Abstract:The natural population of the endangered Chinese sturgeon (), a first-class protected aquatic fish in China, declined sharply recently in the Yangtze River, because of human activities such as dam construction, overfishing, and pollution. The wild breeding groups consisted of less than 100 individuals, and the natural reproductive behavior became irregular under the Gezhou Dam, the only discovered spawning site. Since the ecological environment of the Yangtze River cannot be restored in a short time, the best way to recover the natural population is to build artificial breeding groups and release cultured fish. The Chinese sturgeon is a typical anadromous fish with large body size, a long lifespan, and a high sexual maturity age; thus, it is challenging to cultivate this fish under artificial conditions, which requires time, investment, and material resources. Since the 1970s, many conservation studies on Chinese sturgeons have been conducted. The wild Chinese sturgeon was induced successfully for the first time in 1976 in the Jinsha River, a tributary of the upper Yangtze River, by the Fisheries Investigation Team of Sichuan. In 1983, the first year after the cutoff of the river by the Gezhou Dam, the wild fish was induced successfully under the Gezhou Dam by the Yangtze River Fisheries Research Institute (YFI). In 1997, with the advent of the technology of large-scale juvenile fish cultivation, large-scale artificial breeding groups (the first generation, F₁) gradually established. In 2012, the artificial propagation of the F₁ generation was successfully conducted by YFI, and a second generation (F₂) was acquired for the first time. The artificial breeding groups of Chinese sturgeon have been established following more than 30 years of efforts and systematic studies and comprise individuals belonging to a certain age echelon. Previous studies indicated that the reproductive capacity of the wild Chinese sturgeon has been in decline over the past 30 years. In this study, the reproductive biology characteristics of cultured F₁ , which hatched between 1998 to 2008, were analyzed. A total of 492 fish, between the ages of 10 and 20 years, were counted. The body weight was 30 to 169 kg, the body length 140 to 258 cm, and the condition factor was 0.77 to 1.26. The relationship between body length and weight was determined as =0.9076, =492). In total, 74 fish were almost reaching gonadal maturation; the mature proportion was 15.04%. The body weight and body length of the mature male fish were (60.73±14.53) kg and (172.27±13.46) cm, respectively, and were significantly lower than the female fish with (88.39±29.14) kg and (193.37±18.90) cm, respectively. The minimum age of sexual maturation for the male fish was 10 years, with an average of (14.96±1.93) years, while the minimum age for the female was 12 years, with an average of (17.84±1.80) years. Both mature male and female fish were induced successfully every October to November from 2012 to 2018 when the water temperature was between 17.5℃ and 20.5℃. The success rate of inducing the mature male fish was 76.36%, the swirling movement time of the sperm was (49.11±13.38) s, and the sperm life was (220.75±56.47) s. The success rate of inducing the female fish was 57.89%, the egg quantity, egg diameter, and egg weight were (13.43±6.79)×10⁴ ind, (3.97±0.15) mm, and (0.046±0.013) g, respectively. The fertility rate, hatching rate, and quantity of hatched-out larvae were (42.72±27.82)%, (51.61±32.41)%, and (4.44±5.67)×10⁴ ind, respectively. Compared with wild has a smaller body size and decreased fecundity, indicating that its preservation will be faced with challenges. The fundamental data in this study will contribute to further large-scale artificial propagation of the Chinese sturgeon.

Abstract:In this study, we aimed to examine the relationship between the pancreatic alpha-amylase gene 5' flanking sequence and the feeding habits of fish by analyzing the differences of alpha-amylase gene transcription factors in different fishes. Pancreatic alpha-amylase gene 5' flanking sequences were obtained from a total of 32 fish species. Five of them were obtained by PCR and the remaining were obtained by searching the NCBI database. The length of the obtained 5' flanking sequences was 824 bp. Then, the transcription factors and phylogenetic relationship analyses were carried out for these pancreatic alpha-amylase gene 5' flanking sequences. Fishes were divided into herbivores, omnivores, and carnivores, according to their different trophic positions. The percentage similarity analysis was used to study the differences in the composition of transcription factors in fishes with different feeding habits. The similarity of the pancreatic alpha-amylase gene 5' flanking sequence among different fishes was very low. The pancreatic alpha-amylase gene 5' flanking sequences of 32 fish species contained a species transcription factor that ranged from 40 to 98. The results of the percentage similarity analysis showed that there were differences in the transcription factors of pancreatic alpha-amylase gene 5' flanking sequences among fishes with different feeding habits. Differences between the Herbivore and Carnivore groups were mainly found in the E47, C/EBPalpha, NF-Y, and Pax-2 transcription factors. Differences between the Herbivore and Omnivore groups were mainly found in the deltaEF1, MyoD, NF-Y, AREB6, and Pax-2 transcription factors. Differences between the Omnivore and Carnivore groups were mainly found in the GATA-1, SRY, MyoD, HFH-8, AREB6, Pax-2, STAT5A, and AP-1 transcription factors. These transcription factors play an important role in glucose metabolism and can enhance or inhibit gene expression. In liver glucose and lipid metabolism, the E47 and GR transcription factors act jointly as metabolism promoters and enhancers. In the regulation of gluconeogenesis, C/EBPalpha and FOXO1 act together on the IRE controlled promoter to regulate the expression of target genes such as PCK1 and G6PC. Transcription factor NF-Y plays an important role in promoting glucose metabolism. The phylogenetic tree results were generally consistent with the traditional morphological taxonomy. Fishes with the same feeding habits did not cluster together in the phylogenetic tree. The results indicated that there were several transcription factors in the pancreatic alpha-amylase gene 5' flanking sequences that were related to the feeding habits of fish. There is a certain relationship between transcription factors and the dietary differentiation of fish.

