Comparison of Otolith and Scale Ages for Yellow Perch from Lake Michigan

The age composition of the yellow perch (Perca flavescens) population in Lake Michigan is assessed annually by five management agencies, but all agencies do not use the same structure to estimate ages. The reliability of the most commonly used structure, scales, has not been formally evaluated for this population. We compared ages estimated by three readers from scales and sagittal otoliths for 150 yellow perch from southwestern Lake Michigan. The maximum age of yellow perch determined from scales and otoliths was 12. Otoliths had better precision (reproducibility) and usually had more annuli than scales for all three readers. Scale ages were usually younger than otolith ages when otolith ages were ≥ 7. Chi-square tests revealed significant differences (P < 0.05) between the age distributions determined from scales and otoliths for two of the three readers. We recommend use of otoliths for aging Lake Michigan yellow perch greater than 150 mm in length because of greater precision, easier readability, and detection of more annuli.     

Fish Community Dynamics in Northeastern Lake Ontario with Emphasis on the Growth and Reproductive Success of Yellow Perch (Perca flavescens) and White Perch (Morone americana), 1978 to 1997

Fishes were assessed in Guffin, Chaumount, and Black River bays in northeastern Lake Ontario with a 7.9-m (headrope) bottom trawl during late September and early October, 1978 to 1997. Fish density declined in the early 1990s with sharp declines in abundance of spottail shiner (Notropis hudsonius), trout-perch (Percopsis omiscomaycus), and johnny darter (Etheostoma nigrum) occurring in 1993 to 1995. Rising numbers of piscivores, walleye (Stizostedion vitreum) and double-crested cormorant (Phalacrocorax auritus), increased predation pressure, presumably acting in concert with oligotrophication to lower fish density, particularly after 1991 when large numbers of adult alewife (Alosa pseudoharengus) no longer migrated to the northeast basin in spring. Annual mortality of yellow perch (Perca flavescens) from age 2 to 5 rose from 33% in 1980–83 to 65% in 1992–95 and was positively related to piscivore numbers (P = 0.01, r = 0.96, n = 5). Annual mortality of yellow perch from age 0 to 2 also peaked in 1992–95. Abundance of yellow perch YOY in fall varied 40 fold and was not related to water warming in spring (P = 0.45, r = −0.19, n = 18) but was negatively related to the abundance of adult alewives in spring (P = 0.04, r = −0.49, n = 18). Although yellow perch produced moderate to strong year classes each year during 1991–95, stock size failed to increase because of rapidly accelerating mortality. Fully 85% of the variation in mean length of yellow perch YOY was explained by a multiple regression model which included YOY abundance, mean total phosphorus, and cumulative degree days > 13.5°C (P < 0.01, n = 15). Abundance of white perch (Morone americana) YOY varied nearly 200 fold and was not related to water warming or spring alewife abundance (P > 0.15). Variation in mean length of white perch YOY was related to cumulative degree days > 15°C (P < 0.01, r = 0.69).     

Examination of Sampling Bias for Larval Yellow Perch in Southern Lake Michigan

Evidence suggests larval yellow perch, Perca flavescens, utilize nearshore and offshore habitat during the 30–40 day period between hatch and transition from pelagic to demersal habitat. In a large, open system like Lake Michigan this represents a significant increase in available habitat and it is important to understand how this increase may impact our ability to sample larval yellow perch in an unbiased manner. We measured the vertical distribution of larval yellow perch in southern Lake Michigan as a function of size, age, and diel period. Larval yellow perch were collected from two zones (surface and epilimnion) from 1 to 32 km from shore in 2001 during the day; on four dates surface samples were also collected at night. Results indicate larval perch are more abundant at the surface at night han during the day. Larval yellow perch < 15 mm total length (TL) and younger than 18 days post hatch were found in both surface and epilimnion habitat during the day, but larvae > 15 mm TL were captured only in the epilimnion and farther than 5 km from shore, which suggests a different spatial distribution for larger, older larvae. Diel differences in larval abundance and size at the surface suggest more and larger larvae will be caught for a similar effort at night as compared to daytime sampling. Observed differences in larval distribution with size and age also suggest that sampling concentrated nearshore and/or at the surface has the potential to under-sample larger/older yellow perch larvae in Lake Michigan.     

