Proceedings - Teaching and Learning Centre - Simon Fraser ...

Fraser River Action Plan 3rd Research Workshop
techniques were all used to improve the capture success of mature peamouth chub. The greatest numbers of
peamouth were caught in eddy pools along the margins of the river using sinking, monofilament gillnets (50 mm
mesh). Despite substantial sampling effort, numbers of mature male/female fish captured in the exposure zones
were again limited. Capture success was strongly hindered by high, turbid water levels and large amounts of
suspended debris which fouled the gillnets.
Conclusions
Overall, there were few differences in whole organism and physiological parameters between fish collected from
the reference and near-field zones. Limited sample sizes for mature male and female fish made it difficult to
confidently compare characteristics between zones. However, a graphical approach comparing the spatial
position of individual near-field fish relative to the 95% confidence ellipse of reference fish did not show
substantial deviations in the parameters of exposed chub. As in the fall survey, immature peamouth chub from
the near-field zones had induced EROD activity (1.5- to 4.1-fold) relative to reference fish, indicating exposure
to mill effluent. No steroid hormone differences (circulating levels or in vitro production) were observed
between reference and exposed fish. Comparisons between spring and fall reference fish indicated that sexually
mature fish collected in the spring were significantly larger and older than fish collected during the fall survey.
These results further supported the hypothesis that chub collected during the fall were probably borderline in
terms of size and age of maturity.
As in the fall, instream concentrations of conductivity, chloride, sodium and suphate were predictably higher
downstream of the mill diffusers during the spring survey. Chloride data indicated that effluent concentrations
were approximately 0.08-0.6% downstream of mill A and approximately 0.03-0.4% downstream of mill B. The
chemistry data, along with MFO data, indicated that the fish sampled during the spring survey were exposed to
mill effluent.
Concurrent to the field surveys, laboratory effluent exposure tests were conducted to determine whether effluents
from the Fraser River mills (Prince George and Quesnel mills) were capable of inducing MFO activity in
exposed rainbow trout. Fish were exposed to 100% effluent for a total of four days. Hepatic EROD activity in
exposed trout were induced 6.7-fold with mill A effluent, 8-fold with mill B effluent, 14.5-fold with mill C
effluent and 3.1-fold with mill D effluent relative to reference fish.
Similar exposure tests were conducted in the field at the mill A site using peamouth chub from the reference
zone. Male and female chub were exposed to river water (collected upstream of diffuser) or 50% whole effluent
from mill A for five days. After the exposure period MFO activity and circulating levels of testosterone were
measured. Unfortunately, problems related to fish survival occurred (fungal infection) affecting the sample size,
exposure time and power of the test. No differences were observed in EROD activity or plasma concentrations
of testosterone between exposed and reference fish. Confidence in the results were influenced by high withintreatment
variability and reduced exposure time. However, the on-site test represented a useful approach for
assessing the potential of effluents to affect resident fish species, especially in situations where the capture
success of exposed fish is poor.
Despite the limited field data, there was evidence which suggested that effluent from mills A and B were capable
of eliciting physiological responses in laboratory and resident fish species (immature chub). However, the
success of using peamouth chub for monitoring the upper Fraser River is uncertain. First, peamouth chub is
larger than many cyprinid/cottid species and its capacity for large-scale movement is unknown. Although likely
to be less mobile relative to larger species such as mountain whitefish or squawfish, the degree of mobility of
peamouth chub needs to be assessed. Second, the success of using peamouth chub as a sentinel monitoring
species is strongly influenced by the ability to capture mature chub within the near-field zones. Unless capture
success improves, use of peamouth chub as a sentinel species will be restricted to far-field zones, or mills located
further downstream of Prince George where peamouth chub are more abundant.
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