Abstract:In this study, we evaluated the effects of acute temperature and salinity change on the survival and immune function of Iwagaki oysters (). We measured the oysters' survival rates, superoxide dismutase (SOD), catalase (CAT), alkaline phosphatase (AKP), and lysozyme (LSZ) activities, and their malond­ialdehyde (MDA) content after they were transferred to environments with five different temperatures (15℃, 19℃, 23℃, 31℃, and 35℃) and six different salinity levels (16, 20, 24, 28, 36, and 40). In the temperature experiment, the minimum survival rate (34.44%) was observed at 35℃ and the survival rates of were higher in other treatments. At 15℃, the SOD, CAT, AKP, and LSZ activities were at low levels and the MDA content reached its highest value (46.93 nmol/mg pro). By contrast, the SOD, CAT, AKP, and LSZ activities and the MDA content in the treatment groups, reached their highest levels after acute temperature stress, then they decreased gradually to the control group level at 19℃, 23℃, and 31℃. In the salinity experiment, the minimum survival rate (71.11%) was observed at a salinity level of 40, which was significantly different from other treatments (<0.05). The 20, 24, 28, and 36-acute treatment salinity levels were suitable for the survival of The SOD, CAT, AKP, and LSZ activities were significantly lower than the control group (<0.05) and the MDA content reached its highest value (45.76 nmol/mg pro) on salinity level 16 for 144 h. The results demonstrated that acute changes in temperature and salinity had significant effects on the SOD, CAT, AKP, and LSZ activities as well as on the MDA content and survival rate of . Iwagaki oysters could adapt to seawater temperatures of 19℃, 23℃, and 31℃-acute treatment and 20, 24, 28, and 36-acute treatment salinity levels.

Abstract:In this study, suspended growth reactors (SGRs) were used to evaluate the effect of floc particle size on nitrification and assimilation capacity. In bioflocculation, there are flocs of various sizes; the size of the bioflocculation is affected by the aeration intensity and the osmotic pressure and the size of the floc is adjusted to achieve the strongest water treatment capacity. Therefore, the differences between flocs of different sizes and their role in water treatment are worth exploring. The purpose of this study was to investigate the effect of floc particle size on assimilation, nitrification, and nutrient values. Three treatment groups were set up; the <50 μm particle size group, the >50 μm particle size group, and the unscreened group. Under nitrification conditions, the total ammonia nitrogen (TAN) removal rates of the unscreened group, >50 μm group, and <50 μm group were (1.33±0.01) mg TAN/(g TSS·h), (1.62±0.04) mg TAN/(g TSS·h), and (1.64±0.06) mg TAN/(g TSS·h), respectively; under assimilation conditions, the TAN removal rates of the three groups were (2.83±0.08) mg TAN/(g TSS·h), (3.34±0.12) mg TAN/(g TSS·h), and (3.52±0.12) mg TAN/(g TSS·h), respectively. There were no significant differences in the TAN removal rates, nitrite nitrogen (NO₂^--N), nitrate nitrogen (NO₃^--N), and total nitrogen (TN) between the >50 μm and the <50 μm group (>0.05). We also measured the dissolved organic carbon (DOC), crude protein, crude fat, amino acids, fatty acids, crude ash, carbon to nitrogen ratio (C/N), volatile suspended solids (VSS), specific oxygen uptake rate (SOUR), and other indicators. The total fat content was higher in the >50 μm group and the crude protein content was higher in the <50 μm group. Our results showed that the floc particle size had no significant effect on the nitrification and assimilation reactions; under different reaction conditions, the floc particle size affected the nutritional value of bioflocculation and it also affected greatly the microbial community composition. Our results also showed that sieving might have had some effect on the flocs. This effect was greater than the influence of the different floc particle sizes. Sieving may have enhanced the microbial activity in or changed the morphology of bioflocculation. However, structural changes in bioflocculation require further verification. We conclude that the particle size had no significant effect on the nitrification and assimilation reactions and had a significant effect on the nutritional value of bioflocculation. This study has the potential to effect changes on the management of biological flocculation systems. The effects of floc size on microbial composition, nitrogen conversion, and nutrient composition should be studied further.

