| The Cyprinus carpio,osteichthyes,cypriniformes,cyprinidae,the scales are golden,and the tail is red.In addition to containing several trace elements necessary for the human body,the muscle contains all essential amino acids and four kinds of flavor amino acids.The meat is also very tender.The cyprinus carpio is a kind of fish with high protein and low fat.It has been deeply loved by various inland banquets.In recent years,due to the changes of the Yellow River’s water supply and the changes in the ecological environment,how to effectively monitor and reasonably manage the fishery resources to ensure the sustainable development of the fishery economy has become an urgent problem to be solved.Fish resource assessment is the basis for the development of fish resources.Rational investigation and development of freshwater fishes are of great significance to the sustainability of resources.There are few studies on freshwater fishes in the country and they cannot meet the needs of research and investigation and development..The assessment of fishery resources used in our assessment of fishery resources is based on the advantages of rapid and high-efficiency,large-scale survey space,and non-contact damage to biological resources.It has been designated by the world’s fisheries developed countries as the main assessment of aquatic swimming resources in the world.The hydroacoustic assessment of fishery resources measures the amount of biological resources in the surveyed sea area based on the Nautical area scattering coefficient(NASC,m2/nmile2),and the target strength(d B)is the key factor of the conversion of the two.In order to improve the accuracy and credibility of the fishery resource water acoustics assessment,this paper is based on the Kirchhoff approximation model to measure the relationship between the target intensity and the fish body tilt and body length at different acoustic detection frequencies of the cyprinus carpio,obtained conclusions are as below:In this experiment,The target strength of the samples of cyprinus carpio in the xiaolangdi reservoir was measured and analysed,Then the X-ray photography was completed for the experimental samples.The X-ray images were processed with DICOM VIEWER to measure the morphological parameters of the samples according to the kirchhoff approximation model calculation,then the MATLAB software was used to calculate and analyse the data.As well as the science acoustics sounder(EY60,Simrad)was selected with three kinds of commonly used frequence of 38 KHz,70KHz and120 KHz,The cyprinus carpio body tilt angle is between-50° to 50° as research scope,the relations are obtained between tilt angle and length of fish and the target strength.Results shows that :The tilt angle variation pattern in both fish’s target strength at 38,70 and 120 k Hz showed the feature distribution of multiple peaks,and the higher frequency the target strength to tilt angle variations is more sensitive.The maximum target strength corresponding to the tilt angle increases with the number of peaks increasing.When the function of tilt angle is(-5°,15°),for cyprinus carpio,at 38 k Hz;the relationship between target strength and body length is LTS-(28)28.61lg95.15,and the formula is LTS-(28)28.64lg20 using b20 form at 70 k Hz;the relationship is LTS-(28)43.61lg23.16 and the formula is LTS-(28)42.64lg20 using b20 form at 120 k Hz;the relationship is LTS-(28)87.64lg73.19 and the formula is LTS-(28)24.64lg20.When the function of tilt angle is(0°,10°),for cyprinus carpio,at38 k Hz;the relationship between target strength and body length is LTS-(28)28.61lg69.16,and the formula is LTS-(28)76.63lg20 using b20 for form the relationship is LTS-(28)91.60lg3.16 and the formula is LTS-(28)01.64lg20 using b20 form at 120 k Hz;the relationship is LTS-(28)86.63lg21.19 and the formula is LTS-(28)74.63lg20.Based on the Kirchhoff Approximation model,the correlations of target intensity with tilt and body length at different frequencies of the cyprinus carpio have been obtained in order to provide a useful reference for model research on the target intensity of freshwater fishes in China,in order to improve fishery resources.The accuracy and credibility of hydroacoustic assessment provides a scientific basis. |
