Table of Content

25 February 2021, Volume 43 Issue 1

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Red tide level prediction based on RF feature selection and XGBoost model

2021, 43(1):  1-12.  DOI: 10.12012/j.cnki.fjsc.2021.01.001

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The occurrence of red tide is the result of various natural factors, involving physical, chemical, biological and other factors. Aiming at the difficulty in selecting impact factors and low accuracy in red tide prediction, this study proposed an extreme gradient boosting tree (XGBoost) red tide level prediction model based on random forest (RF) feature selection method. We used Sansha Bay as a research area, taking the annual red tide event data from 2005 to 2019 as the model input data, combining the importance of random forest algorithm features and Pearson correlation analysis to obtain the final ranking of features. Secondly, according to the AUC value of each feature of the RF algorithm, we obtained the optimal feature number of the model, and then selected the optimal feature set required by the XGBoost model based on the importance of the feature. Finally, we used the best feature set to train the XGBoost classification model. Experimental results showed that this method can achieve higher classification accuracy than other classification methods, which can provide a new solution for the prediction of red tide levels in Sansha Bay.

Study on the inhibition of eutrophic water sediment by new phoslock and coagulants

2021, 43(1):  13-20.  DOI: 10.14012/j.cnki.fisc.2021.01.002

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One of the primary reasons for frequent algal blooms are the release of phosphorus and the algae recovery in sediments. Therefore, the deposits of the eutrophic Shanzi Reservoir in Fujian Province were taken as the research object and laboratory simulation experiments were carried out to explore the inhibitory effect of new phosphorus-locking agent (NP) on the release of phosphorus in the sediments and the recovery of algae. The experimental results showed that the addition of NP increased the total phosphorus (TP) and the calcium-bound phosphorus (Ca-P) of the deposit by 10.8% and 15.9%, respectively. Adding twice as much NP improved phytoplankton germination inhibition in sediments by 79.6%，but the cost was higher and the ecological risk of heavy metal residues had increased, the theoretical amount (NP∶P=100∶1) of the NP’s inhibition rate only reached 34.0% during the experiment. The method of combining 60 mg/L Polyaluminum Chloride (PAC) or Diatomaceous earth (DIA) with the theoretical amount of NP also had a better effect and changed the structure of the phytoplankton community in water.. Therefore, the algae inhibition rate, the cost, and ecological risks should be comprehensively considered and choosing a suitable combination of NP and coagulants could have a better effect to treat eutrophic water.

Photo-degradation of dissolved organic matter from different sources

2021, 43(1):  21-27.  DOI: 10.14012/j.cnki.fisc.2021.01.003

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Photochemical degradation is typically treated as a removal mechanism of marine dissolved organic matter (DOM). However, DOM photodegradation kinetics in different aquatic environments have not been well documented. Natural solar radiation experiments of DOM collected from Jiulong estuary, Xiamen Bay and highly-polluted urban Yundang Lagoon were conducted based on the absorption and fluorescence spectroscopy. An excitation-emission matrix and parallel factor analysis revealed three humic-like (C1, C2 and C5) and three protein-like (C3, C4 and C6). The results showed that the chromophoric dissolved organic matter (CDOM) in water samples from urban lagoon and Xiamen Bay was photodegraded more easily than that from Jiulong estuary. The higher proportion of protein-like components in sewage reflects the influence of human activities on the DOM composition of sewage in urban lagoons. After 6 days of light culture, the C1~C5 components degraded by 40.1%~78.8%, while the active humus-like components and the tryptophan-like components were preferred to degradation. This study revealed the diverse dynamics and composition change of DOM during solar radiation experiments in different aquatic environments, implied that photodegradation was an effective remediation way for organic pollution in polluted water.

