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The regime of the Laptev Sea depends closely on the runoff of the Lena River. Microorganisms are essential components of aquatic food webs and play a significant role in polar ecosystems.

Antarctic krill (Euphausia superba) is Earth’s most abundant wild animal, and its enormous biomass is vital to the Southern Ocean ecosystem. Here, we report a 48.01-Gb chromosome-level Antarctic krill genome, whose large genome size appears to have resulted from inter-genic transposable element expansions. Our assembly reveals the molecular architecture of the Antarctic krill circadian clock and uncovers expanded gene families associated with molting and energy metabolism, providing insights into adaptations to the cold and highly seasonal Antarctic environment. Population-level genome re-sequencing from four geographical sites around the Antarctic continent reveals no clear population structure but highlights natural selection associated with environmental variables. An apparent drastic reduction in krill population size 10 mya and a subsequent rebound 100 thousand years ago coincides with climate change events. Our findings uncover the genomic basis of Antarctic krill adaptations to the Southern Ocean and provide valuable resources for future Antarctic research. Antarctic krill (Euphausia superba) is Earth's most abundant wild animal, and its enormous biomass is vital to the Southern Ocean ecosystem. Here, we report a 48.01-Gb chromosome-level Antarctic krill genome, whose large genome size appears to have resulted from inter-genic transposable element expansions. Our assembly reveals the molecular architecture of the Antarctic krill circadian clock and uncovers expanded gene families associated with molting and energy metabolism, providing insights into adaptations to the cold and highly seasonal Antarctic environment. Population-level genome re-sequencing from four geographical sites around the Antarctic continent reveals no clear population structure but highlights natural selection associated with environmental variables. An apparent drastic reduction in krill population size 10 mya and a subsequent rebound 100 thousand years ago coincides with climate change events. Our findings uncover the genomic basis of Antarctic krill adaptations to the Southern Ocean and provide valuable resources for future Antarctic research.

In this study, deposit- and district-scale three-dimensional (3D) fault-and-intrusion structure models were constructed, based on which a numerical simulation was implemented in the Jiaojia gold district, China. The numerical simulation of the models shows the basic metallogenic path and trap of the gold deposits using mineral system theory. The objective of this study was to delineate the uncertainty of the geometry or buffer zones of the ore-forming and ore-controlling fault-and-intrusion domains in 3D environment representing the exploration criteria extraction and the gold potential targeting in the study area. The fast Lagrangian analysis of continua in three dimensions was used as the platform to define the stress deformation fracture ore storage and the hydrothermal seepage channel zone based on the gold deposit features and metallogenic model in the study area. The validity of the numerical simulation was verified by comparing it with robust 3D geological models of the large Xincheng gold deposit. The potential targeting zones are analyzed for uncertainty and then evaluated by Boolean operation in a 3D geological model using the computer-aided design platform. The research results are summarized as follows. (1) In the pre-mineralization period, the Jiaodong fault’s left lateral movement created the Jiaojia network faults and formed a fracture zone with NW- to NNW-trending dips of 20° to 40°. (2) During the mineralization period, hydrothermal flow was associated with the intrusion geometry and features. However, it was constrained by the Jiaojia fault, which blocked the vadose flow into the upper wall rock and made the hydrothermal route close to the fault in the footwall fracture zones. (3) Three gold potential targets were identified by the numerical simulation results in the study area: the NW-trending Sizhuang gold deposit, the NW-trending zone of Jiaojia gold deposit, and the NE-trending zone of the Xincheng gold deposit. (4) The numerical simulation results show the fault-and-intrusion metallogenic domain and the hydrothermal alteration zones, which reflect the main ore-controlling and ore-forming factors of mineralization. The information obtained through the numerical simulation discussed here can be used to define exploration criteria in the study area.

