An evaluation of statistical methods for estimating abundances of migrating adult sea lamprey

We evaluated statistical methods for estimating abundances of adult sea lamprey (Petromyzon marinus) migrating in Great Lakes tributaries. The sea lamprey is the target of a basin-wide, bi-national control program. Abundance estimates from mark-recapture data are used to evaluate program success and the efficiency of sea lamprey trapping. Recent tracking studies suggested the mark-recapture estimates of abundance could be biased. We compared four estimators of abundance using stratified (weekly) mark-recapture data for 19?years of trapping in the St. Marys River. Abundances from the pooled Petersen estimator were similar to abundances from the stratified Schaefer and stratified Petersen estimators, but substantially lower than abundances from a stratified Bayesian P-spline estimator. In simulations of virtual populations, pooled Petersen and Bayesian P-spline estimates were similar across a range of conditions where catchability differed between marked and unmarked lamprey and changed over the trapping season, with one exception. Abundances from the Bayesian P-spline estimator were strongly positively biased when catchability of marked lamprey increased over the season, while catchability of unmarked lamprey did not. Estimates from both estimators were negatively biased when lamprey displayed consistent individual differences in catchability and positively biased when a proportion of marked lamprey fell back. Discrepancies between mark-recapture and tracking studies cannot be reconciled by the choice of abundance estimator, but could be an outcome of bias due to individual differences in catchability. Sea lamprey managers could also switch from the stratified Schaefer to the pooled Petersen estimator to simplify field operations without losing accuracy and precision.     

Contribution of manipulable and non-manipulable environmental factors to trapping efficiency of invasive sea lamprey

We identified aspects of the trapping process that afforded opportunities for improving trap efficiency of invasive sea lamprey (Petromyzon marinus) in a Great Lake's tributary. Capturing a sea lamprey requires it to encounter the trap, enter, and be retained until removed. Probabilities of these events depend on the interplay between sea lamprey behavior, environmental conditions, and trap design. We first tested how strongly seasonal patterns in daily trap catches (a measure of trapping success) were related to nightly rates of trap encounter, entry, and retention (outcomes of sea lamprey behavior). We then tested the degree to which variation in rates of trap encounter, entry, and retention were related to environmental features that control agents can manipulate (attractant pheromone addition, discharge) and features agents cannot manipulate (water temperature, season), but could be used as indicators for when to increase trapping effort. Daily trap catch was most strongly associated with rate of encounter. Relative and absolute measures of predictive strength for environmental factors that managers could potentially manipulate were low, suggesting that opportunities to improve trapping success by manipulating factors that affect rates of encounter, entry, and retention are limited. According to results at this trap, more sea lamprey would be captured by increasing trapping effort early in the season when sea lamprey encounter rates with traps are high. The approach used in this study could be applied to trapping of other invasive or valued species.     

Evaluation of harassment of migrating double-crested cormorants to limit depredation on selected sport fisheries in Michigan

Diverse management techniques have been used to mitigate conflicts between humans and double-crested cormorants (Phalacrocorax auritus) including harassment methods supplemented by lethal take. In this study we evaluated impacts of programs to harass spring migrating cormorants on the walleye (Sander vitreus) fishery in Brevoort Lake and the yellow perch (Perca flavescens) and walleye fisheries at Drummond Island. Cormorant foraging declined significantly (p < 0.05) at both locations subsequent to initiation of harassment programs. Overall harassment deterred 90% of cormorant foraging attempts while taking less than 6% lethally on average at each site. Yellow perch were a predominate prey item in number and biomass at both locations. Walleye made up a small proportion of the diet at both locations. However, both walleye and yellow perch abundance increased significantly (p < 0.05) at Drummond Island. Walleye abundance at age 3 increased to record levels in 2008 following 3 years of cormorant management at Brevoort Lake. The estimated cormorant consumption of age-1 walleye in the absence of management at Brevoort Lake during 2005 would account for 55% of the record 2006 age-1 walleye population. These results support the hypothesis that cormorant predation on spawning aggregations of sportfish was a significant mortality factor and cormorant management reduced sportfish mortality and increased abundance at both locations. Continuation of harassment programs and fishery assessments will determine whether improvement of targeted sport fisheries through control of spring migrating cormorants is sustainable.     

长江九江河段河势演变及治理探讨

对九江河段历史的和近期的演变分析表明,该河段由于受来水来沙及上游河势变化的影响,深泓有一定的摆动幅度,由此引起潜洲、边滩、浅滩出现相应的冲淤变化,以致影响船舶停靠和通航.对该河段进行治理,一方面可通过挖泥疏浚来缓解目前的矛盾;另一方面,从长运考虑应实施综合治理工程来彻底根治目前九江河段存在的问题.     

