Fish populations of the Avon‐Heathcote estuary

Characteristic organisms are tabulated, and the substrate conditions briefly described for seven habitats in the Avon‐Heathcote Estuary, Christchurch, New Zealand. Temperatures and water movements within the estuary are outlined.

From April 1965 to April 1966, samples were collected by short otter‐trawl shots, gill netting, beach seine hauls, and dip netting; the limitations of the gear are noted. The distributions and movements are recorded for nine fish species : sand flounder, Rhombosolea plebeia (Richardson) ; yellow‐bellied flounder, Rhombosolea leporina (Hutton) ; common sole, Peltorhamphus novae‐zeelandiae (Gunther) ; ye'llow‐eyed mullet Aldrichetta forsteri (Cuvier and Valenciennes); kahawai, Arripis trutta (Bloch and Schneider); spotty, Pseudolabrus celidotus (Bloch and Schneider); cockabully, Tripterygion nigripenne (Cuvier and Valenciennes) ; common bully, Gobiomorphus basalis (Gray); and globe fish, Spheroides richei (Freminville).

Length‐frequency distributions showed that most of the nine species of fish used the estuary as a feeding area for adults and as a nursery area. Only two species did not migrate to and from the sea.

Length‐weight relationships for eight species showed that weight was a function of length approximately cubed, and that the exponential equation could be used to predict weight from length.

Regressions of caudal fin length on standard length for four species gave a positive correlation (r = +0.95). Relative proportions of body length to caudal fin length were related to habitat; fish of benthic habits had proportionally shorter caudal fins than pelagic fish.     

Fish populations of the Avon‐heathcote estuary

Details are given of gut‐content analyses for nine fish species from the Avon‐Heathcote Estuary, Christchurch, New Zealand: sand flounder, Rhombosolea plebeia (Richardson); yellow‐bellied flounder, R. leporina (Hutton); common sole, Peltorhamphus novaezeelandiae (Gunther); yellow‐eyed mullet, Aldrichetta forsteri (Cuvier & Valenciennes); kahawai, Arripis trutta (Bloch & Schneider); spotty, Pseudolabrus celidotus (Bloch and Schneider); cockabully, Tripterygion nigripenne (Cuvier & Valenciennes); common bully, Gobiomorphus basalis (Gray); and globefish, Spheroides richei (Freminville). The percent occurrences of each food type recorded over Ihe sampling period (April 1965‐April 1966) for each species are compared. Monthly food tables are given for those species of which suitably large samples were obtained (sand flounder, yellow‐bellied flounder, common sole, yellow‐eyed mullet, and globefish). Where possible, the dietary occurrence of different food types is related to environmental and other factors observed or considered likely to influence food selection.     

Structure of a mudflat diatom community in the Avon‐Heathcote Estuary,New Zealand

Parameters of community structure (species composition and relative abundance, number of taxa, diversity, evenness, and cell density) were measured for a mudflat diatom community in the Avon‐Heathcote estuary, New Zealand. Fifty three diatom species were identified: 25 taxa (species and varieties) are new New Zealand records. The Shannon‐Wiener information index (H') was 3.46, indicating high diversity. Evenness (J') ranged from 0.57–0.67. The association between the biomass of the pulmonate gastropod, Amphibola crenata, and benthic diatom community structure was studied using large open enclosures (4.0 m²) to manipulate snail biomass. Community structure was compared at 0, 5 (natural biomass), and 10 g A. crenata dry weight per m. A similarity index (SIMI=0.88–0.95), as well as H’ and J’ indicated close similarity between the diatom assemblages within all enclosures, but number of taxa increased from 33 to 49 with increasing snail biomass. Cell densities were significantly lower at high snail biomass (6088 valves per mm²) compared to enclosures with no snails (10 110 valves per mm ). A. crenata had a higher ratio of diatom fragments to whole diatom valves in its faeces (2.42) than in its crop (0.55), indicating that it is capable of fragmenting diatoms.     

The Study of Fish Eggs, Larvae and Juveniles of the Estuary at Beitang

The fish eggs, larvae and juveniles were collected during 25 cruises from April to No-vember 1980 and 1981 respectively. They were represented by 40 species, 36 genera, 19families and 9 orders. According to their habit, the fish eggs, larvae and juveniles couldbe referred to three types: (1) shallow sea and estuary type; (2) migration type of outersea; (3) fresh water type. The shallow sea and estuary species were 29 in number, occu-pying 72.5% of the total; the migration species were 3 in number, occupying 7.5% of thetotal; the fresh water species were 8 in number occupying 20% of the total.     

Further evidence for the existence of sub‐littoral populations of toheroa,Amphidesma ventricosum Gray (eulamelli‐branchiata), off the west coast of New Zealand

The finding of shells of toheroa (Amphidesma ventricosum Gray) which had been drilled by gastropods absent from the littoral zone, is presented as evidence for the existence of sub‐littoral populations of toheroa.     