Two surveys using a combination of midwater trawl and acoustics were undertaken in October 2014 and June 2015 to investigate species composition and biomass density of mesopelagic nekton over the continental slope of the South China Sea (CSSCS). In two surveys, diversity and dominant species of nektons (Chondrichthyes, Osteichthyes and Cephalopoda) showed obviously diel and depth–dependent difference. In 2014, in general species richness and diversity of nektons in the 0–100 m at night were greater than that in the 350–650 m during the day and 350–650 m at night. In Jun. 2015, species richness and diversity of nektons in the 350–650 m during the day were much greater than that in the 350–650 m at night and 0–100 m at night. Myctophidae and Diaphus are the most common fishes in the CSSCS mesopelagic zone. Jellyfishes could cause the nautical area scattering coefficient (NASC) to increase, but the effect of jellyfishes on NASC could vary over the light–night cycle and trawl depth. Catch rates of different nektonic categories varied by time of day and depth. Night–time catch rate at trawl depths

Mesopelagic fishes are major components contributing to deep-sea scattering layers in the open ocean. They have the potential to support a substantial higher trophic level harvest, but knowledge about this possible resource is still rudimentary. Some of the mesopelagic fishes undertake diel vertical migration (DVM) over large depths by feeding in shallow water during darkness and migrating to depth to avoid visual predators during daylight. The vertical distribution and diel migration pattern of the mesopelagic fishes on the northern slope of the South China Sea were investigated during two multidisciplinary surveys carried out in October 2014 and June 2015. Based on acoustic and biological sampling, a distinct deep scattering layer (DSL) consisting mainly of mesopelagic fishes was identified in deep water (>300 m). Extensive diel vertical migration for hundreds of meters to form dense aggregations in the epipelagic zone (0–150 m) at night was observed in both seasons, but the migration was highly species dependent. While most of the Myctophiformes and the Perciformes undertook DVM, most of the Salmoniformes and Beryciformes remained in deep water both day and night. Based on paired day-night differences of acoustic density in the DSL, the migrating proportion of mesopelagic backscatter varied markedly in different locations, ranging from 28% to 63%, with a mean of 48% in two seasons. The extensive vertical migration occurred in separate groups at different periods during sunset and sunrise hours. Additional analysis showed that the center of gravity of the mesopelagic backscatters (200–1000 m) and their night distribution in the subsurface layer (10–150 m) were positively correlated with the mean temperature in respective zones. Moreover, some of the mesopelagic communities on the slope were found to undertake pronounced diel horizontal migration in a pattern of towards the shore in the evening and away from the shore after midnight. The horizontal migrant species were mainly Myctophidae, in particular Diaphus chrysorhynchus and Diaphus garmani. Simultaneous analysis on typical tidal currents indicated that the horizontal migration, over a large distance with high speed and biomass, could not be explained by passive transport due to tidal currents alone, and the active swimming of the mesopelagic fishes may also play an important role.

To estimate the age and growth of a dominant species of lanternfish, Myctophum asperum, in the South China Sea, 399 fish were collected by a midwater trawl in spring and autumn, 2014–2016. Age was estimated using counts of daily growth increments laid down across the sagittal section of otoliths (n = 52 fish). Three regions of deposition in the otolith microstructure were clearly evident: the larval, post-larval and post-metamorphic zones. Increments in the larval zone (average of 30) and the post-metamorphic zone appeared brighter under a light microscope than the increments in the post-larval zone. The age of the sampled fish ranged between 183 and 405 days. The von Bertalanffy growth model provided the best fit for the post-metamorphosis fish and was expressed as: SL = 85.3[1-exp{− 0.008(t − 28.1)}]. The maximum rate of growth occurred at 183 days after metamorphosis and 58 mm SL among the age determined samples, and the growth rate decreased with age. The length-weight relationship for the entire sample of fish was W = 0.000037234 SL2.7935, whereas for females and males it resulted Wf = 0.000050140 SL2.7255 and Wm = 0.000035459 SL2.8022, respectively. Fish reached the adult size by 74 mm SL and 5–8 g, and this size group was numerically the most and constituted the greatest portion of the biomass.

The Jiaodong Peninsula hosts the main large gold deposits and was the first gold production area in China; multisource and multiscale geoscience datasets are available. The area is the biggest drilling mineral-exploration zone in China. This study used three-dimensional (3D) modeling, geology, and ore body and alteration datasets to extract and synthesize mineralization information and analyze the exploration targeting in the Zhaoxian gold deposit in the northwestern Jiaodong Peninsula. The methodology and results are summarized as follows: The regional Jiaojia fault is the key exploration criterion of the gold deposit. The compression torsion characteristics and concave–convex section zones in the 3D deep environment are the main indicators of mineral exploration using 3D geological and ore-body modeling in the Zhaoxian gold deposit. The hyperspectral detailed measurement, interpretation, and data mining used drill-hole data (>1000 m) to analyze the vectors and trends of the ore body and ore-forming fault and the alteration-zone rocks in the Zhaoxian gold deposit. The short-wave infrared Pos2200 values and illite crystallinity in the alteration zone can be used to identify 3D deep gold mineralization and potential targets for mineral exploration. This research methodology can be globally used for other deep mineral explorations.