Abstract:A better understanding of the behavior of offshore fishing fleets is required in order to prioritize and enforce fisheries management and conservation measures worldwide. Satellite-based Automatic Information Systems (S-AIS) are now commonly installed on most ocean-going vessels and have been suggested as a novel tool to explore the movements of fishing fleets in near-real time. The fishing behavior and effort of vessels determined by vessel speed data obtained from AIS could assist in fishery resources analysis. In this study we used AIS data extracted from exactEarth Shipview^TM and fishing log data of longline vessels in the Western and Central Pacific Ocean; both types of data were collected from October to November 2017 and were analyzed together in order to establish a vessel status recognition model by evaluating the speed and heading characteristics of longline fishing vessels. The fishing effort model was defined, and the fishing intensity information of the fishing grounds was calculated based on the output of the fishing activity identification model. In order to test the fishing effort rationality data extracted from AIS, the spatial correlation coefficients of the fishing intensity obtained from AIS data mining and the catch per unit effort (CPUE), the total number of tuna, the total catch weight, and hook numbers were calculated. Our results indicated that the speed of longline vessels was mostly between 3 to 9 knots while fishing. The heading ranges of longline vessels were between 0 to 10° and 300 to 360°. The fishing activity was classified based on the speed and heading of vessels; the accuracy of the fishing vessel status classification was 68.29%. The spatial correlation of fishing intensity between threshold classification and logging was high (>0.96, <0.000001). The spatial distribution characteristics of the fishing intensity based on AIS were similar to the actual ones but lower than later. The spatial correlation coefficients of the fishing intensity obtained from AIS and CPUE data, the total number of tuna, the total catch weight, and hook numbers were all greater than 0.62 (<0.00001). Data on the fishing intensity of fishing vessels obtained from AIS could provide high-resolution information for scientists and decision makers and could be used as alternative data in fisheries stock assessment and management.

Abstract:Feeding is an important behavior for the growth and reproduction of fish. The nutrient niches of different areas and the distribution of main feeding grounds can be understood by analyzing the spatial heterogeneity of the feeding habits and growth rates of fish species. Based on samples collected from bottom trawl surveys in Haizhou Bay during the springs of 2011 and 2013-2016, the feeding habits of were studied by analyzing their stomach contents. The spatial heterogeneity of feeding habits and feeding grounds was identified by analyzing the distribution of and its major prey species. The results showed that prey items of included 20 species, with decapoda and amphipoda being the most predominant prey taxa. Based on stomach content and bottom trawl survey data, eight major prey items, including Alpheus distinguendus, Metapenaeopsis dalei, were selected to examine the spatial heterogeneity of the feeding habits and feeding grounds of % for the eight major prey items were 35.95%, 55.67%, and 44.59%, respectively. The spatial heterogeneity of feeding habits indicated that . Compared with results from previous studies, our results showed that the dominant prey items of had changed; this change was not only affected by the inter-species relationships in the ecosystem, but also by the fluctuation in the abundance of dominant prey items in Haizhou Bay. In addition, according to the abundance of these major prey items, the survey stations were divided into two areas (area I and area II) based on hierarchical cluster analysis. Except for , the abundance of the other six prey items in area I was higher than that in area II. In area I, the body length of ranged from 52 to 125 mm, their average body length was (86.67±0.28) mm, their body weight ranged from 2.15 g to 33.76 g, and their average body weight was (11.94±0.12) g. In area II, the body length of the ranged from 47 to 138 mm, their average body length was (95.80±0.12) mm, their body weight ranged from 1.74 g to 39.59 g, and their average body weight was (14.75±0.05) g. Our results showed that the <0.05), whereas in area II (2.90) it was significantly lower than 3 ( and its eight major prey species were more abundant in the 10~20 m depth sea area in the center of Haizhou Bay; the abundance of prey in the 10~20 m depth sea area in the center and south of Haizhou bay (area I) was higher than that in other areas ( in this area were smaller and fast-growing. Therefore, this area was identified as the feeding and nursery ground of in Haizhou Bay during the spring.

