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Characteristics of trace element in the otolith of Sardina pilchardus in waters near Mauritania 2022, 44(4): 385.  Abstract ( 121 )   PDF (1867KB) ( 407 )   Characteristics of trace element in the otolith of  Sardina pilchardus in waters near Mauritania SONG Liming1,2, ZHOU Wang1, WANG Di1, Ebango Ngando Narcisse1 (1. College of Marine Sciences, Shanghai Ocean University, Shanghai201306, China;  2. National Engineering Research Center for Oceanic Fisheries, Shanghai Ocean University,Shanghai201306, China) Abstract: Sardine (Sardina pilchardus) resources play an important role in the West African fisheries and have high economic value. Mauritania waters is located in the intersection area of Guinea warm current and Canary cold current, with strong upwelling and high primary productivity. It is one of the important fishing grounds in the Northwest African sea area.At present, most of the studies about sardines otolith in the Mauritanian waters are focused on the otolith morphology and age identification, and studies of sardines otolith microchemical in Mauritania waters are mainly used for species identification.In the Mauritania coastal area,the migration pattern of sardine is related to the seasonal changes of upwelling systems and the SenegalMauritania warm front. Sardine spawns all the year round in the Mauritania coastal area, the dominant spawning season is from October to December, and from April to May of the following year.To study the characteristics of trace element of sardine in waters near Mauritania will further understand the habitat of sardine, so as to further develop, maintain and manage small pelagic fishery resources such as sardine. The content of fish otolith elements is affected by the habitat. The habitat can be studied by analyzing the content ratio of fish otolith elements. To better understand the characteristics of trace element in the otolith of sardine in waters near Mauritania, 219 sardines were collected on board the purse seiner from the waters near Mauritania (20°10′N21°10′N,17°10′W17°40′W) from Oct. to Dec. , 2018.The fork length of the samples was (15.24±6.76) cm and the body weight was (103.51±23.48) g.The gender was identified. Fifty eight (25 male, and 33 female)otoliths were selected and polished until the daily ring could be identified. The numbers of daily ring were measured under the microscope. The numbers of daily ring were counted independently by three qualified individuals and identified according to the numbers of broad bands or narrow bands. The otoliths transversely sectioned slices were sonicated in deionized water. The otolith element content in the core region, oneyear region and twoyear region was measured by laser ablation inductively coupled plasma mass spectrometry (LAICPMS) to analyze the ratio differences of otolith element content among different ages and discuss the habitat environment differences among different ages of sardine in waters near Mauritania. The experiment was conducted at Wuhan Shangpu Analysis Technology Co., LTD. During analysis a spot size of 44 μm was used for cell removal. Helium (0.7 L·min-1) was used as a gas sample and argon (0.8 L·min-1) was thus added to the gas flow for sensitivity adjustment. For the calibration of elemental concentration various external methodologies were considered and quantified with certified reference materials (NIST 610, BCR, BIR, BHVO, MACS3and ZS). The instrument parameters were calibrated again after measured 35 samples.The range of the otolith daily ring was from 344 to 789 for 58 samples.The numbers of fish in 01 year old, 12 years old, and more than 2 years old are 2, 40, and 16 respectively, the dominating age was 12 years old.Wilcoxon test was used to analyze the otolith trace elements content of different genders and ratios of dominant elements (Na, Sr, Fe, Mg, Ba) content to Ca content in different measuring points of sardine otolith. Results showed that: 1) A total of 44 elements were detected in the otolith of sardine, mainly including Ca, Na, Sr, Fe, Mg, Ba, etc; 2) There was no significant difference in the ratios of otolith dominant elements content to Ca content between male and female in waters near Mauritania (P>0.05); 3)There was no significant difference in the ratios of Na, Sr, Mg, Ba content to Ca content between the otolith core region and oneyear region of sardine in waters near Mauritania (P>0.05). There were significant differences in the ratios of Na, Sr, Mg, Ba content to Ca content between the oneyear region and twoyear region and between the twoyear region and fringe region (P<0.05); 4) There was no significant difference in the ratio of Fe content to Ca content between the oneyear region and twoyear region or between the twoyear region and fringe region (P>0.05). This study suggests that: 1) The female and male sardine in waters near Mauritania have the same habitat environment and migratory route. When the migratory life history is studied, they don’t need to study separately; 2) There is no habitat environment difference between 0yearold and 1yearold sardine in waters near Mauritania, but there are habitat environment differences between 1yearold and 2yearold, and between 2yearold and capture time for sardine in waters near Mauritania. Sardines might stay in the shallow waters off Cabo Blanco and there is no migration from age 0 to age 1. There are seasonal migratory movement for sardines from age 1 to age 2 and from age 2 to the capture time.In the summer and fall, sardines might migrate along the coastal area of Western Sahara to the north, and to the south in the winter and spring; 3) Sr and Ba element contents in the otolith of marine fish associate with fish habitats. Sr∶Ca and Ba∶Ca are environment fingerprint elements for researching the life cycle of the fish; 4) Na∶Ca and Mg∶Ca ratios can also be used for the study of sardine habitat change at different ages, but Fe∶Ca ratio is not applicable to study the sardine habitat change in the waters near Mauritania.Na content of the fish otolith relates to the water temperature and Mg content of the fish otolith relates to water temperature and salinity. The element composition in the waters near Northwest Africa of the Atlantic Ocean is influenced by the mine dust from the Sahara Desert. Iron ore resource is rich in Mauritania, which may lead to the distribution of Fe content even in this sea area, and Fe content in sardine otolith fluctuates little in the process of sardine growth. Keywords: Sardina pilchardus; otolith; trace element；Mauritania waters  Related Articles | Metrics

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Genetic structure of Sthenoteuthis oualaniensis population in the east Indian Ocean and South China Sea 2022, 44(4): 396.  Abstract ( 123 )   PDF (2198KB) ( 365 )   Genetic structure of Sthenoteuthis oualaniensis population  in the east Indian Ocean and South China Sea ZHAO Yan1, WANG Congcong1,2,3,4,5, LIU Bilin1,2,3,4,5, LIN Longshan6, LI Yuan6 (1.College of Marine Sciences, Shanghai Ocean University, Shanghai201306, China; 2. Key Laboratory  of Sustainable Exploitation of Oceanic Fisheries Resources, Ministry of Education, Shanghai201306, China;  3. National Distantwater Fisheries Engineering Research Center, Shanghai Ocean University, Shanghai201306,  China; 4. Key Laboratory of Oceanic Fisheries Exploration, Ministry of Agriculture and Rural Affairs, Shanghai201306,  China; 5. Scientific Observing and Experimental Station of Oceanic Fishery Resources, Ministry of Agriculture and  Rural Affairs, Shanghai201306, China; 6. Third Institute of Oceanography, Ministry of  Natural Resources, Xiamen Fujian361005, China) Abstract: Purpleback flying squid, Sthenoteuthis oualaniensis, widely distributed in tropical and subtropical waters such as the equator in the Indian and Pacific oceans. The species possesses fast growth rate, strong reproductive capacity and short life cycle, occuping an important position in the marine ecosystems.  Sthenoteuthis oualaniensis is not only the predator of zooplankton, lanternfish and other organisms, but also the food source for many marine predators, therefore, the changes of its resources have a profound impact on the entire ecosystem. At the same time, it has a relatively high resource abundance.  Sthenoteuthis oualaniensis possesses a large resource in the Northwest Indian Ocean and the South China Sea, with high potential commercial value. It is gradually becoming one of the important fishery species. As the basic unit of fishery management, researches on the population structure of Sthenoteuthis oualaniensis are crucial to the rational evaluation and management of fishery resources, and it is also important for the scientific management and rational maintenance of Sthenoteuthis oualaniensis fishery resources and genetic resources reference. Due to the complex current changes in the equatorial waters of the East Indian Ocean, researches on the genetic structure of Sthenoteuthis oualaniensis have not yet been reported. Whether there are genetic differences between groups still needs further researches. Population genetics are helpful in understanding the population structures and genetic variations in this sea area. The South China Sea is an important economic sea area in China, and there are important fishery resources available for exploitation, among which Sthenoteuthis oualaniensis resources are the most abundant species. It should be further developed and utilized. Further understanding of the genetic structure of Sthenoteuthis oualaniensis population in the South China Sea is extremely important for its’ sustainable development and utilization in the South China Sea. Whether there are genetic differences between Sthenoteuthis oualaniensis of the East Indian Ocean equatorial waters and the South China Sea, and whether genetic differences are significant also require further study. Therefore, the mitochondrial cytochrome b gene (Cytb) marker was selected in this paper to analyze the genetic