This is an exploratory analysis combining artificial intelligence algorithms, fishery acoustics technology, and a variety of abiotic factors in low-latitude coastal waters. This approach can be used to analyze the sensitivity level between the acoustic density of fishery resources and various abiotic factors in the surface mixed layer (the water layer above the constant thermocline) and the bottom cold water layer (the water layer below the constant thermocline). The fishery acoustic technology is used to obtain the acoustic density of fishery resources in each water layer, which is characterized by Nautical Area Scattering Coefficient values (NASC), and the artificial intelligence algorithm is used to rank the sensitivity of various abiotic factors and NASC values of two water layers, and the grades are classified according to the cumulative contribution percentage. We found that stratified or multidimensional analysis of the sensitivity of abiotic factors is necessary. One factor could have different levels of sensitivity in different water layers, such as temperature, nitrite, water depth, and salinity. Besides, eXtreme Gradient Boosting and random forests models performed better than the linear regression model, with 0.2 to 0.4 greater R2 value. The performance of the models had smaller fluctuations with a larger sample size.

Little effort has been made to conserve the East Asian finless porpoise, which is hindered by a lack of robust baseline data on their population status and threats. We conducted a local ecological knowledge survey around south Bohai Sea to collect information about the spatio-temporal distribution, population trends, and threats to East Asian finless porpoises. Based on the local ecological knowledge of 186 fishermen, April and September were the two months when porpoises were most frequently sighted, while February, November and December were when sightings were rare. Western coastal of Laizhou Bay and southern regions around Yellow River Estuary were identified as hotspots for sightings. More than half of the fishermen reported an overall decline in population through increasing water pollution, lower food resources and sustained fishery bycatch. These results provide insights into the distribution pattern and seasonal trends of the East Asian finless porpoises living in south Bohai Sea, thereby providing useful information for local authorities tasked with protecting this endangered cetacean.

A fishery for Antarctic krill (Euphausia superba) has existed for over 3 decades and the Commission for Conservation of Antarctic Marine Living Resources (CCAMLR) manages this fishery using precautionary catch limits, fishery data collection and a scientific observer programme operating on the fishing vessels. A recent increase in the number of vessels fishing and the rising costs of undertaking scientific research cruises have focussed attention on being able to use fishing vessels to collect more extensive scientific data sets. In 2011, CCAMLR’s Subgroup on Acoustic Survey and Analysis Methods (SG-ASAM) was tasked with assessing the use of acoustic data collected from fishing vessels to provide qualitative and quantitative information on the distribution and relative abundance of Antarctic krill and other pelagic species. SG-ASAM conceived a proof of concept programme and implemented the first stage in 2013 to determine the current setup of acoustic equipment on participating fishing vessels and to establish whether these vessels could collect geo- and time-referenced acoustic data. To date data have been received from 7 krill fishing vessels and SG-ASAM has now focussed on the development of data collection protocols to enable fishing vessels to collect quantitative acoustic data along prescribed transects. While this development work continues, the willingness of fishing industry to participate in such studies has already been demonstrated by several fishing companies, and Norwegian- and Chinese-flagged fishing vessels are undertaking krill biomass surveys in two key fishery Areas in the South Atlantic sector of the Southern Ocean.

Otter boards are important device that provide a desired horizontal opening of a mid-water trawl net. High lift coefficients are essential for an otter board to maintain favorable fishing efficiency, especially for fishing target like Antarctic krill (Euphausia superba) which is often found in layers very close to the sea surface. Response surface method (RSM) was used to optimize the parameters of a rectangular cambered otter board in this study. The aspect ratio (0.8–2.0), maximum relative camber (2%–18%), and maximum camber position (10%–50%) were adopted as the independent variables. Hydrodynamic performances of twenty otter board models were simulated using numerical simulation. Results showed that RSM was applicable to describe the relationship between the selected variables and the maximum lift coefficient. The maximum lift coefficient was significantly affected by these three variables. An optimal otter was extracted in the optimal solutions, and the optimal parameters of aspect ratio, maximum relative camber and maximum camber position were 2.0, 15.5% and 35.1%, respectively. Under the optimal conditions, the maximum lift coefficient was improved by 20.5% compared with the initial otter board. The relative error differed by only 1.6% from RSM model predictions, which indicated the availability of the model experimentally.

