Settlement of Mussel Perna perna Seed on Artificial Collectors Deployed on Sea Surface

The low settlement of mussel Perna perna seeds on artificial collectors deployed on sea subsurface has been a major obstacle to the mussel farming improvement in Brazil. This study aimed to compare the seed settlement on artificial collectors deployed on the sea surface with the aid of buoys and at the subsurface (20 cm depth) in Cocanha Beach, Caraguatatuba City, Sao Paulo State, Brazil. Mann–Whitney test showed significant differences (P < 0.05) between treatments for each class of length, with the best settlement occurring on the sea surface collectors for all classes (P < 0.05). It is concluded that deploying artificial collectors with buoys on the sea surface increases the number and the biomass of settled mussel seeds when compared to the non‐buoys deployed collectors on the sea subsurface.     

Differential Growth of the Mussels Perna perna and Perna viridis (Bivalvia: Mytilidae) in Suspended Culture in the Golfo de Cariaco,Venezuela

We evaluated the growth of mussels Perna perna and Perna viridis in suspended culture in the Golfo de Cariaco in Venezuela. Juveniles were cultured for up to 13 mo on cultch strings suspended from longline, with monthly sampling for determination of shell length and dry weights of shell and soft tissues. Water temperature, oxygen, salinity, chlorophyll a, seston, and shell fouling were also monitored. In both species, growth during the first 5 mo (the stratification period in the region) was slow. Subsequently, the onset of the coastal upwelling period (November/December) generated lower temperatures and higher plankton levels, correlated with higher growth rates, particularly in P. perna, which by the end of the experiment had reached a mean length 1.3‐fold greater than that of P. viridis (95.3 ± 7.91 vs. 73.3 ± 6.99 mm) together with a 1.9‐fold greater somatic tissue. Likewise, reproductive activity differed between the two species, P. perna showing a higher gonad development and its reproductive activity starting earlier than that of P. viridis. Our results show that P. perna presents higher growth and survival than P. viridis in suspension culture, a fact related to a greater tolerance to the environmental characteristics of the Golfo de Cariaco.     

Influence of densities on the growth of brown mussel Perna perna L. cultivated in suspended socks at Caraguatatuba,southeastern Brazil

This study was carried out in a marine area at Cocanha Beach, Caraguatatuba, southeastern Brazil, aiming to determine the most appropriated density for brown mussel (Perna perna L.) cultured in suspended socks (French System), in order to reduce costs with acquisition of juvenile mussels (seed) and labor. In September 2007, 15 socks measuring 2 m each were reared at densities of 300, 400 and 500 seeds/m. After 250 days, mussels were harvested and separated in two length classes: non-commercial (<6 cm) and commercial (≥6 cm). Mussels were counted and weighed. In August 2008, the experiment was repeated with 1-m-long socks at lower densities (200, 250 and 300 seeds/m) in order to identify differences among commercial-sized mussels only. Data were analyzed by ANOVA or nonparametric Kruskal–Wallis test, followed by Tukey or SNK tests, respectively. The results suggest that it is feasible to use densities from 250 to 300 seeds/m, since biomass yields are similar to those registered at higher densities and the use of mussel seed is therefore optimized.     

Molting,Mortality, and the Effects of Density in a Soft-Shell Crawfish Culture System 1

The molting and mortality patterns at a crawfish density recommended for commercial-scale soft-shell crawfish culture systems showed that, over a 116 day period, 74% of the crawfish molted, 22% died, and 4% remained in the system at the end of the study. Approximately three weeks of adaption to the system were required before molting rates of the crawfish began to increase. By the sixth week, the number of malted crawfish per day exceeded the overall mean and remained at this level until 10 days before moltable crawfish were depleted. In a second study, three density levels (3.7,4.9, and 6.1 kg crawfish/m²) were tested for 60 days. The lowest density produced significantly fewer (P < 0.05) molted crawfish. Mortality was significantly greater (P < 0.05) at the highest density compared with the lowest density. The highest density (6.1 kg crawfish/m²) showed a higher molting rate than the lower densities, but it was not significantly different (P < 0.05) from the molting rate of 4.9 kg/m².     