structures, genetic differences, genetic diversities, and population historical dynamics among four Sthenoteuthis oualaniensis populations in the East Indian Ocean and South China Sea. This would provide scientific basis for the management and utilization of Sthenoteuthis oualaniensis fishery resources, as well as the protection of genetic diversities. This research was conducted to understand the population genetic structure of Sthenoteuthis oualaniensis from the East Indian Ocean and the South China Sea, and to rationally manage the resources of squid fishery. The cytochrome b (Cytb) sequences of 120 mitochondrial DNA from four subpopulations of Sthenoteuthis oualaniensis were measured. These samples were collected from the north and south of the East Indian Ocean and the South China Sea. Cytb gene marker primers were used for the PCR amplification and sequencing, and a total of 120 Sthenoteuthis oualaniensis samples were genetically analyzed in four populations of the eastern Indian Ocean in the northern equator, southern and northern South China Sea. The results showed that the total diversities of haplotype and nucleotide were 0.273 32 and 0.981, respectively. The highest haplotype diversity of the group from the north of the South China Sea was 0.989, while that of the group from the south of the South China Sea was only 0.306 60. The results of the haplotype network diagram and phylogenetic tree showed that the genetic differentiation between populations of the East Indian Ocean and the South China Sea was significant. The analysis result of molecule variance indicated that 54.90% of population variation came from different groups, and the genetic differentiation was significant (P<0.01). The genetic variation rate within the population was 45.10%, and the genetic variation caused by geographical isolation was slightly higher than the variation of individuals within the population.The analysis of Fst value showed that Fst value between two groups from the north and south of the East Indian Ocean was 0.085 88, and Fst value between two groups from the north and south of the South China Sea was 0.025 36. These results indicated that the indistinctive genetic differentiation existed between two groups from north and south of the South China Sea, while the differences of the genetic differentiation between two groups from north and south of the East Indian Ocean were small. The frequent ocean activities of Sthenoteuthis oualaniensis in both sides of the East Indian Ocean were the main factor leading to the genetic differentiation in the north and south of the East Indian Ocean. While the geographical isolations between the East Indian Ocean and the South China Sea might be the main reason causing the prominent genetic differentiation between two geographical groups. The neutrality test results of the population in the northern Eastern Indian Ocean showed a very significant negative value (Fs=-26.568 09, P<0.01), and the nucleotide unpaired distribution map showed a significant undirected peak, which speculated that the population might experience a historical population expansion event . In conclusion, the two groups in the East Indian Ocean and the South China Sea were independent, therefore, they should be regarded as two independent units. Through the study of Cytb gene of 120 individuals in the north and south equatorial waters of the East Indian Ocean, the southern and northern waters of the South China Sea, this study revealed that there was a significant genetic differentiation between the East Indian Ocean equatorial sea area and the South China Sea area, which should be regarded as two independent groups in fishery management. The populations in both sides of the equator in the East Indian Ocean has moderate genetic differentiation, and the addition of Sthenoteuthis oualaniensis samples in the waters of the Strait of Malacca could preferably verify the speculation in this paper. The Cytb gene fragments used in this study could only reflect the genetic differentiation characteristics of the female parent, and there were certain differences in the evolution rate of different gene fragments and the phylogenetic information displayed. In the future, it is necessary to integrate other gene fragments or genomic DNA data more comprehensively. Moreover, in the future, morphological data information could be added, and combined with the population structure information reflected by the morphology, a more indepth understanding of the population genetic structure of Sthenoteuthis oualaniensis could be obtained. Keywords: East Indian Ocean; South China Sea; Sthenoteuthis oualaniensis; cytochrome b gene; population genetic structure Related Articles | Metrics

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Effect of voluntary restriction zone on Antarctic krill fishery and fishing ground distribution in the Antarctic Peninsula 2022, 44(4): 409.  Abstract ( 88 )   PDF (3055KB) ( 378 )   Effect of voluntary restriction zone on Antarctic krill fishery and  fishing ground distribution in the Antarctic Peninsula DONG Sisong1,2, ZHU Guoping1, 2, 3, 4 (1. College of Marine Sciences, Shanghai Ocean University, Shanghai201306; 2. Center for Polar  Research, Shanghai Ocean University, Shanghai201306; 3. Polar Marine  Ecosystem Lab, Key Laboratory of Sustainable Exploitation of Oceanic  Fisheries Resources, Ministry of Education, Shanghai Ocean University, Shanghai201306;  4. National Engineering Research Center for Oceanic Fisheries, Shanghai201306) Abstract: Antarctic krill (commonly refers to Euphausia superba) is a key species in the Southern Ocean ecosystem. Its huge biomass has tremendous potential for fishery exploitation. With the development of krill fishery, the total catch has exhibited an increasing tendency, and the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) conventional area subarea 48.1, a hotspot for the krill fishery, has been closed in recent years due to reaching the trigger level. The areas around the Antarctic Peninsula are also inhabited for protection of vast numbers of penguins and seals. To better conserve krill resources and the predators depending on krill for food, the Association of Responsible Krill Harvesting Companies (ARK), a group of 90% of the world’s krill fishery companies, has agreed to and implemented voluntary restriction zones (VRZs) for krill fisheries in this area, starting in 2019. The VRZ requires krill fishing vessels to voluntarily restrict fishing activities in some areas during the summer and to reduce their access in other seasons, except for a failed searching for krill resource outside the VRZ, to reduce the potential impact of krill fishing activities in the areas around the Antarctic Peninsula due to competition between fishing and penguins for krill in the area. The implementation of the VRZ has had a significant impact on krill fishery and the distribution of fishing ground, and this change is bound to have an unpredictable impact on the sustainable development of krill fishery, as well as further affecting the decisionmaking of krill fishery companies. To understand the impact of the VRZ establishment and the potential future trend of VRZ enlargement on krill fishery and fishing ground selection, based on the existing VRZ, this study defines the boundary of the simulated restriction zone by extending 20 km, 30 km, and 40 km from the shoreline off the Antarctic Peninsula and the South Shetland Islands, respectively. The Bransfield Strait region is divided into four areas near the Antarctic Peninsula: AP20 (from the Antarctic Peninsula shoreline to the 20 km simulation line), AP30 (from 20 km to 30 km off the Antartic Peninsula), AP40 (from 30 km to 40 km off the Antarctic Peninsula), and BS (40 km off the Antartic Peninsula). The South Shetland Islands VRZ is divided into SSI20 (from the South Shetland Islands shoreline to the 20 km simulation line), SSI30 (from 20 km to 30 km off the South Shetland Islands), and SSI40 (from 30 km to 40 km off the South Shetland Islands), and NSSI (the open waters north of the restriction zone of the South Shetland Islands). The trawling locations and catch of krill trawler Furonghai owned by Liaoning Pelagic Fisheries Corporation around the Antarctic Peninsula from January to May 2017—2020 is used for the analysis in this study and the catch per unit effort (CPUE) is calculated to be an indicator of the vessel’s fishing efficiency. The area with high fishing efficiency can be considered as the core fishing ground. The fishing grounds in CCAMLR subarea 48.1 is divided into eight simulated restricted zones (MRZ). The spatial and temporal distribution and changes in fishing catch and fishing efficiency in different areas before and after the establishment of VRZ are analyzed.Results show that most of the fishing locations are concentrated in the BS near the Antarctic Peninsula north shelf during these four years, while the number of nets near the South Shetland Islands is low. With the establishment of the VRZ, the number of nets in the inshore off the South Shetland Islands declines significantly, while the number of nets in the NSSI but outside the VRZ increases. Following the establishment of the VRZ, krill fishery’s core fishing grounds shift to the BS, and the fishing efficiency in the BS is higher than that in other areas near the South Shetland Islands. There is an overall decreasing tendency of fishing efficiency and a greater negative influence on the seasonal catch peak in January and February. To reduce the impact of the VRZ on fishing grounds selection, no fishing vessel visits the Antarctic Peninsula in January and February, instead moving to the South Orkney Islands to launch the new fishing season. The VRZ and MRZ already cover a large portion of the Gerlache Strait, the northwest and north area off the South Shetland Islands, and parts of the Bransfield Strait, where krill fishery is much efficient. Krill fishing vessels will have less time available to fish in subarea 48.1 during summer if fishery management develops with the assumed MRZ, and the fishing grounds will be less selective. If conservation measures are implemented around the years in the future, subarea 48.1 will be too low in revenue for the fisheries to be exploitable. The transport mechanisms of krill stock is not generally known, and the potential impacts of krill fishery on predators are not fully demonstrated. The krill fishery has provided the CCAMLR with a wealth of basic scientific data for the development of conservation measures and has contributed to the study of the Southern Ocean environment, although overly harsh management of fishery may have a negative effect on subsequent scientific research. The current VRZ has led to an overconcentration of krill fishery in the Bransfield Strait for a short period, and this highdensity fishing behavior in small areas might lead to excessive fishing effort in hotspots, which in turn can have a greater impact on krill and their predators. To cope with more stringent fisheries management in the future, it’s suggested to develop professional krill fishing vessel with continuous pumping technology to improve fishing ground exploitation and increase fishing efficiency, while lowering operation costs. It’s also suggested to strengthen scientific research and international cooperation to enhance our position in krill fisheries internationally. Keywords: Antarctic krill; fishing ground; fishery management; voluntary restriction zone Related Articles | Metrics