Preliminary analysis of tidal current characteristics in Yantian Port sea area of Sansha Bay

2021, 43(1):  28-41.  DOI: 10.14012/j.cnki.fisc.2021.01.004

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Using the quasi-harmonic method, this paper anchored at the five stations in Yantian Port sea area of Sansha Bay for 27 hours in December, 2015 for study of the tidal current characteristics. The harmonic coefficients of the O1, K1, M2, S2, M4 and MS4 tidal current constituents were calculated for their north and east components. The tidal current elliptic factors were also computed. Meanwhile, the tidal type was analyzed. It was demonstrated that, the tidal and current type in Sansha Bay was regular semidiurnal tide, while the ratio of shallow water tidal current constituent to total current was very low. The ellipticity in absoluted value of M2 tidal was less than 0.2. The tidal current mainly presented in N-S reciprocating movement. The magnitude of ebb was larger than that of flood. The maximum possible flow velocity was between 113 cm/s and 135 cm/s, greater at the deep station and smaller at the low station. The velocity decreased gradually from surface to bottom generally. The residual current was generally small, less than 8 cm/s usually and the minimum was about 2 cm/s in the observed area, performing fuzzy lay phenomenon and circulation structure.

Characteristic of phytoplankton community structure

2021, 43(1):  42-52.  DOI: 10.14012/j.cnki.fisc.2021.01.005

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Phytoplankton samples were collected from 24 stations in Sansha Bay, Fujian Province in April 2019.The species composition, dominant population, cell density and ecological index of phytoplankton were preliminarily studied. The results showed that 181 species belonging to 69 genera and 4 phyla were identified in Sansha Bay, including 161 species in 57 genera of Bacillariophyta, 16 species in 10 genera in Dinoflagellates, 1 genus and 3 species in Cyanophyta, 1 genus and 1 species in Chrysophyta. The dominant species were Paralia sulcata, Skeletonema costatum, Thalassionema nitzschioides, Coscinodiscus jonesianus and Nitzschia sp. The cell density of phytoplankton in the middle layer was higher than that in the bottom layer, and the density of phytoplankton varied greatly in the horizontal distribution. The density ranged from (9.2~38.9)×106 cells/m3, with an average of 22.67×106 cells/m3.The richness index of different stations was between 0.77~1.83, with an average of 1.24. The evenness index was between 0.35~0.74, with an average of 0.63. The diversity index was between 1.14~2.63, with an average of 2.13. And the overall evaluation was in the middle level.

Effects of vacuum packaging combined with brine treatment on the fresh quality of Japanese sea bass (Lateolabrax japonicas)

2021, 43(1):  53-60.  DOI: 10.14012/j.cnki.fisc.2021.01.006

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The effect of brine treatment with different salt concentrations (10% and 25%) on the quality changes of Japanese sea bass was comprehensively evaluated by sensory evaluation, total viable counts, total volatile basic nitrogen (TVB-N) and pH during the cold storage. Our results showed that the brine treatment with different salt concentrations all exerted the bacteriostatic effect, which can significantly inhibit the growth of bacteria and delay the ability of microorganisms to produce TVB-N. According to the Pearson correlation analysis, the sensory scores of Japanese sea bass had a significant correlation with TVC and TVB-N, but no significant correlation with pH. The comprehensive evaluation of the freshness period of Japanese sea bass needed to be conducted based on synthesized analysis of three indicators. And the comprehensive evaluation result showed that 10% and 25% saline treatment could extend the shelf-life of superior products to 4 d, 8 d, and qualified products to 8 d, 12 d, respectively.

Molecular identification and phylogenetic analysis of Myxobolus honghuensis found in pharynx of goldfish Carassius auratus

2021, 43(1):  61-66.  DOI: 10.14012/j.cnki.fisc.2021.01.007

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During the diseases monitoring of goldfish in Fuzhou area, a kind of myxospore was found in the pharynx of goldfish Carassius auratus. In order to identify the parasite, 18S rDNA and ITS-5.8S gene of the Myxosporean were amplified by PCR, while the sequences of the two genes were used to construct the phylogenetic tree for further analysis, respectively. The results showed that the morphology of the myxospore was similar to that of Myxobolus honghuensis, and the sequence identity of 18S rDNA gene was 98.08 % between them. Besides, the specific primers of ITS-5.8S gene for the identification of M. honghuensis were succeed in amplifing the target gene of the myxospore. Combined with the parasitic parts, morphology as well as phylogenetic analysis, the myxospore could be identified as M. honghuensis. The findings were the first report of an infection of M. honghuensis in the pharynx of goldfish besides C. auratus gibelio, and of great benefit to the understanding of the hosts and parasitic parts. In addition, this work provided references with the early diagnosis of diseases of the pharynx-parasitising myxobolus.

