I attended the 2020 Virginia Sea Grant Graduate Symposium on February 27 – 28 and presented a poster of my OSCAR funded research conducted under Dr. Kim de Mutsert and the Potomac Environmental Research and Education Center.
I have been researching the differences in spawning population size of river herring, the collective name of alewife and blueback herring, in three tributaries of the Potomac River: Cameron Run, Pohick Creek, and Accotink Creek. Each of these creeks experience different amounts of human activity. Cameron Run is in a heavily urbanized area and receives treated wastewater discharge, Pohick Creek receives treated wastewater discharge and is in a moderately urbanized area, and Accotink Creek does not receive wastewater discharge. To determine the abundance of river herring in each tributary, I have been utilizing field collections and surveys of ichthyoplankton (larval fish) and adult river herring in 2019 along with statistical analysis of the data collected from 2015-2019. I have also been looking at water quality parameters – dissolved oxygen, pH, water temperature, and specific conductivity (a measure related to salinity) – to gain a better idea of what might be causing differences in spawning population sizes.
While my project is still ongoing, at this conference I presented some initial results from the 2019 populations sizes and correlations with water quality parameters. I found that Pohick Creek likely had the largest spawning population size of the three tributaries in 2019, as indicated by the high CPUE (catch per unit effort, or number of fish caught in a given time period) of both larval and adult river herring in Pohick Creek. Cameron Run likely had the second largest population size of the three tributaries, as indicated by the CPUE of both larval and adult river herring.
In addition, there was a significant linear correlation between water temperature and larval CPUE; as water temperature increased, the amount of larval CPUE increased. This is interesting, because treated wastewater discharge can often be warmer than the water temperature of a normal tributary, my initial findings could mean that river herring, specifically blueback herring, favor the creeks with treated wastewater discharge, Pohick and Cameron Run. The next step of my project on river herring is using the 2019 data to analyze water quality variables and their non-linear relationships to population size, in order to account for non-linearity common in ecology.