In-stream fertilization is recognized as an effective rehabilitation strategy for increasing
fish production in nutrient poor streams. Past research has focused on timings and
concentration levels, and short term trials. Several alternative management schemes are
possible, but only a limited number have been field-tested. Sixteen nutrient replacement
schemes were developed based on an imitation of historical nutrient inputs such as
inorganic and organic components of fish carcass, leaves and background hydrology and
geology. Further, six schemes (3 schemes one year and 3 others the next year, see below)
were field tested over one year using nine artificial sub-alpine stream channels that
received natural background water from a nearby spawning channel and two Oncorhynchus
species, namely endangered coho salmon (O. kisutch) and steelhead trout (O. mykiss).
Schemes tested include: 1) summer inorganic fertilizer addition to reach 3 |ig/L SRP, 2)
organic fertilizer to reach 3 fig/L SRP, 3) no fertilizer addition, 4) organic fertilizer
addition in the summer to reach 3 ug/L SRP, 5) organic fertilizer in the fall to reach 3 (Xg/L
SRP and 6) no fertilizer addition. Background SRP conditions in schemes 1-3 were nil in
the summer and above phosphorous growth saturating conditions due to upstream salmon
carcass decomposition (SCD) in the fall, and in schemes 4-6, they were approximately
phosphorous growth saturating in the summer and fall (due to SCD that fall and the
previous fall). Schemes 1 and 6 were pseudo-replicates and their results were compared to
investigate the effects on the response variables of having a variable amount of inorganic
phosphorous (either from fertilizer or natural sources) available in the summer and
dissolved phosphorous from SCD available in the fall. Juvenile fish length, weight, fat
stores, and over-winter biomass were the primary response variables. Food web response to
phosphorous inputs including algal standing biomass, stream macroinvertebrate numbers
and biomass, and resident fatty acid profiles were investigated to elucidate the results. In
general, the benefits were not universal in terms of fish species. Steelhead trout benefited
the most from in-stream phosphorous augmentation. Year 1, steelhead trout over-winter
sizes under schemes 1 and 2 were significantly larger than under scheme 3 (p<0.0001).
Lipid levels were highest year one in steelhead trout under scheme 1 during the summer
and under scheme 2 and 3 after winter. Coho salmon size years 1 and 2 was significantly
larger after summer under treatments 1 and 4 than under the others conducted during the
same time period, but the size advantage did not persist over winter. Total lipid content in
coho salmon year 1 followed a similar trend. Year 2 after summer steelhead trout size
obtained under scheme 4 was larger than obtained under scheme 5 and 6, but like year 1
coho salmon, this advantage did not persist over winter. Scheme 1 and 6 the pseudo
replicates did not produce statistically similar results. Scheme 1 that received a higher input
concentration of SRP during the fall than scheme 6 produced more after winter biomass. As
well, in the summer coho salmon grew faster under scheme 6, than under scheme 1. This
can be attributed to SRP being available for a longer time period in scheme 6. These
results illustrate that future research should be conducted to investigate how concentration
and duration of phosphorous inputs as well as source and timing can be manipulated to
mimic historical stream phosphorous inputs and produce increased benefits to freshwater
resident juvenile salmonids. More tests on other schemes and species compositions could
lead to improved management practices and higher fish yields. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/17687 |
| Date | 05 1900 |
| Creators | Lawrie, Sarah Joanne |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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