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Abstract Marine populations are generally well connected through larval exchange, and juvenile and adult migration. Genetic differentiation and/or local adaptation among populations are sometimes observed at small spatial scales. The marbled flounder (Pseudopleuronectes yokohamae) is a commercially important coastal species in Tokyo Bay, Central Japan, exhibiting different spawning phenology at a small scale. Using 30 highly polymorphic microsatellite loci, including the 16 new microsatellite loci developed in the present study, we estimated the genetic structure and demographic connectivity of specimens collected along Tokyo Bay in 2012–2013 and 2015–2016. F -statistics indicated a genetic differentiation between adult populations collected within and outside Tokyo Bay during both collection periods, but almost no difference was detected between the populations from the inner and outer parts of Tokyo Bay. Assignment tests directly estimated demographic connectivity between the inner and outer bays via larval dispersal and juvenile and adult migration. The average movement distance of marbled flounder was 13.1–29.6 km, with a maximum distance of 42.8–54.0 km. This movement distance contributed to the strong demographic connectivity between the inner and outer bays. Meanwhile, an indirect method using the isolation by distance (IBD) theory underestimated the average movement distance (5.0–7.8 km) because the isolated setting of Tokyo Bay resulted in a higher IBD slope. Based on the results of F -statistics and assignment tests, we suggest that a multilayered management by local and regional organizations may benefit the fishery in Tokyo Bay. Highlights • We estimate the population connectivity of marbled flounder around Tokyo Bay. • F -statistics and assignment tests showed connections among populations of Tokyo Bay. • Assignment tests showed an average movement distance of marbled flounder of 13–30 km. • An indirect method using isolation by distance underestimated the movement distance. [ABSTRACT FROM AUTHOR]

Abstract We conducted a laboratory experiment and field collections of juvenile marbled flounder (Pseudopleuronectes yokohamae) to assess growth rates of juveniles. In the laboratory, cultured juveniles of approximately 31 and 46 mm standard length grew fastest at 20 °C, while juveniles of approximately 21 mm grew faster at 12–14 °C than at 20 °C. This result confirmed that optimal temperature for growth of juveniles changes ontogenetically. Juveniles were also collected from shallow estuaries during April to May, during which the water temperature increased from 13 to 22 °C. The increase in optimal temperature is advantageous for juveniles, because both juvenile size and ambient temperature increase as the season progresses. Growth rates of juveniles were nearly maximum under given temperatures in the field when assessed from otolith microstructure. Thus, juveniles grow at high rates in the field, although ambient temperatures are not necessarily optimal for growth. Graphical abstract Unlabelled Image Highlights • Maximum growth rates of juvenile marbled flounder were examined in the laboratory. • Thermal optima increased from 12 to 14 °C to 20 °C with the size increase of juveniles. • Juveniles were collected in the field until May with temperatures below 20 °C. • In situ growth rates of juveniles were evaluated to be nearly maximum. [ABSTRACT FROM AUTHOR]

Estrogenic pollution has aroused great concern for its adverse effects on marine organisms. This study aimed to establish biomarker-based methods for detecting environmental estrogens using vitellogenin (Vtg) of teleost fishes inhabiting coastal areas of China. Firstly, Vtgs in marbled flounder ( Pseudopleuronectes yokohamae ), black rockfish ( Sebastes schlegelii ) and fat greenling ( Hexagrammos otakii ) were purified, characterized and used to prepare antibodies. Then, Vtg ELISA for each species was developed using purified Vtg and its antibody. Marbled flounder Vtg ELISA had a working range of 3.9–500 ng/mL and a detection limit of 2.1 ng/mL, and black rockfish Vtg ELISA had strong cross-reactivity with marbled flounder Vtg. Furthermore, Vtg induction in male marbled flounder exposed to pentadecafluorooctanoic acid (PFOA) was measured by developed ELISA. Plasma Vtg concentrations were significantly increased with PFOA concentrations in seawater and fish muscle. Therefore, Vtg ELISAs for these species might be useful tools for monitoring marine environmental estrogens. [ABSTRACT FROM AUTHOR]

