Search

The temporal changes in the fish community structure before and after a tsunami in 2011 were investigated in Funakoshi and Otsuchi bays, Iwate prefecture, on the Pacific coast of northern Japan. Fish species richness, abundance, biomass, and species composition were analyzed in relation to temporal variability of biotic and abiotic environmental conditions in two sub-intertidal seagrass Zostera marina beds. Mean seagrass shoot density decreased to

The asari (Manila) clam Ruditapes philippinarum is a commercially important bivalve that lives on tidal flats, but the clam landings have decreased in many estuaries in Japan. To increase the production of the clam, we conducted pilot translocation experiments at small spatial scales within the estuarine system of Matsukawaura Lagoon, Japan. Two scales were used: one was a horizontal translocation from an area with low clam productivity to an area with high productivity, and the other was a vertical translocation from the upper area to the lower area of the tidal flat. Our caging experiment with the horizontal translocation revealed that the growth rate and somatic condition of the clams translocated to favorable conditions were significantly better than those remaining in the original habitat. On a sandy fishing ground, vertical translocation of clams from the upper intertidal zone to the lower intertidal zone resulted in higher growth rates and better somatic conditions for the clams. Moreover, the clams from sandy ground showed larger growth increases than those from muddy-sand ground, indicating that the origin of clams affected translocation effectiveness. We found that clam biomass increased by 42%– 53% with the vertical translocation of small (

Asari clam (or Manila clam)Ruditapes philippinarumis an important bivalve for local fisheries. This species exhibits a large variation in shell morphology, and the shell roundness tends to be greater in more unsuitable habitats. To test whether the increments in shell size parameters (length, height and width) were affected solely by environmental conditions or by internal factors such as initial shell shapes or growth rate, a field caging experiment was conducted at two different sites of unsuitable and suitable habitats in Matsukawaura Lagoon, Japan, where shell shapes of wild clams were significantly different between the habitats. In the experiment, clams were released from the two sites to the same site or to the other site and were re-collected after 3, 6 and 12 months of caging. Caged clams originating from unsuitable habitats and released to suitable habitats showed a reduction in shell height relative to shell length, while clams from suitable habitats introduced to unsuitable habitats showed marked increases in both shell height and width. Generalized linear mixed models suggested that the increase in shell height was affected largely by the release habitat (environment) whereas the increase in shell width was affected largely by the individual growth rate. These results suggest that marginal growths in shell height and width respond differently to external and internal factors of clams, resulting in plasticity in their shell shapes according to the environments to which they are translocated.

Seasonal changes in habitat use in terms of depth and temperature were estimated for Japanese flounder Paralichthys olivaceus from the Pacific coast of northeastern Japan from 2006 to 2008, using data from trawl and gillnet fisheries logbooks, to which we assigned monthly estimates of bottom temperature. Estimated distributions of flounder for depth and temperature were validated by actual depth and temperature readings from data storage tags (DSTs) attached to flounder, and from collection records by trawl survey. Year-round, flounder > 300 mm in total length were present mainly in areas

The sharp-nosed sand goby Favonigobius gymnauchen is one of the most dominant fish species around tidal flats and sandy beaches in Japan and plays an important role in the food web. To clarify the habitat utilization and secondary production of F. gymnauchen in these waters, we investigated the density, size compositions, feeding, and prey availability in sandy beaches, a muddy sand estuary, and a seagrass bed in Hiroshima Bay, central Seto Inland Sea, Japan. The density of F. gymnauchen was the highest in the estuarine habitat and the lowest in the sandy beaches. They mainly consumed copepods, gammarids, and polychaetes. The body sizes of F. gymnauchen were larger in the estuarine habitat than in the seagrass bed, although prey availability was higher in the seagrass bed than in the estuary. Secondary production of F. gymnauchen was the highest (> 1 g wet weight m−2 year−1) in the estuarine habitat. The growth rate in the estuarine habitat was estimated to be 0.2 mm d−1. In a laboratory experiment in which fish were exposed to various salinity conditions and fed excess food, the feeding and growth of F. gymnauchen were not significantly different at salinities of 5, 15, and 30, and the maximum growth of juveniles at nearly 25 °C was estimated to be 0.2 mm d−1. These results indicate that F. gymnauchen grows at nearly maximum rates in estuarine habitats despite their high density, thereby resulting in the high secondary production of this species., This study was partly supported by JSPS KAKENHI Grant Number 19K06207.

