This study documents the data of fish species systematically collected in the off southern Zhejiang, East China Sea, from November 2015 to August 2016, according to Nelson’s classification system and analyzed the diversity at different taxonomic levels. The inclusion index at taxonomic level (TINCL _i ), taxonomic diversity (the average taxonomic distinctness △⁺ and the variation in taxonomic distinctness ∧⁺) are used in this study. The results show that the fish species in the waters belonged to 18 orders, 78 families, 130 genera and 182 species. It is concluded that the number of species in spring (104 species) is larger than that in autumn (103 species) and winter (93 species), while the smallest number occurs in summer (88 species). Analyzed by TINCL _i , the average numbers of (families, genera, species), (genera, species) and (species) per order, family and genus are (4.33、7.22、10.11), (1.67、2.33) and (1.40). The △⁺ and ∧⁺ in the off southern Zhejiang, East China Sea, are 62.9 and 77.0, respectively. The △⁺ in our study area is less than those in the high latitude areas, such as the Yellow Sea and Bohai Sea (66.4), the coastal waters off Shandong (66.1), and is greater than those in the lower latitude waters including the Nansha Islands (56.6), the Xisha Islands (60.2) and the Dongsha Islands (55.2). The results above indicate that the △⁺ decreases with latitude. This study analyzed taxonomic diversity of fish species in the off southern Zhejiang, East China Sea, which can provide reference for the exploitation and conservation of fish species in local waters.

Catch-MSY method can temporarily replace conventional stock assessment models in making management decisions for a data-limited fishery, even when only catch data are available. In this study, for the sensitivity analysis and assessment of the Indian Ocean blue marlin, we established 15 scenarios based on non-informative and informative prior distributions of the intrinsic growth rate r and carrying capacity K. Sensitivity analysis reveals a high negative correlation between parameters r and K, and the estimated maximum sustainable yield (MSY) increases with r. Sensitivity analysis shows that the length of catch time series has less influences on the results of the assessments, but the assessments are sensitive to catch data in the first and last year. The assessment results reveal that the status of total biomass is optimal, with the ratio of B ₂₀₁₅ to B _MSY higher than 1. Exception is only two scenarios, the exploitation status under the other scenarios would be overfishing, since all the ratios of F ₂₀₁₅ to F _MSY would be higher than 1. Projections of future stock status show that, to attain the objective of maintaining B/B _MSY>1 with a probability of higher than 50% in the next 10 a, the catch would have to be reduced to 90% (13 860 t) of the current level. Considering that the catch-MSY method is conservative under data-limited conditions, maintaining 100% to 110% (15 400–16 940 t) of the current catch could achieve the objective of maintaining B/B_MSY >1 with a probability of higher than 50% in the next 5 a.

Phytoplankton, as the base of the oceanic food chain, plays a fundamental role in marine ecosystems. Since the Bohai Sea, the largest inner sea in China, is an important spawning ground and nursery field as well as a feeding ground for marine creatures, it is critical to understand variations of phytoplankton in the area. Chlorophyll a (Chl a) concentration is an important proxy for phytoplankton biomass. Chl a derived from both the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) from 1997 to 2010 and the MODerate resolution Imaging Spectroradiometer (MODIS) sensor on satellite Aqua from 2002 to 2018 were combined into one time series to investigate the spatial and temporal variability of Chl a concentrations in the Bohai Sea using Google Earth Engine. Annual Chl a concentrations increased significantly by 14.1% in the study area over the past two decades. Chl a concentrations in every season and in all months except November have stagnated or increased. Chl a concentrations increased mainly in the middle part of the sea. Sea surface temperature (SST), wind speed and precipitation were also analyzed. Increases in precipitation over the land around the Bohai Sea and wind speed in summer, as well as decrease in SST in autumn, all contributed to the rises of Chl a concentrations. Nutrients from land may play an important role in phytoplankton growth.

