Salinity intrusion and rice production in Red River Delta under changing climate conditions

This study was carried out to identify the vulnerability of rice production to salinity intrusion arising from climate change in Giao Thuy, a coastal district of Nam Dinh Province, located in Red River Delta in Vietnam. From the analysis of historical climate data at Nam Dinh city, both mean maximum and minimum temperatures increased by about 0.3 and 0.1 °C per decade, respectively, during the period of 1961–2010. Salt concentration of the river water was higher at the irrigation gate closer to river mouth (Con Nhat) than at the upstream gate (Ha Mieu), which generally increased from 2003 to 2012, with the average maximum concentration up to 2.13 % at Con Nhat gate in 2010. The salt water concentration in the riverside field outside the dyke reached 3.6 %, while among the fields within dyke the salinity was only 0.7 % at maximum in January 2013, and the values were higher in paddy fields close to the dyke than far from the dyke. Average yield among the selected 27 fields from 2011 summer to 2013 spring rice was higher in spring rice (748 g m^?2) but lower in summer rice (417 g m^?2) mainly due to unfavorable weather such as cold spell at flowering and flood at harvesting time. Rice yield was lowest in general in the most downstream commune Giao Thien, and was significantly lower in field located close to the dyke than those far from the dyke. This spatial variability of rice yield may not be directly attributable to salinity, but to the other factors such as shift of irrigation intake gate to further upstream and/or different management such as less input of N fertilizer and use of traditional local variety.     

Experimental analysis on the relationship between the population density of ayu Plecoglossus altivelis altivelis and fishery catch by “Tomozuri” angling

To investigate the relationship between the population density of ayu and the survival rate, number of ayu caught by “Tomozuri” angling and total fishery catch, ayu were introduced into experimental ponds with currents at densities of 1.1–6.1/m² in 2011 and 2012. After stocking in May, fishing was conducted from early July to late August or early September. The proportion of dead ayu in each pond was less than 20 % through the experiment and was not correlated with the initial density of ayu in either year. The growth rates of ayu that were fished and that remained in ponds to the end of the experiment were negatively correlated with the initial density. However, the number and catch of ayu fished by Tomozuri peaked at an initial density of 2.6–4.7/m². Medium- and large-sized ayu heavier than 30 and 50 g, respectively, caught by fishing peaked at initial densities of 2.6/m² and 2.1–2.6/m². These results suggest that the traditional criterion on the stock density of ayu, 0.6–0.7/m², is too low from the viewpoint of Tomozuri angling, and recent stock densities used in many prefectures, 0.5–2.0/m², are not sufficient.     

Effects of stratification and misspecification of covariates on species distribution models for abundance estimation from virtual line transect survey data

The aim of this study was to examine the effects of stratification of the survey region on the performance of species distribution models (SDMs) described by generalized linear models or generalized additive models when estimating school abundance by using a line transect survey. True covariates that define spatial school distribution are not always obtainable explanatory variables. When the true covariates differ from explanatory variables in the model, the explanatory variables are determined to be misspecified. We evaluated the performance of SDMs in abundance estimation with misspecified covariates by using dummy datasets for which the true abundance was known. Simulated replicates of spatial distributions of a whale school and sighting data were generated from possible scenarios motivated by the spatial school distribution of Antarctic minke whales Balaenoptera bonaerensis. This distribution was obtained from the Japanese Whale Research Program under Special Permit in the Antarctic. Our results showed that the relative bias of the abundance estimators was large when covariates were misspecified and a survey region was stratified. Although stratification of the survey region is intended to produce a conventional line transect estimator with a smaller variance than that of non-stratified survey region, it also acts to increase the bias of the abundance estimate obtained from SDMs.     

