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In order to assess the metal pollution in the Wujiang River, concentrations of Cu, Zn, Fe, Mn, Pb, Cd, As, and Hg in the water, sediments, and two fish species Cyprinus carpio and Pelteobagrus fulvidraco from the middle reaches (Tuomugang, TMG) and lower reaches (Wulong, WL) of the Wujiang River were examined. The results indicated that all metal concentrations were lower than the values for grade one water quality according to the Environment Quality Standard for Surface Water of China (GB 3838–2002). The bioavailable fraction concentrations of Zn, Fe, Mn, Pb, and Hg in WL were significantly higher than those in TMG (p < 0.05), indicating that these metals in sediments of WL have higher bioavailability and mobility. The Cu, Zn, Fe, Pb, As, and Hg were mainly related to the residual fraction, while the Mn and Cd were mainly associated with the non-residual fraction. The risk assessment code (RAC) and the secondary phase to the primary phase (RSP) values indicated that Mn and Cd have a high risk of secondary release. The mean metal concentrations in the liver of the two fish species were higher than those in muscle. The higher metal concentrations of fish in WL suggested that bioaccumulation of metals in fish could be influenced by metal bioavailability. No identical relationships between metal concentrations and fish length were manifested in the present study. The values of target hazard quotient (THQ) and hazard index (HI), and carcinogenic risk (CR) of metals for the consumption of C. carpio and P. fulvidraco indicated that the anglers would likely not experience significant non-carcinogenic risk, but the carcinogenic risk of As cannot be ignored. Thanks to prohibited commercial fishing in the Wujiang River, the metal pollution will probably not pose a health risk to the general public for wild fish consumption. [ABSTRACT FROM AUTHOR]

The total length‐weight relationships (LWRs) were estimated for six fish species from the lower reaches of the Jinsha River, southwest China. Specimens were seasonally collected using gillnets and drift gillnets (mesh size 2~14 cm), benthic fyke nets (mesh size 1 cm), baited hooks (stationary longline) and electricfishing (36 V/12 A, depth 3 m), in six sites from 2016 to 2019. The fish length (TL = total length, standard length (SL) as well as weight (W) were determined to the nearest 0.1 cm and 0.01 g, respectively. The LWRs for Jinshaia abbreviata (Günther, 1892) and Liobagrus marginatoides (Wu, 1930) are newly reported to FishBase. New maximum length or weight values were recorded for Pseudolaubuca engraulis (Nichols, 1925), Pseudobagrus truncatus (Regan, 1913), L. marginatoides, Abbottina obtusirostris (Wu & Wang, 1931) and Pseudobagrus pratti (Günther, 1892). All regressions were highly significant, with the coefficients of determination r2 > 0.950, and b values in the LWRs equations ranged from 2.399 to 3.484. For comparison and conversion, the SL‐TL relationships were also estimated, with r2 values ranging from 0.980 to 0.999. [ABSTRACT FROM AUTHOR]

Abstract: Non-vegetated creek edges were investigated to explore spatial nekton use patterns in a low salinity intertidal salt marsh creek network of the Yangtze River estuary along a stream-order gradient with four creek orders. Non-vegetated creek edges were arbitrarily defined as the approximately 3 m extending from the creek bank (the marsh–creek interface) into open water. Nekton was sampled using seine nets during daytime high slack water during spring tides for two or three days each in May through July 2008. Twenty-three nekton species (16 fishes and 7 crustaceans) were caught during the study. Fishes were dominated by gobies (Mugilogobius abei, Periophthalmus magnuspinnatus, Periophthalmus modestus, Synechogobius ommaturus), mullets (Chelon haematocheilus, Liza affinis) and Chinese sea bass (Lateolabrax maculatus). Crustaceans were dominated by mud crab (Helice tientsinensis) and white prawn (Exopalaemon carinicauda). Rank abundance curves revealed higher evenness of nekton assemblages in lower-order creeks compared to higher-order creeks. Fish abundance tended to increase with increasing creek order. Crustacean abundance was higher in the first–third order creeks than in the fourth-order creek. Dominant nekton species displayed various trends in abundance and length–frequency distributions along the stream-order gradient. The spatial separation of nekton assemblages between the first–third order creeks and the fourth-order creek could be attributed to geomorphological factors (distance to mouth and cross-sectional area). These findings indicate that both lower- and higher-order creek edges play important yet different roles for nekton species and life history stages in salt marshes. [Copyright &y& Elsevier]

The elemental signature in otolith nuclei was determined using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) for stock discrimination of adult anadromous tapertail anchovy, Coilia nasus, in five Chinese estuaries. Five elements (Na, Mg, K, Sr, and Ba) were well detected in the otolith nuclei of the adult fish. Results showed that the elemental composition in the otolith nuclei varied substantially among the estuaries. Age and fish length data showed no significant influences on the elemental concentration ratios across the sample sites. The Sr:Ca and Ba:Ca ratios were inter-site distinct and could be used as natal tags for discriminating among stocks. Discriminant function analyses (DFA) showed that these ratios can be used in discriminating the Liaohe River estuary (LD, 92.3 %), the Yangtze River estuary (CJ, 86.7 %), and the Yellow River estuary (HH, 76.9 %) samples with high classification accuracy, followed by the Haihe River estuary (BH, 58.3 %) and the Daguhe River estuary (JZ, 46.2 %) samples. An overall classification accuracy rate of 72.7 % from the discriminant functions indicated that elemental fingerprinting appeared to have the potential to discriminate between tapertail anchovy stocks in these estuaries. [ABSTRACT FROM AUTHOR]

Simple Summary: In the sorting process of Chinese softshell turtles, it is necessary to classify them based on their weight and accurately identify their plastron and carapace. This process requires heavy manual labor and complex mechanical processing methods. To improve processing efficiency and reduce costs, this article introduces machine vision technology, and a new image processing method is proposed. This method can estimate the weight of Chinese softshell turtles and accurately locate the positions of their plastron and carapace. The automation level of aquaculture can be greatly enhanced, and hardware costs can be reduced through software optimization through this approach. With the rapid development of the turtle breeding industry in China, the demand for automated turtle sorting is increasing. The automatic sorting of Chinese softshell turtles mainly consists of three parts: visual recognition, weight prediction, and individual sorting. This paper focuses on two aspects, i.e., visual recognition and weight prediction, and a novel method for the object detection and weight prediction of Chinese softshell turtles is proposed. In the individual sorting process, computer vision technology is used to estimate the weight of Chinese softshell turtles and classify them by weight. For the visual recognition of the body parts of Chinese softshell turtles, a color space model is proposed in this paper to separate the turtles from the background effectively. By applying multiple linear regression analysis for modeling, the relationship between the weight and morphological parameters of Chinese softshell turtles is obtained, which can be used to estimate the weight of turtles well. An improved deep learning object detection network is used to extract the features of the plastron and carapace of the Chinese softshell turtles, achieving excellent detection results. The mAP of the improved network reached 96.23%, which can meet the requirements for the accurate identification of the body parts of Chinese softshell turtles. [ABSTRACT FROM AUTHOR]