Abstract:In this study, we analyzed the species composition, ecological distribution, and spatial, diurnal, and interannual variation of zooplankton in the Yangtze River Estuary in the summers of 2017-2018. We used a 24 time-series analysis, a section stations survey, and the canonical correspondence analysis (CCA) to reveal the relationship between the abundance of dominant groups and the environmental variables. The results showed that there were 49 and 50 zooplankton species in the summers of 2017 and 2018, respectively, of which, Sagitta enflata, and were the dominant species. The SIMPER analysis indicated that the main contributors to the interannual variation of the zooplankton community were , and Thaliacea. CCA analysis showed that the surface temperature, bottom salinity, and surface chlorophyll a were the main environmental factors affecting the interannual variation of zooplankton groups, explaining 47.51% of the two-year zooplankton variation. Based on the spatial distribution of chlorophyll a in 2018, the stations were divided into chlorophyll a frontal and non-frontal area, which contained the L1-L2 and L3-L4 stations, respectively. The main contributors to the spatial differences of the zooplankton community were Euchaeta concinna. CCA analysis showed that the bottom salinity, bottom temperature, and surface chlorophyll a were the main environmental factors affecting the spatial variation of zooplankton groups, accounting for 56.31% of the variation in the composition of zooplankton in 2018. The results indicated that the different runoffs of the Yangtze river, diluting the water and causing changes in salinity and chlorophyll a, had an important impact on the interannual variation of the zooplankton community.

Abstract:The neon flying squid (), found in the Northwest Pacific Ocean, is a species of great economic importance. It is mainly caught by fishing fleets from and consumed in China (including Taiwan), Japan, and other countries and regions. The winter-spring cohort of is a short-lived species with a lifespan of about one year. The abundance and distribution of are influenced by global climate change and local marine environmental changes, such as El Nia events, Pacific interdecadal oscillation, currents, sea surface temperature (SST), chlorophyll-a (Chl a) concentrations, etc. The monthly potential habitat distribution of neon flying squid in the Northwest Pacific Ocean during the peak fishing season (July-October) was explored by using maximum entropy (MaxEnt) models; these models were fitted with squid fishery data obtained from Chinese commercial squid-jigging vessels from 2011 to 2015 and five oceanographic environmental factors derived from remote sensing data (SST; Chl a concentration; net primary productivity, NPP; mixed layer depth, MLD; sea level anomaly, SLA). The accuracy of the monthly MaxEnt models was evaluated by the area under receiver operating characteristic (ROC) curve (AUC). The simulated by a different MaxEnt model for each month, were imported into ArcGIS for visual analysis. The values obtained from probabilistic modeling were defined as habitat suitability index (HSI) and divided manually. When HSI>0.6, the sea area was considered as the most suitable area for ; when 0.4

Abstract:Ever since the Antarctic waters began to cool about 20 million years ago, Antarctic notothenioid fishes, comprising more than 120 species, have been living in the stable, extremely cold, and oxygen-rich Antarctic waters, when all other temperate fishes gradually disappeared. In order to survive the coldest area in the world, Antarctic notothenioid fishes have evolved many adaptive changes in their biochemical and physiological functions; among these changes, the origin and evolution of antifreeze proteins is one of the most important adaptations of Antarctic fishes. Antifreeze proteins are a family of macromolecules that are essential for survival in extreme cold conditions. For the time being, at least one antifreeze glycoprotein (AFGP) and four structurally different antifreeze protein (AFPs) types, known as AFP I, AFP II, AFP III, and AFP IV, have been identified from polar and subpolar fishes. Although these AFPs have similar structures and functions, their origin and evolution are significantly different. AFPs have also been found in insects, plants, and bacteria living in cold habitats. In fish, AFPs are typically secreted into the blood and also produced in the skin, scales, fin, and gills. AFPs cause ice recrystallization inhibition and contribute to non-colligative freezing point depression by binding to small ice crystals in order to inhibit their growth. AFPs can reduce the freezing point of Antarctic notothenioid fishes' body fluids to -2.2℃; this preserves the fluidity of body fluids at sub-zero temperatures and protects fishes from freezing damage. Due to the natural biological properties of AFPs, such as the thermal hysteresis activity (THA) and the inhibition of ice recrystallization activities (IRI), they have several commercial applications. AFPs can be used in the food industry for food preservation and ice cream production; they can also be used in the agricultural and biomedical fields to freeze and preserve a wide variety of biological samples including body tissues (cells, organs, embryos, and gametes) of human beings, animals, and fishes. Additionally, AFP transgenic plants show enhanced cold tolerance. Studies have demonstrated that AFPs are up to 300 times more effective than traditional antifreeze chemicals at the same concentrations and they can improve post-thaw viability regardless of the freezing method. Since AFPs show promising potential application prospects in the fields of medicine, food industry, agriculture, etc., there has been an accumulation of relevant published research recently. In this paper, the evolution, function, application, and current concerns regarding the use of AFPs were reviewed.