The variation in suspended sediment and water properties in the flood-water front traversing the tidal flat

The initial flooding waters from twenty-four consecutive tides were examined for changes in water properties as the flood-front traversed the intertidal zone. The flood-front water temperature depended on the time of flooding as well as the sun’s insolation. On warm sunny days, the water temperature at the leading edge of the tide successively increased as the water flooded the tidal flat. In contrast, during cloudy days, and early morning and evening samplings, the flood-front water decreased during flooding. Flood-front water temperatures on warm days exceeded 34°C, some 15°C higher than the water observed in the deeper tidal channels. Flood-front salinities increased progressively across the intertidal zone regardless of local weather conditions, and were primarily controlled by mixing of surface waters with interstitial waters during the flooding process. Particulate matter concentrations were dependent on the interaction between small amplitude waves and varying intertidal bottom slope. Extreme variability in the particulate matter concentration across the tidal flat was in part caused by alternate resuspension and settling of fecal pellets composed of silty-clay aggregates which partly form the bottom sediment of the test area. The texture of the suspended particulate matter coarsens near shore, where wave resuspension became more effective on a steeper portion of the intertidal zone. *** DIRECT SUPPORT *** A01BY009 00003     

Light scattering and extinction in a highly turbid coastal inlet

Multifactor regression analysis was used to test for relationships between chemical, physical and optical properties of the water column in the organically rich, highly turbid waters of Florida's Fort Pierce Inlet. Optical measurements were made at three visible light wavelengths (445 nm, 542 nm and 630 nm). Scattering by suspended particulate material was found to be the primary optical mechanism controlling downwelling irradiance at all three wavelengths. Larger particles showed constant scattering efficiencies of 2 when their diameters exceeded 3 to 5 microns, depending upon the wavelength used for observation. Selective absorption had a definite effect on the transmission of radiant energy in the 445 nm wavelength range. High correlation between extinction at 445 nm and the cross-sectional area of the suspended particulate material indicates particulate, rather than dissolved materials, are the major water column constituents that selectively absorb short wavelength radiant energy in this inlet. Spectral distribution of the downwelling radiant energy field was found to shift dramatically over a period of several months. These shifts in downwelling spectral irradiance were attributed to seasonal and/or event related shifts in concentrations of selectively absorbing compounds within the water column.     

藏东南地区复杂下垫面辐射收支特征分析

利用藏东南地区进行的地气交换观测数据, 分析了典型晴天和阴天不同下垫面辐射过程的特征及其差异. 结果表明: 藏东南地区典型晴天不同下垫面总辐射均呈现出明显的日变化规律, 典型阴天各下垫面总辐射日峰值与典型晴空天气下的总辐射日峰值差值不大, 日均值显著减小; 反射辐射日变化趋势与总辐射变化一致, 但变化曲线比总辐射离散, 阴天地表反射辐射受总辐射和下垫面的综合影响; 向上长波辐射日变化幅度和量值都大于向下长波辐射, 下垫面类型对向下长波辐射没有影响. 净辐射具有明显的日变化特征, 和总辐射的相位一致, 农田净辐射的日峰值和日均值最大.     

Two-dimensional modelling of hydrodynamics and water quality of a stratified dam reservoir in the southern side of the Mediterranean Sea

A vertical two-dimensional, laterally averaged hydrodynamic and water quality model CE-QUAL-W2 was used to simulate water temperature, dissolved oxygen, electrical conductivity, chlorophyll a, total suspended solids, alkalinity, ammonium, phosphate, and total iron in the Sejnane Dam (North Tunisia) in response to external forcings that characterize main features of climate in the southern side of the Mediterranean Sea. The hydrodynamic modelling results show that the model is able to reproduce accurately the measured water surface elevation, spatio-temporal patterns of temperature, dissolved oxygen and other state of variables and to capture most of the seasonal changes in the reservoir. Three scenarios involving the impacts of severe drought season, summer rainfall and total suspended solids load on hydrodynamics and water quality are analyzed. Severe drought reduces the thickness of hypoxic waters from 10 to 2–4 m and shifts the temperature of the entire water column up to 5 °C during summer and about 1.2 °C in winter. The thermocline takes place 1 month before that of the reference and sinks to the bottom faster by 1–2 m per month. Summer rainfall dilutes the first waves of the autumn rains and disrupts the thermal gradient in the water column, which may show complex thermal structures. TSS load has the most negative effects on water quality in that it shifts the phosphorus concentration by 1–3 mg/l and promotes an early warming of surface water in spring and an early cooling since late summer by up to 1 °C. During summer stratification, it contributes to the cooling of the metalimnion by 2 °C on average, which may alter its structure and dynamics as an aquatic biotope.     