Japanese anchovy (Engraulis japonicus) is a small pelagic fish with commercial and ecological importance. In spite of its importance, in recent years, specific research on anchovy in the Shandong Peninsula area has been relatively scarce and outdated. This study aims to estimate the age and growth characteristics of anchovy through year-round seasonal sampling from 2016 to 2017, utilizing length–frequency and otolith microstructure analysis. The higher coastal abundance and larger size observed in the spring and summer suggest a potential peak spawning period for anchovies dominated by larger-sized individuals. Based on otolith analysis, anchovies range in age from 0 to 4 years, with a limited presence at age 0 and dominance in the age-1 group. The length–weight relationship (LWR) equation shows hyper-allometric growth for each season, with a mean relative condition factor (Kn) of 1.025 ± 0.005, indicating good health. Additionally, the von Bertalanffy growth equation of can be expressed as Lt = 154.40 [1 − e−0.604 (t + 0.965)], suggesting a medium growth rate (K = 0.604). These findings contribute to the understanding of anchovy age and growth patterns, emphasizing the continuous need for research and monitoring to support rational and sustainable fisheries management and conservation efforts. [ABSTRACT FROM AUTHOR]

Brominated flame retardants (BFRs) have attracted increasing attention in recent decades because of their persistence, distribution, bioaccumulation, and biotoxicity in the environment. In the present study, the levels and distribution of polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyl (PBBs) in twenty-four samples of twelve fish species collected from the Three Gorges Reservoir (TGR) were analyzed. The results indicated that SPBDE concentrations in fish muscle ranged from 22.62 pg g-1 by wet weight (ww) (yellowcheek carp) to 217.75 pg g-1 ww (yellow catfish). BDE47 and BDE209 were the most predominant congeners, with their sum accounted for 23.62-68.16% of SPBDEs. SPBB concentrations ranged from 27.83 pg g-1 ww (silver carp) to 155.75 pg g-1 ww (topmouth culter); BB49 and BB209 were detected in all samples, with concentrations ranging from 4.62 to 47.10 pg g-1 ww and 1.29 to 80.95 pg g-1 ww, respectively. There are no significant correlations between the BFRs levels and fish length (or weight) in these samples. Compared to other areas, the level of BFRs in edible fishes from TGR was low. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are a major global issue in the marine environment, and fish inhabiting coastal environments are susceptible to the ingestion of MPs. Knowledge regarding MPs in fish along the coast of China is very limited. In this study, the characteristics and retention of MPs in 19 fish species in the Yellow Sea were systematically studied. MPs were detected in all of the fish species sampled. Overall, 34% (444/1320) of fish retained plastic, and 552 pieces of plastic were removed from these fish, among which 546 pieces (99%) were microplastics (i.e., <5 mm). Three MP types were found: fibers, pellets, and fragments, which accounted for 67%, 22%, and 11% of the total, respectively. MP length ranged from 16 to 4740 μm, with an average of 941 ± 43 μm. The average lengths of the fibers, pellets, and fragments were 1233 ± 57 μm, 263 ± 24 μm, and 503 ± 91 μm, respectively, and MP length was positively correlated with fish length. Fourteen polymers were detected, with organic oxidation polymers (40%) being most abundant, followed by polyethylene (22%) and polyamide (11%). The retention of MPs in fish was affected by sampling areas and fish weight. Fish collected from the area adjacent to the Bohai Sea and the Yangtze River Estuary were found to possess higher levels of MPs than those collected from the center of the Yellow Sea. The average MP/fish for fish with plastic was negatively correlated with fish body weight. The retention of MPs may affect the quality and quantity of fishery resources in the Yellow Sea, especially the commercial fish. It is suggested that future studies be conducted to determine the ingestion rate, retention time, and egestion rate of MPs by fish to enable a rational risk assessment by combining the field results. Image 1 • A moderate level of microplastic abundance was found in fish from the Yellow Sea. • The dominant MPs in fish from the Yellow Sea were fibers. • The chemical compositions of MPs were diverse, with high density plastics dominant. • Larger fish tended to retain larger MPs, but showed lower amounts of MP/fish. • Fish from areas with heavier human activities showed higher MPs retention. [ABSTRACT FROM AUTHOR]

In this work we studied the accumulation of heavy metals in nine species of fish with different life and feeding habitats which are native and major commercial fish in the Baotou Urban Section of the Yellow River. The results showed that the concentration of heavy metals was significantly dependent on fish species; the pollution index of heavy metals in different species were ranked as Hemiculter leucisclus > Carassius auratus auratus > Hemibarbus maculatus > Megalobrama amblycephala > Abbottina rivularis > Cyprinus carpio > Squaliobarbus curriculus > Perccottus glehni > Saurogobio dabryi. Product-moment correlation coefficients among the metal pairs Pb-Zn, Cu-Cd, Cu-Zn, Cu-Pb, Pb-Cd, and Zn-Cd revealed there was no competitions between metals in each tissue. Correlations between heavy metal concentrations and fish length or weight indicated that accumulation of the heavy metals by the different fish species was related to their surrounding environments and their life and feeding habitats. According to the mean bioconcentration factors (BCFs), the heavy metal concentrations in these nine species were ranked Zn ≫ Cu > Cd ≈ Pb. In this work, the bioaccumulation factors (BAFs) were developed by using the sum of exchangeable and bound-to-carbonate heavy metals as Cs values. It was found that BAFs better reveal the accumulation characteristics of the heavy metals in the fish, which might provide an effective method for assessing bioaccumulation of heavy metals. [ABSTRACT FROM AUTHOR]

Due to the rarity of Chinese paddlefish ( Psephurus gladius), very little information is available on this species. In order to save this critically endangered giant species, four large-range hydroacoustic surveys (using an echo sounder with a 199 kHz, 6.8° split-beam transducer) and capture surveys (by drift nets and setlines) were conducted in the upper Yangtze River during 2006–2008. According to the target strength (TS) study on Polyodon spathula ( Hale et al., 2003 ) and Love’s formula about TS-fish length relationships ( Love, 1971 ), the four acoustic surveys identified nine potential targets (TS > −26.29 dB) of P. gladius, two (TS > −22.40 dB) of them very probably the fish species sought. A total of 4762 setlines, 111 anchored setlines and 950 drift net catches were conducted in which 472 large fish specimens of various species were caught. However, no single P. gladius was caught directly. The gear used did not allow quantitative capture over rough ground with deep holes, perhaps allowing some large fish to effectively hide or escape; the hydroacoustic signals indicated this as likely. In any case, it is strongly suggested that P. gladius is on the verge of extinction and further rigid measures are proposed to save the very few remaining specimens. [ABSTRACT FROM AUTHOR]

