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

Julia Margaret Lawson  Conner Muir Smith 《Fish and Fisheries》2023,24(4):635-651

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.  相似文献   

A comparison of crop data measured by two commercial sensors for variable-rate nitrogen application     

Nicolas Tremblay  Zhijie Wang  Bao-Luo Ma  Carl Belec  Philippe Vigneault 《Precision Agriculture》2009,10(2):145-161

Nitrogen (N) fertilizer rates applied spatially according to crop requirements can improve the efficiency of N use. The study compares the performance of two commercial sensors, the Yara N-Sensor/FieldScan (Yara International ASA, Germany) and the GreenSeeker (NTech Industries Inc., Ukiah, California, USA), for assessing the status of N in spring wheat (Triticum aestivum L.) and corn (Zea mays L.). Four experiments were conducted at different locations in Quebec and Ontario, Canada. The normalized difference vegetation index (NDVI) was determined with the two sensors at specific growth stages. The NDVI values derived from Yara N-Sensor/FieldScan correlated with those from GreenSeeker, but only at the early growth stages, where the NDVI values varied from 0.2 to 0.6. Both sensors were capable of describing the N condition of the crop or variation in the stand, but each sensor had its own sensitivity characteristics. It follows that the algorithms developed with one sensor for variable-rate N application cannot be transferred directly to another sensor. The Yara N-Sensor/FieldScan views the crop at an oblique angle over the rows and detects more biomass per unit of soil surface compared to the GreenSeeker with its nadir (top-down) view of the crop. The Yara N-Sensor/FieldScan should be used before growth stage V5 for corn during the season if NDVI is used to derive crop N requirements. GreenSeeker performed well where NDVI values were >0.5. However, unlike GreenSeeker, the Yara N-Sensor/FieldScan can also record spectral information from wavebands other than red and near infrared, and more vegetation indices can be derived that might relate better to N status than NDVI.  相似文献   

滨海盐碱地改良研究现状及展望   总被引：1，自引：0，他引：1  

赵英  王丽  赵惠丽  陈小兵 《中国农学通报》2022,38(3):67-74

在中国东部耕地资源紧缺、人地供需失衡的背景下,迫切需要增加耕地,保证"占补平衡".滨海盐碱地作为一类潜在的土地后备资源,其合理开发利用对缓解土地资源不足的压力、提高农业水资源利用效率和生态系统稳定性具有重要的战略与现实意义.本文介绍了滨海盐碱地的资源现状及主要特点,从物理、化学、水利工程、生物4个方面总结了当前滨海盐碱...  相似文献   

许昌市古树名木的现状与保护措施     

李留振  王燕军  薛金国  董文辉  盛瑞琦 《中国城市林业》2007,5(5):56-58,55

对许昌市古树名木普查建档,已查清古树名木298株,其中国家一级古树103株,二级古树54株,三级古树138株,同时还查明了古树名木的生存现状和存在的主要问题,并提出相应的保护措施。    相似文献   

徐州市不同功能城区绿地土壤的理化性质分析   总被引：7，自引：0，他引：7  

于法展  尤海梅  李保杰  赵文 《水土保持研究》2007,14(3):85-88

以徐州市三环路内不同功能区的绿地土壤为研究对象,通过对城区土壤的理化性质与养分状况等指标进行测定分析,并与该地区自然土壤进行了对比,研究其变化的趋势.结果表明:该绿地土壤的容重较大,孔隙度和田间持水量少,有机质缺乏,养分含量不均,pH值明显向碱性的方向演变.  相似文献   

我国植物源农药研究进展   总被引：5，自引：1，他引：4  

袁文金  马德英  郭冬雪  姜运涛  张帆  羌松 《新疆农业科学》2007,44(6):892-897

随着人们对化学农药的高毒、高残留、害虫抗药性、杀伤天敌、环境污染、危害人类健康等问题的广泛关注,研究和开发环境友好农药成了人们的迫切需要,生物农药特别是植物源农药成了研究热点.概述了发展植物源农药的时代背景及其必要性;植物源农药的特点、种类、研究现状、开发模式及目前存在的一些问题,并对其发展趋势做了一个简单的展望.  相似文献   

中国动物科学的研究现状与发展趋势   总被引：1，自引：0，他引：1  

彭建军  邓飞 《中国农学通报》2006,22(11):8-8

通过叙述动物科学的起源和重要性、在自然科学和社会生活中的地位和意义,介绍国内外动物学的研究现状和国际动物科学的发展趋势,指出中国动物科学在总体上与国际先进水平的差距,提出中国动物科学研究的近期和长远发展目标、原则和研究对策。  相似文献   

中国休闲农业的现状与趋势   总被引：7，自引：1，他引：6  

冀献民 《中国农学通报》2007,23(12):456-456

中国休闲农业发展迅速。目前,全国休闲农业特色农户（农家乐）已发展至150多万家,具有一定规模的休闲农业园区发展至12000多家,直接从业人员近300万人,年接待游客7亿人次,年经营收入达900亿元左右。已成为农业和农村经济发展的亮点之一,彰显出广阔的发展前景,必将成为中国特色农业现代化建设和农民增收的重要举措。当前应着力解决好基础设施条件差,人才队伍短缺,规划滞后,特色不突出,管理不规范,服务水平不高等问题。  相似文献   

腐殖酸结合汞的研究现状   总被引：2，自引：1，他引：1  

余贵芬  青长乐  牟树森 《农业环境科学学报》2000,19(4):255-266

综述了近20年来国内外对腐殖酸结合汞的研究成果。腐殖酸在土壤中虽然含量不高 ,但结合汞的容量大 ,且结合汞后有一定的活性。并指出 ,人们对腐殖酸结合汞是抑制还是活化土壤汞的认识分歧在于腐殖酸组分对汞的络合能力和络合物稳定性存在差异。  相似文献   

甘肃省草产业发展现状与分析思考     

朱倩 《中国牛业科学》2021,47(4):62-64

饲草料作为发展畜禽养殖必不可少的物质,在畜牧业发展中占有着重要的位置,是畜牧业发展壮大的重要基础支撑。甘肃省气候类型复杂、草地类型众多、可利用饲用植物达743种,饲草资源多样,加之有着悠久的牧草种植传统,饲草料产业得到了长足的发展,成为了地方经济产业发展的重要组成部分。为全面掌握全省草产业发展现状,在分析发展优势的基础上,增强产业发展后劲,本文就2016—2019年的草产业发展情况进行分析,摸清了发展底数,为下一步稳定发展草产业,加速相关产业的有效融合提供一定的参考。  相似文献