The sand lance Ammodytes japonicus in the Seto Inland Sea burrows into sandy benthic sediments to rest, escape predation, and estivate. To investigate the physical properties of the sediments preferred by A. japonicus, we conducted a laboratory experiment measuring the incidence at which individuals burrowed into different types of benthic sediments collected from the Mihara Strait, a part of the Seto Inland Sea, Japan. Using stepwise multiple regression analyses, we confirmed that shear strength was the most important factor explaining variations in the mean number of A. japonicus burrowing into a given sediment. The number of burrowed individuals was the highest in sediments with low shear strength, suggesting that the ease with which burrowing A. japonicus individuals can penetrate the sediment strongly affects habitat preference.

Japanese Spanish mackerel Scomberomorus niphonius is a target species for stocking, but its biological characteristics at the juvenile stage are not well understood. Here, we investigated the high-temperature and starvation tolerances of hatchery-reared juveniles in captivity. We used juveniles of approximately 40 mm standard length, the size of juveniles released into the field. The upper incipient lethal temperature (50% lethal water temperature) was estimated to be 31.8 °C, higher than the maximum sea surface temperature in the field (approximately 29 °C). The critical thermal maximum was 34.8 °C, whereas it was 36.1 °C when juveniles were preliminarily acclimated to 31 °C for 24 h. Juveniles died from 3 to 11 days under nonfeeding conditions at 20 °C, but from 2 to 7 days at 27 °C. This information is expected to contribute to the development of the production of juvenile Japanese Spanish mackerel., This study was partly supported by JSPS KAKENHI Grant Number 19K06207.

Left-sided inferior vena cava (IVC) is a rare congenital malformation, as is persistent descending mesocolon, a developmental anomaly in which the colonic mesentery does not fuse with the dorsal abdominal wall. Although these anomalies are mostly asymptomatic, they should be identified preoperatively to avoid iatrogenic injury. We report a case of sigmoid colon cancer in a patient with both anomalies. The patient was an 80-year-old man whose preoperative computed tomography (CT) scan showed that the IVC ascended vertically along the left side of the abdominal aorta, and the descending colon was at the abdominal midline. Coronal CT was particularly useful for visualizing these anomalies. With this better understanding of the malpositioned anatomy, we successfully performed laparoscopic sigmoidectomy with lymph node dissection. Careful evaluation of preoperative CT imaging based on a clear understanding of such anatomical anomalies is particularly important for performing safe laparoscopic surgery.

To determine the annual reproductive cycle and the formation of spawning grounds in the Japanese jack mackerel Trachurus japonicus in the Uwa Sea, Japan in relation to sea temperature, seasonal changes in the ovary histomorphology and the catch per unit effort (CPUE) of adult fish were analyzed. Japanese jack mackerel in this region initiated vitellogenesis in winter and spawned between late April and early July in 2013–2015, with a quotient analysis suggesting that suitable temperatures for these two processes were 16–20 °C and 16–21 °C, respectively. However, the CPUE of adult fish was consistently high in the central Uwa Sea irrespective of temperature, indicating that the dense distribution of adult fish there is affected by additional parameters, such as phytoplankton productivity and migration. Comparison of the hatching period with the spawning season suggested that individuals recruited to the population in the Uwa Sea are derived not only from the Uwa Sea but also from other sea areas including the East China Sea. Therefore, further research on the hatching sites and recruitment processes of Japanese jack mackerel is required to evaluate the effectiveness of conservation measures for adult fish in the Uwa Sea.

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.

