文蛤动态能量收支模型构建、验证与应用

为评估文蛤生态容量,实验根据动态能量收支理论,基于R语言构建了文蛤动态能量收支模型,采用线性与非线性回归法估算模型参数,通过对比围塘环境下文蛤壳长、湿重、软体部湿重的实测值与模拟值验证模型,并应用于模拟黄海海域滩涂区文蛤的生长过程。结果显示,文蛤模型主要参数形状系数、阿伦纽斯温度系数和单位体积结构物质所需能量分别为0.57、9 278 K和2 056 J/cm³;实测与模拟的文蛤壳长、湿重和软体部湿重相关系数R²平均为0.996,模拟值与实测值的平均误差为3.58%;如东沿海区域6月实测文蛤软体部干重为0.48 g,壳长3.12 cm,模型模拟的软体部干重、湿重和壳长分别为0.476 g,6.6 g和3.2 cm。研究表明,实验构建的文蛤动态能量收支模型的准确度较高,可真实地反映出文蛤在自然水域中的生长过程,为评估文蛤生态容纳量及构建文蛤相关的生态系统模型提供科学参考。     

SEM observations on larval shell morphology of Manila clam Ruditapes philippinarum and their utility

Manila clam Ruditapes philippinarum is common and abundant on Japanese tidal flats, forming a commercially important clam fishery. However, annual catches of Manila clam have decreased drastically since 1975?C1985. To study larval recruitment processes of Manila clam, we carried out scanning electron microscopy (SEM) observations on larval and juvenile shells of clams reared at 20 and 24?°C. There was no significant difference in final shell length of trochophores between 20 and 24?°C. However, the larval duration was much longer and the shell length of settled size of pediveligers was much larger for clams reared at 20?°C than those reared at 24?°C. These findings suggest that larval duration and growth, as well as settlement size, may vary markedly depending on temperature (and probably on season). The larval shell morphology of Manila clam can provide essential information about larval recruitment processes.     

缢蛏选育系F5的生长优势比较及育种效应分析

以6个缢蛏(Sinonovacula constricta)自然群体(浙江象山群体、浙江乐清群体、福建霞浦群体、福建长乐群体、江苏射阳群体和上海崇明群体)为材料,构建基础群体F_0,采用群体选育方法进行多代连续选育(选择强度2.063),比较了选育系F_5与对照群体的生长差异,并估计F_5的选择反应、现实遗传力和遗传获得。结果表明,F_5的卵径及受精率与对照组无显著差异(P0.05),但F_5的变态率、存活率及后期壳长生长明显优于对照组(P0.05);7~360日龄F_5壳长的选择反应、现实遗传力与遗传获得的变化范围分别为0.30~0.78,0.14~0.37和4.83%~42.18%,平均为(0.49±0.06),(0.23±0.08)和(26.49±11.73)%。研究结果表明,对缢蛏的连续多代选育是有效的,可以明显提高其存活能力和主要经济性状。     

Growth Improvement of Shell Length in the Orange Strain of Manila Clam,Ruditapes philippinarum

Mass selection for shell length was conducted in the orange strain of the Manila clam, Ruditapes philippinarum, in this study. Based on the size‐frequency distribution, the clams constituting the largest 10% of the distribution were selected as parents for the selected line. An equal number of clams of the orange strain were randomly chosen as parents for the control line prior to the size selection. The responses to selection and realized heritability were 2.37 and 0.61, respectively. In addition, 97.3% of the progenies inherited the orange shell color. Our results suggest that mass selection for fast growth of shell length in this orange strain of the Manila clam is effective.     

Physical properties of soft shell clams, Mya arenaria

Soft shell clams, Mya arenaria, are found from Canada to North Carolina on the U.S. Atlantic Coast and from Canada to California on the U.S. West Coast. They are also found in several other parts of the world including Europe. The primary market for these clams on the U.S. East Coast is in New England. Clams are sold whole live or in one of the several cooked forms. Commercial soft clam shucking and processing is primarily by manual methods. However, physical properties data for these clams is lacking and is a constraint on the automation of processing. Several properties of soft shell clams harvested from five different harvest locations in the Chesapeake Bay are detailed in this paper and relationships between the components of the clam are defined mathematically through regression equations. The live weight and the clam length are related to shell weight, siphon weight, meat weight, total solids and free water in the clams. Meat yields under both standard processing methods and for clams steamed and consumed with only the shell removed are detailed. The effect of harvest area on the clam parts is also defined. Soft shell clams shucked manually result in a meat yield of approximately 29% of the live weight. If steamed and eaten the meat yield may be as high as 43% of the live weight, primarily because the siphon is often consumed in steamed clams.     