Study on the Improvement of Sea-Entering Waterway in the Changjiang Estuary

The Changjiang Estuary is the doorway of the Shanghai Harbour and the throat for the six provinces in the Changjiang River drainage area. However the minimum water depth of the waterway in the estuary is only about six meters, so that the development of the Shanghai Harbour and the utilization of water transportation on the Changjiang River have been greatly restrained. Since 1975, the depth of the sea-entering waterway of the Changjiang Estuary has been successfully increased by one meter. This article has made a comprehensive summing-up about the selection of waterways, the determination of the line for dredging and disposal of the dredged material, thus providing reference data for future work in increasing the depth of the waterway of the Changjiang Estuary and for controlling similar waterways of other estuaries.     

Phosphate limitation of phytoplankton growth in the Changjiang Estuary

Laboratory experiments of bioassay with Pltaeodaetytum tricornutum, Chatoceros didymus, Chaetoreros calcitraus and Heterogtoea sp. sampled from the Changjiang Estuary in spring and summer, 1986, indicated that both N and P limit phytoplankton growth in the medium with N : P ranged between 8-30, and N limits phytoplankton production in the medium with N: P<8, while P is the limitary nutrient in the N : P>30. Generally, N : P in the Changjiang Estuary waters is 2 times higher than Redfield ratio. The bioassay experiments with high N : P water samples collected from Changjiang Estuary show that phytoplankton production is limited by P. Phytopiankton appears to give priority to the uptake of P at all periods of time. And the optimum N:P for phytoplankton growth is determined to be 18.     

Stability of the Guiding Dike in Yangtze Estuary Under the Wave Load

1 .IntroductionIt has beenrealizedthat constructing gravitystructures onsoft soil foundations is a difficult task,especiallyinthe marine area where boththe geological and environmental conditions are severe .Thisisnot only because the bearing capacity of the soft foundation is relatively low, but also because thestrength of the soft soil will befurther weakened bythe waveloading (Andersenet al .,1988 ;Ander-sen and Lauritzsen,1988 ; Yasuhara ,1988) .The strength weakening may cause serious d…     

The state‐of‐the‐art in marine navigation

Tide gauges distributed all over the world provide valuable information for monitoring mean sea level changes. The statistical models used in estimating sea level change from the tide gauge data assume implicitly that the random model components are stationary in variance. We show that for a large number of global tide gauge data this is not the case for the seasonal part using a variate-differencing algorithm. This finding is important for assessing the reliability of the present estimates of mean sea level changes because nonstationarity of the data may have marked impact on the sea level rate estimates, especially, for the data from short records.     

On sedimentation of phosphorus in specified area outside of the Changjiang Estuary

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Study of Bed Friction Factor for the Wu River Estuary

1 .IntroductionThe Wu River systemis the most important estuary river in central Taiwan.Its tidal wave canrange over 5 meters .Itis considered as one of the most magnificent scenesin Taiwan.The understand-ing of the tidal flowof the estuaryis essential to…     

Preliminary study of the retention mechanism of planktonic copepods in the Jiulong Estuary in China

The horizontal and vertical distribution patterns of five planktonic copepods,Calanus sinicus, Acartia pacifica, Tortanus derjugini, Acartiella sinensis and Pseudodiaptomus poplesia, predominant in the Jiulong Estuary, were investigated from May 2003 to April 2004. The results showed that the distribution of these copepods was related to the tidal period but that each species had its own specific pattern. C. sinicus showed no tidal vertical migration behavior and was thought to be a non-resident species in this estuary. Among Acartia pacifica,T. derjugini,Acartiella sinensis, more individuals occurred in the surface than in the bottom waters during flood tide, and the pattern was reversed during ebb tide. The epibenthic copepod P. poplesia usually remained in the bottom waters in the upstream part of the estuary, but it displayed strong tidally-oriented vertical migration in the middle reaches of the estuary.Taking into account the hydrographic characteristics of the Jiulong Estuary,it was hypothesized that the planktonic copepods in this estuary had more or less adopted the mechanism of vertically migrating to the surface waters during flood tide in order to make use of the inflowing tide, and then sinking to the bottom during ebb tide to avoid being carried out of the estuary by net outflow.     

Bottom Sediment Transport in the Flood and Ebb Channels of the Changjiang Estuary

Nanxiaohong and Nangang main south channel are chosen as the typical flood and ebb channels. Hydrodynamics analysis based on field hydrological and sediment data is conducted with Gao-Collins model to analyse sediment transport trends. Also, the grain size distribution analysis of the bottom sediment sampled in Sep. 2001 is used as the base of the analysis. The result shows that the sediment in Nanxiaohong is from the rive mouth area. The sediment transports upwards with the flood flow which is stronger than the ebb flow, i.e., in the direction of SE-WN. The sediment in main south channel comes from upward. They transport downwards with the ebb flow. which is stronger than the flood flow, i.e., in the direction of WN-SE. The directions, sources and mechanism of sediment transport are identified according to comprehensive analyses of the observed data on hydrodynamics and sediment.     

