermis by comparing stomach contents and growth between juveniles exposed to light and those maintained in the absence of light. The major prey items of juvenile black rockfish in illuminated cages were: copepods (%IRI = 62.6); amphipods (%IRI = 36.7); and polychaetes (%IRI = 0.3), whereas those in unilluminated cages were: copepods (%IRI = 93.3); amphipods (%IRI = 6.1); and polychaetes (%IRI = 0.4). The specific growth rates of the juveniles reared in illuminated cages (0.67%) were significantly higher than those juveniles maintained in the unilluminated cages (0.27%).

The impact of predators is often relative to the spatial scale at which the study is conducted. In this paper we investigated how spatial scale might influence the importance of predation. In doing this we addressed the hypothesis of scale-dependency in predation experiments. The predator studied was the shore crab, Carcinus maenas (L.), and its impact on intertidal macrofauna communities was assessed using a caging experiment. Two different treatments, small and large 2 enclosure cages (of, respectively, 0.25 and 1 m), were established in a completely randomised design on two different sites, mud and muddy sand, which differed physically but were very similar biologically. The density of crabs per square metre was 48, much larger than the ambient density but comparable with previously published work. The experiment ran for a month and the resulting data and summary statistics were analysed using univariate and multivariate methods. Results indicate that the impacts of crab predation were similar in the different cage sizes but different on the different sites. The present work demonstrates the importance of scale in interpreting the results of caging experiments, but not at the small-scale level of cage size.

Expansion of the shellfish aquaculture industry has the potential to affect the structure and dynamics of coastal estuarine foodwebs. To better understand foodweb trade-offs, we incorporated both trophic and non-trophic interactions (e.g. habitat facilitation and predator refuge) into a foodweb model of central Puget Sound to predict the effects of an increase in geoduck (Panopea generosa) aquaculture. At a basin scale, the foodweb can support at least 120% increased geoduck aquaculture, above current production levels (landings of 10 546 kg in 2012), with only minor changes in individual species' biomass and/or metrics of ecosystem resilience. The non-trophic effects of increased geoduck aquaculture, related to the influence of anti-predator structure, had a stronger influence on the foodweb than the trophic role of cultured geoducks as filterfeeders and prey to other species. Increased geoduck culture caused substantial increases in biomass densities of surfperch, nearshore demersal fish, and small crabs, and decreases in seabirds, flatfish, and certain invertebrates (e.g. predatory gastropods and small crustaceans). This study identifies species that should be a priority for additional empirical research and monitoring related to bivalve aquaculture interactions, including demersal fish, small crustaceans, and seabirds. It also provides insights into the benefits and challenges of incorporating habitat-related data into a foodweb model. Understanding these relationships can inform management decisions by clarifying trade-offs in ecosystem functions and services in Puget Sound and facilitates estimation of direct and cumulative effects of bivalve aquaculture at a foodweb scale.

Highlights ►We have demonstrated the adaptation of foraging Red Knots in a megatidal environment. ►The use of prey items differs significantly during the tidal cycle depending on benthic assemblages. ►We identified a new, significant prey for the Red Knot, Donax vittatus. ►This paper suggests that a waders' diet study should include all benthic assemblages used by birds.

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In ecological studies, especially in those dealing with energy circulation in nature, determinations of the energy content of organisms are inevitable. Energy determinations are, however, laborious and time-consuming. Average conversion factors based on different species form various areas and seasons may often be a shortcut for overcoming this problem. To establish general energy conversion factors for aquatic invertebrate groups, we used 376 values of J. mg-' DW and 255 values of J. mg-' AFDW, representing 308 and 229 species, respectively. The dry-weight-to-energy factors were highly variable both within and between taxonomic groups, e.g.: Porifera, 6.1 J. mg-' DW; insect larvae, 22.4 J * mg-' DW (median values). The energy-conversion factors related to AFDW showed a much smaller dispersion with a minimum median value of 19.7 J * mg-' AFDW (Ascidiacea) and a maximum of 23.8 J. mg-' AFDW (insect larvae). Within taxonomic groups, the 95% confidence intervals (AFDW) were only a few percent of the median values. The use of energy-conversion factors based on AFDW is preferable due to their lower dispersion. For aquatic macrobenthic invertebrates, a general conversion factor of 23 J. mg-' AFDW can be used.

