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1.
The number of migrating alewives in the Parker River, Massachusetts, can be counted visually by standing at the upper end of each of the 6 fish ladders in the system. Estimating the entire run of up to a month’s duration by this procedure is not economically feasible, but we suggest a subsampling procedure that can provide sufficient accuracy and be economical. The reliability of periodic sample counts when used to estimate population numbers of anadromous alewives (Alosa pseudoharengus) was indicated by the low variance of paired counts, small random errors of individual counts, and by the low variability between counts on days of large runs in the Parker River. Analyses of computer-simulated runs using actual data suggested that short counts taken frequently are superior to longer counts taken less often. Both field and computer-simulated data suggested that ten-minute counts taken hourly will estimate the true population of alewife runs within 10% error at the .05 level of probability.  相似文献   

2.
A comparative study of the standing crop of marsh vegetation was made of the Patuxent River and Parker Creek, two tributaries of Chesapeake Bay. The biomass of marsh vegetation in the tidal freshwater and brackish regions of the Patuxent was relatively uniform with regard to salinity, seasonally high concentrations of dissolved nitrogen, and phosphorus and nutrient gradient. Maximum values of biomass occurred in the tidal freshwater and slightly brackish water region of Parker Creek, a system whose nutrient concentrations approximated 20% of those of Patuxent River. Biomass values for the Patuxent River and Parker Creek averaged about 1417 and 895 g m?2 dry weight, respectively. Estimates of total annual marsh production based on the maximum standing crop was 27×103 and 519 metric tons, respectively, for the Patuxent River and Parker Creek.  相似文献   

3.
Corbicula manilensis was found in the gizzards of 24 ducks of 5 species taken from the James River, Virginia, between 1973 and 1976. Percent average volume in these species ranged from trace to 6%. This is the first known occurrence of this exotic clam in the food of duck in Chesapeake Bay. A total of 135 other food items was identified from the 116 gizzards of 9 species that were examined. Food that predominated includedCyperus spp.,Leersia oryzoides, Polygonum spp., andZea mays. The great diversity of food consumed in this fresh tidal section of the James River indicates the high value of these wetlands to waterfowl. *** DIRECT SUPPORT *** A01BY015 00008  相似文献   

4.
《China Geology》2019,2(2):169-178
A comparative comparative study on the detrital mineral composition of stream sediments of the Yangtze River (Changjiang) and Yellow River (Huanghe) shows that, light minerals of the Yangtze River basin were mainly quartz, feldspar, and detritus, the compositional characteristics of light minerals differed among tributaries, the main stream had a generally higher maturity index than tributaries; heavy mineral content tended to decrease progressively from the upper stream to lower stream of the Yangtze River, the primary assemblage was magnetite-hornblende-augite-garnet-epidote, and diagnostic minerals of different river basins were capable of indicating the nature and distribution of the source rock. Detrital mineral assemblages in sediments of tributaries and the main stream of the Yellow River were basically similar, Primary heavy mineral assemblage was opaque mineral-garnet-epidote-carbonate mineral and alteration mineral. Variations in the contents of garnet, opaque mineral, and hornblende mainly reflected the degree of sedimentary differentiation in suspended sediment and the hydrodynamic intensity of a drainage system. The heavy mineral differentiation index F revealed sedimentary differentiation of diagnostic detrital mineral composition due to changes in regional hydrodynamic intensity and can serve as an indicator for studying the dynamic sedimentary environment of a single-provenance river and the degree of sedimentary differentiation of its detrital minerals. Changes in detrital mineral content of the Yellow River was not completely controlled by provenance but reflected gravity sorting of the detrital mineral due to variations in the ephemeral river hydrodynamic intensity and sedimentary environment, however the index changing of Yangtze River were mainly influenced by the complex sediment sources. Therefore caution must be exercised in using the detrital mineral composition of marginal sea to determine the contribution of the Yangtze River and Yellow River.© 2019 China Geology Editorial Office.  相似文献   

5.
Ninety-four prespawning adult Atlantic sturgeon (Acipenser oxyrinchus) were sampled in the Hudson River for age, sex, body size, gonad weight, fecundity, mature oocyte size, and plasma concentrations of gonadotropins, sex steroids, and vitellogenin during the spring spawning migrations in 1992 and 1993. In males, the age and total length ranged from 12 yr to 19 yr and from 133 cm to 204 cm and in females from 14 yr to 36 yr and from 197 cm to 254 cm. The majority of males were 13–16 yr old, and females were 16–20 yr old. Some females had residual atretic ovarian bodies, presumably remaining from a previous spawning and indicating iteroparity. Pre-ovulatory condition was recognized by migration of the germinal vesicle or by germinal vesicle breakdown and by significantly elevated plasma gonadotropins, progesterone, and vitellogenin. All pre-ovulatory females were captured upriver from Hudson River kilometer 136. Individual fecundity ranged from 0.4 million to 2.0 million eggs and oocyte diameter from 2.4 mm to 2.9 mm, and both characters exhibited a significant (p<0.05) positive relationship with female body size. Iteroparous females, tentatively identified by the presence of atretic bodies remaining in the ovary from a previous spawning, had significantly (p<0.05) higher fecundity and produced larger eggs, compared with females spawning presumably for the first time.  相似文献   