Anchovy is a key species in the Yellow Sea ecosystem. An accurate estimate of anchovy abundance is vital for the management of the anchovy stock and measurement of the ecosystem response to changes in anchovy abundance. However, the acoustic fish abundance estimate may be biased by 30%–40% if the fat-content induced target strength variation is not taken into account. We measured the monthly variation in the fat content of anchovy (Engraulis japonicus) in the Yellow Sea, and evaluated the potential effect of variation in fat content on the acoustic assessment of anchovy abundance. The fat content of anchovy varied seasonally, with two maxima and two minima in a year. The highest fat content (14.75%) was measured in the pre-spawning period in May, and the lowest fat content (2.48%) was measured during the post-spawning period in October. Fat content appeared to correlate with water content, but not body size. Assuming that the target strength is decreased by 0.2dB for every 1% increase in fat content, the seasonal difference in the target strength of anchovy may be as high as 2.45 dB. Given this, the acoustic abundance estimate may be biased by between 43% and 76%. Our results highlight the need for more information on the changes in fat content of fishes whose abundance is estimated by acoustic surveys.

Zhao, X., Wang, Y., and Dai, F. 2008. Depth-dependent target strength of anchovy (Engraulis japonicus) measured in situ. – ICES Journal of Marine Science, 65: 882–888. Three sets of target strength (TS) data were collected in the southern part of the Yellow Sea using a calibrated, 38 kHz, Simrad EK500 split-beam echosounder. Midwater trawl sampling showed that >97% of the catch by number was anchovy (Engraulis japonicus), with total lengths ranging from 6 to 15 cm, and that the arithmetic-mean length and root-mean-square length were 10.6 and 10.8 cm, respectively. The mean TS of anchovy in the 10–45-m layer was estimated to be –50.9 dB, with a 95% confidence interval of (–51.0, –50.8) dB. The TS data showed, however, a clear depth-dependence that was very close to and not significantly different from what might be expected according to Boyle’s law. The TS model was estimated to be TS = 20 log L − 71.6 for the conventional relationship between TS and length, but TS = 20 log L− (20/3) log (1+z/10) − 67.6 when the depth (z, m) effect was included according to Boyle’s law. These results may have a significant influence on abundance estimates of anchovy derived from acoustic surveys, both in the Yellow Sea and in other parts of the world.

The target strength of hairtail (Trichiurus haumela) in the Yellow Sea was measured in situ with a 38 kHz, split-beam echosounder on 2 January 2001. The fish measured were of the 2000 year class, its anal length ranged from 62 to 115 mm, with a mean of 89.8 mm. The mean target strength of these young hairtail was estimated to be −49.2 dB, with a 95% confidence interval of (−49.4, −49.0) dB. This provided a rare and useful reference for the acoustic-abundance estimation of hairtail.

This paper addresses the problem of acoustic ‘‘shadowing’’ (i.e. first-order scattering) using an heuristic approach. It is shown that the relationship between the shadow coefficient – the proportional reduction of the acoustic energy due to the shadowing effect of fish (Zhao et al., 1993) – and the apparent area backscattering coefficient of the fish is practically linear, and that the linear relationship will hold true even with inhomogeneous fish distributions. Based on this finding a simple linear model for the estimation of the e/ (extinction cross-section/acoustic cross-section) ratio is developed. The model applies the reference target method of Foote et al. (1992), which allows the shadow coefficient to be determined. A model is also developed for compensation of the shadowing effect. This model can also be used to deduce the maximum-detectable fish density when the e/ ratio is known; and the maximumdetected apparent fish density may, in turn, suggest an upper limit of the e/ ratio under the specific survey condition. A correction table is provided to serve as an approximate reference and a registration from a typical herring survey is shown as an example. 2003 International Council for the Exploration of the Sea. Published by Elsevier Science Ltd.