Growing Giant Clam (Tridacna Derasa) in Aquaculture Effluent

Juvenile giant clams (Hippopus spp. and Tridacna spp.) are highly valuable and popular in the aquarium trade due to their brightly colored mantles with various patterns. Giant clams are unique bivalves in that they possess symbiotic zooxanthellae (Symbiodinium). A previous study by the authors demonstrated the feasibility of culturing giant clams in aquaculture effluent. Among the four species tested (Tridacna derasa, T. gigas, T. maxima, and T. squamosa), T. derasa was the most suitable for culturing in effluent. The present study compared the growth, survivorship, and condition indexes of T. derasa (mean initial shell length about 83mm) cultured in fish culture effluent or seawater for six months. The clams grew significantly faster (1.29 vs. 0.93mm shell length/month) and had marginally significant (p = 0.076) higher survivorship (94.1% vs. 77.7%) than those in control seawater. Total (shell and tissue) and tissue weight indexes (g/mm shell length), and mitotic index (% dividing zooxanthellae) were similar between the treatment and control clams; whereas zooxanthellae density (number of zooxanthellae/g clam tissue) of the clams in the effluent tanks was 2.5 times higher than that in control tanks.     

Seasonality of QPX disease in the Raritan Bay (NY) wild hard clam (Mercenaria mercenaria) population

Quahog Parasite Unknown (QPX) is a potentially lethal pathogen of the hard clam Mercenaria mercenaria along the northeastern coast of the United States. In the Raritan Bay wild clam population, QPX prevalence and infection intensity at three sites were examined by both histology and quantitative PCR in 2006. At two of three sites, QPX infection showed a seasonal pattern, with prevalence and weighted prevalence increasing through the spring, peaking in the summer and declining in the fall, while at the other site, the highest QPX prevalence and infection intensity were observed in the spring although overall prevalence at this site was generally low. Our data suggested that temperature may be an important environmental factor regulating the seasonal pattern of QPX disease in wild clams but also demonstrated that seasonal patterns vary from site to site, possibly linked to the clam density or other environmental factors. Over‐winter sampling and further investigations focusing on environmental factors, clam density and clam mortality as related to QPX infection are needed to better characterize and understand the seasonality of QPX disease.     

Reproductive cycle of the venerid clam <Emphasis Type="Italic">Meretrix lusoria</Emphasis> in Ariake Sound and Tokyo Bay,Japan

We assessed the reproductive cycle of the venerid clam Meretrix lusoria by histological analysis of the gonads. Individuals for study were collected from natural populations on the Shirakawa tidal flat, Ariake Sound, and from populations that had been transplanted from the Shirakawa flat to the Oi flat in Tokyo Bay. In both study areas, the reproductive cycle was synchronized between sexes. Gonads of the clam started to develop in early spring and matured during the summer. Mass spawning occurred in the late summer/early fall. The clam matured at a shell length of 17–20 mm, which is much smaller than previously considered. While trophic conditions and salinity differed considerably in the two study areas, water temperatures showed similar seasonal changes (12°C during the winter and around 30°C during the summer). Thus, temperature probably controlled gonadal development. The coincidence of the period of spawning with the period of frequent intrusion of hypoxic waters into the tidal flats in Tokyo Bay suggests that such hypoxic events interfere with clam recruitment and are at least partly responsible for the disappearance of the natural population at this location.     

Influence of Congeneric Aquaculture on Hard Clam (Mercenaria spp.) Population Genetic Structure

Throughout their range, hard clams of the genus Mercenaria support important commercial fisheries, and hard clam aquaculture is rapidly developing in several regions, including Florida, USA. Commercial hard clam aquaculture in Florida waters originated in the Indian River Lagoon during the late 1970s, but by the early 1990s the focus of the industry had shifted to Cedar Key on the west coast of the state. There, the species Mercenaria campechiensis predominates the natural hard clam population, whereas Mercenaria mercenaria is predominant in the local aquaculture industry. The two species hybridize extensively. The present study was conducted to estimate the genetic implications of M. mercenaria aquaculture on the natural population of M. campechiensis that occupies Cedar Key waters. We sampled a variety of marine and estuarine habitats surrounding Cedar Key and collected 257 hard clams for analysis of species-specific diagnostic allozyme loci, age, and the presence and stage of gonadal neoplasia. Results indicate that the composition of the hard clam population has changed since the advent of aquaculture (i.e., post-aquaculture). Members of the species M. mercenaria were practically nonexistent prior to the 1993 initiation of aquaculture in the area but increased significantly in abundance post-aquaculture, as did hybrid hard clams. There was no significant difference in the abundance of M. campechiensis pre- versus post-aquaculture. All genotype classes had a high incidence (>80%) of gonadal neoplasia, although it is not clear if this high incidence is a reflection of the introduction of aquaculture into the area or if neoplasia was a common feature of the population prior to 1993. Regardless, this finding is not consistent with previous reports that neoplasia is more common in hybrid hard clams. Overall, the results of this study provide clear evidence that culture of M. mercenaria can influence the genotype composition of naturally occurring congeneric populations in the vicinity of the culture operation. The long-term implications of that influence remain to be seen.     