The effects of biological disturbance caused by the lugworm Arenicola marina (L.) on the abundance of the macrobenthic fauna were investigated at three subtidal stations (0.5 m, 12 m and 19 m water depth) in Kiel Bay (western Balticj and on an intertidal flat in the German Wadden Sea. Different effects of biological disturbance were observed (1) between funnel and cast of the lugworm burrow, (2) among stations, (3) between seasons, and (4) among taxa and groups of different living mode of the macrofauna. The strength of the impact of A. marina on the abundance of a certain macrobenthic species depends on three factors: (1) species behaviour and living mode, (2) A. marina activity, and (3) hydrodynamic conditions. In general, the most distinct effects were observed at the intertidal station during summer, followed by the two deeper subtidal stations. At the very shallow station, only weak effects were detected. AWI Publication No. 412.

No published information is available on the foraging ecology and choice of feeding habitat of New Zealand's rarest breeding bird: the New Zealand Fairy Tern (NZFT) Sternula nereis davisae. To address this gap, we conducted an assessment of the largest remaining breeding population at Mangawhai Harbour, Northland, New Zealand, during the chick-rearing period of the 2010/2011 breeding season. We combined visual tracking of birds with prey surveys and stable isotope analyses, and we present the first quantitative assessment of NZFT foraging. We recorded 405 foraging dives that show NZFT foraging habitat includes the water edges, shallow channels, and pools on the tidal flats of mangrove-lined (Avicennia marina var. resinifera) parts of the estuary; tidal pools on mud-and sandflats in the mid-estuary and lower harbour; the shallow margins of the dredged main channel in the lower harbour; the oxbow lagoons on the sand spit; and coastal shallows. Our study identifies the mangrove-lined highly tidal and shallow mid-estuary and the lagoon on the sand spit as foraging hotspots for the Mangawhai breeding population of the NZFT. The prey survey employed a seine-net sampling method at identified NZFT foraging sites and yielded 4,367 prey-sized fish of 11 species, two of which had not previously been reported in Mangawhai Harbour, as well as numerous shrimps. The most abundant fish were gobies of the genus Favonigobius. Our stable isotope results highlight gobies as the most important prey for NZFT chick rearing, also indicating that flounder Rhombosolea sp. contribute to NZFT diet. We raise the possibility that shrimps may also constitute a substantial diet component for NZFT, potentially providing up to 21% of diet mass for adult birds. While our results provide a first basis to understanding the feeding ecology of NZFT during their breeding season in order to facilitate conservation planning, further research is required to address inter-annual variation and to identify key foraging grounds for this Critically Endangered bird at other breeding sites.

Background. Organism biomass is one of the most important variables in ecological studies, making estimations of organism weight one of the most common laboratory tasks. Biomass of small macroinvertebrates is usually estimated as dry (DW) or ash-free dry weight (AFDW); a laborious and time consuming process, that often can be speeded up using easily measured and reliable proxy variables like wet/fresh weight and/or body size. Another common way of estimating AFDW - which is the most accurate but also time-consuming estimate of biologically active tissue weight - is the use of AFDW/DW ratios or conversion factors. So far, however, these ratios typically ignore the possibility that the relative weight of biologically active vs. non-active support tissue (e.g. protective exoskeleton or shell) - and therefore, also the AFDW/DW ratio - may change with body size, as previously shown for taxa like spiders, vertebrates and trees. Methods. We collected samples of aquatic, epibenthic macroinv...

