In recent years, researchers have discovered a large number of secondary metabolites with novel chemical structures and diverse activities from sponge-derived actinomycetes. Sponge-derived actinomycetes have become important sources of new drug lead compounds. The actinomycete <italic>Streptomyces parvulus</italic> MA1076 is derived from the sponge( <italic>Pseudoceratina</italic> sp.) on Yongxing Island in the South China Sea. In order to obtain the structural type and potential medicinal value of the secondary metabolites, strain identification and chemical composition analysis were carried out on the sponge-associated actinomycete <italic>Streptomyces parvulus</italic> MA1076. Bacterial genomic DNA rapid extraction kit was used to extract streptomyces genomic DNA. Streptomyces universal primers 27F and 1492R were used for PCR amplification, and the amplified products was sent for sequence testing. The sequencing result was used for strain identification through 16S rDNA sequence analysis and phylogenetic tree construction. Silica gel column chromatography, Sephadex LH-20 gel column chromatography, semi-preparative high performance liquid chromatography and other techniques were applied to separate and purify the ethyl acetate extract of the sponge-derived actinomycetes <italic>Streptomyces parvulus</italic> MA1076. The structure of the compound was identified by spectral data such as proton nuclear magnetic resonance spectroscopy (¹H-NMR), carbon nuclear magnetic resonance spectroscopy (¹³C-NMR), high-resolution mass spectrometry (HR-MS),and combined with the comparison with literature data. Six compounds were isolated and identified from the actinomycetes <italic>Streptomyces parvulus</italic> MA1076, which were actinomycin D (compound 1), daucosterol (compound 2), cyclo-((<italic>S</italic>)-Pro-(<italic>R</italic>)-Leu) (compound 3), thymidine (compound 4), 3′-<italic>O</italic>-acetylthymidine (compound 5), and indole-3-carboxyli acid (compound 6). Compounds 2-6 were isolated for the first time from <italic>Streptomyces parvulus</italic> MA1076. The six compounds were tested for their cell proliferation inhibitory activity on two pancreatic cancer cell lines (pc-12 and bc-16). Results showed that compound 1 had obvious proliferation inhibitory activity on both pancreatic cancer cell lines. Compounds 2-6 showed no obvious anti-tumor cell proliferation activity. The results of the study make full use of the abundant Chinese sponge resources and their associated microbial resources, exploring the structural diversity of sponge secondary metabolites to discover new chemical substances that may be contained in natural products, and to develop new antibacterial , antitumor drugs is of great theoretical significance and potential application value.

<italic>Collichthys lucidus</italic> is an important small economic fish species in coastal areas of China. Because of fast growth, large catches and delicious taste, it is loved by people of Fujian and Zhejiang in China. At present, there are only a few studies of <italic>C</italic>. <italic>lucidus</italic> on nutrition. To improve the basic data of quality and nutritional composition of muscle in this species, this study analyzed and evaluated the nutrient composition of <italic>C</italic>. <italic>lucidus</italic> muscles from Mindong waters. Nutritional components in muscle of <italic>C</italic>. <italic>lucidus</italic> were tested and analyzed with routine methods. Samples of 30 wild individuals, with (12.45±1.25) cm in body length and (37.15±13.25) g in body weight, were collected from Mindong waters during the reproductive season. The results showed that contents of moisture, crude ash, crude protein and crude fat of fresh muscles were (77.70±0.21)%, (1.49±0.59)%, (17.21±0.27)% and (0.56±0.05)%, respectively. There were 17 common amino acids found in muscles, including 7 essential amino acids (except Trp). In fresh sample, the total content of amino acids was (17.01±0.11)%, the content of essential amino acids was (6.09±0.06)%; in dry sample, the total content of amino acids was (76.30± 0.44)%; the content of essential amino acids was (27.33±0.29)%; the percentage of essential amino acids in total amino acids was 35.82%; the ratio of amino acids to no-essential amino acids (EAA/ NEAA) was 66.73%. The constitutional rate of the essential amino acids accorded with the FAO/WHO standard fundamentally. According to nutrition evaluation in amino acids score (AAS) and chemical score (CS), the first limited amino acid was Val, and the second limited amino acids were Leu and Phe+Tyr; the essential amino acids index (EAAI) was 67.04. In dry sample, the content of four kinds delicious amino acids was (26.24±0.01)%, and the percentage of delicious amino acids in total amino acids was 34.40%. 27 fatty acids were found in muscle of <italic>C</italic>. <italic>lucidus</italic>. There were 12 types of saturated fatty acids, accounting for (56.48±0.10)% of the total fatty acids. The content of C18∶0 in saturated fatty acids was the highest, accounting for (32.77±0.42)% of the total fatty acids. There were 7 types of monounsaturated fatty acids, accounting for (13.22±0.12)% of the total fatty acids, and 8 types of polyunsaturated fatty acids, accounting for (30.31±0.18)% of the total fatty acids. The percentages of EPA and DHA in total fatty acids of <italic>C</italic>. <italic>lucidus</italic> were (8.23±0.14)% and (13.22±0.12)%, respectively. The composition of trace elements in muscles of <italic>C</italic>. <italic>lucidus</italic> was reasonable. Therefore, <italic>C</italic>. <italic>lucidus</italic> is delicious fish species with balanced nutrition and relatively high nutritional value, which deserves further exploitation and popularization.

