Status and historical changes in the fish community in Erhai Lake

Erhai Lake is the second largest freshwater lake on the Yunnan Plateau, Southwest China. In recent decades, a number of exotic fish species have been introduced into the lake and the fish community has changed considerably. We evaluated the status of the fish community based on surveys with multimesh gillnet, trap net, and benthic fyke-net between May 2009 and April 2012. In addition, we evaluated the change in the community using historical data (1952–2010) describing the fish community and fishery harvest. The current fish community is dominated by small-sized fishes, including Pseudorasbora parva, Rhinogobius giurinus, Micropercops swinhonis, Hemiculter leucisculus, and Rhinogobius cliffordpopei. These accounted for 87.7% of the 22 546 total specimens collected. Omnivorous and carnivorous species dominated the community. A canonical correspondence analysis (CCA) plot revealed that the distribution of fishes in the lake is influenced by aquatic plants, water temperature, pH, and season. The abundance of indigenous species has declined sharply, and a majority of endemic species have been extirpated from the lake (a decrease from seven to two species). In contrast, the number of exotic species has increased since the 1960s to a total of 22 at present. The fishery harvest decreased initially following the 1960s, but has since increased due to the introduction of non-native fish and stocking of native fish. The fishery harvest was significantly correlated with total nitrogen, not total phosphorus, during the past 20 years. Based on our results, we discuss recommendations for the restoration and conservation of the fish resources in Erhai Lake.     

Fish community diversity in the middle continental shelf of the East China Sea

The status of fishery stocks in the coastal waters of China is far from ideal, mainly due to climate change and the impacts of human activities (e.g., pollution and overfishing). Thus, the restoration and protection of fishery resources have become critical and complex. The stability and balanced structure of the fish community is a basic foundation for the protection of fishery resources. Based on data collected from bottom trawls by the R/V Beidou in continental shelf of the East China Sea in November 2006 and February 2007, changes in the composition and diversity of fish species and functional groups were analyzed. The research area was divided into offshore waters and inshore waters by the two-way indicator species analysis (TWIA). The results showed that the dominant species were different between offshore waters and inshore waters and also varied with the survey time. The most abundant family was Sciaenidae and Teraponidae in November 2006, Sciaenidae, Engraulidae and Triglidae were most abundant in February 2007. The species belonged mainly to mobile piscivores (G6), benthivores/piscivores (G4), benthivores (G3) and planktivores (G1), and the dominant species in November 2006 were commercial species (e.g. Larimichthys polyactis and Trichiurus japonicus), but small-sized species were dominant in February 2007 (e.g., Harpadon nehereus, Benthosema pterotum, Champsodon capensis, and Acropoma japonicum). The species diversity showed a similar trend as the functional group diversity. Stations with higher diversity were mainly distributed in inshore waters in February 2007, whereas higher diversity was found in offshore waters in November 2006. The highest biomass and species number were found in G6 group, followed by the G4, G5 and G1 groups. The distribution of the number of individuals of each functional group showed the opposite trend as that of the biomass distribution. In addition, the size spectra were mainly concentrated around 3–29 cm, and the individual number of fish species gradually decreased with the increase in body size, but the relative biomass showed a moderate fluctuation in each size class. These changes showed that species with faster growth rate and earlier maturity age became dominant in continental shelf of the East China Sea. So the variations in biological characteristics of fish should be fully considered in maintaining sustainable utilization of fishery resource.     

东海中部夏季鱼类群落结构及其多样性分析

根据2008年8月东海区主要渔场重要渔业资源调查资料,分析东海中部鱼类的种类组成、区系特征、多样性等群落结构特征。结果表明:共调查捕获鱼类88种,其中暖水种59种,占67.0%;暖温种29种,占33.0%。相对重要性指数(IRI)值大于500的优势种鱼类共有5种,分别为带鱼、刺鲳、小黄鱼、六斑刺鲀和鳄齿鱼;种类丰富度指数变动范围为0.10～2.31,平均为0.88;Shannon-Wiener多样度指数变动范围为0.01～1.86,平均为0.87;种类均匀度指数变动范围为0.01～0.92,平均为0.41;东海中部夏季鱼类多样性指数与往年相比有下降的趋势。     

