Concentrations of trace elements in <Emphasis Type="Italic">Meretrix</Emphasis> spp. (Mollusca: Bivalva) along the coasts of Vietnam

The dominant coastal bivalve in Vietnam, hard clams Meretrix spp., collected from the South Key Economic Zone (SKEZ), the Mekong River Delta, and the Central Coastal Zone (CCZ) were analyzed for 21 trace elements. Comparison of the results from the three regions indicated that levels of most of the trace elements, especially As, Mo, Sn, and Pb, were highest in the samples collected from the CCZ, whereas most of the trace elements were found to be present at relatively low levels in samples from the SKEZ. The high concentrations of these trace elements in the CCZ, a sparsely populated region with less human activity than the other two regions, were believed to have originated from industrial waste produced in a shipyard. Although the trace element concentrations in the bivalves were within safe levels for human-consumption criteria reported by the United State Food and Drug Administration and the European Commission, estimation of cancer risk based on As concentration indicates that the hard clams from the CCZ pose a high risk to consumers. Thus, the industrial waste produced in the less densely populated region might increase the health risk to consumers via the contamination of bivalves commonly used as food.     

Long‐term epidemiological study of disseminated neoplasia of cockles in Galicia (NW Spain): temporal patterns at individual and population levels,influence of environmental and cockle‐based factors and lethality

The dynamics of disseminated neoplasia (DN) affecting cockles Cerastoderma edule (L.) in Galicia was addressed at individual and population levels. Early stage of DN was characterized by isolated neoplastic cells occurring in branchial vessels or in the connective tissue of gills, mantle, gonad or digestive gland. As disease progressed, the neoplastic cells appeared loose in foci and became widely distributed throughout the organs. In advanced stages, the connective tissue of most organs was infiltrated by neoplastic cells, which displaced normal cells, leading to the loss of the normal tissue/organ architecture. Host defence reaction was occasionally observed. A field survey performed for 7 years, in two cockle beds located in different Galician Rías, showed that DN is a hyperendemic disease usually present all year‐round at high prevalence in adult cockles but with annual prevalence minima in spring likely due to the death of heavily affected cockles, concurrently with gonad ripeness–spawning. DN was detected in the cockles ranging from 10 to 39 mm in size; the highest DN prevalence and severity corresponded to the cockles of intermediate size/age (22–29 mm/0.7–1 year old). Sex did not appear to influence DN occurrence. An inhibitory effect of DN on cockle gametogenesis was detected.     

Modelling of common European cockle <Emphasis Type="Italic">Cerastoderma edule</Emphasis> fishing grounds aimed at sustainable management of traditional harvesting

In the Bay of Saint-Brieuc, a 3,110-ha tidal bay in NW France, English Channel, the cockle Cerastoderma edule has been collected by traditional fishing methods for many decades without any evaluation or management of this resource taking place. Since 2001, the National Natural Reserve of the bay of Saint-Brieuc has carried out an evaluation of the stock and a mapping of the cockle fishing grounds each year. Analysis of the spatial structure of the population is approached by cartography through interpolation of the data using the kriging method. The recruitment zones are geographically quite well defined and located in areas limited to the mean-tide zone. The distribution of the population was affected by passive displacement of juvenile cockles. Evaluation using the matrix of individual numbers for each age group found the inter-annual mortality rates to be about 60%. Somatic production was estimated and expressed in ash-free dry weight. The average annual production ranged from 7.4 to 14.5 g/m2. In the autumn of 2006, the minimum legal fishing size changed from 30 to 27 mm (corresponding to individuals aged about 2.5 years). The model developed shows that this change has led to a doubling of the fishable stock.     