<italic>Lateolabrax maculatus</italic> is an important economic fish species in China. It is a eurysaline species and can survive and grow in water environment with varieties of salinity. It is of practical significance to study the tolerance and adaptability of <italic>L</italic>. <italic>maculatus</italic>, because it usually suffers from sudden increase or decrease of salinity in aquaculture environment. This work investigated the effects of abrupt salinity changes on the activitiy of metabolic enzymes and antioxidant enzymes and cortisol content in liver of <italic>L</italic>. <italic>maculatus</italic> by simulating salinity changes of water for its breeding. The salinity was reduced from 18 to 0 and remained for 7 d, and then increased to 33 sharply after acclimation and remained for 7 d. Correspondingly, in the other treatment, the salinity increased from 18 to 33, and then decreased to 0 sharply after acclimation and remained for 7 d. Samples were taken on 0, 0.5, 1, 3,7 d after the start of the experiment, respectively. The activitiy of alkaline phosphatase, acid phosphatase, glutamic-pyruvic transaminase, glutamic-oxalacetic transaminase, superoxide dismutase, catalase, glutathione peroxidase in serum and liver of <italic>L</italic>.<italic>maculatus</italic> was tested, and cortisol (COR) content in serum was monitored as well. Results showed that the abrupt salinity changes would have impact on activitiy of metabolic enzymes and antioxidant enzymes, and COR content of <italic>L</italic>.<italic>maculatus</italic>. The activitiy of enzymes and COR content showed a trend of increasing firstly and then declining with time prolonging under most situations of abrupt salinity changes. These results showed that <italic>L</italic>.<italic>maculatus</italic> had a stress reaction during the abrupt changing of salinity, and could adapt to the change within 3-7 days, which indicated that <italic>L</italic>.<italic>maculatus</italic> had a substantial tolerance and adaptability to the abrupt changes in salinity. The changes of morphological characteristics, metabolic enzyme activity, antioxidant enzyme activity and COR content showed that <italic>L</italic>.<italic>maculatus</italic> could more rapidly adapt to sudden drop in salinity and was more adaptable to low-salinity environment.

In order to study the effects of different sperm densities of <italic>Pelteobagrus vachelli</italic> on the fertilization rate, hatching rate and emergence rate of hybrid yellow catfish Huangyou-1, this paper adopted 8 groups of different sperm densities (1×10³-1×10⁶ cells·mL^-1) to carry out artificial insemination experiments. The fertilized eggs were hatched under the same environmental conditions until the out-of-the-membrane fry developed and started to feed during the parallel swimming period. The hatching water temperature was (27±1) ℃ and each gradient was repeated in three groups.Results showed that when the sperm density increased from 1×10³ cells·mL^-1 to 2.5×10⁴ cells·mL^-1, the fertilization rate, hatching rate and emergence rate all increased significantly (<italic>P</italic><0.05); when the sperm density was 5×10⁴ cells·mL^-1, the fertilization rate reached the maximum value of (88.8±2.0) %; when the sperm density was 2.5×10⁴ cells·mL^-1, the hatching rate and emergence rate reached the maximum, respectively (83.4±2.8) % and (79.4±4.6)%. In addition, the regression equation was established to determine the relationship between sperm density and fertilization rate, hatching rate and emergence rate. In this experiment, 8 different sperm densities (1×10³-1×10⁶ cells·mL^-1) were used to artificially inseminate hybrid yellow catfish, and the optimal sperm density was determined. It is recommended that the sperm density range of 2.5×10⁴-5×10⁴ cells·mL^-1 should be used for artificial insemination in actual production. This density uses less sperm than in actual production, which can effectively protect male gamete resources and reduce the demand for cryopreservation of sperm during artificial seed production. The optimal sperm density selected in this experiment can be used as the best choice in large-scale production of hybrid yellow catfish, and it can also provide certain references for artificial insemination and hybrid breeding of yellow catfish.