不同地理群体菲律宾蛤仔壳形态对体重性状的影响研究

采集我国南北沿海9个地理群体的菲律宾蛤仔(Ruditapes philippinarum),利用通径分析等方法评估各群体形态性状对活体重和软体重的影响。结果显示,各群体壳长、壳高、壳宽和壳厚4 个形态性状对菲律宾蛤仔活体重和软体重的影响存在显著差异。除壳厚外,其他形态性状与活体重和软体重呈显著相关(P < 0.05)。通径分析和决定系数分析显示,大多数群体的壳宽对活体重和软体重的直接作用最大。2个形态比例参数(壳宽/壳长和壳高/壳长)最大值出现在山东莱州群体(0.49和0.74),而最小值出现在大连东港群体(0.42和0.67)。壳厚的变异系数最大(22.74),而壳高的变异系数最小(9.47)。通过检验偏回归系数的显著性,建立了各群体形态性状对软体重的最优回归方程。聚类分析表明,菲律宾蛤仔不同群体未出现明显的地域分布特征,而呈现出不规律的南北交替聚类现象。本研究查明了不同地理群体菲律宾蛤仔壳形态性状对体重性状的影响,为菲律宾蛤仔地理群体的形态判别、种质资源分析和遗传育种研究等提供了重要科学依据。     

Growth and survival of hatchery-bred giant clams (<Emphasis Type="Italic">Tridacna gigas</Emphasis>) in an ocean nursery in Sagay Marine Reserve,Philippines

To restore the diminishing population of the giant clam Tridacna gigas in Sagay Marine Reserve (SMR), Negros Occidental, central Philippines, two size classes [8- and 10-cm shell length (SL)] of hatchery-bred T. gigas were reared in an adjacent ocean nursery for restocking to Carbin Reef later upon reaching grow-out size of ≥20 cm SL. Growth rates did not significantly differ for both sizes and were on average 0.67 cm month⁻¹. However, survival after 382 days of rearing T. gigas was significantly higher in the 10-cm SL clams than the 8-cm SL clams (96 and 83%, respectively). For future restocking projects, the use of 8-cm SL clams is recommended because the lower survival of this size class is compensated by its cheaper price. While rearing the clams to attain grow-out size, the population of wild clams (Family Tridacnidae) in Carbin Reef was assessed using ten 50 × 2-m belt transects. Four species of tridacnid clams have been recorded: Hippopus hippopus, Tridacna crocea, T. maxima, and T. squamosa. T. crocea comprised 12.5–93.9% of all the clams observed in all ten transects. There was a significant difference in clam density between species (ANOVA, F = 6.94, P < 0.001), with T. crocea having the highest density. Living T. gigas were absent, but presence of dead shells was indicative of its presence in the reef in the past. It can be expected that the release of hatchery-bred T. gigas juveniles in Carbin Reef could provide future breeders that will repopulate this reef and the adjacent reef communities.     

Underestimation of primary productivity on continental shelves: evidence from maximum size of extant surfclam (Spisula solidissima) populations

Atlantic surfclams (Spisula solidissima), among the largest extant non‐symbiotic clam species in the world, live in dense aggregations along the Middle Atlantic Bight (MAB) continental shelf. The food resources that support these populations are poorly understood. An individual‐based model that simulates the growth of post‐settlement surfclams was used to investigate the quantity of food needed to maintain existing surfclam populations along the MAB continental shelf. Food inputs to the model were based on measured near‐bottom water‐column chlorophyll concentrations. Simulations showed that these water‐column food sources supported only 65% of the observed body mass of a standard large surfclam (160‐mm shell length). Additional simulations using benthic food sources to supplement water‐column food sources by 20% generated surfclams that grew to observed size and biomass and exhibited spawn timing consistent with the known surfclam spawning season. The simulation results suggest that measured water‐column chlorophyll concentrations may underestimate the food available to the continental shelf benthos. Large continental shelf bivalves are an essential resource for fisheries and higher trophic level consumers. Understanding available and utilized food resources is important for predicting long‐term impacts of climate change on benthic secondary production and fishery yield on the continental shelf.     