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Catch comparison of electric pulse and beam trawl fishing in the East China Sea 2022, 44(4): 421.  Abstract ( 106 )   PDF (2022KB) ( 367 )   Catch comparison of electric pulse and beam trawl  fishing in the East China Sea LI Huiyu1,2, Zhang Yi1,2, DAI Yang1,2, LIU Zunlei1,2 (1. East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences,Shanghai200090, China;  2. Key Laboratory of East China Sea Fishery Resources Exploitation and Utilization, Ministry of  Agriculture and Rural Affairs, Shanghai200090, China) Abstract:  Shrimp beam trawl has started since the 1980s in the East China Sea, and electric pulse trawl was used in early 1990s because of its increased catch and reduced fuel cost. The principle of electric pulse trawl is to energize by a pulse generator, which generates a pulse electric filed at the net mouth, then the shrimp buried is electrically stimulated and becomes susceptible for capture. At the end of 1990s, the heavy use of pulse trawling caused subsequent overfishing and further biomass depletion of the fisheries resources, and then was banned in 2001. However, its considerable economic returns led to the frequent illegal use of electrofishing. To assess the harmful effects of electrofishing and to quantify its damage on fishery resources, paired samplings of beam trawl and multivariate statistical software PRIMER were applied. Pulse trawl (electrofishing) and beam trawl (control trawl) hauled parallelly at a distance of 0.150.2 n mile with 23 kn towing speed from July 1st to 7th, 2019, off the East China Sea (32°00′32°12′N、122°30′123°18′E) were studied. Then the catch effectiveness and composition between electrofishing and control trawl were compared. Analysis of similarity (ANOSIM) test of the composition dissimilarity between fishing gears and similarity percentage analysis (SIMPER) estimated the contribution of main species to each group. Nonparametric (MannWhitney U test) test determined differences in catch rate between day and night and between fishing gears. Results showed significant differences in composition and catch rate between gears and diel period. Electrofishing produced lower species richness (73 species, including 46 fishes, 16 crustaceans, 11 cephalopod) than control trawl (80 species, including 49 fishes, 21 crustaceans, 10 cephalopod) with 58 sharing species. The catch of electrofishing was mainly composed of fishes (49.7%) and crustaceans (47.3%) while control trawl with fishes (58.9%). The species Chelidonichthys spinosus and Portunus trituberculatus dominated (> 75% by weight) in both of the two fishing gears, while the six shrimps（Trachypenaeus curvirostris and Parapenaeopsis hardwickii etc.）only occupied 2.8%3.2% of the total catch. The result of SIMPER indicated that the dissimilarity of catch composition between electrofishing and control trawl was 43.85% (P= 0.001), and species P. trituberculatus, C. spinosus, Octopus ocellatus, Pleuronichthys cornutus, Paraplagusia japonica, Johnius grypotus and Argyrosomus argentatus showed relatively high dissimilarity contributions (>4%). For diel catch composition comparison, ANOSIM showed that significant differences were obtained by both electrofishing (P=0.001) and control trawl (P=0.001). Electrofishing captured more species at night (60) than at day (57) with 40 sharing species, while control trawl captured the same species (66) at day and night with 51 sharing species. The diel dissimilarity of catch composition was 44.60% by electrofishing and 40.73% by control trawl, and species P. trituberculatus, C. spinosus, J. grypotus, P. cornutus, O. ocellatus and A. argentatus showed high dissimilarity contributions (>4%) with different degrees of contribution to each group. Catch rate was 45 386 g ·h-1 by electrofishing and 24 945 g ·h-1 by control trawl. Electrofishing showed 81.9% catch rate increment, indicating more effective catch than control trawl (MannWhitney U test, P<0.001). Catch rate in fishes, crustacean and cephalopod was 22 547 g ·h-1，21 476 g ·h-1，1 363 g ·h-1, respectively by electrofishing and 14 692 g ·h-1，9 318 g ·h-1，934 g ·h-1, respectively by control fishing, showing significant differences in fishes (53.5% increment) and crustacean (130.5% increment) (MannWhitney U test, P<0.001). The remarkable change of catch rate by electrofishing was observed in species C. spinosus, P. trituberculatus, P. cornutus and T. curvirostris. Catch rate of C. spinosus was 16 899 g ·h-1 and 10 746 g ·h-1，respectively by electrofishing and control trawl, showing 57.3% increment (P<0.001). Catch rate of P. trituberculatus was 19 496 g ·h-1 and 8 026 g ·h-1，respectively by electrofishing and control trawl, showing 142.9% increment (P<0.001). And the species P. cornutus showed significant increment of catch rate (P<0.05), while species T. curvirostris displayed significant decrement of catch rate by electrofishing (P<0.05). Diel comparison of catch rate revealed significant differences for both electrofishing and control trawl. Night time catch rate (55 085 g ·h-1) was more efficient than daytime (35 688 g ·h-1), with 54.4% increment by electrofishing (P<0.001). For control trawl, nighttime catch rate (28 330 g ·h-1) was more efficient that daytime (21 560 g ·h-1) with 31.4% increment (P<0.05). The catch rate of fishes was 14 540 g ·h-1 at day and 30 555 g ·h-1 at night by electrofishing, while it was 11 666 g ·h-1 at day and 17 719 g ·h-1 at night by control trawl. There was a significant diel increment of catch rate by both electrofishing (110.1%) and control trawl (51.9%) (P<0.001). The diel variation of catch rate showed that there were significant differences in species C. spinosus, J. grypotus, T. curvirostris and P. hardwickii. Compared with daytime, nighttime fishing efficiency of the four species increased by 154.1%,494.9%,61.1%,134.2%, respectively for electrofishing (P<0.05), and 60.3%,565.2%,138.5%,39.7%, respectively for control trawl (P<0.05). From the results, it concluded that electrofishing showed more efficientcy in catch, especially at night. Differences in species richness, species composition and catch rate may be determined by the combined effect of differences in electric (electrofishing) and mechanical (control trawl) stimulations. It was also probably due to the differences in diel period, species, behavior and physiological condition of species. Though high efficiency by electrofishing, the percentages of shrimp catches were still very low, which indicated that the catch structure was not improved at all. Electrofishing, in fact, has no significant selectivity for target species (shrimp), but displays more harmful destruction to the demersal fishes and crab in the East China Sea.  Keywords: East China Sea; electrofishing; beam trawl; catch composition, catch rate Related Articles | Metrics

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Stock assessment of Collichthys lucidus in the Pearl River Estuary in data-limited conditions 2022, 44(4): 435.  Abstract ( 102 )   PDF (1555KB) ( 383 )   Stock assessment of Collichthys lucidus in the  Pearl River Estuary in data-limited conditions SHI Dengfu1,3， ZHANG Kui1,2， CAI Yancong1， XU Youwei1，  SUN Mingshuai1， XU Shannan1， ZHU Jiangfeng1， CHEN Zuozhi1, 2  (1. Key Laboratory for Sustainable Utilization of Opensea Fishery, Ministry of Agriculture and Rural Affairs,  South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Guangzhou510300, China;  2. Southern Marine Science and Engineering Guangdong Laboratory（Guangzhou）, Guangzhou511458, China;  3. College of Marine Sciences, Shanghai Ocean University, Shanghai201306, China) Abstract: Fishery stock assessment is a basic component of modern management to maintain sustainable fisheries exploitation. Traditional assessment methods always require a large amount of statistical data, e.g., catch, abundance index, and even age structure. Due to limited funding and data for such surveys, only 1% of fish stocks around the world have been systematically assessed. Therefore, it is difficult to assess most fishery resources using traditional methods based on the maximum sustainable yield (MSY) principle. In recent years, stock assessment using limited data has become a focus issue in the field of fishery resources. Owing to the ease and objectivity of fish length, the evaluation models based on body length data has gained wide attention for data limited fisheries, including traditional electronic lengthfrequency analysis (ELEFAN) and lengthbased Bayesian biomass estimation (LBB). The big head croaker (Collichthys lucidus) is a commercially important smallsize fish widely distributed in the northwestern Pacific, from southern Japan to the inshore waters of Vietnam, with the majority of its distribution in Chinese waters. This species is smallsized, matures at age 1 yr, and has high fecundity and strong adaptability to salinity. It presents estuarineresident life history and can make a short distance migration from deep to shallow water areas in breeding seasons. Due to overfishing, the stocks in traditionally fished estuaries (e.g., Yangtze River Estuary and Minjiang River Estuary) have dramatically declined. It has important economic value and ecological effect on the ecosystem of Pearl River Estuary. In recent years, with the rapid development of coastal marine development and social economy, the fish resources in the Pearl River Estuary have been severely damaged due to the intensive fishing by human beings and the destruction of habitat by channel dredging. At present, the development and utilization status of  C. lucidus resources in the Pearl River Estuary is not clear. In this study, C. lucidus was sampled from the Pearl River Estuary from 2018 to 2019, and was conducted by bottom trawl fishing boat. The survey was conducted seasonally, namely spring 2018 (March, April), summer (August), autumn (September, October, November) and winter 2019 (December 2018, January and February 2019). The“Yuedongguanyu 92008” bottom trawl fishing boat was used for all surveys, with a length of 21.68 m, a main engine power of 143 kW, and a gross tonnage of 118 t. The bottom trawl nets used in the survey had an upper mesh length of 36 m, a mesh mouth of 5 cm, a cod end mesh size of 3 cm, and a total net length of 50 m. Biological data such as body length, body mass and gonadal maturity were determined from the collected samples. A total of 853 C. lucidus individuals were measured in this study. Based on the length data, we used ELEFAN and LBB methods to study the exploitation status of C. lucidus. Results showed that the body length frequency distribution was obviously unimodal and proportion of individuals in 91110 mm was the highest. The asymptotic lengths based on ELEFAN and LBB method were 160 mm and 156 mm, respectively. The exploitation rates were 0.55 and 0.68, respectively. The estimated total mortality coefficient was 4.81 based on lengthconverted catch curve, and the estimated nature mortality coefficient was 2.16 using Pauly’s empirical equation. Based on the LBB method, the estimated optimal fishing length was 100 mm, and B/BMSY was 0.57. Comparing with the stock in 1980s, although the growth coefficient and the exploitation rate reduced, the biomass level estimated by LBB was below 1, indicating that this stock had been overfished. Although both two methods were based on the assumption that fish growth followed the Von Bertalanffy growth equation, there were completely different computational procedures in the parameter evaluation process. The ELEFAN method obtained the optimal solution of the two parameters L∞ and K by finding the maximum value of the “explained sum of peaks”, and then estimated the values of other parameters through empirical formulas and evaluation curves. Management parameters such as development rate were obtained. The LBB simplified the data requirements, replaced the real values of M, F, and K in the form of M/K and F/K, and determined the L∞, M/K and F/K values through the catch function. Therefore, different evaluation methods resulted in differences in the evaluation results. According to the evaluation results of population parameters of C. lucidus in different sea areas in China, the natural mortality coefficient of C. lucidus in Pearl River Estuary was the highest, which might be caused by the difference of water temperature in different sea areas. According to Pauly’s empirical formula, the higher the water temperature in the habitat area, the higher natural mortality coefficient. The asymptotic body length of Minjiang River Estuary population was the largest, and the growth coefficient of populations in Minjiang River Estuary and Yangtze River Estuary were significantly lower than that of Pearl River Estuary, also due to water temperature. The higher the habitat water temperature was, the faster the metabolism of fish was, the faster the growth rate was, and the larger the growth coefficient was. The difference of asymptotic body length and exploitation rate in different sea areas might be caused by the difference of fishing intensity. Since 1999, the Chinese government has started to control the number of fishing boats and the power of fishing boats in the South China Sea, adjusted the fishery production structure, and vigorously built artificial reefs and implemented enhancement and releasing. This has reduced the intensity of development of fishery resources in the South China Sea. Studies have shown that the fishery policies in the South China Sea in recent years have had a positive impact on the changes in fish biological characteristics, such as the recovery of the average body length and first sexual maturity body length of Evynnis cardinalis in the Beibu Gulf. In this study, the changes in mortality parameters from the 1980s to the present show that the resources of C. lucidus in the Pearl River Estuary have not recovered, and even suffered from high fishing pressure, which indicates that  the current resources have not been recovered. Therefore, in order to conserve and restore Collichthys lucidus resource, it is recommended to implement precautionary fishery management measures such as quota fishing and protected areas on the basis of traditional measures, including strict minimum mesh size, access to gears, and control of fishing effort.  Keywords: Pearl River Estuary；Collichthys lucidus；resource exploitation status；ELEFAN；LBB method Related Articles | Metrics

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Microbial diversity and active substances of some fungi in surface seawater of the northern South China Sea 2022, 44(4): 446.  Abstract ( 107 )   PDF (4070KB) ( 386 )   Microbial diversity and active substances of some fungi  in surface seawater of the northern South China Sea LI Han1,2， FAN Chengqi2,3， CHEN Sha1,2,， ZHOU Jin2,4，  ZHOU Junfang2,5， LU Yanan2,3， MA Liyan2， TIAN Xiaoqing1,2,3 (1. College of Food Science, Shanghai Ocean University, Shanghai201306; 2. East China Sea Fisheries Research Institute,  Chinese Academy of Fishery Sciences, Shanghai200090; 3. Key Laboratory of Oceanic and Polar Fisheries, Ministry of  Agriculture and Rural Affairs, Shanghai200090, China; 4. Key Laboratory of East China Sea Fishery Resources  Exploitation, Ministry of Agriculture and Rural Affairs, Shanghai 200090, China; 5. Key Laboratory of Inland Saline  alkaline Aquaculture, Ministry of Agriculture and Rural Affairs, Shanghai200090) Abstract: To survive in the complex ocean environment, marine microbes have evolved a variety of adaptation systems, including the production of specific biomolecules and unique bioactive compounds which were never found in terrestrial environments. Marine microorganisms with abundant species and unique metabolism are important sources of marine natural products and new medicines. The South China Sea（SCS）is the largest sea in China. The abundant microbial resources in SCS are ideal objects for studying marine microbial diversity and natural products. To study the microbial diversity of surface seawater in SCS and bioactivity of fungi extracts, a study was carried out. Surface seawater samples were collected from eight stations in the northern part of SCS, then were filtered and diluted to different concentrations and spread on bacterial and fungal plates, finally, the plates were cultured in a constant temperature incubator at 28℃ for 328 d. After cultivation, the morphological characteristics of the colonies were visually observed. Colonies of different forms were brought up in corresponding culture media after preliminary screening and purified into single colonies, then stored under 4℃ on an inclined plane. With a molecular protocol by DNA amplification and sequencing of the 16S rRNA and ITS gene sequence alignment, a total of 162 bacterial strains and 43 fungal strains were isolated. The 162 bacterial strains belonged to 4 phyla, 5 classes, 15 orders, 21 families, 35 genera and 61 species. Proteobacteria and Actinomycetes were the dominant phylum. A total of 105 strains of Proteobacteria were identified as 84 strains of αProteobacteria, accounting for 51.8%; and 21 strains of γProteobacteria, accounting for 12.9%; 50 strains of Actinomycetes, accounting for 30.8%, 4 strains of Bacteroidetes, accounting for 2.5%, 3 strains of Firmicutes, accounting for 1.9%.Microbacterium and Erythrobacter were the dominant genera, which isolated 40 and 23 strains, respectively; E. pelagi was the highest with 12 strains. E. flavus, M. aurantiacum and M. schleiferi followed. From the results, the diversity and quantity of culturable bacteria isolated from different stations were different. Proteobacteria and actinobacteria were isolated from all 8 stations, and the number of proteobacteria strains was more than actinobacteria strains in each station, while Firmicutes and Bacteroidetes were only isolated from 3 stations. The bacteria genera diversity of stations 15, 19 and 21 was the highest, while the station 17 was the least with only 4 genera. Erythrobacter,Microbacterium and Qipengyuania were distributed widely and isolated from seven stations. Twenty genera of bacteria, which accounting for 57% of the total genus numbers, were only isolated from specific stations. The bacterial strains isolated from Firmicutes were least, and all strains were classified to Bacillus. 