Juvenile Plaice Research Articles

Effect of temperature on growth, expression of growth regulating genes, and deformity development of juvenile European plaice (Pleuronectes platessa)

The flatfish European plaice is a demersal, temperate species and a candidate for marine aquaculture. To better understand growth and the mechanisms involved in growth regulation, juvenile plaice (initial mean weight ± SEM, 10.4 ± 0.1 g) were reared in triplicate rearing tanks at three different temperature: ambient (average of 8.6 °C), 12 °C and 16 °C, for 100 days. Interactions between growth, expression of growth regulating genes, and skeletal development were studied to determine optimal rearing conditions for juvenile plaice. Juvenile plaice grew fastest at 16 °C, followed by the 12 °C group. The condition factor was inversely correlated to increased temperatures and was highest in the 8.6 °C group. At the start of the experiment, 11% of the fish had vertebra deformities. Increasing temperature resulted in higher frequency and severity of malformations, and the 8.6 °C group had 8% less vertebra deformities at the end of the experiment compared to other two groups. The 12 °C and 16 °C groups had similar frequency of deformed fish, however, the 16 °C had more severe deformities, measured as number of deformed vertebrae per fish. Temperature affected gene transcript levels of ghr, igf-1, and igf-1r in muscle and liver tissue differently. Hepatic igf-1 transcript levels increased with increased growth and temperature. Muscular igf-1r transcript levels increased with increasing temperature in each sampling, indicating that igf-1r corresponded with muscular growth. Based on the present findings, a rearing temperature of 12 °C is recommended for on-growing of juvenile plaice.

Spatial and temporal variability in larval connectivity of North Sea plaice Pleuronectes platessa between spawning grounds and coastal European nurseries

Annual year-class strength in North Sea plaice Pleuronectes platessa Linnaeus, 1758 appears to be determined by the connectivity of eggs and larvae between open-sea spawning grounds and coastal nursery areas. Hydrodynamic modelling studies indicate that coastal nurseries can be supplied with larvae from multiple offshore spawning locations. To verify this, we compared relative size-frequency distributions of demersal juvenile plaice just after larval immigration between coastal nurseries as a proxy for larval origin. During 12 yr, up to 21 stations in the Dutch coastal zone and international Wadden Sea were visited and sampled at the beginning of May at the end of larval immigration. The results of the size-frequency analysis showed 2 distinct clusters of stations. The first cluster included all stations along the Dutch coast and Wadden Sea up to Wangerooge in the German East Frisian Wadden Sea, most likely dominated by supply from spawning grounds in the Southern Bight, with contributions from the English Channel and the Dogger Bank. The second cluster included all stations in the North Frisian Wadden Sea, most likely supplied from spawning grounds in the German Bight and near the Dogger Bank. The higher interannual variability in the first cluster might be caused by a larger variability in the relative contributions from multiple spawning areas (English Channel, Southern Bight, Dogger Bank). The comparison of the relative size-frequency distributions at the end of larval immigration introduced in this study may also be a useful tool for the validation of connectivity modelling studies in other areas and for other species.

Changes in functioning of the largest coastal North Sea flatfish nursery, the Wadden Sea, over the past half century

The international Wadden Sea is an important flatfish nursery. Information from the Dutch Wadden Sea indicates that the flatfish nursery function of the area has been affected during the last decades. Increased seawater temperature has affected settling, habitat suitability for and growth performance of the various flatfish species. Settling of plaice, flounder and to a lesser extent sole larvae occurs earlier nowadays. In the 1960s, 0-, I-, II- and III-group plaice were present, but since 2000, II-group has disappeared and densities of I-group have decreased. For juvenile flounder, II-group almost disappeared, and for dab, a decline in densities of all age groups was observed from the 1990s onwards. Summer temperatures exceed the optimum for the cold-water species (plaice, flounder and dab) with increasing frequency, level and duration. Only for 0-group sole, the period with optimal growth conditions has become longer and has resulted in increased growth. Mortality rates in 0-group plaice have increased, coinciding with an increase in water temperatures and an increase in the abundance of predators. The decrease in density of juvenile plaice and dab in the Wadden Sea has not affected recruitment to North Sea stocks, suggesting that other areas have taken over part of the nursery function. The predicted increase in seawater temperature in the next decades will continue to improve the conditions for sole. The temperature tolerance of plaice and dab and to a lesser extent flounder will further reduce their scope for growth and may ultimately result in their disappearance from the Wadden Sea.

