Natural hybridization between black spruce and red spruce

Using species-specific random amplified polymorphic DNA (RAPD) markers and morphological characters, natural hybridization between the closely related black spruce Picea mariana (Mill.) B.S.P. and red spruce P. rubens Sarg. was evaluated in natural populations from north-eastern North America. Sampling included populations from both areas of allopatry and also 14 populations from part of the area of sympatry located in the province of Québec and covering several thousands of square kilometres. Classification results from RAPD species-specific markers and from a discriminant function based on morphology were compared. Molecular analysis of the allopatric populations indicated a small amount of interspecific gene leakage with no asymmetric directionality to introgression. A high occurrence of hybrid/introgressant individuals was observed within sympatric populations, suggesting weak reproductive isolation. As expected, the detection of such individuals was more efficient using molecular markers than with morphological traits. The hybrid zone appeared extensive with variable species structure and, in some stands, the main component composed of hybrid/introgressant trees. Implications for the genecology and genetic management of these species are discussed.     

Comparative studies on the feeding selectivity of silver carp Hypophthalmichthys molitrix and bighead carp Aristichthys nobilis

Silver carp and bighead carp exhibited size-selection for food particles in aquarium experiments, but did not select their preferred species of plankton actively when they were distributed evenly in the water. They also possessed the capacity of selection for feeding area. The removal rates (% g⁻¹ fish weight) of silver carp for smaller plankton (phytoplankton) were higher than those of bighead carp. The removal rates by the latter for bigger plankton (zooplankton) were higher than those of silver carp, but for plankton about 70 μm dia. the rates by the two species were almost equal.     

武汉东湖鲢、鳙生长的几个问题的研究

采用退算法研究东湖鲢、鳙的生长,包括生长的基本模式,瞬时生长率及其变动,雌、雄鱼生长的差异等问题:1)鲢、鳙的生长模式可用von Bertalanffy方程来描述,其中鲢的参数l∞=99.8厘米、W∞=17,104克、K=0.3040、t0=0.4821年,鳙的参数l∞=117.6厘米、W∞=29,311克、K=0.3088、t0=0.5392年;2)鲢、鳙的瞬时生长率随着年龄的增长而逐渐下降,并且不同世代同龄鱼的瞬时生长率有一定的变动,其变差系数与年龄呈正相关;3)鲢、鳙的生长无显著的性别差异。通过对研究结果的综合分析,阐述了鲢、鳙4龄前后出现生长的拐折主要由其个体大小所制约,种群的不同世代和同一世代的不同个体一样存在生长补偿作用,以及瞬时生长率与肥满系数之间有着明显的对应关系。所取得的有关参数值可以应用于渔业估算。     

不同日照时数对鲤,鲢,鳙鱼苗生长和存活的影响

不同日照时数对鲤、鲢、鳙鱼苗生长和存活的影响王吉桥,赵德树,张景全（大连水产学院养殖系,１１６０２３）（大连市碧流河水库渔场,１１６４２８）ＥｆｆｅｃｔｏｆＰｈｏｌｏｐｅｒｉｏｄｏｎｔｈｅＧｒｏｗｔｈａｎｄＳｕｒｖｉｖａｌｏｆＳｉｌｖｅｒＣａｒｐ,Ｂ...     

Reproductive condition and occurrence of intersex in bighead carp and silver carp in the Missouri River

Little is known about the reproductive biology of the exotic bighead carp Hypophthalmichthys nobilis and silver carp Hypophthalmichthys molitrix in the Missouri River. In order to fill this gap in understanding, herein is described the reproductive condition of these Asian carps. Evidence is presented which indicates that bighead and silver carp in the Missouri River have a protracted spawning period that extends from early spring through fall and some individual bighead and silver carp are spawning multiple times during a reproductive season. Although bighead and silver carps are successfully maturing and spawning in the Missouri River some reproductive abnormalities such as intersex, atresia, and sterility were observed. Knowledge of the reproductive activity of these invasive carps may be useful to resource managers tasked with their control. Furthermore, the reproductive abnormalities observed should be considered when evaluating the environmental condition of the Missouri River relative to supporting a healthy fish fauna.     

鲤鱼种和鲢鳙对池塘浮游生物的影响

本文根据１９９０年－９月对９个鱼池的研究,报道鲤鱼种和鲢鳙对浮游生物的影响,结果表明：鲤鱼种使浮游植物和浮游动物生物量增加,浮游植物大型化,浮游动物小型化,并使浮游植物多样性增加,浮游动物多样性下降;鲢鳙密度增加,浮生物小型明显,微型藻类和超微在在浮植物中所占比重显著增加,小型浮游动物（原生动物和轮虫）在浮游动物中比重也明显增;鲢鳙密度对浮游生物多样性和浮游生物量的影响具有阶段性,当鲢鳙密度低时,     

Molecular Taxonomy of Cupped Oysters (Crassostrea, Saccostrea, and Striostrea) in Thailand Based on COI, 16S, and 18S rDNA Polymorphism