谈小水电输、配电变压器的接地措施

对农村小水电站输、配电变压器的接地措施作了介绍，并叙述了接地的目的和要求。     

三工河流域下游灌区竖井排灌效应分析

对222团竖井排灌治理土地盐碱化的水文地质效应分析,得出竖井排灌工程在本区降低潜水埋深较为显著,灌溉条件下农田土壤脱盐使潜水矿化度升高.同时竖井排灌即排水灌溉又可减轻土地盐碱化对干旱区农业生产的双重作用是适宜高效的.     

Use of chemosensory cues as repellents for sea lamprey: Potential directions for population management

Sea lamprey invaded the Great Lakes in the early 20th century and caused an abrupt decline in the population densities of several native fish species. The integrated management of this invasive species is composed of chemical (lampricide) applications, low-head barrier dams, adult trapping and sterile male release. Recently, there has been an increased emphasis on the development of control methods alternative to lampricide applications. We propose as an alternative-control method the use of chemosensory cues as repellents for sea lamprey population management. Based on the available evidence at this time, we suggest that injury-released chemical alarm cues show promise as repellents for sea lamprey and further research should be directed at determining whether sea lamprey show an avoidance response to these types of chemosensory cues. From a management perspective, these chemosensory cues could be used to restrict sea lamprey access to spawning grounds. Repellents could also be used together with attractants like sex pheromones to manipulate sea lamprey behavior, similar to the “push–pull” strategies utilized with insect pests.     

Implications of tagging effects for interpreting the performance of sea lamprey traps in a large river

Abundance estimates can be crucial for managing species of economic concern. The accuracy of these estimates can depend on the methods used to track animals and to estimate abundance from tracking data. We tested experimentally if disparate estimates of trapping efficiency calculated for sea lamprey (Petromyzon marinus) in the St. Marys River near Sault Ste. Marie, Canada could be explained by effects related to the invasiveness and handling involved in tagging or the tag size used in the marking procedures. Trapping is used to gauge adult abundance, trapping efficiency, and success of a binational sea lamprey control program in the Laurentian Great Lakes, North America. Our experiment compared nightly catches of sea lamprey marked with external fin clips, surgically-implanted passive integrated transponder tags (PIT-only), and surgically-implanted PIT and acoustic tags (PIT+acoustic). We found no evidence that the probability of being trapped was affected by the added invasiveness and handling of internal tagging. Nightly recaptures of PIT-only tagged sea lamprey, relative to fin-clipped sea lamprey, were not different from expectations based on the numbers of individuals released from each treatment group. Conversely, there was evidence of effects related to tag size. Nightly recaptures of PIT+acoustic tagged sea lamprey, relative to PIT-only tagged sea lamprey, were lower than expected based on numbers of individuals released from each treatment group. Effects related to tag size partially explain the disparate estimates in trapping efficiency observed for sea lamprey.     

Factors affecting recruitment dynamics of Great Lakes sea lamprey (Petromyzon marinus) populations

Knowledge of stock–recruitment dynamics is as important for control of pest species such as the sea lamprey (Petromyzon marinus) as it is for sustainable harvest management of exploited fish species. A better understanding of spatial and temporal variation in recruitment of pest populations may inform managers on where and when to effectively apply different control methods. Sea lamprey stock–recruitment data combined from streams across the Great Lakes basin into a Ricker stock–recruitment model indicated both compensation (density-dependent survival) and a large amount of density-independent recruitment variation. We evaluated the use of a mixed-effects model to look at common year effects and stream-level variables that could affect productivity and growing season length, with the objective of identifying factors that may explain this density-independent variation in recruitment. After selecting the “best model”, we tested factors that might affect recruitment variation, using a Great Lakes dataset comprising 97 stream–years. Lake Superior tributaries, streams with larger numbers of lamprey competitors, and streams regularly requiring lampricide treatment showed significantly higher recruitment. Alkalinity and thermal regulation did not affect the observed recruitment pattern among streams. In four long-term study streams we observed significant variation among streams, tested as a fixed effect, but no evidence suggested a common pattern of variation among years. Differences in recruitment among streams were consistent with evidence of quality of spawning and larval habitat among streams. Our findings suggest that management models should account for differences in recruitment dynamics among sea lamprey-producing streams, but not common year effects.     