In order to further study the metamorphosis development and growth characteristics of the hybrid offspring of Epinephelus lanceolatus♀×E. tukula♂, we measured embryonic development time, fertilization rate, deformity rate, hatching rate and growth traits (full length, body length, height and anal front) of the hybrid offspring and E. lanceolatus. We also observed the absorption process of yolk sac and oil globule, the growth and contraction of the second dorsal spine and pelvic fin spine, and the changes of eye diameter and oral fissure during embryonic development of hybrid offspring. Statistical analysis of the data was performed. The results show that the hybrid offspring and E. lanceolatus complete embryo development at 21 h 24 min and 21 h 32 min at 28℃, respectively; the fertilization rate, deformity rate and hatching rate of hybrid offspring are 89.09%±0.08%, 35.16%±5.05% and 62.59%±10.70%, respectively, no significant difference is shown compared with that of E. lanceolatus. According to the morphological changes of yolk sac, second dorsal spine, pelvic fin spine, scales and body color, the post-embryonic metamorphosis is divided into early larvae (0–6 d after hatching), late larvae (7–34 d after hatching), juveniles (35–46 d after hatching) and juvenile fish period (47–86 d after hatching). The growth of the early larvae is slower, while the growth of the larvae to the juveniles increases gradually. At 86 d after hatching, the body lengths of the hybrid offspring and E. lanceolatus reach (60.80±0.50) cm and (51.80±0.47) cm, which indicates the growth of the hybrid offspring is significantly faster than E. lanceolatus (P<0.01). During embryo development, the yolk sac consumption is 29.45%, the oil ball consumption is 20.75%, and the yolk sac consumption is the fastest at 1 d after hatching, reaching 58.70%. The oil globule consumption is the fastest at 3 d after hatching, reaching 32.08%, and the yolk sac and oil globule of the larvae are basically absorbed at 5 d after hatching. The lengths of the second dorsal spine and pelvic fin spine reach the longest of (8.15±0.02) mm and (5.80±0.10) mm at 29 d after hatching respectively, and they completely degenerate at 47 d after hatching which marks the completion of metamorphosis. The eye diameter of the larvae is (0.16±0.01) mm at 1 d after hatching, which increases by 22 times at 86 d after hatching. The length of oral fissure is (0.09±0.02) mm, and it increases by 99 times at 86 d after hatching. The results show that the hybrid offspring of E. lanceolatus♀×E. tukula♂ develops normally, and the hybrid offspring shows a significant growth advantage comparing with its female parent. This study provides rich data for seed cultivation, development research and variety improvement of the hybrid offspring.

The Weixi’nan Sag is the important research area of exploration and development integration. This study takes the Weizhou Formation of the No.2 Fracture Zone as the research object. By analyzing the geometry, kinematics, and dynamics characteristics of fracture, the "slope-flat" fault system in the middle section and the "shovel-type" fault system on both sides are divided into the level 3 en-echelon main fracture zone, the level 4 branch fracture zone, and the level 5 branch fracture zone. The "slope-flat" fault system in the middle section is subjected to higher in-situ stress, and the main and branch faults are more developed. The vast majority of oil and gas are distributed in the "slope-flat" fault system. A comprehensive analysis of the relationship between the internal fracture system of the differential fault system in the No.2 Fracture Zone and the oil-gas distribution law is made, and obtains the corresponding regular of 3 aspects of fracture reservoir controlling mechanism and 8 types of fracture reservoir controlling patterns. Under the regular of fracture reservoir controlling mechanism and patterns, the search and evaluation of targets are carried out around the inner or surrounding oil fields of the No.2 Fracture Zone, and good results are obtained. Based on the field production, the potential targets of North 1, North 3 and North 4 in the middle part of the No.2 Fracture Zone are searched and optimized. The three blocks have been successfully drilled, and the purpose of the geological reservoir has been achieved. The regular of fracture reservoir controlling mechanism and patterns which have been applied to the potential zone of the No.2 Fracture Zone in the southwest depression play very good effect.

The spectral width of the electromagnetic scattering from sea surface is closely related to the SWH (significant wave height), and thus the spectral width can be used to retrieve the SWH. In this paper, the linear filtering method is employed to simulate the radial velocity of the orbit velocity of the each scattering element on sea surface. Based on the radial velocity, we establish a spectral width model, and analyze the influences of spatial resolution, time sampling length and SWH on spectral width. At the same time, we also discuss how to select the parameters such as time sampling length and the azimuth angle during the actual observation. Here, the theoretical results are compared with the estimated results based on the measured data required by the CSIR-X band radar. The comparisons demonstrate that the spectral width obtained by the estimation method based on Gaussian distribution standard deviation agree well with the theoretical results after eliminating the effects of radar noise and frequency leakage, which proves the reliability of the theoretical results. The results obtained in this paper have certain reference value for the retrieval of the SWH.

Simple Ocean Data Assimilation reanalysis and other data were used to explore seasonal variation characteristics of freshwater transport between the Arabian Sea (AS) and the Equatorial Western Indian Ocean (EWIO), and the Gulf of Oman (GOO). Freshwater budget in the AS is characterized by a basic balance and its seasonal variation is also present. Our results indicate that the amount of input freshwater from the EWIO and river discharge is roughly equal to the amount of freshwater output to GOO and lost caused by the evaporation overwhelming the precipitation (P–E). The lost freshwater via air-sea exchange (i.e. P–E) is compensated by freshwater flux from the EWIO and the Bay of Bengal (BOB), which plays a key role in maintaining the basic balance of salinity over the AS. Net freshwater flux in the AS is negative (i.e. lost freshwater) from January to June together with December, and positive (i.e. receive freshwater) during July and November with a maximum positive value in September. The seasonal variation characteristics of net freshwater flux in the AS shows a single remarkable peak. Along the 9°N section, freshwater exchange between the EWIO and the AS primarily occurs from the surface to 200 m depth, with a multi-year averaged net flux into the AS of about 0.1×10⁶ m³/s. From October to next March, the BOB low-salinity water extends into the AS at above 60 m depth through the southwest of the Indian peninsula. In summer and autumn, the transport associated with the Great Whirl located at the east of Somali Peninsula, is characterized by low (high) salinity water in the west (east) of the whirl transported northward (southward) into the AS (equatorial Indian Ocean). This transport during these two seasons is largest in a year with its influence can extend downward to about 300 m depth, which forms in June, then peaks in August and September, and finally decays rapidly in November. Water exchange between the AS and the GOO is relatively weak, and has a sandwich-like three-layer structure in vertical direction: high salinity water intrudes from GOO into the AS in the upper 10 m layer and in the bottom layer between 175 m and 400 m depth; whereas in the middle layer (i.e. 15 m to 170 m depth) low salinity water is transported from the AS to the GOO. On multi-year average, a net freshwater transport of about 0.39×10⁴ m³/s is further estimated into the GOO from the AS across the section along the GOO mouth.

