Phenotypic changes in reproductive traits with changes in stock size of the starspotted smooth-hound Mustelus manazo in Tokyo Bay, Japan

Reproductive traits are among the primary determinants of population dynamics, and their changes could affect stock size. We investigated differences in reproductive traits of the starspotted smooth-hound Mustelus manazo in Tokyo Bay between the 1990s (a low-stock period) and the 2000s (a high-stock period). Peak timings of mating (May–July), ovulation (May–June), and parturition (May–June) were similar between the two periods. However, the size at first maturity in the 2000s was smaller than that in the 1990s for both sexes. In addition, embryo-related parameters differed greatly between the two periods. Slopes of size–fecundity regression in the 2000s decreased to 43–73 % of the 1990–1996 values, suggesting a substantial decline in fecundity during the 2000s. Frequency distribution of the maximum ovum diameter during the ovulation season showed two distinct two modes in 1990s while it showed a substantial dispersion during the 2000s, implying that changes occurred in the developmental pattern of ova in the ovary. Undeveloped eggs were present in the uteri with low frequency from September to May during the 2000s, but they were totally absent from September through May in the 1990s. The increased number of remnant undeveloped eggs that did not become embryos may explain the fecundity decline during the 2000s.     

Occurrence and distribution of settling and newly settled spotted halibut Verasper variegatus and Japanese flounder Paralichthys olivaceus in shallow nursery grounds around Shimabara Peninsula, western Japan

The occurrence and distribution of settling and settled spotted halibut Verasper variegatus were compared with those of Japanese flounder Paralichthys olivaceus in shallow habitats around Shimabara Peninsula, western Japan, to elucidate the settlement and recruitment characteristics of spotted halibut, a rare pleuronectid flatfish in Japan. Push-net sampling conducted at nine sites in March and April 2003 collected spotted halibut from four nurseries located at eastern areas of Shimabara Peninsula in Ariake Bay; Japanese flounder were sampled from eight nurseries. Comparison of microhabitat distributions in a tidal-flat nursery during February?CApril in 2003?C2007 revealed that metamorphosing larvae and juveniles of spotted halibut, which showed the drastic body coloration (black to brown) and behavioral changes (frequent swimming to settlement), were distributed mainly in the lower edge of the intertidal area, whereas Japanese flounder inhabited both intertidal and subtidal areas. Metamorphosing larvae of spotted halibut (12.6?C16.5?mm standard length; n?=?24) were collected in March when the highest densities were observed, whereas metamorphosing larvae of Japanese flounder (10.0?C15.9?mm, n?=?55) were observed during March?CApril. Our results suggest that spotted halibut has a narrower time/space window for recruitment to the specific nurseries compared with Japanese flounder.     

Growth behavior of suckers derived from transplanted sago palm (Metroxylon sagu Rottb.)

During the growth of sago palm (Metroxylon sagu Rottb.), primary suckers appear from the main stem (MS) of transplanted suckers. Then, secondary suckers appear from the primary suckers. After the MS (trunk) is first harvested 10 and several years after transplantation, trunks can be harvested persistently using the primary, secondary, and subsequent suckers, which are designated as derivative suckers, growing with the MS. However, little knowledge exists about the growth behavior of derivative suckers. This study clarified how derivative suckers, especially the primary and secondary suckers, spread in the horizontal direction, and how they form a plant with the MS during the creeping growth stage. Most derivative suckers crept in the direction of about 70° subtended by the mother stem. However, two primary suckers that appeared early after transplantation crept in an obtuse angle to the creeping direction of the MS. As the reason for this obtuse angle direction, we considered the following four factors: (1) the existence of petiole, (2) distance from the sucker to the ground surface, (3) enlargement of the MS, and (4) space for sucker growth. The growth behaviors of the two primary suckers and the other derivative suckers differed. Therefore, in sago palm cultivation, the two primary suckers which appeared first from the MS were very important for formation of the framework of the plant with the MS, in terms of efficient utilization of space for the growth of derivative suckers.     

Nucleotide polymorphism in the carrot late embryogenesis abundant gene DC8/ECP63

Carrot (Daucus carota) somatic embryogenesis has been extensively used as an experimental system for studying embryogenesis. In several plant species, late embryogenesis abundant (LEA) genes are reported as the embryogenesis-related genes that are specifically expressed in embryonic tissues. Several LEA genes have been isolated for carrot somatic embryogenesis. The carrot LEA genes DC8 and ECP63 have very similar nucleotide sequences, and the gene pair is likely to be a nucleotide polymorphism. In several carrot cultivars, plants in which only DC8 was detected (DD genotype), only ECP63 was detected (EE genotype), and both DC8 and ECP63 were detected (DE genotype) have been observed via genomic PCR. Furthermore, distinct frequencies of the genotypes were observed in some carrot cultivars. These results suggested that detection of the nucleotide polymorphism might be useful in defining carrot cultivars. In addition, DC8 and ECP63, which include 14 amino acid insertions/deletions and 21 amino acid substitutions, may have similar effects on somatic embryogenesis, as all genotypes (DD, DE, and EE) were detected in some embryogenic cell lines. Therefore, the nucleotide polymorphism may be a useful candidate polymorphic marker that is easily detectable by PCR.     