Use of an artificial stream to monitor avoidance behavior of larval sea lamprey in response to TFM and niclosamide

The lampricide 3-trifluoromethyl-4-nitrophenol (TFM) has been used in liquid form to control larval sea lamprey (Petromyzon marinus) in Great Lakes tributaries since the late 1950s. In the 1980s a dissolvable TFM bar was developed as a supplemental tool for application to small tributaries as a deterrent to larvae seeking water not activated with TFM. The size, mass, and number of bars needed in some streams, as well as the location of the streams, limit the utility of a TFM bar. The development and use of an alternative niclosamide bar has the potential to use fewer bars to achieve similar results. However, the use of a niclosamide bar is dependent upon its larval deterrent capability compared to the TFM bar. In this study, we developed a laboratory-scale, simulated stream fluvarium with several avoidance areas including two side channels and a seep. The objective was to evaluate the deterrent capabilities of TFM and niclosamide. We found similar behavioral responses, with TFM and niclosamide having similar capabilities to prevent sea lamprey from seeking refuge in side channels and seep avoidance areas. TFM-treated side channels and seep increased sea lamprey occupancy in the main channel 2.56 times more than the untreated-controls (95% CI 1.63–4.14) whereas niclosamide-treated side channels and seep increased sea lamprey occupancy of the main channel 2.68 times more than the untreated-controls (95% CI 1.72–4.32). These responses indicate a niclosamide bar would effectively prevent sea lamprey escapement into freshwater during a lampricide treatment at concentrations unlikely to harm aquatic organisms.     

筏式养殖区垂向流速分布特征试验研究

贝类筏式养殖在海水养殖中占据重要地位。近年来,随着养殖规模逐渐扩大,筏式养殖的弊端也随之显现出来。大面积筏式养殖网笼的布置,对海洋潮流流速产生阻碍作用,引起水体交换能力下降、污染物堆积等问题。因此研究筏式养殖垂向流速区分布特征,可为养殖规模控制、污染防治等提供科学参考。该文首先收集了筏式养殖及流速变化的相关资料,整理了筏式养殖区区域特征及养殖概况,根据养殖区实际情况,取长度比尺1??20,制作了筏式养殖的物理模型。然后在波流水槽中进行11组试验,探究了养殖区内外流速在不同水深、来流速度、养殖密度条件下的变化情况。结果表明:(1)筏式养殖模型的存在,会对来流造成明显的阻碍作用,表层流速减小较多。(2)养殖区内部断面平均流速相比于来流减小约15%。(3)养殖区前方流速变化较小,养殖区后方流速变化较大。(4)养殖水深越浅,来流速度越小,养殖密度越大,养殖区对来流的影响程度越大。     

沿海挡潮闸下港道监测方法的改进

感潮河口建闸后,河口区的潮波运动形态发生改变,径流与潮流间的能量平衡重新调整,引起闸下港道淤积,导致泄洪不畅,加剧洪涝灾害损失。为最大限度地减轻闸下港道淤积带来的危害,在进行工程整治的同时,必须弄清闸下港道泥沙运动规律,找到一条科学、合理、有效的治理方法和途径。以江苏省里下河地区的射阳河、新洋港、黄沙港、斗龙港为范例,提出挡潮闸下港道监测方法的改进。     

低浓度固液两相流中泥沙垂直分布的摄动理论解释

本文从低浓度两相流中固相和液相的相互作用着眼，从基本的动量方程和连续方程出发，将悬浮固体颗粒的存在视为对相同流动条件下清水紊流的摄动，引入摄动分析的理论，并通过动量方程直接得出了悬移质泥沙浓度分布规律，从而对作者和王光谦提出的悬移质泥沙分布的统一公式给出了理论解释     

对悬移质含沙分布Rouse公式沿垂线积分的研究

文中着重研究了悬移质泥沙分布Ｒｏｕｓｅ公式沿垂线的积分问题，给出了悬移质垂线平均含沙量与底部含沙量的比值函数，并给出了此函数的计算方法。     

Estimating wounding of lake trout by sea lamprey in the upper Great Lakes: Allowing for changing size-specific patterns