Reconstructing Habitat Use and Wetland Nursery Origin of Yellow Perch from Lake Superior using Otolith Elemental Analysis

The use of otolith elemental composition as a natural tag has emerged as a powerful tool for managing and understanding the ecology of marine fish populations. The approach remains relatively untested in fresh waters, so we examined its utility for reconstructing habitat use and wetland nursery origin in Lake Superior. We analyzed the otolith margin of adult yellow perch, Perca flavescens, as an indicator of recently occupied habitat, and the juvenile region of the otolith core as an indicator of nursery area. To characterize elemental fingerprints, all otolith samples were analyzed for Ca and 13 minor and trace elements using mass spectrometry. We found differences in the otolith concentrations of several elements between yellow perch inhabiting coastal wetlands and those inhabiting the adjacent nearshore waters of Chequamegon Bay. The most striking difference was the high concentration of Sr in the sagittal margins of wetland-caught fish relative to those captured in the bay. Based on differences in otolith Sr concentrations alone, fish from bay and wetland habitats could be distinguished with 100% accuracy. We also found that elemental fingerprints derived from otolith cores of adult yellow perch were similar among fish captured from wetlands adjacent to Chequamegon Bay but quite distinct for one site outside of the bay, suggesting these fish came from a separate population from those in Chequamegon Bay. Overall, these results encourage us that elemental fingerprinting techniques will be useful for estimating the relative importance of different coastal wetland habitats to wetland-dependent species in the Great Lakes.     

Biophysical Model of Larval Yellow Perch Advection and Settlement in Lake Michigan

Potential for large-scale physical transport processes to affect recruitment of Lake Michigan yellow perch (Perca flavescens) was studied by examining the variation in larval distribution, growth rate, and settlement during June–August 1998–2003 using a 3D particle transport model linked with an individual-based bioenergetics growth model. In all years, virtual larvae were released nearshore in southwestern Lake Michigan, a known and important spawning region for yellow perch. For any given year, the same circulation pattern and water temperature either promoted or reduced yellow perch settlement depending on the consumption rates and settlement size chosen in the growth model. Increased consumption increased the number of settled larvae and expanded the total area where larvae settled, whereas increased settlement size reduced the number of settled larvae and reduced the overall settlement area. Interannual variability in circulation patterns and water temperature also resulted in contrasting larval settlement rates, settlement locations, and size of settlement areas between years. Model predictions were most consistent with field observations of age-0 yellow perch from Illinois and Michigan waters when settlement was assumed to occur at 50 mm. Moreover, our model suggests that larvae originating from southwestern Lake Michigan can recruit anywhere within the southern basin and even in the northern basin. Future model improvement will require information on the relative contribution of various sectors to the larval pool, their distribution with reference to the hydrodynamic landscape, the feeding and growth of yellow perch during their pelagic phase, and the size at transition to demersal stage.     

Differential habitat use patterns of yellow perch Perca flavescens in eastern Lake Michigan and connected drowned river mouth lakes

Understanding stock structure and habitat use is important for sustainable fisheries management and conservation of genetic and phenotypic diversity. In eastern Lake Michigan, yellow perch Perca flavescens is found in both the nearshore region of Lake Michigan proper and drowned river mouth (DRM) lakes, small estuary-like systems directly connected to Lake Michigan. Recent genetic analyses suggest complex stock structure between these habitats and the potential migration of Lake Michigan yellow perch into the profundal zone of DRM lakes. We quantified carbon (δ¹³C) and oxygen (δ¹⁸O) stable isotope ratios of yellow perch otolith cores to index natal origins, and measured muscle δ¹³C, nitrogen (δ¹⁵N), δ¹⁸O, and hydrogen (δ²H) isotope ratios to reflect recent diet and habitat use. Stable isotope ratios of otolith cores and muscle samples support the existence of resident populations in nearshore Lake Michigan and DRM lakes, as well as Lake Michigan migrants using DRM lakes. Most fish caught in DRM lakes that had natal and recent stable isotope values similar to Lake Michigan fish were collected during fall in DRM lake profundal zones. Comparison of otolith core and muscle stable isotope ratios of individual yellow perch suggest that individuals that recently migrated to DRM lakes also spent early life in Lake Michigan. Differential habitat use patterns of yellow perch in eastern Lake Michigan may have important implications for harvest estimates and fishing regulations. Migration by Lake Michigan fish into DRM lakes does not appear to be related to reproduction, and the underlying benefits of these migrations remain unclear.     