Does trade openness reduce a domestic fisheries catch?

Although trade liberalization may increase a country’s welfare, its specific effect on a country’s fishing industry has not been well studied. By decomposing the effect of international trade into four parts, i.e., scale-technique effects (ST), the indirect trade-induced composition effect (IC), the indirect effect of trade intensity through income (ITC), and the direct effect of trade intensity (DTC), this study empirically investigates the effect of trade openness on country-level fisheries production. To take into account the endogeneity of trade openness and income, we adopt the instrumental variable approach. We find that a rise in trade openness reduces fisheries catch on average. In particular, the long-run effect is large. This result implies that future production is affected by current overfishing through stock dynamics. Our decomposed elasticities indicate that the ST and ITC dominate in the trade elasticity of fisheries catch. While ST implies that overfishing would be affected by trade, ITC may either establish an “overfishing haven”, similar to a “pollution haven” in the environmental literature, or production shift of fisheries to countries with lax regulation to pass stringent regulation, which is more likely to occur in high-income countries.     

Interannual variation in quantitative relationships among egg production and densities of larvae and juveniles of the Japanese mantis shrimp <Emphasis Type="Italic">Oratosquilla oratoria</Emphasis> in Tokyo Bay,Japan

To explore which lifestages affect the stock size of young-of-the-year mantis shrimp Oratosquilla oratoria in Tokyo Bay, Japan, we investigated interannual variations in the quantitative relationships among egg production, larval density, and juvenile density. We collected adult females, larvae, and juveniles during monthly field surveys from 2004 to 2007. The interannual trend for the juvenile density index differed from those for egg production and larval density; although indices of both egg production and larval density were high in 2004 and 2007, the juvenile density index was high only in 2007, suggesting high mortality during the pelagic larval stage or the early phase of the postsettlement juvenile stage in 2004. We found that larval settlement started at the end of August and peaked in October, although larvae from the early spawning season (May–June) should have settled in August or earlier. Juveniles were found throughout the bay except in areas where bottom hypoxia occurred, suggesting that hypoxia restricts the spatial distribution of juveniles. Our results suggest that mortality during the early life history fluctuates among years, probably because of changes in environmental conditions in the bay, resulting in interannual variation in the stock size of young-of-the-year juvenile O. oratoria.     

Dietary utility of enzyme-treated fish meal for juvenile Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis>

ABSTRACT:   In order to develop an artificial diet, the dietary utility of enzyme-treated fish meal was investigated for juvenile Pacific bluefin tuna Thunnus orientalis (PBT). Diets containing each 63% of Chilean fish meal (FM), enzyme-treated Chilean fish meal (EC) and enzyme-treated Peruvian fish meal (EP), with 10% bonito oil and raw sand lance Ammodytes personatus (SL) were fed to juvenile tuna six times per day for one week. In a different trial, diets EC and SL were fed to tuna six times per day for 2 weeks. Only diet EC sustained similar growth or caused lower survival and higher feed efficiency, hepato- and enterosomatic indices and final carcass lipid content as compared to those of SL. Diets FM and EP led to lower specific growth rate (SGR) but similar feed efficiency, survival and hepatosomatic index, yet higher enterosomatic index. Moreover, PBT fed diet EC for 2 weeks led to similar growth performance but higher final carcass and hepatic lipid contents, and plasma cholesterol and phospholipid levels than those fed SL. Carcass fatty acid composition of diet EC group had lower 20:5  n -3 and 22:6  n -3 levels than the SL group. These results revealed that EC, as a suitable dietary protein source, could sustain growth of PBT, while dietary bonito oil led to higher carcass lipid but lower accumulation of n -3 highly unsaturated fatty acids.     

The first specific detection of a highly pathogenic avian influenza virus (H5N1) in Ivory Coast

The Virology Laboratory of the Central Laboratory of Animal Diseases in Ivory Coast at Bingerville received samples of wild and domestic avian species between February and December 2006. An RT-PCR technique was used to test for avian influenza (AI) and highly pathogenic AI subtype viruses. Among 2125 samples, 16 were type A positive; of which, 12 were later confirmed to be H5N1. Fifteen of these 16 type A positive samples were inoculated into the chorioallantoic cavity of 11-day-old embryonated hens' eggs for virus isolation. Eight produced virus with hemagglutination titres from 1/64 to 1/512. The 4/16 M-RT-PCR positive samples, which were H5N1 negative, were shown to be H7 subtype negative. The diagnostic efficiency of the laboratory for the surveillance of H5N1 in Ivory Coast was demonstrated. The positive cases of H5N1 were from a sparrowhawk (Accipter nisus); live market poultry and in free-range poultry, where the mortality rate was approximately 20% (2/10) and 96.7% (29/30) respectively. Currently, investigations into intensive poultry farms have proved negative for H5N1. No human cases have been reported this time.