Juvenile fish habitat across the inner Danish waters: Using otolith chemistry to discriminate between hybridising con-familials and contiguous, coastal habitat

Connectivity between juvenile habitats and adult stocks is important for determining the resilience of local fisheries and the relative contribution of different juvenile habitat areas to adult populations. Otolith chemistry is commonly employed to differentiate between individuals from different juvenile habitat areas; whereby different environmental exposures, mediated by intrinsic physiological processes, produce different trace element concentrations in the biologically inert otolith. This study aims to determine if otolith chemistry can differentiate between juveniles of hybridising con-familials where they are found in the same habitat and to establish if otolith chemistry can effectively re-assign individuals to contiguous coastal juvenile habitat areas of the inner Danish waters (IDW). Sympatric pairs of juvenile European plaice (Pleuronectes platessa) and flounder (Platichthys flesus) caught together in a juvenile beam trawl survey, in areas where the two species hybridise, were used to address the first aim. Juvenile plaice and common sole (Solea solea) caught during the same survey were used to determine if otolith chemistry can correctly re-assign individuals back to contiguous coastal juvenile habitat areas. Laser ablation inductively coupled plasma mass spectroscopy (LA-ICPMS) was used to analyse the trace elements in edge spots of juvenile otoliths and Canonical Analysis of Principal Coordinates was employed to test the reassignment of individuals back to correct species or area. Using a suite of eight trace elements, ∼72% of individual plaice (∼70%) and flounder (∼73%) were correctly identified. Greater than two-thirds (∼67%) of plaice were correctly re-allocated to four juvenile habitat areas and close to four out of five (∼79%) individual sole were correctly re-allocated to three juvenile habitat areas. These results indicate that the hybridising con-familial plaice and flounder of the IDW warrant further attention and could be a valuable model system to assess how intrinsic and extrinsic factors influence elemental incorporation. Furthermore, this study shows otolith chemistry is a valuable tool for tracing marine fish back to juvenile habitat areas, even where they are found along contiguous coastal areas.

Changes in distributional patterns of plaice Pleuronectes platessa in the central and eastern North Sea; do declining nutrient loadings play a role?

Since the beginning of the 1990s, there has been a change in the relative distribution of smaller age-classes of plaice Pleuronectes platessa (age 1–3) in the North Sea. The abundances have increased in deeper, more offshore areas, while coastal abundances have been stagnant or declining. For the same time period available time series data on nutrient conditions in the coastal North Sea area show that the freshwater nitrogen loading has decreased by about 50%. While nutrient concentrations in the ambient environment have been shown to influence growth in juvenile plaice through influence on their prey, we here inspect the potential linkage between distributional changes in plaice and the decline in nutrient loading. We compare plaice observations in coastal areas in the eastern North Sea, which have experienced large changes in eutrophication, with observations for the Dogger Bank, a large sandbank in a shallow offshore area of the North Sea. The Dogger Bank, was used as a reference location assuming this area has been less influenced from coastal eutrophication but similar regional climate conditions, and here we found no changes in the abundances of juvenile plaice. The increase in the use of offshore habitats as nursery areas by juvenile plaice in the North Sea appears not related to water depth per se but driven by specific processes dominating in near-shore areas and may be related to changes in nutrient loadings. This point to the importance of separating more general depth-related factors from conditions specific for near-shore areas, such as nutrient loadings in coastal waters and export offshore. The concurrent changes in environment and in distribution of juvenile plaice may have implications for environmental and fisheries management.

Discriminating nursery grounds of juvenile plaice (Pleuronectes platessa) in the south-eastern Irish Sea using otolith microchemistry