The Yarlung Zangbo River is a river with abundant hydropower resources but fragile biodiversity in China. As an important benchmark for both research and ecological management, there is still a lack of knowledge about the swimming ability of fishes in the Yarlung Zangbo River. The induced flow velocity (U ind ), critical swimming speed (U crit ), and burst swimming speed (U burst ) of five Schizothoracinae species were tested in this study. Relative swimming ability related to body length and body shape was calculated. The results indicated that the average absolute swimming speeds (U ind-a , U crit-a , and U burst-a ) of all the experimental fish were 10.20 ± 0.01, 57.58 ± 3.28, and 69.54 ± 2.94 cm/s, respectively, and the corresponding relative U ind , U crit , and U burst related to body length (U ind-l , U crit-l , U burst-l ) were 1.15 ± 0.07, 5.04 ± 0.26, and 7.23 ± 0.28 BL/s, respectively. Moreover, relative U ind , U crit , and U burst related to body shape (U ind-s , U crit-s , and U burst-s ) were 0.80 ± 0.13, 2.49 ± 0.51, and 4.32 ± 0.57 cm -2 /s, respectively. No significantly differences in relative swimming speeds existed among five species. Only Oxygymnocypris stewartii was significantly weaker in U burst-s than Schizothorax o'connori. The body shape showed a stronger relationship with swimming speed than the body length did. Schizothoracinae fish in the Yarlung Zangbo River basin are less sensitive to the water flow and performed weaker U crit and U burst compared to those in the Yangtze River basin, indicating that Schizothoracinae fish in the Yarlung Zangbo River may be more susceptible to threats from environmental changes. The paper enriched the research on the swimming ability of Schizothoracinae fishes and provided efficient data for the fish conservation in the Yarlung Zangbo River., (© 2024 Fisheries Society of the British Isles.)

To investigate the age composition, growth pattern, mortality, and exploitation rate of Triplophysa scleroptera in the upper reaches of the Yellow River, we measured the total length (L) and body weight (W) of 347 individuals based on three sampling surveys from 2022 to 2023. The otoliths were used in this investigation to determine age. The total length of the collected samples ranged from 5.69 cm to 18.40 cm, body weight ranged from 1.65 g to 50.22 g, and the age ranged from 1 to 7 years old. The relationship of total length and body weight was W = 0.009 L 2.942 for the total samples, and the growth pattern observed in the study belongs to the isometric type. The von Bertalanffy growth equation revealed that the fish had an asymptotic total length L∞ of 37.536 cm, and the growth coefficient K was 0.064 yr−1. Total instantaneous mortality rate (Z) of total samples calculated by the age-based catch curve method was 1.092 yr−1. The average instantaneous rate of the natural mortality (M), estimated by three different methods, for the total samples was 0.237 yr−1. The instantaneous rate of fishing mortality (F) for the total samples was calculated as 0.855 yr−1, and the exploitation rate (E) was determined as 0.783. As a whole, compared with other Triplophysa fishes, the growth rate of T. scleroptera in the upper reaches of the Yellow River is relatively slow, and the population of T. scleroptera has been overexploited. It is crucial to establish some effective management strategies to protect this species. [ABSTRACT FROM AUTHOR]

The purpose of this study was to analyze levels of heavy metals and human health risk implications associated with fish consumption from the Yangtze River. A total of 60 fish muscles were taken from six different fish species—Hypophthalmichthys molitrix, Ctenopharyngodon idellus, Blicca bjoerkna, Mylopharyngodon piceus, Carassius carassius and Pelteobagrus fulvidraco—and digested using standard protocols. Contents of lead (Pb), cadmium (Cd), zinc (Zn), aluminum (Al) cobalt (Co), manganese (Mn), chromium (Cr), and copper (Cu), were analyzed using an Atomic Absorption Spectroscophotometer ((ZEEnit 700 P Zeeman)). Based on consumer health risk indicators, the health implications to children and adults upon consuming the analyzed fish species were assessed. Findings revealed that Zn recorded the highest mean concentration of 9.87 µg/g in Carassius carassius followed by Mn (7.97 µg/g) in Pelteobagrus fulvidraco, Cu (2.07 µg/g) in Mylopharyngodon piceus, Pb (1.04 µg/g) in Hypophthalmichthys molitrix, Cr (0.63 µg/g) in Hypophthalmichthys molitrix, Cd (0.19 µg/g) in Blicca bjoerkna and Ni (0.16 µg/g) (w/w) in Pelteobagrus fulvidraco. In addition, the health risk assessments revealed that children are at heightened non-carcinogenic risk for Pb, Cd, and Co upon consuming the examined fish species. [ABSTRACT FROM AUTHOR]

The weight–length relationship (WLR) of fish is a crucial tool in fish biology research and has received extensive attention. However, fish growth is influenced by many factors, and the WLR also changes accordingly. Our aim was to investigate how fish body shape is affected by various factors by analyzing the existing parameters of the relationship between fish body length and weight. We analyzed 198,354 fish specimens belonging to 402 species of 82 families in China and investigated the change of fish body shape in the function of their ecology. Herbivorous fish tended to be shorter and fatter than carnivorous fish, and omnivorous fish fall somewhere in between. This difference could be due to variations in feeding habits and the availability of food sources. Additionally, fish living in lentic waters tended to have a shorter and fatter body shape compared to those living in lotic waters. This could be attributed to differences in swimming behavior in these environments. Furthermore, our results showed that the b value decreased as altitude increased, and fish tended to be thinner and longer due to lower oxygen and temperature levels in high-altitude waters. Overall, our study provides valuable insights into the WLR of fish and the impact of multiple factors on fish body shape. [ABSTRACT FROM AUTHOR]

Hybrid sturgeon is an important economic fish species in China. In 2021, a bacterium was isolated from the liver and kidneys of freshwater-farmed hybrid sturgeon in Yichang City, Hubei Province, causing a disease with high mortality and surface bleeding. Through morphological observation, 16S rDNA gene sequence analysis, pathogenicity, an antimicrobial sensitivity test, as well as serum physiological and biochemical analysis, it was identified as Staphylococcus saprophyticus and named E702. The 16S rDNA gene sequence of E702 is highly homologous to S. saprophyticus in GenBank. Phylogenetic analysis showed that E702 and S. saprophyticus clustered into one clade. The 50% lethal dose of E702 was 2.14 × 105 CFU/g. The percentages of monocytes and eosinophils were markedly increased in the diseased sturgeon's blood, whereas the percentages of platelets and lymphocytes were decreased. The activity levels of aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase in the diseased fish were significantly increased. The diseased fish suffered obvious damage to many tissues and organs, especially the liver and kidney, showing swelling, hyperemic and inflammatory cell infiltration. E702 was sensitive to antibiotics such as neomycin, cefazolin, norfloxacin, carbenicillin, gentamicin and ciprofloxacin. The study not only proved that S. saprophyticus was responsible for a great deal of hybrid sturgeon deaths, but also shed light on its potential risks in hybrid sturgeon farming. The research results provided the theoretical basis for the diagnosis as well as prevention of this disease. [ABSTRACT FROM AUTHOR]

