Jin Xian-shi

Biomass size spectra of net plankton in the adjacent area near the Yangtze River Estuary in spring

Abstract Based on data from survey carried out in spring 2005, the biomass size spectra of net plankton were explored in the adjacent sea of Yangtze River Estuary. Results revealed an approximately continuous size distribution of plankton individuals, from phytoplankton (5–250 μm cell −1 in equivalent sphere diameter (ESD), 15 pg–146 ng C cell −1 ) to zooplankton (120 μm–2 cm ESD, 115 ng–7.5 mg C ind −1 ). The normalized spectra (carbon scale) were linear with slope ranged from –0.889 to –0.445, and intercept ranged from 12.866 to 16.863 (all stations together, slope = –0.606, intercept = 19.448), indicating strong deviations from the ideal value (slope = –1.22) of a steady pelagic ecosystem. Correlation analysis presented that intercept and regression coefficient of net plankton size spectra had significant relationship with plankton biomass size diversity.

Variation in feeding ecology within the fish community in the north Yellow Sea

Our objective was to evaluate ecosystem status before and after fishery enhancement.We analyzed the feeding habits,food consumption,and trophic level of the species constituting 90% of total biomass in bottom trawl surveys conducted in May and August of 2010.We compared the traits of the five dominant species(by total biomass) with those collected in 1985 and 2000.In addition,we evaluated decadal-scale variation in the mean TL of the fish community in the north Yellow Sea. The fish community in the north Yellow Sea was dominated by nine species,though these differed between May and August.The most dominant species in May included small yellow croaker Pseudosciaena polyactis,elongate eelpout Enchelyopus elongates,half-fin anchovy Setipinna taty,angler Lophius litulon,pointhead plaice Cleisthenes herzensteini,Pacific cod Gadus macrocephalus,and sea perch Lateolabrax japonicus.Conversely,in August the fishery was dominated by anchovy Engraulis japonicus,sea snail Liparis tanakae,small yellow croaker,elongate eelpout,and Pacific cod.Thus,the assemblage in May was characterized by a lack of nektivores,a decrease in the proportion of generalist predators,and an increase in the proportion of zooplanktivores relative to August.The mean trophic level of the fish community was 3.75 in May and 3.57 in August. The primary prey groups included euphausiids,copepods,hyperiid amphipods,crustacea larva,shrimps,ophiuroidea,bivalvia,polychaeta,and other fish species.We estimated the fish community consumed 0.5 million tons and 19.6 million tons of these prey items in May and August,respectively.Fish and shrimp were the dominant prey groups in May,accounting for 46.9% and 39.2% of the total food consumption,respectively.Similarly,fish,shrimp,and zooplankton were the dominant prey groups in August,accounting for 33.9%,31.4%,and 30.8% of the total food consumed,respectively.The primary prey species were Crangon affinis,Eualus sinensis,Euphausia pacifica,small yellow croaker,Johnius belengerii,and Ophiura sarsii in May.Consumption of these species equaled 0.3 million tons,accounting for 65% of the total food consumption.The primary prey species in August were C.affinis,E.sinensis,Themisto gracilipes,Calanus sinicus,and anchovy.Consumption of these species equaled 12.4 million tons,accounting for 62.9% of the total food consumption.Thus,as in the central and southern Yellow Sea,T.gracilipes,C.sinicus,C.affinis,E.sinensis,small yellow croaker,and anchovy were the most im-portant prey species in the north Yellow Sea. The mean trophic level of fish community declined from 4.26 in 1985 to 3.66 in 2010 in the north Yellow Sea,or 0.24 decade?1.This decrease was more rapid than in the Bohai Sea and central and southern Yellow Sea and was caused by a shift in the dominant species in the fish community.The percentage of nektivores decreased concomi-tantly with an increase in generalist predators between 1985 to 2010.The rate of change in trophic level has de-creased from 0.28 decade?1 between 1985 and 2000 to 0.18 decade-1 between 2000 and 2010,but has remained higher than the global rate.Given this,we recommend continuing efforts to enhance the fishery.

Comparative analysis of the mitochondrial control region between the cultured and wild populations of Chinese shrimp (Fenneropenaeus chinensis).

In present study,genetic differentiation of the Chinese shrimp Fenneropenaeus chinensis between cultured( 21 individuals) and wild populations( 14 individuals,sequences were downloaded from the GenBank) was investigated using the sequence of mitochondrial control region ( CR ) .Four individuals of the F.merguiensis were chosen as the outgroup during the phylogenetic analysis in this study.Sequences were edited and aligned using DNA Star software and refined manually.Genetic diversity indices such as number of haplotypes,polymorphic sites,transitions,transversions,and indels were obtained using the program ARLEQUIN( Ver.3.0) .Haplotype diversity( h) and nucleotide diversity( л) were calculated with DNASP 4.0.The nucleotide compositions and the average distances between populations and within population were calculated with MEGA 4.0.The Network software was used to draw the minimum spanning tree based on the haplotype data.The results were as follows:the A + T content was higher than the G + C content in both the populations,but the G + C content was a little lower in the cultured population.The results indicated genetic divergence existed between the 2 populations based on the 563 bp sequences.The gene diversity of the wild population( 0.967 2) was a little higher than the cultured population( 0.938 0) .There was no shared haplotype between the 2 populations.The ratio of transitions/transversions of the wild populations and nucleotide diversity were 3.5 and 0.010 6 respectively while they were 4.0 and 0.009 4 for the cultured population.The nucleotide diversity of the wild population was a little higher than cultured population.The K-2P distance was 0.010 8 between the 2 populations,0.010 7 in the wild population and 0.009 5 in the cultured population.Both the NJ phylogenetic tree and the haplotype minimum spanning tree showed no significant genealogical structure.The exact test of population differentiation showed that the 2 populations were significantly different ( P=0.000 9) .The FST value between the populations was 0.069 8( P=0.00) ,which indicated that the difference between 2 populations was significant.This may indicate that some alleles were lost during the aquaculture.