This paper aims to assess the diel feeding pattern and seasonal variation in the daily ration of immature and mature marbled flounder (Pseudopleuronectes yokohamae ). A day‐night collection by bottom trawls was conducted in Sendai Bay in July 2014. Marbled flounder (131–493 mm total length; Number of collected individuals = 1830, Number of analyzed individuals = 497) fed mainly on polychaetes during the day. At night, stomach content weight decreased with time, but the weight and proportion of bivalve siphons were consistently higher at night than during the day, suggesting nocturnal feeding by the flounder on bivalve siphons. Daily ration was greater in females (, This work was partly supported by the Stock Assessment Program of Fisheries Agency and Fisheries Research and Education Agency of Japan and the program “Project on Clarifying the Impact of Nuclear Substances” of the Fisheries Agency of Japan.

Diel vertical migration of the cutlassfish Trichiurus japonicus larvae were investigated by consecutive 24-h collections at 3-h intervals at a station in the central Seto Inland Sea, Japan in June and September. Only one larva was collected in June 2017, while 224 and 40 larvae were collected in September 2016 and 2017, respectively. Larvae were present only at depths of ≥ 11 m during the day, whereas they were present at depths of 1, 6, 11 and 16 m during the night. Migration was observed in larvae in which swim bladder formation was completed. A similar pattern, namely nocturnal occurrence at shallow depths only of the developed larvae, was observed in another 24-h survey, suggesting that the swim bladder regulates the upward movement of larvae at night., This work was partly supported by the Environment Research and Technology Development Fund (S-13) granted by the Ministry of the Environment, Japan.

Quantification of myocardial flow reserve (MFR) provides diagnostic value for detection of cardiovascular artery disease. However, the common calculation method for MFR requires dynamic acquisition and specific software. The study aimed to predict coronary artery disease by simpler calculation of myocardial count without the use of dynamic data from 13N-ammonia myocardial perfusion positron emission tomography (MP-PET). This study included 40 consecutive patients suspected of ischemic heart disease and 7 healthy controls (34 men and 13 women, 66 ± 12 years). All participants underwent adenosine stress and rest 13N-ammonia MP-PET. From the dynamic images, the MFR in the entire left ventricular myocardium (ELV) and the three-vessel area was calculated by dividing stress myocardial blood flow (MBF) by rest MBF. From the static images, the myocardium-to-background ratio (MBR) was calculated by dividing each area’s counts/pixel by background counts in the upper thoracic aorta/pixel in both stress and rest images. The MBR-increasing rate (MBR-IR) was calculated by dividing stress MBR by rest MBR. The relationship between MFR and MBR-IR in each area was examined. The cutoff diagnostic value of MBR-IR corresponding to that of MFR for detection of cardiovascular artery disease was calculated. Each MBR-IR was closely correlated with each MFR (r = 0.830 in ELV, r = 0.864 in LAD, r = 0.829 in LCX, r = 0.757 in RCA). The cutoff values of MBR-IR were 1.45 in ELV, 1.46 in LAD, 1.41 in LCX, and 1.45 in RCA, respectively. This study demonstrated that quantification of MBR-IR may provide diagnostic value for detection of coronary artery disease as well as MFR.

Predators often affect prey production not only by lethal predation but also by unintentional inhibition of feeding and growth. The present study examined the lethal and non-lethal effects of the invasive naticid Laguncula pulchella on the survival and growth of the prey clam Ruditapes philippinarum in a sandy tidal flat. Cages accommodating 30 clams (10 individuals × 3 size classes of ≤ 20 mm, 20–30 mm, and > 30 mm shell length) and one L. pulchella (approximately 37 mm shell height) per cage were buried in the tidal flat for 10 weeks. Medium sized clams were consumed by predators much more (80.5%) than small (12.2%) and large clams (7.3%). Clams were consumed by L. pulchella at a frequency of 0–2.5 individuals per predator per week. The growth of clams caged with L. pulchella was lower (23, 27, 33, 41, and 57% for clam of 10, 20, 30, 40, and 50 mm, respectively) than that in control cages (clams without L. pulchella). The clam burial depths did not increase by the presence of predators in a laboratory experiment, indicating that growth suppression was caused by the reduced feeding activity following physical disturbance and/or chemical signals. The results of this study demonstrate that the introduction of L. pulchella reduced the productivity of the commercially important clams not only by lethal predation but also by mere presence.