The study described the length–weight relationships (LWRs) and diversity status of fishes in the midstream of the Jialing River, which is the largest tributary of the upper Yangtze River, China. A total of 4592 specimens from 53 fish species belonging to three orders and eight families were collected from December 2021 to November 2022. The results showed that Culter oxycephaloides, Xenocypris davidi, Hemibarbus labeo, Hemiculter tchangi were dominant fish species in the study region. Twenty-five fish species (IRI ≥ 10) were subjected to LWR analysis, and the regression parameters a and b for fish species varied from 0.006 to 0.333 and 2.129 to 3.391. Eleven fish species were determined to have isometric growth, and 14 fish species were determined to have allometric growth. The diversity analyses suggested that the diversity status of fishes were kept relatively stable during the sampling period and that the fishes suffered moderate disturbance in the midstream of the Jialing River. The present study provided basic biology data for fish conservation and management after the fishing ban in the Jialing River. [ABSTRACT FROM AUTHOR]

The article presents a study which aims to identify the target strength (TS) of significant fish species and monitor their access during fish pass operation in China. The study shows that the fish length was around 10-31 centimeter (cm) when changing the TS to the fish length according to empirical research. It reveals that hydroacoustic monitoring is a feasible method to approximate the effectiveness of various operational modes of a fish passage with the use of different attraction devices.

Zinc (Zn) and copper (Cu) concentrations were determined in the tissues (muscle, stomach, liver, gills, skin, and gonads) of five commercial fish species (mullet Liza haematocheilus, flathead Platycephalus indicus, mackerel Scomberomorus niphonius, silver pomfret Pampus argenteus, and sea bass Lateolabrax japonicus) from Laizhou Bay in the Bohai Sea. Metal bioaccumulation was highest in the metabolically active tissues of the gonads and liver. Bioconcentration factors for Zn were higher in all tissues (gonads 44.35, stomach 7.73, gills 7.72, liver 5.61, skin 4.88, and muscle 1.63) than the corresponding values for Cu (gonads 3.50, stomach 3.00, gills 1.60, liver 5.43, skin 1.50, and muscle 0.93). Mackerel tissues accumulated metal to higher concentrations than did other fish species, but bioaccumulation levels were not significantly correlated with the trophic levels of the fish. Zn and Cu concentrations in the tissues were generally negatively correlated with fish length, except for a few tissues of sea bass. Risk assessment based on national and international permissible limits and provisional tolerances for weekly intake of Zn and Cu revealed that the concentrations of these two metals in muscle were relatively low and would not pose hazards to human health. [ABSTRACT FROM AUTHOR]

The Pearl River is a global hotspot of fish biodiversity, yet has the most threatened endemic fish species in China. Since the establishment of the Changzhou Dam in the lower reach, changes in hydrological rhythm have negatively impacted fish downstream of the dam, but their spatiotemporal distribution in response to flood alteration has received little attention. In this study, hydroacoustic surveys were undertaken monthly in 2016 to monitor the distribution and behavior of fish. Fish densities were higher during the water discharge rising stage than during the falling stage, indicating that the fish aggregate during flooding (coefficient of variation [CV] > 100%) and depart after flooding (CV < 100%), especially aggregations of large fish. The target strength (TS) was allocated to two groups as per their frequency distributions, defined as small fish (−55 dB < TS < −40 dB) and large fish (TS > −40 dB). The sizes of both groups were significantly larger during the rising stage when compared to those during the falling stage (p < 0.01). Comparatively more fish were present with a greater average TS, and a substantially greater proportion of large fish was detected during rising stages. Hydrological variation importantly influences fish aggregations, including the numbers and sizes present, with the differences being particularly pronounced between the rising and falling stages. Combined with relevant studies, it is suggested that water releases from the Changzhou Dam should be regulated to satisfy fish spawning and migration demands during the main breeding season. [ABSTRACT FROM AUTHOR]

The rapid development of China's economy has brought tremendous pressure to the marine ecosystem, and about 57% of marine fish populations have been overexploited or collapsed. A series of fisheries policies have been implemented successively to improve the decline of resources. Over the past decade, the fisheries sector has particularly increased focus on resource and ecosystem sustainability, which has led to the wider use of stock management policies in China. Therefore, fishery resource assessment is crucial, such as assessing the long-term changes in biological information. This study is based on biological characteristics of Johnius belengerii captured by bottom trawls in Xiamen Bay during two periods, beginning in 2006 and 2016. Length composition, length–weight relationship, growth, mortality, sexual maturation, and feeding intensity were analyzed. The changes in biological characteristics show that there is a phenomenon of improvement in the later period, of which the changes are closely related to a series of fisheries management strategies, such as setting closed fishing periods and non-fishing areas, and establishing fishery restoration marine protected areas. This result seems to reveal the effectiveness of a long-term series of fisheries policies. It can provide an important basis and visibility for management effectiveness. [ABSTRACT FROM AUTHOR]

An assessment of the stock status and historical changes in abundance of Coilia mystus and C. nasus in the Yangtze River Estuary, China, was carried out based on field surveys conducted in 2019–2020 and published length-frequency (L/F) data from earlier periods. These two species' current and past relative biomasses (B/BMSY) were estimated using a length-based Bayesian biomass estimation method (LBB). The LLB method also estimated their asymptotic lengths (Linf), current and optimum mean lengths at first capture (Lc; Lopt_c), and their ratios of natural and fishing mortality to growth (M/K; F/K). In response to increasing fishing pressure, both species' maximum lengths declined, along with their B/BMSY ratio, which declined for C. mystus from 1.7 in 1982 to 0.47 in 2020 and for C. nasus from 1.7 in 2006 (or earlier) to 0.17 in 2020. These assessments show that both of the two Coilia species are overfished, with C. nasus impacted more severely than C. mystus. The prospect for the recovery of these two species is briefly discussed. This contribution will help toward the management of the population of these two Coilia species and provides a basis for evaluating the effect of the 10-year fishing ban in the Yangtze River. [ABSTRACT FROM AUTHOR]

Purpose: The objective of this paper is to assess the regulation of the accumulation of heavy metals in the aquatic environment and different fish species. Methods: Water and fish samples were collected from upper to lower reaches of the Yangtze River. The heavy metal (Cd, Cr, Cu, Hg, Pb, Zn) concentrations in the muscle tissue of seven fishes were measured. Additionally, the relationships between heavy metal concentrations in fish tissue and fish size (length and weight), condition factor, water layer distribution, and trophic level were investigated. Results: Metal concentrations (milligrams per kilogram wet weight) were found to be distributed differently among different fish species. The highest concentrations of Cu (1.22 mg/kg) and Zn (7.55 mg/kg) were measured in Pelteobagrus fulvidraco, the highest concentrations of Cd (0.115 mg/kg) and Hg (0.0304 mg/kg) were measured in Silurus asotus, and the highest concentrations of Pb (0.811 mg/kg) and Cr (0.239 mg/kg) were measured in Carassius auratus and Cyprinus carpio. A positive relationship was found between fish size and metal level in most cases. The variance of the relationships may be the result of differences in habitat, swimming behavior, and metabolic activity. In this study, fishes living in the lower water layer and river bottom had higher metals concentrations than in upper and middle layers. Benthic carnivorous and euryphagous fish had higher metals concentrations than phytoplankton and herbivorous fish. Generally, fish caught from the lower reach had higher metals concentrations than those from the upper reach. Conclusions: Cadmium and lead concentrations in several fishes exceeded the permissible food consumption limits, this should be considered to be an important warning signal. [ABSTRACT FROM AUTHOR]

