The Majority of Fish Species were Detected with All Materials
For all materials, we assigned 8,822,884 sequence reads to 71 fish taxa (Table 2). Of the 50 species known to inhabit the mesocosm, 37 (74%) were detected through passive eDNA. The additional 34 species detected include known feed taxa, fish found in local intake waters, and fish occupying tanks within the same facility and within the same water system. The number of species detected differed between materials (Fig.4; F=21.69, df=11, p < 0.01), with cotton, hemp and nylon detecting the fewest number of fish species on average. However, all materials detected a comparable number of species to the conventionally filtered eDNA samples.
The median number of fish species detected by material was 27 (filtered eDNA; range = 19-32), 29 (cellulose; 19-33), 31 (chitosan - 1%; 17, 36), 31 (chitosan - 3%; 23, 37), 29 (espun; 22, 31), 26.5 (espun with chitosan; 21, 36), 19.5 (cotton; 11, 28), 24 (hemp; 14, 30), 24 (nylon bags; 18, 29), 27 (sponge – active carbon; 13, 37) and 29 (sponge – nitrate; 21, 34). The number of species detected did not differ with submersion time for any of the nine trialled materials (Fig. 5; F = 0.68 for submersion time * material, df = 9, p = 0.72).