STARVATION TOLERANCE OF EARLY STAGE LAGUNCULA PULCHELLA (NATICIDAE)

The starvation tolerance of the moonsnail Laguncula pulchella was examined under nonfeeding conditions in the laboratory using individuals at the early stages of development, which comprised subadults (≤19 mm shell width) and newly hatched juveniles (≤1.7 mm). The newly hatched juveniles survived for ≤86 days at 20°C, ≤56 days at 25°C, and ≤22 days at 30°C, whereas subadults survived for ≤323 days at 20°C and ≤181 days at 30°C. These starvation tolerance ranges were relatively greater than those of other gastropods. There was a positive correlation between shell size and the duration of juvenile survival, indicating that the juveniles hatched at larger sizes have more energy stores. The high starvation tolerance of L. pulchella might be contributing to its invasion success in habitats with low prey availability.This study was partly supported by JSPS KAKENHI Grant (20H03062)

Temporal changes of the fish community in a seagrass bed after disappearance of vegetation caused by disturbance of the sea bottom and sediment deposition

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)

Fish fauna off sandy beaches, in an estuary, and in a seagrass bed in Hiroshima Bay, Seto Inland Sea

From February 2015 to January 2016, we collected fish monthly using a beach seine net at two sandy beaches (B1 and B2), in a muddy sand estuary (MS), and in a seagrass bed (SG) in Hiroshima Bay, western Japan. A total of 2920 fish in 50 species were collected. The number of species, individuals, and biomass (total weight) were greater at SG and MS than at B1 and B2. The numerically most dominant species were Favonigobius gymnauchen and Tridentiger trigonocephalus at B1 and B2, F. gymnauchen and Acentrogobius sp. 2 at MS, and Plotosus japonicus and Rudarius ercodes at SG. Fish diversity also was higher at MS and SG than at B1 and B2 throughout the year. Fish assemblages and their patterns varied between sites, indicating that each habitat plays an important role as the nursery ground for different fishes

Diel feeding rhythms, daily ration, and seasonal changes thereof in marbled flounder Pseudopleuronectes yokohamae

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 (<300 mm: 2.6%–3.2% body weight; ≥300 mm: 1.5%–2.5%) than in males (<300 mm: 1.7%–2.6%; ≥300 mm: 1.3%–1.9%). Seasonal surveys were also carried out, and the greater ration in females than males were consistent throughout the year, suggesting that greater growth in females than males attributes to the greater food intake of females. The ration was highest in June, especially for large individuals, although water temperature in June was lower than that in September. These results indicate that the amount of food intake is related to the annual life cycle of the marbled flounder.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

Implicit-correction-based immersed boundary-lattice Boltzmann method with two relaxation times

In the present paper, we verify the effectiveness of the two-relaxation-time (TRT) collision operator in reducing boundary slip computed by the immersed boundary-lattice Boltzmann method (IB-LBM). In the linear collision operator of the TRT, we decompose the distribution function into symmetric and antisymmetric components and define the relaxation parameters for each part.The Chapman-Enskog expansion indicates that one relaxation time for the symmetric component is related to the kinematic viscosity. Rigorous analysis of the symmetric shear flows reveals that the relaxation time for the antisymmetric part controls the velocity gradient, the boundary velocity, and the boundary slip velocity computed by the IB-LBM. Simulation of the symmetric shear flows, the symmetric Poiseuille flows, and the cylindrical Couette flows indicates that the profiles of the numerical velocity calculated by the TRT collision operator under the IB-LBM framework exactly agree with those of the multi-relaxation time (MRT). The TRT is as effective in removingthe boundary slip as the MRT. We demonstrate analytically and numerically that the error of the boundary velocity is caused by the smoothing technique using the delta function used in the interpolation method. In the simulation of the flow past a circular cylinder, the IB-LBM based on the implicit correction method with the TRT succeeds in preventing the flow penetration through the solid surface as well as unphysical velocity distortion. The drag coefficient, the wake length, and the separation points calculated by the present IB-LBM agree well with previous studies at Re =10, 20, and 40