Hatch date and settlement date distribution and planktonic larval duration (PLD) in yellow striped flounder in nursery grounds in the northern Japan Sea and in the Okhotsk Sea around Hokkaido (Northern Japan Sea–Okhotsk Sea population) were investigated. We examined the relationship between the ecological features and water temperature in these two locations where oceanographic conditions considerably differ. For both nursery grounds, the timing of hatch was early in a warm year and late in a cold year, indicating the strong link between water temperature and the timing of hatch in this population. Although spatial difference in hatch date in 2007 was not significant, hatching and settlement of juveniles collected in the Okhotsk Sea nursery (Okhotsk Sea subpopulation: OSS) occurred later than in those collected in the Japan Sea (Japan Sea subpopulation: JSS); in the spring, the water temperature of the Japan Sea rises earlier in the southern area. The precise area where eggs of both subpopulations originated is unknown; however, this study indicates that eggs that become the JSS may be produced further south than those for the OSS. Comparing on the same date, the water temperature around potential spawning area of OSS in 2006 was ca. 2 °C lower than in 2007 and 2009; however, the overall difference in water temperature at the median date of hatching was 0.7 °C. This result indicates that a spring rise in water temperature probably determines the timing of spawning and larval hatch of this population. Spatiotemporal differences in the PLD were affected by water temperature in which juveniles were exposed during pelagic phase. The PLDs were shorter in warmer years and for warmer subpopulation. The PLD of OSS was longer than that of JSS and spatial difference was statistically significant in 2006. Water temperature in which OSS was exposed in later pelagic phase was relatively low, and the growth of pelagic larvae of OSS was probably slow, and consequently, the PLD of OSS may become long. The eggs originating the OSS are spawned in the Japan Sea and transported a long-distance to their nursery ground in Okhotsk Sea. Generally, a slow growth rate is considered a negative factor for the early survival of fish, although it may be that the slow growth and long PLD of the OSS juveniles confers an advantage upon them during their long-distance transportation. For yellow striped flounder, this study primarily reports on hatch date and settlement date distribution and PLD of juveniles. For flatfish species, the study of the link between those features and water temperature is limited. This study expands the knowledge of the early life-cycle in flatfish, information on which is currently limited. [ABSTRACT FROM AUTHOR]

We investigated factors that might have disturbed the stock recovery of marbled flounder in Tokyo Bay by focusing on the early life stages. Field surveys in Tokyo Bay from 2006 to 2011 revealed that mature adult biomass increased from 2006 to 2008 and decreased thereafter. Meanwhile, larval and juvenile densities were high in 2006 and 2008 but low in other years. Discrepancies in the yearly trends of these parameters suggest that mortality during life stages between spawning and early larval phases might have affected the abundance of the subsequent life stages. Monthly mean water temperature between January and February, in which hatching and pelagic larvae occur in the bay, was lower in 2006 (8.6 °C) and 2008 (9.6 °C) than was observed in other years (10.4–11.4 °C). Significant negative correlation between water temperature and larval density implies that mortality during pre- and post-larval stages would be higher in warmer winter years (>10 °C). To test this hypothesis, we examined the effects of water temperature on mortality and development in egg and larval stages under controlled laboratory conditions. Hatching rate was high in a water temperature range of 9.2–12.7 °C (66.6–82.5%), whereas it decreased in cooler (3.7% at 5.9 °C) or warmer (33.9% at 14.8 °C) conditions. Meanwhile, days from fertilization to hatching, size of larvae at hatching and survival rate of larvae after 18 d from hatching were monotonically and significantly decreased as water temperature was elevated. Combined evidence of the field and laboratory studies suggests that a warmer reproductive season (>10 °C) might induce mortalities of marbled flounder larvae in Tokyo Bay. [ABSTRACT FROM AUTHOR]

This study identified ventilatory and behavioural responses in the marbled sole Pseudopleuronectes yokohamae under experimentally induced progressive decreases in dissolved oxygen ( DO) levels. Ventilation frequency showed an increase with decreasing DO levels from normoxia to 2·75 mg O2 l−1, followed by a decrease in ventilation frequency at decreased DO levels from 2·00 to 0·75 mg O2 l−1. At DO levels below 2·00 mg l−1, behaviours at the bottom were suppressed, whereas avoidance behaviours increased. A decrease in avoidance behaviours was observed from 1·00 to 0·75 mg O2 l−1. Upside-down reversal and incapacitation at DO levels of 1·00-0·75 mg O2 l−1 suggested that sublethal effects on P. yokohamae were induced. The responses observed before the sublethal DO level could be interpreted as an effort to maintain oxygen uptake, reduce routine activities and facilitate avoidance. The observed DO level thresholds that induce behavioural responses, in addition to sublethal effects, indicate hypoxia-tolerance that is important for understanding the effects of hypoxia on coastal ecosystems. [ABSTRACT FROM AUTHOR]

