A size-structured model for a stock-recovery program for an exploited endemic fisheries resource

The size of harvests temporarily decreases following stock-recovery programs for overexploited resources. The process of stock recovery is quite uncertain, because of unknown life-history parameters, changes in environmental conditions, and human impact. To project future stock recovery, we considered a size-structured matrix model of a stock-recovery program, in which the minimum body size in the first harvest is increased. We applied some common concepts, including yield per recruitment, spawning per recruitment, and reproductive value, to a size-structured matrix model that incorporated economic discounting. The size-structured model predicted the following characteristics in stock-recovery processes: several years must pass for the harvest to increase, and the time-lag between the inception of the management program and the increase in the catch is caused by intergenerational momentum in demography. We also investigated the effects on the recovery process of temporal environmental fluctuations. We applied our model to a stock-recovery program of the corbiculid Seta clam (Corbicula sandai) in Lake Biwa, Japan.     

河蚬的耗氧率和排氨率

本试验研究了在饱食状态下各种大小的河蚬在下不同温度下的耗氧率和排氨率及其昼夜变化的特征。结果表明,温度和河蚬的个体大小均对其耗氧率和排氨率有显著影响。其中,河蚬耗氧率与其体重之间呈幂函数关系,排氨率与其体重之间呈指数函数关系;而温度对河蚬耗氧率和排氨率的影响,则表现为,在一定的温度范围内,河蚬的耗氧率和排氨率,随温度的升高而增加,超过某一温度,则随温度的的升高而降低。还发现,河蚬的耗氧率存在着明显     

浙江地区3种淡水经济贝类的营养成分分析与评价

采用国标方法对浙江地区的河蚬、环棱螺和圆田螺的营养成分进行分析并进行评价,以期为贝类的营养研究、饲料生产和开发利用提供理论依据。结果表明,环棱螺和圆田螺的水分、灰分、粗蛋白和粗脂肪的含量较为接近,而糖类的含量有较大差异;河蚬与环棱螺和圆田螺在主要营养成分组成方面差异较大。氨基酸分析结果表明,3种淡水经济贝类均含有18种氨基酸,其中包括人体必需的8种氨基酸,第一、二限制性氨基酸分别为缬氨酸和异亮氨酸。此外,谷氨酸含量远高于其他氨基酸,环棱螺中高达115.88 mg/g,圆田螺中也高达98.68 mg/g,2种螺肉的呈味氨基酸接近,含量均达40 %以上。环棱螺和圆田螺的总氨基酸含量分别为653.28 mg/g 和561.67 mg/g,必需氨基酸占总氨基酸的比例均在35 %左右,与WHO/FAO模式推荐的模式（35.38%）接近。因此,3种淡水经济贝类软体部分的营养组成丰富,氨基酸种类齐全、比例均衡,具有较好的开发和利用价值。     

藻种、贝类密度和大小对背角无齿蚌和河蚬摄食率的影响

在水温为(20±1)℃的室内实验条件下,研究铜绿微囊藻(Microcystis aeruginosa)、小球藻(Chlorella pyrenoidosa)、斜生栅藻(Scenedesmus obliquus)3种藻类和贝类规格(身体大小)及密度对背角无齿蚌(Anodonta woodiana)和河蚬(Corbicula fluminea)摄食率的影响。三因素方差分析表明:藻种对背角无齿蚌的摄食率无显著影响,但显著影响河蚬的摄食率;贝类密度和规格均显著影响2种贝类的摄食率,两者对背角无齿蚌摄食率有交互作用;但对河蚬无交互作用;2种贝类摄食率均随着密度的增加而下降,大规格背角无齿蚌和2种较低密度下的大规格河蚬的摄食率均分别显著小于小规格,但在2种较高密度下的河蚬摄食率在规格间无显著差异;2种贝类摄食率与水体溶解氧均显著正相关,但相关性河蚬明显高于背角无齿蚌;不同藻类的投喂对溶解氧不产生显著影响,但贝类大小和密度显著影响溶解氧。结果表明,溶解氧胁迫程度会影响身体大小和密度对2种贝类摄食率的交互作用,小规格河蚬对低溶解氧的耐受性低于大规格。     

