Fraser Estuary Research Articles

Tracking a Pollutant in the Lower Fraser River: A Computer Simulation

Abstract A one-dimensional numerical model of the tidal portion of the Fraser estuary has been adapted to simulate the path and residence time of contaminants released in any of the lower reaches of the river. A brief discussion of the model’s original development and purpose is followed by an assessment of its accuracy in predicting currents as compared to water surface elevations. Since the flow computations in this type of model are vertically and laterally integrated, they had to be corrected to represent transport in mid-channel. These correction factors were established by several time series and spot measurements along the river, taking into account the local topography. The results were verified by tracking surface floats during three representative discharges.

Juvenile salmonid use of habitats altered by a coal port in the Fraser river estuary, British Columbia

Juvenile chinook, chum, and pink used habitats modified by a coal port at the Fraser estuary in southwestern British Columbia, Canada. Recent construction for expansion of the port has obliterated feeding areas, invertebrate communities, and possibly herring habitat from the local production system. Further studies are required to document recolonization of disrupted habitats and to investigate if present food webs are similar to those before construction. Juvenile salmon may be diverted by causeways and terminals and this also requires study.

The distribution of alkalinity and pH in the Fraser estuary

Abstract The distribution of alkalinity, dissolved oxygen and pH were determined in the Fraser Estuary (B.C., Canada) under varying flow regimes. The alkalinity exhibited apparent non‐conservative behaviour at low salinities. A pH minimum is evident in the low salinity zone throughout the year and can be theoretically replicated using a two step mixing model without recourse to biological mechanisms.

Juvenile Salmon Residency in a Marsh Area of the Fraser River Estuary

Large numbers of juvenile chinook salmon (Oncorhynchus tshawytscha), chum salmon (O. keta), and pink salmon (O. gorbuscha) were present within tidal channels of a marsh area in the Fraser Estuary between March and June 1978. The tidal channels investigated dewatered at low tide, necessitating daily emigrations by juvenile salmon out of the channels. While pink fry emigrated from tidal channels at the early and middle stages of ebbing tides, most chum and chinook fry emigrated near the later stages of ebbing tides. Mark–recapture studies demonstrated that chinook and chum fry resided temporarily in the marsh prior to migrating into the Pacific Ocean and returned to the same channel on several tidal cycles. Pink fry were abundant in the channels, but appeared to be transient. Chinook and chum showed an increase in average length which was attributable to estuarine growth.Key words: chinook salmon, chum salmon, pink salmon, juvenile residency, marsh tidal channel, Fraser Estuary, estuary growth

THE UNCERTAIN QUEST FOR A MANAGEMENT STRATEGY IN THE FRASER ESTUARY

The growing pressure of competing demands and, in particular, a concern for the effects of development on the estuarine ecosystem, have led over the last decade, to an increasingly intensive quest for a management strategy in the Fraser Estuary. The progress that has been made in this quest is evaluated in terms of information flows and representation of interests in the bargaining processes that predominate in management. Progress has been substantial in opening up the bargaining to affected interests within governments but there has been less success in the case of non-governmental interests. This progress has, however, been severely limited by continuing inadequacies in the availability of needed information. In particular, the lack of information about cause-effect relationships constrains and frustrates the bargaining process. Phase I of the Federal-Provincial Fraser River Estuary Study partly recognized these weaknesses and made some innovative proposals for their resolution. The success of the ongo...

Association and Feeding Relationships Between Eogammarus confervicolus (Amphipoda, Gammaridae) and Benthic Algae on Sturgeon and Roberts Banks, Fraser River Estuary

Field and laboratory studies of the feeding and association of the gammarid amphipod Eogammarus confervicolus with algae and vascular plant debris were conducted on jetties, marshes, and sandflats at the Fraser River Estuary. Associations with Prasiola meridionalis (alga), and debris from Carex lyngbyei (vascular plant) were statistically significant. Vascular plant debris was more widespread in winter (January) compared to a summer survey (August). Laboratory growth rates and survival varied with food types, which were ranked (best to worst) as follows: Enteromorpha linza, Pylaiella littoralis, Porphyra spp., Navicula grevillei, Carex lyngbyei debris and Ulva lactuca. Assimilation efficiencies, measured with gravimetric and radioisotope techniques (14C) ranged from about 78% with P. littoralis to 62% with U. lactuca. Construction of jetties could increase the surface area for algal growth, but there would be no appreciable enhancement of primary production compared to a natural marsh/sandflat ecosystem.Key words: Crustacea, Eogammarus confervicolus, benthic algae, Fraser Estuary, intertidal distribution, feeding, ecological associations, engineering structures

Seasonal salinity changes in the Fraser River Estuary

The Fraser Estuary in British Columbia is characterized by a salt water wedge, which underlies the fresh surface water. The stage of the tide and the fresh water discharge in the Fraser River are the two primary factors influencing the maximum intrusion of the salt water wedge.A systematic set of measurements are presented, documenting the change in the position of the tip of the salt water wedge as a function of fresh water discharge. Tidal conditions did not affect the measurements, since all measurements were made at times when the stage of the tide was the same. The tip of the salt water wedge is shown to be displaced a distance of 22 km (13.8 mi) seawards, as the fresh water discharge increased from 850 to 9000 m3/s (30 000 to 317 000 ft3/s).Vigorous surface to bottom mixing was observed during large ebb flows. The mixing was sufficiently strong to break up the wedge over a large part of the estuary. A calculation is presented showing that this was due to the existence of a strong velocity shear between the saline bottom water and the fresh water surface flow.

SEDIMENT BUDGET OF THE LOWER FRASER RIVER

The Lower Fraser River, being continually developed for better navigation and larger port- facilities, is an area of active sedimentation. The dynamic processes influenced by river discharge, tides and winds are probably the most important factors in the transport and deposition of sediments in the estuary. The main part of the Fraser Estuary is vertically homogeneous (non-stratified) and the sediments are transported progressively seaward and are accumulated near the limit of net landward flow. The lower estuary is stratified and coarse sediments are trapped near the toe of the salt wedge while the fine sediments are carried seaward with the outflowing river water. The hydrometric and sediment survey of the lower Fraser River are described. Survey results are used in determining the sediment balance of the river reach. In the budget analysis, the river and estuary are divided into four consecutive reaches, the sediment discharges are subdivided to represent about 10 particle size ranges and the balance is then determined for each reach and particle size range. Conclusions are drawn with respect to the sediment transport and depositional characteristics, annual variations, and the agreement between the sediment entering the estuary and the sediment dredged.