Storm damage risk assessment for offshore cage culture

This study establishes a practical methodology for storm damage risk assessment and zoning for offshore cage culture by superimposing the vulnerability theory onto hydrodynamic modeling. The peak significant wave height is statistically correlated to the normalized fatigue load criteria at specified loading cycles to classify the destruction duration and damage state during storm events. The yield damage of the flotation pipe under cyclical wave oscillations was identified as the major failure mechanism of the sea cage. The structural failure risk would significantly decrease to 4.5-m waves, which is much lower than the manufacturing standard due to cumulative damage in a relatively short operation time. The wave-circulation model was applied to hindcast 112 high-impact typhoon scenarios in the study area for the return period analysis of the storm wave field. The damage risk distribution of the cage culture was mapped across the landscape to increase storm strength according to the vulnerability classification. The effectiveness of island shielding was explicitly revealed, and the leeward side was overall less risky as the return period increased, with the safe area shrinking inshore. For extreme conditions over a 100-year return period, the shield performance of leeward bays varied significantly due to the shoreline profile differences. Some existing cage deployment locations are at-risk relative to the structural resistance capability, whereas other unrecognized areas might be suitable for cage culture. These findings imply the necessity of storm risk assessment before proactive prevention measures and deployment zoning. The methodology may also be adapted to storm risk predictions for other facilities in the coastal ocean.     

Correction to: Stocking density alters growth performance,serum biochemistry,digestive enzymes,immune response,and muscle quality of largemouth bass (Micropterus salmoides) in in-pond raceway system

Fish Physiology and Biochemistry -     

Precision biometrics data of Atlantic salmon (Salmo salar L.) in commercial grow-out sea-cages: Manual sampling and infrared diode frames compared to processing plant

One of the critical challenges that the global salmon farming industry will confront when upscaling production is accurate biomass control. Commercial salmon farming requires a significant level of certainty regarding fish count, average weight measurement, live weight distribution, and other production indicators. A reliable control system for assessing the biomass of farmed Atlantic salmon is essential for sustainable and cost-effective precision aquaculture. A study was done in four production sea-cages in a Chilean Atlantic salmon marine grow-out farm to estimate the average weight and frequency distribution utilizing the Vaki Biomassdaily® diode frames as an alternate technology to manual weight measurement. From post-smolt reception to fish harvest, diode frames were put in each sea-cage in a secure position for 15 months. There were no significant changes in length or average weight between manual sampling and frame estimate. The mean degree of accuracy for the average weight estimation was 98.83 % for the frames utilized in the four sea cages. The diode frames also achieved a high degree of precision in predicting the frequency distribution of fish. There were no statistically significant variations between the distribution variances of the diode frame measurements and the distribution variances of the fish received at the fish processing facility (FPF). The maximum difference between the average weight calculated by the frames and the average weight of the fish received in the processing facility was 2.4 %, with 99.66 % being the highest accuracy with only 19 g of difference. We determined that diode frames might replace manual weight assessments with greater reliability for growth monitoring and production management. To assure the optimal performance of the diode frames in terms of accuracy and precision for future commercial-scale validations in the salmon farming business, the development of a standard best practice manual is necessary.     

Antifungal Activity of Rhein and Aloe‐Emodin from Rheum palmatum on Fish Pathogenic Saprolegnia sp.

Saprolegnia infections cause severe economic losses among freshwater fish farming. In this study, two known compounds, rhein and aloe‐emodin, were isolated from Rheum palmatum, and the in vitro inhibitory activity of both compounds against mycelial growth and spore germination of Saprolegnia was tested. Both rhein and aloe‐emodin were able to decrease Saprolegnia mycelial growth and spore activity in all tested concentrations after exposure for 48 h. Complete inhibition of mycelial growth was observed at 20 mg/L for rhein and at 50 mg/L for aloe‐emodin, while spore germination was 100% prevented at 16 and 40 mg/L for rhein and aloe‐emodin, respectively. Because rhein showed stronger in vitro anti‐Saprolegnia activity, it was further tested in vivo to measure the prevention and treatment efficacy on Saprolegnia infection of grass carp. Its acute activity to grass carp was also evaluated. The results revealed that exposure to rhein at 20 mg/L for 7 d could prevent 93.3% of infections by Saprolegnia in abraded grass carp, while 67.7% of infected fish could be recovered by treatment with rhein. The 48‐h median lethal concentration (48 h‐LC₅₀) to grass carp was 148.5 mg/L, which is about 7.4 times the effective dose indicating the safety for the use of rhein. This study suggests that rhein has promising anti‐Saprolegnia activity and may be an option in preventing and controlling Saprolegnia infection.     