To determine the optimal temperature for juvenile (0 year old) marbled flounder Pseudopleuronectes yokohamae, juveniles of 40-54 mm standard length were reared at six temperature conditions in the range of 8-26 °C, using group- and individual-based methods. Growth of juveniles increased from 8 to 20 °C but decreased from 20 to 26 °C, irrespective of the rearing method used. Food intake was greatest at 20 and 24 °C compared with other temperatures, while feed conversion efficiency was greater at 20 °C than 24 °C in individual rearing. Individual rearing provided more information such as individual variations in growth and food consumption, suggesting the importance of individual-based experiments for exploring the optimal temperature for fish. [ABSTRACT FROM AUTHOR]

Occurrence, distribution and prey items of juvenile marbled sole Pseudopleuronectes yokohamae were investigated around a submarine groundwater seepage on a tidal flat in southwestern Japan. Spatial distribution of radon-222 ( 222 Rn) concentration in water showed more submarine groundwater seepage in the offshore area. The lower salinities at offshore sampling stations corresponded with the highest 222 Rn concentrations. Juvenile marbled sole were collected from March through June with seasonal peak in April in 2013 and 2014. Mean abundance of juvenile marbled sole was highest at the second most offshore station where high submarine groundwater seepage was indicated. Major prey items in the stomachs of the marbled sole at the post-settlement stage (10–40 mm) were small crustaceans such as cumaceans and gammarids, which were partially replaced with polychaetes in larger juveniles (40–50 mm). Abundance of these major prey items was also higher at offshore stations. A negative correlation between gammarid abundance and salinity indicated a higher concentration of gammarids around the area of high submarine groundwater seepage, a pattern not observed for the other major prey organisms. Stable isotope analysis showed greater dependence of post-settlement stage marbled sole on the small crustaceans with low δ 13 C indicating that nutrients of terrestrial origin contribute to production of the juvenile marbled sole on the tidal flat. [ABSTRACT FROM AUTHOR]

The effect of climate variability on flatfish includes not only the effects of warming on sensitive life history stages, but also impacts from more frequent or unseasonal extreme cold temperatures. Cold weather events can affect the overwintering capabilities of flatfish near their low temperature range limits. We examined the responses of two flatfish species, the thin-bodied windowpane ( Scophthalmus aquosus ) and cold-tolerant winter flounder ( Pseudopleuronectes americanus ), to variable winter temperatures in a Northwest Atlantic estuary using abundance and size data collected during a monitoring study, the Aquatic Biological Survey, conducted from 2002 to 2010. Winter and spring abundances of small (50 to 120 mm total length) juvenile windowpane were positively correlated with adult densities (spawning stock) and fall temperatures (thermal conditions experienced during post-settlement development for the fall-spawned cohort) of the previous year. Windowpane abundances in the estuary were significantly reduced and the smallest size class was nearly absent after several consecutive years with cold (minimum temperatures < 1 °C) winters. Interannual variation in winter flounder abundances was unrelated to the severity of winter temperatures. A Paulik diagram illustrates strong positive correlations between annual abundances of sequential winter flounder life history stages (egg, larval, Age-1 juvenile, and adult male) within the estuary, reflecting residency within the estuary through their first year of life. Temperature variables representing conditions during winter flounder larval and post-settlement development were not significant factors in multiple regression models exploring factors that affect juvenile abundances. Likewise, densities of predators known to consume winter flounder eggs and/or post-settlement juveniles were not significantly related to interannual variation in winter flounder juvenile abundances. Colder estuarine temperatures through the first year of life were associated with smaller Age-1 winter flounder body size. For example, Age-1 winter flounder developing under conditions that differed by 1.9 °C in mean daily water temperature, averaged 98.7 mm total length (TL) and 123.1 mm TL, for the relatively cold vs. moderate years, respectively. More frequent cold temperature extremes associated with climate variability may negatively impact the overwintering capabilities of some flatfish near their cold temperature range limits, whereas cold-tolerant species may experience reduced growth, which imparts the ecological challenges associated with smaller body size. [ABSTRACT FROM AUTHOR]

Otolith microstructure of reared and wild cresthead flounder Pseudopleuronectes schrenki larvae and juveniles was used to investigate the daily periodicity of ring formation, morphological change and unique otolith structure related to important life events. By comparing microstructural features of P. schrenki with those reported for other flatfish species, it was shown that there may be microstructural features that are common to all flatfishes. In the sagittae and lapillus, a check (a distinct ring) was formed in the centre of otoliths at c. 6 days post hatching, and the daily formation of rings observed outside the check was confirmed. During metamorphosis, accessory primordia ( AP) of otolith growth were formed on the outer edge of the sagittae, and the shape of the sagittae became more complex. No AP was formed on the lapilli, however, and otolith rings were concentrically formed throughout the larval and juvenile (≤51·6 mm standard length, LS) stages. It is proposed, therefore, that lapilli are more appropriate than sagittae for analysis throughout the larval and juvenile (≤51·6 mm LS) stages. During metamorphosis, unique rings that are relatively wide and show weak contrast are formed on lapilli (metamorphosing zone, MZ). Hence, the duration of metamorphosis, larval duration and the days of juvenile life can be estimated by the number of rings within the MZ, using rings from the check to outermost ring of the MZ, and that of rings formed outside MZ, respectively. The formation of AP on sagittae as well as the absence of AP, bilateral asymmetry and the formation of a unique structure during metamorphosis on lapilli have also been reported for other flatfishes. [ABSTRACT FROM AUTHOR]

