2022 Early Hearing Detection & Intervention Virtual Conference

March 13 - 15, 2022

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6/06/2017 | 9:30 AM - 9:45 AM | HIGH FLOWS DECREASE FISH POPULATIONS IN THE CURRENT YEAR BUT INCREASE POPULATIONS THE FOLLOWING YEAR | 302C

HIGH FLOWS DECREASE FISH POPULATIONS IN THE CURRENT YEAR BUT INCREASE POPULATIONS THE FOLLOWING YEAR

Hydrology is thought to exert strong control on lotic fish populations, but relationships between specific flow metrics and actual abundances only rarely have been quantified. We used long-term fish count data to test specific hypotheses of flow ecology relationships in two contrasting river systems: (1) the highly biodiverse Etowah River in Georgia, USA, and (2) a set of streams in Nevada, USA that support Lahontan cutthroat trout (Onchorhynchus clarkii henshawii). We used autoregressive population models incorporating density dependence to test the effects of high flows on population growth rates. We found that for cutthroat trout and for 9 of 12 shoal-dwelling species in the Etowah, high flows reduced growth rates in the current year (i.e., reduced abundance relative to the prior year), but increased growth rates in the succeeding year. We argue that the most likely explanation for this pattern is scouring that causes immediate mortality but increases primary and secondary productivity, thereby increasing recruitment to adult stage. We also illustrate the benefits of modeling growth rate rather than repeated measures of abundance as a response variable.

C02 Fish and Other Aquatic Vertebrates
C15 Population Ecology
S31 Moving forward in flow ecology: identifying and testing key hypotheses & C17 Bioassessment

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Presenters/Authors

Seth Wenger (), University of Georgia, sethwenger@fastmail.fm;