黄河三角洲河蚬软体部营养成分的分析及评价

对黄河三角洲流域分布的河蚬软体部营养成分进行了分析,综合评定其营养价值.结果表明,河蚬软体部干样中,粗蛋白、粗脂肪、灰分含量分别为53.90%、8.90%和1.33%;共测到了17种氨基酸,必需氨基酸占氨基酸总量的37.44%,大部分必需氨基酸分(AAS)在40分以上,含硫氨基酸(半胱氨酸+蛋氨酸)为第一限制性氨基酸, 色氨酸得分最高为124.00分;共分析了10种主要脂肪酸,其中EPA、DHA含量分别占7.62%和8.61%.河蚬富含钙、钠、镁、钾、铁等11种无机元素,维生素A、B含量也较丰富.对紫彩血蛤的脂肪酸组成及含量进行了检测, 其中EPA、DHA含量分别占15.23%和6.45%.     

上海淀山湖内河蚬（Corbicula fluminea）的分布与种群生长的初步研究

2010年6月28日通过取样调查研究了上海市淀山湖沿岸及周边河道内河蚬的分布状况,发现湖内西南方向沿岸区域河蚬分布较多(平均密度62.3个/m2,生物量62.7 g/m2),而东北方向沿岸区域河蚬分布较少(平均密度13.8个/m2,生物量12.8 g/m2),位于东南侧的河道内河蚬密度最大,达到318.5个/m2,生物量225.2 g/m2。2011年1-12月通过按月取样对淀山湖内河蚬群落的生长繁殖特征进行了研究和分析:仔蚬(壳长<8 mm)在6月份大量出现,指示6月为淀山湖内河蚬的繁殖高峰期,仔蚬在1年后壳长生长至19mm,2年后壳长生长至27 mm,2年之后仍然存活的个体比例很低。估计淀山湖内河蚬在开始底栖生活之后的生命周期约为2～3年,理论上最大壳长为30 mm,实际最大壳长为34 mm。淀山湖河蚬的分布及生长数据将对于此区域河蚬资源保育工作的开展提供重要的依据。     

Shell growth and age determination of the brackish water bivalve Corbicula japonica in Lake Shinji, Japan

ABSTRACT:   Shell growth and age determination of Corbicula japonica were investigated from samples collected monthly at two sites and field growth experiments from November 1999 to November 2000 in Lake Shinji. Both specimens did not grow in winter when the water temperature was below 11°C, but grew rapidly from spring to early summer when the water temperature rose from 15°C to 30°C, before further growing slowly from summer to autumn after the main breeding period. The monthly marginal growth distribution of the samples indicated that the concentric groove on the shell surface was an annual growth ring. It is concluded that the age of C .  japonica in the i -ring group when the shell growth resumed in spring was i  + 0.5 ( i  = 1, 2, · · ·), because the first true growth ring was formed at 0–2 mm in shell length, which then faded with growth. Lee's phenomenon was observed in the age determination results, and thus the growth coefficient and the asymptotic shell length of the von Bertalanffy growth equation were not estimated from the samples. However, these parameters were estimated from the annual shell length increments of the experimental individuals, which were 0.331/year and 28.2 mm, respectively.     

水环境中Cd和Cu污染对监测生物河蚬积累效应的影响

以河蚬作为指示生物,采用室内培养方法,研究了不同浓度的 Cd和 Cu的单独及联合作用的毒性效应.结果显示,在水体中浓度为 10、 20、 30、 40、 50 μ g· L-1的 Cd与 Cu单独作用下,河蚬体内 Cd与 Cu的含量分别与其在该环境中的暴露时间和浓度呈显著正相关.在同样浓度的 Cd与 Cu共同存在的环境中,河蚬体内的 Cd与 Cu的含量仍与环境中该物质的浓度呈显著正相关,且随着暴露时间的延长均表现出对污染物质积累的增加.初步建议河蚬可作为淡水中重金属污染的监测指示生物.