A primary fishery concern in the Laurentian Great Lakes is mitigating the persistent negative impact of parasitic sea lamprey (Petromyzon marinus) on native lake trout (Salvelinus namaycush). Wounds observed on surviving lake trout are commonly used by managers to assess damages associated with sea lamprey predation. We estimated the relationship between wounding rates and lake trout size, and how this varied spatially and temporally. We built upon previously published work by fitting wound rates as a logistic function of lake trout size. By using longer time series and data from three Great Lakes, our analysis harnessed substantially more contrast in host populations than previous work, and we also employed software advances for nonlinear mixed-effect models. Candidate models allowed logistic function parameters to be constant or to vary spatially, temporally, or both. Temporal effects were modeled as random walk processes. We also considered models that assumed either Poisson or negative binomial distributions for the number of wounds per fish at a given length. Models that allowed for both spatial and temporal effects in the shaping parameters and assumed a negative binomial wound distribution resulted in the best fit as indicated by Akaike's Information Criterion. Wounding rate estimates from models selected for each lake in this analysis are contrasted with those of wounding rate models currently used as components of lake trout population assessments. Although model fit was improved substantially, differences in wounding rates estimates are modest and estimates follow very similar temporal trends. However, as time series of wound data continue to grow, models that incorporate temporal variability in parameter estimation are expected to be increasingly favored. This research provides managers with an updated tool to obtain more reliable estimates of sea lamprey wounding.     

Variation in larval sea lamprey demographics among Great Lakes tributaries: A mixed-effects model analysis of historical survey data

Understanding variation in fish populations is valuable from both a management and an ecological perspective. Great Lakes sea lampreys are controlled primarily by treating tributaries with lampricides that target the larval stage. Great Lakes streams were divided into four categories based on their regularity of parasitic lamprey production inferred from the historic regularity of chemical treatments. This categorization was intended to direct future assessment efforts, but may also reflect differences in early demographics. We analyzed assessment data collected from 1959 to 2005 using mixed-effects models and variance components analyses to test for differences in recruitment and growth to age 1 among stream categories. Recruitment was twice as large in regularly treated streams as in irregularly treated streams, indicating that age-1 year-class strength is correlated with consistent chemical treatments. We found no differences in length at age 1 among stream categories; however, Lake Superior streams with irregular treatment histories exhibit more variation in length at age 1 than streams that are treated regularly. The majority of variation in length at age 1 was due to within-year variation, which was fairly consistent across stream types within each lake. Our results indicate that early life history differs among subsets of the Great Lakes sea lamprey population, and management practices should be modified to account for these differences. Mixed-effects models and variance components analyses are useful tools for analyzing large historical datasets for patterns of demographic variation within and among populations, whether the ultimate goal is pest control, harvesting, or conservation.     

海水直流冷却系统中立式混流泵选型和防腐问题研究

立式混流泵作为海水直流冷却系统的核心设备,选型应兼顾可靠性、经济性和维修便利性.以某滨海石化厂的海水立式混流泵为实例,探讨了立式混流泵选型时需考虑的问题,并重点介绍了立式混流泵在海水介质中的防腐蚀措施.     

江苏辐射沙洲陈家坞槽悬沙变化过程及垂线分布资料分析

本文对辐射沙洲陈家坞槽14号站位连续2个潮次的水文、泥沙测量资料进行了分析研究,论述了在非恒定流作用下泥沙的悬浮与沉降过程。定量分析了重力作用与紊动作用对含沙量和床面变形率的影响关系。对水体悬沙的垂线分布进行了拟合,给出了对数拟合关系式,并对该关系式进行了讨论和验证,初步明确了陈家坞槽主槽的悬沙垂线分布基本特征。     

Discriminating natal origin of spawning adult sea lamprey (Petromyzon marinus) in Lake Champlain using statolith elemental signatures

Sea lamprey (Petromyzon marinus) is a nuisance species in the Great Lakes and Lake Champlain. Information about tributary contributions to the spawning adult phase is critical for appropriate allocation of efforts to control this species. We examined the accuracy of statolith elemental composition to identify the natal origin (i.e., individual rivers or clusters of rivers) of 33 known-origin adults from the Lake Champlain basin. To do so, we first established natal origin chemical signatures using the statoliths of 238 larvae from the same basin. Using laser-ablation inductively coupled plasma mass spectrometry, the 238 larvae originating from 12 streams and one delta were discriminated with a classification accuracy of 57% (range: 25–80%) and 70% (range: 29–80%) when individual streams and groups of streams were considered respectively, highlighting the potential of statolith microchemistry to identify natal origins. However, the assignment of natal origin for adults was overwhelmingly incorrect. Using a maximum likelihood procedure, 88% of the adults were assigned to a cluster of three streams and one delta, while only 3% of these individuals were known to originate from this particular cluster. More research is required to understand the low classification accuracy of sea lamprey adults and validate the use of statolith microchemistry to identify sea lamprey natal origin.     

沉井下沉过程中底部垂线流速分布试验研究

本研究借助河工模型试验手段,通过对沉井在不同的入水深度时沉井底郝垂线流速分布情况的观潮,探讨了沉井下沉过程的局部冲刷发展的原因,本研究对制定沉井施工工序和掌握恰当时机进行沉井具有指导意义.