Trace elements in waters of inland,low‐salinity shrimp ponds in Alabama

Trace element concentrations in waters of 10, inland, low‐salinity shrimp ponds in Alabama tended to be greater than those found in normal seawater – molybdenum, boron and silicon were exceptions. Concentrations of most trace elements varied greatly among ponds on individual sampling dates, and average concentrations based on all sampling dates in individual ponds also varied considerably. The analytical method used, digestion of water samples in nitric acid followed by inductively coupled plasma atomic emission spectrophotometry, measured total concentrations of trace elements – free ions, hydrolysis products, ion pairs, coordination compounds (chelated forms) and particulate forms. Free ions are the toxic forms of most trace elements and the ionic concentration is much less than the total concentration of a trace element. Based on total concentrations of trace elements, it is doubtful that free‐ionic concentrations of trace elements were great enough to harm shrimp. The fact that no negative correlations were noted between trace element concentrations and shrimp survival and production supports this conclusion. However, positive correlations (P < 0.05) between shrimp survival and production and increasing concentrations of zinc, cobalt and iron should be investigated further to ascertain if additions of these elements to ponds might improve shrimp performance.     

Bioaccumulation and distribution of trace elements in tissues of giant river prawn <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis> (Decapoda: Palaemonidae) from South Vietnam

ABSTRACT:   Accumulation profiles of 22 trace elements in abdominal muscle, abdominal exoskeleton and the hepatopancreas of the giant river prawn Macrobrachium rosenbergii were analyzed. The giant river prawn is an indigenous freshwater species from South Vietnam, and is cultured commercially and fished in the wild. Samples were collected from Ho Chi Minh City and the surrounding area (SKEZ, South Key Economic Zone), and from the Mekong River Delta between 2003 and 2005. Highest accumulations of essential (Cu, Se and Mo) and toxic (As, Ag, Cd and Hg) elements were observed in hepatopancreatic tissue, except for Mn, Sr, Sn, Ba and V in the exoskeleton and Rb and Cs in muscle tissue. Spatial differences showed concentrations of Cs and Pb in muscle and Sr in exoskeletons from the SKEZ were higher than those from the Mekong River Delta. The opposite trend was observed for Cr, Se and Sb in muscle, Mo, Sb and Tl in exoskeleton, and Se, Hg, Mo, Cd, Sb, Tl and Bi in the hepatopancreas. These differences in trace element concentrations in prawns likely reflect differences in industrialization and human activities between the two regions of South Vietnam.     

Effects of seasonal variations and pond age on trace elements and their correlations with plankton productivity in commercial freshwater crayfish (cherax cainii austin, 2002) earthen ponds

Seasonal variations can affect the concentration of trace elements, and the change in their concentrations can affect the natural productivity of freshwater aquaculture ponds. Hence, we studied the seasonal variations of the 12 pre‐selected trace elements (Co, Cu, Fe, Mn, Zn, Se, Ca, Mg, P, S, Al, Si) and their relationships with primary and secondary productivity in two aged ponds, stocked with three different life stages of marron (Cherax cainii), for a period of 1 year. Trace element analysis was performed by using (Agilent, ICP‐OES). Except Co and Se, all trace elements, and primary and secondary productivity were influenced by seasonal variation. The pond age significantly influenced the concentrations of some trace elements. On a seasonal basis, trace elements were positively correlated with the plankton abundance, species diversity, and wet and dry plankton weights. Seasonal variations and pond age affected the dissolved concentrations of trace elements and plankton productivity.     