Characterization of Growth and Winter Survival of Age-0 Yellow Perch in Southeastern Lake Michigan

Reduced growth and increased winter mortality are possible mechanisms for poor recruitment of age-0 yellow perch (Perca flavescens) in southeastern Lake Michigan. To assess the role of growth variability on recruitment of age-0 yellow perch, we quantified length-by-date and abundance during 1996–2002. Analyses revealed significant differences in length among years and sites. To resolve spatial trends, we contrasted the 1998 cohort from southeastern Lake Michigan with conspecifics from populations located within and beyond the Lake Michigan watershed. These analyses identified significant differences in length; trends suggested that the capacity for growth in the cohort from southeastern Lake Michigan was similar to these other populations. To characterize winter survival for the 1998 age-0 cohort, otoliths from age-1 perch in 1999 were used to back-calculate length (BCL) from the previous autumn. The BCL distribution was significantly larger than the 1998 distribution, but analyses led to the inference that this age-0 cohort experienced little mortality during the winter of 1998–99. We used a regression model to quantify risk of winter starvation for the 1998 cohort, using 1981–2001 winter water temperatures from southeastern Lake Michigan. This analysis suggested that risk of starvation for the 1998 cohort across this period was low (1.0–4.4%). Back calculation and regression analyses allow us to reject the hypothesis that reduced growth led to a high rate of winter mortality for the 1998 cohort. If we extrapolate our findings to past cohorts, the results would be similar unless these fish were significantly smaller than the 1998 cohort. Variation in age-0 length, growth, or winter mortality failed to fully explain yellow perch recruitment patterns in southeastern Lake Michigan. We hypothesize that factors acting before the juvenile stage is sampled during summer are shaping recruitment; resolving this requires further, stage-specific studies.     

Distribution of Larval Yellow Perch (Perca Flavescens) in Nearshore Waters of Southeastern Lake Michigan

Spatial and temporal distribution of larval yellow perch (Perca flavescens) in southeastern Lake Michigan was described from samples collected during 1973–1981 with plankton nets and benthic sleds in water 0.5 to 21 m deep. Yellow perch larvae ≤ 7.5 mm total length were numerous from mid-May to early or mid-July. Larvae taken before mid-June hatched from eggs spawned in inland waters, rather than in Lake Michigan. Those larvae appearing early occurred chiefly in shallow water (≤1.5 m), whereas larvae caught later were chiefly distributed in deeper water (≥ 6 m). Larval perch abundance was similar at all bottom depths ≥ 6 m, was low in surface water during the day, and low near bottom at night. At 0.5- and 1.5-m stations, significantly more larvae were caught at night than during the day.     

Response of Yellow Perch Diet to a Changing Forage Base in Southern Lake Michigan, 1984-2002

This study evaluated yellow perch (Perca flavescens) diet in southern Lake Michigan to determine whether prey consumed fluctuated with abundance of zooplankton, benthic invertebrates, and fish species during the period 1984 to 2002. Some change in benthic community abundance was evident from samples collected in the region during the period, including the naturalization of the round goby and the zebra mussel between 1993 and 2002. In addition, changes in fish abundance were evident from 1984 to 2002, when spottail shiner (Notropis hudsonius) and alewife (Alosa pseudoharengus) increased, while yellow perch, and rainbow smelt (Osmerus mordax) declined. Non-indigenous species eaten by yellow perch in 2002 included spiny water fleas (Bythotrephes longimanus), round gobies, and alewives with the latter two species dominating the diet by volume. Yellow perch did exhibit prey preferences, although they consumed a variety of different organisms over the period of study. This euryphagous characteristic of yellow perch is expected to promote its persistence in southern Lake Michigan, despite a changing prey base.     

