<p>Offshore spring zooplankton biomass
in northern Lake Michigan is currently dominated by calanoid copepods and lacking
in cyclopoid copepod biomass, which is a preferred prey type for larval
coregonids in the Great Lakes. As such, we survey nearshore beach zooplankton
to determine if nearshore environments are following offshore trends and
describe larval coregonid diets and prey selectivity during spring 2015-2019. Copepod
nauplii and calanoid copepods were the most abundant prey types in the
nearshore beach environments, and although larvae did not consume copepod
nauplii, larvae did incorporate substantial later life stages of calanoid
copepods into their diet. Additionally, larvae exhibited positive selectivity
for both calanoid and cyclopoid copepods. High consumption of and selectivity
for calanoid copepods in small larval coregonids is not a common observation in
the Great Lakes, as previous diets of small larvae have been comprised of
mainly cyclopoid copepods and cladocerans. Future research into the foraging
costs and nutritional benefits of larval diets with differing ratios of cyclopoid
to calanoid biomass should be investigated to understand the potential impacts
of differing diets on larval growth and survival. </p>
<p> Many
species of larval fish in Lakes Michigan and Huron experience a prolonged
offshore pelagic stage as during early life, but environmental conditions in
offshore environments have changed in the past quarter century. Under current
conditions, offshore habitats may be unsuitable for larval fish, given recent increases
in offshore water clarity and decreases in offshore primary production and
zooplankton biomass in both lakes. To evaluate habitat suitability for larval
fish, we characterized ambient environmental conditions using data streams from
multiple high frequency sensors to
develop growth rate potential models as an index of habitat quality of
nearshore-offshore transects in central Lake Michigan and southern Lake Huron.
Since temperature regimes differ throughout the summer, we compare habitat
quality throughout the summer for larval yellow perch and smelt, two species
that have demonstrated offshore pelagic stages as larvae. Early in the summer,
high habitat quality was concentrated nearshore, while later in the summer high
habitat quality was concentrated near the thermocline, at depths where larvae
are unlikely to inhabit due to limited swimming ability. The offshore (15-60 m
depth contour) surface waters of both lakes provide poor habitat quality in May
and July, although the surface waters of transects collected during June in
southern Lake Huron provided high quality habitat at all distances from shore. These
results suggest that offshore advection and prolonged offshore pelagic stage
duration during early life of fish could contribute to decreased growth and
survival of larval fish in lakes Michigan and Huron. </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/17182511 |
| Date | 18 December 2021 |
| Creators | Marissa Lynn Cubbage (11824208) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/IMPACTS_OF_ZOOPLANKTON_ABUNDANCE_AND_COMMUNITY_COMPOSITION_ON_LARVAL_FISH_HABITAT_QUALITY_AND_LARVAL_COREGONID_DIETS/17182511 |
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