Time series analyses of suspended sediment concentrations at North Inlet,South Carolina

Daily water samples have been collected at three stations in the North Inlet (South Carolina) marshestuary system since February 1981 as part of the NSF Long-Term Ecological Research (LTER) project. As a result of this sampling regime, nearly continuous time series of inorganic and organic suspended sediment, particulate organic carbon (POC), Secchi disk, salinity, and water temperature are now available. Power spectrum analysis of these data reveals that most of the explainable variance in the inorganic suspended sediment, POC, and Secchi disk data is related to a yearly cycle that is strongly coherent with water temperature such that high turbidity is associated with high water temperature. Only a small fraction of the explainable variance is associated with frequencies that can be related to the semidiurnal tide. Simple correlation analysis also indicates that turbidity is more closely associated with water temperature than with tide height or salinity. The ratio of POC to inorganic suspended sediment shows no discernible power spectra peaks and is weakly, but inversely, correlated with temperature. From these results we hypothesize that temperature-regulated bioturbation is the main factor controlling turbidity variations in the system. The lack of a strong inverse correlation between turbidity and salinity suggests that river runoff has little immediate impact on the suspended sediment of nearshore coastal waters in systems similar to North Inlet.     

Diel oxygen dynamics and anoxic events in an eutrophic estuary of Waquoit Bay,Massachusetts

As a result of nutrient loading from septic systems, a thick canopy of macroalgae covers the bottom of Waquoit Bay, an embayment on Cape Cod, Massachusetts. Using automated conductivity-temperature-oxygen recorders and manual profiles, we measured diel water column O₂ changes during summer in the Childs River, the estuary of the bay with the highest housing density. At dawn in midsummer, bottom waters in the Childs River are chronically hypoxic due to high rates of benthic respiration. On sunny days benthic photosynthesis drives bottom water O₂ to 10–15 mg l^?1 by afternoon. The extent of the daily O₂ excursion is directly proportional to daily irradiance. Large diel O₂ excursions in bottom water are due to limited mixing of surface and bottom water. Density stratification exceeded two sigma-t units 85% of the time during midsummer in the Childs River. Because of stratification, hypoxia and even anoxia occur in this estuary. The first of several anoxic events was observed in Waquoit Bay in 1988, and we have attempted to evaluate factors that trigger anoxia. High rates of benthic respiration result in anoxia when replenishment of O₂ during the day is limited by insufficient light. Our analysis of meteorological records during two recent anoxic events shows that anoxia develops overnight in midsummer during periods of peak summertime temperatures after several days of cloudy, moderately calm weather. Similarly critical conditions existed most summers since 1975, yet anoxic events in the bay have not been reported historically. If climatic warming occurs, anoxic events in the bay may occur more frequently even if algal stocks remain unchanged. Eutrophication of Waquoit Bay is similar to many other embayments in populated coastal areas, and anoxic events may indicate a chronic growing problem in these important ecosystems. However, in shallow, stratified embayments, anoxia may be transient and easily missed without frequent monitoring.     

The role of stratification in the deoxygenation of Mobile Bay and adjacent shelf bottom waters

Oxygen depletion in the shallow bottom waters of Mobile Bay, Alabama, and in adjacent nearshore and continental shelf waters, is shown to be directly related to the intensity of water column stratification. Low winds speeds are coincidental with the onset of water column stratification and the occurrence of hypoxic events. Hourly, daily, and seasonal changes in the relationship between percent oxygen saturation or oxygen concentration in the bottom waters and surface-bottom density differences indicate that the oxidized materials are recently formed, and not relic or overwintering carbon sources. The influence of density structure (water column stratification) in other oxygen-depleted coastal water masses is compared to Mobile Bay.     