Nursery grounds are valuable habitats providing sources of food and refuge during early life stages for many commercially caught marine fish. Distinguishing between different nursery grounds and identifying habitat origin using trace elemental concentrations in aragonite structures of teleost fish has proved valuable in fish ecology and fisheries. This study aimed to (1) compare chemical signatures (elemental fingerprints) within sagittal otoliths of juvenile European plaice Pleuronectes platessa sampled from known nursery habitats in the south-eastern Irish Sea and (2) assess their potential and robustness as natural tags for identifying nursery grounds for the putative south-eastern Irish Sea plaice stock. Otoliths from juvenile plaice (‘1-group’, 6 to 15 cm total length) were obtained from 8 nursery grounds in coastal areas off north-west England and north Wales (including Anglesey) between June and August 2008. Solution-based inductively coupled plasma-mass spectrometry determined the concentrations of 10 elements (Li, Na, Mg, K, Mn, Zn, Rb, Sr, Sn, Ba), with significant differences in otolith element composition observed between all nursery grounds. Cross-validation linear discriminant function analysis (CV-LDFA) classified fish to their nursery ground of capture (46.2 to 93.3%), with a total group CV-LDFA accuracy of 71.0%. CV-LDFA between regions (north-west England and north Wales) classified fish with 82% accuracy. The discrimination of juvenile plaice from all 8 nursery grounds within the south-eastern Irish Sea using otolith microchemistry offers significant opportunities in the development of future effective fisheries management strategies through understanding the supply of juveniles from specific nursery grounds and adult plaice in the south-eastern Irish Sea.

Shifts in nursery habitat utilization by 0-group plaice in the western Dutch Wadden Sea

Since the mid-1980s major changes in spatiotemporal patterns of distribution of juvenile plaice have occurred in the Wadden Sea. Large juvenile (I- and II-group) plaice have almost completely disappeared from the intertidal flats in spring and summer and are no longer found in subtidal and tidal channels in autumn, consistent with an offshore movement reported in the nearshore coastal zone. In this paper we evaluate the present functional importance of the western Wadden Sea as a nursery for young-of-the-year (0-group) plaice and the changes over time compared to the mid-1980s period by analyzing abundance, growth and distribution patterns in various intertidal, subtidal and tidal channel areas. Spatiotemporal changes in habitat use were observed compared to 1986 based on a depth-stratified sampling repeated two decades later, in 2009. Present results showed that the utilization of the western Wadden Sea has greatly changed, with changing patterns of depth distribution of the 0-group. Settlement of 0-group plaice still occurred in the intertidal, however, shortly thereafter, they moved to deeper waters. Such shift in habitat use did not seem to have affected growth rates. Overall, it seems that the western Wadden Sea can still support young-of-the-year plaice population and in spite of changes in habitat use, the functional importance of the area for this group has not been affected.

Possible causes for growth variability and summer growth reduction in juvenile plaice Pleuronectes platessa L. in the western Dutch Wadden Sea

Growth variability within individuals and among groups and locations and the phenomenon of summer growth reduction has been described for juvenile flatfish in a variety of European coastal areas whereby the underlying causes still remain elusive. Potential mechanisms were tested for juvenile plaice Pleuronectes platessa L. in the western Dutch Wadden Sea, by analysing published and unpublished information from long-term investigations (1986–present). Growth variability did occur and could be explained by differences induced by environmental variability (water temperature), and by non-genetic irreversible adaptation and sex. Dynamic Energy Budget analysis indicated that especially sexually-dimorphic growth in combination with variability in sex ratio could explain most of the variability in growth and the increase in the range of the size of individuals within the population over time. Summer growth reduction was not only observed among 0-group plaice in the intertidal, but also in the subtidal and tidal gullies as well as among I- and II-group plaice. Intraspecific competition for food was not detected but some support for interspecific competition with other predators was found. Also resource competition (due to crowding) with the other abundant epibenthic species (0-, I- and II-group flounder Platichthys flesus; the brown shrimp Crangon crangon; the shore crab Carcinus maenas; the goby species Pomatoschistus minutus and Pomatoschistus microps) could not explain the summer growth reduction. The observed growth reduction coincided with a decrease in stomach content, especially of regenerating body parts of benthic prey items. It is hypothesised that macrozoobenthos becomes less active after the spring phytoplankton bloom, reducing prey availability for juvenile plaice in summer, causing a reduction in food intake and hence in growth.