Hairtails (family Trichiuridae) are an important group of fish for coastal fisheries worldwide. In the view to reiterate the need of management of hairtails found in the Republic of the Union of Myanmar, the species composition of hairtails was investigated according to the morphological characteristics and DNA barcoding of mitochondrial cytochrome c oxidase subunit I gene. A total of 95 individual landed fish were sampled from fish markets in Yangon and Myeik. The hairtails were treated similarly to the group without species distinction at the fish markets, which consisted of five species from three genera, namely Trichiurus sp., Lepturacanthus savala, Lepturacanthus sp., Eupleurogrammus sp., and Eupleurogrammus muticus. Further studies on the biological characteristics and taxonomies are needed to establish improved approach of identifying with such fishery species in Myanmar.

Nymphonella tapetis (Pycnogonida, Ascorhynchidae) is an endoparasitic sea spider affecting bivalves. Recently, sea spiders have been found on a massive scale in the commercially important Manila clams (Veneridae, Ruditapes philippinarum) in Japan (Tokyo Bay). Simultaneously, mass mortality has occurred in this area. Local fishers assumed that this mass mortality was caused by the parasitic sea spider, despite the effect of the parasite and parasite intensity on the host being unknown. To evaluate the susceptibility of the Manila clam to sea spider infestation and the impact on mortality levels, we established six treatments at different infection intensities (density of newly hatched larvae of sea spiders) over a 6-month long laboratory experiment. We monitored mortality and three susceptibility indices (clearance rate, sand-burrowing speed and adductor muscle strength) under sufficient food conditions. Parasitization by sea spider affected clearance rate and sand-burrowing speed. The pattern of parasitic intensity effects on survival of Manila clam hosts was shown to be dependent on the levels of parasite numbers, i.e. clams with lower parasitic levels (total of

The determination of the optimum stocking density of hatchery-reared juveniles in relation to the carrying capacity of the nursery ground is important to the success of any stock enhancement programs. In order to estimate the surplus productivity of nursery grounds available to support hatchery-reared fish, a population growth model for juvenile Japanese flounder Paralichthys olivaceus was developed by extending an ecophysiology-based model on growth of juvenile fishes. Parameters of the model were adjusted using field-collected data from Ohno Bay in northeastern Japan. This model predicted the optimum stocking density, namely the maximum number of hatchery-reared juvenile Japanese flounder released into the bay without decreasing the growth of conspecific wild juveniles owing to food limitation. The optimum stocking density for juveniles of 89 mm total length was estimated to be 2000 individuals per 250,000 m2 in Ohno Bay in 1989. Under the model, the most important factors affecting the optimum stocking density of Japanese flounder were the abundance of mysids and wild juveniles at the time of release. The effect of abundance of a competing flatfish species on growth of wild Japanese flounder was less important.

Stocking hatchery fish into the wild should only be implemented at a level that can be sustained within the available food-based carrying capacity to avoid food resource competition with wild conspecifics. We constructed a simulation model to assess the growth of wild conspecifics under different magnitudes of hatchery fish releases, including no releases and actual release levels, and under different wild fish abundancies. Stocking of juvenile Japanese flounder Paralichthys olivaceus (approximately 70–110 mm TL) in Fukushima from 2003 to 2005 was analyzed. We monitored post-release changes in abundance of both cultured and wild juveniles and their prey (mysids). Our survey and modelled simulations revealed that the surplus prey production was sufficient to support the consumption of stocked and wild Japanese flounder (up to 150,000 individuals per site in 2003 and 2004), during which wild juveniles achieved nearly maximum growth rates. However, in 2005, during which a dominant year class of wild Japanese flounder occurred, the body size of wild juveniles was 49% smaller than the predicted size based on the maximum growth rates. This suggests that the food-based carrying capacity was reached in that year. Thus, it is important to evaluate the existing prey and wild juveniles levels and adjust the release accordingly every year.