Significant effects of fishing gear selectivity on fish life history

Over the past few decades, extreme changes have occurred in the characters of exploited fish populations. The majority of these changes have affected the growth traits of fish life history, which include a smaller size-at-age, an earlier age-at-maturation and among others. Currently, the causes of these life history traits changes still require systematic analyses and empirical studies. The explanations that have been cited are merely expressed in terms of fish phenotypic adaptation. It has been claimed that the original traits of fish can be recovered once the intensity of exploitation of the fish is controlled. Sustained environmental and fishing pressure will change the life history traits of most fish species, so the fish individual’s traits are still in small size-at-age and at earlier age-at-maturation in exploited fish populations. In this paper, we expressed our view of points that fishing gear has imposed selectiv-ity on fish populations and individuals as various other environmental factors have done and such changes are unrecoverable. Ac-cording to the existing tend of exploited fish individual’s life history traits, we suggested further researches in this field and provided better methods of fishery management and thereby fishery resources protection than those available early.     

Are the fish of the upper and lower Mekong interconnected？

The Mekong supports one of the richest inland fisheries in the world, with many of the fish migrating long distance to spawn. Little is known about the fisheries and migration strategies of the Upper Mekong whilst it is supposed that many fish species move between the Lower and Upper Mekong. Most likely, natural fish migration in the river has been altered by dam construction across the mainstream of the Upper Mekong. In this paper, the interconnectivity of fish species between different sections of the Mekong and negative impacts of dams on migratory fish are studied. Of the 162 fish species in the Upper Mekong and the 869 species in the Lower Mekong, 61 species are common. Results show that there is no significant difference at order level between the UM and LM. Similarity coefficients are used to evaluate interconnectivity at species, genus and family levels among four different sections of the Upper Mekong with each other and with the Lower Mekong as a whole. The highest similarity is found between the middle and lower reach of the Upper Mekong at species and genus levels and the middle and upper reach at family level. Of the eight cascade dams, Mengsong Dam in planning is considered as the biggest threat to migratory fish from the Lower Mekong and should be particularly concerned. Supported by National Natural Science Foundation of China (No. 40601096)     

ARTIFICIAL PROPAGATION AND BREEDING OF MARINE FISH IN CHINA

Since the 1990s, artificial propagation and breeding technique of marine fish in China have developed by way of increasing species and fry numbers, with special stress laid on valuable species. Large quantities of artificial fry can meet the needs of both marine cage culture and pond culture for most species. Experimental results obtained by scientists have been put into use in actual production.Fish fry production has entered a period of sustainable development. So far, at least 44 species (21 families) of marine fish have been successfully bred in China. The artificial fry number of large yellow croaker ( Pseudosciaena crocea) exceeded 300 million in 1999. The species whose artificial fry numbers have each surpassed 10 million annually are red drum ( Sciaenops ocellatus ), Japanese seabass ( Lateolabrax japonicus), cuneate drum (Nibea miichthioides ), spring spawning red seabream (Pagrosomus major ) and threebanded sweethp ( Plectorhynchus cinctus ). Millions of artificial fry are bred annually in the species of black porgy ( Sparus macrocephalus ), Russell‘ s snapper ( Lutjanus russeUi ), javelin gnmt ( Pomadasys hasta ), miiuy croaker ( Miichthys miiuy) and skewband gnmt ( Hapalogenys nitens ). The fish in the family Sciaenidae are the main species in artificial propagation and breeding. Some problems and prospects on marine fish culture and stock enhancement are also discussed and some proposals for sustainable development are put forward in this article.     