Background Organism biomass is one of the most important variables in ecological studies, making biomass estimations one of the most common laboratory tasks. Biomass of small macroinvertebrates is usually estimated as dry mass or ash-free dry mass (hereafter ‘DM’ vs. ‘AFDM’) per sample; a laborious and time consuming process, that often can be speeded up using easily measured and reliable proxy variables like body size or wet (fresh) mass. Another common way of estimating AFDM (one of the most accurate but also time-consuming estimates of biologically active tissue mass) is the use of AFDM/DM ratios as conversion factors. So far, however, these ratios typically ignore the possibility that the relative mass of biologically active vs. non-active support tissue (e.g., protective exoskeleton or shell)—and therefore, also AFDM/DM ratios—may change with body size, as previously shown for taxa like spiders, vertebrates and trees. Methods We collected aquatic, epibenthic macroinvertebrates ...

Observations were made of the location and duration of foraging by five species of shorebirds in relation to the tubes of Diopatra cuprea (Polychaeta). Infaunal abundances in sites with D. cuprea tubes exceeded those in surrounding tubefree areas (120 individuals vs 29 individuals per 0.01 rn2, respectively). Of 112 shorebird foraging episodes observed only 4 were in the vicinity of D. cuprea tubes. Despite a greater abundance of prey items around worm tubes, shorebirds avoided feeding in such areas. D. cuprea tubes appear to provide an effective refuge for macrofauna from shorebird predation.

Epibenthic communities and their diets, at Culbin Sands (a cold-temperate coastal lagoon in the Moray Firth, northeastern Scotland), were sampled every 2-4 wks for 3 yrs (1994-1996). These communities were more abundant and diverse in warmer months, especially in less-exposed areas of the lagoon. The most common species were the brown shrimp Crangon crangon, the shore crab Carcinus maenas, and teleost fish (sandeel Ammodytes tobianus, sticklebacks Gasterosteus aculeatus and Spinachia spinachia, seascorpion Myoxocephalus scorpius, gobies Pomatoschistus microps and Pomatoschistus minutus, flounder Platichthys flesus, and plaice Pleuronectes platessa). Diets of these epibenthic predators included benthic infauna (especially polychaetes Eteone longa, Pygospio elegans, and Fabricia sabella; oligochaetes Tubificoides benedini; isopods Eurydice pulchra; and bivalves Cerastoderma edule and Macoma balthica), small epibenthic organisms (amphipods especially Bathyporeia pilosa and Gammarus sp....

The aim of this study was to determine the influence of temperature increase combined to conditions of light incidence on functional response of Heleobia australis. Experiments were conducted using nine to ten food concentrations for each treatment: 20°C without light; 30°C without light and, 30°C under low light intensity. For each experiment, the functional response type III (sigmoidal) was fitted and equation parameters were determined. Results suggest that, if the sediment temperature increases, H. australis will not have its ingestion rates affected negatively, whilst its feeding behavior seems to be negatively affected by light. Ingestion rates estimated for organic content in the Guanabara Bay were: 0.34 μgC ind-1 h-1 at 20°C without light, 1.44 μgC ind-1 h-1 at 30°C without light and 0.64 μgC ind-1 h-1 at 30°C under light incidence. Higher ingestion rates were estimated at the high temperature, even under light incidence, and temperature seems to have outweighed the light effect. In contrast, if higher carbon content is considered, despite high temperature, the experiment conducted with light incidence showed lower ingestion rates than those from the experiment at 20°C without light. This study provides the first quantification of H. australis ingestion rates and the effects that changes in temperature and light have on its feeding behavior.

