PS 77-183
Marine fish surveys using environmental DNA
Given the current crisis of biodiversity loss, a quantitative biological assessment in natural ecosystems has become a matter of urgency. In particular, there are serious concerns regarding changes in fish communities in marine ecosystems because such changes would have significant impacts on ecosystem processes and the sustainability of fisheries. Recently, a research method for aquatic vertebrate assessment using environmental DNA (eDNA) has been developed and applied extensively in inland waters; however, only a few applications in the marine environment have been reported. Here, we conducted a fish survey in a marine coastal habitat using the eDNA technique.
To evaluate the effect of temperature on the amount of DNA, eDNA was recovered from tanks in which juveniles of jack mackerel (Trachurus japonicus) were maintained under three temperature conditions. An analysis of eDNA was also conducted in tanks containing fish at four density levels. Subsequently, the fish community in the natural habitat was surveyed by SCUBA divers followed by eDNA analysis of sampled water. Nine surveys were performed along the coast of Maizuru Bay, Japan, from October 2012 to February 2013. TaqMan real-time PCR was performed targeting five fish species, and the results were compared with those of the visual census.
Results/Conclusions
eDNA was detected in all tanks containing jack mackerel. The amount of eDNA was not significantly different among the three temperature conditions examined (12, 20, or 28°C). This finding is essential knowledge for the establishment of a quantitative system in the field. The eDNA concentration in the tanks with different fish densities (0, 3, 10, or 30 individuals of fish in a 500-liter tank) did not reflect the fish density in the tanks due to the high variation in eDNA in the low density tanks. The underwater visual census recorded a total of approximately 3,000 fish belonging 36 species. The eDNA density/detection frequency corresponded reasonably well with the fish abundance recorded in the underwater visual census for jack mackerel, wrasse (Halichoeres tenuispinnis), and black sea bream (Acanthopagrus schlegelii). In contrast, the eDNA analysis detected two species that were not observed in the visual census, namely, Japanese anchovy (Engraulis japonicus) and temperate seabass (Lateolabrax japonicus). These two species were, however, recorded in surveys undertaken in previous years. Although certain problems need to be resolved, the eDNA method represents a promising tool for fish surveys in marine ecosystems.