Study on the effect of estradiol benzoate on feminization of the New Gift Tilapia（Oreochromis niloticus）

2021, 43(1):  67-72.  DOI: 10.14012/j.cnki.fisc.2021.01.008

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In order to study the influence of exogenous hormones on the sex differentiation of tilapia, the New Gift Tilapia (Oreochromis niloticus) was induced by oral and soating estradiol benzoate as the exogenous estrogen. By setting different drug concentration gradients and induction durations, the effects of two methods of inducing feminization, both oral and soating, on the feminization of tilapia of the Gift Tilapia were studied. The results showed that during the induction of feminization with different drug concentrations, the female rate increased with the increase of concentration and the induction days, and there was a significant difference from the control group (P<0.05). The highest female rate in the 150 mg/ kg feed treatment group for 90 days was 94.45%, which was 49.34% higher than that of the control group (46.11%), and the lowest female rate was 65.00% in the 50 mg/kg group after 30 days of feeding. During the induction of feminization for 30 days by soating with different drug concentrations, the female rate increased with the increase of bath concentration, and they were significantly higher than the control group (P<0.05). The highest female rate was 77.78% in the group with 150 μg/L. The above results indicated that both oral and bathing female methods had good effects on inducing sex conversion of the Gift Tilapia, but considering the effectiveness and convenience, it was suggested that oral methods was easier to induce and obtain feminization fish.

Discussion on the pretreatment of residuals of malachite green, nitrofuran and chloramphenicol in aquatic products by quick inspect of immune colloidal gold technique

Jiang-Lei YE Gong-Shi LIN

2021, 43(1):  73-79.  DOI: 10.14012/j.cnki.fisc.2021.01.009

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It was banned by the state, that the residues of 6 kind of drugs, including malachite green, nitrofuran (furazolidone, furaltadone, nitrofurazone, nitrofurantoin), and chloramphenicol could not be detected in aquatic products. At present, the quick inspect of these residues was mainly based on immune colloidal gold technique. The accuracy of inspecting was reduced, as high fat samples, and the probability of "false negative" was arised. Commercialized quick inspect kits usually have certain pertinence. The basic inspecting unit usually select a certain type of kit that could cover the range to meet the daily inspect; however, in case of abnormal samples, the improvement of the pretreatment must be made by the kit supplier. This situation may be changed, on the basis of discussing the pretreatment process of these three kinds of residues in aquatic products in recent years. In this paper, we provided clues, including various interference factors and corresponding reagents. And tied to make it possible, that those basic level inspectors could be optimized or even designed the pretreatment by themselves, according to the method of the daily inspecting. There were many kinds of aquatic products, and the matrix of samples was quite different. Even if the authors had made improvements in some aspects for a certain type of kit, they could not completely cover all samples. It was important to enabled the readers could properly optimize the pre-treatment on the basis of the adopted method, when encountering abnormal samples. The optimized method verification and process recording should be made for future checking and item expansion.

A study on the effect of RMB exchange rate fluctuation on import price of aquatic products in China