Anthropogenic noise pollutions are gradually increasing in the world, especially in coastal waters due to shipping and seismic exploration. However, the need for high-quality aquatic products has led to more and more marine suspended farming, which may add to the new sources of low-frequency anthropogenic noises in the ocean. Waters around the Gouqi Island, one of the major reef islands in the northern Zhoushan Archipelago, are considered as important suspended farming waters of mussel. The units of suspended farming facilities composed of aquaculture lines with attached mussels, or the sleeves, are suspended in the surface layer by buoys. The length of the sleeves is 2.3-2.8 m and the water layer occupied by the aquaculture system is about 3.5 m. These suspended farming facilities can reduce the current speed significantly. In this paper, the underwater noises of mussel suspended farming waters of Gouqi Island were measured by a passive monitor system at two sites (inside and outside mussel farming waters) with depths of 5 m and 10 m, and boat noises were also recorded to determine the noise source. All sounds were monitored prior to record to ensure the minimum self-noise, and at least 10 recordings were made and separated by at least 5 min. Power spectra of sound recordings were presented as 1/3-octave sound pressure level (SPL) in dB. Results showed that the main frequency of boat motor noise was 250 Hz, and its SPL at 5 m (114.7± 1.7) dB was greater than that at 10 m (97.4±0.9) dB when the boat was anchored. There were three peak frequencies (63 Hz, 250 Hz, 500 Hz) of underwater noises generated outside the mussel farming waters, where the SPL of 250 Hz at 5m was greater than that at 10m, indicating that the environmental noise outside mussel farming waters was greatly affected by fishing boat. The average environmental noise SPL was (87.7±13.7) dB inside the mussel farming waters, there were also three peak frequencies (63 Hz, 250 Hz, 500 Hz), where SPL of 500 Hz at 10 m (85.13±0.5) dB was greater than taht at 5 m (179.4±0.9) dB, indicating that the suspended mussel farming facilities were the main source of 500 Hz inside the mussel farming waters. This vertical distribution of marine environmental noise may be due to the blocking effect of mussel suspended farming facilities on tidal currents. Owing to that tidal current velocity was reduced in the surface layer, underwater noise level at bottom was greater than that in the surface layer. The underwater noise from suspended farming facilities can contribute significantly to the local ocean noise, and it is clear that the frequency of the suspended farming noise overlaps with the frequency used for acoustic communication in fish. It is necessary to increase our understanding of marine soundscapes, especially when ocean soundscapes continue to be suffered from human activity. In the future, more studies on the effects of noise from aquaculture facilities on the biology and ecology of fish are needed to fill the missing link in acoustic ecology.

In order to study the relationship between the structural characteristics of invertebrate communities in Tianjin coastal waters and environmental factors, bottom trawl nets were used to conduct a monthly survey of Tianjin coastal waters in April and from June to November of 2019, and the invertebrate species in Tianjin coastal waters were analyzed. The relationships between composition, dominant species, community structure changes and abundance distribution and environmental factors were studied. Results showed that: 34 species of invertebrates were monitored in 2019, of which Arthropods and Molluscs were the most (16 species), followed by Echinoderms (1 species) and Moths (1 species); the dominant species of invertebrates in 2019 were 4 species: <italic>Arcuatula senhousia</italic>, <italic>Loligo beka</italic>, <italic>Charybdis japonica</italic>, <italic>Oratosquilla oratoria</italic>; the average abundance of invertebrates in 2019 was 1 267.9 ind·h^-1, and the average biomass was 9.58 kg·h^-1, and invertebrate abundance and biomass were significantly different between months (<italic>P</italic><0.05), and there was no significant difference between stations (<italic>P</italic>>0.05), and there were characteristics of changes over time. Based on the analysis of the generalized additive model, temperature, oxidation reduction potential and dissolved oxygen were the main environmental factors affecting invertebrate abundance (<italic>P</italic><0.05). Results of this study can provide a systematic reference for the investigation of fishery resources in the coastal waters of Tianjin.