Recent somatic growth of juvenile fringed flounder (Etropus crossotus) collected in North Inlet (South Carolina, USA) was determined based on the width of the 24 most recently deposited daily increments in sagittal otoliths. Growth rates were estimated using previously published data on the experimentally validated relationship between the daily increment width and the somatic growth. A comparison of the realised growth with experimental data indicated that growth rates in the field were near optimum values determined under ad libitum food conditions. Gut contents analysis of field collected fringed flounder indicated that food consisted predominantly of zooplankton and motile epibenthic prey with calanoid copepods, in particular Pseudodiaptomus coronatus, as the most important food items. There was no clear ontogenetic shift in prey with increasing fish size. Copepods and their eggs remained a significant prey item in even the largest fish examined (>9 cm SL), while larger prey items like polychaete worms, cumaceans, bivalves, and mysids were found in the stomachs of smaller fish. The prey organisms were abundantly available during the period of highest settlement (May through September). Growth rates, biomass, consumption estimates, and prey availability in North Inlet indicated that growth of juvenile fringed flounder is not limited by food, but predominantly determined by water temperature. During the summer months temperature and food supply in North Inlet are near optimal for juvenile fringed flounder. This allows this short-lived species to grow rapidly to attain a mature size and migrate to near-shore waters to reproduce within one growing season.

Estuaries are among the most productive habitats in the world, providing important functions and goods. Among these supplies, shellfish is an important economic resource. In Portugal (southern Europe), the edible cockle (Cerastoderma edule) is a popular food item for humans, and their populations are submitted to hard harvesting pressures both by traditional methods and for recreational purposes. The population of C. edule was studied for 18 months (2005-2006) in an intertidal sand flat of the Mondego estuary (central Portugal). In the beginning of 2005, C. edule population showed high abundance and biomass. During the summer of that year, human harvesting increased considerably, resulting in significant changes in the population structure, dynamics and secondary production. An estimate on the harvest for the studied area resulted in amounts of 4 to 7 ton shell free dry weight for 3.82 ha area. As a result, adults practically disappeared, the population structure was disrupted and the production decreased to negative values due to over-harvesting.

The aim of this study was to determine the influence of temperature increase combined to conditions of light incidence on functional response of Heleobia australis. Experiments were conducted using nine to ten food concentrations for each treatment: 20°C without light; 30°C without light and, 30°C under low light intensity. For each experiment, the functional response type III (sigmoidal) was fitted and equation parameters were determined. Results suggest that, if the sediment temperature increases, H. australis will not have its ingestion rates affected negatively, whilst its feeding behavior seems to be negatively affected by light. Ingestion rates estimated for organic content in the Guanabara Bay were: 0.34 μgC ind-1 h-1 at 20°C without light, 1.44 μgC ind-1 h-1 at 30°C without light and 0.64 μgC ind-1 h-1 at 30°C under light incidence. Higher ingestion rates were estimated at the high temperature, even under light incidence, and temperature seems to have outweighed the light effect. In contrast, if higher carbon content is considered, despite high temperature, the experiment conducted with light incidence showed lower ingestion rates than those from the experiment at 20°C without light. This study provides the first quantification of H. australis ingestion rates and the effects that changes in temperature and light have on its feeding behavior.

Predation is an interaction between species that influences community organisation by the direct consumption of prey, influencing prey numbers, behaviours and traits. The intensity of predation is greatly influenced by the environment, and the physical structure of habitats may influence predation intensity by providing refuge for prey or reducing the foraging efficiency of predators. In this context, the aim of the present study is to verify the influence of predation on the richness and density patterns of crustaceans inhabiting different species of Mussismilia corals, which provide various habitat structures for the associated fauna. We conducted an exclusion experiment to include total, partial and no cage treatments. The richness and density of crustaceans differed among coral species and cage treatments, except between partial cage and no cage treatment. Mussismilia harttii showed higher richness and density in uncaged and partial cage treatments compared with M. braziliensis, which in turn showed higher values than M. hispida. These findings indicate the importance of predation in the structure of crustacean assemblage associated with Mussismilia species and that differences in the richness and abundance of associated fauna result from the different habitat structures provided by each species of Mussismilia.