43 strains of fungi were isolated from eight stations, and ITS sequence results showed great similarity to fungi (over 98%) after comparison with database. The 43 strains were classified to 2 phyla, 5 classes, 7 orders,7 families,7 genera and 14 species. Strains isolated from Ascomycota were the highest (40 strains). The other three strains belonged to Basidiomycota. Aspergillus was the dominant genus among the strains, a total of 21 Aspergillus strains were isolated, accounting for 48.8% of 43 strains. In terms of number of species, Penicillium oxalicum was the most common species in which 9 strains were isolated, while Aspergillus versicolor followed with 7 strains. According to the fungal sequence results and the station difference of fungi, 16 strains of fungi were selected for further smallscale fermentation. After incubation for 18 d, the cultures were ultrasonicextracted two times with ethanol, respectively. After filtered and vacuum evaporated, the crude extracts were dissolved in DMSO to prepare 10 mg·mL-1 solutions for further activity screening. The HDAC inhibitor screening kit was used to screen the histone deacetylase inhibitory activity. Black 96well plate was used and the total reaction system was 100 μL. SAHA was dissolved in DMSO to prepare a 100 μmol·L-1 SAHA solution as positive control 1; TSA was used as positive control 2.Three parallel replicates were set for each sample to calculate the inhibitory activity of HDAC. Compared with the positive control groups, the crude extracts of these 16 fungi showed a certain inhibitory effect on HDAC. A. sydowii b96 showed the highest inhibition rate as 54%, while A. flavus f111 showed the lowest as 44%. The inhibition rate to histone deacetylase of 8 fungi crude extracts, A. Sydowii B96, A. versicolor H291, A. versicolor E118, and Cladosporium halotolerans B61, Cystobasidium Minutum E114, P. Oxalicum F112, Cystobasidium Minutum E129 and P. Oxalicum B49, was measured between 50% and 54%. The other fungi crude extracts to HDAC ranged from 44% to 49%. The activity of crude extracts from 16 strains of fungi on HeLa cells was determined by MTT method. The fungal crude extract was diluted to 60 μg·mL-1, and the paclitaxel was set as positive control with concentration of 2 μg·mL-1. Three parallel replicates were set. Results showed that these 16 fungal crude extracts had weak activity from 2% to 37% at a concentration of 60 μg·mL-1.The crude extracts of P. oxalicum H287 and A. versicolor H291 showed the highest inhibition activity of Hela cells by 37% and 35%, respectively, which was similar to the results of previous literature. Secondary metabolites with antitumor activity from these two fungi were supposed to acquire after expansion of fermentation in future study. The antibacterial activity of crude extracts was determined by KB disk method. The crude fungal extract was diluted to 0.2 mg·mL-1. Aeromonas Hydrophila and A. Vickers were inoculated into liquid medium for activation, then the bacterial solution concentration was adjusted to 104 cfu·mL-1 and coated on LB plate. The sterilized filter paper was placed on the plate, and 5 μL of diluted fungal crude extract was added. Then the plates were cultured in a constant temperature incubator at 28℃ for 12 h. The blank plate was used as negative control. Three parallel replicates were set for each sample to calculate diameter of antibacterial circle. Results showed that the 16 crude extracts did not show antibacterial activity against A. hydrophila and A. Vickers at the concentration of 200 μg·mL-1.According to literatures, secondary metabolites of some Aspergillus fungi had bacteriostatic effect on aquatic pathogens such as A. hydrophila. In our research, no crude extracts of these 16 fungi showed bacteriostatic effect on the same bacteria. And because the test concentration in this experiment is set as a single concentration, it is speculated that the concentration of active secondary metabolites in crude extracts is lower than its minimum inhibitory concentration. More groups of different extracts concentration should be set in further study to testify the bacteriostatic activity. Results showed that the microbial diversity of surface seawater in SCS was high and the extracts had multibioactivity. And it will provide references for developing and using of fungi sources of SCS in the future.  Keywords: South China Sea surface water; microorganism diversity; histone deacetylase inhibitory activity; antitumor activity  Related Articles | Metrics

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Effect of different phosphorus concentrations on the growth and alkaline phosphatase activity of free-living zooxanthellae 2022, 44(4): 459.  Abstract ( 119 )   PDF (1429KB) ( 359 )   Effect of different phosphorus concentrations on the growth and  alkaline phosphatase activity of free-living zooxanthellae LI Yue1,2, WANG Yunlong2, OUYANG Longling2 (1. College of Fisheries and Life Science, Shanghai Ocean University, Shanghai201306, China;  2. Key laboratory of East China Sea Fishery Resources Explotation and Utilization, Ministry of Agriculture and Rural Affairs,  East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China) Abstract: Symbiodinium sp. provides coral with oxygen and synthetic organic matter, while CO2, nitrate and phosphate produced by coral metabolism are used by Symbiodinium sp. to maintain its growth. As a beneficial reservoir of functional diversity, freeliving zooxanthellae can potentially repopulate highly impacted reef ecosystems. However, phosphorus is severely restricted in many coastal and estuarine waters, which could affect phytoplankton growth. Freeliving zooxanthellae is in a natural environment with constantly changing phosphate, and the effect of different phosphate concentrations on zooplankton algae is unknown. To understand how Symbiodinium sp., a species of freeliving zooxanthellae, responded to the dynamic change of dissolved inorganic phosphorus (DIP), we designed short term test and long term test to examine the effects of different phosphate concentrations on the growth, alkaline phosphatase activity (APA), chlorophyll a (chl a) and effective photochemical efficiency (Fq′/Fm′). Symbiodinium sp. was cultured under four different DIP initial concentrations (0.15, 10.00, 20.00,35.00 μmol·L-1PO43-) for 7 d in short term test, while the algal cells were cultured under a high DIP initial concentration (35.00 μmol·L-1PO43-) for 55 d in long term test. Subsequently, the cell density, DIP concentration in the culture medium and APA of algal cells were measured on 0, 1, 2, 4, 7 d in short term test, and every 5 d in long term test, respectively. In addition, chl a and Fq′/Fm′ were also measured in long term test. Results revealed that there were significant differences in the growth of Symbiodinium sp. under different initial concentrations of phosphate. The cell density of high initial concentration group was significantly higher compared with the other three groups (P＜0.05). In particular, when the initial concentration of phosphate was 0.15 μmol·L-1, although the initial concentration was low, the phosphate concentration decreased to 0.05 μmol·L-1 after 1 d, followed by no significant change (P>0.05), indicating that the growth of freeliving zooxanthellae was positively correlated with phosphate concentration. APA of algal cells in the test group of initial concentration of phosphate of 10.00, 20.00, 35.00 μmol·L-1was significantly lower than that of 0.15 μmol·L-1 test group (P<0.05), indicating that it was negatively correlated with the concentration of inorganic phosphorus in the environment. It could be seen that low inorganic phosphorus could induce the increase of alkaline phosphatase (AP) activity. Two days after inoculation, the algal cell density of each test group increased slowly or showed a downward trend, showing a growth retardation period of at least two days. On the 7th day of culture, the density of algal cells varied with the initial concentration of phosphate, which was shown as follows: the initial concentration of phosphate was 35.00 μmol·L-1, the density of algal cells was the highest and significantly higher than that of other groups (P<0.05); the initial concentration was 10.00 μmol·L-1 and 20.00 μmol·L-1, the density of algal cells was the second, and there was no significant difference between two groups (P<0.05); the initial concentration of phosphate was 0.15 μmol·L-1, the density of algal cells was the lowest, which was only 1/3 of that of the highest experimental group. When the initial concentration of phosphate was 35.00 μmol·L-1, the cell concentration in the medium began to increase rapidly, and reached the highest after 20 days, which was 2.34×108 L-1, and then there was a fluctuating decline. Under high concentration of phosphate (35.00 μmol·L-1), changes in the content of chl a in Symbiodinium sp. were consistent with the trend of algal cell density. However,changes in cell growth and chl a showed a 5day lag trend. The chl a content of algal cells increased exponentially in the first 15 d, and reached the maximum value of 3 034.27 μg·L-1 on the 15th day, then began to decline, and basically remained stable after the 40th day, which was 807.71873.23 μg·L-1. Results of Fq′/Fm′ analysis of algal cells showed that Fq′/Fm′ increased 5 d before culture, then decreased significantly, and the change trend changed after the 25th day, showing a fluctuating downward state. Along with the consumption of phosphate, the specific growth rate (μ) and Fq′/Fm′ of Symbiodinium sp. decreased, suggesting that a positive correlation existed between phosphorus limitation and photosynthetic efficiency. At the beginning of longterm culture experiment, the phosphate concentration in the culture medium decreased rapidly, and decreased to 0.04 μmol·L-1 on the 5th day, and then remained at a low level, showing a small fluctuation, ranging from 0.04 μmol·L-1 to 0.53 μmol·L-1. In contrast, the APA was significantly enhanced (P<0.05) after 20 d of culture at the phosphate initial concentration of 35.00 μmol·L-1, increased to the maximum on the 30th day, indicating that the DIP content was negatively correlated with APA, which was also presented when Symbiodinium sp. was cultivated under low phosphate initial concentration (0.15 μmol·L-1). During 2055 d, the change trend of algal cell APA was opposite to that of the number. It was speculated that the increase of algal cell number after the decline was due to the decline of algal cells, which released organic phosphorus to provide a substrate for AP, making algal cells regain inorganic phosphorus and proliferate. Alkaline phosphatase catalyzes dissolved organic phosphorus to DIP, which could enable Symbiodinium sp. to keep growing under low DIP concentration. In the shortterm and longterm culture experiments, the enhancement of AP activity did not cause the increase of DIP in the culture medium, which may be due to the fact that AP hydrolysis and DIP absorption were carried out at the same time. These results implied that like other dinoflagellates, Symbiodinium sp. could adapt to low phosphorus condition, and might help understand the mechanism of phosphorus utilization in this dinoflagellate in further research. Keywords: freeliving zooxanthellae; dissolved inorganic phosphorus; alkaline phosphatase; photosynthesis Related Articles | Metrics