Phytoplankton uptake and growth rate in the Japanese egg cockle Fulvia mutica

To clarify the relationship between the quantity of food ingested by and the growth rate of the Japanese egg cockle Fulvia mutica (Reeve), we conducted a laboratory breeding experiment for 2 weeks and estimated the chlorophyll a (chl-a) concentrations in water and the increments in shell length and soft-body weight of this species under five chl-a concentrations. Moreover, we compared the relationship between cockle growth (changes in soft-body weight and shell length) and their feeding environment observed in the laboratory experiment with the results of a field investigation conducted at two sites in the Sea of Japan, Kumihama Bay (35°38′5″ N, 134°54′00″ E) and Kunda Bay (35°33′30″ N, 135°15′4″ E). The changes in soft-body weight were similar in both laboratory and field investigations, but those in shell length were not. We, therefore, considered shell length changes as unsuitable for evaluating the relationship between growth and feeding in F. mutica. Based on the changes in soft-body weight, it was possible to classify the feeding environment of this species into the following three types: (1) < 1.52 μg chl-a L−1, negative feeding environment for cockle growth; (2) 1.52–5.71 μg chl-a L−1, neutral feeding environment for cockle growth; (3) > 5.71 μg chl-a L−1, positive feeding environment for cockle growth (growth increased with increasing chl-a concentration up to about 11 μg chl-a L−1). These results indicate that maintaining chl-a concentration in the breeding water within 5.71–11 μg chl-a L−1 is desirable for rearing Japanese egg cockle.     

Effects of stocking density and substratum on the survival,growth, burrowing behaviour and shell morphology of juvenile basket cockle,Clinocardium nuttallii: implications for nursery seed production and field outplanting

The basket cockle, Clinocardium nuttallii, is a candidate species for aquaculture in British Columbia, Canada. Previous research on broodstock conditioning, embryonic development and larval rearing of C. nuttallii demonstrated the potential for reliable hatchery production of cockle seed. In this paper, we investigated the effects of culture density (50% and 150% bottom cover in a monolayer) and substratum (none and fine sand) on cockle seed survival, growth, behaviour and shell morphology to improve the efficiency of the nursery production phase. Low stocking density (50% cover) yielded a shell length increase from 3 to 7 mm over a 4‐week period. High stocking density (150% cover) negatively impacted some of the growth and condition parameters studied, but did not have a statistically significant effect on seed survival. Growing seed without substratum did not significantly affect seed survival or growth, but led to shell deformities (at shell length >15 mm) and lower burrowing rates when cockles were subsequently placed on sand. We recommend planting seed for grow‐out at a shell length not exceeding 15 mm. Acclimating seed to the substratum before planting may increase the burrowing rates, thereby reducing the risks of seed dislocation and mortality. Additional studies are required to determine optimal substratum acclimation times and techniques.     

Frequent occurrence of the tetrodotoxin-bearing horseshoe crab <Emphasis Type="Italic">Carcinoscorpius rotundicauda</Emphasis> in Vietnam

Tetrodotoxin (TTX) was detected by HPLC and LC-MS/MS in specimens of the horseshoe crab Carcinoscorpius rotundicauda collected from Tan Hai village, Vung Tau province, Vietnam, where cases of poisoning due to the consumption of horseshoe crab have frequently been reported. The soft tissue from 10 out of the 12 specimens analyzed showed considerable levels of TTX, making them unsafe for human consumption (81.2 ± 50.3 MU/g). Paralytic shellfish poisoning (PSP) toxins were also detected in all of the specimens, but the levels were low. These findings show that the frequency of occurrence of C. rotundicauda specimens with a high level of TTX is significantly high, and that the TTX is responsible for the food poisonings caused by the consumption of C. rotundicauda in this area.     

Growth and fatty acid composition of juvenile Cerastoderma edule (L.) fed live microalgae diets with different fatty acid profiles

The importance of dietary 20:5n‐3 (EPA), 22:6n‐3 (DHA) and 20:4n‐6 (ARA) for growth, survival and fatty acid composition of juvenile cockles (Cerastoderma edule) was investigated. Cockles of 6.24 ± 0.04 mm and 66.14 ± 0.34 mg (live weight) were distributed into three treatments where live microalgae diets were fed constantly below the pseudofaeces production threshold, for three weeks. Diets had distinct fatty acid profiles: high EPA (53% Chaetoceros muelleri + 47% Pyramimonas parkeae), no DHA (47% Brachiomonas submarina + 53% Tetraselmis suecica) and low ARA concentrations (73% P. parkeae + 27% Phaeodactylum tricornutum). Growth was positively affected by high EPA and low ARA diets, whereas no significant growth was observed for the no DHA diet. High mortality of cockles fed no DHA diet raises questions about its suitability for cockles. In balanced diets with EPA and DHA, lower concentrations of ARA do not limit growth. The impact of dietary fatty acids was evident in the fatty acids of neutral and polar lipids of cockles. In polar lipids of all cockles, there was a decrease in EPA, in contrast to an increase in DHA. The combination of EPA and DHA in a live microalgae diet was beneficial for the growth and survival of juvenile cockles.     