Variation of scales on the blind side of Pseudopleuronectes yokohamae in relation to sex, maturity and body size was examined. Immature males often have cycloid scales, while mature males have mostly ctenoid scales. Large females also often have ctenoid scales (but with fewer spines compared with males), and small females have mostly cycloid scales. The number of spines (ctenii) on the blind-side scale increases with body size in both sexes, indicating an ontogenetic change in scale morphology. As P. yokohamae spawn demersal eggs with males positioning themselves above the females on the ocular side, it is hypothesized that ctenoid scales on the blind side in mature males function for maintaining contact with females during spawning. [ABSTRACT FROM AUTHOR]

Highlights: [•] We obtained the respiratory uptake efficiencies (E W) of 99 compounds by fish. [•] The relationship between the E W values and log K OW was analyzed. [•] The E W of the compounds increased with increasing the log K OW up to a log K OW of 5. [•] We derived an equation for predicting E W based on a two-phase resistance model. [Copyright &y& Elsevier]

The authors investigated the kinetics of transfer of perfluorooctane sulfonate (PFOS) from water, suspended sediment, and bottom sediment to a marine benthic fish, the marbled flounder ( Pseudopleuronectes yokohamae). Fish were exposed in 3 treatments to PFOS in combinations of these exposure media for 28 d and then depurated for 84 d. A major part (37-66%) of PFOS in the fish was in the carcass (i.e., whole body minus muscle and internal organs). Three first-order-kinetic models that differed in exposure media, that is, 1) sum of dissolved and particulate phases and sediment; 2) dissolved phase, particulate phase, and sediment; and 3) dissolved phase only, were fitted to the data assuming common rate constants among the treatments. The uptake efficiency of dissolved PFOS at the respiratory surfaces was estimated to be 3.2% that of oxygen, and the half-life of PFOS in the whole body to be 29 d to 31 d. The better fit of models 1 and 2 and the values of the estimated uptake rate constants suggested that the PFOS in suspended and bottom sediments, in addition to that dissolved in water, contributed to the observed body burden of the fish. Based on an evaluation of several possible contributing factors to the uptake of PFOS from suspended and bottom sediments, the authors propose that further investigation is necessary regarding the mechanisms responsible for the uptake. Environ Toxicol Chem 2013;32:2009-2017. © 2013 The Authors. Environmental Toxicology and Chemistry Published by Wiley Periodicals, Inc., on behalf of SETAC. This is an open access article under the terms of the Creative Commons Attribution Non-Commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes. [ABSTRACT FROM AUTHOR]

We evaluated the extent of shrinkage in body size of juvenile marbled sole Pseudopleuronectes yokohamae after preservation in 70% ethanol for 6, 12, 24, or 48 h, or 4 weeks. Standard length (SL, range of the analyzed specimens: 22.82-53.01 mm) decreased by 5.6% after 12 h and body weight (BW 0.174-2.964 g) decreased 27.8% after 24 h preservation in 70% ethanol. There was no further decrease in SL or BW after 12 or 24 h of preservation, respectively. The original body size could be estimated based on the size after preservation in 70% ethanol for 4 weeks using the following equations: SL = 1.05 SL + 0.37 and BW = 1.36 BW + 0.04. The condition factor calculated using the body size of preserved individuals was 16.0 and 15.8% lower than that calculated from the original body size and the body size back-calculated using the linear regression equations described above, respectively. Thus, our data suggest that the shrinkage of body size due to preservation in ethanol can cause errors in estimation of the condition factor. Our results can be used to improve the accuracy of estimating size-related biological parameters based on juvenile marbled sole that are preserved in ethanol. [ABSTRACT FROM AUTHOR]