Productive performance of brown mussels Perna perna (Linnaeus, 1758) cultivated on ropes at low densities in Caraguatatuba,Brazil

In Brazil, mussel seed are not a plentiful natural resource, and so the efficient use of seeds by reducing stocking densities should be considered. There are very few studies addressing the relationship between seeding density and growth of mussels in tropical conditions. This work aimed to determine the influence of low seeding densities on the productive performance of Perna perna (Linnaeus) mussels cultivated on ropes in Caraguatatuba, Brazil. In October 2014, 12 ropes, one metre in length each, were seeded at the densities of 200, 300 and 400 mussels/m (four ropes for each density) and suspended on a long line. After 226 days of growing, mussels were harvested and their performance at each density was evaluated in terms of mean weight and length, production, culture efficiency, condition index, survival, amount of recruited seed, amount of fouling on the ropes and morphometric relationships. We observed no significant differences (p > .05) for these indicators among the densities tested, except for mussel biomass, which was significantly higher (p < .05) at the greater densities. A partial budget analysis showed that the density of 400 m^?1 showed better profitability and should be recommended, even in case of seed shortage.     

Differential growth of the brown mussel,Perna perna (Linnaeus, 1758), in longline and pole cultures in Dakhla Bay (SW Morocco,Atlantic Ocean)

There is a great interest in establishing mussel farming in Dakhla bay. Selection of suitable sites is more meaningful only if a reliable culture method at proposed site is included. We compared two different culture methods, longline and pole, over 1 year (June 2016 to June 2017). Growth indicators for Perna perna (size and weight growth rates, frequency distributions and estimating growth curves) were analysed from seeding to harvest. The results highlighted the influence of culture method on growth rates of mussels (p < 0.05). At harvest, individuals reared on longline presented higher growth rates and consequently reached greater weight and length values than those reared on pole. Mussels reared at the longline grew 73.2 mm and gained 53.5 g W_L (live weight) and 3.3 g W_t (tissue dry weight) after 12 months of cultivation. However, mussels cultured at the pole gained only 52.3 mm, 26.7 g W_L and 1.6 g W_t. Aerial exposure of mussels at low tides could explain this reduced performance on pole compared with longline. Size frequency distributions at harvest fitted bimodal distribution in both cultures due to an asymmetric competition among individuals. Effect of density started in both treatments after 7 months of culture when mussels reached 60–70 mm, implying an increment of their food and space requirements. To prevent overcrowding, the initial density should have been reduced through “thinning‐out.” The longline method exhibited high‐performance growth and hence is highly recommended for cultivation of P. perna in Dakhla bay.     

Recruitment and Commercial Seed Procurement of the Blue Mussel Mytilus edulis in Maine

A thorough understanding of recruitment in the blue mussel is necessary if the new industry is to maximize seed procurement without impinging upon other fisheries. Larval appearance is a relatively precise event in Maine, cued to early summer water temperature of 10–12 C and, apparently, full moon spawning events. Mussel larvae are more abundant on the flood tides indicating inshore and estuarine retention, although this retention relates to the morphometry and relative energy of the system. Webb Cove, a wide embayment with maximum sample station current velocity of 0.2 m/s, showed a random ebb tide vs. flood tide larval distribution; the narrow, long Damariscotta River estuary with 0.35 m/s current velocity showed a two-fold flood tide larval enhancement and the Jordan River with 1.5 m/s current velocities showed up to a 14-fold flood tide enhancement of mussel larvae and bysally drifting juveniles. Thus certain Maine estuaries may act as larval traps, providing areas of concentrated settlement and seed abundance. Primary setting normally begins with a large initial pulse in June followed by one or more secondary pulses throughout the summer. Secondary settlement (reattachment of bysally drifting juveniles) occurs at lower levels throughout the year, especially in late July and early August. Maximum attachment of larvae and juveniles occurs during periods of maximum current velocity. Extensive eelgrass beds at the mouths of some estuaries (i.e., Jordan River) may be the sites of extensive primary and secondary setting. Great Eastern Mussel Farms, the industry component, guided by these studies, is testing the deployment of live and shell mussel cultch to develop and optimize a new seed procurement system.     