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Effects of leaf extracts of three terrestrial plants on the growth and photosynthetic physiology of Prorocentrum donghaiense 2022, 44(4): 468.  Abstract ( 74 )   PDF (3668KB) ( 361 )   Effects of leaf extracts of three terrestrial plants on the growth  and photosynthetic physiology of Prorocentrum donghaiense XIANG Shu, CHEN Wenwen, SHEN Anglyu (College of Marine Ecology and Environment, Shanghai Ocean University, Shanghai201306, China) Abstract: Harmful algal bloom is an increasingly serious marine environmental problem for aquaculture, fisheries and public health in many coastal areas throughout the world. The dinoflagellate Prorocentrum donghaiense has been a major bloom species in the Yangtze River Estuary and adjacent coastal waters of the East China Sea during the annual blooms that occur in late April and May since 2000. Therefore, the control of P. donghaiense bloom gradually becomes one of research hotspots, and plant allelopathy is one of the important means of biological control of algal blooms due to its advantages such as simple operation, low environmental pressure, no secondary pollution and economic applicability. However, there are few studies on the effective control of P. donghaiense bloom in the East China Sea, especially in the cage culture area where blooms are easy to occur in the offshore area. Moreover, it has been found that the allelochemicals extracted from terrestrial woody plants have a good inhibitory effect on marine algae, however, there are only a few reports describing the inhibition effect of terrestrial plant extracts on bloomforming species, especially for P. donghaiense. We hypothesized that leaf powder of terrestrial plants could build a bloom isolation zone in the cage aquaculture area learned from the principle of forest fire prevention isolation zone. Therefore, in this study, leaves of three common terrestrial plants, Cinnamomum camphora, Nerium indicum and Ginkgo biloba, were selected as algae inhibition materials, and the effects of seawater extracts from these three plant leaves on the growth inhibition effect were studied. Furthermore, the effects of leaf extracts of the three plants on the actual photochemical quantum efficiency (Fv′/Fm′), photosynthesis efficiency (α), relative maximal electron transport rates (rETRmax), and light saturation coefficient (Ik) of P. donghaiense were as well carried out to comprehensively evaluate the regulatory effects of leaf extracts of the three plants on the photosystem PS Ⅱ of algae to provide basis for biological control of P. donghaiense bloom. Results showed that low concentration of the extracts (< 1.0 g·L-1) from the leaves of C. camphora and N. indicum had no obvious inhibitory effect on P. donghaiense during the experiment period, 0.5 g·L-1 and 1.0 g·L-1 G. biloba extracts could slightly stimulate the growth of algae cells when treated for 72 h. However, the three extracts had a significant inhibitory effect on the algae density of P. donghaiense at 48 h (P<0.05) with the increase of extract concentration(> 1.0 g·L-1), and the cell growth inhibition rate of P. donghaiense treated by C. camphora and N. indicum extracts was 100.0% under 3.0 g·L-1 at 96 h, higher concentrations of G. biloba extract (3.0 and 5.0 g·L-1) had a significant effect on the growth of P. donghaiense (P<0.05) as well and the cell growth inhibition rate was 74.9% and 88.7% at 96 h. The 96 h EC50 of P. donghaiense cell growth under C. camphora, N. indicum and G. biloba extracts was 0.84 g·L-1, 1.30 g·L-1 and 1.74 g·L-1, respectively. In addition, there was no significant difference of Fv′/Fm′ values in P. donghaiense under low concentration of extracts (0.1 g·L-1 for C. camphora and N. indicum, and ≤ 1.0 g·L-1 for G. biloba) compared to that of the control group. The algal inhibition ratio of Fv′/Fm′ under 0.5 g·L-1, 1.0 g·L-1 and 3.0 g·L-1 C. camphora extracts was 19.4%, 29.9% and 100.0% after 96 h treatment, respectively. The algal inhibition ratios of Fv′/Fm′ under 0.5 g·L-1, 1.0 g·L-1, 3.0 g·L-1 and 5.0 g·L-1 N. indicum extracts were 11.9%, 19.4%, 97.0% and 100.0% after 96 h treatment, respectively. The algal inhibition ratios of Fv′/Fm′ under 3.0 g·L-1 and 5.0 g·L-1 G. biloba extracts were 88.9% and 100.0% after 96 h treatment, respectively. By analyzing the relativeelectron transfer efficiency (rETR) and fast light response curve, it was found that values of α, rETRmax, and Ik decreased in different degrees with the increase of leaf extracts concentration and treatment time. For example, there was no significant difference of α, rETRmax, and Ik values in P. donghaiense under low concentration of three extracts (< 1.0 g·L-1) compared to that of the control group after 24 h treatment, and values of α, rETRmax, and Ik in P. donghaiense under high concentration of three extracts (≥ 3.0 g·L-1) were significant lower than that in the control group at the end of the experiment (P<0.05). Furthermore, the algal inhibition ratio of α, rETRmax, and Ik under 3.0 g·L-1 C. camphora extract treatment was 100.0%, the algal inhibition ratio of these parameters under 3.0 g·L-1 N. indicum extract treatment was 57.4%, 94.0% and 70.1%, and the algal inhibition ratio of these parameters under 5.0 g·L-1 G. biloba extract was 88.9%, 96.1% and 62.2% after 96 h culture. These results indicated that the photosynthesis of P. donghaiense was inhibited significantly by these extracts. In summary, the leaf extracts of C. camphora, N. indicum and G. biloba have different inhibitory effects on the growth of P. donghaiense. By comprehensively analyzing the changes of P. donghaiense cell density and values of 96 h EC50, it can be found that C. camphora has the best inhibitory effect, N. indicum takes the second place, and G. biloba leaf extract has the lowest inhibitory effect. The difference in algal inhibition efficiency may be due to the different types and contents of allelochemicals contained in the three plants. The photosynthetic parameters of P. donghaiense significantly reduced when treated by high concentration extracts (≥ 3.0 g·L-1) of C. camphora, N. indicum and G. biloba leaves, so they have a significant inhibitory effect on the photosynthesis of P. donghaiense, and future research can focus on the changes of photosynthetic pathways in algae through transcriptomic analysis. The results of this study provide a basis for screening effective algae inhibiting plants for controlling P. donghaiense bloom through allelopathy, especially in the offshore cage culture area. Keywords: Prorocentrum donghaiense; common terrestrial plants;allelopathy of plants; growth restriction; photosynthetic system Related Articles | Metrics

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Study on integrated bioremediation of Suaeda glauca and Perinereis aibuhitensis on Meretrix meretrix aquaculture ponds 2022, 44(4): 480.  Abstract ( 86 )   PDF (2171KB) ( 349 )   Study on integrated bioremediation of Suaeda glauca and  Perinereis aibuhitensis on Meretrix meretrix aquaculture ponds LI Lei1, DAI Ming2, ZHAO Yongchao3, CHEN Yusheng3,  XU Chenglin3, WANG Shuaijie1, JIANG Mei1 (1. Key Laboratory of Aquaculture on Salinealkaline Land, Ministry of Agriculture and Rural Affairs, Fishery  Engineering Technology Research Center for Salinealkaline Waters(Shanghai),East China Sea Fisheries  Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China;  2. Guangdong Provincial Key Laboratory of Fishery Ecology and Environment， South China Sea  Fisheries Research Institute, Chinese Academy of Fisheries Sciences, Guangzhou510300, China;   3. Jiangsu Marine Fisheries Research Institute, Nantong， Jiangsu226007, China) Abstract: Aquaculture has been a fastgrowing industry because of significant increases in demand for seafood throughout the world, aquaculture is an important source of human protein. It is growing more rapidly than any other segment of the animal culture industry. Aquaculture production of China has long ranked first in the world, pond aquaculture is an important part of marine aquaculture, and China is the country with the largest scale of pond aquaculture in the world. However, with the development of aquaculture, its impact on marine environment has been concerned by more and more people. Compared with the culture mode in the natural sea area, the traditional aquaculture pond ecosystem is an artificial open ecosystem established for economic purposes. The traditional aquaculture pond ecosystem is characterized by its small area, shallow pond water, simple nutrient structure, and fragile ecological balance. Its ecological structure and function are mainly affected by natural climate and human activities. The pollution sources of aquaculture ponds mainly include external pollution and internal pollution of cultured organisms. Pollution can lead to eutrophication of water bodies and accumulation of pollutants in sediments. Although some pollutants can be degraded through the pond's own