Length-weight relationship of pond-raised milkfish in the Philippines

Milkfish from culture ponds were measured in the provinces of Bataan, Iloilo, and Pangasinan over the period December 28th, 1970, to November 9th, 1971. The overall length-weight relationship was computed from 6 304 measurements giving the equation: log W = ?5.0463 + 2.98895 log L, where W = weight in g and L = total length in mm. A table is presented giving calculated weights for milkfish in the length range 80–400 mm, which can be used to compute relative condition factors. Data were grouped according to lengths, province, food system, and months for separate comparisons.     

Origin of the diclidophorid monogenean Neoheterobothrium hirame Ogawa, 1999, the causative agent of anemia in olive flounder Paralichthys olivaceus

In the mid-1990s, Neoheterobothrium hirame suddenly appeared as a new species in olive flounder Paralichthys olivaceus in Japanese coastal waters. Anemia caused by the parasite has prevailed in wild and cultured populations of olive flounder since that time. In this study, to clarify the origin of N. hirame, two Neoheterobothrium species, namely unidentified Neoheterobothrium species (tentatively abbreviated as Neoheterobothrium sp. PL) and N. affine, were collected from Paralichthys lethostigma and Paralichthys dentatus, respectively, off the east coast of North America and compared with N. hirame collected in Japan. No substantial differences were detected in the morphology and DNA sequences of ITS1-5.8S rRNA-ITS2 and mitochondrial cytochrome oxidase subunit I (mt COI) regions between N. hirame and Neoheterobothrium sp. PL. On the other hand, the congeneric N. affine was clearly distinguished from both N. hirame and Neoheterobothrium sp. PL in its longer isthmus and the DNA sequences in ITS1 and mt COI. The absence of differences between N. hirame and Neoheterobothrium sp. PL and the clear difference between both of these and N. affine indicate that N. hirame is conspecific with Neoheterobothrium sp. PL infecting P. lethostigma and that N. hirame was recently introduced from North America to Japan.     

Diversity of denitrifying bacteria in the greenwater system of coastal aquaculture

Greenwater technology is based on integrating finfishes inside pens for zero water exchange system of shrimp aquaculture. Nitrogen transformation could be improved by rearing euryhaline finfishes like grey mullet, milkfish which have a broad diet and tolerate poor water quality. The abundance of four denitrifying functional genes coding for nitrate reductase (narG and napA), nitrite reductase (nirS), nitric oxide reductase (qnorB) and nitrous oxide reductase (nosZ) has been examined in the greenwater system through a metagenomic approach. Phylogeny revealed homology of narG clones with uncultured environmental clones, whereas napA clone sequences were found to have homology with cultured (Stappia aggregata) and uncultured microorganisms. The nirS clones show uniqueness with Marinobacter hydrocarbonoclasticus, Aromatoleum aromaticum, and Ruegeria pomeroyi. The qnorB gene has been reported for the first time from culture systems along the Indian coast and clone exhibited 84–87 % identity with different uncultured bacteria. The nosZ clones are closely affiliated with S. aggregate and alpha bacterium. This study revealed denitrifying diversity from a greenwater system which could eventually be used in planning the future strategy for comprehending nitrogen fluxes, greenhouse gases and their mitigation in coastal aquaculture systems.     

A method for predicting the occurrence of paralytic shellfish poisoning along the coast of Hokkaido in the Okhotsk Sea in summer

To design a method for predicting outbreaks of paralytic shellfish poisoning (PSP) in scallop fishing grounds, the relationship between the distribution of the toxic dinoflagellate Alexandrium tamarense and the dynamics of the Soya Warm Current (SWC) was examined in the Okhotsk Sea off Hokkaido. Surveys were conducted from May to June to clarify the transportation mechanism of A.?tamarense from the oceanic area to the coastal area. The sea-level difference (SLD) between Wakkanai and Abashiri was monitored as an index of the strength of the SWC southeastward flow in an alongshore belt to examine the possible occurrence of A.?tamarense in the coastal area during temporal weakening of the SWC. A bottom-mounted acoustic Doppler current profiler (ADCP) was used for direct observations of the SWC. The results indicated that PSP occurred when low-salinity water contaminated with A.?tamarense extended to the coast during temporal weakening of the SWC due to a decrease of the SLD. Our results strongly indicate that predictions can be realized by monitoring the decrease of SLD as an index of temporal weakening of the SWC after surveys of the distribution of A.?tamarense in the oceanic area before the period of PSP occurrence.     