The Optical Properties of Greater Florida Bay: Implications for Seagrass Abundance

Water column optical properties of Greater Florida Bay were investigated in the context of their impacts on seagrass distribution. Scattering played an important role in light attenuation throughout the shallow water system. The northwest region was characterized by an absence of seagrasses and the highest scattering by particles, mostly from resuspended carbonate sediments. Higher seagrass densities were observed in the open waters just north of the Florida Keys, where absorption coefficients were dominated by colored dissolved organic material and scattering was lower than in the northwest region. Patchy dense seagrass meadows were observed in the clear waters south of the Keys where scattering and absorption were low and contributed equally to light attenuation. In general, seagrasses were observed in areas where >7.5% of surface irradiance reached the plants and where optical properties were not dominated by scattering. Although the prevention of eutrophication and nuisance algal blooms may be necessary for preserving seagrass meadows in this system, our observations and model calculations indicate that nutrient control alone may be insufficient to permit seagrass recolonization if optical properties are dominated by particulate scattering from resuspended sediments.     

Temporal variability of remotely sensed suspended sediment and sea surface temperature patterns in Mobile Bay,Alabama

Distribution patterns of suspended sediments and sea surface temperatures in, Mobile Bay were derived from algorithms using digital data from the visible, near infrared, and infrared channels of the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-TIROS-N satellite. Closely spaced AVHRR scenes for January 20, 24, and 29, 1982, were compared with available environmental information taken during the same period. A complex interaction between river discharge, winds, and astronomical tides controlled the distribution patterns of suspended sediments. These same variables, coupled with air temperatures, also governed the distribution patterns of sea surface temperatures.     

Evaluating the support vector machine for suspended sediment load forecasting based on gamma test

Due to the various influencing factors on river suspended sediment transportation, determining an appropriate input combination for developing the suspended sediment load forecasting model is very important for water resources management. The influence of pre-processing of input variables by Gamma Test (GT) was investigated on performance of Support Vector Machine (SVM) with two kernels; Radial Basis Function (RBF) and polynomial in order to forecast daily suspended sediment amount in the period between 1983 and 2014 at Korkorsar basin, northern Iran. The best input combination was identified using GT and correlation coefficient analysis. Then, the SVM model was developed and the suspended sediment amount was forecasted with RBF and polynomial kernels. The obtained results in testing phase showed that GT-SVM (RBF kernel) model can estimate suspended sediment more accurately with the lowest RMSE (14.045 ton/day), highest correlation coefficient (0.88) and highest NSEC coefficient (0.88) than SVM (RBF kernel) model (RMSE?=?18.36ton/day, \( {R}^2=0.79, \) \( NSEC=0.73 \)) and had a better performance than the other models. The results indicated that in forecasting the first nine maximum values of suspended sediment load, GT-SVM (RBF) had a higher capability than the other models and could provide a more accurate estimation from the maximum rate of suspended sediment. The results of this study showed the capability of identifying the priority of the input parameters can change GT to a useful and technical test for input variables pre-processing to forecast the amount of suspended sediments.     

Some life history aspects of the seaboard goby (gobiosoma ginsburgi) in Rhode Island

This paper represents the first report of adultG. ginsburgi from Rhode Island waters since 1938. Gobies were collected only from subtidal shell communities in high salinity waters. Seaboard gobies eat a variety of benthic invertebrates but feed most heavily on harpacticoid copepods. Gravid females collected in July contained one size class of ova indicating a single spawning per season. Egg counts ranged from 1268 to 1977 per female. Larval densities indicate that peak spawning occurs in July and suggest thatG. ginsburgi is more abundant in the Sakonnet River and nearby Narragansett Bay than previously reported.     

Productivity and biomass of the seagrassThalassia testudinum along a gradient of freshwater influence in Charlotte Harbor, Florida

Eight meadows of the seagrassThalassia testudinum Banks ex König representing a gradient of freshwater influence in Charlotte Harbor, Florida (United States), were sampled on a bimonthly basis from April 1995 to August 1996. Spatial and temporal variation in the density, biomass, productivity, and epiphyte loads of short shoots were determined. Physical factors such as water temperature, salinity, and light extinction coefficients were also measured. Areal blade production (g dw m^?2 d^?1) ofT. testudinum was not strongly associated with water temperature, salinity, or the amount of subsurface irradiance reaching the bottom at each station. Variation in production could be described by a linear combination of the independent variables water temperature and salinity. Water clarity (expressed as the percent of subsurface irradiance reaching the bottom) was positively related to salinity. The lack of a clear relationship between water clarity and areal production was probably due to water clarity being highest during times of the year when water temperatures were too cold to support growth ofT. testudinum. Our results suggest that seagrass light requirements determined by averaging irradiance levels measured during the growing season might be more relevant than those established by averaging light measurements collected throughout the year. The use of field studies for estimating lower salinity tolerances of seagrasses might be inappropriate for those systems where water clarity is positively associated with salinity.     