The growth of fish is usually affected by the size and type of bait, feeding frequency, feeding rate and the ability of fish to absorb nutrients. Recent studies have found that feeding frequency is one of the key factors affecting the growth performance of fish. In this study, juvenile <italic>Siganus canaliculatus</italic> was used as the research object. The growth indices, muscle crude nutrients and serum biochemical indices were measured at different feeding frequencies. According to the physiological and biochemical indices of the fish body, the growth benefit under each feeding frequency was evaluated. The purpose is to find out the scientific feeding frequency for juvenile <italic>Siganus canaliculatus</italic>, and to provide the corresponding theoretical basis and scientific support for the actual production of <italic>Siganus canaliculatus</italic> and other fishes. To investigate the effects of feeding frequencies on the growth and physiology of juvenile <italic>Siganus canaliculatus</italic>, four feeding frequencies (1 meal·d^-1, 2 meals·d^-1, 3 meals·d^-1, 4 meals·d^-1) were set, marked as F1, F2, F3 and F4. Three parallel groups were set in each group for 16 weeks in a microfluidic breeding tank (effective volume 125 L). Results of the study showed: 1) Growth indicators: Body weight and body length in each group increased linearly with the breeding time, the growth trend was similar between F3 and F4. The feeding rate and feed conversion ratio were the highest in F3, significantly higher than those of F1 (<italic>P</italic><0.05). The hepatosomatic index of F4 was significantly higher than that of F1 (<italic>P</italic><0.05), and ratio of intestine weight to body weight and ratio of intestine length to body length of F1 were significantly higher than those of F4 (<italic>P</italic><0.05), condition factor of F3 and F4 was significantly higher than that of F1 and F2(<italic>P</italic><0.05). 2) Muscle crude nutrition: The muscle moisture content of F1 was significantly higher than that of the other three groups (<italic>P</italic><0.05), while the muscle crude protein content of F1 was significantly lower than that of the other three groups (<italic>P</italic><0.05). The muscle crude ash content of F2 and F3 was significantly higher than that of F1 and F4 (<italic>P</italic><0.05). 3) Serum biochemical indicators: The contents of glucose and total cholesterol were not significantly affected by feeding frequencies. The content of total protein (TP) of F2 and F3 was significantly higher than that of F1 and F4(<italic>P</italic><0.05), while the content of albumin (ALB) of F1 and F4 was significantly higher than that of F2 and F3 (<italic>P</italic><0.05). The content of triglyceride(TG) increased significantly with the breeding time (<italic>P</italic><0.05). The content of high-density lipoprotein (HDL) was the highest in F4, significantly higher than that of F1 and F2 (<italic>P</italic><0.05), and the content of low-density lipoprotein (LDL) of F4 was significantly lower than that of other three groups(<italic>P</italic><0.05). The activity of aspartate transaminase (AST) and alanine aminotransferase (ALT) was significantly lower than that of the other three groups (<italic>P</italic><0.05). Results showed that the optimal growth benefit could be gained at the feeding frequency of 3 meals·d^-1.

In order to investigate the effect of intestinal bubble accumulation on the antioxidant capacity of silver pomfret <italic>Pampus argenteus</italic>, fifteen diseased fish were chosen as diseased group[(11.7±0.8)cm, (42.8±4.1)g] and fifteen healthy fish as control group [(12.5 ± 0.7)cm, (48.6 ± 5.6)g]. These fish were collected from Fuding research center of East China Sea Fisheries Research Institute in March 2019. Liver, kidney, muscle, and gill tissues of each group were collected and used to test their superoxide dismutase activity, catalase activity, malondiadehyde content and total antioxidant capacity, and kidney and gill tissues of each group were collected and used to test their lysozyme activity. The experimental results showed that the total antioxidant capacity of liver, gill and kidney of the diseased fish group decreased, and it decreased significantly in the liver and kidney(<italic>P</italic> <0.05), and the total antioxidant capacity in muscle was significantly higher than that in the control group (<italic>P</italic><0.05); the activity of superoxide dismutase and catalase in liver and muscle of the diseased group was significantly lower than that in the control group (<italic>P</italic><0.05); the malondiadehyde content in liver and muscle was significantly higher than that in the control group (<italic>P</italic><0.05), but the malondiadehyde content in gill and kidney were significantly lower than those in the control group (<italic>P</italic><0.05); lysozyme activity of gill was significantly higher than that in the control group (<italic>P</italic><0.05). Results show that: 1) During the intestinal bubble accumulation, the antioxidant enzyme activity of liver and muscle tissues of <italic>Pampus argenteus</italic> is impacted strongly. The antioxidant enzyme activity indicators of these two tissues can be used for the detection and pathological analysis of the disease; 2) The accumulation of bubbles in fish intestines is likely to be accompanied by bacterial infections, but still needs further verification.

