Accuracy of a machine-vision pellet detection system

Video cameras are employed on net pen fish farms for monitoring food pellet levels near the cage bottom. Herein, the accuracy of a new machine-vision system for the identification of a feed-wastage event and its response time are reported. Research involved novel tests and definitions, video footage recorded under different stocking and environmental conditions, and numerical filters to reduce the effects of misclassifications and patchiness of the pellet wastage record on overall system accuracy. Single-frame food pellet detection accuracy was based on the difference between computer-generated and actual frame counts of pellets greater than 30 pixels in size. A pellet wastage event was defined as a median of three or more visible pellets per frame. During tests on still video frames from different feeding events, the system missed 0.1±0.1 to 1.3±0.4 pellets frame⁻¹, and miss-classified as pellets 0±0.1 to 2.3±0.5 objects frame⁻¹ (n=264). Most missed pellet images were on top of fish images. Waste matter accounted for 65% of the misclassifications, while particles associated with poor camera maintenance accounted for approximately 24%. The average response time to a pellet wastage event was 5.1 and 11.4 s for sampling rates of 2 frames s⁻¹ and 0.5 frames s⁻¹, respectively (n=20 different pellet wastage events). The longest response time (26 s) occurred when fish were amassed against the camera and/or covering pellets. Using appropriate camera lens, camera positioning and/or ‘warning’ software can address fish-interference problems.     

东祁连山高寒草甸土壤酶活性及其化学计量特征对海拔和坡向的响应

研究高寒草甸微尺度海拔和坡向下土壤酶活性及其化学计量特征的变化对于探讨草地生态系统养分循环过程具有重要的生态学意义。以东祁连山高寒草甸为研究对象,分析了7个海拔（2 800,3 000,3 200,3 400,3 600,3 800,4 000 m）和2个坡向（阴坡、阳坡）高寒草甸的土壤酶活性、化学计量特征变化规律及其与土壤理化因子之间的关系。结果表明：海拔和坡向的交互效应对土壤亮氨酸氨基肽酶（LAP）、β-葡萄糖苷酶（BG）、多酚氧化酶（PPO）和过氧化物酶（POD）酶活性、lnBG/ln （NAG+LAP）、lnBG/lnAP和ln （NAG+LAP）/lnAP有显著影响;LAP、AP、BG、POD、lnBG/ln （NAG+LAP）、lnBG/ln （NAG+LAP）随海拔的升高呈先升高后降低,β—1,4—乙酰基氨基葡萄糖苷酶（NAG）和PPO随海拔升高而降低;同一海拔,阳坡土壤AP、BG、POD、PPO酶活性低于阴坡,阳坡土壤NAG酶活性高于阴坡,海拔3 800 m以下阳坡LAP酶活性低于阴坡,除海拔3 000 m和4 000 m外的其他海拔阳坡的土壤lnBG/ln （NAG+LAP）高于阴坡,海拔3 000~3 400 m的土壤lnBG/lnAP和海拔3 000~3 600 m的土壤ln （NAG+LAP）/lnAP在阳坡低于阴坡。相关分析发现,土壤酶活性及其化学计量特征不同程度受土壤C、N、P资源及土壤水分条件等的调控,土壤含水量和有机碳是影响土壤酶活性的主要因子。综上,土壤酶活性及其化学计量特征在微尺度海拔和坡向上具有差异性,且受土壤C、N、P资源及土壤水分条件的综合影响,以土壤含水量和有机碳尤为突出。     

Pollution of Environmental Endocrine Disrupting Chemicals(EDCs) in Water and Its Adverse Reproductive Effect on Fish

越来越多的环境内分泌干扰物（ EDCs）不断释放到环境,并通过大气沉降、地表径流、土壤淋溶和直接排放等方式进入水体,从而使水体成为 EDCs 存在的主要场所之一。为引起社会对水体 EDCs 污染的广泛关注,并积极采取EDCs 危害防治措施,保护鱼类资源和水生态系统,本文介绍了 EDCs 的分类,详述了自然水体、饮用水源水以及自来水中EDCs 污染情况,阐明了 EDCs 对鱼类的生殖危害。资料分析显示,EDCs 能够扰乱生物体内分泌功能,导致生殖器官、生殖机能和生殖行为异常,引起生育力下降,甚至生物繁殖机能损害,并最终导致种群数量下降,以至物种灭绝。虽然国内外已经开展了一些关于 EDCs 对生物危害等方面的研究,但大都处于起步阶段,存在着基础研究薄弱、识别和鉴定困难或代价太大等问题,有关工作亟需全面、深入开展。     

饲料磷脂对仔稚鱼营养生理的研究进展

近年来,磷脂(Phospholipids,PL)在仔稚鱼营养生理所发挥的作用引起人们广泛重视。综述了近年来饲料磷脂对仔稚鱼生长表现、消化道、骨骼发育以及脂肪代谢等方面的影响,以期为磷脂在水产苗种饲料中合理添加与应用提供理论参考。     