Concentrations of copper, zinc, mercury, and arsenic were measured in the muscle, gill and liver tissues of Coreius heterodon and Pelteobagrus vachelli collected from the rare and endemic fish nature reserve in the upper reaches of the Yangtze River. The concentrations of copper and zinc in the tissues of these two fish species were higher than those of mercury and arsenic. Highest metal concentrations were generally found in fish samples from Yibin. The concentrations of copper, zinc, mercury, and arsenic in C. heterodon were higher than that in P. vachelli. The fish from this study area were not safe for human consumption. [ABSTRACT FROM AUTHOR]

We estimated the risk posed by hydroxybenzene in farm-raised Crucian carps (Carassius carassius) from a pond on a fish farm in Beijing, China, by analyzing a time-series of observed hydroxybenzene concentrations in fish within a culturing season in year 2006. We used the basic linear regression to model the data and forecast the probability of hydroxybenzene concentration in pond fish exceeding selected health effect criteria (the risk) using Monte Carlo simulation. The risk is highly correlated with the time a fish stays in the pond. The results indicate that the risk-days in pond relationship resembles a sigmoid function with an inflection point around 150 days. The resulting model can be used to demonstrate the benefit of improving water quality in terms of increased fish production. [ABSTRACT FROM AUTHOR]

The article discusses the findings of a study which determined the age of Tibetan Catfish found in the branches of the Brahmaputra River in China. The Tibetan Catfish or Glyptosternum maculatum is the highest-priced commercial fish in Tibet and can only be caught during the period of April to September. The study showed that ages of 3-12 year old fish were determined through evaluation of otoliths and opercula, while ages from vertebrae were shown for 3-13 year-old fish. Researchers infer that correlation between fish length and size of vertebra is a valid measurement for back-calculation of growth history for both sexes of the Tibetan Catfish.

This study examined the age, growth, and maturation of 1,064 Coregonus ussuriensis individuals that were collected monthly from the middle section of the Amur River, China between 2016 and 2018. The fork length (FL) ranged from 14.9 to 49.1 cm for males and 21.5 to 58.8 cm for females, and the body weight (BW) ranged from 72.6 to 1,348.7 g for males and 107.9 to 2,854.9 g for females. The relationship of BW and FL was expressed as: BW? = 0.0324 × FL2.708; BW? = 0.014 × FL2.963. The sample ages ranged from 2 to 8 years for males and 2 to 9 years for females. We used the von Bertalanffy function based on otolith reading and observed FL data to simulate Coregonus ussuriensis growth, which has been suggested to be similar to that of other Salmonidae fishes. No significant difference in growth was determined between males and females. The monthly gonad somatic index (GSI) value ranged from 0.16% to 1.69% for males and from 0.73% to 16.15% for females, with a peak in November. Additionally, the reproductive staging suggested that the Coregonus ussuriensis spawning season was mainly in November and December. The size at maturity (FL50%) for males and females was 34.9 cm and 37.9 cm respectively, and the corresponding age (T50%) was 4.5 and 5.1, respectively. This study provides basic information for understanding the biological characteristics of Coregonus ussuriensis and should aid in the assessment and management of fishery resources. [ABSTRACT FROM AUTHOR]

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Microplastic pollution, one of the major global challenges, is a severe threaten to aquatic organisms. The purpose of this study was to investigate the abundance, distribution and characteristics of microplastics in coastal surface waters from eastern Guangdong, south China. We chose pelagic Konosirus punctatus and demersal Mugil cephalus from different sampling sites as candidate monitoring species for the ingestion of marine microplastics, and talked about the relationship between water samples and fish samples. We tried to find out the regulation about microplastics characteristics in fish samples and fish own traits. The mean abundance of microplastics in surface water was 8895 items/m3, small white fragments were dominating character. We need to increase the amount of fish data to further explore. This study would not only provide a detailed reference for a better understanding of microplastic pollution in Guangdong coastal areas, but also shed an insight in prospect of using fish as biomonitoring of microplastic wastes. Image 1 • Small white fragments were dominating character of microplastics from east coastal areas of Guangdong, south China. • There was no significant relationship between the number of fish ingestion microplastics and fish length, weight or GITs weight. • There was no significant relationship between average microplastic abundance of water samples and two fish samples. [ABSTRACT FROM AUTHOR]

Summary: The length‐weight relationships (LWRs) of three native fish species (Triplophysa hsutschouensis, Gymnocypris chilianensis and Triplophysa tenuis) from the middle reaches of the Sule River in China were determined. Samples were obtained from April 2019 to April 2021 using various types of fishing gear. The sample size, length range, weight range, LWR, 95% confidence intervals of a and b, and correlation coefficients of each species were determined. [ABSTRACT FROM AUTHOR]

In this work, rare minnow (Gobiocypris rarus) was applied as a sentinel organism and set in cages at control and test sampling sites in Donghu Lake for 4 weeks in March, June, September, and December 2016 to assess the biological toxicity of in situ water. Sampling for active biomonitoring and physicochemical variables was performed weekly. The control was obtained from the outdoor pool of the Institute of Hydrobiology, China. Superoxide dismutase, lipoperoxidation, metallothioneins, acetylcholinesterase activity, and Vtg mRNA expression were determined as biomarkers during the field exposure period. Survival and growth also were monitored to evaluate the overall physiological condition of the fish. The seasonal changes of organic pollutants and trace metals (As, Hg, Cr, Cu, Zn, Cd, Pb) in surface water were determined. The integrated biomarker response (IBR) index was applied to summarize biomarker responses and correlate stress levels with concentrations of organic pollutants and trace metals in the surface water. Results indicated that complex pollution by persistent organic pollutants and heavy metals was present in Donghu Lake and that the in situ exposed organisms were stressed. Moreover, the complex pollution of Donghu Lake in summer and autumn was more serious than that in spring and winter. Active biomonitoring combined with IBR analysis enabled good discrimination among different exposure seasons. The proposed protocol with caged rare minnow revealed marked biological effects caused by the investigated Lake and a useful approach that can easily be extended to monitor water pollution. [ABSTRACT FROM AUTHOR]