Sedimentary matter and organic compounds in the aerosols and surface waters along the Transatlantic section

Concentrations and composition of suspended particulate matter and organic compounds (OC), including Сorg, lipids, hydrocarbons (HC), and pigments, were determined in the near-water aerosol layer and in surface waters on the meridional section across the Atlantic Ocean from the port of Ushuaia to the port of Gdansk (Cruise 47^th of the R/V Akademic Ioffe, March 26–May, 7, 2015). It was established that the distribution of OC (except for pigments) in aerosols, in general, repeats the distribution of particle number and weight concentrations of aerosols, with maximums in the influence zone of fluxes from Patagonia and African deserts. The concentrations of aerosols changed within wide ranges: from 1237 to 111739 particles/L for 0.3–1 μm fraction; and from 0.02 to 19.890 μg/m³ for aerosols collected by network method (flux of 0.02–34.4 mg/m² day). The contrasting mineral composition of aeolian material reflects the diversity of its provenances. In surface waters, the studied compounds were accumulated in the frontal river–sea area (runoff of the Rio-Colorado River) and with approaching the coast, especially in the English Channel. A simultaneous change of concentrations of suspended particulate matter and OC is observed only in open oceanic waters.     

基于能量平衡法的黑河中游灌溉渠道蒸发量估算

干旱区绿洲农田需要通过渠道引水进行灌溉,在此过程中蒸发损失不可避免,尤其是在渠系广泛分布的情况下,蒸发损失量大,如何估算这部分量对于干旱区水资源管理至关重要. 以甘肃张掖绿洲灌溉渠道为研究对象,采用Mihara所提供的基于能量平衡理论的经验方程,对渠道蒸发量进行了估算.结果表明：蒸发率在晴天时白天大于夜间,阴天时白天和夜间相差不大,气温和相对湿度是影响蒸发率的主要因子.累计蒸发量在晴天时白天是夜间的2倍左右,阴天时白天和夜间相差不大,蒸发率是直接原因.     

Clay-lead sorption relations

Bays, lagoons, and estuaries are sites where normal physicochemical processes result in accumulations of sediment and certain chemicals. Changes in water velocity and chemistry, and chemical interactions of sediment, biota, and water are factors that contribute to concentrating trace metals in coastal and lake sediments. To evaluate whether lead concentration is affected by mineralogy, kaolinite, illite, montmorillonite, and a zeolitic tuff were suspended in 10 and 20 mg/l concentrations of lead solutions [Pb(NO₃)₂] which were pH-adjusted incrementally through a range of 2.5 to 11.0. Samples were centrifuged after 24 hours to separate liquid from suspended sediment. Sediment-free solutions were run as controls. Lead concentrations were determined by atomic adsorption spectrophotometry. Results indicate that montmorillonite (Wyoming Bentonite) particles serve as lead adsorption nuclei over a broad pH range. Maximum sorption occurs as the solution reaches a pH of about 7.5. The kaolinite clay from Georgia strongly adsorbs trace amounts of lead at pH ranging from 3.0 to 4.5, where up to 95 percent of the lead is adsorbed by the clay. Little adsorption difference was found between the Fithian illite clay and zeolitic tuff from the Nevada Test Site in comparison to sediment-free solutions which were pH-adjusted. In concentrations of 10 to 20 mg/l montmorillonite and kaolinite clays serve as nucleation sites capable of adsorbing up to 95 percent of trace concentrations of lead within 24 hours. It appears that accumulations of lead in coastal lake and estuarine sediments are significantly influenced by:

1. pH changes which occur as river and coastal waters mix resulting in precipitation of lead, and
2. sorption of lead by suspended clays.

