Analysis of a coastal North Sea fish community: Comparison of aquatic environmental DNA concentrations to fish catches

Analyses of environmental DNA have the potential to become an integrated tool infish research and management. We performed a pilot study during the spring migration of fishes from the North Sea into the Wadden Sea and present comparativeresults from daily fyke catches (20 mm mesh) in the Marsdiep tidal inlet on two locations and results from weekly fish eDNA analyses on three locations, all within 2 kmdistance.Fish catches did not differ significantly between the two locations, whereas theeDNA composition showed a significant location effect. However, when eDNA analysis was restricted to species that were caught with the fykes, differences amonglocations became insignificant. Over ten weeks, from late April to early July, presence–absence calls of fishes based on weekly eDNA sampling significantly agreedwith calls based on seven days of fyke fishing 1 km westwards. Fish eDNA compositions differed significantly among sample days and months but not between tides.Over the season, patterns in eDNA concentration (12S rRNA gene copies/L) inferredfrom quantitative PCR and Illumina HiSeq community composition corresponded topatterns in wet mass for the eight most abundant fish species in the fyke (>6 weekspresent) despite changes in water temperature and changes in fish size class. Smallsandeel and gobies, which are important prey for large fishes and birds, were typically missed with the fyke but contributed up to 25%–40% of the fish eDNA depending on the sample location.