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Sakami T.,Tohoku National Fisheries Research Institute
Microbes and Environments | Year: 2011

Ammonia oxidization is the first and a rate-limiting step of nitrification, which is often a critical process in nitrogen removal from estuarine and coastal environments. To clarify the correlation of environmental conditions with the distribution of ammonia oxidizers in organic matter-rich coastal sediments, ammonia-oxidizing archaea (AOA) and bacteria (AOB) ammonia monooxygenase alpha subunit gene (amoA) abundance was determined in sediments of Matsushima Bay located in northeast Japan. The AOA and AOB amoA copy numbers ranged from 1.1×10 6 to 1.7×10 7 and from 7.1×10 5 to 7.6×10 6 copies g -1 sediment, respectively. AOA and AOB amoA abundance was negatively correlated with dissolved oxygen levels in the bottom water. AOA amoA abundance was also correlated with total phosphorus levels in the sediments. On the other hand, no significant relationship was observed between the amoA abundance and ammonium, organic matter (ignition loss), or acid volatile sulfide-sulfur levels in the sediments. These results show the heterogeneous distribution of ammonia oxidizers by the difference in environmental conditions within the bay. Moreover, AOA amoA diversity was relatively low in the area of high AOA amoA abundance, suggesting the variability of AOA community composition. Source

Kurita Y.,Tohoku National Fisheries Research Institute | Fujinami Y.,Fisheries Research Agency | Amano M.,Kitasato University
Fishery Bulletin | Year: 2011

The duration of spawning markers (e.g. signs of previous or imminent spawnings) is essential information for estimating spawning frequency of fish. In this study, the effect of temperature on the duration of spawning markers (i.e., oocytes at early migratory nucleus, late migratory nucleus, and hydrated stages, as well as new postovulatory follicles) of an indeterminate multiple-batch spawner, Japanese f lounder (Paralichthys olivaceus), was evaluated. Cannulation was performed to remove samples of oocytes, eggs, and postovulatory follicles in individual females at 2-4 hour intervals over 27-48 hours. The duration of spawning markers was successfully evaluated in 14 trials ranging between 9.2° and 22.6°C for six females (total length 484-730 mm). The durations of spawning markers decreased exponentially with temperature and were seen to decrease by a factor of 0.16, 0.36, 0.30, and 0.31 as temperature increased by 10°C for oocytes at early migratory nucleus, late migratory nucleus, and hydrated stages, and new postovulatory follicles, respectively. Thus, temperature should be considered when estimating spawning frequency from these spawning markers, especially for those fish that do not spawn synchronously in the population. Source

Saito H.,Japan National Research Institute of Fisheries Science | Aono H.,Japan National Research Institute of Fisheries Science | Aono H.,Tohoku National Fisheries Research Institute
Food Chemistry | Year: 2014

Phosphatidylethanolamine and phosphatidylcholine were major components in the foot lipids of the turban shell Turbo cornutus, while triacylglycerol was the major one in its viscera, which demonstrate the high level of lipid in all specimens. The major polyunsaturated fatty acids (PUFA) in the major lipid classes of T. cornutus were 20:4n-6 (arachidonic acid; ARA), 20:5n-3 (ecosapentaenoic acid; EPA), 22:4n-6, and 22:5n-3 (docosapentaenoic acid; n-3 DPA), with very low levels of 22:6n-3 (docosahexaenoic acid; DHA). The unusual high levels of ARA, 22:4n-6, and n-3 DPA found in both the triacylglycerols and phospholipids of all specimens suggest the influence of dietary algae on its tissue lipids. In the polar lipids, the total PUFA content was consistently high, with n-6 PUFA compensating for the fluctuation in the total n-3 PUFA levels. T. cornutus concentrated high levels of ARA in the visceral lipids from the dietary algae whose lipid content were very low. The viscera may effectively serve as a source of ARA for infant formulas. High levels of ARA, EPA, and n-3 DPA in the phospholipids of T. cornutus were observed. T. cornutus is a healthful marine food containing high levels of n-3 DPA. © 2013 Elsevier Ltd. All rights reserved. Source

Tamate T.,Tohoku National Fisheries Research Institute
Zoological Science | Year: 2015

Evolutionary ecologists often expect that natural and sexual selection result in systematic co-occurrence patterns of sex-biased mortality and sexual size dimorphism (SSD) within animal species. However, whether such patterns actually occur in wild animals is poorly examined. The following expectation, the larger sex suffers higher mortality, was primarily tested here for apparently native sea-run masu salmon (Oncorhynchus masou) in three populations in Hokkaido, Japan. Field surveys on sex ratios, body sizes, and ages of smolts and returning adults revealed that two of the three populations exhibited an expected pattern, a female-biased marine mortality and SSD, but one population demonstrated an unexpected co-occurrence of male-biased marine mortality and female-biased SSD. These female-biased SSDs were attributed to faster marine growth of females because of no sex difference in smolt body size. It has been previously suggested that breeding selection favoring large size generally act more strongly in females than in males in Japanese anadromous masu, as there is a weak sexual selection on adult males but universally intensive natural selection on adult females. Thus, this hypothesis explains female-biased SSDs well in all study populations. Interpopulation variation in sex-biased mortality found here might result from differences in marine predation and/or fishing pressures, given that selection driving female-biased SSD makes females forage more aggressively than males during the marine phase. Taken together, these results raise the possibility that evolutionary forces have shaped adaptive sex-specific foraging strategies under relationships between growth and mortality, resulting in co-occurrence patterns of sex-biased mortality and SSD within animal species. © 2015 Zoological Society of Japan. Source

A generalized method to accurately estimate the spawning fraction (S) of multiple batch spawning fish considering the duration of histological spawning markers over a wide range of ambient temperature, spawning time frequency distribution of the population, and sampling time was developed. The concept of the variable "fraction of the daily spawning females with spawning markers at a sampling time t (FDSM t)", which varies diurnally in relation to the duration of the spawning markers and the spawning time frequency distribution, was introduced. Spawning fraction can be calculated as S=Psm t×(1/FDSM t), where Psm t is the observed fraction of active females with signs of previous or imminent spawnings, referring to various spawning markers, at a sampling time t. Simulations suggested the following two methods were robust when the spawning time frequency distribution was long and uncertain. The first refers to sampling females evenly throughout the 24h period, whilst the second is based on selecting a single or combination of spawning markers so that the total temperature-adjusted marker duration at sampling sums to around 24h and applying, if necessary, a correction factor. With these methods, the influence of sampling time and spawning time frequency distribution can be ignored. The utility of the second method was evaluated with field data for Japanese flounder Paralichthys olivaceus. In all cases, accurate validation of the temperature-dependent duration of spawning markers is essential for accurate estimation of S. © 2011 Elsevier B.V. Source

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