physical, chemical and biological processes, due to lack of the material circulation function of the natural ecosystem, with the continuous expansion of the pond aquaculture scale and the continuous improvement of the breeding density, aquaculture sewage has become a potential pollution source. At present, the restoration technologies applied in the aquaculture industry mainly include physical, chemical and biological means. Among them, bioremediation methods (including aquatic plants, aquatic animals, and microbial methods) have become the potential optimal restoration method for the aquaculture industry, because its impact on aquaculture is small, there will be no secondary pollution, and the restoration effect is longlasting. The goal of bioremediation is to transform or degrade pollutants in the aquaculture environment. The single restoration of water and sediment pollutants has limited effect on the improvement of aquaculture environment. Comprehensive restoration is more important for aquaculture restoration. The selection of restoration species and the placement density control is the key to the success of comprehensive repair model. Studies have shown that aquatic plants such as Suaeda salsa can reduce the nutrient content of aquaculture water to a certain extent. Benthic polychaetes, especially Perinereis aibuhitensis, have become important sediment restoration species due to their diverse variety, wide distribution and strong adaptability, which can reduce the total organic nitrogen (TN) , total organic phosphorus (TP) , total organic carbon (TOC), sulfide, organic matter and other pollution indicators in sediments to a certain extent. In order to evaluate the bioremediation effect of integrated bioremediation of Suaeda glauca and Perinereis aibuhitensis on aquaculture ponds, we used Meretrix meretrix aquaculture ponds as a case study, indoor simulation experiment was carried out to study the trends of water eutrophication and sediment pollution by placing S. glauca and P. aibuhitensis. Eight groups were set up:A1：30 S.glauca; A2：20 S.glauca; A3：10 S.glauca; B：0.20 kg·m-2 P.aibuhetensis; C1：30 S.glauca and 0.20 kg·m-2 P.aibuhetensis; C2：20 S.glauca and 0.20 kg·m-2 P.aibuhetensis; C3：10 S.glauca and 0.20 kg·m-2 P.aibuhetensis; D：control group with only sediment and sea water. Results showed that both S. glauca and P. aibuhitensis grew well, dissolved inorganic nitrogen (DIN) presented different changing trends between different experimental groups, DIN of C1 experimental groups declined by 14.10%, DIN of C1 and C2 experimental groups increased by 18.06% and 42.89%, respectively. Dissolved inorganic nitrogen (DIP) presented the same changing trends between different experimental groups, dissolved inorganic phosphates (DIP) of C1, C2 and C3 experimental groups declined by 40.00%, 28.57% and 19.30%, respectively. The sulfide and total organic carbon content of bottom sediments presented the same changing various trends between different experimental groups, the sulfide content of C1, C2 and C3 experimental groups declined by 26.80%, 26.03% and 19.30%, respectively. TOC content of C1, C2 and C3 experimental groups declined by 48.07%, 38.71% and 43.47%, respectively. Results showed that integrated bioremediation of S. glauca and P. aibuhitensis had a certain effect on water eutrophication, sulfide and TOC in sediment. The nutrient absorption efficiency of S. glauca is related to the growth, root length and quantity of S. glauca. Bioturbation of P. aibuhitensis is the main factor affecting the changes of sulfide and TOC content in sediments. P. aibuhitensis has strong digging ability, dissolved oxygen can be transported to the deep layer of the sediment, and the reducing environment of the sediment is oxidized, which can reduce the content of sulfide in the sediment. P. aibuhitensis can directly feed on the organic matter in the sediment, which directly reduces the TOC content in the sediment; on the other hand, the microbial decomposition of the organic matter in the sediment is also an important factor in the decrease of TOC content. The excretion of P. aibuhitensis, the adsorptiondesorption process of suspended particulate matter and bioturbation all lead to the increase of nutrient exchange flux at the sedimentwater interface, but the increment gradually decreases with time. Results of this study showed that under certain experimental conditions, the restoration combination of 30, 20, 10 S. glauca and 0.20 kg·m-2 P. aibuhitensis stocking density had a certain removal effect on DIN, DIP in water, sulfide and TOC in sediments , among them, 30 S. glauca and 0.20 kg·m-2 density of P. aibuhitensis had the best comprehensive restoration effect. However, in the actual cultivation process of the pond, the growth of bait algae is a factor that must be considered in shellfish breeding. The breeding water body needs to maintain a certain concentration of nutrients. At the same time, in order to maintain the necessary photosynthesis intensity of the bait algae, the number of S. glauca is not the more the better, the coverage rate can only be maintained within a certain area, and the optimal proportion of comprehensive restoration needs to be further experimentally verified in combination with primary productivity and other indicators on site. This study could provide a theoretical and practical foundation for bioremediation of aquaculture ponds. Keywords: aquaculture ponds; Suaeda glauca; Perinereis aibuhitensis; integrated bioremediation Related Articles | Metrics

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Accumulation, metabolism and elimination of enrofloxacin in submerged macrophytes in simulated ecosystem 2022, 44(4): 491.  Abstract ( 91 )   PDF (2532KB) ( 375 )   Accumulation, metabolism and elimination of enrofloxacin in  submerged macrophytes in simulated ecosystem LI Chuanbu1，2， WANG Yuan2， ZHAO Shu2， FAN Peili2，  LING Hai1，2， LI Xincang2， ZHOU Junfang2， FANG Wenhong2 (1. Key Laboratory of East China Sea Fishery Resources Exploitation and Utilization, Ministry of Agriculture and Rural affairs,  East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai200090, China; 2. National  Pathogen Collection Center for Aquatic Animals, College of Fisheries and Life  Science, Shanghai Ocean University, Shanghai201306, China) Abstract: In order to evaluate the efficiency of antibiotic removal of submerged macrophytes from aquaculture tail water, HPLC method for the determination of enrofloxacin and ciprofloxacin in submerged macrophytes was established based on the improved QuEChERS pretreatment method. The accumulation, metabolism and elimination of enrofloxacin residue in submerged macrophytes were studied in simulated ecosystem. The effects of different extraction solution, extraction salt and extraction time on the recovery were optimized, and the purification effect of different purification agents was investigated. The recovery rates of enrofloxacin and ciprofloxacin in submerged macrophytes were 79.60 %110.15 % and 57.26 %102.00 %, respectively. The detection limits were 0.003 μg·g-1 and 0.005 μg·g-1, respectively. In simulated ecosystem, Vallisneria natans, Elodea nuttallii and Hydrilla verticillata were exposed to enrofloxacin of final concentration of 200 μg·L-1, respectively. The maximum enrofloxacin concentration of 0.82 μg·g-1, 0.86 μg·g-1 and 2.34 μg·g-1 were determined at 24 h after the exposure. The areas under the curves (AUC) were 192.06 （μg·g-1)·h, 209.92 (μg·g-1)·h and 471.44 (μg·g-1)·h, respectively. The bioaccumulation coefficients (FBC) of enrofloxacin were 9.7, 10.2 and 27.8, respectively. The concentrations of ciprofloxacin, the metabolite of enrofloxacin, reached the highest value at 72 h after the exposure, which were 0.027 μg·g-1, 0.029 μg·g-1 and 0.037 μg·g-1 respectively, and showed a slow downward trend after 300 h; the area under the curves(AUC) were 8.42 (μg·g-1)·h, 8.21 (μg·g-1)·h and 12.21 (μg·g-1)·h, respectively. Results showed that submerged macrophytes could effectively accumulate enrofloxacin residue in aquaculture tail water, and Hydrilla verticillata was significantly better than Vallisneria natans and Elodea nuttallii. The results provided a theoretical basis for the treatment of antimicrobial residues in aquaculture tail water. The submerged macrophytes can absorb antibiotics from the aquatic environment through  roots and leaves, and then migrate and transform them into other metabolites in the macrophytes, which plays a certain role in the degradation of antibiotics in the aquatic environment. In aquaculture, insitu degradation or translocation degradation of antibiotics by aquatic plants has the characteristics of low cost, high efficiency and green environmental protection, which has a considerable application prospect in aquaculture tail water treatment. HPLC method for the determination of enrofloxacin and ciprofloxacin in submerged macrophytes was established based on the improved QuEChERS pretreatment method. Finally, 1% formic acid acidified acetonitrile was selected as the extraction solution, 1.0 g NaCl as the extraction salt. The sample was purified with 50 mg PSA and 5 mg GCB, and was extracted by vortex for 15 min. The recovery rates of enrofloxacin and ciprofloxacin in submerged macrophytes were 79.60%110.15% and 57.26%102.00%, respectively. The detection limits were 0.003μg·g-1 and 0.005 μg·g-1, respectively. In order to evaluate the removal efficiency of antibiotics in submerged macrophytes from aquaculture tail water, the experiment was carried out in simulated ecosystem.  Vallisneria natans, Elodea nuttallii and Hydrilla verticillata were chosen to investigate its absorption, elimination and removal effects of antibiotics. They were separately exposed to  enrofloxacin of final concentration of 200 μg·L-1,respectively. The maximum enrofloxacin concentration of 0.82 μg·g-1, 0.86 μg·g-1 ,2.34 μg·g-1were determined at 24 h after the exposure. The areas under the curves (AUC) were (192.06 μg·g-1)·h, 209.92 (μg·g-1)·h,471.44 (μg·g-1)·h, respectively. The bioaccumulation coefficients (FBC) of enrofloxacin were 9.7, 10.2 and 27.8, respectively. The concentrations of ciprofloxacin, the metabolite of enrofloxacin, reached the highest value at 72 h after the exposure, which were 0.027 μg·g-1, 0.029 μg·g-1 and 0.037 μg·g-1 respectively, and showed a slow downward trend after 300 h; the areas under the curves(AUC)were 8.42 (μg·g-1)·h,8.21 (μg·g-1)·h, 12.21 (μg·g-1)·h, respectively.  Results showed that submerged macrophytes could effectively accumulate enrofloxacin residue in aquaculture tail water, and Hydrilla verticillata was significantly better than Vallisneria natans and Elodea nuttallii in accumulation effects. These results provided a theoretical basis for the treatment of antimicrobial residues in aquaculture tail water. Keywords: enrofloxacin; submerged macrophytes; accumulation, metabolism and elimination; simulated ecosystem; HPLC method Related Articles | Metrics

