NOAA 'Omics Seminar Series (July 19, 2023): Pairing eDNA with acoustic surveys for Atlantic herring

This seminar is part of the NOAA 'Omics Seminar Series, which takes place on the third Wednesday of every month at 12pm ET / 9am PT. 'Omics describes a suite of cutting-edge tools used to analyze DNA, RNA, proteins, or metabolites.
Date: July 19, 2023
Title: Pairing eDNA with an inshore acoustic survey for Atlantic herring (Clupea harengus): challenges and some promising findings
Presenter: Graham Sherwood
Abstract: Environmental DNA (eDNA) is becoming a promising tool for assessing abundance and biomass of organisms in marine settings. While many studies show that eDNA can be correlated with traditional survey methods, issues related to catchability and/or detectability of target species and stability of eDNA may hamper the development of more robust correlations between the two measures of abundance. Our current work builds on the results of a large-scale fisheries acoustic survey in coastal Maine, where Atlantic herring have previously been identified with a high degree of confidence, due to acoustic characteristics of schools and unique spawning behavior. The goal of this study was to compare acoustic estimates of herring abundance (‘known’ schools) with eDNA concentrations to provide a robust test of the eDNA method for assessing fish abundance in the open ocean. Unfortunately, the northeast US herring stock complex underwent major declines over the period leading up to our field research making it difficult to observe spawning schools in the way that they have been in the past. Nonetheless, herring eDNA was detected in the study region and matched some patterns of acoustic biomass. Interestingly, our study showed a prominent depth dependency with herring eDNA being much more prevalent on the bottom (which is where spawning occurs). We also found that eDNA fragment size mattered; herring eDNA was much more detectable using primers for a shorter fragment (150 BP) compared to a longer fragment (792 BP). We will discuss how this information may be useful for making abundance inferences at different spatial and temporal scales. While this study was intended to pair eDNA sampling with an acoustic survey to ‘validate’ eDNA, we will also discuss how eDNA may prove very useful for ground-truthing acoustic signals which often can be ambiguous.