Primary fish survey in the Huanghe River estuary

The survey in the Huanghe River estuary indicated that the 85 fish species found there comprised three faunal elements: warm-water species (29.4%), warm-temperate species (55.3%) and cold-temperate species (15.3%). The seasonal changes of fish species, density and biomass are obvious. The total biomass is highest (7 699t) in August and lowest (489 t) in January.Setipinna taty has mean density of 9 278 indiv/km², and is the most important species constituting 25.5% of the total weight of fish caught.Trichiurus haumela was a dominant species in the 1950s, but no one was caught in this survey. There were obvious changes of the dominant fish species during the recent three decades. The demersal fish biomass has dropped greatly to only 1/10 in over 50 years since 1930. Contribution No. 2210 from the Institute of Oceanology, Academia Sinica.     

Modern movement and deformation in the South China Sea shown by GPS measurements and numerical simulation

To better understand the crustal deformation of the South China Sea Basin, we produce a mechanically consistent 2-dimensional model for observing regional velocity field in the South China Sea (SCS). We studied the dominating regional tectonic stress field by geodetic measurements and finite element analysis, the spatial variations of velocity field and strain field, and relative movements among different blocks, using a 2-dimensional model describing crustal deformation of the South China Sea Basin. Strain results show that the SCS is extending at present. The western part of SCS is opening gradually in NWSE direction from its northern margin to the south, but the eastern part of SCS is opening gradually from its central part to the north and south. In addition, we analyzed the plate kinematics to the deformation of the SCS, using a two-dimensional finite element model. Our simulations results are well explained by available geodetic data. The movement of SCS is resulted from interactions among Indian Plate, Pacific Plate, Philippine Sea Plate, and Eurasian Plate.     

THE REGIONAL AIR-SEA COUPLED OSCILLATION IN THE SOUTH CHINA SEA

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅＳｏｕｔｈＣｈｉｎａＳｅａ (ＳＣＳ)ｉｓａｕｎｉｑｕｅｓｅｍｉ ｅｎｃｌｏｓｅｄｄｅｅｐｏｃｅａｎｂａｓｉｎｌｏｃａｔｅｄｎｅａｒｔｈｅｗｅｓｔ ｅｒｎｐｅｒｉｐｈｅｒｙｏｆｔｈｅＰａｃｉｆｉｃＯｃｅａｎ .Ｓｐｒｅａｄｉｎｇｆｒｏｍｔｈｅｅｑｕａｔｏｒｔｏ 2 0°Ｎａｎｄｓｐａｎｎｉｎｇｚｏｎａｌｌｙａｂｏｕｔ1 5°Ｎ ,ｔｈｅＳＣＳｌｉｅｓｂｅｔｗｅｅｎｔｈｅＳｏｕｔｈＣｈｉｎａｃｏａｓｔａｎｄｔｈｅｍａｒｉｔｉｍｅｃｏｎｔｉｎｅｎｔ.ＴｈｅＳＣＳｂｏｔｔｏｍｔｏｐｏｇｒ…     

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.     

镇江长江豚类省级自然保护区鱼类多样性及年际变化

【目的】调查了解镇江豚类保护区鱼类资源状况,丰富鱼类资源本底数据。【方法】于2013、2016和2019年,分别开展3次渔业资源调查,对该区域鱼类种类组成、优势种、体型大小及群落多样性进行统计分析。【结果】共记录鱼类68种属于7目13科47属;鲤形目(Cypriniformes)鱼类种类占比较为稳定,鲇形目(Siluriformes)鱼类资源量有下降趋势,鲈形目(Siluriformes)鱼类种类占比上升明显;不同年份优势种替代较为明显;2016年的物种丰富度指数和多样性指数最高,分别为6.528、3.026。【结论】保护区鱼类资源较为丰富,但不同年份鱼类群落变化较为明显,渔业资源面临小型化趋势。     

Intrusions of Kuroshio and Shelf Waters on Northern Slope of South China Sea in Summer 2015