The relationship between trace elements in fish otoliths of wild carp and hydrochemical conditions

The trace element composition of the fish otolith is an indicator of biomineralization. In contrast to other skeletal tissue, the otolith retains its entire original structure and does not absorb any elements after the fish dies. Because otoliths in carp degrade very slowly in the dead body, the information it provides on the environment is retained, even in fossil form. Here, we report our analysis of the trace elements in otoliths of carp and of the water in Donghu Lake and Longhupao Lake, Heilongjiang province, China, where the fish lived. The results revealed that the trace elements found in the carp otoliths were clearly correlated with those found in these water bodies. There were high concentrations of Au, Ba, K, Sr and Zn in both the water and otoliths; in contrast there were high levels of As, Na and Se in water, but low concentrations in otoliths. These results indicate that an analysis of the otoliths of carps provides an accurate procedure for studying the surrounding hydrochemistry conditions. The interaction of the elements during deposition was also studied. The correlation coefficients of 13 trace elements identified in the otoliths in both lakes were calculated.     

Current status of cockle bed restoration in New Zealand

The intertidal cockle Austrovenus stutchburyi, also known as tuangi or littleneck clam, is endemic to New Zealand, where it commonly occurs in sheltered sandflats and estuaries. While it is still abundant in some places, recreational collecting and habitat change have resulted in the losses of shellfish beds. This paper reviews the current status of cockle beds in New Zealand and outlines some of the methods that are being used to try to re-establish them. Cockle populations differ both within and between locations, and recent research suggests that this is often site-specific and correlated with sediment properties, salinity and contamination levels. The role of Customary Fishing Regulations and the management of Maori Marine Reserves in promoting cockles as a sustainable shellfishery is discussed, together with the role of closures. The transfer of adult stock may be the most promising technique for restoration. There is, however, a need to identify the potential risks and choose the sites carefully to ensure that shellfish are sustainable and that they improve ecosystem function.     

Using trace elements in otoliths to discriminate between wild and farmed European sea bass (<Emphasis Type="Italic">Dicentrarchus labrax</Emphasis> L.) and Gilthead sea bream (<Emphasis Type="Italic">Sparus aurata</Emphasis> L.)

Trace elements in otoliths of sea bass (Dicentrarchus labrax L.) and sea bream (Sparus aurata L.) from fish farms and coastal wild populations in the western Mediterranean Sea were analysed by inductively coupled plasma-mass spectrometry. Results showed that concentrations of Mg, K, and Mn differed significantly between wild and farmed sea bass, while concentrations of Mg, K, Mn, Fe, Zn, Sr, and Ba varied significantly between wild and farmed sea bream. Discriminate analysis and cross-validation classification showed that the trace element profile in otoliths can be used to separate farmed fish from wild stocks with high accuracy on both sea bass (individuals correctly classified: 90.7 %) and sea bream (individuals correctly classified: 96.6 %). Moreover, trace elements in otoliths resulted to be useful to discriminate among wild fish stocks within each species.     