Comparison of aspects of the reproductive biology of Pomadasys,Otolithes and Pampus spp. in Kuwaiti waters

Aspects of the reproductive biology of Pomadasys argenteus, Otolithes argenteus and Pampus argenteus are described. Maturation of the gonads is divided into 8 arbitrary stages, and the distribution of the stages in an annual cycle is reported. In Pomadasys argenteus there is a major spawning period from February to April and another minor one in October. In Otolithes argenteus there is one distinct spawning period from January to April. The spawning season of Pampus argenteus extends from March to August. The histology of the gonads and the distribution of oocytes of different diameters in the ovaries of the 3 fish species are described. The distribution of oocyte diameters in the ovary of Pampus argenteus is polymodal and characteristic of serial spawners, whereas the distribution of oocyte diameters in Pomadasys argenteus and Otolithes argenteus corroborate the finding that these fish are single spawners. The estimated potential fecundity for Pomadasys argenteus ranged from 6 25 848 to 2 424 846, for Otolithes argenteus from 53 676 to 7 163 954 and for Pampus argenteus from 765 675 to 2 537 774.     

Observations on the use of Furanace for the control of vibrio disease in marine flatfish

Minimum inhibition concentrations (MICs) were determined for Furanace (Dainippon Pharmaceutical Co. Ltd.) against 17 strains of pathogenic vibrios isolated from marine fish and salmonidae. All the strains tested were sensitive to Furanace, the highest MIC being 3.1 μg/ml for one strain and the remainder being < 1.6 μg/ml. Plaice (Pleuronectes platessa L.), Dover sole (Solea solea (L.)) and brill (Scophthalmus rhombus (L.)) rapidly took up Furanace from low-concentration baths (5–10 μg/ml) at 9.5–11.5°C. Uptake varied between species at these temperatures and in most cases blood levels above 1 μg/ml were achieved after 1 hour's exposure. Two hours after exposure over 70% of the Furanace had been eliminated from the blood.     

Evaluation of the pigmentation stages and body proportions from the glass eel to yellow eel in Anguilla japonica

The pigmentation stages of Anguilla japonica were classified from the glass eel to yellow eel stage using 412 wild-caught eels from Hamana Lake and detailed developmental observations of 10 laboratory-reared eels. The sequential appearance of pigment was similar to that in A. anguilla, except for delayed pigment formation on the nerve cord of A. japonica. The general classification of pigmentation stages (V_A–VI_B) in A. anguilla was applicable to A. japonica, but the V_B stage could be separated into two stages (V_B1, V_B2) in A. japonica. The completion of guanine deposition on the intra-abdominal membrane may be a trait to discriminate the yellow eel stage (VII) from the VI_B stage. In natural conditions, wild-caught 0-age eels (n = 3,298) did not increase in size and retained a slender body form until VI_A4, and then became thicker during VI_B. The transition between body forms and growth may correspond to their ecological change from using passive transport in glass eels with tidal flow into rivers, to their settlement and further movements of elvers upstream. Considering this behavioral transition and pigmentation progression, it is proposed that the terms "glass eel" and "elver" could be defined as stages V_A–VI_A4 and VI_B, respectively.     

Spawning per recruit analysis of the pelagic thresher shark,Alopias pelagicus,in the eastern Taiwan waters