     

The chemical control of soluble phosphorus in the Amazon estuary

The factors which control concentrations of soluble inorganic phosphorus in the Amazon estuary are described and the efflux of phosphorus through the estuary is estimated using estuarine data collected on three field excursions (two in December, 1982 and one in May, 1983), and various laboratory mixing experiments. There is evidence to suggest that suspended sediments release significant quantities of inorganic phosphate to the estuarine waters. Bottom sediments collected from the estuary released soluble inorganic phosphorus at rates of approximately 0.2 μM day⁻¹, when suspended in mixtures of seawater and deionized water. Release rates depended on salinity but were independent of sediment concentrations. Inputs of phosphate persisted for approximately 3 days in suspensions with sediment concentrations of 0.5 g l⁻¹, but the duration of release increased to greater than 8 days at concentrations greater than 10 gl⁻¹. A one-dimensional dispersion model was developed incorporating input rates derived from the laboratory mixing experiments. The model predicts phosphate concentrations which are consistent with field observations, and it provides quantitative estimates for total fluxes of soluble inorganic phosphorus to the high salinity fringes of the estuary (~25 ppt) of approximately 15 × 10⁶molesday⁻¹ and 27 × 10⁶molesday⁻¹ during December, 1982 and May, 1983 respectively. The data indicate a significant phosphate loss from estuarine waters at salinities from 0–4 ppt, possibly associated with iron and humate removal. More than 50% of the predicted flux could be contributed by phosphate released from suspended sediments within the turbid part of the estuary.     

Suspended Matter,Chl-a,CDOM, Grain Sizes,and Optical Properties in the Arctic Fjord-Type Estuary,Kangerlussuaq, West Greenland During Summer

Optical constituents as suspended particulate matter (SPM), chlorophyll (Chl-a), colored dissolved organic matter (CDOM), and grain sizes were obtained on a transect in the arctic fjord-type estuary Kangerlussuaq (66°) in August 2007 along with optical properties. These comprised diffuse attenuation coefficient of downwelling PAR (K _d(PAR)), upwelling PAR (K _u(PAR)), particle beam attenuation coefficient (c _p), and irradiance reflectance R(−0, PAR). PAR is white light between 400 and 700 nm. The estuary receives melt water from the Greenland Inland Ice and stations covered a transect from the very high turbid melt water outlet to clear marine waters. Results showed a strong spatial variation with high values as for suspended matter concentrations, CDOM, diffuse attenuation coefficient K _d(PAR), particle beam attenuation coefficients (c _p), and reflectance R(−0, PAR) at the melt water outlet. Values of optical constituents and properties decreased with distance from the melt water outlet to a more or less constant level in central and outer part of the estuary. There was a strong correlation between inorganic suspended matter (SPMI) and diffuse attenuation coefficient K _d(PAR) (r ² = 0.92) and also for particle beam attenuation coefficient (c _p; r ² = 0.93). The obtained SPMI specific attenuation—K _d^*(PAR) = 0.13 m² g⁻¹ SPMI—and the SPMI specific particle beam attenuation—c _p^* = 0.72 m² g⁻¹—coefficients were about two times higher than average literature values. Irradiance reflectance R(−0, PAR) was comparatively high (0.09−0.20) and showed a high (r ² = 0.80) correlation with K _u(PAR). Scattering dominated relative to absorption—b(PAR)/a(PAR) = 12.3. Results strongly indicated that the high values in the optical properties were related to the very fine particle sizes (mean = 2–6 μm) of the suspended sediment. Data and results are discussed and compared to similar studies from both temperate and tropical estuaries.     

新疆阿勒泰克兰河中游地区冬季积雪分布及特性分析

新疆阿勒泰地区是中国季节性积雪水资源最为丰富的地区之一。2016年12月在克兰河中游地区开展了积雪观测,利用直尺和量雪筒测量雪深和雪密度,调查了积雪水资源的分布情况;利用针式温度计测量雪层温度,获取了雪层之间的温度梯度;利用雪特性分析仪和显微镜测量了积雪剖面的雪层密度、液态水含量、介电常数和雪粒径。通过分析研究区积雪水资源的空间分布和积雪特性的垂直分异发现：研究区雪深的分布非常不均匀,北部的雪深总体上大于南部,即使在同一地区,雪深也因风力等原因而分布不均匀;研究区总体上属于"干寒型"积雪,密度较小,且密实化迅速;各雪层属于干雪或者湿度极低的潮雪,绝大多数雪层的液态水含量在0.3%以下;积雪温度总体上从表层到底层逐渐升高,表层温度日变化较大;阴天积雪温度高于晴天,各雪层温度日变化小于晴天,且午后积雪会出现负温度梯度,冷中心出现在积雪次表层;雪粒径较小,雪粒长短轴比的最小值出现在中间层,且符合新雪的粒径特点。     