Parasite–host systems are pervasive in nature but are extremely difficult to convincingly identify in the fossil record. Here we report quantitative evidence of parasitism in the form of a unique, enduring life association between tube-dwelling organisms encrusted to densely clustered shells of a monospecific organophosphatic brachiopod assemblage from the lower Cambrian (Stage 4) of South China. Brachiopods with encrusting tubes have decreased biomass (indicating reduced fitness) compared to individuals without tubes. The encrusting tubes orient tightly in vectors matching the laminar feeding currents of the host, suggesting kleptoparasitism. With no convincing parasite–host interactions known from the Ediacaran, this widespread sessile association reveals intimate parasite–host animal systems arose in early Cambrian benthic communities and their emergence may have played a key role in driving the evolutionary and ecological innovations associated with the Cambrian radiation. Parasitic interactions are difficult to document in the fossil record. Here, Zhang et al. analyze a large population of a Cambrian brachiopod and show it was frequently encrusted by tubes aligned to its feeding currents and that encrustation was associated with reduced biomass, suggesting a fitness cost. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are a major global issue in the marine environment, and fish inhabiting coastal environments are susceptible to the ingestion of MPs. Knowledge regarding MPs in fish along the coast of China is very limited. In this study, the characteristics and retention of MPs in 19 fish species in the Yellow Sea were systematically studied. MPs were detected in all of the fish species sampled. Overall, 552 pieces of plastic were removed from a total of 1320 fish, including 546 pieces of MP （99%）(0.41 MP/fish) and 6 pieces of meso/macro-plastic (1%). Three MP types were found: fibers, pellets, and fragments, which accounted for 67%, 22%, and 11% of the total, respectively. MP length ranged from 16 to 4740 μm, with an average of 941 ± 43 μm. The average lengths of the fibers, pellets, and fragments were 1233 ± 57 μm, 263 ± 24 μm, and 503 ± 91 μm, respectively, and MP length was positively correlated with fish length. Fourteen polymers were detected, with organic oxidation polymers (40%) being most abundant, followed by polyethylene (22%) and polyamide (11%). The retention of MPs in fish was affected by sampling areas and fish weight. Fish collected from the area adjacent to the Bohai Sea and the Yangtze River Estuary were found to possess higher levels of MPs than those collected from the center of the Yellow Sea. The average number of MPs per fish (which ingested MPs) was negatively correlated with fish body weight. The retention of MPs may affect the quality and quantity of fishery resources in the Yellow Sea, especially the commercial fish. It is suggested that future studies be conducted to determine the ingestion rate, retention time, and egestion rate of MPs by fish to enable a rational risk assessment by combining the field results. [ABSTRACT FROM AUTHOR]

Climate change seriously affects habitat suitability for coldwater fish. Amur whitefish (Coregonus ussuriensis) is a commercially important coldwater fish species found in northeast China that is particularly sensitive to water temperature. We use water temperature models for Songhua (Harbin to Yilan) and Mayi rivers to predict habitat suitability for Amur whitefish and other coldwater fish species during the months of July and August in 2014 and 2100—2 months during which river temperatures can reach extremes. The predict-results showed that fish habitat was to deteriorate over time, and to be less suitable for survival of coldwater fish species in 2100 than that in 2014. Under scenario RCP4.5 (Representative Concentration Pathway 4.5), the time period during which habitat for Amur whitefish was unsuitable increased continually; under scenario RCP8.5 (Representative Concentration Pathway 8.5), Amur whitefish might even disappear from the river basin. A significant increase in river water temperature will compromise coldwater fish survival and possibly lead to their disappearance. Practical measures to control greenhouse gas emissions and reduce the impact of global warming on aquatic ecosystems must be taken. [ABSTRACT FROM AUTHOR]

Amur sturgeon Acipenser schrenckiii Brandt 1869 and kaluga Huso dauricus (Georgi 1775) are critically endangered species with populations showing significant decline from historical levels due to overexploitation, yet little is known about their population structure. Adults are not often captured in the Fuyuan reach of the Amur River, Heilongjiang Province, Northeast China, and the government prioritizes juvenile sturgeon management. This study was conducted to determine the age and length/weight relationships of juvenile Amur sturgeon and kaluga in the Fuyuan reach of the Amur River. We estimated age using pectoral fin spine sections obtained from 65 juvenile Amur sturgeon and 50 juvenile kaluga. We compared the age estimates from two readers, and found 100% between‐reader agreement in 67.7% of the Amur sturgeon and 64.0% of the kaluga. The majority of differences in estimated age were within 1 year. Length/weight relationships (LWR) were calculated, and the LWR of the Amur sturgeon and kaluga were W = 0.0025L3.106 (r2 = 0.966）and W = 0.0022L3.175 (r2 = 0.989), respectively. Our study provides the age structure and LWR in juveniles of two sturgeon species. [ABSTRACT FROM AUTHOR]

This study aimed to estimate the parameters of length‐weight relationships (LWRs) for six freshwater fish species that inhabit in the Xiangjiang River of Guangxi region, China. The specimens were sampled in April, July, and October 2014 and in January 2015 using electrofishing (CWB‐2000P, China; 12 V import, 250 V export) and traps (mesh size 8.5 mm; length 200 m) at five sampling sites. For each sampling site, a trap was settled on one nearshore zone of the river for 24 hr, and the electrofishing was applied within 30 min from downstream to upstream with 200 m long. Standard length was measured (be accurate to 0.1 cm) and total weight determined (be accurate to 0.1 g) after preservation in formaldehyde (10%). The values for the parameter b of the length‐weight relationships were estimated together with the coefficient of determination scores. In addition, this study provides a new tentative LWRs for the six species. [ABSTRACT FROM AUTHOR]

Since two large specimens of Chinese paddlefish Psephurus gladius were found unexpectedly in December 2002 and January 2003, a series of measures have been undertaken to attempt to save this critical endangered species. As a part of the rescue plan, a total of eight hydroacoustic and capture surveys were conducted in the upper Yangtze River between 2006 and 2013. Preliminary results from the first four surveys (2006-2008) were reported in 2009. The later four surveys were conducted in the same area and consisted of 578 setlines, 8 anchored setlines and 2003 drift net catches. A total of 1982 fish belonging to 38 species were captured. For the hydroacoustic surveys, a BioSonics echo sounder with a vertically down looking 199 kHz split-beam transducer was applied, both for data recording, and for guiding the capture trials by drift nets and setlines. Post processing applying automatic tracking identified 7217 single targets from the eight acoustic surveys. Body size was estimated from TS values of single targets. No P. gladius were captured. The acoustic data, however, revealed at least a few observations that are difficult to interpret as something other than large P. gladius. Although not conclusive, this gives hope that this species may still exist in the river. [ABSTRACT FROM AUTHOR]

Threadfin porgy Evynnis cardinalis is both a dominant fish species and an important fishing target in bottom trawl fisheries in the Beibu Gulf, South China Sea. It was listed as endangered (EN) in a recent International Union for Conservation of Nature (IUCN) red list. Despite its economic importance and endangered status, limited research on its biological characteristics and spatial-temporal distribution has been undertaken this last decade, creating uncertainty in current conservation and management. We analyse this species' spatial distribution characteristics using data from four seasonal bottom trawl surveys in 2014-2015, and report average catch per unit effort to vary seasonally, from 49.1 to 594.5 ind h -1 . Growth, mortality and sexual maturity are reported for four time periods based on data from bottom trawl fishery surveys over 1961-1962, 1998-1999, 2006, and 2014-2015. Length frequency distributions changed from bimodal to unimodal, and the female-to-male ratio increased. Mean body length and length at first maturity decreased, whereas the growth coefficient increased, indicating miniaturization, early sexual maturity and accelerated growth, respectively. We report sparid catch to have first exceeded maximum sustainable yield in 2001, and to have remained overfished from 2010 to 2015. Since the 1980s, low-trophic-level fishes such as E. cardinalis have replaced high-trophic-level fishes such as Crimson snapper Lutjanus erythropterus to become dominant species. As catches have increased substantially, these species have been faced with overfishing, driving the ecosystem into an unstable state., (© 2020 The Fisheries Society of the British Isles.)