Development of fish spatio-temporal identifying technology using SegNet in aquaculture net cages

In marine aquaculture, fish populations constantly decrease throughout the cultivation period because of mortality and escape. Current production management systems provide limited opportunities to count the cultured fish, making it difficult to estimate accurately the fish population in the cage. To overcome this problem, an automatic fish identifying method based on particle tracking velocimetry (PTV) flow visualization technology is proposed in this paper. The proposed method utilizes an image processing unit that extracts individual fish from the acquired image and a motion analysis unit that calculates the motion vector for each individual. Thus, the accuracy of the extraction results in the image processing unit affects the system’s counting results. To validate the efficiency and robustness of the image extraction performed by the image processing unit, individuals were extracted from images using the open-source image deep learning semantic segmentation method (SegNet), which is able to distinguish between the background and foreground in the images via analysis at the pixel level. SegNet is able to improve the image discrimination performance by multiplying the learning paths, and the robustness of the detection results can be ensured by changing the layer structure according to the detection target. Accordingly, the use of SegNet was evaluated in terms of the number of layers and images in the training set. The results of this study indicate that the application of SegNet with PTV technology represents a promising method for the automatic identifying and behavioral tracking of fish in an aquaculture net cage.     

迟缓爱德华菌FliC-TolC融合蛋白表达及免疫特性研究

鞭毛蛋白FliC与外膜蛋白TolC均具有免疫保护效果,其中FliC蛋白具有疫苗佐剂的特性,但目前尚未有关迟缓爱德华菌(E.tarda)FliC-TolC融合产物免疫动物的免疫效果的相关报道。为研究E.tarda FliC-TolC融合蛋白的免疫特性,本研究利用融合PCR方法扩增获得fliC-tolC片段,构建重组载体pET-28a-fliC-tolC,并利用E.coli BL21表达系统表达了融合蛋白FliC-TolC。将纯化的FliC-TolC、TolC、FliC蛋白免疫小鼠后,以E.tarda强毒株攻毒评估免疫效果;并利用斑马鱼模型进行了平行试验。结果显示,本研究克隆了E.tarda fliC-tolC基因并表达和纯化了相应重组蛋白FliC-TolC;FliC-TolC蛋白激发小鼠产生的抗体水平优于FliC、TolC蛋白单独免疫组,表明FliC-TolC蛋白具有优良的免疫原性。攻毒试验表明FliC-TolC蛋白组小鼠对强毒株可产生较好的抵抗力,相对保护率为95%;斑马鱼攻毒试验相对保护率为60%。本研究证实了E.tarda重组蛋白FliC-TolC的免疫效力,为进一步研制E.tarda亚单位疫苗提供了参考和借鉴。     

免疫增强剂在虾类养殖上的应用现状和研究进展

从介绍虾类的免疫系统出发，阐述了虾类免疫增强剂的发展概况，对免疫增强剂在虾类养殖上的应用进行了总结和概括，并阐述了虾类免疫增强剂研究存在的问题和发展趋势。     

Self-grading of larval pike-perch (Sander lucioperca), triggered by positive phototaxis

The phototactic behavior of pike-perch (Sander lucioperca) larvae from 1 to 50 days post hatch (dph) was evaluated using a channel system with 0 and 700 lx light treatment. The findings of this work show larval pike-perch to be highly positive phototactic during its larval stage with a peak of positive phototactic behavior between 10 and 22 dph. After 22 dph positive phototaxis decreased and pike-perch increasingly preferred the lower light treatment. In a second experiment observed positive phototaxis was used to evaluate the effectiveness of a light triggered self-grading mechanism for pike-perch larvae at 16, 22, 28 and 34 dph. The use of larvae’s positive phototaxis for a gentle self-grading was successful at 16 and 22 dph and decreased the length variability between 14 and 18% at 16 dph and between 18 and 28% at 22 dph. Whereas the grading at 28 and 34 dph led to an insufficient reduction in length heterogeneity. As a result the light triggered self-grading has the potential to be implemented in future rearing protocols and to be applied on pike-perch between 16 to 22 dph. Furthermore, it is suggested to consider a light triggered self-grading mechanism within upcoming tank designs for the rearing of larval pike-perch.     

草鱼出血病细胞培养灭活疫苗生产工艺的比较

比较了方瓶静置培养、１０×２００ｍｌ转管培养和细胞生物反应器微载体培养３种方法增殖细胞和病毒的效率,以细胞生物反应器微载体培养法的效率最高,与静置培养法相比较,单位培养液细胞增殖量提高２０～２５倍,病毒增殖量ＴＣＩＤ５０测定增加１．６５对数值,ＬＤ５０测定增加１．４５对数值。经济效益比较,疫苗制备的培养液成本,以细胞生物反应器微载体培养法最低。已研究出以细胞生物反应器微载体培养法增殖细胞和病毒为基本生产工艺的工厂化生产草鱼出血病细胞疫苗工艺流程。