Abstract: To evaluate the dietary uptake of polychlorinated biphenyls (PCBs) from live food, we investigated the dietary uptake and depuration kinetics of PCBs in a marine benthic fish (marbled sole, Pseudopleuronectes yokohamae) by using as food live sandworms (Perinereis nuntia) that were laboratory-exposed to field-collected PCB-contaminated sediment. Marbled sole were fed the PCB-contaminated sandworms for 28d and then uncontaminated sandworms for 56d. The assimilation efficiencies (AEs) of 84 PCB congeners via the gastrointestinal tract (GIT) to the muscle of the fish ranged from 0.21 to 0.78; whole-body AEs would be lower than those of muscle because of the lower PCB concentrations, on a lipid basis. The AEs determined in this study were lower than those in other studies that used PCB-spiked commercial pelletized food. The lower AEs found in this study might be attributable to differences in the food administered (live sandworms vs. commercial pellet food), possibly because of low digestibility of sandworm lipids by marbled sole. In addition, the AEs in this study tended to increase with increasing log octanol–water partition coefficients (K OW) up to about seven, although AEs in the other studies using commercial pelletized food did not increase with increasing log K OW. This result suggests the co-transport of highly hydrophobic PCB congeners along with lipids and fatty acids from the digested sandworms into the GIT epithelium cells. The growth-corrected half-lives of 26 PCB congeners in the muscle of fish ranged from 20 to 107d. [ABSTRACT FROM AUTHOR]

Background: Epidermal pseudotumours from Hippoglossoides dubius and Acanthogobius flavimanus in Japan and gill lesions in Limanda limanda from the UK have been shown to be caused by phylogenetically related protozoan parasites, known collectively as X-cells. However, the phylogenetic position of the X-cell group is not well supported within any of the existing protozoan phyla and they are currently thought to be members of the Alveolata. Ultrastructural features of X-cells in fish pseudotumours are somewhat limited and no typical environmental stages, such as spores or flagellated cells, have been observed. The life cycles for these parasites have not been demonstrated and it remains unknown how transmission to a new host occurs. In the present study, pseudobranchial pseudotumours from Atlantic cod, Gadus morhua, in Iceland and epidermal pseudotumours from the northern black flounder, Pseudopleuronectes obscurus, in Japan were used in experimental transmission studies to establish whether direct transmission of the parasite is achievable. In addition, X-cells from Atlantic cod were sequenced to confirm whether they are phylogenetically related to other X-cells and epidermal pseudotumours from the northern black flounder were analysed to establish whether the same parasite is responsible for infecting different flatfish species in Japan. Results: Phylogenetic analyses of small subunit ribosomal DNA (SSU rDNA) sequence data from Atlantic cod X-cells show that they are a related parasite that occupies a basal position to the clade containing other X-cell parasites. The X-cell parasite causing epidermal pseudotumours in P. obscurus is the same parasite that causes pseudotumours in H. dubius. Direct, fish to fish, transmission of the X-cell parasites used in this study, via oral feeding or injection, was not achieved. Non-amoeboid X-cells are contained within discrete sac-like structures that are loosely attached to epidermal pseudotumours in flatfish; these X-cells are able to tolerate exposure to seawater. A sensitive nested PCR assay was developed for the sub clinical detection of both parasites and to assist in future life cycle studies. PCR revealed that the parasite in P. obscurus was detectable in non-pseudotumourous areas of fish that had pseudotumours present in other areas of the body. Conclusions: The inability to successfully transmit both parasites in this study suggests that either host detachment combined with a period of independent development or an alternate host is required to complete the life cycle for X-cell parasites. Phylogenetic analyses of SSU rDNA confirm a monophyletic grouping for all sequenced X-cell parasites, but do not robustly support their placement within any established protist phylum. Analysis of SSU rDNA from X-cells in Japanese flatfish reveals that the same parasite can infect more than one species of fish. [ABSTRACT FROM AUTHOR]

Despite its recreational and commercial importance, the movement patterns and spawning habitats of winter flounder (Pseudopleuronectes americanus) in the Gulf of Maine are poorly understood. To address these uncertainties, 72 adult winter flounder (27-48 cm) were fitted with acoustic transmitters and tracked by passive telemetry in the southern Gulf of Maine between 2007 and 2009. Two sympatric contingents of adult winter flounder were observed, which exhibited divergent spawning migrations. One contingent remained in coastal waters during the spawning season, while a smaller contingent of winter flounder was observed migrating to estuarine habitats. Estuarine residence times were highly variable, and ranged from 2 to 91 days (mean=28 days). Flounder were nearly absent from the estuary during the fall and winter months and were most abundant in the estuary from late spring to early summer. The observed seasonal movements appeared to be strongly related to water temperature. This is the first study to investigate the seasonal distribution, migration, and spawning behavior of adult winter flounder in the Gulf of Maine by using passive acoustic telemetry. This approach offered valuable insight into the life history of this species in nearshore and estuarine habitats and improved the information available for the conservation and management of this species. [ABSTRACT FROM AUTHOR]

