Effects of hypoxia on consumption, growth, and RNA:DNA ratios of young Yellow Perch

As in various freshwater and coastal marine ecosystems worldwide, seasonal bottom water hypoxia is a recurring
phenomenon in Lake Erie’s central basin. While bottom hypoxia can strongly affect sessile benthic animals, its effects
on mobile organisms such as fish are less understood. We evaluated the potential for bottom hypoxia to affect the
growth rates of yellow perch Perca flavescens, a species of ecological and economic importance in the lake. To this end,
we (1) conducted laboratory experiments to quantify the effects of reduced dissolved oxygen on consumption, somatic
growth, and RNA:DNA ratios (an index of short-term growth) of young yellow perch and (2) explored the effects
of bottom hypoxia on young yellow perch growth in Lake Erie’s central basin by collecting individuals in hypoxic and normoxic regions of the lake and quantifying their RNA:DNA ratios. Yellow perch consumption and growth in
our experiments declined under hypoxic conditions (≤2 mg O2/L). While yellow perch RNA:DNA ratios responded
strongly to experimental temperature, nucleic acid ratios were not significantly affected by dissolved oxygen or feeding
ration. We did, however, observe a positive correlation between yellow perch growth and RNA:DNA ratios at low
temperatures (11◦C). The nucleic acid ratios of yellow perch collected in Lake Erie varied spatiotemporally, but
their patterns were not consistent with hypoxia. In short, while yellow perch consumption and growth rates respond
directly and negatively to low oxygen conditions, these responses are not necessarily reflected in RNA:DNA ratios.
Moreover, in central Lake Erie, where yellow perch can behaviorally avoid hypoxic areas, the RNA:DNA ratios of
yellow perch do not respond strongly to bottom hypoxia. Thus, this study suggests that there is no strong negative
effect of bottom hypoxia on the growth of young yellow perch in Lake Erie.