The pelagic thresher shark, Alopias pelagicus, is a cosmopolitan species and abundant in Taiwan waters. Some of its biological information has been documented yet its population dynamics are poorly known. The purpose of this study is to assess the pelagic thresher shark stock status in the eastern Taiwan waters. The whole weights (W) of 51,748 individuals of the pelagic thresher shark landed at Nanfanao and Chengkung fish markets, eastern Taiwan from 1990 to 2004 were converted to precaudal length (PCL) based on the W–PCL relationship (W = 2.25 × 10⁻⁴ × PCL^2.533, n = 2165). The sexes combined VBGE L_t = 189.5 × (1 − e^{−0.10(t+6.47)}) was used to estimate the age for each length group. Total mortality rates (Z) obtained with length-converted catch curves ranged from 0.208 to 0.277 year⁻¹. Natural mortality rate (M) estimated from Hoenig method was 0.132 year⁻¹, and exploitation rate (E) ranged from 0.069 to 0.127 for 1990–2004. Annual abundance was estimated to range from 97,551 in 2000 to 153,331 in 2003 from virtual population analysis, and the highest fishing mortality occurred in ages 8–18 years. There were four different scenarios being simulated in this study. Scenario 1 indicated that spawning per recruit (SPR) ranged from 23.07% in 2001 to 47.71% in 1990 with a mean of 36.41% for the period of 1990–2004. The mean SPR of pelagic thresher for 1990–2004 was below the BRP of SPR = 35% in scenarios 2–4 suggesting that this stock was slightly overexploited. Therefore, to ensure sustainable utilization of this stock, reduction of fishing effort and close monitoring on A. pelagicus are needed.     

Genetic population structure of the bigeye tuna Thunnus obesus in the central Pacific Ocean based on mtDNA Cytb sequences

Bigeye tuna Thunnus obesus is considered an important fishery species around the world. There is no adequate genetic data available for the T. obesus population. Polymorphism of sequence variations in mitochondrial Cytb genes were assessed to explore the level of genetic variability and differentiation among eight populations of T. obesus sampled from the central Pacific Ocean. Overall, a total of 44 mtDNA haplotypes and 26 variable sites were detected in the 686 bp segment of mtDNA Cytb gene. Nucleotide diversity ranged from 0.17 to 0.27 % and the haplotype diversity ranged from 0.604 to 0.793. An analysis of molecular variance (AMOVA) test of bigeye tuna revealed that 99.38 % of the genetic variation occurred within populations. Both the maximum likelihood tree and the haplotype network indicated that two lineages of bigeye tuna coexisted in the central Pacific Ocean. Hierarchical AMOVA tests and pairwise analysis revealed no geographical isolation among haplotypes within the two lineages. High Nm values from this investigation indicated high rates of gene flow between the two sampling regions. Furthermore, tests of neutrality and mismatch distribution suggested that T. obesus might have experienced a population expansion, one that possibly occurred 110,000 years ago. Our study firstly unraveled the population genetic structure of the T. obesus in the central Pacific Ocean, and addressed the related fishery management issues including fishery stock identification, management, and conservation.     

Age and maturation of jack mackerel Trachurus japonicus in the East China Sea

Growth and reproductive characteristics of jack mackerel Trachurus japonicus collected in the East China Sea were determined based on otolith readings and gonad histology, respectively. Translucent and opaque zones on sectioned otoliths were identified and opaque rings counted. Von Bertalanffy growth parameters did not significantly differ between males and females, and the combined growth curve was: L _t  = 401{1 ? exp[?0.275 (t + 1.149)]} (0.8 < t < 6.9), where L _t is fork length (mm) at age t. The calculated lengths at age 1 in our study were larger than those reported 50 years ago from the East China Sea. The spawning period was evaluated to be from December to June, but primarily from February to May, based on the monthly changes in the gonadosomatic index and histological observations. The minimum size and age at first maturity were smaller and younger, respectively, than those reported in previous studies.     

Analysis of plasmids encoding the histidine decarboxylase gene in Tetragenococcus muriaticus isolated from Japanese fermented seafoods

In order to analyze the genes related to histamine production in halophilic lactic acid bacteria, 16 strains of histamine-producing bacteria were isolated from three fermented seafoods produced in the Hokuriku region of Japan. Phenotypic and 16S rRNA gene sequence analyses identified all of the strains as those of Tetragenococcus muriaticus. Pyruvoyl-dependent histidine decarboxylase gene (hdcA) was determined from all strains using the PCR method with an hdcA-specific detection primer set. Genetic analyses (Southern blot and restriction fragment length polymorphism analysis) of hdcA and genes related to histamine production (the hdc cluster) confirmed that all of the strains harbored 21–23 kbp plasmids encoding a single copy of hdcA. The four representative strains were selected based on isolation source and genetic analysis, and subsequently full sequences of plasmids harbored in these strains were determined. hdc cluster sequences from the plasmids showed very high similarity (>99 %) to known hdc clusters of T. halophilus, Lactobacillus hilgardii 0006, and other lactic acid bacteria. The structures of the plasmids, the replication region, the hdc cluster, and the plasmid maintenance system were conserved between the plasmids present in new isolates and the T. halophilus strains. These results indicate that plasmids encoding hdcA are widely distributed among T. halophilus and T. muriaticus and function in both species.     