This study assessed the paternal effects on the growth of early juvenile winter flounder Pseudopleuronectes americanus and examined the energy allocation strategy employed during this critical stage. Males from three different locations (Passamaquoddy Bay, Baie-des-Chaleurs and the St Lawrence Estuary) were crossed with females from the Baie-des-Chaleurs, and the growth characteristics of hybrids from settlement to 45 days post-settlement were monitored under similar culture conditions. Young juveniles displayed good growth rates (0·09 ± 0·02 mm day−1), with no differences related to sire origin, in terms of growth indicators (length, width, RNA:DNA and triacylglycerol:sterol ratios), condition indices (Fulton's K, pigmentation and fin erosion) and biochemical components (nucleic acids, proteins and lipid classes). These results suggest the absence of a paternal contribution to the growth strategy during the early juvenile stage of P. americanus. The results also highlight the high energetic cost associated with metamorphosis: young juveniles mobilized most of their triacylglycerol reserves during the growth period following settlement. [ABSTRACT FROM AUTHOR]

The aim of the present study was to clarify the effect of a feeding regimen of live food enriched with docosahexaenoic acid (DHA) on the rates of abnormal morphology in larval brown sole Pseudopleuronectes herzensteini. Live foods were enriched with oil emulsion to produce both high-DHA and low-DHA content. Larvae in group 1 (control) were fed low-DHA-content live foods throughout the experiment. Conversely, larvae in group 2 were fed high-DHA live foods from 15 days post-hatching (dph), when larvae were D stage. Larvae in group 3 were fed high-DHA live foods from 25 dph, when larvae consisted mainly of E stage. The occurrence of normal morphology development in group 2 was significantly higher ( P < 0.05) than those of groups 1 and 3, suggesting that normal morphology of brown sole is determined during the critical larval period (D–E stages). [ABSTRACT FROM AUTHOR]

We examined the effect of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on the rates of abnormal morphology in juvenile brown sole Pseudopleuronectes herzensteini. Larvae during the D–E stages (15–24 days post hatching) were fed live food containing various amounts of DHA and/or EPA prepared using emulsified oils (DHA ethyl ester, EPA ethyl ester, and corn oil). Larvae during the F–I stages were fed Artemia enriched with a commercial diet supplement. We found that DHA and EPA promoted larval development and improved the incidence of morphological abnormalities in brown sole juveniles to a similar extent. However, DHA was more effective than EPA in preventing the appearance of morphological abnormalities in brown sole. The incidence of normal morphology was clearly improved by an increase of the DHA content in brown sole larvae at 25 days post-hatching. These results suggest that it is important to promote larval development and feed larvae with live food containing high levels of DHA during the D–E stages to prevent morphological abnormalities in brown sole juveniles. [ABSTRACT FROM AUTHOR]

We examined the age and growth of the marbled sole Pseudopleuronectes yokohamae collected from Tokyo Bay, Japan, during two study periods between 2002 and 2008, when the stock size was consistently low. The von Bertalanffy growth equations were found to differ significantly between sexes, and females attained a larger standard length than males of the same age. These results were then compared with those reported for 1974–1983 and 1986–1988, two study periods when the stock size was high. The growth of both sexes of marbled sole in Tokyo Bay during the 2000s was found to be significantly higher than that in the 1970s and 1980s. To explore possible factors causing these changes in the growth, we examined bottom water temperature and population density. We found that the population density decreased and the bottom water temperature increased between the late 1970s and the late 2000s. However, despite evidence of changes in population densities and water temperatures, further study is needed to determine the main factors causing the observed changes in growth. [ABSTRACT FROM AUTHOR]

To resolve varied and sometimes conflicting accounts of spawning and habitat characteristics for winter flounder Pseudopleuronectes americanus, seasonal patterns in abundance and reproductive condition were investigated in the New York Bight, near the southern edge of their current reproductive range. Fish were collected from trawl surveys on the inner continental shelf from October 2006 to October 2007. Pseudopleuronectes americanus were most abundant during January and April surveys, were rarely collected in August, with intermediate abundances in June and October. Measurements of fish condition [hepato-somatic index ( IH), condition factor ( K) and the per cent dry mass of muscle tissue (% MD)] and reproductive condition [gonado-somatic index ( IG)] were determined to evaluate seasonal changes in energy accumulation and depletion and reproduction. Males and females had similar patterns in body and reproductive condition, although the magnitude of change was greater for females. IH values were highest during spring and early summer, suggesting increased feeding following spawning. K and % MD increased through spring and summer then declined in the autumn and winter concurrent with gonadal development. Gonads began developing in the autumn, and in January, IG values approached spawning levels, with many spent individuals collected in spring. Within these general patterns, however, there was a large degree of variability among individuals, and a few mature non-reproductive (‘skipped spawning’) females were observed. In the period after spawning, increased energy intake, indicated by increased IH, may influence reproductive output since this energy is gradually transferred to the muscle and used for gonadal development in the forthcoming year. The occurrence of ripening individuals on the inner continental shelf in January suggests that these fish either rapidly move into estuaries to spawn by February–March or they remain on the inner shelf to spawn, or some combination of these. Future studies should evaluate these possibilities, as both estuarine and inner shelf habitats are potentially affected by activities such as dredging, sand dredging and wind energy development. [ABSTRACT FROM AUTHOR]

