Spatio-seasonal patterns of fish diversity,Haizhou Bay,China

Spatial-seasonal patterns in fish diversity in Haizhou Bay were studied based on stratified random surveys conducted in 2011.Principal component analysis was conducted to distinguish different diversity components,and the relationships among 11 diversity indices were explored.Generalized additive models were constructed to examine the environmental effects on diversity indices.Eleven diversity indices were grouped into four components:(1) species numbers and richness,(2) heterogeneous indices,(3) evenness,and(4) taxonomic relatedness.The results show that diversity indices among different components are complementary.Spatial patterns show that fish diversity was higher in coastal areas,which was affected by complex bottom topography and spatial variations of water mass and currents.Seasonal trends could be best explained by the seasonal migration of dominant fish species.Fish diversity generally declined with increasing depth except for taxonomic distinctness,which increased with latitude.In addition,bottom temperature had a significant effect on diversity index of richness.These results indicate that substrate complexity and environmental gradients had important influences on fish diversity patterns,and these factors should be considered in fishery resource management and conservation.Furthermore,diversity in two functional groups(demersal/pelagic fishes) was influenced by different environmental factors.Therefore,the distribution of individual species or new indicators in diversity should be applied to examine spatio-seasonal variations in fish diversity.

Effects of sampling strategies and DNA extraction methods on eDNA metabarcoding: A case study of estuarine fish diversity monitoring

Environmental DNA(eDNA)integrated with metabarcoding is a promising and powerful tool for species composition and biodiversity assessment in aquatic ecosystems and is increasingly applied to evaluate fish diversity.To date,however,no standardized eDNA-based protocol has been established to monitor fish diversity.In this study,we investigated and compared two filtration methods and three DNA extraction methods using three filtration water volumes to determine a suitable approach for eDNA-based fish diversity monitoring in the Pearl River Estuary(PRE),a highly anthropogenically disturbed estuarine ecosystem.Compared to filtration-based precipitation,direct filtration was a more suitable method for eDNA metabarcoding in the PRE.The combined use of DNeasy Blood and Tissue Kit(BT)and traditional phenol/chloroform(PC)extraction produced higher DNA yields,amplicon sequence variants(ASVs),and Shannon diversity indices,and generated more homogeneous and consistent community composition among replicates.Compared to the other combined protocols,the PC and BT methods obtained better species detection,higher fish diversity,and greater consistency for the filtration water volumes of 1000 and 2000 mL,respectively.All eDNA metabarcoding protocols were more sensitive than bottom trawling in the PRE fish surveys and combining two techniques yielded greater taxonomic diversity.Furthermore,combining traditional methods with eDNA analysis enhanced accuracy.These results indicate that methodological decisions related to eDNA metabarcoding should be made with caution for fish community monitoring in estuarine ecosystems.

Fish species diversity in the Huanghe Estuary

This paper lists 50 fish specs in the Huanghe Estuary, which belong to 9 orders, 22 families and 37 genera. The paper describes the seasonal distributions of these fish species and the succession of the important fish species during the past 50 a. The authors discuss the main factors that have resulted in the changes in fish species diversity and the fishery resources. These include the overexploitation of the fishery and the sharp reduction in the fresh water discharges from the Huanghe River.

Revealing an Invasion Risk of Fish Species in Qingdao Underwater World by Environmental DNA Metabarcoding

Environmental DNA(eDNA)metabarcoding has emerged as a potentially powerful tool to monitor invasive fish species.As an alternative(or complementary)tool for biodiversity monitoring,e DNA metabarcoding had been used to detect species in aquariums,which represents an important transit avenue for introducing non-indigenous species with high population densities.In this study,eDNA metabarcoding as well as morphological characterization were used to reveal the diversity of non-indigenous species in a large aquarium at Qingdao Underwater World.Environmental DNA metabarcoding of 14 water samples at five locations from the Big Water Tank detected 24 non-indigenous species and four putative non-indigenous operational taxonomic units(OTUs).In contrast,only 20 non-indigenous species were observed by morphological characterization.Some species undetected by morphological characterization,such as Oreochromis niloticus(Linnaeus,1758),are highly adaptable to various environments and/or have invaded preferred regions where they threaten native aquatic species.eDNA metabarcoding also detected seven local fishes that were not identified by morphological characterization.However,analysis of OTU diversity among stations and sample replications revealed that eDNA varied within and/or between stations.Increasing sampling effort as well as negative controls are required to increase the detection rate of species and to eliminate false-positive OTUs.