The overwintering strategy is widespread among planktivorous fish from temperate to sub-polar regions, and is particularly pronounced in sandeel ecotypes. This adaptation is presumably a behavioural adaptation to strong seasonal fluctuation in prey availability, day length and temperature. Yet so far, insight into the evolutionary and ecological mechanisms involved has remained elusive. In the present study, the overwintering behaviour is considered to be a strategy requiring 2 annual decisions: When to end overwintering and when to start overwintering, which combined comprise the timing and duration of the foraging window. We present a model framework for sandeel that demonstrates how the optimal timing of the foraging window involves a trade-off between energy gain and survival probability. Physiological components of the model are based on laboratory experiments with sandeel, some of which are presented as part of this study. The major findings were that optimisation of individual fitness is strictly dependent on the temporal match between the foraging window and the peak period of the spring burst of zooplankton. In contrast, fitness is only marginally reduced in individuals that fail to optimise the foraging window in relation to the level of mortality and prey availability experienced during the zooplankton spring burst. Lastly, overwintering remained the optimal strategy, even in scenarios where winter prey abundances approached abundances near that of the peak abundance in spring.

Understanding how animals select their habitat is a fundamental issue concerning species and habitat conservation (Jonzén 2008). Shorebirds are highly dependent on a limited number of key stopover and wintering sites, and hence are particularly vulnerable to habitat loss and most populations are in serious decline worldwide (Bart et al. 2007, Nebel et al. 2008, Delany et al. 2009). Food is a primary requirement for survival and therefore, the most important determinant of habitat quality (Piersma 2006). Intertidal sand or mud flats are the main foraging areas of coastal shorebirds feeding on macrofauna and bird distributions across coastal bays have often been positively correlated with those of their benthic prey species

Spatial and temporal variations in the diet of Crangon uritai were examined using stable isotope and stomach content analyses. The sand shrimp and its potential prey were collected from Yura Estuary (3-5 m), shallow coast (5-10 m), and deep coast (30-60 m) stations of Tango Sea from April 2006 to February 2007. The measurements of the length (carapace and total lengths) and feeding habit (stomach content and stable isotope ratios) of C. uritai showed that this shrimp changed its diet during migrations between the estuary and marine environments. This species consumes a variety of food at the lower estuary: mysid Orientomysis japonica, small crustaceans particularly amphipod Melita hoshinoi, and bivalve Veremolpa micra. The abundant mysid O. japonica at the shallow coast and juveniles of unidentified bivalve species at the deep coast were the favored food throughout the year. The d 13 C and d 15 N variations in C. uritai confirmed the spatial and temporal diet shift in gut content composition as the sand shrimp grow and migrate along the estuary-marine gradient.

Pleuronectes platessa often appears in ichthyological check lists for the Mediterranean Sea, as well as in regional field guides and even in some official national landings statistics. However we have not found a single ichthyologist or fisheries biologist who has actually observed this fish in the Mediterranean. The ichthyologic sources available, from classical antiquity to recent times, were checked in order to follow the track of the citations (i.e. true field observations or citations of former authors), and to try to detect misidentifications, if any. Few of these citations appear to be reliable and misidentifications with flounder Platichthys flesus are frequent. Recent scientific trawl surveys have not reported any observations of plaice. The statistics provided by France to the FAO with positive catches of P. platessa appear to be misidentifications of P. flesus. Plaice may have been present in some areas of the Mediterranean in the past, as a result of climatic changes related to the ice age. However, the species seems to be absent now. We propose that this species should be removed from the ichthyofauna records of the Mediterranean.

The relationship between relative body condition (deviation from expected mean body weight) and burying depth was investigated in five macro-zoobenthic species living in a marine intertidal habitat. Body weight increased with depth when animals of the same size were compared. The increase amounted to 50% in the clam Scrobicularia plana, ca. 40% in the worm Nereis diversicolor, 25% in the clam Macoma balthica and 20% in the cockle Cerastoderma edule and the clam Mya arenaria. Only a part of the prey was within reach of some feeding wader species. Therefore prey value may be overestimated if one does not take into account the fact that shallow and accessible prey often have a relatively poor body condition.