Method for visually measuring umbrella diameter of medium and large jellyfish

Abstract

The invention relates to a method for visually measuring an umbrella diameter of medium and large jellyfish. The method comprises the following steps: (1) extending a cross rod out of a ship side and fixing a jellyfish collecting net at a top part of the cross rod; (2) putting the jellyfish collecting net into the sea, after visual measuring is started, enabling an investigation ship to run at a constant speed and standing at observation points for the visual measuring, where the visual measuring time of each station is fixed to be 5 min; (3) if the visual measuring time is not finished and a net bag is filled with jellyfish, alternately collecting and releasing two jellyfish collecting nets until the visual measuring time reaches 5 min or the number of the collected jellyfish meets a statistical requirement; and (4) carrying out umbrella diameter measurement and counting on large jellyfish on a deck one by one by using a measuring tool. The method can actually measure the umbrella diameter of the jellyfish obtained through visual measuring, realizes quantitative judgment of the number and size of the jellyfish at each visual measuring station, ensures integrity, scientificity and usability of jellyfish data information obtained through the visual measuring method, and is convenient for dynamic analysis and research of follow-up jellyfish population.

Description

technical field [0001] The invention relates to the technical field of monitoring marine biological resources, in particular to a method for visually measuring the umbrella diameter of medium and large jellyfish. Background technique [0002] In recent years, due to the deterioration of the marine environment and overfishing, jellyfish species at the lower end of the food chain (Nemopilema nomurai, Cyaneanozakii Kishinouye, etc.) have broken out, seriously affecting the marine ecosystem, food web structure and fishery production. Therefore, the development of large-scale jellyfish monitoring is of great significance for the early warning of jellyfish bloom and the study of bloom mechanism. [0003] In the past, the monitoring methods of large jellyfish mainly included net gear survey, acoustic survey and visual inspection. Various monitoring methods need to obtain jellyfish data information as much as possible, including the number of jellyfish and the size of jellyfish (um...

AI Technical Summary

Problems solved by technology

In the visual survey, the survey ship is used to set the visual survey time during the scheduled route navigation, and the number of jellyfish is counted visually within the specified time, but the size of the jellyfish, that is, the visual survey of the umbrella diameter is not ideal, because: 1) It is estimated by visual survey Compared with the actual measurement, there is an error; 2) It is due to the refraction of sea water, and the measurement of the visual perception of objects in the water will change after refraction; 3) The shape of the jellyfish is three-dimensional, and the visually measured shape is sometimes not suitable for estimating the diameter of the umbrella

Therefore, it is difficult to quantitatively judge the size of the obtained large jellyfish in the process of visual inspection, only the qualitative judgment of whether the umbrella diameter is large or small

According to visual inspection, the jellyfish data obtained in this way is not very complete, and the data of jellyfish size is lacking, which will affect the follow-up research and data comparison

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