Genetic Variations in Populations from Farms and Natural Habitats of Asian Green Mussel,Perna viridis,in Singapore Inferred from Nine Microsatellite Markers

The Asian green mussel, Perna viridis, has been widely cultured in Southeast Asia as delicious seafood depending on natural spat. We analyzed the genetic diversity and population structure of three populations (two from Singapore and one from Malaysia) from natural habitats and two from Singapore farms, by genotyping a total of 262 adult individuals using nine polymorphic microsatellites. In all five populations, high allelic (number of alleles A = 11.0–14.4,allelic richness Ar = 10.4–13.9) and gene diversity (expected heterozygosity He = 0.73–0.77) were observed, whereas deficiency of heterozygosity (inbreeding index f = 0.08–0.12) was detected in all populations. Genetic differentiation among populations was low (pairwise fixation index ranged from 0.003 to 0.088), but statistically significant. The usefulness of the information about genetic variations for genetic resource management of the populations in wild habitats and farms to keep genetic variation and setting up a breeding program of Asian green mussel was discussed.     

Effect of Timing of Seed Deployment on Growth and Mortality of Oysters, Crassostrea virginica, Affected by Juvenile Oyster Disease (JOD)

Abstract.— Mortality of oysters, Crassostrea virginica , caused by Juvenile Oyster Disease (JOD) has been a chronic problem the northeastern United States since 1988. To assist in identifying potential health management options, the effect of time of spawning and deployment of oysters on resultant growth and mortality was examined in the Damariscotta River, Maine. Broodstock oysters from a line selected for fast growth were spawned at 2-wk intervals between 28 March and 19 July 1995. Duplicate groups of juvenile oysters from each spawn were deployed in floating trays between 23 May and 31 August. Mortality and size of all cohorts were determined from late June to early December. Cumulative mortality of oysters was related to the timing of deployment. Cohorts placed in the river before June or after mid-August had cumulative mortalities of 20% or less. Oysters deployed between 8 June and 18 August had cumulative mortalities ranging from 64–96%. Growth of all cohorts was rapid immediately after deployment but decreased once JOD began to have an effect. Final size of oysters was directly related to age. This study determined that seed oysters placed in the Damariscotta River between June and mid-August will experience high mortality and low growth. Potential management options to reduce JOD impact include 1) early spawning and deployment in May, ensuring that a mean shell height >25 mm is reached prior to August and 2) late spawning and deployment after mid-August to avoid exposure to JOD.     

pH Dependent Growth of Chlorella in a Continuous Culture System 1

Production and growth of a local strain of marine Chlorella sp. was investigated under different pH levels ranging from pH 6.0–8.5 using 200 L capacity algal tubes. The results show that a pH of 6.5 will be most conducive for producing this species in a continuous culture system. The highest production was 136 g/m³/d with a mean of 117 ± 11 g/m³/d at pH 6.5 compared with other pH levels tested. The total fatty acid content was elevated at low pH levels and ω 3 PUFA increased as the pH was lowered from 8.5 to 6.5. The investigations show that algal productivity is considerably higher in the continuous culture system than in any of the other culture systems available.     