6.
Movements of spawning rainbow smelt, Osmerus mordax, were followed in the Parker River estuary, Massachusetts during 1974 and 1975. Fish marked with vinyl subcutaneous tags (n=1,492) or fin clips (n=577) were recaptured on three separate spawning sites in three different tributaries; the distribution patterns of marked fish indicated a homogeneous spawning stock. Interstream movement may have been facilitated by tidal transport since smelt ascended to the spawning sites on flood tides and moved downstream as tides ebbed. Rates of recapture of fish tagged on the spawning areas were 2.61 and 5.61 times greater for males than females in 1974 and 1975 respectively. Individual tagged males were recovered up to four times during the spawning period; females were recaptured a maximum of once. The proportion of age II and older females sampled from the angling fishery prior to spawning in 1975 (47.38%) was greater than the cumulative proportion sampled on the spawning sites (11.93%) due to longer spawning period of individual males.  相似文献   

7.
Altered river flow has been suggested as a cause for the low recruitment of striped bass,Morone saxatilis, in the Roanoke River (North Carolina) because of its effect on the proximity of zooplankton and larval striped bass. This results in unsuccessful feeding and subsequent starvation, which was considered to be a major mortality factor. Other mortality factors, such as parasitism and copepod predation on age-0 fish, may also be regulated to some extent by changes in river flow. The relationship of cestode plerocercoids, trematode metacercaria, mussel glochidia, and cyclopoid copepod predators with age-0 fish was evaluated in the lower Roanoke River and western Albemarle Sound from plankton net collections made in 1984 to 1986 and 1988. Plerocercoid prevalence was higher under low river flow conditions than under high flow conditions in darters (Percidae; 16.7% vs. 9.2%), minnows (Cyprinidae; 28.8% vs. 4.7%), andMorone (1.9% vs. 0%). Gut analysis of the age-0 fish revealed that copepods (source of the plerocercoids) were a major diet component ofMorone and darters but not of minnows or herring (Clupeidae). Decreases in river flow were associated with increases in copepod density (Pearson r=?0.62; p=0.0001) and plerocercoid prevalence inMorone (Pearson r=?0.29; p=0.03). The low correlation value forMorone may be quite strong considering the complexity of the variables associated with prevalence. Metacercaria were found only inMorone and minnows, and prevalence and mean intensity were less than that found for plerocercoids. Mussel glochidia prevalence was less than 0.5% for all affected taxa, an order of magnitude less that that found in other studies. The low value may indicate that the mussel population in the Roanoke River is declining. Prevalence of attacks by the predatory copepodMesocyclops edax on age-0 fish was similar to that in Chesapeake Bay, and striped bass was the primary prey. Spatial and temporal proximity of copepods and fish prey may be the key factors in regulating copepod attacks. The low prevalence of parasites and copepod predators seen in this tudy would suggest that mortality from these sources may not be a major factor in age-0 recruitment in this system. Confirmation of these conclusions would require a more controlled experimental approach.  相似文献   

8.
In this first study of lignin geochemistry in the world’s longest river on an island, surface sediments were collected along the Kapuas River, three lakes in the upper river, a tributary in the lower river and a separate river during June-July 2007 and December 2007-January 2008. The samples were analyzed for lignin-derived phenols and bulk elemental and stable carbon isotope compositions. Λ values (the sum of eight lignin phenols, expressed as mg/100 mg organic carbon (OC)) ranged from 0.13 to 3.70. Ratios of syringyl/vanillyl (S/V) and cinnamyl/vanillyl (C/V) ranged from 0.34 to 1.18 and 0.28 to 1.40, respectively, indicating the presence of non-woody angiosperm tissues. The high vanillic acid to vanillin (Ad/Al)v (0.71-2.01) and syringic acid to syringaldehyde (Ad/Al)s (0.72-2.12) ratios indicate highly degraded lignin materials. In the upper Kapuas River, highly degraded soil materials discharged from lands that were barren as a result of deforestation activities were detected in the locations directly in those vicinities. The middle Kapuas River showed rapid organic matter degradation, probably due to the presence of fresh terrestrial and phytoplankton organic matter fueling the biogeochemical cycling. The Kapuas Kecil River, one of the two branches in the lower reach of the Kapuas River, showed higher levels and diagenesis of sedimentary organic matter due to input from anthropogenic sources and increased marine organic matter near the mouth. This study shows that different stretches along the river exhibit different levels and composition of sedimentary organic matter, as well as different carbon dynamics, which is directly attributable to the varying landscapes and quality of organic matter.  相似文献   