不同地理群体菲律宾蛤仔的选择反应及现实遗传力

对不同地理群体的3龄菲律宾蛤仔(Pp莆田群体、Dp大连群体、Tp东京群体)进行了混合选择。测量了各实验组的壳长,计算了不同地理群体菲律宾蛤仔的选择反应和现实遗传力。结果表明,3个地群体菲律宾蛤仔子代的上选组壳长显著大于对照组(P<0.05)。在不同生长发育阶段,菲律宾蛤仔的选择反应(R)和现实遗传力(hR2)随着日龄的增大而减小,即R幼虫培育期0.804±0.084>稚贝期0.705±0.039>养成期0.671±0.024;hR2幼虫期0.458±0.051>稚贝期0.402±0.025>养成期0.382±0.013。从总体水平上分析,菲律宾蛤仔R为0.726±0.1074,莆田群体、大连群体、东京群体的R分别为0.758±0.101、0.690±0.049、0.732±0.059;hR2为0.414±0.044,莆田群体、大连群体、东京群体的hR2分别为0.432±0.058、0.393±0.028、0.417±0.033。地理群体间的R和hR2次序为莆田群体>东京群体>大连群体,且彼此间无显著差异。     

Influence of salinity, diurnal rhythm and daylength on feeding in Laternula marilina Reeve

A nature‐simulating culture system was used to explore the influence of salinity, the diurnal cycle and daylength on ingestion rate (IR) and assimilation efficiency (AE) of Laternula marilina. The clams used in the experiments were grouped into three sizes: large, medium and small according to shell length and dry fresh weight. The clams in all size groups demonstrated a common response pattern in IR and AE under salinities ranging from 18 to 34 g L^?1. The clams achieved the greatest IR within the salinity range 27–30 g L^?1. There was a marked reduction in IR outside this range. Of the salinities tested 18 g L^?1 was the harshest stress to the feeding of L. marilina. Between the salinities of 24 and 34 g L^?1, the AE of the clam responded in an inverse way to that of IR, suggesting that L. marilina is able to compensate for the loss of IR by an increase in AE. Although the differences between clam size groups were not statistically different, those between different salinities were except those between 27 and 34 g L^?1 (IR) and 23 and 34 g L^?1 (AE). All sizes of clam showed a two‐phase diurnal feeding pattern, a high ingestion phase from 00:00 to 08:00 hours and a low ingestion phase from 12:00 to 20:00 hours. The response of feeding (as measured by IR) to daylength comprised high and constant feeding at daylengths from 0 to 16 h and declining and unstable feeding as daylength increased from 16 to 24 h. All sizes of clams demonstrated an inverse adaptation to AE compared with IR, indicating that the clam is able to achieve a stable feeding physiology by compensating for daylength‐induced variations in IR by changing AE.     

Intertidal Growth and Survival of Northern Quahogs Mercenaria mercenaria (Linnaeus 1758) and Atlantic Surf Clams Spisula solidissima (Dillwyn 1817) in Georgia

This work reports on the effects of intertidal planting heights upon the growth and survival of the northern quahog, Mereenaria mercenaria (L.) and the Atlantic sod clam, Spisula solidissima (Dillwyn), in the castal waters of Georgia. Quahogs (N = 100 per cage) at 19.5 mm in shell length were planted in replicate cages (N = 3) placed at the spring (SLW), mean (MLW), one (+1), two (+2), and three (+3) hours above mean low water mark. Surf clams (N = 200 per cage) at 41.5 mm in shell length were placed in replicate cages (N = 3) deployed, as above, in all sites except +3. Quahogs grown at the SLW mark after 15 months were significantly larger than clams planted at other tidal heights. Quahogs planted at the MLW mark were significantly greater in shell length than those planted at the +3, +2, and +1 marks. Clams at the upper three sites were not significantly different in size. An inverse relationship between clam growth and intertidal planting height was evident among surf clams. Surf clams grown at the SLW mark for six months were signplificmtly larger than those at the MLW mark which were larger than those grown at the +1 above MLW mark. No significant differences in quahog survival were detected between intertidal planting sites. There was no significant difference in surf clam survival between SLW (77.5%) and MLW (61%) marks, but there was significantly lower survival at the +1 mark (15%) and no survival at the +2 mark.     

