habitat use and movement by brook trout (salvelinus fontinalis) and rainbow trout (oncorhynchus mykiss) in three tributaries of nipigon bay, lake superior
abstract
three streams were surveyed: dublin creek, macinnes creek, and little cypress river in northwestern ontario. knowledge of the physical habitat features of streams that are used by
brook trout (salvelinus fontinalis) and rainbow trout (oncorhynchus mykiss) is an
essential component of insuring that the habitat is protected from potential
impacts of land-use. in three small streams along the north shore of lake
superior i examined the characteristics of the stream habitat and length of
stream generally occupied by the brook trout and rainbow trout during the
summer, including brook trout in the presence and absence of rainbow trout in
the same stream. electrofishing, passive integrated transponder (pit) tagging,
minnow trapping, two-way weirs, and habitat manipulations were techniques
utilized in this study. catch rates and fish biomass were examined in relation to
associated characteristics of the stream habitat. the length of stream generally
occupied was extrapolated from the capture locations of pit-tagged brook trout
and rainbow trout. two-way weirs were placed at the top and bottom of a reach
within a section of one of the streams to monitor immigration and emigration of
brook trout and rainbow trout. brook trout catch-per-unit-effort (cue) using
baited minnow traps was more variable when traps were placed near low to high
amounts of structure in pools compared to areas with no structure. whereas,
rainbow trout cue using baited minnow traps was low for all categories, from no
structure to high amounts of structure. brook trout biomass for entire pools was
found to be significantly correlated with canopy closure over pools in the absence
of rainbow trout (r2 = 0.056, p = 0.037) and in the presence of rainbow trout (r2 =
0.059, p = 0.044). however, no significant correlations were found between
rainbow trout biomass for entire pools and various physical features that were
measured within pools. the majority of re-captured brook trout (20/23) and
rainbow trout (13/15) were less than two pools from the pool in which they were
originally captured one month earlier. primarily young-of-the-year (yoy) brook
trout and rainbow trout moved through the two-way weirs. the majority of
movement through the weirs was in the upstream direction (74 %) and the
majority of the downstream movement (66 %) occurred during the latter third of
the monitoring period (july and august). the results of this study may be
indicative of responses by salmonids to infertile conditions. the salmonid
biomass in streams that are relatively infertile may be at carrying capacity with
respect to the chemical characteristics or productivity of the water, but the
physical habitat is not likely used to its full potential when compared to more
productive waterbodies. therefore, habitat use and movement patterns exhibited
by salmonids inhabiting small infertile streams may be less common, but it may
also be the natural response by salmonids that encounter these conditions
across their geographic range.
collections
- retrospective theses [1604]