Seasonal and interannual variations of biological performances of newly settled juvenile plaice Pleuronectes platessa during the spring period on an intertidal sandy beach

Seasonal and interannual variations of biological performances of newly settled juvenile plaice Pleuronectes platessa during the spring period on an intertidal sandy beach

Early life stages of plaice Pleuronectes platessa in cold-water nurseries

Event Abstract Back to Event Early life stages of plaice Pleuronectes platessa in cold-water nurseries Filipe Martinho1*, Vânia Freitas2, 3, Paulo T. Santos4, Camila Bremm4, Joana Campos2, 3 and Henk W. Van Der Veer2 1 Centre for Functional Ecology - CFE, Department of Life Sciences, Portugal 2 NIOZ - Royal Netherlands Institute for Sea Research, Netherlands 3 CIIMAR – Interdisciplinary Centre of Marine and Environmental Research, Portugal 4 FCUP – Faculdade de Ciências da Universidade do Porto, Portugal Plaice Pleuronectes platessa (Linnaeus, 1758) is one of the most important commercial flatfish in the European continent, whose captures have reduced considerably in recent decades due to the high pressure of fisheries. Despite the wide distribution of this species, most studies have focused on the North Sea, its central area of occurrence, and very little information is available concerning the populations living at the northern limit of its distribution. Age determination is essential to study population dynamics of commercially important species such as plaice, and can be inferred through otolith microstructure analysis. The aim of this work was to investigate the timing of early life events (spawning, larval, metamorphosis and settlement stage duration) and growth of juvenile plaice in two cold-water nursery areas in northern Norway (Valosen estuary and Storfjord). A latitudinal cline was observed in the main life-history events, such as spawning, and the onset of larval and metamorphosis stages. Settlement to benthic habitats (which coincides with metamorphosis) was estimated to have occurred between mid-May and early-September (peak from the end May and mid July) in the Valosen, and between the end of May and early July (peak in June) in the Storfjord. In the Storfjord area, larval and metamorphosis stage duration seemed to be shorter, probably due to a reduced window of opportunity for growth and survival at the northernmost extremes. Size at settlement was negatively related with hatch day, implying that the older larvae were larger at settlement, a consequence of higher fecundity of females earlier in the spawning season. A significant relationship between size at settlement and total length reinforced this evidence. The results demonstrate the influence of latitude in the early life stages of plaice, mainly by the regulatory effect of temperature in the growth and survival of larvae and juveniles. Acknowledgements This study was funded by the Portuguese Foundation for Science and Technology, through the following grants, with funds from the European Social Fund and the Portuguese Operational Human Potential Program (POPH): F Martinho - Investigador FCT programme IF/01410/2012 V Freitas - Post doc grant SFRH/BPD/75858/2011 J Campos - Post doc grant SFRH/BPD/71205/2010 Keywords: latitudinal gradient, Plaice, otolith microstructure, Nursery grounds, Norway Conference: XV European Congress of Ichthyology, Porto, Portugal, 7 Sep - 11 Sep, 2015. Presentation Type: Oral Presentation Topic: Otoliths as a tool to study fish life cycles Citation: Martinho F, Freitas V, Santos PT, Bremm C, Campos J and Van Der Veer HW (2015). Early life stages of plaice Pleuronectes platessa in cold-water nurseries. Front. Mar. Sci. Conference Abstract: XV European Congress of Ichthyology. doi: 10.3389/conf.fmars.2015.03.00090 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 18 Nov 2015; Published Online: 19 Nov 2015. * Correspondence: Dr. Filipe Martinho, Centre for Functional Ecology - CFE, Department of Life Sciences, Coimbra, 3000-456, Portugal, fmartinho@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Filipe Martinho Vânia Freitas Paulo T Santos Camila Bremm Joana Campos Henk W Van Der Veer Google Filipe Martinho Vânia Freitas Paulo T Santos Camila Bremm Joana Campos Henk W Van Der Veer Google Scholar Filipe Martinho Vânia Freitas Paulo T Santos Camila Bremm Joana Campos Henk W Van Der Veer PubMed Filipe Martinho Vânia Freitas Paulo T Santos Camila Bremm Joana Campos Henk W Van Der Veer Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Smelling Danger – Alarm Cue Responses in the Polychaete Nereis (Hediste) diversicolor (Müller, 1776) to Potential Fish Predation

The harbour ragworm, Nereis (Hediste) diversicolor is a common intertidal marine polychaete that lives in burrows from which it has to partially emerge in order to forage. In doing so, it is exposed to a variety of predators. One way in which predation risk can be minimised is through chemical detection from within the relative safety of the burrows. Using CCTV and motion capture software, we show that H. diversicolor is able to detect chemical cues associated with the presence of juvenile flounder (Platichthys flesus). Number of emergences, emergence duration and distance from burrow entrance are all significantly reduced during exposure to flounder conditioned seawater and flounder mucous spiked seawater above a threshold with no evidence of behavioural habituation. Mucous from bottom-dwelling juvenile plaice (Pleuronectes platessa) and pelagic adult herring (Clupea harengus) elicit similar responses, suggesting that the behavioural reactions are species independent. The data implies that H. diversicolor must have well developed chemosensory mechanisms for predator detection and is consequently able to effectively minimize risk.