To examine survival processes in marbled sole Pseudopleuronectes yokohamae larvae, nutritional transition date distributions (NTDDs) were compared between larvae and large juveniles (LJs) in Hakodate Bay from 2001 to 2003. NTDDs were used instead of hatch date distributions because the onset of increment formation coincides with the timing of the transition from endogenous to exogenous nutritional sources for marbled sole. LJs were defined as being large enough to be safe from predation by the sand shrimp Crangon uritai. In 2001 and 2002, the ranges of the NTDDs of LJs largely overlapped with those of the larvae. However, in 2003, the early cohort (those whose otolith rings formed before 17 March) disappeared from the NTDDs during and after April, and the NTDDs of LJs were heavily biased toward a later period compared to those of the larvae. In 2003, Oyashio coastal water (<3°C and ≤33.0 salinity) unexpectedly intruded into the bay in late March and lowered the water temperature from 6.3°C on 6 March to 4.1°C on 25 March. One possible cause of mortality in the early cohort of 2003 may be feeding failure caused by the extremely low water temperature. [ABSTRACT FROM AUTHOR]

To find an appropriate method for age determination in the marbled sole Pseudopleuronectes yokohamae in Tokyo Bay, Japan, sagittal otoliths of 1,343 individuals were observed by surface-reading and cross-section methods and the results were compared. Opaque zones occurred once a year and were regarded as annuli in both methods. The surface-reading method sometimes provided a lower count of the number of annuli than the cross-section method, and the frequency of this discrepancy was highest in older fish (males above 5 years, females above 4 years). The oldest female fish was estimated to be age 10 years by the cross-section method but 8 years by the surface-reading method. The cross-section method could provide a more accurate estimate of age and is therefore likely to be indispensable to estimations of longevity. In contrast, the surface-reading method is superior in terms of cost and time efficiency but is likely to underestimate the ages of older fish. However, growth equations based on age estimated by the surface-reading method were sufficiently accurate if males ≥5 years and females ≥4 years were combined as specific, single age groups of 5+ and 4+, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Cryopreservation of fish embryos has proven to be an elusive goal. Two reasons for this lack of success are their high chilling sensitivity and the formation of ice crystals while in the frozen state or during the thawing process. Antifreeze proteins (AFP) that protect marine teleost fishes from freezing in subzero waters have been shown to be capable of inhibiting ice recrystallization and protecting cell membranes from cold induced damage. Therefore they have the potential to improve the success of embryo cryopreservation. A recent study demonstrated that vitrified winter flounder embryos continued to show developmental changes following thaw [V. Robles, E. Cabrita, G.L. Fletcher, M.A. Shears, M.J. King, M.P. Herráez, Vitrification assays with embryos from a cold tolerant sub-arctic fish species, Theriogenology 64 (2005) 1633–1646]. Since winter flounder produce AFP it was hypothesized that these proteins, if present in the embryos, could have contributed to this progressive step towards success. Winter flounder produce three species of type 1 AFP: a small liver type, a large “hyperactive” liver type and a skin type. This study was conducted to determine which, if any, of these AFP genes was being expressed in pre-hatch winter flounder embryos. There was no evidence of AFP activity in freshly fertilized embryos. However, low levels of AFP activity were found in embryos at 4, 8, and 11 days post-fertilization. Reverse transcriptase-polymerase chain reaction (RT-PCR) analyses of the AFP mRNA isolated from the embryos revealed the expression of seven different skin type AFP genes that translated into four distinct AFP. Neither of the liver type AFP genes was expressed in the embryos. [Copyright &y& Elsevier]