The growth, development and maturation are comprehensively affected by age, total length, sex hormone and so on in teleosts. The blacktip grouper <italic>Epinephelus fasciatus</italic> is an important and valuable marine economic species widely distributed in the coastline of east Asian countries. Recently, with the global warming and increase of sea water temperature in the coastline of Japan, the time of growth, development and maturation of this species has become shorter than before while the size of growth and maturation has become smaller than before. Therefore, the access to information and research work on the growth, development and maturation of this species becomes very important and indispensable in the coastline. To understand the interrelation between total length(TL), age, sex maturation, and sex reversal, <italic>Epinephelus fasciatus</italic> was captured in the coastline of Nagasaki city in Japan from July 2015 to June 2018. The TL, body weight, age, sex, gonadal developmental maturity, and gonadosomatic index (GSI) were measured and calculated. In addition, the changes of 17β-Estradiol (E₂) content in the serum were analyzed. The results indicated that the mature proportion and GSI of female <italic>Epinephelus fasciatus</italic> individuals reached the peak in July, suggesting that the sexual mature timing of this species might be in July. The mature female <italic>Epinephelus fasciatus</italic> individuals were firstly detected at 3 years old, and the TL was about 24.5 cm. Accompanied with the increase of TL, the quantities of the mature individuals gradually increased, which indicated that the age of the first sex maturation was at 3 years old in this species. In addition, at 3 and 4 years old in female <italic>Epinephelus fasciatus</italic>, the E₂ content in the mature individuals was significantly higher than that in the immature individuals (<italic>P</italic><0.05), suggesting that E₂ played an important role in inducing oocyte maturation in this species. The intersex individuals were detected at about 35.7 cm and 9 years old, and the male individuals were detected at about 36.7 cm and 7 to 12 years old. In summary, the sexual mature timing of the <italic>Epinephelus fasciatus</italic> in the coastline of Nagasaki city in Japan was in July, which was closely related to the increase of E₂ content. The first sex maturation and sex reversal were at 3 years old or 7 to 12 years old, respectively. Based on the investigation of <italic>Epinephelus fasciatus</italic> in the coastline of Nagasaki city, the interrelation between total length, age, sex maturation and sex reversal was studied to provide the basic biological data and theoretical basis for resource conservation and artificial propagation.

In order to test the method of culling male and pseudomale seedlings of <italic>Cynoglossus semilaevis</italic> at 70 dph according to morphological differences between different sex to improve the female percentage in the population, a total of 349 seedlings of <italic>Cynoglossus semilaevis</italic> at 70 dph were randomly collected from a farm in Tianjin in 2019. Genomic DNA were extracted from the tail fin of each sample, and the sex specific gene loci of <italic>Cynoglossus semilaevis</italic> were used to accurately identify the genetic and physiological sex of each sample. In order to eliminate the influence of individual differences on the data and facilitate the difference comparison and data continuity, the data were standardized, and the angle value was converted into length by tangent for analysis. A total of 5 morphological traits were obtained, including full length (FL), body height (BH), full length/body height (FL/BH), caudal angle tangent (CT), dorsal at a horizontal angle tangent (DT). Principal component analysis was performed to analyze the morphological variation among different gender groups of <italic>Cynoglossus semilaevis</italic>. The discriminant equations of <italic>Cynoglossus semilaevis</italic> at 70 dph were established for female, male and pseudomale with linear discriminant analysis, and the accuracy of discriminant equations were verified according to the genetic gender information of the established equations. Results showed that the morphological traits of each gender group were normally distributed, and homogeneous in variance (<italic>P</italic>>0.05). The analysis of variance and principal component analysis of morphological characters of <italic>Cynoglossus semilaevis</italic> showed that the differences between males and females were mainly concentrated in body length and body height, and the mean values of body length and body height of females were higher than those of males and pseudomales. The discriminant accuracy of females and males was 37% and 85%, respectively by using various standardized indicators. It was very difficult to discriminate pseudomales, because they were close to males. Results showed that the accuracy of male identification was relatively high, which could meet the requirements of early gender observation and identification of seedlings to improve the female percentage of <italic>Cynoglossus semilaevis</italic>. Therefore, it is suggested to postpone the culling of seedlings of <italic>Cynoglossus semilaevis</italic>, such as at 120 dph, when the sex of the fish is completely differentiated. But it will increase the breeding costs simultaneously, therefore, tradeoff should be considered comprehensively to maximize the benefits.