Severe oxidative stress is thought to be a principal cause of jaundice of yellowtail Seriola quinqueradiata

The jaundiced yellowtail Seriola quinqueradiata had yellow discolored skin and hyperbilirubinemia. Histology revealed that hemosiderin and ceroid occurred in the spleen. In the vascular system, there were vasculitis and sinusoidal dilatation. Hepatic cells showed degenerative figures with pyknotic or karyolytic nuclei, basophilic cytoplasm, cytoplasmic vacuoles in various sizes, and ceroidosis. In the bile duct system, however, there was no noticeable change. Hemoglobin contents of jaundiced fish were similar to those of control fish. Plasma taurine levels of jaundiced fish were significantly lower than those of control (p0.05). Judging from 2-thiobarbituric acid reactive substance values, in vivo lipid peroxidation progressed in the liver of jaundiced fish. In the plasma of jaundiced fish, contents of unconjugated bilirubin were significantly higher than those of conjugated bilirubin. A large amount of substance Xs, breakdown products of bilirubin scavenging active oxygen species, existed in the plasma of jaundiced fish. Therefore, jaundiced fish may suffer from severe oxidative stress, which might be a principal cause of jaundice. Liver superoxide dismutase and glutathione peroxidase activities of jaundiced yellowtail were significantly lower than those of controls.     

Spatial and seasonal variations of radiocesium concentrations in an algae-grazing annual fish,ayu Plecoglossus altivelis collected from Fukushima Prefecture in 2014

Fisheries Science - To elucidate spatial and seasonal variations of radiocesium (134Cs and 137Cs) concentrations in ayu Plecoglossus altivelis, amphidromous fish samples were collected both from...     

Formaldehyde adsorption by karamatsu (Larix leptolepis) bark

Formaldehyde adsorption and release tests of karamatsu (Larix leptolepis) bark and bark ingredients were performed. Karamatsu bark had good formaldehyde adsorption ability that was better than microcrystalline cellulose. An acetone-soluble fraction from karamatsu bark, which might contain bark tannin, had excellent formaldehyde adsorption ability, and was found to release a trace amount of the adsorbed formaldehyde, suggesting that its formaldehyde adsorption was predominantly due to chemical adsorption. It was confi rmed that the acetone-soluble fraction played an important part in formaldehyde adsorption by karamatsu bark. An acetone-insoluble fraction from karamatsu bark had good formaldehyde adsorption ability as well as the bark, in spite of the residue after the removal of the acetone-soluble fraction.     

Mechanism of formaldehyde adsorption of (+)-catechin

The reaction of (+)-catechin with formaldehyde vapor was investigated as a model reaction of formaldehyde adsorption of (+)-catechin. It was found by H nuclear magnetic resonance spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and gel permeation chromatography of the product that the vapor reaction of (+)-catechin with formaldehyde without a solvent or a catalyst proceeds via methylolation, condensation, and polymerization. This is the same as the reaction in a solvent in the presence of an acid or a base. The formation of polyoxymethylenes such as paraformaldehyde was not confirmed.     

Reproductive biology of male skipjack tuna <Emphasis Type="Italic">Katsuwonus pelamis</Emphasis> (Linnaeus) in the tropical western and central Pacific Ocean

The reproductive biology of male skipjack tuna Katsuwonus pelamis was examined from May 2005 to December 2007 in the tropical western and central Pacific Ocean. Testis maturity was classified into five stages (i.e., immature, early maturation, mid maturation, late maturation, and regression) on the basis of morphological changes in the germinal epithelium. The testis duct system (TS), which was characterized by lobules that lack spermatocysts, store only sperm, and form an anastomosing network, was located under the main sperm duct. The TS was observed at all stages of maturity except the immature stage, and first appeared in individuals with a fork length (FL) of 38–40 cm. The estimated minimum size at first maturity was 35.5 cm FL and the size at 0.5 maturity was 40.7 cm in FL. It was difficult to clearly differentiate the testis maturity stage based solely on the gonad index (GI) class because each GI class contained mature fish. Monthly changes in testis height index and GI did not follow a seasonal cycle. Mature individuals dominated throughout the year. These results imply that male skipjack tuna in this area showed evidence of spawning activity throughout the year without a clear seasonal pattern.     

Seasonal potential fishing ground prediction of neon flying squid (Ommastrephes bartramii) in the western and central North Pacific

We explored the seasonal potential fishing grounds of neon flying squid (Ommastrephes bartramii) in the western and central North Pacific using maximum entropy (MaxEnt) models fitted with squid fishery data as response and environmental factors from remotely sensed [sea surface temperature (SST), sea surface height (SSH), eddy kinetic energy (EKE), wind stress curl (WSC) and numerical model‐derived sea surface salinity (SSS)] covariates. The potential squid fishing grounds from January–February (winter) and June–July (summer) 2001–2004 were simulated separately and covered the near‐coast (winter) and offshore (summer) forage areas off the Kuroshio–Oyashio transition and subarctic frontal zones. The oceanographic conditions differed between regions and were regulated by the inherent seasonal variability and prevailing basin dynamics. The seasonal and spatial extents of potential squid fishing grounds were largely explained by SST (7–17°C in the winter and 11–18°C in the summer) and SSS (33.8–34.8 in the winter and 33.7–34.3 in the summer). These ocean properties are water mass tracers and define the boundaries of the North Pacific hydrographic provinces. Mesoscale variability in the upper ocean inferred from SSH and EKE were also influential to squid potential fishing grounds and are presumably linked to the augmented primary productivity from nutrient enhancement and entrainment of passive plankton. WSC, however, has the least model contribution to squid potential fishing habitat relative to the other environmental factors examined. Findings of this work underpin the importance of SST and SSS as robust predictors of the seasonal squid potential fishing grounds in the western and central North Pacific and highlight MaxEnt's potential for operational fishery application.     

Solar and lunar influences on the spawning activity of Pacific bluefin tuna (Thunnus orientalis) in the south‐western North Pacific spawning ground

Pacific bluefin tuna (Thunnus orientalis) migrate to the south‐western North Pacific spawning grounds (area off Taiwan and the Ryukyu Islands) from mid‐April to early July. Reproductive traits of the species in this area have been studied for some time; however, temporal changes in spawning activity during this season are not well understood. In this study, the spawning fraction (proportion of females with post‐ovulatory follicles to total mature females) in relation to solar calendar date and lunar day was investigated using a generalized linear model. Sampling was conducted almost every day throughout the fishing season at Ishigaki Fishing Port (24°21′N, 124°09′E), southern Japan between 2012 and 2014, and a total of 212 ovaries were histologically observed. Spawning fraction continued to increase from the beginning to the end of the season. This indicates that the peak season of occurrence in the area and the peak of spawning activity did not co‐occur. Spawning fraction also changed with the lunar day and significantly increased around the new moon. Eggs and early larvae hatched around the new moon may have reduced the predation risk during night‐time. These findings improve the current knowledge of reproductive biology and resource evaluation of Pacific bluefin tuna and indicate that spawning activity is not constant, and has two or three peaks in each season.     

Correction to: Spatial and seasonal variations of radiocesium concentrations in an algae-grazing annual fish,ayu Plecoglossus altivelis collected from Fukushima Prefecture in 2014

Fisheries Science - In the original publication the caption of Fig.&nbsp;6a and 6b is incorrectly published.