9.
The influence of hydrodynamics on the chemical composition of sediments is based on the uneven distribution of element abundances in different size fractions. In this study, 72 size‐fractional sediments from the Huanghe (Yellow River) and Changjiang (Yangtze River) riverbeds were measured with XRD, SEM, ICP‐AES and ICP‐MS. The analysis results show that the mineral and chemical characteristics change with grain size in the Huanghe and Changjiang sediments. According to the principal components analysis, three independent geochemical factors were found. The first factor elements, Zr, Hf, Th, U, Y, La and TiO2 are influenced by the existence of heavy minerals. The second factor elements, Al2O3, alkalis, alkaline earth (excluding Ca and Sr) and most of the transitional metals are dominated by clay minerals. The third factor group includes Ca and Sr, which were controlled by calcium‐bearing mineral contents and chemical weathering intensities. The various grain size distributions greatly affect the mineralogical and chemical compositions of bulk sediments. Compared to other size fractions, the 5–6PHI size fractions of the Huanghe and Changjiang sediments have special mineralogical and chemical compositions, and intermediate volume percentages. Weight or volume percentage of each size fraction may be more suitable than mean grain‐size of the bulk sediment to elucidate the grain size effects. Chemical Index of Alteration (CIA) values increase steeply with decreasing grain size, while Weathering Index of Parker (WIP) values are relatively stable. Because of the big influence of the abundance of clay minerals on CIA values, it is questionable to use CIA as a proxy of weathering intensity. Considering the clay mineral effects, stability in values and heterogeneous material properties, WIP has the potential to indicate the chemical weathering intensity of sediments. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

10.
Two hydrobiid gastropods are important components of the salt marsh pool invertebrate community at the Parker River National Wildlife Refuge near Rowley, Massachusetts.Hydrobia truncata was found to be the dominant snail in the two higher salinity pools, withSpurwinkia salsa becoming the more important at lower salinities.H. truncata began to reproduce between May 19 and June 9. Cohorts lasted about 14 months, and 99% of production occurred during the first 12 months. Shell height inH. truncata was greater in pool 2 which had a much lower density than pool 1 on all dates of the 1980 growing season. Snail densities were positively correlated with the presence of floating algal mats of the genusCladophora, but the snails apparently do not graze on this alga.H. truncata production, calculated by four methods, ranged from 41.0 to 78.1 and averaged 60.5 g m?2 cohort?1 for pool 1, but were estimated to be less than 10% of these values in pool 2. In pool 1,H. truncata was estimated to assimilate 55% of net primary production or 28% of total pool energy income when detritus income was included. When found in the same pool asH. truncata, Spurwinkia salsa ordinarily comprised less than 0.5% of the total snail population.S. salsa veligers did not metamorphose into juveniles until July and were partitioned fromH. truncata by size durig their first growing season. The main separation between the two species, however, appeared to be spatial, on a salinity gradient. TheS. salsa cohort lasted about 19 months with a few individuals surviving to 27 months in their third summer.  相似文献   

11.
Soil samples were collected at different locations from Etche and Obio Akpor local government area (LGA) of River State in Niger Delta. The n-alkane and polycyclic aromatic hydrocarbons were determined qualitatively and quantitatively using GC-FID. The concentration of PAHs in the soil samples ranged from 7.40 to 78.3 ng/g. The highest concentration of PAHs was recorded in Agbada 1 flow station, while the lowest concentration was recorded in Agbada 2 flow station. A significant level of pollution was also observed in the soil of Bomu pipeline at Obio Akpor LGA. Also, the distribution of n-alkanes in the samples was also used to assess the level of pollution in the studied area. Various n-alkanes and PAHs ratios were obtained to know the major source of pollution in the area under study. The main source of pollution was pyrolytic, which might be due to the gas flaring activities going on in the study area. Also, the results showed that n-alkanes could also be a complementary tool in assessing pollution and source apportionment.  相似文献   