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Processing technology, quality characteristics and application status of Antarctic krill powder 2022, 44(4): 501.  Abstract ( 216 )   PDF (1184KB) ( 372 )   Processing technology, quality characteristics and  application status of Antarctic krill powder YANG Liu1,2 , WANG Lumin2, ZHOU Guoyan1, GUO Quanyou2, ZHENG Hanfeng2,  ZHENG Yao2, YANG Xu2, WANG Wanyong3, QIN Ganjing3   (1．School of Health Science and Technology, University of Shanghai for Science and Technology,  Shanghai200093, China; 2．East China Sea Fisheries Ｒresearch Institute，Chinese Academy of Fishery Sciences， Shanghai200090，China; 3．Jiangsu Sunline Deepsea Fishery Co. Ltd., Lianyungang Jiangsu, China) Abstract: Antarctic krill is a kind of small crustacean widely distributed in the waters of the Southern Ocean. Its biological resources are rich, about 0.651.00 billion tons. The main fishing countries are Norway, China, Chile, Japan, etc. It is rich in protein, astaxanthin, phospholipids and other nutrients, and is known as the “future animal protein warehouse of mankind”. Antarctic krill contains highly active endogenous hydrolases, which are easy to autodissolve, resulting in a rapid decline in shrimp freshness. Therefore, it is necessary to carry out onboard processing in time after fishing to prepare frozen shrimp or shrimp powder. Antarctic krill powder has the characteristics of high freshness of raw materials, excellent product quality and low transportation cost. In recent years, its processing proportion has gradually increased, and it has become one of the main processing products of Antarctic krill. Antarctic krill powder is rich in protein, astaxanthin, phospholipids and other components. It is mainly used in the production of krill oil, krill peptide and other functional products, as well as the production and processing of animal feed. The full efficiency utilization and highvalue processing have become the focus of the industry. This paper mainly searches the research and review articles on Antarctic krill powder in recent ten years, combined with patent examination and industrial research, understands the production technology and processing technology of Antarctic krill powder, expounds the main processing links, and summarizes the main research directions and research results of Antarctic krill powder. At present, the research on Antarctic krill powder mainly includes processing technology, nutritional quality and application, so this paper elaborates on these three aspects. Firstly, the advantages and disadvantages of different processing methods of whole krill powder and skimmed krill powder are introduced, and the process optimization of three key processing steps of cooking, separation and drying by different scholars is summarized. Secondly, the nutritional quality of whole fat krill powder is evaluated, mainly referring to its internal quality. The nutritional value includes the content of basic nutrients such as protein and lipid, the composition of amino acids and fatty acids, the content of minerals and other active substances. The safety is mainly to guide the fluorine content in krill powder, and the focus is to optimize the fluoride removal process. Finally, the application status of Antarctic krill powder is introduced, in which shrimp oil extraction and aquaculture are the traditional application directions, and the emerging field of highvalue utilization is the current research hotspot. From the processing of Antarctic krill powder, cooking will denature and solidify Antarctic krill protein to a certain extent, and high temperature will inactivate endogenous enzymes, and kill heatresistant microorganisms. When heating at room temperature, the central temperature controlled between 5560℃, the quality of krill powder is the best. The purpose of separation is to realize solidliquid separation of cooked materials and improve the subsequent drying efficiency. This link mainly affects the conversion rate of shrimp powder. The content of protein, fat and minerals in shrimp powder obtained by twinscrew extrusion technology increases. Drying can remove excess water, but too high temperature will cause adverse effects such as oil oxidation. Freeze drying (-50℃), lowpower microwave drying (≤1 kW) and lowtemperature hot air drying (≤60℃) are three drying methods conducive to the production of Antarctic krill powder with high astaxanthin content. From the quality characteristics of Antarctic krill powder, it has the characteristics of high protein and high fat, and shows good nutritional value. However, due to the influence of processing technology, the content of basic nutrients is different. The content of crude protein in the whole shrimp powder of Antarctic krill is the highest, which is 55%70%, followed by crude fat, which is basically in the range of 5%15%, ash content is 9%18%, and water content is 2%10%. The ash content of krill powder prepared after shelling reduces significantly, and the content of crude protein increases. The amino acid composition of the whole krill powder of Antarctic krill conforms to the ideal essential amino acid composition mode recommended by FAO/WHO (1973). The fatty acid composition is rich, it is also rich in EPA and DHA. Antarctic krill powder is rich in minerals, astaxanthin and other substances, of which the content of astaxanthin is in the range of 110140 mg·kg-1, and the content of minerals and chitin can reach 6%. The main factor affecting the safety of Antarctic krill powder is the content of fluorine. Enzymatic hydrolysis, calcium chloride method and hydrochloric acid multistage countercurrent extraction method are effective methods for defluorination of shrimp powder. During the storage of krill powder, lipid oxidation and enzymatic hydrolysis, astaxanthin and tocopherol oxidation can occur. Vacuum storage is conducive to improve the oxidative stability of krill powder. At the same time, adding antioxidant (VE) or deoxidizer (reduced iron powder) can improve the storage of Antarctic krill powder. From the perspective of the application of Antarctic krill powder, it is mainly used in aquatic feed and highvalue utilization. Antarctic krill powder has high protein content and rich flavor amino acids, which plays a certain role in food attraction. It can be added to aquatic feed as a protein source, which can promote the growth performance of aquatic animals, but the promotion effect varies with the feeding objects. At the same time, it can also improve the muscle quality of aquatic animals, improve the meat flavor and muscle color. And it can promote the nonspecific immunity and antioxidant capacity of aquatic animals. Modern methods such as chemical reagent extraction and enzyme engineering are used to extract krill oil, astaxanthin and prepare active peptides. The highvalue utilization of Antarctic krill powder is mainly based on these aspects. At present, shrimp oil is mostly extracted by organic solvent extraction, enzymatic hydrolysis and subcritical fluid extraction, but the difference of extraction methods will affect the extraction efficiency and nutritional value. To overcome the problems of the current single extraction method and develop multidimensional combined extraction methods with high extraction efficiency, convenience and environmental protection is very necessary. Using krill powder as raw material, astaxanthin is extracted by organic solvent method, and its extraction process and production application still need to be further studied. Enzymatic hydrolysis is the main method to prepare Antarctic krill protein peptide, which has the advantages of high production efficiency, but it is easy to produce bitter taste, which restricts its popularization and application in food. Using the target microbial fermentation and biological enzymatic hydrolysis, while ensuring its degree of hydrolysis, the flavor of active peptides is improved by using microbial fermentation, which has gradually attracted the attention of the industry, and has good development potential and application prospects. To sum up, Antarctic krill powder is rich in nutrition, but at present, China’s relevant production and processing equipment is backward, the product quality varies greatly, and the potential value of Antarctic krill powder has not been fully utilized. We should carry out targeted process optimization and systematic equipment upgrading, establish a standardized production system of shrimp powder, and focus on the research related to the highvalue utilization of Antarctic krill powder. This paper systematically expounds the production technology, nutritional quality and highvalue utilization of Antarctic krill powder, in order to provide reference for establishing the whole industrial chain technology system of Antarctic krill powder processing on board, processing on land and industrial application, extending the industrial chain and improving the added value. Keywords: Antarctic krill powder; onboard processing; parameter optimization; nutritional quality; production applications  Related Articles | Metrics