Feeding and growth on bivalve biodeposits by the deposit feeder Stichopus japonicus Selenka (Echinodennata : Holothuroidea) co-cultured in lantern nets

Suspension aquaculture of filter-feeding bivalves has been developing rapidly in coastal waters in the world, especially in China. Previous studies have demonstrated that dense populations of filter-feeding bivalves in shallow water can produce a large amount of faeces and pseudofaeces (biodeposits) that may lead to negative impacts on the benthic environment. To determine whether the deposit feeder Stichopus (Apostichopus) japonicus Selenka can feed on bivalve biodeposits and whether the sea cucumber can be co-cultured with bivalves in suspended lantern nets, three experiments were conducted, two in tanks in the laboratory and one in the field. In a 3-month flow-through experiment, results showed that sea cucumbers grew well with specific growth rate (SGR) reaching 1.38% d(-1), when cultured in the bottom of tanks (10 m(3) water volume) where scallops were cultured in suspension in lantern nets. Moreover, results of another laboratory experiment demonstrated that sea cucumbers could survive well on bivalve biodeposits, with a feeding rate of 1.82 +/- 0.13 g dry biodeposits ind(-1) d(-1), absorption efficiency of organic matter in biodeposits of 17.2% +/- 5.5%, and average SGR of 1.60% d(-1). Our longer-term field experiments in two coastal bays (Sishili Bay and Jiaozhou Bay, northern China) showed that S. japonicus co-cultured with bivalves also grew well at growth rates (0.09-0.31 g wet weight ind(-1) d(-1)) depending on individual size. The results suggest that bivalve lantern nets can provide a good habitat for sea cucumbers; and the co-culture of bivalve molluscs with sea cucumbers may provide an additional valuable crop with no additional inputs. (c) 2006 Elsevier B.V. All rights reserved.

Culture of tropical sea cucumbers for stock restoration and enhancement

Severe overfishing of sea cucumbers has occurred in most countries of the tropical Indo-Pacific. The release of juveniles is being examined at the ICLARM Coastal Aquaculture Centre in the Solomon islands as a means of restoring and enhancing tropical sea cucumber stocks. Sandfish (Holothuria scabra) are the tropical species that show the best potential for stock enhancement. Sandfish are of high value, widely distributed and relatively easy to culture in simple systemss at a low cost. This paper summarizes information about the culture of H. scabra and compares it to that of the temperate species Stichopus japonicus.

Genetic evidence for natural hybridization between Red Snow Crab (Chionoecetes japonicus) and Snow Crab (Chionoecetes opilio) in Korea

Both red snow crab (Chionoecetes japonicus Rathbun, 1932) and snow crab (Chionoecetes opilio Fabricius, 1788) are commercially important species in Korea. The geographical ranges of the two species overlap in the East Sea, where both species are fished commercially. Morphological identification of the two species and putative hybrids can be difficult because of their overlapping morphological characteristics. The presence of putative hybrids can affect the total allowable catch (TAC) of C. japonicus and C. opilio, and causes problems managing C. japonicus and C. opilio wild resources. To date, however, no natural hybridization has been reported between C. japonicus and C. opilio, despite their overlapping distributions along the coast of the East Sea. In this study, the internal transcribed spacer (ITS) region of major ribosomal RNA genes from the nuclear genome and the cytochrome oxidase I (CO I) gene from the mitochondrial genome were sequenced to determine whether natural hybridization occurs between the two species. Our results revealed that all putative hybrids identified using morphological traits had two distinct types of ITS sequences corresponding to those of both parental species. Mitochondrial CO I gene sequencing showed that all putative hybrids had sequences identical to C. japonicus. A genotyping assay based on single nucleotide polymorphisms in the ITS1 region and the CO I gene produced the most efficient and accurate identification of all hybrid individuals. Molecular data clearly demonstrate that natural hybridization does occur between C. japonicus and C. opilio, but only with C. japonicus as the maternal parent.

Effect of environmental conditions on the distribution of Pacific mackerel (Scomber japonicus) larvae in the California Current system

We modeled the probability of capturing Pacif ic mackerel (Scomber japonicus) larvae as a function of environmental variables for the Southern California Bight (SCB) most years from 1951 through 2008 and Mexican waters offshore of Baja California from 1951 through 1984. The model exhibited acceptable fit, as indicated by the area under a receiver-operating-characteristic curve of 0.80 but was inconsistent with the zero catches that occurred frequently in the 2000s. Two types of spawners overlapped spatially within the survey area: those that exhibited peak spawning during April in the SCB at about 15.5°C and a smaller group that exhibited peak spawning in August near Punta Eugenia, Mexico, at 20°C or greater. The SCB generally had greater zooplankton than Mexican waters but less appropriate (lower) geostrophic f lows. Mexican waters generally exhibited greater predicted habitat quality than the SCB in cold years. Predicted quality of the habitat in the SCB was greater from the 1980s to 2008 than in the earlier years of the survey primarily because temperatures and geostrophic flows were more appropriate for larvae. However, stock size the previous year had a larger effect on predictions than any environmental variable, indicating that larval Pacific mackerel did not fully occupy the suitable habitat during most years.