The use of morphological characters and otolith weight as predictors of fish age has proven to be an efficient, objective and precise method, but studies were heretofore focused primarily on fast-growing fish species. In the present study, Belanger's croaker, Johnius belangerii (Cuvier, 1830), is presented as a model species for slow-growing fish where it is hypothesized that age has a significant effect on the otolith shape , and that the otolith weight has the potential to predict individual fish age as an alternative and objective method. Discriminant function analysis ( DFA) of shape variables and cross-validation were applied to a total of 359 sagittal otoliths in the age groups 0, 1 and 2. The shape variables demonstrated 64.1% correct age classification, and a 93.5% correct age classification with the inclusion of otolith weight in the discriminant function. Results show that a combination of shape variables and otolith weight work well in age determination of Belanger's croaker, and demonstrate its application potential for sciaenids that are distributed throughout the coastal waters of China. [ABSTRACT FROM AUTHOR]

We tested the use of otolith shape analysis to discriminate between species and stocks of five goby species ( Ctenotrypauchen chinensis, Odontamblyopus lacepedii, Amblychaeturichthys hexanema, Chaeturichthys stigmatias, and Acanthogobius hasta) found in northern Chinese coastal waters. The five species were well differentiated with high overall classification success using shape indices (83.7%), elliptic Fourier coefficients (98.6%), or the combination of both methods (94.9%). However, shape analysis alone was only moderately successful at discriminating among the four stocks (Liaodong Bay, LD; Bohai Bay, BH; Huanghe (Yellow) River estuary HRE, and Jiaozhou Bay, JZ stocks) of A. hasta (50%-54%) and C. stigmatias (65.7%-75.8%). For these two species, shape analysis was moderately successful at discriminating the HRE or JZ stocks from other stocks, but failed to effectively identify the LD and BH stocks. A large number of otoliths were misclassified between the HRE and JZ stocks, which are geographically well separated. The classification success for stock discrimination was higher using elliptic Fourier coefficients alone (70.2%) or in combination with shape indices (75.8%) than using only shape indices (65.7%) in C. stigmatias whereas there was little difference among the three methods for A. hasta. Our results supported the common belief that otolith shape analysis is generally more effective for interspecific identification than intraspecific discrimination. Moreover, compared with shape indices analysis, Fourier analysis improves classification success during inter- and intra-species discrimination by otolith shape analysis, although this did not necessarily always occur in all fish species. [ABSTRACT FROM AUTHOR]

Little is known about mercury (Hg) biomagnification in the subtropics, aquatic systems with high species diversity resulting in complex food webs. High atmospheric Hg emissions and ubiquitous reservoir fisheries may lead to elevated Hg bioaccumulation in Chinese freshwater fishes. However, stocking practices using fast-growing species can result in low fish total Hg (THg) concentrations. Here, we describe Hg transfer within the fish food web of a large subtropical reservoir, Qiandao Hu (Xin'anjiang reservoir) situated in eastern China. We measured food web Hg biomagnification and THg concentrations in 33 species of stocked and wild fishes. Mercury concentrations in most fishes were low, though we also found high Hg concentrations in wild top predators. The food web structure, assessed using stable isotopes of carbon (δC) and nitrogen (δN), demonstrated a high degree of omnivory and a long food chain. THg concentrations were highly correlated with fish δN values. The regression of logTHg against δN revealed the overall Hg biomagnification rate was low. This study shows that where long food chains exist in subtropical reservoirs, elevated Hg accumulation in top predators can occur despite a low Hg biomagnification rate. [ABSTRACT FROM AUTHOR]

This study quantified and compared hypoxia tolerance and swim performance among cyprinid fish species from rapid-, slow- and intermediate-flow habitats (four species per habitat) in China. In addition, we explored the effects of short-term acclimation on swim performance, maximum metabolic rate (ṀO2,max) and gill remodelling to detect habitat-associated patterns of plastic response to hypoxia. Indices of hypoxia tolerance included oxygen threshold for loss of equilibrium (LOE50) and aquatic surface respiration (ASR50), and critical oxygen tension for routine metabolic rate (Pcrit). Critical swimming speed (Ucrit) and ṀO2,max were measured under normoxic and hypoxic conditions after 48 h acclimation to normoxia and hypoxia, and gill remodelling was estimated after 48 h of hypoxia exposure. Both traditional ANCOVA and phylogenetically independent contrast (PDANOVA) analyses showed that fish species from rapidflow habitats exhibited lower LOE50 compared with fish from intermediate- and slow-flow habitats. Habitat-specific differences in Pcrit and Ucrit were detected using PDANOVA but not traditional ANCOVA analyses, with fish species from rapid-flow habitats exhibiting lower Pcrit but higher Ucrit values compared with fish from intermediate- and slow-flow habitats. Fish species from rapid-flow habitats were also characterized by less plasticity in swim performance and gill morphology in response to hypoxia acclimation compared with species from slow-flow habitats, but a greater drop in swim performance in response to acute hypoxia exposure. The study detected a habitat-specific difference in hypoxia tolerance, swimming performance and its plasticity among fish from habitats with different flow conditions, possibly because of the long-term adaptation to the habitat caused by selection stress. The PDANOVA analyses were more powerful than traditional statistical analyses according to the habitat effects in both hypoxia tolerance and swimming performance in this study. [ABSTRACT FROM AUTHOR]

The article presents a study on the use of hydroacoustic and gillnet sampling approach to examine the distributions and abundance of Gymnocypris przewalskii in Qinghaihu Lake, China. The study shows that G. przewalskii preferred deep-water locations, such as the sites with 24-27 meter depths. It reveals that the complete fishery closure in the lake was the optimal approach for recovery of the fish resource.

The article presents a study on temporal and spatial distribution of fishes in the middle reaches from Chenglingji to Yichang of the Yangtze River in China. The study aims to analyse the fish distribution on a spatial and temporal scale. It also discusses possible factors that might cause or could explain the regional distribution patterns, in an attempt to provide some reference data for further use in assessment research.

