Linking habitat selection, emigration and population dynamics of freshwater fishes: a synthesis of ideas and approaches

Abstract –  The consequences of individual behaviour to dynamics of populations has been a critical question in fish ecology, but linking the two has proven difficult. A modification of Sale's habitat selection model provides a conceptual linkage for relating resource availability and individual habitat selection to exploratory behaviour, emigration and population-level responses. Whole-population experiments with pupfish Cyprinodon macularius that linked all factors along this resource to population continuum lend support to this conceptual model, and illustrate that emigration may be much more common in fish populations than considered in most individual- or population-based models. Accommodating emigration can enhance the ecological appropriateness of behavioural experiments and increase confidence in extrapolation of experimental observations to population-level effects. New experimental designs and advancing technologies offer avenues for assessing population consequences of habitat selection and emigration by individual fish. Emigration often is the key linkage between individual behaviour and population responses, and greater understanding of the underlying factors affecting this often-overlooked demographic parameter could offer new approaches for management and conservation of fishes.     

中国对虾抗病群体选育的初步研究

1998年自山东威海外海 1 2 3°E,3 7°N附近海域采捕中国对虾 2 3 0尾 ,经过生产规模的苗种培育繁殖下代。连续 3年从染病存活的对虾养殖池中选留亲虾。结果表明 ,经过选种的后代存活率一年比一年高 ,同一地区 1 3口养殖池的养殖效果也一年比一年好。室内白斑综合症病毒 (White SpotSyndrom Virus,WSSV)感染的实验结果表明 ,选育的第 3代表现出明显的抗病力 ,由此证实中国对虾抗病力具有遗传基础 ,进一步的选育有望培育出抗病毒的对虾新品种     

烟粉虱对3种寄主植物的田间和室内趋性

【目的】研究烟粉虱对3种寄主植物的田间和室内趋性,为采用“推-拉”技术防控烟粉虱提供参考。【方法】以棉花、苘麻和蓖麻为材料,采用田间调查方法,研究烟粉虱对棉花和苘麻趋性。于室内以罩笼选择法,测定该虫对以上3种寄主植物的选择性。【结果】2019年棉田烟粉虱成虫于8月中旬进入高峰期,若虫于8月下旬进入盛期。田埂苘麻8月中旬上、中、下3张叶片上成虫数量达到90.5头/株,田间棉花上达到30.9头/株,8月下旬苘麻上若虫量达到31.7头/株,棉花上有虫14.1头/株;棉田烟粉虱对苘麻有明显的趋性,苘麻上的烟粉虱虫量始终与棉花上存在显著差异,且在8月上中旬,近苘麻的棉花植株上烟粉虱有趋向苘麻的趋势,8月下旬后近苘麻的棉花上烟粉虱虫量也比远离苘麻的棉花上多;有60.6%的烟粉虱趋向于苘麻,棉花上只有27.0%,蓖麻上仅12.4%,苘麻与棉花、蓖麻上的烟粉虱虫量存在显著差异。【结论】苘麻对烟粉虱引诱效果最好。     

基于乡村振兴战略背景下的农业项目选择研究

实施乡村振兴战略是中央解决农业、农村和农民问题的战略决策,也是解决新时代中国社会主要矛盾的必然途径,产业兴旺是乡村振兴的重点,农业项目则是产业兴旺的有机组成部分,进行农业项目选择研究具有现实意义。本文回顾了国内外关于农业项目选择的研究和发展,提出农业项目选择应当考虑:正确价值取向原则、服务原则、政策符合原则、区域资源优势原则、科学技术原则。并对国家政策文件中的"农业项目"或者"项目"的关键词摘取汇表,推荐了当前具有较优选择价值的休闲农场、农村电商、民宿旅游、家庭农场等四种农业项目。     

