Abstracts - Dissolved Oxygen Monitoring and Substrate Quality |
Nechako River Substrate Quality and Composition (M89-7)
Prepared by Ken Rood, Ken Rood & Associates June 1998
Substrate quality, often measured as the proportion of fine sediments in stream gravels,
is associated with spawning success, incubation success, rearing habitat quality and
invertebrate production. Fine sediments are particularly detrimental to successful
salmonid reproduction. Numerous laboratory and field studies have described inverse
relationships between the proportion of fines (above some critical level) and egg survival
or fry emergence. It is generally assumed that increased mortality is caused by lower
intragravel velocities, lower permeabilities, lower dissolved oxygen and entombment of
eggs, alevins and fry by fine sediments.
ivIn regulated rivers it is often assumed that substrate quality deteriorates following
regulation (Reiser et al. 1985). Typically, regulation reduces peak flows, lowering
sediment transport capacity for gravel and larger particles. Lack of gravel movement, or
bed immobility, is associated with accumulation of fine sediments and deterioration of
substrate quality.
The Nechako Fisheries Conservation Program (NFCP) Technical Committee is responsible
for monitoring gravel quality along the Nechako River. This committee, through the
Department of Fisheries and Oceans, has contracted with K. Rood & Associates to
develop a substrate quality sampling project for the Nechako River. This was accomplished
by:
- Reviewing substrate sampling methodologies, discussing the advantages and disadvantages
of each method;
- Summarizing existing data on substrate quality and composition in the Nechako River;
- Conducting a one-day expert workshop to review appropriate gravel quality sampling
projects;
- Summarizing results of the workshop and developing an appropriate sampling strategy for
the Nechako River; and
- Completing a pilot sampling project for gravel quality along the Nechako River,
analysing the samples and presenting the results.
A background report reviewing substrate sampling techniques was circulated to workshop
participants prior to the meeting on August 1, 1989. Material from the background report
was incorporated into this report which critically reviews substrate sampling
methodologies, summarizes the existing database on the Nechako River, summarizes workshop
discussions, recommends a sampling strategy for substrate quality and presents the results
of a pilot sampling on the Nechako River.