Validation of daily increment formation in otoliths of immature and adult Japanese anchovy <Emphasis Type="Italic">Engraulis japonicus</Emphasis>

In order to validate daily increment formation in otoliths of immature and adult Japanese anchovy Engraulis japonicus, three rearing experiments using chemical marking of otoliths were conducted on adult anchovy in summer 2004 and immature anchovy in summer 2005 and in winter 2006. In the two experiments conducted in summer, the number of otolith microincrements between alizarin complexone (ALC) marks showed that microincrements were formed daily. In the summer 2005 experiment, immature anchovy under conditions of reduced daily food rations also showed daily microincrement formation. Average increment width was 0.9 μm in adults and 1.8–3.1 μm in immature anchovy. In contrast, no clear increments were observed between ALC marks on the otoliths from the experiment in winter 2006, and scanning electron microscope (SEM) observations failed to confirm clear increment formation. We consider that low water temperatures (<13–14°C) restricted otolith growth and lowered the contrast between the discontinuous and the incremental zones of the otolith increments. For age estimation of Japanese anchovy, clear increments wider than about 1 μm in the otolith can be regarded as daily increments. However, daily age estimation of immature and adult anchovy that experience low water temperatures in winter may be difficult due to the obscurity of the increments.     

Mitigating sea turtle by-catch in coastal passive net fisheries

There is growing evidence that small-scale, coastal, passive net fisheries may be the largest single threat to some sea turtle populations. We review assessments of turtle interactions in these fisheries, and experiments on gear-technology approaches (modifying gear designs, materials and fishing methods) to mitigate turtle by-catch, available from a small number of studies and fisheries. Additional assessments are needed to improve the limited understanding of the relative degree of risk coastal net fisheries pose to turtle populations, to prioritize limited conservation resources and identify suitable mitigation opportunities. Whether gear technology provides effective and commercially viable solutions, alone or in combination with other approaches, is not well-understood. Fishery-specific assessments and trials are needed, as differences between fisheries, including in gear designs; turtle and target species, sizes and abundance; socioeconomic context; and practicality affect efficacy and suitability of by-catch mitigation methods. Promising gear-technology approaches for gillnets and trammel nets include: increasing gear visibility to turtles but not target species, through illumination and line materials; reducing net vertical height; increasing tiedown length or eliminating tiedowns; incorporating shark-shaped silhouettes; and modifying float characteristics, the number of floats or eliminating floats. Promising gear-technology approaches for pound nets and other trap gear include: replacing mesh with ropes in the upper portion of leaders; incorporating a turtle releasing device into traps; modifying the shape of the trap roof to direct turtles towards the location of an escapement device; using an open trap; and incorporating a device to prevent sea turtle entrance into traps.     

Diffusion tensor imaging-based quantitative analysis of the spinal cord in Pembroke Welsh Corgis with degenerative myelopathy

Canine degenerative myelopathy (DM) is a progressive neurodegenerative disease of the spinal cord. The diagnosis is based on the observation of clinical signs, genetic testing, and exclusion of other spinal cord diseases, and a definitive diagnosis of DM can only be confirmed by postmortem histopathological findings. The aim of this study was to investigate the diagnostic ability of diffusion tensor imaging (DTI) for DM. Eight DM-affected Pembroke Welsh Corgis, thirteen dogs with thoracolumbar intervertebral disk herniation (IVDH), and six healthy control dogs were included. All dogs were scanned using a 3.0-T MRI system. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were calculated for each intervertebral disk level slice between T8–T9 and L2–L3 intervertebral disk levels, and the entire area of the thoracolumbar spinal cord between T8–T9 and L2–L3 intervertebral disk levels (T8–L3 region). The ADC and FA values of the T8–L3 region were significantly lower in the DM group than in the IVDH group. The ADC values for the T8–L3 region had a moderate negative correlation with clinical duration (r_s= −0.723, P=0.043); however, the FA values of other intervertebral disk levels and T8–L3 region had no correlation with clinical durations. The measurement of DTI indices can be used to quantitatively assess neurodegeneration and may have diagnostic value for DM. In particular, the ADC value of the T8–L3 region may aid in making a non-invasive premortem diagnosis of DM.     