Rare earth element (REE) in the surface sediments from Pahang River (28 samples) and Kelantan River (22 samples) in the eastern portion of Malay Peninsula are analyzed to decipher the characteristics of REE composition and distribution, to discern the controlling factors of REE composition, and to illustrate the significances of provenance tracing of REE. The results show that the total REE ranges from 24.88 μg/g to 304.29 μg/g, with an average of 165.22 μg/g, for the Pahang River; and 126.02 μg/g to 281.40 μg/g, with an average of 181.15 μg/g, for the Kelantan River, respectively. The UCC standardization of REE indicates that Pahang River sediments enrich with heavy rare earth elements, in relative to light rare earth elements. However, there is no significant difference between light and heavy rare earth elements in the Kelantan River. The composition of source rocks and minerals plays a controlling role in the REE composition of the two rivers. The influence of chemical weathering in the Pahang River is greater than Kelantan River, and the difference of grain size among the Pahang River sediments leads to larger REE variations. δEu_UCC-(Gd/Yb)_UCC discrimination diagram demonstrates that it can be used as an effective index to qualitatively seperate the sediment source of two rivers. It can further be used to trace and identify the source of sediments quantitatively on the continental shelf of Malay Peninsula.

Comparison with Geophysical Model Function (GMF) developed by methods of empirical statistics, ocean microwave scattering model works well at all microwave frequency. Composite radar backscattering model is comprised of Bragg scattering model and geometrical optics model. We calculated the normalized radar cross sections (NRCSs) from the composite scattering model by using the sea surface wind speeds and directions measured by buoys moored in the northern of South China Sea in the whole year of 2014, and then compared them with SAR on board RADARSAT-2 at C-band, microwave scatterometer on board HY-2A satellite (HSCAT) at Ku-band, respectively. The biases of comparison are (–0.22±1.88) dB ( for SAR), (0.33±2.71) dB (for HSCAT in VV polarization) and (–1.35±2.88) dB (for HSCAT in HH polarization), respectively. We also calculated the NRCSs from the model by using the sea surface wind speeds and directions measured by NDBC buoys in the time period from October 1, 2011 to September 30, 2014, and then compared them with radar altimeter on board Jason-2 and HY-2A both at Ku-band with the bias of (1.01±1.15) dB and (1.12±1.29) dB, respectively. Although the biases of NRCSs between space-borne sensors and composite scattering model in medium and normal incidence are different each other, the accuracies of their sea surface wind speed products are the same(i.e. the root mean square errors are all less than 1.71 m/s). The results show that we can simulate the sea surface radar NRCSs of satellite-borne SAR, microwave scatterometer, and altimeter by using the composite radar backscattering model, and the simulations are consistent with that of CMOD5, NSCAT-2 and the GMF of operational wind retrieval for altimeter. It also indicates that the composite radar backscattering model could be used in calibration and validation of microwave sensors and simulation of radar backscatter from sea surface.

By monitoring the typical profiles of the artificial cobble and sandy beach on Xiamen Tianquan Bay and Huizhan before and after the super Typhoon No.1614 Meranti, combined with the observation and numerical simulation of hydrodynamic factors, we calculate the wave field together with the total water level during the typhoon process, and analyze the morphology and the average variation of the profile. Results show that the characteristics of response to typhoon between artificial cobble and sandy beach on macro-tidal coast are significantly different. The majority of cobbles transported onshore, the beach face eroded while the beach berm accumulated to form a higher beach berm, and the slope of the artificial cobble beach is obviously steepened. In contract, the artificial sandy beach shows obvious sediment transport offshore, the upper beach face eroded and the lower beach face deposited, the slope of the beach face obviously become gentler, moreover the top of the beach berm become flattened due to the strong onshore wind after the typhoon landing, and the height of the beach berm almost remain unchanged. Whether the beach berm eroded during typhoon process is closely related to the total water level including astronomical tide, storm surge and wave run-up. During the process of typhoon, the artificial cobble beach characterized with higher wave energy and steeper beach slope showed less profile variation comparing to that of the artificial sandy beach. The artificial cobble beach performed a small degree of response to typhoon. Taken together, it is an effective approach of slowing sandy beach erosion by using gravels and other coarse-grained sediments for beach nourishment on strong eroded high-energy macro-tidal coasts.