不同坡度及坡向条件下的土壤侵蚀特征研究——以淮河北部支流低山丘陵区为例

借助RS和GIS技术获取研究区土壤侵蚀的相关影响因子,运用RUSLE土壤侵蚀模型,计算研究区土壤侵蚀模数,进行侵蚀强度分级,并探讨不同坡度和坡向条件下的土壤侵蚀特征。结果表明,研究区平均土壤侵蚀模数为1 173.755 t/(km2·a),年侵蚀总量约9.56×107t;约96%的区域为微度侵蚀;轻度以上侵蚀主要发生在西部和北部的低山丘陵区,侵蚀土壤面积占总面积的3.32%,但泥沙流失量的比重为72.024%,是防治水土流失的关键区域;随着坡度的增加,侵蚀面积呈先减小后增大而后又减小的趋势,8°~15°坡度带是土壤侵蚀状况的转折点;不同坡向条件下,土壤侵蚀面积由大到小的顺序为半阳坡、阳坡、阴坡和平地,半阳坡侵蚀面积约占总侵蚀面积的50%。     

坡向与坡位对雷竹竹笋产量的影响

采用随机区组试验设计法调查雷竹在不同坡向与坡位的生长情况,共调查45个雷竹标准地,统计结果为出笋数14 625~26 625个/hm2、鲜笋产量1.90~7.11 t/hm2、平均单笋重120.2~298.9 g。通过对比分析,结果表明:坡向和坡位对雷竹的出笋数、鲜笋产量和平均单笋重均有极显著影响,坡向与坡位处理之间交互作用引起的鲜笋产量存在极显著差异。经营雷竹林宜选择东南或西南坡、下坡的组合或南坡、下坡组合为好。本文为雷竹造林时选择适生坡向和坡位提供了参考。     

Fish larvae: zooplankton relationships in microcosm simulations of earthen nursery ponds. II. brackish water system

A simulation of the effects of predation intensity on zooplankton composition in brackish water nursery ponds was carried out in order to address the problem that commercial fish nurseries encounter in obtaining enough zooplankton of adequate species composition and size when fish larvae start to feed. The experimental system consisted of twelve 130 l containers with treatments of four densities (0, 1, 2, or 4 larvae l⁻¹) of common carp (Cyprinus carpio L.), stocked on the 6th day after filling the containers. Zooplankton-environment relationships were explored using factor analysis. Factor analysis allowed identifying several groups of zooplankters that responded in different ways to fish larvae predation pressure. The first factor represented a general measurement of rotifer abundance, and the second identified the direct effect of size-selective fish predation. Since no rotifers were present in the filling water, all these species were autochthonous populations that hatched from resting forms in the sediment and reproduced. In the absence of fish predation, this led to a steep rotifer increase. Fish predation started when the rotifer concentration was just starting to increase and their direct predation reduced and delayed the rotifer abundance peak. This effect increased with the increase in fish larvae density. Estimations of rotifer consumption by fish larvae in this experiment were higher than similar calculations from data of the literature, which led us to test the hypothesis that factors other than direct predation were affecting rotifer population dynamics. The mechanisms involved in rotifer population regulation are discussed. It was concluded that in commercial nurseries, increased larvae production can be achieved by keeping the larvae density at an intermediate level and stocking fish to match the increasing phase of the rotifer peak. Under reasonable larvae density (up to 2 l⁻¹) it seems that the direct predation effect of fish larvae on rotifer dynamics is minor, compared to fish induced self regulation.     

亚热带水产养殖寒灾预警系统的设计与实现

通过对亚热带水产养殖现状的分析，论述了亚热带水产养殖寒灾预警系统建设的必要性、研究的目标和任务，详细介绍了系统的结构和框架，以及亚热带水产养殖寒灾预警的几个关键问题及其解决方法。     

鱼精粉在肉鸡日粮中替代进口鱼粉的效果

选用ＡＡ肉鸡进行试验，试验在生产后期进行，试验分为两组：对照组（含有３％的秘鲁鱼粉）和试验组（含有３％的鱼精粉），两组的营养水平接近。试验组平均日增重为４７．１８ｇ，对照组为４７．０６ｇ；试验组的料肉比为２．６８４，对照组为２．７４５。两者的重要生产性能指标接近，差异不显著。试验结果表明，在生长后期的肉鸡日粮中，使用鱼精粉替代进口鱼粉并不影响试验鸡的生产性能。     

浙江鱼粉和秘鲁鱼粉氨基酸对鸡的消化率比较

本试验以去盲肠鸡和正常鸡各１６只测定了浙江鱼粉和秘鲁鱼粉的氨基酸表观消化率（ＡＡＡＤ）和真消化率（ＴＡＡＤ）。结果表明，以去盲肠鸡测定，浙江鱼粉多数氨基酸的ＡＡＡＤ和ＴＡＡＤ超过秘鲁鱼粉（Ｐ＜０．０５）。以正常鸡测定，两者大多数氨基酸消化率无显著差异（Ｐ＞０．０５）。说明新鲜优质浙江鱼粉的氨基酸可消化性与进口鱼粉相当，甚至更优