Use of parasites as tags in delineating stocks of Atlantic cod (Gadus morhua) from the southern Gulf of St. Lawrence and the Cape Breton Shelf

Parasites were inventoried on and in 470 Atlantic cod (Gadus morhua) collected from the southern Gulf of St. Lawrence, NAFO (North Atlantic Fisheries Organization) division 4T, and Cape Breton Shelf (NAFO subdivision 4Vn) in September of 2004 and 2005, and August 2006, respectively. Forward stepwise discriminant function analysis (DFA) of the 4T samples indicated that the nematodes, Hysterothylacium aduncum, and Pseudoterranova decipiens and the acanthocephalans Echinorhynchus gadi and Corynosoma strumosum were significant in the classification of cod to eastern or western 4T. Cross-validation yielded a classification efficiency of 74% overall, thereby supporting the findings of earlier mark-recapture studies which have indicated that 4T cod are comprised of discrete eastern and western spawning groups. Further analyses indicated that western 4T cod was distinct not only from eastern 4T cod, but also differed from cod from the Smokey Channel and Cape Breton Shelf slopewaters (4Vn), with rates of misclassification ranging from 6% to 9%. Hence, “parasite tags” may prove useful for monitoring the exploitation of cod from western 4T during their annual migration through the Cabot Strait and while over-wintering along the edge of the Cape Breton Shelf where mixing with eastern 4T and 4Vn cod may occur. Similar results could be achieved with migrant cod from eastern 4T through analyses of parasite markers together with host meristic or morphometric parameters.     

Comparison of growth and pearl production in males and females of the freshwater mussel, Hyriopsis cumingii, in China

Growth and pearl production were compared for males and females in the freshwater mussel, Hyriopis cumingii, from a full-sib family. The results indicated that there was no significant difference (p > 0.05) on individual weight between male and female mussels of 1- or 2-year-old, while significant difference (p < 0.01) lay among 3- or 4-year-old mussels with male greater than female. The average shell width of the male mussels was less than that of the female individual (p < 0.05). 1- and 2-year-old males and females did not differ significantly with respect to the total weights, grain weights, or grain sizes of the pearls they produced, but these three parameters were all significantly greater in 3- and 4-year-old males (p < 0.05). The round pearl percent were similar between male and females at ages 1, 2, 3 and 4 years. Male and female mussels were separately and mixed cultured in enclosures, respectively. The rates of growth in shell width and body weight of females separated from males were 3.42 and 4.16 %, respectively, higher than in females mixed with males (p < 0.05). The total pearl weight per mussel, the average weight per pearl, and the average pearl size of females separated from males were 6.61, 7.10, and 3.59 %, respectively, greater than in females mixed with males (p < 0.05). There was no significant difference in the growth rate or pearl yield of males cultured with or without females (p > 0.05). Under traditional culture methods, male mussels have a better pearl performance, and artificial separation of females from males can improve the growth and pearl production of female mussels.     

Species diversity of the marine diatom genus Skeletonema in Japanese brackish water areas

The genus Skeletonema includes phytoplankton species that are important primary producers in marine food chains. Brackish waters have been reported to be one of the important habitats of some species of Skeletonema. To elucidate the species diversity of Skeletonema in brackish waters, we investigated three Japanese brackish bodies of water: the coastal waters of Toyama Bay, a tidal area of the Chikugo River, and a constructed reservoir in Isahaya Bay. We used molecular analysis based on large subunit rDNA and fine morphological structure to identify species. Skeletonema costatum s.s. (sensu stricto) was isolated at salinities as low as 0.6, but Skeletonema dohrnii, Skeletonema subsalsum, and Skeletonema tropicum were not found at salinities below 11.0. S. costatum s.s. could survive transfer from a medium with a salinity of 15 to a salinity of 2, but S. dohrnii did not survive in the same experiment. Only S. costatum s.s. germinated from the sediment of a reservoir in which the salinity was 0.1–1.4; incubation conditions included temperatures of 10, 15, 20, 25, and 30 °C and salinities of 5 and 30. Skeletonema costatum s.s. was identified as the species most adaptable to low-level salinity variations throughout its lifecycle.     