贻贝雌性生殖系统的组织学研究

从组织学方面研究了贻贝雌性生殖系统的构造。卵巢壁薄、由外膜和内生殖上皮构成。外膜主要由结缔组绢,意志支上皮和薄层肌肉构成。由其产生的许多延伸物伸入卵巢中把卵巢分成一个个不规则小区。内生死上皮不断增殖平生生殖带,其中含卵原细胞阁阶段雌性生殖细胞和滤泡细胞。卵原细胞较小,核圆形,核仁不明显。初级卵母细胞体积增加,核呈生发泡状,核仁１个,明显。次级卵母细胞卵圆形、细胞体积更大,核仁１个,十分明显。当卵母     

达里湖东北雅罗鱼的生长、死亡和生活史类型的研究

达里湖东北雅罗鱼(Leucisus waleckii)的种群结构参数(体长、体重和年龄)进行测定,估算种群的生长和死亡参数,并研究种群的生活史类型。结果显示:东北雅罗鱼的体长和体重的关系式Wt=0.0281L2t.8152,其vonBertalanffy生长方程各参数为渐近体长L∞=28.9763 cm,渐近体重W∞=366.95 g,生长系数k=0.2586,t0=-0.3237;自然死亡系数M为0.322,总死亡系数Z为0.9386,捕捞死亡系数F为0.6166;生活类型为r-选择。结果表明:作为渔业管理对策,达里湖东北雅罗鱼的起捕年龄应定为3龄以上。     

养殖密度对食用褐鳟Salmo trutta生长和水质的影响

在涌泉水温度5.6~10.5℃下,将体质量(17.52±0.22)g的2龄褐鳟Salmo trutta饲养在流水圆柱形平底玻璃钢(半径45cm,高60cm)水槽中,水深40cm,密度分别为6.8kg/m~3(SD1)、10.4kg/m~3(SD2)、14.0kg/m~3(SD3)、17.5kg/m~3(SD4)、21.0kg/m~3(SD5)和24.5kg/m~3(SD6),每个密度组设3个重复,探讨养殖密度对褐鳟生长的影响。70d的饲养结果表明:本试验范围内的放养密度未显著影响2龄褐鳟的存活率(P0.05),净增重随养殖密度的增加而增大。SD5组褐鳟净增重(116.55g/(m~2·d))最大;SD4组褐鳟的日增重(0.25g/d)、增重率(102.07%)和特定生长率(1%/d)显著高于SD3组(P0.05)。随着养殖密度的增加,溶解氧含量(DO)呈极显著下降趋势(P0.01),SD1、SD2、SD3(10.14~11.84mg/L)组极显著高于SD5、SD6组(9.62~11.53mg/L)(P0.05);养殖29d和50d时SD1组NO_2~-含量(0.02~0.06mg/L)与SD3、SD5、SD6组(0.04~0.06mg/L)差异显著(P0.05),其他时间不显著;36d后SD2、SD3(0.17~0.22mg/L)组的NH4-NT显著低于SD6组(0.25~0.38mg/L)(P0.05)。比较分析认为,2龄褐鳟的最佳养殖密度应为17.5kg/m~3,不要低于10.4kg/m~3。     

Influence of water management,photoperiod and aeration on growth,survival, and early spat settlement of the hatchery-reared green mussel,Perna viridis

In an attempt to induce early spat settlement and improve mussel seed production, this study aims to determine the influence of water management, photoperiod, and aeration, on the growth, survival and settlement of green mussel (Perna viridis). Water in the pediveliger rearing tanks was changed every day, every 3 days and every 5 days for the water-management experiment. Pediveligers were exposed in 24L:0D h (light: dark), 12L:12D h and 0L:24D h conditions for the photoperiod experiment. Three aeration intensities were also tested—mild (10 L h−1), moderate (20 L h−1), and strong (30 L h−1). This study demonstrated that changing water every 3 days was effective in maintaining the rearing water quality and improving the growth and survival of P. viridis larvae. Highest growth and survival rates were observed in P. viridis spats grown in 0L:24D h photoperiod. There was no significant difference in the settlement rate of larvae exposed to different photoperiods. Mild aeration has shown to improve the growth of P. viridis larvae, but higher survival and settlement rates were attained in the strongly-aerated conditions. Therefore, when the larvae start to settle, it is recommended to expose them to darkness, change the water every 3 days and provide a strong aeration to be able to attain high survival and settlement rates, and bigger spats.     