Temperature effect on growth and larval duration of plaice Pleuronectes platessa in three regions of the Northeast Atlantic

Transport models for planktonic fish eggs and larvae often use temperature to drive growth because temperature data are readily available. This pragmatic approach can be criticised as too simplistic as it ignores additional factors, such as food availability and growth-rate-depen- dent mortality. We examined the extent to which temperature could explain the larval duration and growth variability in post-settlement plaice from the southern North Sea, Irish Sea and west of Ireland. Larval duration and individual growth were estimated from the otolith microstructure of juvenile plaice collected from nursery grounds in each region, and average sea surface temper- atures were reconstructed for each region from satellite data. Hatch dates, larval duration and set- tlement dates all differed among the regions, reflecting the timing of spawning and the physical characteristics of each region. Models incorporating presumed temperature history and region explained 73% of variability in individual larval growth (as estimated from otolith microincrement widths), again demonstrating important differences among the regions. The results suggest that sea temperature can be used to drive growth models of plaice larvae, although allowance must then be made for inter-regional differences. However, larval duration can be estimated using a pan-regional model based on the average temperature experienced during the larval phase.

The role of structuring benthos for juvenile flatfish

Within coastal nurseries, the distribution of juvenile flatfish may depend on small-scale habitat variability. The presence of ecosystem engineers is known to have important impacts in coastal sediments. Lanice conchilega is a well-known marine ecosystem engineer of shallow soft bottom ecosystems, shaping the macrobenthic community and attracting flatfish. The present study examines the relation between juvenile flatfish and L. conchilega reefs through two experiments. In a field experiment in the Dutch part of the North Sea, the benthic habitat is evaluated by comparing relative differences in numbers of juvenile flatfish between ecosystem engineered habitats and adjacent bare sand (i.e. non-ecosystem engineered) habitats. The hypothetical shelter seeking behaviour was further examined using stomach content analyses. Results show that juvenile plaice Pleuronectes platessa was the dominant species within the tube worm habitat and the species selects specifically for this biogenic habitat. This selection was explained as feeding behaviour. In a complementary laboratory study, food was excluded and the shelter function of the ecosystem engineered habitat was investigated. This experiment quantifies the selection for this habitat by juveniles of the common sole Solea solea. Results from the flume experiment, manipulating the number of tube worms, show that distribution of sole was not random when current velocities are high. The selected habitat is the one with low density tube worm aggregations. Overall, we conclude that structuring benthos plays an important role for juvenile flatfish, both as refuge and as feeding ground.

Estimating spatial and temporal variability of juvenile North Sea plaice from opportunistic data

Surveys are often insufficient to accurately capture the distribution of a species in both space and time. Complementary to the use of research vessel data, platforms of opportunity can be a powerful strategy to monitor species distributions at high temporal and spatial resolution.In this study we use data from commercial fishing vessels, collecting – under the European Union data collection framework – biological data on all species that are caught and subsequently discarded. Using such discard data in combination with a systematic trawl survey, we model the spatial and temporal distribution of juvenile plaice (Pleuronectes platessa) in the central North Sea. There is a clear age-dependent difference between the commercial fishing vessel data and the research vessel data, with age 1 being the dominating age in the survey catches, while age 2 is the dominating age in the discards. The results show how immature plaice, slowly migrate from the nursery areas, westwards into the deeper regions of the North Sea. Also, the results show that during the study period, juvenile plaice gradually moved to deeper waters at an earlier age. Finally we discuss how the framework can be applied to similar opportunistic data to monitor seasonal and inter-annual migration of marine organisms, and to quantify how they may be influenced by biotic and abiotic gradients, such as temperature.