Aquaculture potential of the basket cockle (Clinocardium nuttallii). Part 1: effects of stocking density on first year grow‐out performance in intertidal and off‐bottom suspended culture

The basket cockle (Clinocardium nuttallii) is a candidate species for aquaculture in the northeast Pacific. The aim of the current research was to assess the feasibility of C. nuttallii grow‐out, with an emphasis on growth performance and qualities affecting product marketability. In this article, we investigated the combined effects of culture mode (intertidal and off‐bottom suspended culture) and initial stocking density (1500, 3000, 10 500 and 21 000 ind m^?2) on C. nuttallii survival and growth during the first year of grow‐out (May through October). In intertidal culture, cockles exhibited low survival and poor growth rates. In suspended culture, survival was consistently high (>96%) at all stocking densities tested; growth and condition parameters had the highest values at 1500 and 3000 ind m^?2. The edible portion (meat yield) exceeded 40% of the whole wet weight at all stocking densities, occurrences of fouled and deformed cockles were <1% and no commensal species were observed. Depending on the minimum harvestable size and stocking density chosen, harvestable proportions constituted from 1.1% to 15.2% by October of the first grow‐out year in the suspended system. The effects of stocking density and depth on second year grow‐out performance of C. nuttallii are reported in a companion paper (Dunham et al. in this issue).     

Origin identification method by multiple trace elemental analysis of short-neck clams produced in Japan, China, and the Republic of Korea

The correlations among the contents of trace elements in the shells of short-neck clams collected from Japan, China, and the Republic of Korea were examined. Origin-specific elemental content patterns were seen in clams originating from Japan, China, and the Republic of Korea. The crushed shells were decomposed with nitric acid–hydrogen peroxide, and the concentrations of ten elements (Li, V, Mn, Co, As, Rb, Mo, Ba, Pb, and U) in the shells were measured by inductively coupled plasma mass spectrometry. Some of the metal concentrations in the samples displayed clear geographical trends. The average concentration of Pb in Japanese clam shells was one-half to one-quarter that seen in Chinese or Korean clams. Average concentrations of As, Rb, and Ba in shells of Japanese origin were one-half those observed in Chinese or Korean clams. Linear discriminant analysis was applied to these analytical data, and four discriminant models were constructed. These discriminant models were able to distinguish the geographic origins of short-neck clams with 80.0–100 % accuracy. In particular, clams of Japanese origin were classified correctly ≥90 % of the time. Therefore, the trace elemental analysis of a short-neck clam shell is useful for identifying the country of origin of the clam.     

微量元素对水华发生、发展的影响

微量元素作为藻类营养因子的一部分,对藻类生长具有重要作用,而藻类(特别是微囊藻)的大量增长则会造成"水华"现象。本文综述了各种微量元素对水华藻类生长的影响及其影响机理,进而得出结论:微量元素对水华藻类的生长影响趋势为低浓度促进生长,高浓度抑制生长,而藻类对微量元素有一定的富集作用;在微量元素中,铁元素对水华的发生、发展至为重要,在某种情况下有可能成为水华发生、发展的限制因子;其他元素(如稀土元素和重金属元素等)在水华发生、发展中则起辅助作用。     

我国三省稻田养殖克氏原螯虾肌肉中24种微量元素含量及健康风险评价

为探讨我国稻田养殖克氏原螯虾的微量元素含量水平和食用安全性,利用电感耦合等离子体质谱法(ICP-MS)分析了湖北、湖南和安徽3省156份稻田养殖克氏原螯虾肌肉样品中24种微量元素的含量,并采用污染指数法、暴露评估和非致癌风险评价法进行污染评价和膳食评估。结果显示,在克氏原螯虾样品的24种微量元素中,Li、Be、Tl和U这4种元素未检出,Ni、Cd和Pb这3种微量元素检出率低于50%。有16种元素含量在安徽与其他两个产地间存在显著差异,而其中5种元素在3个不同产地间存在显著差异。所有克氏原螯虾样品中,有害重金属元素As、Cu、Pb、Cd和Cr的污染指数均小于0.2,处于正常背景值水平。研究表明,21种微量元素的总目标危害系数TTHQ=3.672<10,有害元素的THQ均在可接受范围,长期食用对人群没有明显的健康风险,但营养元素Fe的摄入值得关注。     

Status of freshwater fish around the Korean Demilitarized Zone and its implications for conservation