凡纳滨对虾(Litopenaeus vannamei)抗WSSV选育家系的建立及其抗病特性

2002-2007年在人工感染白斑综合症病毒(white spot syndrome virus, WSSV)的基础上进行一代个体选育（G1）后,对凡纳滨对虾连续进行了4代家系选育,共建立120个抗WSSV家系,感染实验结果表明：G2~G5选育家系对虾平均成活率分别为5.57%±9.83%, 8.66%±11.52%, 9.52%±8.84% 和 13.79%±12.86%;G2~ G5选育家系对虾平均成活率的变异系数分别为1.77、1.40、0.97和0.87。根据每个家系对虾的成活情况可分为敏感、中等抗性和高抗性家系,G2至G5敏感家系在各代选育家系中的比例逐年下降,分别占76.5%、55.2%、51.4%和33.3%,抗病成活率分别为0.44%±1.09%、0.78%±1.70%、2.27%±2.76%和2.44%±3.09%,感染WSSV后2~3 d出现1个急性死亡高峰;中等抗病家系在各代选育家系中的比例逐年上升,分别占0、20.7%、31.1%和38.5%,抗病成活率分别为0、9.08%±1.46%、10.7%±1.41%和11.36%±3.30%,感染WSSV后出现2个死亡高峰,第1死亡高峰值大于第2高峰;高抗家系在各代选育家系中的比例逐年上升（G4除外）,分别占23.5%、24.1%、17.1%和28.2%,抗病成活率分别为22.23%±5.21%、22.7%±12.30%、24.45%±6.56%和28.98%±8.09%,感染WSSV后出现2个死亡高峰,第1死亡高峰至小于第2高峰。经连续的定向选育,选育对虾抗病性状一代比一代强,表现出明显的抗病性能,特别是高抗对虾不仅死亡率低且其死亡高峰推迟2～3d,延缓了对虾WSSV暴发的时间,但是每代每尾对虾平均产卵量逐年下降（P<0.05）。     

Thermal ecology of subadult and adult muskellunge in a thermally enriched reservoir

The movement of adult muskellunge, Esox masquinongy Mitchill, has been investigated in a variety of systems, but temperature selection by muskellunge has not been examined where well‐oxygenated waters were available over a range of temperatures for much of the year. Thirty subadult and adult muskellunge tagged internally with temperature‐sensing radio tags were tracked from March 2010 to March 2011 in a Tennessee reservoir. Mean tag temperatures were 18.9 °C in spring (March to May), 22.1 °C in summer (June to August), 16.5 °C in autumn and 9.8 °C in winter (December to February). When the greatest range in water temperatures was available (7.1–33.3 °C; May to early August 2010), their realised thermal niche (mean ± 1 SD) was 22.3 °C ± 1.8; the realised thermal niche was affected by fish size (smaller fish selected slightly warmer temperatures) but not sex. An electric generating steam plant discharging warm water resumed operation in January 2011, and most (86%) tagged fish occupied the plume where temperatures were ≈10 °C warmer than ambient water temperatures. No mortalities were observed 15 days later when plant operations ceased. Their affinity for the heated plume prompted concerns that muskellunge will be too easily exploited when the plant operates during winter.     

浅谈沥青混合料搅拌设备选型问题

通过对目前各种沥青搅拌设备性能的比较和分析,确认设备选型的方法。     

松浦镜鲤与德国镜鲤选育系（F4）的可量性状、鳞片数比较

对松浦镜鲤（SP）和德国镜鲤选育系（F4）（DJ）的可量性状及体表鳞片数进行比较,SP与DJ的可量性状与体表鳞被存在差异。SP的体长／体高（2．44±0．15）、头长／眼间距（2．24±0．08）明显小于DJ,体长／头长（3．86±0.20）、头长／吻长（2．99±0．23）明显大于DJ,SP体表的鳞片数明显少于DJ。结果表明,从DJ到SP遗传选育过程中,体型和鳞片的变化已达到了选育目的。     

A synthetic control approach to estimate the effect of total allowable catches in the high seas

Total allowable catch restrictions (hereafter referred to as catch quotas) play an important role in maintaining healthy fish stocks. While studies have identified a positive relationship between catch quota implementation and improved stock status, these methods are subject to selection bias as catch quotas are typically applied to stocks that are depleted. We address this challenge using the synthetic control method, which estimates the causal effect of catch quotas on fishing mortality and biomass by predicting a synthetic counterfactual outcome. We focus on high seas stocks (tunas, billfishes, and sharks) managed by tuna Regional Fisheries Management Organizations (tRFMOs), first providing an overview of stock status and current management measures in place. We find that implementation of catch quotas by tRFMOs has more than doubled over the past decade. Second, we predict the hypothetical fishing mortality and biomass trajectory for seven high seas quota-managed stocks in absence of a catch quota. These “synthetic non-quota stocks” are predicted using a weighted selection of high seas non-quota stocks. Credibility of the synthetic non-quota stocks is evaluated through diagnostic checks, and robustness tests assess sensitivity to study design. Five credible fishing mortality synthetic controls are predicted: three add support to the hypothesis that catch quotas successfully reduce fishing mortality, while two find that catch quotas increase fishing mortality. While our analysis is limited in scope, given that all seven quota-managed stocks are managed under a single tRFMO, we highlight the potential for the synthetic control method in fisheries management evaluation.