Population structure of the migratory fish Prochilodus lineatus (Characiformes) from rio Grande basin (Brazil), an area fragmented by dams

• 1. Prochilodus lineatus (Prochilodontidae, Characiformes) is a migratory species of great economic importance both in fisheries and aquaculture that is found throughout the Jacuí, Paraíba do Sul, Paraná, Paraguay and Uruguay river basins in South America. Earlier population studies of P. lineatus in the rio Grande basin (Paraná basin) indicated the existence of a single population; however, the range of this species has been fragmented by the construction of several dams. Such dams modified the environmental conditions and could have constrained the reproductive migration of P. lineatus, possibly leading to changes in the population genetic structure.
• 2. In order to evaluate how genetic diversity is allocated in the rio Grande basin, 141 specimens of P. lineatus from eight collection sites were analysed using polymerase chain reaction–restriction fragment length polymorphism (PCR‐RFLP) with 15 restriction enzymes.
• 3. Forty‐six haplotypes were detected, and 70% of them are restricted. The mean genetic variability indexes (h = 0.7721 and π = 1.6%) were similar to those found in natural populations with a large effective size. Fst and Exact Test values indicated a lack of structuring among the samples, and the model of isolation by distance was tested and rejected.
• 4. The haplotype network indicated that this population of P. lineatus has been maintained as a single variable stock with some differences in the genetic composition (haplotypes) between samples. Indications of population expansion were detected, and this finding was supported by neutrality tests and mismatch distribution analyses.
• 5. The present study focused on regions between dams to serve as a parameter for further evaluations of genetic variability and the putative impact of dams and repopulation programmes in natural populations of P. lineatus. Copyright © 2011 John Wiley & Sons, Ltd.

     

人工选育中国对虾两个群体WSSV感染相关免疫与生化因子的变化

通过分析中国对虾人工选育两个群体WSSV感染相关免疫与生化因子的变化，研究选育的两个中国对虾群体对WSSV的敏感性和抵抗力。结果表明，两个群体感染WSSV后，总细胞数（THC）在24h达到最大，随后呈下降趋势；两个群体血淋巴蛋白在感染初期和中期变化不同，但在后期均呈下降趋势；相比而言2＇对虾群体比6＇对虾群体血蛋白含量和THC下降幅度稍慢；2＇对虾群体和6＇对虾群体感染24h后酸性磷酸酶（ACP）稍有下降，随后保持较高的活性，而碱性磷酸酶（AKP）的变化除2＇对虾群体在感染48h有显著增大外，6＇对虾群体变化不明显；过氧化氢酶（CAT）、活性氧（ROS）、超氧化物歧化酶（SOD）与WSSV感染有密切的联系，两个群体抗氧化酶活性随WSSV增殖的变化略有不同；细胞内酚氧化酶（proPO）原变化趋势也表现出差异，斑点杂交结果显示6＇对虾群体比2＇对虾群体阳性反应较早，揭示不同群体间对WSSV感染的敏感性存在一些差异。     

接种密度和面包酵母投喂量对蒙古裸腹溞种群变动和生产量的影响

在室内水槽中进行蒙古裸腹(Moinamongolica)的大量培养,研究不同接种密度和面包酵母投喂水平对该种群变动和生产量的影响。所用蒙古裸腹为20世纪90年代采自山西省晋南半咸水湖、在海水中长期培养保存下的种。实验1中,接种密度分别设为338ind/L、145ind/L和88ind/L3个水平,面包酵母投喂量为5mg/L,每天4次,各设3个重复。实验2中,面包酵母投喂量分别为30mg/(L·d)、20mg/(L·d)和10mg/(L·d)3个水平,蒙古裸腹接种密度为900ind/L,各设3个重复。实验结果表明:(1)在一定范围内蒙古裸腹培养产量随接种密度增加而增加,当接种密度低于88ind/L时,接种的蒙古裸腹较难形成稳定的种群。(2)当使用面包酵母(Bakeryeast)作为培养蒙古裸腹的惟一食物时,食物需要量随种群密度的变化而变化。当密度低于1500ind/L时,适宜的面包酵母投喂水平为20mg/(L·d);当密度超过5000ind/L时为30mg/(L·d)。上述结果显示,接种密度和面包酵母投喂量对蒙古裸腹种群变动和生产量具有重要影响。建议在蒙古裸腹培养生产中接种密度高于150ind/L,面包酵母投喂量为0 8×10-5～1 3×10-5g/(ind·d)。     