A new system for bottom co-culture of the scallop,Patinopecten yessoensis,with the sea cucumber,Apostichopus japonicus,and the sea urchin,Anthocidaris crassispina,in shallow water in China

A new system for bottom co-culture of scallop, Patinopecten yessoensis, sea cucumber, Apostichopus japonicus (Selenka), and sea urchin, Anthocidaris crassispina, is reported. To evaluate the system, scallops (average shell height, 3.904 ± 0.511 cm) were placed in nine “Hailong” units at densities of 10, 30, and 50 individuals per cell (ind/m²), and the units were placed in shallow waters with a muddy, sandy, or semi-sandy seabed. After more than 9 months, the scallops cultured on the semi-sandy seabed were larger than those cultured on sandy or muddy seabed (p < 0.05). The index of the adductor muscle was higher for scallops cultured on the sandy seabed than for those cultured on semi-sandy or muddy seabed (p < 0.05). More sea cucumbers were harvested from the units on the sandy seabed than from those on semi-sandy or muddy seabed (p < 0.05). The highest yield of sea urchins was from units on the muddy seabed, followed by those on the semi-sandy seabed and then from those on the sandy seabed (p < 0.05). Seaweed communities developed on the units located on sandy seabeds.     

黄河入海泥沙年际通量对莱州湾渔业资源结构的影响

根据2009年8月-2013年8月莱州湾海域渔业拖网调查数据,分析该海域渔业种群组成、优势种、空间分布和资源量的年际变动,以了解黄河入海泥沙通量对莱州湾渔业结构的影响.结果表明:(1)莱州湾渔业资源量整体呈下降趋势,主要以鱼类为主,甲壳类次之,头足类最少;鱼类中以中上层鱼类为主,网获量明显多于底层鱼类,但2011年8月底层鱼类稍多于中上层鱼类;(2)莱州湾渔业资源各年份的优势种有所变动,中上层鱼类和底层鱼类的优势种变动较大,甲壳类优势种变动较少,鱼类优势种组成存在年际更替现象,主要由经济价值高、个体大的种类向经济价值低、个体小的种类演替.主要优势种集中于斑鲦、矛尾鰕虎鱼、口虾蛄、小带鱼和日本枪乌贼等种类.2010年斑鲦大量暴发,为唯一优势种;(3)2009-2013年黄河入海泥沙年际通量与鱼类种数、底层鱼类数和渔业资源数存在显著相关性,与底层鱼类生物量存在极显著相关性.综上所述,黄河入海泥沙年际通量的变动对莱州湾渔业资源量和资源结构都产生了一定影响.     

Potent cellulase activity in the hepatopancreas of mangrove crabs

Mangrove crabs play a crucial role in the carbon cycle in forests by consuming large amounts of mangrove litter, which is mainly composed of cellulose. However, the detailed mechanism of cellulose digestion remains to be elucidated. We tested endogenous hepatopancreatic cellulase activity in eight species of crabs, including three mangrove sesarmid crabs (Episesarma versicolor, Perisesarma indiarum, and Episesarma palawanense) native to Thailand. Endo-??-1,4-glucanase activity was significantly higher in the enzyme extract from mangrove crabs than in that from Japanese marsh crabs. A ??-glucosidase assay revealed particularly high endo-??-1,4-glucanase activity for E. versicolor, whereas little activity was observed for the Japanese marsh crabs. In a zymogram analysis for endo-??-1,4-glucanase activity, endo-??-1,4-glucanase had a similar molecular mass (30.7?C33.1?kDa) among the mangrove crabs, whereas various sizes (44.3?C84.8?kDa) were found in Japanese crabs depending on the species. These results suggest that mangrove crabs efficiently digest cellulose endogenously.