诸暨养殖池塘内水环境、三角帆蚌生长与珍珠产量

2006.06.03-11.08研究了浙江省诸暨市3口蚌养殖池塘内的水温、透明度(SD)、溶氧(DO)、pH等理化因子以及三角帆蚌(Hyriopsis cumingii)生长和珍珠产量。结果显示:实验期间池塘内水温平均为28℃,透明度为24~31 cm,pH为8.5~8.8,DO为6.6~7.8 mg/L,盐度为0.1,Ca2+含量为19.4~37.0 mg/L,总硬度为64.0~123.3 mg CaCO3/L,总碱度为58.4~109.4 mg CaCO3/L,TN为0.76~1.12 mg/L,TP为0.14~0.33 mg/L,TN/TP为4~8,CODMn为9.99~15.5 mg/L。经过158 d生长,池塘内育无核珠或有核珠的3龄蚌蚌壳长增加0.16~0.94 cm,蚌重增加21~61 g;育无核珠的5龄蚌蚌壳长增加0.1~0.25 cm,蚌重增加27~76 g。蚌壳和蚌重生长速度受蚌龄影响,蚌重生长速度的变化幅度往往比蚌壳大。育无核珠的3龄蚌和5龄蚌内珍珠增重分别为每蚌2.03~2.87 g和3.52~5.23 g。3龄蚌蚌壳长和蚌重生长比5龄蚌快,但珍珠产量低于后者,表明三角帆蚌珍珠产量与其蚌壳和蚌重生长速度并不完全一致。     

Growth and Mortality of Ostrea edulis at Two Sites on the Damariscotta River Estuary, Maine, USA

The Damariscotta River estuary is a center of oyster culture in Maine, yet the comparative performance of flat oysters Ostrea edulis at different locations in this now Bonamia ostreae -enzootic estuary has not been assessed. Juvenile O. edulis were deployed in July 1997 among replicate floating trays at one estuarine (Little Point) and one marine site (Lowes Cove), and growth, mortality, and B. ostreae prevalence were compared through December 1999. Growth was faster at Little Point though oysters at both locations reached market size in less than three full growing seasons. Mortality was similar between locations except following a June 1998 rain event that decreased salinity more precipitously at Little Point. Cumulative mortality was greater at Little Point (45.8%) than Lowes Cove (26.7%). Surprisingly, B. ostreae was observed in only a single oyster from Little Point in May 1998. These data indicate that flat oysters in Maine may grow well across a wide range of environments, yet may demonstrate better survival at marine sites where salinity fluctuations are less extreme. While B. ostreae is likely still a threat, selection of sites where rapid growth to market size is possible may reduce its impact.     

日本对虾育苗,养成,加工技术研究

对日本对虾亲虾运输，消毒暂养，催熟，幼体培育，养成，捕捞和活虾运输等全程技术进行了开发。１９９６年５００ｍ＾３育苗水体育出对虾苗４５００万尾，获得利８０余万元；８００亩精养池产虾１万ｋｇ，获利５０余万元，经济效益可观。     

总氮、总磷和钙离子浓度与育珠蚌生长速度的相关性研究

总氮、总磷与钙浓度均是影响育珠蚌生长的主要因素,通过不同处理,进行养殖比较,就三者对蚌生长的相关性程度进行了研究,结果表明:在现有浓度下得出育珠蚌的增重与总氮的偏相关系数为0.998625;总磷的偏相关系数为0.402719;钙离子浓度的偏相关系数为0.995538。     

双齿围沙蚕苗种培育与生态养殖试验报告

针对养殖生产中所存在的关键问题,采取了亲体移植蓄养、强化培育、集中同步产卵技术,运用现代生物技术采取综合生态养殖技术,从而实现双齿围沙蚕苗种培育与生态养殖的规模化生产。2003-2004年连续2年土池育苗均获得成功,其中2004年平均每平方米出苗11刚节以上幼沙蚕3 646条;2004年沙蚕蓄水养殖83．33 hm2(1 250亩),每667 m2 放养幼沙蚕6万-8万条,平均每667m2产沙蚕134．9 kg,获利3 155．2元。