Analysis on the Circulation of the Yangtze River Estuary Based on ADCP Measurements

According to analysis on field data obtained by ADCP(Acoustic Doppler Current Profiler),the flow regime of the Yangtze River Estuary is studied by use of a 3-D numerical model.The flow field characteristics,under the influence of Coriolis force,saltwater intrusion and freshwater inflow and tidal current interaction,are depicted in details.The main driving forces and some important effective factors of lateral,longitudinal and horizontal circulation are also analyzed.     

Effect of the Twin Jetties as A Regulating Structure at the Tao-er Estuary

The phase one project of the twin jetties at the Tao-er Estuary yields no effect on the flow, and there is a large area of deposition. A numerical model is employed to simulate the flow field, and the scouring and silting in the channel be-tween the two jetties are analyzed. The results show that the effective tidal flux between the two jetties is reduced due to the notch located at the heel of the east jetty, and the effect of contraction-flush is not obvious. As for the regulation of this kind of estuary under the tide action, the capability of tidal flux should be fully used.     

State‐of‐the‐art sea level and meteorological monitoring systems in the intra‐Americas sea

State‐of‐the‐art technology is presently being used for the acquisition of water level and meteorological data in the Intra‐Americas Sea to support the Global Sea Level Observing System (GLOSS) network of sea‐level monitoring stations. GLOSS stations provide data for the investigation of regional relative sea level change in areas of complex tectonic motion, national geodetic vertical datums, near real‐time data for input to climatic diagnostic numerical models, calibration of satellite altimeter and scatterometer data, and the evaluation of the feasibility of producing synoptic mean sea level charts for the prediction of climatic trends, long‐range weather forecasts, and ocean processes.     

Study of apparent complexing capacities of trace heavy-metals in the Huanghe River Estuary

-By the electroanalysis method combining the complexation titrating technique with the investigation of ip-Ea* characteristic curves, this paper measures apparent complexing capacities of trace heavy-metals in water samples from the Huanghe River Estuary. The results show that the order of apparent complexing capacities of trace heavy-metals in the samples isCu>Cd>Pb,and that apparent complexing capacities of near shore sample are higher than those far from shore. The effect of ultraviolet irradiation on the dissociation of organic ligands and the adsorption effect of cell walls (cells being treated with acid and seawater respectively) are investigated. The reduction (on electrodes) mechanism of species of trace heavy-metals in seawater is approached by ip-Ea* characteristic curves.     

Estimation of chlorophyll-a concentration in the Zhujiang Estuary from SeaWiFS data

The chlorophyll-a concentration is generally overestimated for the southern China coastalwaters if the default algorithm of the SeaDAS is employed. An algorithm is developed for retrieval of chlorophyll-a concentration in the Zhujiang Estuary, Guangdong Province, China, by using simulated reflectance data. The simulated reflectance is calculated corresponding to the SeaWiFS wavelength bands, via a general model by inputting measured water components, i.e. , the suspended sediment, chlorophyll-a, and yellow substance (DOC) concentration data of 130 samples. Empirical relationships of the chlorophyll-a concentration to 240 different band combinations are investigated based on the simulated reflectance data, and the band combination, R_5R_6/R_3R_4, is found to be the optimum one for the development of an algorithm valid for the Zhujiang Estuary. This algorithm is then employed to determine the chlorophyll-a concentration from SeaWiFS data. The estimated concentrations have a better accuracy than those obtai     

The rule of sediment transport on the Nanhui tidal flat in the Changjiang Estuary

The Nanhui tidal flat is located in the area of slow current where the ebb currents from the Changjiang Estuaryand the Hangzhou Bay converge and the flood current from the sea diverges into the estuary and the bay. The flat extends seaward in tongue shape and has a wide and gentle surface with a marked difference of tidal levels on its two sides, which results in the sediment longitudinal transport on the flat. The water-sediment conditions are diverse at different locations. The velocity and sediment concentration in intertidal zone are higher during the flood tide than those during the ebb tide. The net sediment transport is landward, resulting in a large amount of deposition of sediments on the shoal. However, the ebb current is the dominant one in deep-water area where the net sediment transport is seaward. There exist two circulation systems in plane view on the shoal and in its adjacent deep-water area, which results in the sediment exchanges between the flat and channel and between the estuary an     

Relationship between suspended sediments from the Changjiang Estuary and the evolution of the embayed muddy coast of Zhejiang Province

South of Hangzhou Bay, Zhejiang Province, exhibits an embayed muddy coastline, with the muddy beaches of embayments extending continuously seaward.The source of sediments on this coast presents an interesting problem to marine geologists and geomorphologists .The total annual load of sediments from the rivers of Zhejiang is only 12×106t.These materials affect only the area near the river mouths. The paper showed that the sediment along the coast of Zhejiang mainly comes from the Changjiang Estuary through analysing the time and space variations of suspended sediment, the features of sediment and the sedimentary transport.The Changjiang River is the largest river system in China, its sediment to the sea amounting to 468×106t. The sediment during summer transports mainly eastward, and is affected by the water body with high temperature, salinity and transparency; the winter season is the period with high sediment concentration. The sediment of the Changjiang Estuary transports together with the longshor