The oxygen isotope geochemistry of igneous rocks

Oxygen isotope analyses have been obtained for 443 igneous rock and mineral samples from various localities throughout the world. Detailed studies were made on the Medicine Lake, Newberry, Lassen, Clear Lake, S. E. Guatemala, Hawaii and Easter I. volcanic complexes and on the Bushveld, Muskox, Kiglapait, Guadalupe, Duluth, Nain, Egersund, Lac St. Jean, Laramie, Skaergaard, Mull, Skye, Ardnamurchan and Alta, Utah plutonic complexes, as well as upon several of the zoned ultramafic intrusions of S. E. Alaska. Basalts, gabbros, syenites and andesites are very uniform in O¹⁸/O¹⁶, commonly with δ-values of 5.5 to 7.0 per mil. Many rhyolite obsidians, particularly those from oceanic areas and the Pacific Coast of the United States, also lie in this range; this indicates that such obsidians are differentiates of basaltic or andesitic magma at high temperatures (about 1,000° C). They cannot represent melted sialic crust. The only plutonic granites with such low δ-values are some of the hypersolvus variety, suggesting that these also might form by fractional crystallization. Obsidians from the continental interior, east of the quartz-diorite line, have higher δ-values. This is compatible with their having assimilated O¹⁸-rich sialic crust. A correlation generally exists between the O¹⁸/O¹⁶ ratios of SiO₂-rich differentiates and the chemical trends in volcanic complexes. High O¹⁸/O¹⁶ ratios accompany those trends having the lower Fe/Mg ratios, while ferrogabbro trends are associated with depletion in O¹⁸. Variations in oxygen fugacity may be responsible for these effects, as abundant early precipitation of magnetite should lead to both O¹⁸-enrichment and Fe-depletion in later differentiates. Plutonic granites have higher O¹⁸/O¹⁶ ratios than their volcanic equivalents, because (a) their differentiation occurred at much lower temperatures, or (b) they are in large part derived from O¹⁸-rich sialic crust by partial melting or assimilation. Also, the oxygen isotope fractionations among coexisting minerals are distinctly larger in plutonic rocks than in volcanic rocks. This is in keeping with their lower crystallization temperatures and their longer cooling history, which promotes post-crystallization oxygen isotope exchange. Hydrated obsidians and perlites have δO¹⁸-values that are much different from their primary, magmatic values. A correlation exists between D/H and O¹⁸/O¹⁶ ratios in hydrated volcanic glass from the western U.S.A., proving that the isotopic compositions are a result of exchange with meteoric waters. The O¹⁸ contents of the glasses appear to be about 25 per mil higher than their associated waters; hence, these hydrated glasses have not simply absorbed H₂O, but they have exchanged with large quantities of it. The igneous rocks from Mull, Skye, Ardnamurchan and the Skaergaard intrusion are all abnormally depleted in O¹⁸ relative to “normal” igneous rocks. This is a result of their having exchanged at high temperatures with meteoric water that was apparently abundant in the highly jointed plateau lavas into which these igneous rocks were intruded. In part, this exchange occurred with liquid magma and in part with the crystalline rock; in the latter case the feldspar was more easily exchanged and has become much more depleted in O¹⁸ than has coexisting quartz or pyroxene. The later differentiates of the Muskox intrusion are markedly O¹⁸-rich, but this is not a result of fractional crystallization. It is in large part a result of deuteric exchange between feldspars and an oxygen-bearing fluid (H₂O ?) that was either O¹⁸-rich or had a relatively low temperature. This phenomenon was also observed in a number of granophyres from other localities, particularly those containing brick-red alkali feldspar. The exchanged feldspars in all these examples are turbid or cloudy, and may be filled with hematite dust. It is concluded that most such feldspar in nature is the result of deuteric exchange and is probably drastically out of oxygen isotopic equilibrium with its coexisting quartz.     

Movements and population structure of Atlantic menhaden indicated by tag returns

Over 968,000 adult Atlantic menhaden,Brevoortia tyrannus, were tagged from 1967 to 1969 and over 85,000 juvenile menhaden were tagged from 1969 to 1973. Recoveries of these tagged fish through 1975 provide direct evidence that Atlantic menhaden consist of a single population that over-winters in offshore waters off the southeastern coast of the United States, moves northward in spring and stratifies along the coast by age and size during summer, and moves southward in late autumn.