Length-based estimates of vital statistics in threadfin bream (Nemipterus japonicus) from Bay of Bengal, Bangladesh

ELEFAN 0, ELEFAN I and ELEFAN II were used to estimate vital statistics of Nemipterus japonicus from length-frequency data sampled along the coast of Bangladesh. The parameters L and K were estimated at 24.5 cm and 0.94 year super(-1). The values of M and F were found to be 1.81 and 1.58 year super(-1), respectively. The fish recruit to the fishery during May-June and September-October.

Growth and length-weight parameters of Pacific mackerel (Scomber japonicus) in the Gulf of Guayaquil, Ecuador

The seasonally oscillating growth parameters and length-weight relationships for Scomber japonicus caught in the Gulf of Guayaquil, Ecuador, were determined based on length-frequency data from 1989 to 1996, using the FiSAT software package of Gayanilo et al. (1996). Estimates of growth parameters are in general agreement with previous studies on the same species. Results also imply that the growth of Scomber japonicus slows down during the cold season by approximately 50% with respect to the average growth. The mean value of the power b is significantly larger than 3, indicating that the model of allometric growth should be used for the length-weight relationship and calculation of the condition factor.

麦冬（Ophiopogon japonicus (L.f)Ker Gawl）花粉的发育、精子结构及绒毡层的变化

麦冬的花粉发育自小孢子母细胞开始，经连续型减数分裂，产生游离的单细胞小孢子;小孢子进一步发育，经两次有丝分裂，最终发育为包含有二个精细胞和一个营养核的成熟花粉。在此发育过程中，内质网、线粒体、高尔基体和脂体含量丰富。 麦冬的精子细胞为伸长的细胞，具有椭圆形的头部和长长的尾部细胞质突起，细胞器较少，是线粒体，但缺乏质体，没有明显的二型性;其精细胞伸长的尾部细胞质突起是在生殖细胞有丝分裂时产生，而不是以后由精子细胞本身发育;两个精子细胞之间除了头部的联结外，还有尾部的联接，但没有任何结构上的联结;一个精子细胞的头部常与营养核十分靠近;另外，在精子与精子之间或精子与营养核之间的贴近点上，常可见到多层膜的结构，根据精细胞之间的联结和精细胞与营养核之间的靠近，推测麦冬的成熟花粉中存在雄性生殖单位。 麦冬的花粉壁发育在四分体后期开始，首先产生纤维状的原外壁，由原外壁上依次发育出原基柱层、原覆盖层和原基足层，当四分体分离时，花粉外壁外层已发育完全;在单细胞小孢子时期，外壁内层发育，为极薄的一层，同时内壁－1开始发育;到了二细胞花粉时期，内壁－1开始发育;到了二细胞花粉时期，内壁－1发育完全，并在萌发孔处发育特殊的蜂窝状结构;紧接内壁－1层，发育出内壁－2层。在其壁发育过程中，花粉中大量沿周围平行于花粉壁排列的内质网可能与花粉壁的形成有关。 麦冬的绒毡层发育属分泌型。在小孢子母细胞时期，绒毡层细胞达到了发育的顶峰，此时，细胞器非常丰富，大量的线粒体、高尔基体和质体，尤为内质网含量最为丰富;原乌氏体出现较早，小孢子母细胞时期绒毡层细胞中就已出现;四分体时期，大量乌氏体被排入内切向面的质膜和纤维素壁之间;到了小孢子早期，绒毡层细胞失去细胞壁，原乌氏体分布在质膜的凹陷处，孢粉素物质开始在其上沉积，发育为乌氏体，乌氏体有单个和复合两种类型;到花粉成熟时，绒毡层细胞彻底解体。

Effects of density-dependence and sea surface temperature on interannual variation in length-at-age of chub mackerel (Scomber japonicus) in the Kuroshio-Oyashio area during 1970–1997

Annual mean fork length (FL) of the Pacific stock of chub mackerel (Scomber japonicus) was examined for the period of 1970–97. Fork length at age 0 (6 months old) was negatively correlated with year-class strength which fluctuated between 0.2 and 14 billion in number for age-0 fish. Total stock biomass was correlated with FL at age but was not a significant factor. Sea surface temperature (SST) between 38–40°N and 141–143°E during April–June was also negatively correlated with FL at age 0. A modified von Bertalanffy growth model that incorporated the effects of population density and SST on growth was well fitted to the observed FL at ages. The relative FL at age 0 for any given year class was maintained throughout the life span. The variability in size at age in the Pacific stock of chub mackerel is largely attributable to growth during the first six months after hatching.

Condition factor and length-weight relationship of Nemipterus japonicus (Bloch) off Bombay coast

Fluctuations in the K values of Nemipterus japonicus (Bloch) off Bombay coast were interpreted regarding sex, month and females maturity stage. These indicate differential growth rates in males and females. Males and females attain first maturity at 145 mm and 115 mm respectively, second maturity is attained by both the sexes at 195 mm. First spawning occurs when both are of 155 mm length and at second spawning males and females attain 215 and 205 mm of length respectively. The fish mature and breed at "O" year; the main spawning period is from August to November with peak spawning activities in October. It grows about 155 mm in first year at 12.91mm per month and about 215 mm in the second year at 5.0 mm per month on an average. Length-weight relationships for males and females are given. The rate of growth of females by weight was found to be slower below 150 mm, but faster than that of males above 150 mm specimens.