Changes in Abundance and Growth Characteristics of White Perch from the Mouth of the Bay of Quinte

White perch became established in Lake Ontario in the 1950s, and by the mid 1960s were a major commercial species in the Bay of Quinte area. Commercial catches have fluctuated markedly, ranging from approximately 60,000 to 230,000 kg/yr between 1964 and 1978. Experimental trap nets set inshore of the mouth of the Bay of Quinte during May to July suggest a decline in white perch abundance from 1973 through 1978. However, the commercial catch did not similarly decline until 1979 when the commercial catch fell to a low of 30,000 kg/yr. The reason for this difference may be due to the fact that the bulk of the commercial catch is harvested during the winter when white perch congregate at the mouth of the bay, making fishing relatively productive. The growth of white perch was also considered, based on back-calculated growth curves of white perch caught in the experimental nets. Lee's phenomenon—a tendency for back-calculated lengths at a given age to become progressively smaller as the age of the fish from which they were computed increases—was apparent among the fish caught during this study although lacking in an earlier study. Due to the size selective nature of the fishery, an increased commercial harvest in recent years may have removed a disproportionate number of faster growing individuals from the population.     

引黄水库水超滤膜处理集成技术研究与综合示范

针对引黄水库水低温低浊、高藻、微污染的水质特点,通过关键技术研究、技术集成及示范应用,研究开发了以超滤膜为核心的深度处理组合工艺,积累了超滤膜净水厂设计、建设、运行和管理等的大量实践经验。在东营建立了国内首座10万m3/d规模的饮用水膜处理示范水厂,出水水质满足现行生活饮用水卫生标准,同时为今后超滤技术在城镇净水厂建设以及老水厂改造中的推广应用提供重要技术支撑。     

对引黄水、地下水优化调控模型的研究

商丘试验区基本无地面水可用,工农业用水主要依赖降水和浅层地下水,需水量与供水量之间存在着矛盾,为此提出了引黄水、地下水联合调控问题。本文运用非线性规划法,结合当地实际,对模型进行求解,以实现各种水源的优化配置。     

激光粒度分析仪测试黄河泥沙粒度的精度试验

根据激光法测试泥沙粒度的目标函数、误差环节和统计误差作为精度指标的要求,提出了误差评估路线,设计了仪器测试重复性试验、试样加样平行性试验、人员操作平行性试验等精度试验方案。通过试验,总结出了激光粒度分析仪测试黄河泥沙粒度时各误差环节的误差限定指标。     

Examination of Factors Contributing to the Decline of the Yellow Perch Population and Fishery in Les Cheneaux Islands,Lake Huron,with Emphasis on the Role of Double-crested Cormorants

Double-crested cormorants increased exponentially in the Les Cheneaux Islands area during the 1980s and 1990s. The yellow perch fishery and population declined by the late 1990s and finally collapsed in 2000. Previous research confirmed that cormorants fed seasonally on perch. This analysis sought to use creel survey data and data from an annual gillnet collection to characterize the perch fishery and population during this time so as to explore if declines were a result of declining recruitment or increased mortality or both. Regression analysis explored six possible independent variables to account for yellow perch trends. Yellow perch abundance and its fishery declined throughout the Les Cheneaux Islands. Mean age declined which was consistent with a high mortality rate explanation. Yellow perch recruitment, as indicated by gillnet catch rate of age-2 perch, continued during this time including one very strong year class. Total annual mortality rates determined by the cohort method were as high as 85% during much of this time and increased over the time series. Cormorant abundance accounted for a total of five significant relationships with the yellow perch data, more than any other independent variable. From this, it is apparent that cormorant predation is at least one factor affecting the perch population and fishery and may be the most influential force, among those examined, during this time series.     