12.
Juvenile spot,Leiostomus xanthurus (Pisces), were collected at 2-h intervals over two 48-h periods in a tidal creek in North Inlet, South Carolina, during July 1986. Gut fullness, dry gut contents weight as a percentage of fish wet weight, was measured to test the hypothesis that feeding intensity is randomly distributed through time. Spot were also collected and serially sacrificed from a holding tank to estimate their gut evacuation rate. Gut fullness was greatest during periods of ebb and high tides and was little affected by the amount of light available. Gut contents were evacuated at a rate of about 15% per hour in the laboratory, in close agreement with field emptying times of about 6 h from peak fullness to empty guts. A conservative estimate of daily ration for juvenile spot (19–42 mm standard length) was 4.5% of their live body weight per day. Studies of spot feeding ecology can be greatly affected by when fish are collected during the tidal cycle.  相似文献   

13.
Cadmium (Cd) variations were investigated over an annual cycle (12 surveys between February 1998–January 1999) in the Morlaix estuary (Brittany, France) in both the water column and the benthic compartment in relation to hydrological conditions. The drainage basin of the Morlaix River estuary is predominantly agricultural in character. Dissolved Cd concentrations in the water column varied from 0.04 to 0.48 nM. Particulate Cd concentrations ranged from 1 to 64 nmol g−1. These concentrations reach levels commonly observed in estuaries affected by heavy industrial activities. Extensive agricultural activities in the drainage basin may be responsible for Cd levels above pristine conditions. Metal concentrations varied significantly over the seasonal cycle and the dissolved fraction exhibited high values in summer months. Particulate concentrations were always lowest during this season. In the benthic compartment, Cd concentrations in surface sediment varied from 0.4 to 5.0 nmol g−1 and from 0.2 to 5.0 nM in porewaters. Concentrations in sediment were slightly affected by Cd contamination and temporal changes were important over the seasonal cycle. The variations seem to be controlled by the succession of sedimentation and erosion processes, which are tightly linked to seasonal changes in river discharge. A box model was constructed based on known Cd sources and sinks in the estuary. Cd is chiefly brought into the estuary by the Morlaix River and accumulates within the estuary. The accumulation within the estuary represents from 6.3 to 7.2 kg yr−1.  相似文献   

14.
Seven species of mojarras (Gerreidae) were collected from three stations in the Indian River lagoon near the Sebastian Inlet, Florida over an eighteen month period to study spatial and temporal variations in occurrence and feeding habits. Two major habitats common to this area were represented in the study; a sandy beach and a seagrass flat. Of the 2,899 gerreids collected,Eucinostomus gula represented 67% and was found primarily in theHalodule seagrass site. The next most abundant species,E. argenteus (11%),E. jonesi andE. lefroyi (each 10%), were found most frequently at the inlet site.Diapterus auratus, E. melanopterus, andGerres cinereus were captured infrequently and were considered incidental. Prey items found included amphipods, bivalves, copepods, fish eggs, foraminifera, isopods, nematodes, ostracods, polychaetes and crustacean parts. Significant amounts of sand and unidentifiable amorphous debris were also included in the gut content analysis. Little interspecific variation in diet was found among the four major species examined. The general shift seen from a diet composed primarily of copepods and other crustaceans to one of polychaetes suggests an intraspecific ontogenetic progression. Spatial variations in diet composition were also indicated between the two major habitats. Feeding analyses showed gerreids to be diurnal feeders with the greatest consumption (total gut content weight) occurring at dusk.  相似文献   

15.
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.  相似文献   

16.
Identification and characterization of aeolian deposits in arid environments provide information on mechanisms of loess and sand accumulation. The objectives of this study were to (i) identify the distribution of aeolian deposits, (ii) discriminate loess and sand deposits using granulometric data, and (iii) describe the aeolian deposition in Sarakhs area, northeastern Iran. Particle size distributions of 26 surface samples were determined using a laser grain-size analyzer. Fine sand, very fine sand, and very coarse silt were dominant fractions in studied sediments, and the sum of these fractions ranged from 46.9% in loess deposits to 93.8% in sand dunes. The mean grain size (M z ) of sand dunes ranged from 3.31 to 3.54 ?, which gradually changed to 4.09 to 5.50 ? in loess deposits. Sorting, skewness, and kurtosis ranged from 0.84 to 1.94 ?, 0.18 to 0.49, and 0.76 to 2.38, respectively. Aeolian deposits in the area resulted in the incorporation of Hariroud River system and Kopeh Dagh Mountains for aeolian particle production and accumulation. Alluvial comminution in Hariroud River is suggested the main mechanism of sand and silt production and flood plain environment the main reservoir of these particles. The mountains of Kopeh Dagh act as a barrier and play a key role for sand and loess accumulation.  相似文献   