The northern slope region of the South China Sea(SCS) is a biological hot spot characterized by high primary productivity and biomasses transported by cross-shelf currents, which support the spawning and growth of commercially and ecologically important fish species. To understand the physical and biogeochemical processes that promote the high primary production of this region, we conducted a cruise from June 10 and July 2, 2015. In this study, we used fuzzy cluster analysis and optimum multiparameter analysis methods to analyze the hydrographic data collected during the cruise to determine the compositions of the upper 55-m water masses on the SCS northern slope and thereby elucidate the cross-slope transport of shelf water(SHW) and the intrusions of Kuroshio water(KW). We also analyzed the geostrophic currents derived from acoustic Doppler current profiler measurements and satellite data. The results reveal the surface waters on the northern slope of the SCS to be primarily composed of waters originating from South China Sea water(SCSW), KW, and SHW. The SCSW dominated a majority of the study region at percentages ranging between 60% and 100%. We found a strong cross-slope current with speeds greater than 50 cms~(-1) to have carried SHW into and through the surveyed slope area, and KW to have intruded onto the slope via mesoscale eddies, thereby dominating the southwestern section of the study area.     

Interannual oscillation of meridional sea level wind and its impact on sea surface temperature in the South China Sea

Analysis of COADS data (1958–1987) showed that there is obviously interannual SST oscillation including QBO (Quasi-biennial oscillation) and quasi-3.5 year oscilation, etc., of the SCS (South China Sea), which is the response of the upper mixed layer of the sea to the impact of the East Asian Monsoon anomaly. Most SST anomalies appear in the central basin of the SCS. The phase-locked phenomena linking the SST annual cycle and interannual oscillation is an important characteristic of the SCS climate. There is not only SST response to atmospheric impact, but also feedback to the air. The authors put forward a scheme of regional air-sea interaction in winter time in the SCS. Project 49676276 supported by NSFC and also supported by FSEC.     

Species Composition and Gear Characteristics of the Macrobrachium Fishery of the Cross River Estuary,Nigeria

The Cross River Estuary,Nigeria,is an important shrimping area for artisanal fishermen of the coastal communities.The multi-species Macrobrachium fishery is exploited with three main gears,namely beach seine,push net and trap.Studies on species composition of this fishery recorded thirteen shrimp species,one swimming crab (Callinectes amnicola) and two fish species (Eleotris sp.and Pellonula leonensis).The shrimp species identified included Macrobrachium macrobrachion (83.39% and 55.69% by number and weight,respectively),M.vollenhovenii (9.66% and 37.18%),M.equidens (3.8% and 2.87%),juveniles-sub-adults of Penaeus notialis (1.11% and 1.3%),M.dux,M.felicinum,Palaemonetes africanus,Palaemon maculatus,Palaemon elegans,Desmocaris sp.,Leander sp.,Nematopalaemon hastatus and Alpheus pontederiae.While the selectivity index for trap was 0.25,beach seine and push net had a lower index of 0.063.The results present the first comprehensive and representative report for the Estuary shrimp fishery and will assist in the management of the biodiversity of this ecosystem.     

The post-larval and juvenile fish assemblage in the Sukhothai Floodplain,Thailand

This study investigated abundance, species composition and spatial and temporal distributions of fish larvae and their relationship with some environmental variables in the Sukhothai floodplain in northern Thailand. Fish larvae were collected from 33 sampling stations on 8 occasions between August 2010 and October 2013. The study collected and identified 149 296 individuals, representing 32 families and 165 taxa. The species composition of larval fish was dominated by the Cyprinidae(47.27%), Cobitidae(7.88%), Siluridae(6.67%), Bagridae(6.06%) and Mastacembelidae(3.33%) families. The mostabundant larval species were the Striped flying barb Esomus metallicus(16.90%), the Siamese mud carpHenicorhynchus siamensis(8.48%) and the Sumatran river sprat Clupeichthys goniognathus(8.31%). The greatest abundance and species diversity of larvae were found when the river flow runs onto the floodplain. PCA and nMDS analysis revealed that the samples plot is associated with temporal distribution among years. The discharge was a major factor determining fish larvae assemblage and environmental variables in the Sukhothai floodplain. Four fish larval species were positively correlated with the samples for 2013. The result of the CCA ordination plot showed that only the discharge variable was strongly correlated with fish larvae abundance, especially two cyprinid R asbora species.     