Seasonal effects of clams (Panopea generosa) on eelgrass (Zostera marina) density but not recovery dynamics at an intertidal site

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An investigation of stocks of giant clams (family Tridacnidae) in Java and of their utilization and potential

Abstract. A survey was carried out in Karimun Jawa, a group of islands off the north coast of Central Java, in order (1) to investigate the environmental effect of the collection of giant clam shells used for floor tile manufacture, (2) to investigate the distribution and abundance of living populations of Tridacna spp. and to determine whether the larger species of giant clams are still to be found in the area and (3) to determine the suitability of this area for reseeding of giant clam species for mariculture and/or fishery development. Results showed that the collection of T. gigas shells for the manufacture of floor tiles did not have the same damaging effect on the coral environment as reported elsewhere. They also showed that populations of T, crocea, T. maxima and T. squamosa were still thriving while T. gigas, H. hippopits and T. derusa were extremely rare if not actually extinct, one individual alone of T. derasa being found. The potential for reintroduction of these latter species and for the encouragement of mariculture or fishery development into these islands seems great and is strongly advocated.     

文蛤年龄的研究

本文采用透光法鉴定文蛤的年龄．当贝壳在光透射下，条纹清晰显出。贝壳的亮带形成是在5月至10月，暗带则在10月至翌年的5月间形成。不同年龄组的亮带和暗带形成的时间没有差别。通过贝壳的亮、暗分界线，可以判断文蛤的年龄。     

胶州湾移植底播菲律宾蛤仔的生长和死亡特性

2004年5月至2005年4月对胶州湾菲律宾蛤仔（Rudimpes philippinarum）底播增殖区进行了逐月定点采样，将样品带回放于实验室内水族箱暂养，每站随机取样，共对3269个个体进行了基本生物学特性测定，研究了移植底播菲律宾蛤仔的生长、死亡等渔业生物学特性。结果表明，底播增殖菲律宾蛤仔苗种的平均个体质量0．26g、平均壳长11．1mm；底播蛤仔与野生蛤仔在生长规律上基本一致，春末至秋初（4～9月）是其主要生长期；1～3龄期间个体生长速度较快，1～2龄、2～3龄，个体质量分别增长3．88g和4．02g；1～2龄生物量增长最快，2～3龄由于死亡率增大，其生物量增长缓慢；1～3龄蛤仔软体部的生长速度快于贝壳，5～6月是菲律宾蛤仔的繁殖肥育期。根据个体生长特性，3龄为最佳采捕年龄；根据目前的养殖状况，2龄蛤仔已达到商品规格，从生物量上分析，采捕2龄蛤仔收益最高；6月是最佳的捕获时期。蛤仔生长具有明显的季节变化，水温是影响菲律宾蛤仔生长的主要环境因子。[中国水产科学，2006，13（4）：642—649]     

Larval and post‐larval growth,spat production and off‐bottom cultivation of the smooth venus clam Chionista fluctifraga

Harvesting practices of the clam Chionista fluctifraga show a decline in commercial size and densities, but no strategies have been developed to maintain clam beds. Aquaculture represents an alternative for preserving this resource. Adult clams from commercial grounds were used as broodstock. Conditioning, induction of spawning, cultivation of larvae, settlement of eyed larvae and nursing of postlarvae were performed in the hatchery for producing spat. Larvae and postlarvae were used to measure increase in shell height and data were fitted to exponential growth models. Spat were placed in floating trays and maintained in off‐bottom cultivation for 9 months. Samples of clams and tissues were collected monthly to measure absolute growth, shell height increase and a condition index. Larvae, postlarvae and juveniles showed exponential growth patterns. Mean shell height increased about 0.030 mm day^?1 during larval and post‐larval stages and 0.049 mm day^?1 during field cultivation. Pediveligers (height 215 ± 83 μm) entered metamorphosis at days 9–13 after fertilization, and postlarvae reached 3011.7 ± 325.5 μm (height) at day 60. After field cultivation, survival was about 95%; juvenile shell height was 20.6 ± 2.2 mm, and total weight was 5.3 ± 0.7 g. Growth rates were superior to natural conditions and the condition index was high throughout the study. Our results show that spat of C. fluctifraga can be produced in the hatchery, and that field production can be maintained in off‐bottom trays until reaching commercial size. Aquaculture activities for this species need to be established and evaluated.