17.
The benthic fauna of a small cove of the Hudson River containing the aquatic plantMyriophyllum spicatum L. was studied for a one-year period. The fauna was characteristic of oligohaline zones of United States east coast estuaries. Total abundance of invertebrates retained on a 0.12 mm mesh sieve averaged 124,631 organisms m?2 (sediment and plant populations combined) and ranged up to 196,000 m?2. During the May–August period, invertebrates living on the plants comprised 16–35% of the invertebrate fauna in the cove. Chironomid larvae were the most abundant organisms on plants and the third most abundant in the sediments. Two assemblages of chironomid species were recognized; one lived solely in the sediments, the other lived primarily on the plants.Chironomus decorus andTanytarsus sp. dominated the former group andCricotopus sylvestris the latter. The chironomidDicrotendipes modestus utilized both habitats. During the May–August period, chironomid biomass on the plants comprised approximately 50% of total chironomid biomass in the cove. The mean dry-weight biomass of chironomids in the cove (1.6 g m?2) is estimated to be sixteen times greater than that of the fauna in the deeper areas of the river. Because chironomid larvae are eaten by fish and invertebrates, shallow water regions with their rich chironomid (and other fauna) may contribute importantly to the trophic dynamics of estuarine systems. *** DIRECT SUPPORT *** A01BY009 00004  相似文献   

18.
Data from sonic tracking during the period 1983–1987 enabled us to define the areas used and the seasonal pattern of movement by adult shortnose sturgeon (Acipenser brevirostrum) in the Delaware River. Tagged adults (n=28) ranged from 544 mm to 871 mm fork length and 1,510 g to 7,125 g. Twenty-six tags were carried for 7–225 d. Most of the tagged sturgeon were relocated in the tidal portion of the river. Sturgeon that overwintered in the upper tidal river near Trenton, New Jersey, began traveling upstream in late March to the nontidal river above Trenton where spawning presumably occurred from late March through April. After spawning, sturgeon traveled rapidly downstream into the tidal portion of the river near Philadelphia, Pennsylvania, where they remained through the end of May. Before the end of June, most sturgeon returned upstream and re-entered the upper tidal river near Trenton, where most apparently remained for the summer and winter. In general, the same pattern was apparent for both sexes. As a result of the intensive use of the river between Philadelphia to just above Trenton, any alterations or additional insults to the river should consider the impact on this endangered species.  相似文献   

19.
The Wujiang River is an important tributary to the Changjiang River that has been intensively impounded for hydropower exploitation. To understand the potential impact of reservoir construction on the riverine inorganic carbon transport, seasonal longitudinal sampling was conducted in four reservoirs Hongjiadu (HJD), Dongfeng (DF), Suofengying (SFY) and Wujiangdu (WJD) along the Wujiang River from April 2006 to January 2007. Results indicated that damming the river induced an obvious discontinuity of water chemistry in the warmer seasons. δ 13C of dissolved inorganic carbon (DIC) ranged from ?3 to ?11.4 ‰, likely as the results of photosynthesis, respiration and carbonate weathering. During periods of thermal stratification, the addition of CO2 from respiration to hypolimnion and the deep water release for hydropower generation led to higher pCO2 downstream, as well as 13C depletion in DIC and undersaturated to calcite. An estimate of DIC budget indicated that only DF reservoir was the sink for DIC while reservoirs HJD, SFY and WJD were the sources for DIC. However, when the retained water was taken into account, for the reason of water storage occurring mainly in HJD and DF, all reservoirs became the sources for DIC with exporting rates of 26.68, 7.97, 6.22 and 11.80 % for HJD, DF, SFY and WJD, respectively.  相似文献   

20.
In this contribution the record of a Nothrotheriinae (Xenarthra, Tardigrada) ground sloth is reported from the Late Pleistocene of the Northern Pampa of Santa Fe Province, Argentina. The stratigraphic unit where the fossil was collected corresponds to fluvial-palustrine sediments of the Timbúes Formation, outcropping along the Carcarañá River valley. The relative stratigraphic position of this lithostratigraphic unit, observed in several sections mainly on the Paraná River cliffs near Carcarañá River distal area, suggests that it was deposited during the Last Interglacial Stage. The specimen (MPAHND-135), assigned to Nothrotherium cf. torresi, is represented by the proximal two-thirds of a left femur that shows a prominent lesser trochanter and no connection between the third trochanter and the ectepicondyle. The presence of Nothrotherium cf. torresi in sediments related to humid conditions supports the idea that Nothrotheriinae had great ecological tolerance and was capable of inhabiting climates ranging from cold and arid, as was previously proposed, to warm and humid.  相似文献   

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