Otolith microstructure of brown sole <Emphasis Type="Italic">Pseudopleuronectes herzensteini</Emphasis>: validation of daily ring formation and the occurrence of microstructure denoting metamorphosis

Brown sole Pseudopleuronectes herzensteini larvae and juveniles were reared to validate daily otolith ring formation. At 15°C, a check (a distinct ring) formed on the sagittae and lapilli at 6 days after hatching, and clear increments regularly formed outside the check. For both otoliths, the relationship between the number of days after hatching and number of increments was linear, and the slope of the line was approximately 1; therefore, daily formation was validated. At 12°C, the check formed on the lapillus 8 days after hatching. Accessory primordia (AP) began forming on the sagittae of metamorphosing larvae, and the shape of the sagittae became complicated. AP were not formed on the lapillus; concentric rings were formed throughout larval and juvenile stages. Wide and obscure increments formed on the lapilli during metamorphosis (metamorphosing zone, MZ). Based on MZ, concentric rings that have formed on the lapilli of juveniles can be separated into larval and juvenile rings. The morphs of large juveniles’ lapilli were bilaterally asymmetric, and the blind-side lapilli were most suitable for otolith microstructure analysis. This study provides fundamental information for otolith microstructure analysis in wild brown sole.     

Growth suppression of human cancer cells by polyphenolics from sweetpotato (Ipomoea batatas L.) leaves

Sweetpotato leaves (Ipomoea batatas L.) contain a high content of polyphenolics that consist of caffeic acid, chlorogenic acid, 3,4-di-O-caffeoylquinic acid, 3,5-di-O-caffeoylquinic acid, 4,5-di-O-caffeoylquinic acid, and 3,4,5-tri-O-caffeoylquinic acid. We investigated the suppression of the proliferation of selected human cancer cells by phenolic compounds isolated from sweetpotato leaf. The human cancer cells used in this research included a stomach cancer (Kato III), a colon cancer (DLD-1), and a promyelocytic leukemia cell (HL-60). Caffeic acid and di- and tricaffeoylquinic acids dose-dependently depressed cancer cell proliferation, and the difference in sensitivity between caffeoylquinic acid derivatives and each kind of cancer cell was observed. Specifically, 3,4,5-tri-O-caffeoylquinic acid effectively depressed the growth of three kinds of cancer cells, and caffeic acid had an exceptionally higher effect against HL-60 cells than other di- and tricaffeoylquinic acids. In attempting to clarify the mechanism of growth suppression with the addition of the apoptotic inhibitor N-ethylmaleimide, we observed that the nuclear granulation in 3,4,5-tri-O-caffeoylquinic acid-treated HL-60 cells suggested apoptosis induction. This effect was confirmed by DNA fragmentation, an increase of caspase-3 activity, and expression of c-Jun. Growth suppression of HL-60 cells by 3,4,5-tri-O-caffeoylquinic acid was determined to be the result of apoptotic death of the cells. These results indicate that 3,4,5-tri-O-caffeoylquinic acid may have potential for cancer prevention.     

A provisional growth model with a size–density relationship for a plantation of <Emphasis Type="Italic">Paraserianthes falcataria</Emphasis> derived from measurements taken over 2 years in Pare,Indonesia

A growth model for a plantation of Paraserianthes falcataria was provisionally derived from measurements of 32 permanent plots taken over a period of 2 years in Pare, Indonesia. This model first predicts height growth with the polymorphic site index equation. Then density-related growth and mortality, that is, diameter and stand density, are calculated to satisfy the mathematical relationship for the reciprocal and self-thinning equations, both of which were based on the maximum size–density line with the slope of −1.759 identified in this study. Cumulative predictions on diameter and stand density, starting with each of three age classes, 3, 4, and 5 years after planting, and continuing for the next 2 years, agreed well with the observations of age-class mean. An exception was for stands that were 7 years old, which were marginal, but closest to the rotation age of 8 years. Contrasting height/diameter relationships among the three age classes were described reasonably well with this model, and the predicted basal growth area was found to agree fairly well with observations. These results suggest that the growth model presented here has good potential for applying size–density control for plantations of P. falcataria. However, measurements for an additional few years might be necessary to derive a model that will more accurately predict diameter size at the rotation age.