Otolith oxygen and carbon stable isotopes in wild and laboratory-reared plaice (Pleuronectes platessa)

The relationship between water temperature, growth rate, and otolith isotopic ratios was measured for juvenile plaice (Pleuronectes platessa) reared at two temperatures (11 and 17°C) and two feeding regimes (1 and 3 prey items·ml−1). The otolith isotope ratios in individual fish ranged from −2 to −4 for carbon isotope ratios (δ13C) and from 0.2 to 1.9 for oxygen isotope ratios (δ18O). The otolith oxygen isotope ratios were significantly affected by water temperature, but not by feeding level, and there were no significant synergistic effects. The fractionation of oxygen isotopes during otolith growth was independent of individual growth rate. Carbon isotope ratios were not significantly affected by food ration or water temperature, but were related to fish growth rate. The carbon isotope ratios were negatively correlated with fish length in the colder water treatments, and tended to increase with fish length in the warm water treatments. The laboratory-determined relationship between otolith oxygen isotope ratio and water temperature was applied to individuals of five species (plaice, cod, whiting, haddock, gurnard) collected in a single trawl sample. The otolith derived temperatures often overestimated measured water temperatures. The difference between real and estimated water temperatures varied between species, and the closest fit was for field-caught plaice.

Effect of starvation on condition and growth of juvenile plaice Pleuronectes platessa: nursery habitat quality assessment during the settlement period

In order to assess the effect of feeding deprivation on growth and condition of field-caught newly settled juvenile plaice Pleuronectes platessa, a 3 week starvation experiment was conducted and changes in RNA/DNA ratio, Fulton's K condition index and recent otolith growth were measured. Fed ad libitum and starved fish were analysed after 0, 1, 2, 3, 4, 5, 7, 9, 14, 16 and 22 days of starvation. In parallel, field newly settled juvenile plaice were collected weekly over the settlement period (between April and May 2005) in the adjacent intertidal zone of the Canche estuary (eastern English Channel, France) and fish performances were estimated. After starvation day 4, Fulton's K condition index and RNA/DNA ratio of juvenile plaice significantly differed between treatments while recent otolith growth differed between treatments after day 9 of the experiment procedure. Results indicate that the three biological parameters are sensitive indices and can be used to accurately assess nutritional condition of wild juvenile fish. Values of 0.32 for RNA/DNA, 0.83 mg. mm−3 for Fulton's K index, and 3.99 µm for recent otolith daily growth were defined as critical threshold values below which juvenile plaice can be classified as ‘starving'. When comparing these experimental values with those from field-caught newly settled juvenile plaice, less than 1% of wild individuals can be classified as ‘starving' whatever the index. Our results suggest that feeding conditions throughout the settlement period on the Canche intertidal nursery ground are favourable to juvenile plaice development and survival, and hence to the recruitment success.

Trophic ecology of juvenile flatfish in a coastal nursery ground: contributions of intertidal primary production and freshwater particulate organic matter

Coastal and estuarine nurseries are essential habitats for juvenile flatfish. These small but productive areas provide food supply and sustain adult fish populations. The Mont-Saint-Michel Bay (MSMB) supports an important flatfish nursery ground but differs from many other nursery habitats due to limited freshwater inputs. The objectives of the present study in the MSMB were to (1) use gut content analysis to identify prey of the 2 most abundant flatfish species (common sole Solea solea and plaice Pleuronectes platessa) for different juvenile age-classes (0-group and 1-group for sole, 0-group for plaice), (2) use C and N stable isotope analysis to model the production sources sustaining juvenile flatfish production, and (3) compare these results with previous knowledge of estuarine nursery grounds located in western Europe. Items found in gut contents differed between species and size classes, with juvenile plaice having a larger prey spectrum. Despite accounting for sensitivity to large uncertainties in source signatures and trophic enrichment factors, stable isotope mixing models led to robust outputs. In contrast to previous studies in estuarine nurseries, we found that microphytobenthos was the major carbon source contribution to juvenile flatfish. The contribution of freshwater particulate organic matter was nonetheless significant, in spite of the very limited river inputs to MSMB.