The impact of the great tsunami, which was generated by the Great East Japan Earthquake on 11 March 2011, on the quality of a nursery ground for juvenile Japanese flounder Paralichthys olivaceus with a sandy bottom of

The tsunami caused by the 2011 Tohoku Earthquake with an epicenter off the Pacific coast had a significant effect on Manila clam, Ruditapes philippinarum, populations of northeastern Japan. In this study, the interannual variability of the clam density before and after the tsunami and monthly population dynamics after the tsunami were investigated in a tsunami-impacted brackish lagoon: Matsukawa-ura, Fukushima, northeastern Japan. In the lagoon, the fishery had been stopped after the tsunami, enabling the subsequent natural recovery process of the population to be assessed. Clam density immediately after the tsunami was markedly lower than before, suggesting substantial impact of huge tsunami. The impacts on clam population showed some degree of variation depending on the clam size and station. The smaller individuals, which have shallower burrowing depth and lighter individual weight, were swept away by direct tsunami more severely than larger individuals. Larger individuals locally remained with low densities at some stations shortly after the tsunami. Recruitment of early juvenile clams (

To investigate the response of the fish community structure to a natural disturbance in their habitat, fish abundance, biomass and species composition were analysed in relation to temporal variability of environmental conditions in a seagrass Zostera marina bed. A total of 3024 fishes belonging to 46 taxa (22 families) were collected by quantitative sampling for 10 years from 2007 to 2016 in the Seto Inland Sea, south-western Japan. Seagrass shoot density decreased to less than 1/20 of its original density after disappearance of vegetation caused by heavy rain in the autumn of 2011 and the area did not recover for the next five years. In order to analyse temporal changes of fish community, the fishes were divided into three groups depending on their habitats or lifestyles: pelagic or migratory species (PM), sand or mud bottom-associated species (SM) and seagrass (Z. marina) – or substrate (rocky bottom including macrophytes) – associated species (ZS). Multiple regression analysis showed seagrass shoot density had the most significant effect on biomass of ZS among the three groups, with higher fish biomass under higher seagrass shoot density. Fish community composition changed after the disappearance of the seagrass vegetation coverage with an increase in abundance of SM during the five years of the post-disturbance period. Seagrass vegetation was concluded to affect temporal change of fish community structure through a stronger influence on fish species that are more dependent on seagrass beds as habitat., This study was partially supported by the Global Environment Research Fund (J.S., grant number RF-0907and RF-1102) of the Ministry of the Environment, and Grant-in-Aid for Scientific Research (B) (J.S., grant number 24380107).

Case 1: 83 years old man. For left upper lobe lungs squamous cell carcinoma infiltrating left main pulmonary artery. After 2 courses went of carboplatin(CBDCA)(AUC: 6)+weekly nab-paclitaxel(nab-PTX)(AUC: 6)+, left upper lobectomy and ND2 lymph nodes dissection. Tumor disappeared in pathology and diagnosed of Ef. 3. Case 2: 81 years old man. Right upper lobe lungs squamous cell carcinoma in #4R lymph node metastasis with the superior vena cava invasion. After 2 courses went of CBDCA(AUC: 6)+weekly nab-PTX(100mg/m2), left upper lobectomy and ND2 lymph nodes dissection. Tumor disappeared in pathology and diagnosed of Ef. 3. Nab-PTX may be considered a preoperative chemotherapeutic agent of choice for squamous cell carcinoma.