Genetic diversity of oysters Crassostrea belcheri (Sowerby, 1871), C. iredalei (Faustino, 1932), Saccostrea cucullata (Born, 1778), S. forskali (Gmelin, 1791), and Striostrea (Parastriostrea) mytiloides (Lamarck, 1819) (Ostreoida, Mollusca) was analyzed by polymerase chain reaction – restriction fragment length polymorphism (PCR-RFLP) of 16S ribosomal DNA with AcsI, AluI, DdeI, DraI, RsaI, and TaqI, 18S ribosomal DNA with HinfI, and cytochrome oxidase subunit I with AcsI, DdeI and MboI. A total of 54 composite haplotypes were observed. Species-diagnostic markers were specifically found in C. belcheri, C. iredalei, and S. cucullata, but not in S. forskali and Striostrea mytiloides, which shared common composite haplotypes. Neighbor-joining trees constructed from genetic distances between pairs of composite haplotypes and species indicated large genetic differences between Crassostrea and Saccostrea (including Striostrea mytiloides), but closer relationships were observed within each genus. Four groups of unidentified oysters (Crassostrea sp. and Saccostrea sp. groups 1, 2, and 3) were also genetically analyzed. Fixed RFLP markers were found in Crassostrea sp. and Saccostrea sp. group 2, but not in Saccostrea sp. groups 1 and 3. Phylogenetic and genetic heterogeneity analyses indicated that Crassostrea sp. and Saccostrea sp. group 2 should be considered as newly unidentified oyster species in Thailand.     

Can filter‐feeding Asian carp invade the Laurentian Great Lakes? A bioenergetic modelling exercise

1. There is much concern that filter‐feeding Asian carp will invade the Laurentian Great Lakes and deplete crucial plankton resources. We developed bioenergetic models, using parameters from Asian carp and other fish species, to explore the possibility that planktonic food resources are insufficient to support the growth of silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) in the Great Lakes. 2. The models estimated basic metabolic requirements of silver and bighead carp under various body sizes, swimming speeds and reproductive stages. These requirements were then related to planktonic food resources and environmental temperature to predict when and where silver and bighead carp may survive in the Great Lakes, and how far they may travel. 3. Parameter values for respiration functions were derived experimentally in a coordinated study of silver and bighead carp, while consumption parameters were obtained from the literature on silver carp. Other model parameters lacking for Asian carp, such as those for egestion and excretion, were obtained from the literature on other fish species. 4. We found that full‐sized bighead carp required 61.0 kJ d^?1 just to maintain their body mass at 20 °C, approximately equivalent to feeding in a region with 255 μg L^?1 macrozooplankton (dry) or 10.43 μg L^?1 chlorophyll a. Silver carp energy requirements were slightly higher. 5. When applied to various habitats in the Great Lakes, our results suggest that silver and bighead carp will be unable to colonise most open‐water regions because of limited plankton availability. However, in some circumstances, carp metabolism at lower temperatures may be low enough to permit positive growth even at very low rations. Positive growth is even more likely in productive embayments and wetlands, and the modelled swimming costs in some of these habitats suggest that carp could travel >1 km d^?1 without losing biomass. 6. The simulation (and firmly hypothetical) results from this modelling study suggest when and where Asian carp could become established in the Great Lakes. Given the potential consequences to Great Lakes ecosystems if these filter feeders do prove capable of establishing reproducing populations, efforts to keep Asian carp out of the Great Lakes must not be lessened. However, we do encourage the use of bioenergetic modelling in a holistic approach to assessing the risk of Asian carp invasion in the Great Lakes region.     

太湖梅梁湾大型控藻围栏对浮游甲壳动物群落结构的影响

2005年对太湖梅梁湾大型鲢、鳙控藻围栏内外浮游甲壳动物群落结构的季节变化进行了监测.结果表明:围栏内外的环境因子、浮游植物生物量、浮游甲壳动物种类组成无显著差异.但鲢、鳙放养对浮游甲壳动物的生物量产生了较大的影响,围栏内浮游甲壳动物的总生物量和枝角类的生物量显著低于围栏外.总体上,枝角类各种类的生物量受鲢、鳙放养的影响程度大于桡足类的种类.太湖梅梁湾浮游甲壳动物的季节演替明显,大部分种类只是季节性出现.冬季和春季以溞(Daphnia sp.)和近邻剑水蚤(Cyclops vicnus)等大型种类为主,夏季和秋季以象鼻溞(Bosmina sp.)、角突网纹溞(Ceriodaphnia cornuta)和中华窄腹剑水蚤(Limnoithona sinensis)等小型种类为主.典范对应分析表明,透明度、温度和浮游植物的生物量是影响浮游甲壳动物季节变化的主要因素.     

Development of silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis) genetic maps using microsatellite and AFLP markers and a pseudo-testcross strategy

Silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis) are two of the four most important pond-cultured fish species inhabiting the major river basins of China. In the present study, genetic maps of silver carp and bighead carp were constructed using microsatellite and AFLP markers and a two-way pseudo-testcross strategy. To create the maps, 60 individuals were obtained from a cross of a single bighead carp (female) and a single silver carp (male). The silver carp map consisted of 271 markers (48 microsatellites and 223 AFLPs) that were assembled into 27 linkage groups, of which 22 contained at least four markers. The total length of the silver carp map was 952.2 cM, covering 82.8% of the estimated genome size. The bighead carp map consisted of 153 markers (27 microsatellites and 126 AFLPs) which were organized into 30 linkage groups, of which 19 contained at least four markers. The total length of the bighead carp map was 852.0 cM, covering 70.5% of the estimated genome size. Eighteen microsatellite markers were common to both maps. These maps will contribute to discovery of genes and genetic regions controlling traits in the two species of carp.