Eriocheir sinensis juvenile crab density measuring method at Yangtze estuary

Abstract

The invention discloses an eriocheir sinensis juvenile crab density measuring method at Yangtze estuary. A push net type eriocheir sinensis juvenile crab gathering device is prepared for the eriocheir sinensis juvenile crab density measuring method at Yangtze estuary. The eriocheir sinensis juvenile crab density measuring method at Yangtze estuary is characterized in that the push net type eriocheir sinensis juvenile crab gathering device is composed of a push rod, a connecting rod, a gathering box, a fixing rod, a net bag, a cone-shaped net, a current meter, a dipsey, a float and a fishing wire. The push net type eriocheir sinensis juvenile crab gathering device utilizes that the pushing rod is fixed on the front portion of a nose of a juvenile crab sampling ship in a suspending manner, the juvenile crab sampling ship pushes the gathering device to go forward at a uniform velocity, and the current meter records flow velocity of water relative to a ship body, and records sampling time and the amount of the gathered juvenile crabs; the juvenile crab density is calculated through an equation of p= S / (T*V*1.2), wherein S stands for the amount of the gathered juvenile crabs, a unit is one; T is the sampling time, the unit is hour; V is the flow velocity of water relative to the ship body, the unit is meter per hour, 1.2 is the area of gathering box net opening, and the unit is square meter. The eriocheir sinensis juvenile crab density measuring method at Yangtze estuary can provide basis for protecting juvenile crab habitats and recovering ecology at Yangtze estuary.

Description

technical field [0001] The invention relates to a method for measuring the density of young crabs. Background technique [0002] Chinese mitten crab, also known as river crab and hairy crab, is one of the aquatic products that our people love very much. Eriocheir sinensis is widely distributed in my country, and three major populations of mitten crab have been formed, mainly in the Yangtze River, Oujiang River and Liaohe River. Among them, the Yangtze River population is superior to the other two populations in terms of traits and yield. The Yangtze River Estuary is the largest and best natural spawning ground for Chinese mitten crabs in my country. At the end of the last century, hairy crab farmers came to the Yangtze River Estuary to snap up crab seedlings one after another in May every year. Natural crab seedlings were sold for 80,000 yuan / catties, known as "Soft gold in water". Because of its excellent germplasm, the crab seedlings produced in the spawning ground of the...

AI Technical Summary

Problems solved by technology

During the flood season of Chinese mitten crab seedlings in the Yangtze River Estuary, accurate knowledge of the density and quantity of crab seedlings is of great significance for fishing and scientific research. In the evaluation stage, there is a lack of accurate evaluation values. Therefore, it is urgent to invent a quantitative determination method for the density of Chinese mitten crab seedlings in the Yangtze River Estuary, so as to accurately grasp the characteristic values ​​of the crab seedling density, so as to protect the habitat and ecological restoration of the crab seedlings in the Yangtze River Estuary. Provide theoretical basis and reference materials for ecological risk assessment

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