The aim of this study was to quantify the fish fauna in the Three Gorges Dam ( TGD) and assess the tendency for change as well as for any spatial and temporal distribution. Two types of echo-sounder equipment ( HTI Model 241 and Simrad EY60) were used to detect the fish density and fish spatio-temporal distribution. Eight surveys were conducted between 2006 and 2010, with the results showing that fish abundance in the Three Gorges Reservoir (TGR) increased yearly from 15.5 to 123 ind./1000 m3, a change apparently correlated with the corresponding increase in the reservoir water level. Horizontally, fish density increased from the lower reaches to the upper reaches. Fish preferred inhabiting the area around the Zhongxian section during winter and the Chongqing section in spring. Vertically, fish density was highest in the lower layer, followed by the middle layer. The difference in fish density in different water layers observed in spring was not as evident as in the winter. Fish target strength throughout the eight investigations showed a skewed distribution with respect to fish size. The overall increasing tendency of fish density and the spatio-temporal distribution of fish species were closely related to the water level of the TGR during the impounding period. Other influencing factors included water flow rate, water depth, reservoir shape, habitat type, and protection policy. [ABSTRACT FROM AUTHOR]

Hydroacoustic surveys were performed in an oxbow lake (Lake Laojianghe, China) along the Yangtze River. The study took place during the day and night in October 2012 using the Simrad EY60 split beam echo sounder. A clear day-night difference in fish densities was observed in selected transect areas. The mean density estimate at night was three times higher than during the day, while at night densities were similar in the two adjacent areas. Significantly positive relationships were found between fish density and average depth for the night and daytime transects, however, the regression slope for the daytime density estimates was much smaller than for the surveys at night. Small fish dominated the acoustic size structure during both day and night, but were more accessible at night. The average biomass estimate from the daytime transects was nearly 60% lower than those from the corresponding night transects. These results indicate that an entire lake estimate of a fish population may be severely biased if fish tend to aggregate temporarily in the bottom or littoral zone or display diurnal behaviour. The conclusion is that acoustic sampling in Lake Laojianghe is best done at night. Diel differences in the lake should be further investigated by carrying out additional day-night comparison experiments and also by using control catches. [ABSTRACT FROM AUTHOR]

This study presents a method of combining hydroacoustics and hydraulic data to estimate fish preference in a large and rapidly flowing river system. A typical middle reach of the Yangtze River with three islands and two wandering sections was taken as the research object to interpret schools of fish with different sizes and densities for their preference of physical habitat features such as water depth and velocity by using Geographic Information Systems ( GIS). Fish density and size were determined based on the hydroacoustic data, and hydraulic variables were simultaneously collected using an Acoustic Doppler Current Profiler ( ADCP) system. Results show that fish sizes are correlated with water depth and velocity and that fish density correlated only with water depth. Small fish prefer high water depth average velocity ( WDAV), lower vertical average velocity ( VAV), deep water, as well as a wide depth and velocity range; large fish prefer low WDAV, high VAV, deep water, and a narrow depth and velocity range. High fish densities appear around islands and areas with deep water. The results show that large fish may be sufficiently strong enough to select their preference for water depth and velocity. Areas of deep water can provide broad velocity diversity and more space to accommodate fish. The island littoral zone could provide a variety of habitats with a diverse pattern of depth and velocity for fish. This study provides a contributive method for the field habitat suitability assessment for fish. [ABSTRACT FROM AUTHOR]

Consumption of fish and aquatic products is considered to be the main pathway of human exposure to methylmercury (MeHg). To assess human health risk through seafood consumption in a coastal area of Guangdong Province, South China, a total of 518 seafood samples (including fish, shrimp, crabs, and mollusks) were collected from 11 coastal cities for total mercury (THg) analysis. The THg concentrations varied significantly among different seafood groups and ranged from 0.11 to 317 ng/g (with a mean of 37.2 ng/g). The THg concentrations were relatively low compared with fish from Europe and North America, and no samples exceeded the national limit recommended by the Standardization Administration of China (0.5 ng/g wet wt). The ecological functional groups and cultured styles have significant effects on THg concentrations in the fish tissue. The median of probable daily intakes (PDIs) of MeHg via seafood consumption ranged from 42.6 to 71.4 ng/g for different age groups, with fish contributing the major portion (84%). The results indicated potential health risks associated with seafood consumption for the general population in the coastal area of Guangdong Province, South China. Environ. Toxicol. Chem. 2013;32:541-547. © 2012 SETAC [ABSTRACT FROM AUTHOR]

Seasonal water-level changes in floodplain lakes can induce variations in primary and secondary production, thus affecting trophic interactions. In this study, we tested the latter by studying size- and temporal hydrology-related shifts in the diet of shortjaw tapertail anchovy Coilia brachygnathus (Actinopterygii, Engraulidae) from Lake Poyang. During the wet season, δC values ranged from −28.2‰ for small anchovies to −24.6‰ for larger individuals, but δN ranged from 18.9‰ for smaller fish to 12.4‰ for larger fish. Significant C-enrichment and N-depletion occurred with increasing size, revealing that different carbon sources were used as the fish grew. Given the high hydrologic fluctuation levels, significant differences in δC values were observed among larger anchovies between seasons, indicating a temporal dietary shift. Anchovies fed primarily on shrimp and fish during the low-water season despite the predominance of zooplankton during the two seasons studied, which indicated increased piscivorous reliance. C. brachygnathus exhibited higher δN values during the wet season because the food items were N-enriched. Human waste brought by floods could be another possible interpretation. Considering C. brachygnathus is an important link between plankton production and higher piscivorous trophic levels, changes in the species are expected to affect the functioning of lake food webs along the trophic pathway. [ABSTRACT FROM AUTHOR]

Silver carp, Hypophthalmichthys molitrix, is one of the four major fishes in China for fishing and aquaculture. The Yangtze River and associated waterbodies are important home to silver carp. In this study, we collected 135 otoliths of juvenile silver carp from the two rivers and the Poyang Lake, and analyzed for stable oxygen and carbon isotope ratios (δO and δC). The isotopic data and correlation of δO versus δC showed a clear separation and significant differences ( p < 0.001 for both δC and δO) between otoliths from the Ganjiang River and the Yangtze River at δO values around −10‰. The Poyang Lake samples were overlapped with those of the Ganjiang River, but distinctly different from the Yangtze River samples. These isotopic signatures agree well with the previous genetic investigation results that there are marked distinctions between one population in the Ganjiang River and the other in the Yangtze River, and the Poyang Lake population belongs to the Ganjiang River rather than to the Yangtze River. Thus we concluded that stable isotope analyses of otoliths can be effectively used to study natal sources and stock differences of silver carp. [ABSTRACT FROM AUTHOR]

The concentration of methylmercury (MMC) and total mercury (TMC) in marine fishes (five species) frequently consumed in the coastal areas of Zhejiang province, China, was determined. The method of high-performance liquid chromatography–atomic fluorescence spectrometry (HPLC-AFS) with the microwave-assisted extraction was used for the MMC determination. TMC was analysed by a direct mercury analyser. MMC and TMC concentrations in five fish species ranged from 53 to 158 µg kg−1 and 60 to 172 µg kg−1, respectively. The proportion of MMC levels in TMC was greater than 80%. The highest MMC and TMC levels were found in Hairtail. [ABSTRACT FROM AUTHOR]