New progress has been made in analyzing the spatial and temporal differences of estuarine fish communities based on environmental DNA technology

Recently, the investigation and assessment team of the South China Sea Fishery Resources Investigation and Assessment Team of the South China Sea Fisheries Research Institute of the Chinese Academy of Fishery Sciences and the South China Sea Rare and Endangered Animals Protection Team have made new progress
in using environmental DNA (eDNA) technology to analyze the diversity of fish in estuaries and the spatial and temporal differences of fish communities 。 The paper is titled "Comparison of environmental DNA metabarcoding and bottom trawling for detecting seasonal fish communities and habitat preference in a highly disturbed estuary" The title was published in
the international journal Ecological Indicators (JCR Q1).
Jiang Peiwen is the first author, and Chen Zuozhi and Li Min are the corresponding authors
.

Estuarine fish are an important part of estuarine ecosystems, and monitoring of fish diversity and community structure is becoming increasingly important
in the context of increasing human activities.
However, the estuarine sea area has shallow water depth, many navigation routes and turbid water bodies, etc.
, and some existing investigation methods are often limited
.
Based on the previously established eDNA enrichment protocol in estuarine waters (DOI: 10.
24272/j.
issn.
2095-8137.
2021.
331; DOI: 10.
12131/20210304) and the eDNA meteric barcode database of background fish in the Pearl River Estuary (DOI: 10.
12131/20210210), the research team used eDNA metabarcoding to study the fish species composition, composition and aquaniche in the Pearl River Estuary The spatiotemporal differences of communities and their relationship with environmental factors were compared
with bottom trawl survey methods.

The study conducted simultaneous bottom trawling, water sampling and environmental factor measurements
at 10 monitoring sites in the Pearl River estuary in autumn and spring.
After filtration, eDNA was extracted from the water samples, and MiFish-U/E primers were used to amplify, build, sequence and OTU annotate the mitochondrial 12SrRNA gene (about 172 bp), and the fish species composition
was obtained by database comparison.
The main results are: 1.
The eDNA method significantly detected more species than bottom trawl at each sampling point, with a total of 214 fish species detected by eDNA (90 bottom trawl species), and there was a significant correlation
between the relative abundance of eDNA detected species and fish species abundance/biomass.
The analysis of fish ecological habits showed that eDNA could detect small fish that were missed due to the size limitation of traditional fishing nets, which made the ecological characteristics of fish communities more complete.
2.
Both methods detected seasonal changes in fish species, i.
e.
there was a significant difference between spring and autumn fish communities, and the eDNA method detected greater significance than bottom trawling
.
3.
eDNA, like bottom trawling, revealed that differences in fish community composition increased
significantly with increasing geographical distance.
The above results show that eDNA metabarcoding can be used as an important supplementary means or even an alternative method to monitor seasonal changes and spatial distribution changes of fish communities in estuarine ecosystems, especially when traditional investigation methods are difficult, and improve the ability to assess the structure of fish communities in estuarine ecosystems, which has good application prospects
in the field of fishery research and ecological environment monitoring.

Schematic diagram of sampling sites in the Pearl River Estuary in the study area

Comparison of fish species composition based on eDNA and bottom trawl