On the deep sea demersal fish communities of the East China Sea

Cluster analysis of data on the species similarity index offish samples taken at various sampling stations of different depths by the R /V " Dongfang " of the East China Sea Fisheries Research Institute, Chinese Academy of Fisheries Science, during the deep sea demersal fish resources survey in May - November, 1981, showed deep sea demersal fish fauna of the western part of the East China Sea can be grouped into the following communities :1)The outer continental shelf community ,2)The continental slope community, and3)The western Okinawa Trough community .The authors found that not only the species diversity index, but also the species similarity index are important criteria to reflect the structure of biotic community.     

Uncertainties in Stock Assessment and the Precautionary Management Suggestions for the Anchovy （Engraulisjaponicus） Stock in the Yellow Sea

Anchovy(Engraulis japonicus) is an abundant fish species in the Yellow Sea,and its natural stock is decreasing rapidly in recent years. Based on the stock-recruitment(SR) data from 1987 to 2002 published in Zhao et al.(2003),the criterion BIC(Bayesian Information Criterion) is applied to selecting a suitable model from six normal and lognormal error structured SR statisti-cal models,the age-structured model is used to calculate the biological reference points(BRPs),and the precision of the SR parame-ters and BRPs are calculated using bootstrap method. The results indicate that the anchovy fishery resource in the Yellow Sea is in an over-fished state. The precaution management principle requires that the fishery should be closed immediately.     

INTERANNUAL OSCILLATION OF MERIDIONAL SEA LEVEL WID AND ITS IMPACT ON SEA SURFACE TEMPERATURE IN THE SOUTH CHINA SEA

INTRODUCTIONTheSouthChinaSea(Srs),nearthewestedgeofthetropicalwestPade,istheoTilyquasi-endotaldeepbasinintheworid,hasa相似文献   

Eukaryotic microbial distribution pattern and its potential effects on fisheries in the fish reserves of Qiantang River in breeding season

To examine the eukaryotic biodiversity of aquatic ecosystems in the Qiantang River,China,eukaryotic microbes in the river were investigated using 18 S rRNA gene sequencing during the breeding season(July to August 2018).Four distinct distribution patterns(1.Jiande;2.Tonglu and Fuyang;3.Jiubao;4.Yanguan) of the microbial community and their potential effects on fishery activities were observed.Results show lower abundances of Dinophyta and Fungi and higher abundances of Cryptophyta and Chlorophyta in Tonglu and Fuyang than those in the other three sections.In addition,the reserves(Tonglu and Fuyang)destabilized the original eukaryotic microbial co-occurrence network.Among all the environmental factors measured,nitrogen(nitrite,nitrate,ammonium),water temperature and total chlorophyll a acted as major driving factors that controlled the eukaryotic microbial distribution.Furthermore,the existence of some algae(e.g.,Chrysophyceae,Cryptophytes,and Chlorophyceae) and fungi(e.g.,Rhizophydium) in Tonglu and Fuyang was beneficial to juvenile fish growth and water quality,although some detrimental species(e.g.,Aphanomyces) needed attention.This study provides further insights into the sustainable protection and utilization of rivers.     

Fish assemblage structure in the hypoxic zone in the Changjiang (Yangtze River) estuary and its adjacent waters

Fish assemblage structure in the hypoxic zone in the Changjiang (Yangtze River) estuary and its adjacent waters were analyzed based on data from bottom trawl surveys conducted on the R/V Beidou in June, August and October 2006. Four fish assemblages were identified in each survey using two-way indicator species analysis (TWIA). High fish biomass was found in the northern part, central part and coastal waters of the survey area; in contrast, high fish diversity was found in the southern part of the survey area and the Changjiang estuary outer waters. Therefore, it is difficult to maintain high fishery production when high fish diversity is evenly distributed in the fish community. Fish became smaller and fish size spectra tended to be narrower because of fish species variations and differences in growth characteristics. Fish diversity increased, the age to maturity was reduced and some migrant species were not collected in the surveys. Fish with low economic value, small size, simple age structure and low tropic level were predominant in fish assemblages in the Changjiang estuary and its adjacent waters. The lowest hypoxic value decreased in the Changjiang estuary and its adjacent waters.