The pattern-related capacity for the dispersion of previously aggregated melanosomes in low concentrations (3 × 10−6 to 10−8 M) of noradrenaline in vitro was observed in melanophores from winter flounder Pseudopleuronectes americanus. With 10−8 M noradrenaline, dispersion was completed more rapidly than in controls using the incubation vehicle alone. Melanophores from white-spot, dark-band and general background components of the integumentary pattern displayed different ‘transition ranges’ between melanosome aggregation and dispersion in higher and lower concentrations of noradrenaline. Within each ‘transition range’ individual noradrenaline concentration decrements could result in highly variable degrees of melanosome dispersion. The relative breadth of the noradrenaline ‘transition range’ concentrations could be represented as dark bands > general background > white spots. The threshold noradrenaline concentration for dispersion was highest for the dark bands. It is concluded that these differences represent variations in the transition from melanophore α-adrenoceptor-mediated pigment aggregation to β-adrenoceptor-mediated dispersion between localized areas of the skin. Such variations in ‘transition range’ will have an important role in the expression of flatfish patterns and in their changes in colour and texture. [ABSTRACT FROM AUTHOR]

A laboratory calibration experiment was conducted to determine the relationship between nucleic acid-based variables and growth rate in young-of-the-year winter flounder Pseudopleuronectes americanus. Three temperatures and three feeding levels were used to produce a variety of growth rates. Nucleic acid analyses were conducted on white muscle tissue using an ultraviolet absorption assay. RNA concentration (μg mg−1 wet tissue mass) and the ratio of RNA:DNA ( RRD) were positively correlated with a mass-based instantaneous growth coefficient ( GM) ( r = 0·42 and 0·72, respectively). Fifty-one per cent of the variability in growth rate was explained by the simple linear regression GM=−0·02615 + 0·00848 RRD ( P < 0·001). This model can be used to estimate recent growth rates for early juvenile winter flounder (27–52 mm standard length) at temperatures ranging from 11 to 24° C. [ABSTRACT FROM AUTHOR]

Abstract: The Magnuson-Stevens Fishery Conservation and Management Act defines essential fish habitat (EFH) as “the waters and substrate necessary to fish for spawning, breeding, feeding, and growth to maturity” and the protection of nursery areas has become a key element in US Federal fisheries management. Distribution and abundance by habitat for age-0, young-of-the-year (YOY) winter flounder, Pseudopleuronectes americanus, were compared for 28 Maine estuaries to help define essential fish habitat for this life history stage. The Maine coast was divided into three broad geographic zones based upon geological features and sampled over 5 consecutive years; during April–November of 2000 in the Mid-coast, in 2001 and 2002 along the Southwest coast and in 2003 and 2004 along the Eastern Maine coast. One beam trawl (2.0m width, 3mm mesh) sample was collected in one to four habitats in estuaries: eelgrass (Zostera marina), kelp (Laminaria longicruris), drift algae (Phyllophora sp.) and unvegetated sand/mud. Fish were sampled every 2 weeks, April–November 2000–2004. Abundance of YOY winter flounder was greatest in Mid-coast estuaries between Casco and Penobscot Bays and was significantly lower in Southwest and Eastern estuaries. Abundance was similar across all four habitats in Mid-coast estuaries in 2000. In the other years, YOY were found in higher abundance in eelgrass relative to other habitats. A logistic regression model based on nearshore habitat characteristics was developed to predict the distribution of this species along the three broad geological zones of the Maine coast with the physical and biological variables most important in discriminating between habitats with and without individual fish identified. This logistic regression model correctly classified winter flounder 72.4% of the time based on the year, zone, the physical habitat variables (temperature, salinity, depth) and the presence–absence of submerged aquatic vegetation (eelgrass, kelp or algae). These results indicate that the type of habitat most important to YOY winter flounder varies among estuaries and EFH for this species and life stage must be defined with care. [Copyright &y& Elsevier]

The spatial scales at which the dynamics of subpopulations are synchronized affect regional population persistence and reflect the operational spatial scales of factors regulating populations. I examined phase synchrony in the fluctuations of age-0 winter flounder (Pseudopleuronectes americanus) production among 19 southern New England (SNE), USA, coastal nurseries. From 1990 to 2004, nursery production was synchronized at scales up to ~200 km based on spatial trends in cross-correlations of first-differenced age-0 abundance time series. However, sliding window analysis of 1975–2005 time series collected in six nurseries ≤55 km apart in northern SNE indicated that synchrony increased from low to high values in the early 1990s. Synchrony in production also increased among three nurseries ≤65 km apart in southern SNE from 1984 to 2004. Thus, interannual fluctuations in nursery production appeared to become synchronized at coarser spatial scales throughout SNE during the 1990s. This coarsening of the spatial scale of control of winter flounder nursery production was coincident with an increase in the frequency of springs with warm temperatures believed to negatively affect early life history processes. Spatial synchronization of winter flounder nursery ground production could destabilize the age-class structure and population dynamics in the region. [ABSTRACT FROM AUTHOR]