2021, 43(1):  80-88.  DOI: 10.14012/j.cnki.fisc.2021.01.010

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In recent years, the quantity and intensity of China's aquatic products import have been increasing gradually, and the RMB exchange rate fluctuation has increasingly highlighted its restriction. The influence of RMB exchange rate pass-through on the price of domestic aquatic products will surely attract the attention of people in large countries of aquatic products. Therefore, this paper focused on the mechanism of the impact of exchange rate fluctuations on prices and studied the impact of RMB nominal exchange rate level and its volatility on the import price of aquatic products in China from theoretical and empirical perspectives. In this paper, the theoretical model analysis under the background of small open economy was constructed, and the results showed that: the appreciation of the RMB would encourage aquatic product imports; the risk of RMB exchange rate was negatively correlated with the price of aquatic products. That is to say, if other conditions remained unchanged, the lower the risk of exchange rate fluctuations was and the lower the exchange rate risk was, the higher the price of aquatic products importers were willing to bear. At the same time, for the convenience of research, this paper focused on the level of domestic nominal exchange rate that affected the import price index of aquatic products and its fluctuation risk. This paper adopted the monthly data of import prices of aquatic products from January 2005 to December 2019 to build an empirical model of aquatic product prices. Through empirical analysis, the combined net effect of the two variables of RMB nominal exchange rate and exchange rate fluctuation risk was -0.004 5, which meant that the pass-through effect of exchange rate on aquatic product import price was still incomplete. Although the RMB foreign exchange market had been improved, the risk bearing capacity and transference capacity of Chinese importers of exchange rate volatility were relatively weak, because the choice of hedging tools was relatively limited. Among the factors affecting import prices, the cumulative elastic ranking of the lagging performance coefficient of each factor could be seen (table 4): the nominal effective exchange rate of RMB had a great influence on the import price of aquatic products, accounting for 84.2%, ranking the first. The second risk of exchange rate volatility was 3.9%, which was basically the same as the domestic competition (3.4%). Domestic demand for imports came in fourth, followed by a smaller impact on exporters' costs, at 0.8%. In the economic sense, the more domestic consumers consume aquatic products, the more obvious the trend of import price decline. From the perspective of national market of aquatic products, compared with developed countries, the market structure of aquatic products in China was not perfect, and the results of theoretical analysis were consistent with the results of VAR and ECM empirical tests. In addition, the appreciation of RMB will stimulate the import of aquatic products, which will reduce the import price of aquatic products to some extent. Through the continuous improvement of China's exchange rate market, it can provide empirical support for China to implement a more flexible exchange rate system reform.

Research status and prevention and control measures on the impact of microplastics on marine environment and fishery production

2021, 43(1):  89-97.  DOI: 10.14012/j.cnki.fisc.2021.01.011

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Marine environment is an important material basis for the survival and development of marine fishery resources. It provids necessary living space and suitable environmental conditions for the growth and reproduction of marine organisms and plays a decisive role in aquaculture and other fishery production activities. Microplastics has become a new type of pollutants that threatens marine environment and fishery production due to their wide distribution, small particle size, difficulty in degradation and durability. This paper summarized the research progress of microplastics in marine environment, identified the main sources and expounded the main mechanism of influence of microplastics in marine environment and fishery production, and put forward the corresponding prevention and control measures, in order to provide scientific basis and technical guidance for the effective prevention and control of microplastics pollution in marine environment and fishery production.

Preliminary study on artificial breeding technique in a large scale of Meretix lyrata

2021, 43(1):  98-102.  DOI: 10.14012/j.cnki.fisc.2021.01.012

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In order to promote the healthy and sustainable development of culture industry and provide high quality spats of Meretix lyrata, artificial breeding technique in a large scale of M. lyrata was carried out. Unicellular algae were used as feeds during the breeding period. There were 6 batches of 580 kg parental M. lyrata which were artificially induced to spawn. The total number of fertilized eggs were 4.0336 billion, and 2.843 7 billion D-shaped larvae were hatched, so the hatching rate was 70.5%. After 7 days breeding of planktonic larvae, the larvae began to attach with the process of metamorphosis, and 1.515 7 billion attachment larvae were obtained, so the attachment rate was 53.3%. After another 33 days growth, 898.6 million spats with average shell length of 916.17 μm survived, the survival rate of artificial breeding was 31.6%, and the average output of spats per unit was 2.496 million seeds/m2.

Advances in the ultrastructure of sperm in Gastropoda

2021, 43(1):  103-110.  DOI: 10.14012/j.cnki.fisc.2021.01.013

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The sperm ultrastructure is widely recognized in the classification and phylogenesis of shellfish. The ultrastructure of spermatozoa can be used as a phylogenetic-taxonomic indicator. Furthermore, the comparative feature has been used as a clue for analyzing the relationship between different species and reproductive evolution. Gastropoda are important marine organisms and play an important role in marine ecosystems. However, Gastropoda spermatozoa exhibit different characters among species groups．In this paper, the basic data of artificial gastropods culture was reviewed.