• 1. The Korean Demilitarized Zone (DMZ), which divides the Korean peninsula, currently serves as a sanctuary for diverse biological resources, owing to limited development and human activities. The fish fauna of the DMZ areas, including the Civilian Control Zone (CCZ) and Military Facility Protection Area (MFPA), was investigated by quarterly sampling at 53 sites from August 2001 to May 2004.
• 2. In total, 10 946 fish were collected and classified into 99 species and 26 families. Zacco platypus (relative abundance, RA 18.6%) was the dominant species, while other key species were Rhynchocypris steindachneri (16.0%), Pungitius sinensis (12.5%) and Zacco temmincki (8.5%).
• 3. Thirty species were found to be Korean endemics, representing seven families. Eight Korean vulnerable species and two Korean natural monument species were recorded. Three exotic fish species (Carassius cuvieri, Micropterus salmoides and Lepomis macrochirus) were collected at 13 study sites, all but one of which are outside the CCZ. There were significant relationships between altitude and fish species richness (r²=0.448, P<0.001) and the number of endemic fish species (r²=0.487, P<0.001).
• 4. Owing to very limited human interference, the DMZ could provide good benchmark sites to enable ecological restoration on other rivers and streams for maintenance of natural freshwater fish biodiversity. It is suggested that a natural park is instituted around the DMZ areas for ecological protection and as a symbol of peaceful coexistence between South and North Korea.

Copyright © 2007 John Wiley & Sons, Ltd.     

Aquaculture potential of the basket cockle (Clinocardium nuttallii). Part 2: effects of stocking density and depth on second year grow‐out performance of three size cohorts in intertidal and off‐bottom suspended culture

We investigated the effects of culture mode (intertidal and off‐bottom suspended culture) and initial stocking density (5%, 10%, 35% and 70% bottom cover) on survival, growth and condition indices of three size cohorts (16, 22 and 32 mm initial shell length) of the basket cockle, Clinocardium nuttallii, during a second year of grow‐out. In addition, we evaluated the effects of depth (2, 4 and 6 m) in suspended culture. All size cohorts demonstrated significantly higher growth rates, soft‐tissue biomass and condition indices in the off‐bottom suspended system compared to the intertidal one. In suspended culture, however, C. nuttallii exhibited sub‐optimal survival, shell deformities and heavy fouling. For all size cohorts, stocking density had a significant effect on most growth and condition parameters, except meat yield indices, in both culture modes. An initial maximum stocking density of 10% cover is recommended for all size cohorts. Culture depth did not have a consistent statistically significant effect on any of the growth or condition parameters. Depending on the grow‐out scenario, stocking density and harvestable size chosen, the cumulative harvestable proportion after the second year of grow‐out constituted 15.5–63.1% of the seed planted. Our results could be used to develop and improve culture techniques for C. nuttallii and other cockle species.     

长春市市售9种鱼类中重金属含量分析及健康风险评价

为了解长春市居民日常消费的9种鱼类的重金属污染水平并评估其健康风险,利用电感耦合等离子体原子发射光谱仪(ICP-OES)法对长春市出售的鲫(Carassius carassius)、鲤(Cyprinus carpio)和草鱼(Ctenopharyngodon idellus)等9种鱼类中的Pb、Cd、Cr、Zn和Cu 5种重金属进行了检测。采用单因子污染指数法(Pi)、综合污染指数法(MPI)和目标危险系数法(THQ)对其污染程度及食用健康风险进行评价。Pi指数表明:Cu、Cd、Cr在各种鱼类中均未出现超标现象,而9种鱼类肌肉中Pb均呈现不同程度的污染,乌鳢(Channa argus)、鲶(Loricariidae)和黄颡鱼(Pseudobagrus fulvidraco)肌肉中的Pb呈重污染水平。MPI结果显示:不同食性鱼类重金属富集程度有差异,肉食性和杂食性鱼类重金属污染水平高于草食性鱼类。鱼类的单一和复合重金属健康风险指数均小于1,长春市市售鱼类食用安全性较好,对人群健康风险不明显。