Effects of water temperature on feeding and growth of juvenile marbled flounder Pseudopleuronectes yokohamae under laboratory conditions: evaluation by group- and individual-based methods

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

Genetic relationships and expected responses for genetic improvement of carcass traits of Berkshire pigs

The Berkshire pig (Sus domestica L.) breed has thin muscle fibers and excellent water-holding capacity. The Berkshire meat makes it widely accepted in the Japanese premium pork market. This study evaluates the accuracy of improving carcass quality with the use of live animal records of Berkshire pigs. Traits analyzed in live animals were: body weight at 60 days of age (W60), age at finish (AGF), daily weight gain from birth to finish (DG), back fat thickness at finish (BFTF), and loin eye area at finish (LEAF), and in carcasses were: carcass weight, loin eye area (LEA), and subcutaneous fat thickness (SCF) at some points, using the records of 4,773 purebred Berkshire pigs. Variance components for the traits were estimated according to the animal model by the Restricted Maximum Likelihood (REML) procedure using the VCE6 program (Neumaier and Groeneveld, 1998). Correlated responses were also calculated. Genetic correlations of back fat thickness (BFT) in live animals with SCF in slaughtered animals were strong, whereas that of LEA between live and slaughtered animals was low. The expected gains by actual selection including W60 and BFTF as selection criterion were superior to other selections. Therefore, selection of live animals at an early stage of growth would be conducive to the production of high quality meat

IMMERSED BOUNDARY-FINITE DIFFERENCE LATTICE BOLTZMANN METHOD USING TWO RELAXATION TIMES

ABSTRACT It is known that velocity fields computed by using an immersed boundary-lattice Boltzmann method (IB-LBM) with a single-relaxation time (SRT) show unphysical distortion when the relaxation time, τ, is high. The authors proposed an immersed boundary-finite difference lattice Boltzmann method (IB-FDLBM) using SRT to predict liquid-solid flows. In simulations with IB-FDLBM, numerical errors in the velocity fields appear as in IBLBMs when τ is high. A two-relaxation time (TRT) collision operator is therefore implemented into IB-FDLBM in this study to reduce numerical errors at high τ. Simulations of circular Couette flows show that the proposed method gives accurate predictions at high τ, provided that the magic parameter, which is a function of the relaxation times, is less than unity. In addition, predicted drag coefficients of a circular cylinder and a sphere at low Reynolds numbers show reasonable agreements with theoretical solutions and measured data

Critical Population Trend of the Small-scale Sillago Sillago parvisquamis (family Sillaginidae) at Nakatsu Tidal Flat, Suo-nada Sea, Western Seto Inland Sea, Japan, 2016-2018

キス科の絶滅危惧種アオギスSillago parvisquamis について，最大の生息地である瀬戸内海周防灘南部（豊前海）の大分県中津干潟において2016 ～ 2018年の繁殖期に緊急調査を実施し，本種の生息状況や年齢構成などを明らかにした。2016年，2017年，および2018年の釣CPUE（個体数/3 時間/ 人；平均値±標準偏差）は，それぞれ0.80 ± 1.3（n＝13），4.3 ± 2.9（n＝18），および0.33 ± 0.65（n＝9）の低値を示した。依然として，繁殖活動が認められるものの，個体数の減少は著しく，危機的な生息状況にあることが明らかになった。The small-scale sillago Sillago parvisquamis (family Sillaginidae) has been evaluated as one of the endangered species in Japan. The only largest local population exists at Nakatsu tidal flat in the southern part of the Suo-nada Sea (Buzen-kai Sea), Seto Inland Sea. The population structure of the species on the tidal flat was investigated in 2016-2018 to determine recent population trends. As a result, no dominant year class was observed in the population. Catch per unit effort (CPUE) (indiv./3 hours/person; mean ± SD) by rod and line fishing during the spawning seasons in 2016, 2017 and 2018 showed low values, at 0.80 ± 1.3 (n = 13), 4.3 ± 2.9 (n = 18) and 0.33 ± 0.65 (n = 9), respectively. Histological examination of ovaries of the females captured in 2018 indicated that spawning had occurred as yet. These findings suggest that the small-scale sillago stock has decreased to a critical level in Japan