This study tested the oxygen consumption rates (OCR), energy, and thermal coefficient of juvenile Lutjanus malabaricus (60 fish, size: 4.53 ± 1.14 g) at four temperatures of 22, 26, 30 and 34 °C. During 30 days of experimental period 5 fish tank−1 were reared at four temperatures with three replicates in intermittent flow respirometers in a recirculatory system under laboratory conditions. As expected, oxygen consumption rates increased significantly (P

Experienced thermal history often affects the temperature tolerance of fish; however, the effect of thermal history on growth performance is unclear. To contribute to effective stocking (release of hatchery-reared juveniles in the field), we conducted four laboratory experiments using juvenile marbled flounder (Pseudopleuronectes yokohamae, around 30 mm standard length and 0.3 g body wet weight) acclimated at 12 °C and 24 °C for approximately 2 weeks to investigate the effects of acclimation temperature on high-temperature tolerance, food consumption, and growth performance. The acclimation to 24 °C increased tolerance to high temperatures, as shown in a 24-h exposure experiment and in a temperature elevation experiment. The 50% lethal temperature (upper incipient lethal temperature) was estimated to be 25.9 °C and 29.0 °C for the 12 °C and 24 °C acclimation groups, respectively. In subsequent experiments, we tested the effects of high and low temperature acclimation on the food consumption and growth performance of two size groups of juveniles (28.7 ± 2.0 and 34.5 ± 2.9 mm, mean ± SD), that were reared at temperatures ranging from 14 °C to 23 °C. The optimal temperature for growth was 20 °C and did not differ between the acclimation temperatures or between the size groups. However, food consumption and growth performance were suppressed by acute temperature changes. Specifically, feeding and growth were lower in the 24 °C-acclimated group than in the 12 °C-acclimated group when exposed to 14 °C, which is close to the natural water temperature at release in the field. These results suggest that experienced thermal history does not affect the optimal temperature but can affect the growth performance of juveniles. To maximize the post-release growth of hatchery-reared juveniles, the influence of thermal history should be taken into consideration and acute thermal changes before release should be avoided., This study was partly supported by the Ministry of Agriculture, Forestry and Fisheries of Japan and by JSPS KAKENHI Grant Number 19K06207.

The present study aims to clarify the Seasonal bathymetric distributions of three coastal flatfishes (stone flounder, marbled flounder, and Japanese flounder) that are caught mainly by bottom trawls and gillnets off the coast of Fukushima, Japan, by using logbook data. All three species were found to have specific spawning depths, i.e., depths of 40–80 m, 20–40 m, and 10–60 m for stone, marbled, and Japanese flounders, respectively, with extremely high catch-per-unit-effort during their spawning seasons, reflecting spawning ground formation. Furthermore, Japanese flounder showed a tendency to expand their distribution offshore to depths deeper than 100 m after October. These results indicate interspecific variations in migration and aggregation patterns. Using logbook data and considering the seasonal catchability of each fishing gear enabled us to understand the seasonal bathymetric distribution of each species and the depths of their spawning grounds.

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., This study was partly supported by the Ministry of Agriculture, Forestry, and Fisheries of Japan., Electronic supplementary material: The online version of this article (doi:10.1007/s12562-016-1053-1) contains supplementary material, which is available to authorized users.

Off Fukushima, Japanese flounder (Paralichthys olivaceus) is a highly-valued species supporting coastal and offshore fisheries. We developed an age-structured population model incorporating seasonal coastal-offshore migrations to estimate and predict the abundance of Japanese flounder off Fukushima, where fishing has been restricted since the 2011 Fukushima Dai-ichi Nuclear Power Plant (FNPP) accident. We estimated the abundance of Japanese flounder using catch per unit effort from coastal gill net and offshore bottom trawl fishing from January 2000 to February 2011 and predicted the abundance under two different fishing effort scenarios (the same effort level as 2010 or decreased effort after the FNPP accident). Estimated abundance reflected the seasonal coastal-offshore migrations well, and it was estimated that abundance increased during and after 2007 because of high recruitments. In contrast, it was concluded that the predicted abundance on and after 2012 increased owing to the decreased fishing effort because the same estimated recruits were used in both scenarios. This indicates that the waters off Fukushima have effectively been serving as a marine protected area for Japanese flounder since the FNPP accident. This result was validated because almost all (83%) of the observed abundance index values calculated from a scientific bottom trawl survey during 2003–2014 were included within the estimated (predicted) 95% credible intervals of estimated (predicted) abundance index in the period. We also demonstrated the model's applicability for estimating the optimal fishing effort and age at first landing to maximize the earnings from gillnet and bottom trawl fisheries.