Component-based Reconstruction Prediction of Runoff at Multi-time Scales in the Source Area of the Yellow River Based on the ARMA Model

Water Resources Management - Improving the accuracy of hydrological prediction for long-term annual runoff series is important for water resources management and planning. In this study, the...     

引黄济津(潘庄线路)关键调度技术探析

为确保引黄济津(潘庄线路)持续成功实施,德州市以线路优化、输水技术、管理方式为中心,进行关键调度技术研究。通过模拟试验、输水演习、数据推算、冰期研究、总结归纳等方式方法,提炼了引黄济津(潘庄线路)不同渠段、不同时段、不同阶段、不同地段的输水运行和险情应对关键调度技术,为类似跨流域输水调度提供借鉴和参考。     

Distribution and Abundance of Rainbow Smelt in Western Lake Superior as Determined from Acoustic Sampling

Distribution and abundance of rainbow smelt (Osmerus mordax, Mitchill) in the western arm of Lake Superior were described through an acoustic sampling program conducted from June 1978 through early June 1980. Density and abundance were highest in shallow water (bottom depth <50 m), where rainbow smelt underwent vertical movements from the bottom and concentrated in warmer (11 to 16° C) near-surface water (2- to 30-m depth) at night. Rainbow smelt densities and abundance were extremely low in the deeper waters (>50 m) along the north shore and in the open lake. Abundance of rainbow smelt in the western area of the lake was estimated to be 286 X 10⁶ fish (4.35 X 10⁶ kg) in 1978. Abundance declined to 164 X 10⁶ fish (2.5 X 10⁶ kg) in 1979. Comparison of rainbow smelt abundance estimates with commercial yields suggested that annual fishing mortality is 15 to 27%. Predation by salmonid populations is considered a potentially important factor influencing smelt abundance levels. Rainbow smelt distribution and changes in abundance described by this study indicate smelt production is not high enough to support the fisheries or predator populations previously supported by native lake herring (Coregonus artedii, Lesueur) stocks.     

引黄灌区泥沙农田化技术

黄河下游引黄灌区在引水的同时，也引进了大量泥沙，堆积在渠道和沉沙池两旁，不仅恶化了环境、形成沙害，而且也占压了大量耕地。三义寨灌区是较典型的引黄灌区，以沉沙条渠泥沙农田化和渠道两侧沙垄治理为重点，进行了堆沙高地作物品种、土壤改良、小麦灌溉、果农间作种植模式等试验研究，提出了一套较系统的泥沙农田化技术，为引黄灌区泥沙的处理和利用探索出了一条新途径。     

Assessment of Stochastic Operation Optimization for Reservoirs of Contrasting Scales

Deriving optimal release policies for dams and corresponding reservoirs is crucial for the sustainable water resources management of a region as they directly control the distribution of water to several users. Mathematical optimization algorithms can help in finding efficient reservoir operating strategies taking into account complex system constraints and hydrologic uncertainty. The robustness of operation optimization models may be influenced by physical reservoir characteristics such as size and scale and the effectiveness of a model for a particular case study does not always guarantee the same level of success for another application. This research focused on assessing the applicability of an implicit stochastic optimization (ISO) procedure to derive rule curves for two different dams of contrasting reservoir scales in terms of physical and operational characteristics. The results demonstrated the feasibility of the proposed technique for both small- and large-scale systems in view of the lower vulnerability provided by the ISO-derived policies in contrast to operations carried out by the standard reservoir operating policy as well as the proximity of the ISO operations with those by perfect-forecast deterministic optimization. The ISO procedure also provided operating rules similar to, and even less vulnerable than, those derived by stochastic dynamic programming.     

黄河泥沙分选装置设计与试验研究

在分析黄河泥沙分选现状的基础上,介绍了利用磁铁和离心力原理研制的黄河泥沙分选装置的工作原理及其工作参数,并进行了典型铁沙和粗、中、细泥沙的室内分选试验。结果表明:该装置揭示了不同粒径泥沙在分选筒内旋转水体作用下的沉降分布规律,其具有结构简单、操作维修方便、结实耐用、节能高效、成本低廉、可连续作业等特点。