Biocomplexity at North Temperate Lakes LTER; Whole Lake Manipulations: Rainbow Smelt Removal 2001 - 2009

Rainbow smelt (Osmerus mordax) are a harmful invasive species in lakes of northern
Wisconsin. Smelt were first detected in Sparkling Lake, Vilas county, WI in 1980 and their
population has since increased dramatically. We attempt to remove rainbow smelt from
Sparkling Lake through a combined strategy of harvest and predation. If successful, such a
strategy might be employed to restore other Wisconsin lakes invaded by smelt to a more
natural species assemblage without resorting to piscicides. The data sets presented here
report the harvest component of smelt removal. An assessment of the rainbow smelt
population, supplementing annual LTER data, was performed during the late summer of 2001.
The spring removal effort began in 2002 at ice out using multiple gear types. In 2002, the
removal effort also continued from mid to late summer using horizontal gill nets. However,
from 2003-2009 we took advantage of smelt spawning behavior and our efforts were condensed
to a spring removal at ice-off and we utilized only fyke nets. The total weight of each
catch was recorded and length-weights as well as sex ratios were documented for a subset of
the catch from each removal event. The removal effort resulted in the removal of the
majority of the adult population multiple times. However, smelt are a robust species and the
population continuously rebounded from large removal years. As a result, catches have
fluctuated from 16kg to nearly two tons. We have observed an overall reduction in fish size
and an increase in the proportion of males to females. Sampling Frequency: annually