Dependence of RNA:DNA ratios and Fulton’s K condition indices on environmental characteristics of plaice and dab nursery grounds

Abstract This field study showed a lack of a correlation between a morphometric (Fulton’s K ) and biochemical (RNA:DNA ratio) condition index in juvenile plaice ( Pleuronectes platessa ) and dab ( Limanda limanda ) studied to assess habitat quality in four sandy beach nursery grounds in Galway Bay, Ireland. Based on monthly surveys from June to September in 2008 and 2009, fish growth, indicated by RNA:DNA ratios and Fulton’s K , displayed considerable spatio-temporal variability. Site-related patterns in Fulton’s K for plaice and dab were consistent between years whereas RNA:DNA ratios displayed annual and interspecific variability among nursery habitats. This indicates a higher sensitivity of RNA:DNA ratios to short-term environmental fluctuations which is not apparent in Fulton’s K measurements of juvenile flatfish. Generalized Additive Modelling (GAM) revealed non-linear relationships between the condition indices and (biotic and abiotic) habitat characteristics as well as diet features, derived from gut content analyses. Density of predators, sediment grain size and salinity were the most important predictors of both condition indices. Temperature also affected condition indices in dab whereas plaice condition indices varied with depth. Diet features did not contribute to the explained variability in the models predicting RNA:DNA ratios whereas certain prey groups significantly improved the explained variability in the models predicting Fulton’s K of plaice and dab. The value of both indices for assessing fish condition and habitat quality in field studies is discussed. These findings aid understanding of the biological and physical mechanisms promoting fast growth and high survival which will help to identify high quality nursery areas for juvenile plaice and dab.

Variability in the early life stages of juvenile plaice (Pleuronectes platessa) on west of Ireland nursery grounds: 2000–2007

Plaice (Pleuronectes platessa) are the most abundant juvenile flatfish present on west of Ireland nursery grounds. 0-group plaice were collected from eleven sandy beach nursery areas along the west coast of Ireland by beach seining (2000–2007). In the majority of years examined, certain beaches were found to support a higher abundance of juvenile plaice, or individuals that were larger in size and exhibited good condition, suggesting that differences in habitat quality exist between beaches. Monthly mean densities of plaice ranged from 2.4 (± 2.4) to 100 (± 1.3) individuals 1000 m−2. Mean lengths of plaice ranged between 6.0 (± 1.0) and 10.1 (± 0.5) cm. No evidence of density dependent growth was detected over the eight years of the study. The length and condition of juvenile plaice also differed between hauls, indicating the existence of microhabitat effects and emphasizing the importance of selecting an appropriate spatial resolution to adequately assess an area. Similar to other locations in Europe, juvenile plaice abundances on nursery grounds were inversely related to mean spring seawater temperatures during the pelagic stage. Abundances of 0-group plaice were not related to the number of either 1- or 2-group individuals collected during bottom-trawl surveys off the Irish west coast, demonstrating the difficulties associated with developing a recruitment index for plaice.

Field experiments on depth selection by juvenile plaice Pleuronectes platessa

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 430:197-205 (2011) - DOI: https://doi.org/10.3354/meps09034 Field experiments on depth selection by juvenile plaice Pleuronectes platessa R. N. Gibson, M. T. Burrows*, L. Robb Scottish Association for Marine Science, Scottish Marine Institute, Oban PA37 1QA, UK *Corresponding author. Email: mtb@sams.ac.uk ABSTRACT: After settlement on sandy beaches in spring, juvenile (0-group) plaice Pleuronectes platessa L. spend the summer and autumn months at depths <5 m. During this time, there is a strong length–depth relationship in which the smaller fish are most common at the shallow end of their depth range. Mark and recapture experiments with fish caught at depths of 0.5 and 2.5 m demonstrated that nearly all fish subsequently released at their depth of capture stayed at that depth, and few moved to other depths. In contrast, many fish reciprocally transplanted between these depths returned to their depth of capture within 2 d, and very few remained at the transplant depth. The results indicate that juvenile plaice have a fidelity to, and can actively select, a particular depth, although there may be some movement between depths, most of which at the time of the experiment (August/September) was directed offshore. KEY WORDS: Plaice · Pleuronectes platessa · Depth distribution · Depth fidelity · Homing · Habitat selection Full text in pdf format PreviousNextCite this article as: Gibson RN, Burrows MT, Robb L (2011) Field experiments on depth selection by juvenile plaice Pleuronectes platessa. Mar Ecol Prog Ser 430:197-205. https://doi.org/10.3354/meps09034 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 430. Online publication date: May 26, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.