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.

Pleuronectid flatfish are considered visual day feeders, but their ability to feed at night has not been examined in the field. Juvenile (age-0) stone flounder Platichthys bicoloratus were collected, and their stomach contents were investigated in situ every 4 h over a 24-h period in an estuarine habitat to elucidate diel feeding periodicity. The weight of juvenile stomach contents was usually the highest around dusk and the main prey was bivalve siphons. To reveal whether juveniles feed only at particular times during the day or throughout a 24-h period, we conducted 24-h cage experiments in which 10 juveniles with empty stomachs were held in a cage for approximately 4 h (six trials). This experiment was carried out three times during different moon phases. Juveniles primarily ingested prey during the day, but 30% of fish that were caged at night also ingested prey. The number of successful captures by the caged fish was much greater during the day than that at night. These results indicate that stone flounder generally feed during the day and they may only feed at night under unusual situations, although they have the ability to capture prey at night. The mean daily ration estimated by diel changes in stomach content weight varied from 3.4% (95% confidence interval, 1.8–4.8%) to 13.2% (11.0–15.6%) of body weight between survey dates, indicating that daily food consumption by fish estimated from a single survey may be strongly biased.

Past studies indicated that newly settled juvenile Japanese flounder Paralichthys olivaceus depend on mysids as their main prey source, but little is known about the prey of juveniles in nursery grounds with a low density of mysids. This study aimed to reveal the annual variation in the main prey items of juvenile Japanese flounder in relation to their growth in southwestern Hiuchi-Nada, the Seto Inland Sea, Japan. Juvenile flounder consumed chiefly larval anchovy in 1995 and 1999 , while small crangonid shrimp Crangon uritai were the main prey items in 1998, 2003, and 2004. The growth rates of juvenile flounder ranged from 0.82–1.33 mm d − 1 during the five years of this study. Mysids were almost absent and small crangonid shrimp were abundant in the study area. Our results indicate that juvenile Japanese flounder prefer larval anchovy, but small crangonid shrimp function as the alternative prey when larval anchovy and mysids are not available in the study area.

A sudden outbreak of the parasitic sea spider Nymphonella tapetis accompanied by mass mortality of the Manila (asari) clam Ruditapes philippinarum was observed in Japan in 2007. It was unknown why dead and dying clams were found on the sand surface. In our laboratory experiment, in which sea spiders were artificially parasitised to host clams, unburied clams were significantly increased, suggesting that sea spider parasitism can change the burial mode of clams. We compared parasite loads, somatic condition and reburial activity of Manila clams among three burial groups (fully buried, partly buried and unburied) collected from the field. Unburied and partly buried clams had 30% lower soft body weight and 60% lower adductor strength as compared to the fully buried clams. Parasite prevalence and the mean infection intensity were greater in unburied and partly buried clams than in fully buried clams. Reburial depth was smaller in unburied and partly buried clams than in fully buried clams under laboratory conditions. Approximately 30% of the unburied and partly buried clams died during 30 days, whereas fully buried clams suffered no mortality. These results indicate that sea spider parasitism can reduce the burial depth and somatic condition of host clams, and eventually cause clam mortality on the sand.

We obtained the nucleotide sequence of 18S rDNA of Nymphonella tapetis, a pycnogonid endoparasitic on some bivalves, together with that of other species belonging to Ascorhynchidae Hoek, 1881. The phylogenetic tree based on these sequences as well as those of selected species from a database strongly supports the monophyly of Ascorhynchidae and the inclusion of Nymphonellain the family. Nymphonellaseems to be an aberrant form in the Ascorhynchidae, but multi-gene analysis with more species is required for the exact determination of the taxonomic position of the genus.