Diet shift of larval and juvenile landlocked Ryukyu-ayu <Emphasis Type="Italic">Plecoglossus altivelis ryukyuensis</Emphasis> in the Fukuji Reservoir,Okinawa Island,Japan

ABSTRACT:   The diet shift of larval and juvenile Ryukyu-ayu Plecoglossus altivelis ryukyuensis was investigated for the landlocked population stocked in the Fukuji Reservoir, Okinawa Island. Gut contents of 274 specimens (5.1–31.4 mm in body length) including 31 yolk-sac larvae (5.7–8.0 mm) were examined. The diet of larval and juvenile landlocked P. a. ryukyuensis was mainly composed of zooplankton such as dinoflagellates, rotifers, copepods, and cladocerans. Feeding incidence was 48% in total and it gradually increased with growth. Diet analysis clearly demonstrated a diet shift during the larval and juvenile periods. For yolk-sac larvae and 5.0–19.9 mm fish, the diet was dominated by dinoflagellates Gymnodinium sp., and Peridinium sp., both numerically and by frequency, followed by rotifers that mainly consisted of Polyarthra spp. Diet breadth (Levin's standardized index B_A) diversified with growth, and feeding on copepods and cladocerans gradually increased in 10.0–14.9 mm fish. Diet overlap (Morisita's index: C) showed that diet drastically changed in 20.0–24.9 mm fish with a specialization on cladocerans Bosminopsis deitersi and Diaphanosoma brachyurum . This diet shift probably corresponded with an increase of feeding ability resulting from an enlargement of the mouth, increased swimming ability, and the development of sense organs.     

用判别函数进行鱼类种群鉴别的计算机程序实现方法

用判别函数进行鱼类种群鉴别的计算机程序实现方法陈卫忠，李长松（东海水产研究所，上海２０００９０）关键词判别函数，鱼类种群，鉴别，计算机程序ＡＣＯＭＰＵＴＥＲＩＺＥＤＡＰＰＲＯＡＣＨＴＯＩＤＥＮＴＩＦＩＣＡＴＩＯＮＯＦＦＩＳＨＰＯＰＵＬＡＴＩＯＮＢＡＳ...     

鱼池不同水层细菌的密度、昼夜波动及其与主要环境因子的关系

鱼池细菌的密度为表层高于底层,表、底层细菌密度的差异以夏季最大,冬季次之,春秋两季最小。各季节池塘表层和底层的细菌密度在24h内均呈现一定程度的波动,但经昼夜波动后又大致回到原来水平。细菌密度与水温、COD、浮游动物生物量呈正相关,与浮游植物生物量无直接相关。     

川东北丘陵地区紫山药高产栽培技术研究

紫山药为特色蔬菜新品种,营养价值高。南充作为川东北农业第一大市,首次引进紫山药栽培。我们设计正交试验对其株行距、施肥方案进行研究,形成适合川东北地区气候地理特点的紫山药高产栽培技术,每667 m2产量可达1 700 kg以上,推广前景广阔。     

桂花种植密度调控对生长量的影响

试验采用‘金桂’桂花品种苗木在山坡地种植,在不同生长阶段采用疏移措施调整桂花密度。结果表明：不同生长阶段密度调控对桂花的生长具有极显著影响,以初植密度（株行距）1 m×1 m,在4年树龄及7年树龄时适时疏移2次的生长量最大;初植密度（株行距）2 m×2 m,在树龄6年疏移1次的生长量次之;初植密度（株行距）3 m×3 m,在生长期内不疏移的生长量最小。     

Remedies for pseudoreplication

Pseudoreplication is the failure of a statistical analysis to properly incorporate the true structure of randomness present in the data. It has been well documented and studied in the ecological literature but has received little attention in the fisheries literature. Avoiding pseudoreplication in analyses of fisheries data can be difficult due to the complexity of the statistical procedures required. However, recent developments in statistical methodology are decreasing the extent to which pseudoreplication has to be tolerated. Seven examples are given here, beginning with simple design-based remedies and progressing to more challenging examples including the model-based remedies of mixed-effects modelling, generalized linear mixed models, state-space models, and geostatistics.