Topeka Shiners Surveyed After 2012 Drought
By Aleshia Kinney
Columbia Ecological Services Field Office
After one of the worst droughts in the state’s history struck Iowa, in 2011 and 2012, biologists from the Rock Island Field Office conducted surveys, in July 2013, to help determine the effect of the drought on the endangered Topeka shiner.
During the 2012 summer's drought, miles of streams designated as critical habitat for the Topeka shiner went completely dry. Entire watersheds became so devoid of water that not even intermittent puddles existed. Most tributary streams were completely dry, leaving only the main rivers, nearby gravel pits and seemingly random pools (e.g., under bridges and plunge pools below structures) as possible sources of available water.
Since 2002 the Rock Island Field Office has restored more than 50 oxbows within the North Raccoon River watershed to provide habitat for Topeka shiners, and we know that most support fish. During the drought, almost all of the restored oxbows went dry.
The weather cycle returned to more normal conditions in 2013 with a few precipitation events causing floods. As a result of this flooding, the restored oxbows reconnected with their streams. This prompted biologists to sample some of these oxbows that were known to contain Topeka shiners to find out three things: what fish species are the first to recolonize these systems and associated off-channel habitats, whether Topeka shiners are among the early recolonizing species, and if Topeka shiners show up, at what density are they represented.
The oxbows that were sampled were those that were sampled in 2009 during an intense sampling effort that provided baseline fish population data for six restored oxbows. Along with resampling those six oxbows, any restored oxbows nearby were also sampled.
Over the course of three days, a total of 15 restored oxbows were sampled and Topeka shiners were found in 10 of them. The 10 oxbows where Topeka shiners were found were either very near the mouth of the North Raccoon River or near a gravel pit, and that is not believed to be a coincidence. The gravel pits, because of their depth and ability to hold water during extended dry periods, may provide refuges during drought. It is likely that spring flooding dispersed fish from these pits into the river main channel and adjacent floodplain, including into our restored oxbow ponds.
Biologists were impressed and heartened that, following the first flood after a drought, they were able to find Topeka shiners in 70 percent of the off-channel areas that were checked. However, numbers appear to be substantially down. In 2009, 10 oxbows were sampled (including the same ones sampled in 2013) and 754 Topeka shiners were found, whereas, in 2013 15 oxbows were sampled and 80 Topeka shiners were found (17 males and 63 females).
The diversity and numbers of other fish using these oxbows is impressive, especially considering they and adjacent tributaries were dry last summer. In three days of sampling, over 15,000 fish of 24 different species were collected, and that is not counting all of the young of the year spawn! The oxbows were also full of turtles, amphibians, insects and crayfish.
Information collected from this study will help guide future management decisions regarding population status and recovery actions. Climate models predict that extreme weather events will become more frequent. Obtaining population density data after the drought of 2012 and comparing it to baseline population estimates from the same place during normal climate years will help researchers and managers evaluate the impact of the 2012 drought on an already imperiled species. Results from this study will be used to guide and focus restoration efforts in years to come.