Numerous lines of evidence suggested that white sturgeon use the dredge areas as a transit corridor and are not directly affected by the dredging activity. Data from the combined studies showed a 77-93% decrease in invertebrate abundance (mainly chironomids) due to dredging and that re-colonization occurred in 2-9 month after dredging. Eulachon prey were examined using egg and larvae sampling using nets coupled with hydroacoustics to look the distribution of aggregations of spawners. White sturgeon use of dredged areas and other habitat was followed using radio tracking techniques, tagging, and stomach content analysis. The benthos part of the studies involved a similar design called a “before – after – control – impact” layout which, along with other lines of evidence allowed for comparison of findings between and among projects and it allowed for replicated treatments to be statistically tested. Sand for sale is typically removed from “borrow pits” from which sand is removed from an upriver site and replaced with sand from the navigation channels, thus maintaining sand grade at the upriver sites. Dredging is used to remove sand for sale in the construction industry and to maintain water depths for shipping traffic. In the early 2000’s Limnotek was commissioned by the Fraser River Port Authority to conduct a series of studies to examine the effect of sand transfer pit and other dredging operations on fish, white sturgeon, and benthos in the sand reach of the lower Fraser River.
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